Metabolic fingerprinting by nuclear magnetic resonance of hepatocellular carcinoma cells during p53 reactivation-induced senescence

Cellular senescence is characterized by stable cell cycle arrest. Senescent cells exhibit a senescence-associated secretory phenotype that can promote tumor progression. The aim of our study was to identify specific nuclear magnetic resonance (NMR) spectroscopy-based markers of cancer cell senescence. For metabolic studies, we employed murine liver carcinoma Harvey Rat Sarcoma Virus (H-Ras) cells, in which reactivation of p53 expression induces senescence. Senescent and nonsenescent cell extracts were subjected to high-resolution proton (1H)-NMR spectroscopy-based metabolomics, and dynamic metabolic changes during senescence were analyzed using a magnetic resonance spectroscopy (MRS)-compatible cell perfusion system. Additionally, the ability of intact senescent cells to degrade the extracellular matrix (ECM) was quantified in the cell perfusion system. Analysis of senescent H-Ras cell extracts revealed elevated sn-glycero-3-phosphocholine, myoinositol, taurine, and creatine levels, with decreases in glycine, o-phosphocholine, threonine, and valine. These metabolic findings were accompanied by a greater degradation index of the ECM in senescent H-Ras cells than in control H-Ras cells. MRS studies with the cell perfusion system revealed elevated creatine levels in senescent cells on Day 4, confirming the 1H-NMR results. These senescence-associated changes in metabolism and ECM degradation strongly impact growth and redox metabolism and reveal potential MRS signals for detecting senescent cancer cells in vivo.

Prostate fibroblasts and prostate cancer associated fibroblasts exhibit different metabolic, matrix degradation and PD-L1 expression responses to hypoxia

Fibroblasts are versatile cells that play a major role in wound healing by synthesizing and remodeling the extracellular matrix (ECM). In cancers, fibroblasts play an expanded role in tumor progression and dissemination, immunosuppression, and metabolic support of cancer cells. In prostate cancer (PCa), fibroblasts have been shown to induce growth and increase metastatic potential. To further understand differences in the functions of human PCa associated fibroblasts (PCAFs) compared to normal prostate fibroblasts (PFs), we investigated the metabolic profile and ECM degradation characteristics of PFs and PCAFs using a magnetic resonance imaging and spectroscopy compatible intact cell perfusion assay. To further understand how PFs and PCAFs respond to hypoxic tumor microenvironments that are often observed in PCa, we characterized the effects of hypoxia on PF and PCAF metabolism, invasion and PD-L1 expression. We found that under normoxia, PCAFs displayed decreased ECM degradation compared to PFs. Under hypoxia, ECM degradation by PFs increased, whereas PCAFs exhibited decreased ECM degradation. Under both normoxia and hypoxia, PCAFs and PFs showed significantly different metabolic profiles. PD-L1 expression was intrinsically higher in PCAFs compared to PFs. Under hypoxia, PD-L1 expression increased in PCAFs but not in PFs. Our data suggest that PCAFs may not directly induce ECM degradation to assist in tumor dissemination, but may instead create an immune suppressive tumor microenvironment that further increases under hypoxic conditions. Our data identify the intrinsic metabolic, ECM degradation and PD-L1 expression differences between PCAFs and PFs under normoxia and hypoxia that may provide novel targets in PCa treatment.

Reprogramming of VEGF-mediated extracellular matrix changes through autocrine signaling

Vascular endothelial growth factor (VEGF) plays key roles in angiogenesis, vasculogenesis, and wound healing. In cancers, including triple negative breast cancer (TNBC), VEGF has been associated with increased invasion and metastasis, processes that require cancer cells to traverse through the extracellular matrix (ECM) and establish angiogenesis at distant sites. To further understand the role of VEGF in modifying the ECM, we characterized VEGF-mediated changes in the ECM of tumors derived from TNBC MDA-MB-231 cells engineered to overexpress VEGF. We established that increased VEGF expression by these cells resulted in tumors with reduced collagen 1 (Col1) fibers, fibronectin, and hyaluronan. Molecular characterization of tumors identified an increase of MMP1, uPAR, and LOX, and a decrease of MMP2, and ADAMTS1. α-SMA, a marker of cancer associated fibroblasts (CAFs), increased, and FAP-α, a marker of a subset of CAFs associated with immune suppression, decreased with VEGF overexpression. Analysis of human data from The Cancer Genome Atlas Program confirmed mRNA differences for several molecules when comparing TNBC with high and low VEGF expression. We additionally characterized enzymatic changes induced by VEGF overexpression in three different cancer cell lines that clearly identified autocrine-mediated changes, specifically uPAR, in these enzymes. Unlike the increase of Col1 fibers and fibronectin mediated by VEGF during wound healing, in the TNBC model, VEGF significantly reduced key protein components of the ECM. These results further expand our understanding of the role of VEGF in cancer progression and identify potential ECM-related targets to disrupt this progression.

PET/MRI and Bioluminescent Imaging Identify Hypoxia as a Cause of Programmed Cell Death Ligand 1 Image Heterogeneity

Purpose To examine the association between hypoxia and programmed cell death ligand 1 (PD-L1) expression using bioluminescence imaging (BLI) and PET/MRI in a syngeneic mouse model of triple-negative breast cancer (TNBC). Materials and Methods PET/MRI and optical imaging were used to determine the role of hypoxia in altering PD-L1 expression using a syngeneic TNBC model engineered to express luciferase under hypoxia. Results Imaging showed a close spatial association between areas of hypoxia and increased PD-L1 expression in the syngeneic murine (4T1) tumor model. Mouse and human TNBC cells exposed to hypoxia exhibited a significant increase in PD-L1 expression, consistent with the in vivo imaging data. The role of hypoxia in increasing PD-L1 expression was further confirmed by using The Cancer Genome Atlas analyses of different human TNBCs. Conclusion These results have identified the potential role of hypoxia in contributing to PD-L1 heterogeneity in tumors by increasing cancer cell PD-L1 expression. Keywords: Hypoxia, PD-L1, Triple-Negative Breast Cancer, PET/MRI, Bioluminescence Imaging Supplemental material is available for this article. © RSNA, 2023.

Evaluating near-infrared photoimmunotherapy for targeting fibroblast activation protein-α expressing cells in vitro and in vivo

Photoimmunotherapy (PIT), carried out using an Ab conjugated to the near infrared dye IRDye700DX, is achieving significant success in target-specific elimination of cells. Fibroblast activation protein alpha (FAP-α) is an important target in cancer because of its expression by cancer-associated fibroblasts (CAFs) as well as by some cancer cells. Cancer-associated fibroblasts that express FAP-α have protumorigenic and immune suppressive functions. Using immunohistochemistry of human breast cancer tissue microarrays, we identified an increase of FAP-α⁺  CAFs in invasive breast cancer tissue compared to adjacent normal tissue. We found FAP-α expression increased in fibroblasts cocultured with cancer cells. In proof-of-principle studies, we engineered human FAP-α overexpressing MDA-MB-231 and HT-1080 cancer cells and murine FAP-α overexpressing NIH-3T3 fibroblasts to evaluate several anti-FAP-α Abs and selected AF3715 based on its high binding affinity with both human and mouse FAP-α. After conjugation of AF3715 with the phthalocyanine dye IR700, the resultant Ab conjugate, FAP-α-IR700, was evaluated in cells and tumors for its specificity and effectiveness in eliminating FAP-α expressing cell populations with PIT. Fibroblast activation protein-α-IR700-PIT resulted in effective FAP-α-specific cell killing in the engineered cancer cells and in two patient-derived CAFs in a dose-dependent manner. Following an intravenous injection, FAP-α-IR700 retention was three-fold higher than IgG-IR700 in FAP-α overexpressing tumors, and two-fold higher compared to WT tumors. Fibroblast activation protein-α-IR700-PIT resulted in significant growth inhibition of tumors derived from FAP-α overexpressing human cancer cells. A reduction of endogenous FAP-α⁺  murine CAFs was identified at 7 days after FAP-α-IR700-PIT. Fibroblast activation protein-α-targeted near infrared PIT presents a promising strategy to eliminate FAP-α⁺  CAFs.

Functional roles of FAP-α in metabolism, migration and invasion of human cancer cells

Fibroblast activation protein-α (FAP-α) is a transmembrane serine protease that is attracting significant interest as it is expressed by a subgroup of cancer-associated fibroblasts that play a role in immune suppression and cancer metastasis. FAP-α is also expressed by some cancer cells, such as melanoma, colorectal and breast cancer cells. Triple negative breast cancer (TNBC) is an aggressive cancer that urgently requires identification of novel targets for therapy. To expand our understanding of the functional roles of FAP-α in TNBC we engineered a human TNBC cell line, MDA-MB-231, to stably overexpress FAP-α and characterized changes in metabolism by ¹H magnetic resonance spectroscopy, cell proliferation, migration characterized by wound healing, and invasion. FAP-α overexpression resulted in significant alterations in myoinositol, choline metabolites, creatine, and taurine, as well as a significant increase of migration and invasion, although proliferation remained unaltered. The increase of migration and invasion are consistent with the known activities of FAP-α as an exopeptidase and endopeptidase/gelatinase/collagenase in tissue remodeling and repair, and in cell migration. We additionally determined the effects of FAP-α overexpression on the human fibrosarcoma HT1080 cell line that showed increased migration, accompanied by limited changes in metabolism that identified the dependency of the metabolic changes on cell type. These metabolic data identify a previously unknown role of FAP-α in modifying cancer cell metabolism in the TNBC cell line studied here that may provide new insights into its functional roles in cancer progression.

PSMA-specific degradable dextran for multiplexed immunotargeted siRNA therapeutics against prostate cancer

Small interfering RNA (siRNA) is ideal for gene silencing through a sequence-specific RNA interference process. The redundancy and complexity of molecular pathways in cancer create a need for multiplexed targeting that can be achieved with multiplexed siRNA delivery. Here, we delivered multiplexed siRNA with a PSMA-targeted biocompatible dextran nanocarrier to downregulate CD46 and PD-L1 in PSMA expressing prostate cancer cells. The selected gene targets, PD-L1 and CD46, play important roles in the escape of cancer cells from immune surveillance. PSMA, abundantly expressed by prostate cancer cells, allowed the prostate cancer-specific delivery of the nanocarrier. The nanocarrier was modified with acid cleavable acetal bonds for a rapid release of siRNA. Cell imaging and flow cytometry studies confirmed the PSMA-specific delivery of CD46 and PD-L1 siRNA to high PSMA expressing PC-3 PIP cells. Immunoblot, qRT-PCR and flow cytometry methods confirmed the downregulation of CD46 and PD-L1 following treatment with multiplexed siRNA.

Abstract 5070: Prostate-specific membrane antigen (PSMA) targeted multiplexed siRNA-mediated gene silencing of CD46 and PD-L1 in prostate cancer

Small interfering RNA are suitable for gene silencing through a sequence-specific RNA interference process. The redundancy and complexity of molecular pathways in cancer create a need for multiplexed targeting that can be achieved with multiplexed siRNA delivery. Here we delivered multiplexed siRNA with a PSMA-targeted biocompatible dextran nanoparticle (NP) to downregulate CD46 and PD-L1 siRNA in PSMA expressing prostate cancer cells. The multiplexed gene targets selected, PD-L1 and CD46, play important roles in the escape of cancer cells from immune surveillance. PSMA is abundantly expressed by prostate cancer cells allowing prostate cancer specific delivery of the NPs. The NP was decorated with acid cleavable amine functional groups through acetal bonds that undergo degradation under acidic conditions providing rapid release of siRNA. Cell imaging and flow cytometry studies confirmed PSMA-specific delivery of CD46 and PD-L1 siRNA to high PSMA expressing PC-3 PIP cells. Immunoblot, qRT-PCR and flow cytometry confirmed downregulation of CD46 and PD-L1 following treatment with multiplexed siRNA at a concentration of 50 nM. These studies pave the way for delivering multiplexed siRNA to tumors in vivo to unmask tumors to the immune system using PSMA targeted biocompatible NPs.

Citation Format: Zhihang Chen, Balaji Krishnamachary, Yelena Mironchik, Sangeeta R. Banerjee, Martin G. Pomper, Zaver M. Bhujwalla. Prostate-specific membrane antigen (PSMA) targeted multiplexed siRNA-mediated gene silencing of CD46 and PD-L1 in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5070.

Abstract 6353: Metabolic changes in the spleen and pancreas induced by PDAC xenografts with or without glutamine transporter downregulation

Introduction: Our ongoing studies are focused on characterizing metabolic changes induced in the organs of mice with cachexia-inducing Pa04C human pancreatic cancer xenografts. Because pancreatic cancer cells are glutamine dependent [1], we downregulated the glutamine transporter SLC1A5 in Pa04C cells to determine if metabolic changes induced in the spleen and pancreas by Pa04C tumors were normalized when SLC1A5 was downregulated in these tumors. Metabolic patterns were characterized using high-resolution quantitative 1H magnetic resonance spectroscopy (MRS) of spleen and pancreas tissue obtained from normal mice and mice with Pa04C tumors and mice with Pa04C tumors with SLC1A5 downregulated.

Method: Patient derived cachexia-inducing Pa04C pancreatic cancer cells were lentivirally transduced to express shRNA to stably downregulate SLC1A5. Mice were euthanized once tumors were ~500 mm3, the spleen and pancreas were excised and snap frozen. Snap frozen spleen (normal n= 5, Pa04C n= 11, Pa04C_SLC1A5 n= 10) and pancreas (normal n= 4, Pa04C n= 16, Pa04C_SLC1A5 n= 10) tissue samples were pulverized for dual phase extraction. The aqueous phase was used for 1H MRS analysis. Topspin 3.5 software was used for data processing and analyses.

Results and Discussion: Significant downregulation of SLC1A5 mRNA and protein was confirmed in Pa04C_SLC1A5 cells and tumors. SLC1A5 downregulation resulted in significant growth delay and attenuation of weight loss. A comparison of normal mice vs empty vector/wild type tumor (EV/WT) bearing mice identified significant changes in succinate, aspartate and fumarate in the spleen, lactate, acetate, pyruvate, methionine, asparagine, creatine, choline phosphocholine, uracil, histidine and phenylalanine in the pancreas, with leucine, isoleucine, valine, alanine, glutamate, glutamine, glutathione, glycerophosphocholine, glycine, glucose and tyrosine commonly altered in the spleen and pancreas. A comparison of normal vs Pa04C_ SLC1A5 tumor bearing mice identified similar metabolic changes in the spleen and pancreas but these were reduced. Fumarate did not change in the spleen, and of the metabolic changes common to spleen and pancreas, glutamine did not change when tumor SLC1A5 was downregulated. Metabolite changes induced only in the pancreas were also similar to normal vs EV/WT with the exception of a change in glutamine with SLC1A5 downregulation and no change in lactate. Our data highlight the profound metabolic changes in spleen and pancreas metabolism that occur with growth of a cachexia-inducing pancreatic cancer xenograft, and the impact on these metabolic patterns as a result of downregulating the glutamine transporter in these cancer cells. The metabolic patterns identified in the spleen and pancreas may provide novel targets to reduce the morbidity from cachexia.

Reference: 1. Son J et al, Nature. 2013;496(7443):101-5.

Citation Format: Raj Kumar Sharma, Santosh Kumar Bharti, Balaji Krishnamachary, Yelena Mironchik, Paul Winnard Jr., Marie-France Penet, Zaver M. Bhujwalla. Metabolic changes in the spleen and pancreas induced by PDAC xenografts with or without glutamine transporter downregulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6353.

VEGF Overexpression Significantly Increases Nanoparticle-Mediated siRNA Delivery and Target-Gene Downregulation

The availability of nanoparticles (NPs) to deliver small interfering RNA (siRNA) has significantly expanded the specificity and range of ‘druggable’ targets for precision medicine in cancer. This is especially important for cancers such as triple negative breast cancer (TNBC) for which there are no targeted treatments. Our purpose here was to understand the role of tumor vasculature and vascular endothelial growth factor (VEGF) overexpression in a TNBC xenograft in improving the delivery and function of siRNA NPs using in vivo as well as ex vivo imaging. We used triple negative MDA-MB-231 human breast cancer xenografts derived from cells engineered to overexpress VEGF to understand the role of VEGF and vascularization in NP delivery and function. We used polyethylene glycol (PEG) conjugated polyethylenimine (PEI) NPs to deliver siRNA that downregulates choline kinase alpha (Chkα), an enzyme that is associated with malignant transformation and tumor progression. Because Chkα converts choline to phosphocholine, effective delivery of Chkα siRNA NPs resulted in functional changes of a significant decrease in phosphocholine and total choline that was detected with ¹H magnetic resonance spectroscopy (MRS). We observed a significant increase in NP delivery and a significant decrease in Chkα and phosphocholine in VEGF overexpressing xenografts. Our results demonstrated the importance of tumor vascularization in achieving effective siRNA delivery and downregulation of the target gene Chkα and its function.

Abstract 2353: Metabolic reprogramming by SLC1A5 downregulation in pancreatic cancer cells

Introduction: Pancreatic cancers exhibit limited response to chemo- and radiation therapy. Identifying novel targets for pancreatic cancer treatment is important for new treatment strategies. Because pancreatic cancer cells are ‘glutamine avid' [1], targeting glutamine metabolic pathways can provide novel options for treatment. The glutamine transporter, SLC1A5, is being actively investigated as a pharmacological target in cancer [2]. Here we have engineered human pancreatic cells expressing shRNA to downregulate the glutamine transporter SLC1A5. We performed high-resolution 1H magnetic resonance spectroscopy (MRS) to understand the metabolic reprograming that occurs with SLC1A5 downregulation in these two cell lines.

Method: Panc1 and Pa04C pancreatic cancer cell lines were genetically engineered to express shRNA against SLC1A5 using lentiviral transduction. Downregulation of SLC1A5 was verified with qRTPCR and immunoblotting. Control cells expressing an empty vector (EV) were also engineered. Dual phase extraction was performed as previously described [3]. High-resolution 1H MRS was performed on the aqueous phase extracts and recorded on a 750 MHz spectrometer. All data acquisition, processing and quantification was performed with TOPSPIN 3.5 software. Spectra were obtained from Panc1EV (n=4), Pa04CEV (n=4), Panc1_SLC1A5_shRNA (n=4) and Pa04C_SLC1A5_shRNA (n=4) cells.

Results and Discussion: SLC1A5 downregulation significantly decreased the glutamine/glutamate ratio in Pa04C_SLC1A5_shRNA cells but not in Panc1_SLC1A5_shRNA cells. Instead, in Panc1_SLC1A5_shRNA cells, a significant decrease of the amino acids leucine, isoleucine, valine, tyrosine, histidine, and phenylalanine was observed. Lactate and fumarate also significantly decreased in Panc1_SLC1A5_shRNA cells. Other than the significant decrease of glutamine/glutamate in the Pa04C_SLC1A5_shRNA cells, no other significant metabolic differences were observed in these cells. Our data expand the understanding of the diverse metabolic reprogramming that occurs following SLC1A5 downregulation in two human pancreatic cancer cell lines that may lead to the development of additional metabolic targets.

Supported by NIH R01CA193365 and R35CA209960.1. Son J et al., Nature. 2013; 2. Bhutia YD et al., Biochim Biophys Acta. 2016; 3. Winnard PT Jr. et al., J Cachexia Sarcopenia Muscle. 2020.

Citation Format: Raj Kumar Sharma, Balalji Krishnamachary, Ishwarya Sivakumar, Yelena Mironchik, Santosh Kumar Bharti, Zaver M. Bhujwalla. Metabolic reprogramming by SLC1A5 downregulation in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2353.

Abstract 2354: Downregulating the glutamine transporter, SLC1A5, significantly reduces cachexia in a PDAC xenograft

Cachexia occurs with high frequency and severity in pancreatic ductal adenocarcinoma (PDAC) patients [1]. Cachectic patients experience a wide range of symptoms affecting the function of organs such as muscle, liver, brain, and heart, causing significant morbidity [2]. In high-resolution 1H magnetic resonance spectroscopy (MRS) studies of extracts, we previously observed significant perturbation of glutamine in the brain and plasma of mice with a cachexia-inducing PDAC xenograft [3] that prompted us to evaluate the effects of modifying tumor glutamine metabolism on cachexia. We investigated tumors derived from cachexia-inducing Pa04C cells engineered to express shRNA against the glutamine transporter, SLC1A5, glutaminase (GLS) 1, and GLS 2. Patient-derived cachexia-inducing Pa04C cells were stably transduced with virions that expressed shRNA against GLS1 or GLS2 or SLC1A5. Pooled clones were obtained with puromycin selection. Empty vector (EV) cells were also established. Downregulation of target genes was confirmed with mRNA and protein expression characterization. The effects of gene knockdown on tumor growth and weight-loss were determined following subcutaneous inoculation of engineered cells or wild type cells in SCID mice. Longitudinal tumor growth, weights and percent weight changes were determined in 7 wild type (WT), 7 EV, 9 GLS1 downregulated, 9 GLS2 downregulated, and 9 SLC1A5 downregulated tumor bearing mice. Once tumors were ~500 mm3 in volume, tumors were harvested from euthanized mice, and snap frozen for molecular analysis. Protein and mRNA obtained from tumors was validated for downregulation of target genes. Efficient downregulation of SLC1A5, GLS1 and GLS2 mRNA and protein was confirmed in tumors. Downregulating SLC1A5 significantly reduced tumor growth. But, downregulating GLS1 or GLS2 did not reduce tumor growth and, in fact, GLS1 downregulated tumors grew significantly faster than WT or EV tumors. Importantly, for comparable tumor volumes, we found that body weight loss was markedly reduced in mice with SLC1A5 downregulated tumors. Although GLS1 downregulated tumors grew faster than WT tumors, weight loss was attenuated at comparable tumor volumes in these tumors although not to the same extent as in SLC1A5 downregulated tumors. These data highlight potential role of SLC1A5 in PDAC tumor treatment and in the treatment of PDAC-induced cachexia, and support targeting the glutamine/glutamate axis in PDAC to reduce or reverse cachexia.Supported by NIH R35 CA209960 and R01 CA193365. 1. Fearon KC, Baracos VE. Cachexia in pancreatic cancer: new treatment options and measures of success. 2010; 2. Inui A. Cancer anorexia-cachexia syndrome: current issues in research and management. CA Cancer J Clin. 2002; 3. Winnard PT, Jr., et al., Brain metabolites in cholinergic and glutamatergic pathways are altered by pancreatic cancer cachexia. J Cachexia Sarcopenia Muscle. 2020.

Citation Format: Balaji Krishnamachary, Ishwarya Sivakumar, Yelena Mironchik, Raj Kumar Sharma, Santosh Kumar Bharti, Marie-France Penet, Paul Winnard, Flonne Wildes, Eibhlin Goggins, Anirban Maitra, Michael G. Goggins, Zaver M. Bhujwalla. Downregulating the glutamine transporter, SLC1A5, significantly reduces cachexia in a PDAC xenograft [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2354.

PD-L1 siRNA Theranostics With a Dextran Nanoparticle Highlights the Importance of Nanoparticle Delivery for Effective Tumor PD-L1 Downregulation

Purpose

The inhibition of immune checkpoints such as programmed cell death ligand-1 (PD-L1/CD274) with antibodies is providing novel opportunities to expose cancer cells to the immune system. Antibody based checkpoint blockade can, however, result in serious autoimmune complications because normal tissues also express immune checkpoints. As sequence-specific gene-silencing agents, the availability of siRNA has significantly expanded the specificity and range of “druggable” targets making them promising agents for precision medicine in cancer. Here, we have demonstrated the ability of a novel biodegradable dextran based theranostic nanoparticle (NP) to deliver siRNA downregulating PD-L1 in tumors. Optical imaging highlighted the importance of NP delivery and accumulation in tumors to achieve effective downregulation with siRNA NPs, and demonstrated low delivery and accumulation in several PD-L1 expressing normal tissues.

Methods

The dextran scaffold was functionalized with small molecules containing amine groups through acetal bonds. The NP was decorated with a Cy5.5 NIR probe allowing visualization of NP delivery, accumulation, and biodistribution. MDA-MB-231 triple negative human breast cancer cells were inoculated orthotopically or subcutaneously to achieve differences in vascular delivery in the tumors. Molecular characterization of PD-L1 mRNA and protein expression in cancer cells and tumors was performed with qRT-PCR and immunoblot analysis.

Results

The PD-L1 siRNA dextran NPs effectively downregulated PD-L1 in MDA-MB-231 cells. We identified a significant correlation between NP delivery and accumulation, and the extent of PD-L1 downregulation, with in vivo imaging. The size of the NP of ~ 20 nm allowed delivery through leaky tumor vasculature but not through the vasculature of high PD-L1 expressing normal tissue such as the spleen and lungs.

Conclusions

Here we have demonstrated, for the first time, the feasibility of downregulating PD-L1 in tumors using siRNA delivered with a biodegradable dextran polymer that was decorated with an imaging reporter. Our data demonstrate the importance of tumor NP delivery and accumulation in achieving effective downregulation, highlighting the importance of imaging in siRNA NP delivery. Effective delivery of these siRNA carrying NPs in the tumor but not in normal tissues may mitigate some of the side-effects of immune checkpoint inhibitors by sparing PD-L1 inhibition in these tissues.

The PD-L1 metabolic interactome intersects with choline metabolism and inflammation

Background

Harnessing the power of the immune system by using immune checkpoint inhibitors has resulted in some of the most exciting advances in cancer treatment. The full potential of this approach has, however, not been fully realized for treating many cancers such as pancreatic and breast cancer. Cancer metabolism influences many aspects of cancer progression including immune surveillance. An expanded understanding of how cancer metabolism can directly impact immune checkpoints may allow further optimization of immunotherapy. We therefore investigated, for the first time, the relationship between the overexpression of choline kinase-α (Chk-α), an enzyme observed in most cancers, and the expression of the immune checkpoint PD-L1.

Methods

We used small interfering RNA to downregulate Chk-α, PD-L1, or both in two triple-negative human breast cancer cell lines (MDA-MB-231 and SUM-149) and two human pancreatic ductal adenocarcinoma cell lines (Pa09C and Pa20C). The effects of the downregulation were studied at the genomic, proteomic, and metabolomic levels. The findings were compared with the results obtained by the analysis of public data from The Cancer Genome Atlas Program.

Results

We identified an inverse dependence between Chk-α and PD-L1 at the genomic, proteomic, and metabolomic levels. We also found that prostaglandin-endoperoxide synthase 2 (COX-2) and transforming growth factor beta (TGF-β) play an important role in this relationship. We independently confirmed this relationship in human cancers by analyzing data from The Cancer Genome Atlas Program.

Conclusions

Our data identified previously unknown roles of PD-L1 in cancer cell metabolic reprogramming, and revealed the immunosuppressive increased PD-L1 effect of Chk-α downregulation. These data suggest that PD-L1 regulation of metabolism may be mediated through Chk-α, COX-2, and TGF-β. The observations provide new insights that can be applied to the rational design of combinatorial therapies targeting immune checkpoints and cancer metabolism.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40170-021-00245-w.

HIF and COX-2 expression in triple negative breast cancer cells with hypoxia and 5-fluorouracil

Our purpose was to understand the effects of normoxia or hypoxia on 5-fluorouracil (5-FU) treatment in triple negative breast cancer (TNBC) cells, and characterize the molecular changes in hypoxia inducible factors (HIFs) and cyclooxygenase-2 (COX-2) following treatment. Cell viability and protein levels of HIFs and COX-2 were determined after wild type and HIF silenced MDA-MB-231 cells, and wild type SUM-149 cells, were treated with 5-FU under normoxia or hypoxia. 5-FU reduced cell viability to the same levels irrespective of normoxia or hypoxia. HIF silenced MDA-MB-231 cells showed comparable changes in cell viability, supporting observations that hypoxia and the HIF pathways did not significantly influence cell viability reduction by 5-FU. Our data suggest that HIF-2α accumulation may predispose cancer cells to cell death under hypoxia. SUM-149 cells that have higher COX-2 and HIF-2α following 24 h of hypoxia, were more sensitive to 96 h of hypoxia compared to MDA-MB-231 cells, and were more sensitive to 5-FU than MDA-MB-231 cells. COX-2 levels changed with hypoxia and with 5-FU treatment but patterns were different between the two cell lines. At 96 h, COX-2 increased in both untreated and 5-FU treated cells under hypoxia in MDA-MB-231 cells. In SUM-149 cells, only treatment with 5-FU increased COX-2 at 96 h of hypoxia. Cells that survive hypoxia and 5-FU treatment may exhibit a more aggressive phenotype. Our results support understanding interactions between HIF and COX-2 with chemotherapeutic agents under normoxia and hypoxia, and investigating the use of COX-2 inhibitors in these settings.

Brain metabolites in cholinergic and glutamatergic pathways are altered by pancreatic cancer cachexia

BACKGROUND

Cachexia is a major cause of morbidity in pancreatic ductal adenocarcinoma (PDAC) patients. Our purpose was to understand the impact of PDAC-induced cachexia on brain metabolism in PDAC xenograft studies, to gain new insights into the causes of cachexia-induced morbidity. Changes in mouse and human plasma metabolites were characterized to identify underlying causes of brain metabolic changes.

METHODS

We quantified metabolites, detected with high-resolution ¹ H magnetic resonance spectroscopy, in the brain and plasma of normal mice (n = 10) and mice bearing cachexia (n = 10) or non-cachexia (n = 9) inducing PDAC xenografts as well as in human plasma obtained from normal individuals (n = 24) and from individuals with benign pancreatic disease (n = 20) and PDAC (n = 20). Statistical significance was defined as a P value ≤0.05.

RESULTS

The brain metabolic signature of cachexia-inducing PDAC was characterized by a significant depletion of choline of -27% and -21% as well as increases of glutamine of 13% and 9% and formate of 21% and 14%, relative to normal controls and non-cachectic tumour-bearing mice, respectively. Good to moderate correlations with percent weight change were found for choline (r = 0.70), glutamine (r = -0.58), and formate (r = -0.43). Significant choline depletion of -38% and -30%, relative to normal controls and non-cachectic tumour-bearing mice, respectively, detected in the plasma of cachectic mice likely contributed to decreased brain choline in cachectic mice. Similarly, relative to normal controls and patients with benign disease, choline levels in human plasma samples of PDAC patients were significantly lower by -12% and -20% respectively. A comparison of plasma metabolites from PDAC patients with and without weight loss identified significant changes in glutamine metabolism.

CONCLUSIONS

Disturbances in metabolites of the choline/cholinergic and glutamine/glutamate/glutamatergic neurotransmitter pathways may contribute to morbidity. Metabolic normalization may provide strategies to reduce morbidity. The human plasma metabolite changes observed may lead to the development of companion diagnostic markers to detect PDAC and PDAC-induced cachexia.

Hypoxia theranostics of a human prostate cancer xenograft and the resulting effects on the tumor microenvironment

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Developed a hypoxia theranostic imaging strategy to eliminate hypoxic cells.

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Hypoxic cell elimination resulted in fewer cancer associated fibroblasts (CAFs)

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Collagen 1 fiber patterns were altered with hypoxic cell elimination.

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cDNA nanoparticles with HRE driven prodrug enzyme expression can target hypoxia.

Hypoxia is frequently observed in human prostate cancer, and is associated with chemoresistance, radioresistance, metastasis, and castrate-resistance. Our purpose in these studies was to perform hypoxia theranostics by combining in vivo hypoxia imaging and hypoxic cancer cell targeting in a human prostate cancer xenograft. This was achieved by engineering PC3 human prostate cancer cells to express luciferase as well as a prodrug enzyme, yeast cytosine deaminase, under control of hypoxic response elements (HREs). Cancer cells display an adaptive response to hypoxia through the activation of several genes mediated by the binding of hypoxia inducible factors (HIFs) to HRE in the promoter region of target gene that results in their increased transcription. HIFs promote key steps in tumorigenesis, including angiogenesis, metabolism, proliferation, metastasis, and differentiation. HRE-driven luciferase expression allowed us to detect hypoxia in vivo to time the administration of the nontoxic prodrug 5-fluorocytosine that was converted by yeast cytosine deaminase, expressed under HRE regulation, to the chemotherapy agent 5-fluorouracil to target hypoxic cells. Conversion of 5-fluorocytosine to 5-fluorouracil was detected in vivo by ¹⁹F magnetic resonance spectroscopy. Morphological and immunohistochemical staining and molecular analyses were performed to characterize tumor microenvironment changes in cancer-associated fibroblasts, cell viability, collagen 1 fiber patterns, and HIF-1α. These studies expand our understanding of the effects of eliminating hypoxic cancer cells on the tumor microenvironment and in reducing stromal cell populations such as cancer-associated fibroblasts.

Abstract 4920: FAP-α overexpression increases cancer cell migration

Fibroblast activation protein-α (FAP-α) is attracting increasing interest because of its role in immune suppression and cancer metastasis. To understand the role of FAP-α in cancer cells we engineered triple negative human breast cancer MDA-MB-231 cells and fibrosarcoma HT1080 cells to stably overexpress FAP-α and compared cell migration of parental and FAP-α overexpressing cells using wound healing analysis. We observed a significant increase of migration with FAP-α overexpression in MDA-MB-231 cells. HT1080 cells displayed similar trends on migration with FAP-α overexpression.

We developed MDA-MB-231 and HT-1080 cells overexpressing FAP-α (231-FAP and HT-1080-FAP) by transducing these cells with lentivirus encoding the gene for human FAP (Accession No. NM_004460.3) that was subcloned into lentiviral vector pMA3211. Immunoblot analysis with FAP-α antibody confirmed the overexpression of FAP-α protein. To evaluate migration, wound healing analysis was performed. Cells were seeded and incubated in DMEM without FBS for 24h before wounds were made by scratching cells with a p200 pipet. Pictures were taken immediately (0h), and at 6h, 24h, and 48h after wound formation. The wound areas were measured using ImageJ and normalized to the area (100%) at 0h. We used a cell counting kit-8 (CCK-8) to determine if cell proliferation was altered by FAP-α overexpression.

231-FAP cells exhibited significantly increased migration from 6h (66%) to 48h (0.6%) after wound formation compared to parental cells (73% at 6h and 7.6% at 48h). HT1080-FAP cells showed increased migration only at 24h (8%) and 48h (1.9%) after wound formation compared to parental cells (19% at 24h and 5.3% at 48h) although this was not statistically significant. The CCK-8 assay showed that there were no differences in cell proliferation between MDA-MB-231 cells and 231-FAP cells with or without 10% FBS. Both cell lines showed a comparably small reduction of proliferation (approximately 30%) at 48h point in FBS free medium. In contrast, both HT1080 and HT1080-FAP cell proliferation was reduced significantly (approximately 75%) at 48h point in FBS free medium. HT1080-FAP cell proliferation was slightly higher than parental cells in medium with FBS (16%) and without FBS (19%) at 48h point than parental cells.

Our data are consistent with the known activities of FAP-α as an exopeptidase and endopeptidase/gelatinase/collagenase in tissue remodeling and repair, and in cell migration. We found that FAP-α significantly increased MDA-MB-231 breast cancer cell migration but had very little effect on cell proliferation. FAP-α overexpression in HT1080 fibrosarcoma cells also increased migration but not as much as in MDA-MB-231 cells. Ongoing work with xenografts derived from these cell lines will provide further insights into tumor microenvironment changes with FAP-α overexpression.

Citation Format: Noriko Mori, Jiefu Jin, Balaji Krishnamachary, Yelena Mironchik, James D. Barnett, Zaver M. Bhujwalla. FAP-α overexpression increases cancer cell migration [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4920.

Abstract 3360: Phototheranostics of cancer associated fibroblasts by targeting fibroblast activation protein-α

Introduction: Stromal cells such as cancer associated fibroblasts (CAFs) mediate many of the aggressive characteristics of cancer1 and have an ever-replenishing supply that is largely left intact by our current therapeutic strategies.2 Fibroblast activation protein-α (FAP-α) is a target antigen that been reported to be selectively expressed in tumors by a subset of immunosuppressive stromal fibroblasts. Here, we extended our previous near-infrared photoimmunotherapy (NIR-PIT) study,3 to develop a FAP-α-targeted monoclonal antibody (mAb) photosensitizer conjugate. We developed FAP-α overexpressing MDA-MB-231 and HT-1080 cells to test the feasibility of targeting FAP-α expressing populations in cells and tumors in vivo, in terms of the specificity of the conjugate to bind to, detect, and eliminate FAP-α expressing populations.

Method: FAP-α monoclonal antibody (AF3715) and its IgG isotype control were conjugated with a NIR phthalocyanine dye, IR700, to form FAP-α-IR700 and IgG-IR700. FAP-α overexpression was achieved by transducing MDA-MB-231 and HT-1080 cells with lentivirus encoding the gene for human FAP (Accession No. NM_004460.3) that was subcloned into lentiviral vector pMA3211 to obtain 231-FAP and HT-1080-FAP cells. Cell viability was measured by using CCK-8 assay. Bilateral tumor models were established by inoculating 1×106 MDA-MB-231 cells or 1×106 231-FAP cells in 0.05 ml of Hank's balanced salt solution on either side in the mammary fat pads of athymic Balb/c (nu/nu) female mice. A similar number of HT-1080 or HT-1080-FAP cells were inoculated bilaterally in the flank. 50 μg of FAP-α-IR700 or IgG-IR700 was injected i.v., and fluorescence images of IR700 in mice were obtained over a 24-h period (n = 3 per group). At 24 h post injection, mice were euthanized, and tumors were isolated for imaging. For PIT, tumor-bearing mice (n = 4 per group) received two i.v. injections of 100 μg of FAP-α-IR700 at a one-week interval, and tumors were exposed to NIR irradiation at 200 J/cm2 at 24h p.i. Tumor diameters were measured over 2 weeks. IgG-IR700 and PBS-injected mice were used as controls.

Results and Discussion: We confirmed FAP-α overexpression in 231-FAP and HT-1080-FAP cells. FAP-α-IR700 was activated by NIR light, causing FAP-α-specific cell death. FAP-α-IR700-mediated phototoxicity was dependent on the conjugate concentration and NIR light dose; and it was inhibited by excess AF3715. We observed the preferential accumulation of FAP-α-IR700 in FAP-α-overexpressing 231-FAP and HT-1080-FAP tumors compared to their wild-type counterparts. The mean fluorescence intensity of FAP-α-IR700 in FAP-α-overexpressing tumors was approximately two to threefold higher than the wild type tumors. FAP-α-IR700 injection together with NIR light exposure resulted in the highest tumor growth delay in 231-FAP tumors and HT-1080-FAP tumors. Our results evaluate and confirm the ability of FAP-α-IR700 to target and eliminate FAP-α-overexpressing cell populations, providing novel opportunities to selectively deplete FAP-α high CAFs in cancers.

References: 1. Horimoto, Y. et al. Cell Adh Migr. 2012; 2. Eyden, B. et al. J Cell Mol Med. 2008; 3. Jin, J. et al. Sci.Rep. 2016. Supported by NIH R35 CA209960, P41 EB024495, and Emerson Collective Cancer Research Fund.

Citation Format: Jiefu Jin, James D. Barnett, Balaji Krishnamachary, Yelena Mironchik, Hisataka Kobayashi, Zaver Bhujwalla. Phototheranostics of cancer associated fibroblasts by targeting fibroblast activation protein-α [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3360.

Abstract 5258: 1 H MRS analysis of pancreas metabolites altered by cachexia

Cachexia is a multifactorial syndrome characterized by skeletal muscle weight loss and reduced physical activity. The extreme weight loss due to cachexia results in a particularly poor quality of life causing profound weakness, listlessness, and inability to function [1, 2]. Severe weight loss decreases the tolerance to treatments and anticancer therapies, and leads to the reduced survival of patients. In pancreatic cancer, the syndrome affects nearly 80% of patients [3]. Cancers can stimulate cachexia through the dysfunction of multiple organs [4]. Metabolic abnormalities may interfere with the regular functioning of these organs to increase the severity of the disease. Here we determined metabolic changes in the pancreas with cachexia-inducing and non-cachexia inducing tumor growth using high-resolution quantitative 1H magnetic resonance spectroscopy (MRS) of pancreas tissue obtained from normal, non-cachectic (Panc1) and cachectic (Pa04C) mice bearing pancreatic ductal adenocarcinoma (PDAC) xenografts.

Cancer cells were inoculated in the right flank of six to eight week old male severe combined immunodeficient mice. The pancreas was removed from mice following euthanization once tumors were ~300 mm3, snap frozen and stored at -80°C prior to dual phase extraction. 1H MRS was performed on the water phase. All 1H MR spectra with water suppression were acquired on a 750 MHz MR spectrometer using a single pulse sequence. All data processing analyses and quantification were performed with TOPSPIN 3.5 software. All statistical analysis were performed with MetaboAnalyst software [5].

Multivariate analyses performed to analyze the differences in the metabolic profiles among the groups (Control n = 9, Pa04C = 10 and Panc1 = 8) revealed differences in the overall metabolic pattern in the pancreas from normal, cachectic and non-cachectic groups. A significant decrease of leucine, isoleucine, valine, BCAA, glutamate, choline, pyruvate, glycine, niacinamide, fumarate and increase of alanine, pyruvate, and NAD was detected in cachectic mouse pancreas compared to control pancreas. A significant increase in alanine, phenylalanine, pyruvate, phosphocholine and decrease in glycine, NAD, niacinamide was observed in cachectic mouse pancreas compared to non-cachectic mouse pancreas. Pathway impact analysis using MetaboAnalyst web software indicated alterations in branch chain amino acid pathways and glutamate, glutamine metabolism. These results provide new insights into changes in pancreas metabolism with cachexia, and support investigating metabolic targets and biomarkers to reduce cachexia-associated morbidity.

Supported by NIH R01CA193365 and R35CA209960.

Ref: 1. Fearon K et al, The Lancet Oncology. 2011; 2. Penet MF, Bhujwalla ZM. Cancer journal. 2015; 3. Winnard PT, Jr. et al, Cancer research. 2016; 4. Argiles JM et al, Nature reviews Cancer. 2014; 5. Xia J, Wishart DS. Nature protocols. 2011.

Citation Format: Raj Kumar Sharma, Santosh K. Bharti, Paul T. Winnard Jr, Yelena Mironchik, Marie-France Penet, Zaver M. Bhujwalla. 1 H MRS analysis of pancreas metabolites altered by cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5258.

Abstract 1135: Dextran based nanoparticles for immunotheranostics of prostate cancer

Introduction:

Targeted nanoparticles (NPs) containing imaging reporters provide exciting options for cancer-specific delivery of siRNA to downregulate specific pathways in theranostic strategies. We recently developed a biodegradable modified dextran NP to deliver effectively siRNA and downregulate the target in vivo (1). Here we have developed a prostate specific membrane antigen (PSMA)-targeted dextran NP to deliver siRNA to downregulate PD-L1 in PSMA expressing prostate cancer (PCa) cells for immunotheranostics. In proof-of-principle studies, the NP was decorated with an optical imaging reporter to allow noninvasive detection in vivo, and evaluated in PC3 human PCa cells genetically engineered to overexpress PSMA (PC3-PIP) and in non-PSMA expressing PC3-Flu cells. Since castration-resistant PCa cells express PSMA, the ability to down regulate PD-L1 specifically may prevent these cancer cells from evading immune surveillance, resulting in their destruction by the immune system.

Methods:

For mRNA and protein analysis, PSMA overexpressing PC3-PIP cells and low PSMA expressing PC3-Flu cells were treated with dextran NPs with PD-L1 siRNA or PBS. 6h later, IFNγ (10 ng/mL) or PBS was added to the medium. Cells were collected, and proteins and mRNA extracted, 24h after NP/PBS treatment. Total RNA was isolated, and cDNA prepared following standard protocols, with q-RT-PCR performed for PD-L1 expression. Western blots were probed with anti-PD-L1, and anti-PSMA antibodies. For in vivo studies, PC3-PIP and PC3-Flu tumors were inoculated bilaterally in the flanks of male SCID mice. Once tumors reached ~200 mm3, dextran NPs siRNA with PSMA binding peptide were injected intravenously. Dosage and frequency of IFNγ injection in vivo was established, and bio distribution studies performed. Tumor samples were harvested and processed for mRNA and protein to detect PD-L1 expression.

Results and Conclusion:

Specificity of the PSMA-targeted dextran NP delivery was confirmed by PSMA-dependent retention of the NPs following fluorescent imaging of PC3-PIP and Flu cells. We next assessed the ability of the dextran NPs carrying PD-L1 siRNA to down regulate PD-L1 expression in PC3-PIP and PC3-Flu cells. Studies were performed with or without pre-activation of the cells with IFNγ. q-RT-PCR and western blots analysis confirmed a clear decrease of PD-L1 after NP treatment in PC3-PIP and PC3-Flu cells. Effective NP delivery was confirmed in tumors with optical imaging, both in vivo and ex vivo in excised organs. Ongoing studies are characterizing PD-L1 downregulation in tumors in vivo following treatment with PSMA-targeted dextran NPs delivering PD-L1 siRNA.

References: 1. Chen et al., Theranostics, 2018.

Acknowledgements: Supported by NIH P41EB024495 and R35CA209960.

Citation Format: Balaji Krishnamachary, Marie-France Penet, Zhihang Chen, Jesus Pacheco-Torres, Sangeeta Ray, Yelena Mironchik, Marty G. Pomper, Zaver M. Bhujwalla. Dextran based nanoparticles for immunotheranostics of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1135.

Abstract 5265: Spleen metabolism altered by human pancreatic cancer xenografts

Cancer-induced cachexia accounts for approximately 20% of all cancer deaths [1] and affects nearly 80% of pancreatic cancer patients [2, 3]. Cachectic patients experience a wide range of symptoms affecting several organ functions such as muscle, liver, brain, and heart that decrease quality of life and worsen prognosis. A major characteristic of cachexia is the accelerated skeletal muscle and fat storage wasting causing nutrient mobilization both directly as lipid and amino acids, and indirectly as glucose derived from the exploitation of liver gluconeogenesis that reaches the tumor through the bloodstream [4]. Here, for the first time, we have performed high-resolution quantitative 1H magnetic resonance spectroscopy (MRS) of spleen tissue obtained from normal mice and mice bearing PDAC that are cachectic (Pa04C) and non-cachectic (Panc1).

The Panc1 (non-cachectic), and Pa04C (cachectic) PDAC cell lines were used [5]. Eight-week-old male severe combined immunodeficient mice were inoculated in the right flank with cancer cells (5×106). Mice were euthanized once tumors were ~ 300 mm3. Control, cachectic and non-cachectic groups consisted of 9, 10 and 9 mice per group respectively. Spleen water soluble metabolites were extracted, freeze dried, reconstituted in D2O PBS and transferred to an NMR tube for spectral acquisition with a 750 MHz (17.6T) MR spectrometer [6].

As anticipated, mice with cachexia-inducing Pa04C tumors showed significant weight loss with time. We observed, for the first time, that spleens from cachectic Pa04C tumor bearing mice showed a profound weight loss compared to normal mice and mice with Panc1 tumors. However, an increase of liver and spleen size has been previously reported in terminal cachectic human patients from colorectal cancer measured by CT scan 2-11 months prior to death [7]. A significant decrease in almost all amino acids was observed in cachectic (Pa04C) mouse spleens compared to normal and non-cachectic (Panc1) mouse spleens. Differences in choline metabolites, creatine, glutamine, glutamate, glutathione and aspartate were observed in cachectic mouse spleens compared to non-cachectic mouse spleens and spleens from healthy control mice. The significant decrease of amino acids in the cachectic spleens may reflect increased utilization of amino acids by the tumor or other organs during the cachexia muscle/protein wasting [4]. These results provide new insights into changes in spleen metabolism during cachexia, and support investigating metabolic targets to reduce cachexia associated morbidity.

Supported by NIH R01CA193365 and R35CA209960.

Reference: 1. Argiles et al. Nat. Rev. Cancer 2014, 14 (11), 754; 2. Fearon et al. HPB (Oxford) 2010, 12 (5), 323; 3. Ozola et al. Pancreatology 2015, 15 (1), 19; 4. Porporato et al. Oncogenesis 2016, 5, e200; 5. Winnard et al. Can. Res. 2016, 76(6): 1441; 6. Penet et al. Clin. Can. Res. 2015, 21 (2), 386; 7. Lieffers et al. Am J Clin Nutr. 2009, 89 (4), 1173

Citation Format: Santosh Kumar Bharti, Paul T. Winnard, Raj Kumar Sharma, Yelena Mironchik, Marie-France Penet, Zaver M. Bhujwalla. Spleen metabolism altered by human pancreatic cancer xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5265.

Abstract 5260: Different cell metabolism by FAP-α overexpression in triple negative breast cancer cells

Fibroblast activation protein-α (FAP-α) is a cell surface serine protease that is attracting increasing interest because of its role in immune suppression and cancer metastasis. To understand the role of FAP-α in cancer cell metabolism we engineered triple negative MDA-MB-231 cells to stably overexpress FAP-α and compared metabolic profiles of parental and FAP-α overexpressing cells using 1H MR spectroscopy. We observed a significant increase of aspartate, glycerophosphocholine, lactate, myoinositol and phosphatidylcholine with FAP-α overexpression. These results identify a previously unknown role of FAP-α in modifying cancer cell metabolism that may provide new insights in its functional roles in cancer progression.

MDA-231luc (parent cells), derived from MDA-MB-231, were purchased from Sibtech Inc. MDA-231luc-FAPα (231-FAPα) cells were engineered using the gene for human FAP that was subcloned into lentiviral vector pMA3211. Immunoblot analysis with FAP-α antibody confirmed the overexpression of FAP-α protein in 231-FAPα cells. Approximately 3.5x107 cells were used for dual-phase cell extraction as previously described [1]. 1H MR spectra were recorded on a Bruker Biospin Avance-III 750 MHz NMR spectrometer and analyzed using TOPSPIN 3.5 software. Integrals of the metabolites of interest were determined and normalized to the number of cells and internal standard. Metabolite levels were quantified as arbitrary units (A.U.) from three experimental samples from each cell line. Statistical significance was evaluated using the unpaired one tailed Student t test.

We identified 18 metabolites from the aqueous phase (8 amino acids, 3 choline metabolites and 7 others) and 10 signals from the lipid phase (7 Fatty acids (FA), Cholesterol, Phosphatidylethanolamine (PtdE), -N(CH3)3: Phosphatidylcholine (PtdCho) & Sphingomyelin (SM)) using 1H MR spectra. We found that 4 metabolites (aspartate, glycerophosphocholine (GPC), lactate and myo-inositol) from the aqueous phase and 2 signals (FA: -CH2-CH2-CH=, and -N(CH3)3) from the lipid phase were significantly higher in 231-FAPα cells. It is likely that PtdCho level was significantly higher in 231-FAPα cells since the majority of -N(CH3)3 signals are from PtdCho. All the FA signals tended to be higher in 231-FAPα cells compared to parental cells. Since the average cell numbers at the time of cell collection were similar, cell density differences did not contribute to differences in metabolite levels. We are currently investigating the molecular mechanisms underlying these differences. The significant differences in water-soluble and lipid-soluble extracts provide new insights into the metabolic modulatory role of FAP-α.

[1] Krishnamachary B, et al. Cancer Res. 2009;15;69(8):3464-71

This work was supported by NIH R35CA209960.

Citation Format: Noriko Mori, Balaji Krishnamachary, Jiefu Jin, James Barnett, Yelena Mironchik, Zaver M. Bhujwalla. Different cell metabolism by FAP-α overexpression in triple negative breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5260.

Human Cancer Cell Membrane-Coated Biomimetic Nanoparticles Reduce Fibroblast-Mediated Invasion and Metastasis and Induce T-Cells

Biomimetic nanoparticles (NPs) combine the flexibility and reproducibility of synthetic materials with the functionality of biological materials. Here, we developed and characterized biomimetic poly(lactic- co-glycolic acid) (PLGA) NPs coated with human cancer cell membrane fractions (CCMFs) to form CCMF-coated PLGA (CCMF-PLGA) NPs. We evaluated the ability of these CCMF-PLGA NPs to disrupt cancer cell-stromal cell interactions and to induce an immune response. Western blot analysis verified the plasma membrane purity of CCMFs. Confocal fluorescence microscopy and flow cytometry confirmed the presence of intact membrane-associated proteins including CXCR4 and CD44 following membrane derivation and coating. CCMFs and CCMF-PLGA NPs were capable of inhibiting cancer cell migration toward human mammary fibroblasts. Intravenous injection of CCMF-PLGA NPs significantly reduced experimental metastasis in vivo. Following immunization of Balb/c mice, near-infrared fluorescence imaging confirmed the migration of NPs to proximal draining lymph nodes (LNs). A higher percentage of CD8⁺ and CD4⁺ cytotoxic T-lymphocyte populations was observed in spleens and LNs of CCMF-PLGA NP-immunized mice. Splenocytes isolated from CCMF-PLGA NP-immunized mice had the highest number of interferon gamma-producing T-cells as detected by the ELISpot assay. CCMF-PLGA NPs hold promise for disrupting cancer cell-stromal cell interactions and for priming the immune system in cancer immunotherapy.

Ascites Volumes and the Ovarian Cancer Microenvironment

Epithelial ovarian cancer is the leading cause of death from gynecologic malignancy among women in developed countries. Epithelial ovarian cancer has a poor prognosis, due to the aggressive characteristics of the disease combined with the lack of effective therapies. Options for late-stage ovarian cancer are limited and invasive, especially once malignant ascites develops. Malignant ascites, a complication observed in terminal ovarian cancer, significantly contributes to poor quality of life and to mortality. Excess accumulation of fluid in the peritoneal cavity occurs due to a combination of impaired fluid drainage and increased net filtration, mostly due to increasing intraperitoneal vascular permeability. Here we applied non-invasive magnetic resonance imaging (MRI) and spectroscopic imaging (MRSI) of syngeneic mouse tumors in vivo, and high-resolution ¹H MRS of mouse tumor extracts, to characterize the relationship between ascites volumes and the vasculature and metabolism of an experimental model of ovarian cancer. Differences were observed in the tumor vasculature and metabolism in tumors based on ascites volumes that provide new insights into the development of this condition.

Abstract 3483: 1H MRS characterization of the cachetic brain metabolome induced by human pancreatic pancer xenografts

The uncontrollable extreme weight loss due to cachexia results in a particularly poor quality of life causing profound weakness, listlessness, and an inability to function. A major characteristic of cachexia is accelerated skeletal muscle and fat storage wasting causing nutrient mobilization both directly as lipid and amino acids, and indirectly as ketone bodies and glucose derived from liver keto- and gluconeogenesis with systemic distribution including to the tumor through the bloodstream. Previously, we have reported the initial characterization of a myoblast optical imaging reporter that allowed real-time longitudinal monitoring of the early onset of cancer induced wasting and measured plasma metabolic changes associated with pancreatic ductal adenocarcinoma (PDAC)-induced cachexia. Here, for the first time, we have performed high-resolution quantitative 1H MR spectroscopy (MRS) of brain tissue to characterize the brain metabolome of normal mice and mice with human PDAC xenografts that induce cachexia (Pa04C cells) or are noncachectic (Panc1 cells).

Male severe combined immunodeficient mice were inoculated in the right flank with cancer cells (2×106) and in the right hind leg muscle with reporter myoblasts (2×106). Once the mice were sacrificed, brains were harvested, freeze clamped and stored in -80°C until 1H MRS analysis. Dual phase solvent extraction was performed on brain tissues and MR spectra were acquired on 750 MHz (17.6T) spectrometer.

As anticipated, mice with cachexia-inducing Pa04C tumors showed significant weight loss with time. For the first time, we found that brains from Pa04C tumor bearing mice exhibited a profound reduction in water soluble metabolites as compared to Panc1 and nontumor bearing normal mice. Significant decreases in neurotransmitters: γ-aminobutyric acid (GABA), N-acetyl aspartate (NAA), and taurine as well as lactate, myo-inositol, phosphocholine, glycerophosphocholine, creatine, formate, and essential amino acids: Leu, ILe, Val, and Phe were observed in brains from cachectic mice compared to noncachectic and healthy mice. Non-cachexia inducing Panc1 tumors also induced a significant decrease of brain GABA, glutamate, aspartate, total choline and tyrosine compared to normal brains. These results provide new insights into profound changes in brain metabolism during cachexia that are likely indicative of compromised CNS function and may be a major contributing factor to the systemic control of cachectic wasting. These data provide strong evidence to support investigating new metabolic interventions to reverse CNS injury and cachexia. and provide new CNS targets for early detection using in vivo MRS techniques.

Acknowledgement: This work was supported by NIH R01CA193365, R35CA209960, and P30CA06973.

Citation Format: Santosh Kumar Bharti, Paul T. Winnard, Yelena Mironchik, Marie-France Penet, Anirban Maitra, Zaver M. Bhujwalla. 1H MRS characterization of the cachetic brain metabolome induced by human pancreatic pancer xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3483.

Abstract 3480: COX-2 alters the metabolic secretome in triple negative human breast cancer xenografts

Cyclooxygenase-2 (COX-2) is an active mediator of the inflammatory response of cells and plays an important role in the development, progression, invasion, and metastasis of cancers including breast cancer [1]. Tumor interstitial fluid (TIF), the milieu that contains the tumor secretome, is one of the least examined aspects of the TME because of the difficulty in sampling this fluid from tumors. Here, for the first time, we have sampled TIF from COX-2 overexpressing triple negative SUM-149 human breast cancer xenografts and empty vector SUM-149 xenografts.

The cloning, construction of a lentivirus vector expressing COX-2 gene, and the establishment of SUM-149 cells stably overexpressing COX-2 (SUM-COX-2) were reported by us previously[2]. A home-built TIF collection chamber was inserted subcutaneously in female SCID mice with 4-6 1-2 mm tumor pieces packed around the chamber. Once tumors were ~ 400 mm3, TIF was collected from chambers. Each chamber yielded ~50μL of TIF that was analyzed with high-resolution 1H magnetic resonance spectroscopy (MRS) at 750 MHz.

SUM-COX-2 tumors showed consistently higher COX-2 expression compared to SUM-EV tumors. COX-2 overexpression resulted in a significant increase of lactate, glutamate, acetate, and succinate, and a significant decrease of glucose, glutamine, citrate, formate, and lipids; pyruvate tended to decrease. The changes in lactate and lipids are consistent with our earlier observations where COX-2 downregulation in triple negative MDMB-231 human breast cancer cells resulted in a significant decrease of lactate and an increase of lipids and lipid droplets in intact perfused cells[3]. Here, COX-2 overexpression increased glycolysis. Depletion of pyruvate observed here in COX-2 overexpressing cells would limit production of acetyl-CoA and consequently citrate to diminish fatty acid synthesis/lipids. Increased succinate parallels the increase in glutamate/α-ketoglutarate, the upstream intermediate to succinate in the tricarboxylic acid cycle [1], and indicates increased utilization/depletion of glutamine to supplement the TCA cycle. Importantly, accumulation of succinate inhibits HIF-1α prolyl hydroxylase that stabilizes HIF-1α driven cancer promoting metabolic pathways such as enhanced glycolysis and increased ROS[4]. Moreover, increased succinate also through the succinate/succinate dehydrogenase reaction, provides necessary electrons to the electron transport chain upstream of the COX-2 reaction[5]. These data provide new insights into the role of COX-2 in the metabolic secretome and tumor metabolism, and identify metabolic pathways as potential targets for reducing the effects of COX-2 expression in cancer.

Ref.

1. Wang et. al. Nat. Rev. Can. 2010

2. Krishnamachary et al. Oncot. 2017

3. Shah et al. NMR Biomed. 2012

4. Selak et al. Can Cell. 2005

5. Mills et al. Trd in Cell Bio. 2014

Citation Format: Santosh Kumar Bharti, Paul T. Winnard, Yelena Mironchik, Louis Dore-Savard, Balaji Krishnamachary, Zaver M. Bhujwalla. COX-2 alters the metabolic secretome in triple negative human breast cancer xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3480.

Abstract 3482: Cachexia has profound metabolic consequences in the heart and skeletal muscle

Cachexia is an underexplored and yet devastating consequence of cancer that is the cause of 20% of all cancer related deaths [1]. Cachexia is associated with poor treatment outcome [3], fatigue, and extremely poor quality of life [2, 3]. Tissue wasting is one of the characteristics associated with cachexia syndrome. Here we have used 1H MRS to characterize the metabolic profile of skeletal muscle and heart muscle obtained from normal mice and noncachexia (Panc1) and cachexia inducing (Pa04C) human pancreatic cancer xenograft bearing mice to further understand this syndrome.

Male severe combined immunodeficient (SCID) mice were inoculated in the right flank with cancer cells (2 × 106) and in the right hind leg muscle with cachexia reporter myoblasts (2×106) [4]. Mice were sacrificed once tumors were ~400 mm3, and the heart and skeletal muscle were harvested for dual phase solvent extraction. 1H magnetic resonance (MR) spectra of the water phase were acquired with a 750 MHz MR spectrometer.

Quantitative changes in metabolite levels were obtained from 1H MR spectra. Leucine, creatine, lactate and glucose were significantly lower, and acetate and formate were significantly higher, in the muscle of cachectic mice compared to non-cachetic mice. Cachectic mice had significantly lower alanine, succinate, glycine, lipid and PUFA (poly unsaturated fatty acids), and significantly higher acetate, pyruvate, and formate compared to normal mice. Non-cachectic mice had significantly lower alanine, succinate, phosphocreatine, and glycine, and significantly higher leucine, isoleucine, valine, pyruvate, creatine, taurine and glucose compared to normal mice.

In the heart, leucine, isoleucine, valine, aspartate, glucose, lipid and PUFA were significantly lower, and glutamine was significantly higher, in cachectic mice compared to non-cachetic mice. Cachectic mice had significantly lower leucine, isoleucine, valine, lactate, alanine, glutamate, and PUFA, and significantly higher glutamine and glucose compared to normal mice. Non-cachectic mice had significantly lower alanine, and significantly higher glucose and lipid compared to normal mice.

These data highlight, for the first time, the profound metabolic changes that occur in skeletal muscle and the heart with cachexia, identifying potential in vivo 1H MRS indices to detect the onset of cachexia from changes in branched chain amino acids, glucose, and PUFAs. Our data also provide new insights into the effects of cachexia as well as noncachexia inducing tumors on skeletal muscle and heart metabolism that may lead to metabolic interventions in ‘metabolotheranostic' strategies to reduce the morbidity associated with cancer and cachexia.

Supported by NIH R01CA193365, R35CA209960, and P30CA06973.

Ref.

1. Argiles et al: Nat. Rev. Can 2014, 14(11):754

2. Fearon et al: HPB (Oxford) 2010, 12(5):323

3. Ozola et al: Pancreatology 2015, 15(1):19

4. Winnard et al: Can Res. 2016, 76(6):1441

Citation Format: Santosh Kumar Bharti, Paul Winnard, Yelena Mironchik, Marie-France Penet, Zaver M. Bhujwalla. Cachexia has profound metabolic consequences in the heart and skeletal muscle [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3482.

Abstract 1680: The immune checkpoint metabolome and its relationship with choline metabolism

Introduction: Immune checkpoint inhibition has emerged as an exciting treatment option for several cancers. New insights into the role of immune checkpoints in cellular metabolism can be used to optimize their effectiveness in treatment. Programmed cell death-1 ligand (PD-L1) is an immune checkpoint overexpressed in cancers that has been successfully exploited for immune therapy. Here we investigated the relationship between the aberrant choline metabolism observed in most cancers and PD-L1 expression in triple-negative human MDA-MB-231 breast cancer cells, and characterized the metabolic effects of PD-L1 downregulation.

Methods: Experiments were performed with MDA-MB-231 cells transiently transfected with small interfering RNA (siRNA) against either luciferase (control siRNA), choline kinase-α (Chk-α), or PD-L1, following standard protocols. Total RNA was isolated, complementary cDNA synthesized, and quantitative real-time PCR performed using IQ SYBR Green supermix and gene-specific primers. Cell extracts were obtained using a dual-phase extraction method and analyzed by high resolution 1H magnetic resonance spectroscopy. 3 to 6 independent experiments were performed for each group.

Results: Silencing of Chk-α resulted in a significant increase of PD-L1 mRNA expression and silencing of PD-L1 resulted in a significant increase of Chk-α mRNA expression. These increases were not observed when both PD-L1 and Chk-α were silenced. Transfection with control siRNA did not alter Chk-α mRNA, but induced a small increase of PD-L1 mRNA compared to untreated cells. Transfection of cells with Chk-α and PD-L1 siRNA resulted in a significant decreases of Chk-α and PD-L1 mRNA. Consistent with the mRNA results, a significant increase of phosphocholine (PC) was observed in spectra obtained from cells transfected with PD-L1 siRNA compared to cells transfected with control siRNA, confirming that Chk-α increased in these cells. A significant increase of glutamate, glutathione, alanine and lactate was also observed in cells transfected with PD-L1 siRNA. As expected, cells transfected with a combination of Chk-α and PD-L1 siRNA showed a significant decrease of PC due to downregulation of Chk-α.

Discussion: Our data have identified, for the first time, the inverse association between PD-L1 and Chk-α expression following downregulation. These data suggest that treatments that decrease Chk-α and PC could result in cancer cells escaping immune surveillance through increased expression of PD-L1. On the other hand, these cells may become more susceptible to checkpoint inhibitors such as anti-PD-L1 or anti-PD-1 antibodies. PD-L1 downregulation also significantly increased glutathione that acts as a major antioxidant. Our ongoing studies are characterizing the effects of anti-PD-L1 antibody treatment on Chk-α expression.

Supported by NIH R35CA209960 and R01CA82337, and the Martin Escudero Foundation and Emerson Foundation.

Citation Format: Jesus Pacheco-Torres, Marie-France Penet, Yelena Mironchik, Sridhar Nimmagadda, Balaji Krishnamachary, Zaver M. Bhujwalla. The immune checkpoint metabolome and its relationship with choline metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1680.

Metabolic consequences of HIF silencing in a triple negative human breast cancer xenograft

Hypoxia is frequently encountered in tumors and results in the stabilization of hypoxia inducible factors (HIFs). These factors transcriptionally activate genes that allow cells to adapt to hypoxia. In cancers, hypoxia and HIFs have been associated with increased invasion, metastasis, and resistance to chemo and radiation therapy. Here we have characterized the metabolic consequences of silencing HIF-1α and HIF-2α singly or combined in MDA-MB-231 triple negative human breast cancer xenografts, using non-invasive proton magnetic resonance spectroscopic imaging (¹H MRSI) of in vivo tumors, and high-resolution ¹H MRS of tumor extracts. Tumors from all three sublines showed a significant reduction of growth rate. We identified new metabolic targets of HIF, and demonstrated the divergent consequences of silencing HIF-1α and HIF-2α individually on some of these targets. These data expand our understanding of the metabolic pathways regulated by HIFs that may provide new insights into the adaptive metabolic response of cancer cells to hypoxia. Such insights may lead to novel metabolism based therapeutic targets for triple negative breast cancer.

Hypoxia Inducible Factors Modify Collagen I Fibers in MDA-MB-231 Triple Negative Breast Cancer Xenografts

Hypoxia inducible factors (HIFs) are transcription factors that mediate the response of cells to hypoxia. HIFs have wide-ranging effects on metabolism, the tumor microenvironment (TME) and the extracellular matrix (ECM). Here we investigated the silencing effects of two of the three known isoforms, HIF-1α and HIF-2α, on collagen 1 (Col1) fibers, which form a major component of the ECM of tumors. Using a loss-of-function approach for HIF-1α or 2α or both HIF-1α and 2α, we identified a relationship between HIFs and Col1 fibers in MDA-MB-231 tumors. Tumors derived from MDA-MB-231 cells with HIF-1α or 2α or both HIF-1α and 2α silenced contained higher percent fiber volume and lower inter-fiber distance compared to tumors derived from empty vector MDA-MB-231 cells. Depending upon the type of silencing, we observed changes in Col1 degrading enzymes, and enzymes involved in Col1 synthesis and deposition. Additionally, a reduction in lysyl oxidase protein expression in HIF-down-regulated tumors suggests that more non-cross-linked fibers were present. Collectively these results identify the role of HIFs in modifying the ECM and the TME and provide new insights into the effects of hypoxia on the tumor ECM.

Breast cancer cell cyclooxygenase-2 expression alters extracellular matrix structure and function and numbers of cancer associated fibroblasts

Cyclooxygenase-2 (COX-2) is a critically important mediator of inflammation that significantly influences tumor angiogenesis, invasion, and metastasis. We investigated the role of COX-2 expressed by triple negative breast cancer cells in altering the structure and function of the extracellular matrix (ECM). COX-2 downregulation effects on ECM structure and function were investigated using magnetic resonance imaging (MRI) and second harmonic generation (SHG) microscopy of tumors derived from triple negative MDA-MB-231 breast cancer cells, and a derived clone stably expressing a short hairpin (shRNA) molecule downregulating COX-2. MRI of albumin-GdDTPA was used to characterize macromolecular fluid transport in vivo and SHG microscopy was used to quantify collagen 1 (Col1) fiber morphology. COX-2 downregulation decreased Col1 fiber density and altered macromolecular fluid transport. Immunohistochemistry identified significantly fewer activated cancer associated fibroblasts (CAFs) in low COX-2 expressing tumors. Metastatic lung nodules established by COX-2 downregulated cells were infrequent, smaller, and contained fewer Col1 fibers.COX-2 overexpression studies were performed with tumors derived from triple negative SUM-149 breast cancer cells lentivirally transduced to overexpress COX-2. SHG microscopy identified significantly higher Col1 fiber density in COX-2 overexpressing tumors with an increase of CAFs. These data expand upon the roles of COX-2 in shaping the structure and function of the ECM in primary and metastatic tumors, and identify the potential role of COX-2 in modifying the number of CAFs in tumors that may have contributed to the altered ECM.

Abstract 2495: The metabolic secretome of cachexia inducing pancreatic ductal adenocarcinoma

Cachexia is an underexplored and yet devastating consequence of cancer that is the cause of 20% of all cancer related deaths1. Cachexia inducing tumors cause a ‘wasting away’ of the body. The condition is associated with poor treatment outcome2, fatigue, and extremely poor quality of life2,3. Because of the multi-factorial characteristics of this condition, it has been difficult to understand the mechanisms driving the impact of the tumor on body organs and the sequence of events that leads to this lethal condition. Here we have used 1H MRS to characterize the metabolic profile of tumor interstitial fluid (TIF) obtained from noncachexia (Panc1) and cachexia inducing (Pa04C) tumors to further understand the impact of the deranged metabolism of cachexia-inducing tumors on the tumor metabolic secretome.

The human pancreatic cancer cell line, Panc1, was obtained from ATCC. The human pancreatic cancer cell line, Pa04C, was provided by Dr. Maitra4. Six to 8 week old male SCID mice were inoculated in both the right and left flank with cancer cells (5×106, Panc1 N=2, Pa04C N=2). We created a collection chamber to collect TIF. The chamber was implanted together with small tumor pieces harvested from the subcutaneous flank tumors, into the subcutaneous flank space of SCID mice (Panc1 N=8 and Pa04C N=6) until the tumor encompassed the chamber (4-5 weeks). The tumor was then removed and the tumor tissue and TIF were collected. To obtain control TIF, an empty chamber was implanted in the subcutaneous flank space of healthy mice. Dual phase solvent extraction was performed on tumor tissue. The water phase was separated, freeze dried, reconstituted in D2O PBS for spectral acquisition. All 1H MR spectra were acquired on an Avance III 750 MHz (17.6T) Bruker NMR spectrometer equipped with a 5 mm broad band inverse (BBI) probe. Spectral acquisition, processing and quantification were performed using TOPSPIN 2.1 software.

Notable differences between Pa04C compared to Panc1 TIF or normal interstitial fluid were a significant decrease of polyunsaturated fatty acids (PUFA) and lipids, and formate, pyruvate, glutamine, and glucose. Lactate, glutamate, succinate, glycine and acetone significantly increased in Pa04C TIF compared to Panc1 TIF or normal interstitial fluid. These differences in TIF cannot be explained solely by the differences in the tumor metabolic profile. Our data provide new insights into changes in the metabolic secretome with induction of cachexia that may shed new light on the cachexia cascade, and identify metabolic strategies to reverse the syndrome.

References:

(1) Argiles, J. M., et al. Nature reviews. Cancer 2014, 14, 754-762.

(2) Ozola Zalite, I., et al. Pancreatology 2015, 15, 19-24.

(3) Fearon, K. C., et al. HPB (Oxford) 2010, 12, 323-324.

(4) Penet, M. F., et al. Clinical Cancer Research 2015, 21, 386-395.

Acknowledgment: This work was supported by NIH R01 CA193365, NIH P50CA013175 and NIH P30CA06973.

Citation Format: Santosh K. Bharti, Paul T. Winnard, Louis Dore-Savard, Yelena Mironchik, Marie-France Penet, Zaver M. Bhujwalla. The metabolic secretome of cachexia inducing pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2495. doi:10.1158/1538-7445.AM2017-2495

Abstract 2510: Interrogating liver metabolic stress due to cancer-induced cachexia

Cancer-induced cachexia accounts for approximately 20% of all cancer deaths 1. In pancreatic cancer, the syndrome affects nearly 80% of patients 2,3. Cachectic patients experience a wide range of symptoms affecting the function of several organs such as muscle, liver, brain, and heart, that decrease quality of life and worsen prognosis. A major characteristic of cachexia is the accelerated skeletal muscle and fat storage wasting causing nutrient mobilization both directly as lipid and amino acids, and indirectly as glucose derived from the exploitation of liver gluconeogenesis that reaches the tumor through the bloodstream4. Patients with cachexia develop a wide range of metabolic stress from increased proteins and fat tissue burning resulting in increased energy expenditure. Here, for the first time, we have performed high-resolution quantitative 1H magnetic resonance spectroscopy (MRS) of liver tissue obtained from normal, noncachectic and cachectic mice bearing PDAC that are cachectic (Pa04C) and noncachectic (Panc1). A significant reduction in liver weight and significant changes in 1H MRS derived metabolite profiles were detected with cachexia.

Human pancreatic cancer cell lines, Panc1 and Pa04C, were used for the study. Six to 8 week old male severe combined immunodeficient mice were inoculated in the right flank with cancer cells (5×106) and in the right hind leg muscle with reporter myoblasts (2×106) to monitor the development of cachexia in mice5. Live animal optical imaging was done using a Xenogen IVIS® Spectrum (PerkinElmer) optical scanner. Dual phase solvent extraction was performed on liver tissue to extract water soluble metabolites. All 1H MR spectra were acquired on an Avance 750 MHz Bruker NMR spectrometer.

We found, for the first time, that the liver in Pa04C tumor bearing mice underwent a profound weight loss; although Panc1 tumor bearing mice showed some liver weight loss this was not as profound as observed with Pa04C tumors. Significant decreases in lactate, glucose and glutathione were observed in cachectic mouse liver compared to noncachectic mouse liver, and the liver from healthy control mice. The significant decrease of these metabolites in cachectic livers may reflect increased utilization of glucose, lactate and glutathione by the tumor or other organs during the cachexia cascade4. These results provide new insights into changes in liver metabolism during cachexia, and support investigating metabolic strategies such as supplementing glutathione or glucose to reduce cachexia associated morbidity.

References: (1) Argiles, J. M., et al. Nature reviews. Cancer 2014, 14, 754-762. (2) Fearon, K. C., et al. HPB (Oxford) 2010, 12, 323-324. (3) Ozola Zalite, I., et al. Pancreatology 2015, 15, 19-24. (4) Porporato, P. E. Oncogenesis 2016, 5, e200. (5) Winnard, P. T., et al. Cancer Research 2015.

Acknowledgment: This work was supported by NIH R01 CA193365. We thank Dr. Marie-France Penet for useful discussions.

Citation Format: Santosh K. Bharti, Paul T. Winnard, Yelena Mironchik, Anirban Maitra, Zaver M. Bhujwalla. Interrogating liver metabolic stress due to cancer-induced cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2510. doi:10.1158/1538-7445.AM2017-2510

Effect of Pantethine on Ovarian Tumor Progression and Choline Metabolism

Epithelial ovarian cancer remains the leading cause of death from gynecologic malignancy among women in developed countries. New therapeutic strategies evaluated with relevant preclinical models are urgently needed to improve survival rates. Here, we have assessed the effect of pantethine on tumor growth and metabolism using magnetic resonance imaging and high-resolution proton magnetic resonance spectroscopy (MRS) in a model of ovarian cancer. To evaluate treatment strategies, it is important to use models that closely mimic tumor growth in humans. Therefore, we used an orthotopic model of ovarian cancer where a piece of tumor tissue, derived from an ovarian tumor xenograft, is engrafted directly onto the ovary of female mice, to maintain the tumor physiological environment. Treatment with pantethine, the precursor of vitamin B5 and active moiety of coenzyme A, was started when tumors were ~100 mm³ and consisted of a daily i.p. injection of 750 mg/kg in saline. Under these conditions, no side effects were observed. High-resolution ¹H MRS was performed on treated and control tumor extracts. A dual-phase extraction method based on methanol/chloroform/water was used to obtain lipid and water-soluble fractions from the tumors. We also investigated effects on metastases and ascites formation. Pantethine treatment resulted in slower tumor progression, decreased levels of phosphocholine and phosphatidylcholine, and reduced metastases and ascites occurrence. In conclusion, pantethine represents a novel potential, well-tolerated, therapeutic tool in patients with ovarian cancer. Further in vivo preclinical studies are needed to confirm the beneficial role of pantethine and to better understand its mechanism of action.

Structure and Function of a Prostate Cancer Dissemination-Permissive Extracellular Matrix

Purpose: The poor prognosis of metastatic prostate cancer continues to present a major challenge in prostate cancer treatment. The tumor extracellular matrix (ECM) plays an important role in facilitating metastasis. Here, we investigated the structure and function of an ECM that facilitates prostate cancer metastasis by comparing orthotopic tumors that frequently metastasize to poorly metastatic subcutaneous tumors.Experimental Design: Both tumors were derived from a human prostate cancer PC3 cell line engineered to fluoresce under hypoxia. Second harmonic generation (SHG) microscopy was used to characterize collagen 1 (Col1) fiber patterns in the xenografts as well as in human samples. MRI was used to determine albumin-Gd-diethylenetriaminepenta-acetate (alb-GdDTPA) transport through the ECM using a saturation recovery MR method combined with fast T₁ SNAPSHOT-FLASH imaging. Cancer-associated fibroblasts (CAF) were also quantified in these tumors.Results: Significant structural and functional differences were identified in the prometastatic orthotopic tumor ECM compared to the less metastatic subcutaneous tumor ECM. The significantly higher number of CAFs in orthotopic tumors may explain the higher Col1 fiber volumes in these tumors. In vivo, alb-GdDTPA pooling was significantly elevated in metastatic orthotopic tumors, consistent with the increased Col1 fibers.Conclusions: Developing noninvasive MRI indices of macromolecular transport, together with characterization of Col1 fiber patterns and CAFs can assist in stratifying prostate cancers for aggressive treatments or active surveillance. These results highlight the role of CAFs in supporting or creating aggressive cancers, and the importance of depleting CAFs to prevent metastatic dissemination in prostate cancer. Clin Cancer Res; 23(9); 2245-54. ©2016 AACR.

HIF isoforms have divergent effects on invasion, metastasis, metabolism and formation of lipid droplets

Cancer cells adapt to hypoxia by the stabilization of hypoxia inducible factor (HIF)-α isoforms that increase the transcription of several genes. Among the genes regulated by HIF are enzymes that play a role in invasion, metastasis and metabolism. We engineered triple (estrogen receptor/progesterone receptor/HER2/neu) negative, invasive MDA-MB-231 and SUM149 human breast cancer cells to silence the expression of HIF-1α, HIF-2α or both isoforms of HIF-α. We determined the metabolic consequences of HIF silencing and the ability of HIF-α silenced cells to invade and degrade the extracellular matrix (ECM) under carefully controlled normoxic and hypoxic conditions. We found that silencing HIF-1α alone was not sufficient to attenuate invasiveness in both MDA-MB-231 and SUM149 cell lines. Significantly reduced metastatic burden was observed in single (HIF-1α or HIF-2α) and double α-isoform silenced cells, with the reduction most evident when both HIF-1α and HIF-2α were silenced in MDA-MB-231 cells. HIF-2α played a major role in altering cell metabolism. Lipids and lipid droplets were significantly reduced in HIF-2α and double silenced MDA-MB-231 and SUM149 cells, implicating HIF in their regulation. In addition, lactate production and glucose consumption were reduced. These results suggest that in vivo, cells in or near hypoxic regions are likely to be more invasive. The data indicate that targeting HIF-1α alone is not sufficient to attenuate invasiveness, and that both HIF-1α and HIF-2α play a role in the metastatic cascade in these two cell lines.

Abstract 4228: Imaging and targeting of hypoxic microenvironments in prostate cancer

Cancer cells display an adaptive response to hypoxia through the activation of several genes mediated by the binding of hypoxia inducible factors (HIFs) to hypoxia response elements (HRE) in the promoter region of target gene that results in their increased transcription [1]. HIFs promote key steps in tumorigenesis, including angiogenesis, metabolism, proliferation, metastasis, and differentiation [1]. Bacterial or yeast cytosine deaminase (yCD) converts the nontoxic prodrug 5-fluorocytosine (5-FC) to the anti-cancer drug 5-fluorouracil (5-FU) that is widely used in cancer treatment [2]. Using a lentivirus approach, we established controlled expression of yCD by HRE in prostate cancer cells (PC-3). These cells also report on HIF-1α expression with regulated luciferase (Luc) expression, allowing detection of hypoxia, and the generation of 5-FU from 5-FC by yCD in the presence of hypoxia. Transduction efficiency and reporter activity in response to hypoxia was evaluated by performing luciferase assays, and bioluminescence imaging (BLI) of cells in vitro or in vivo using a Xenogen IVIS Spectrum system. Cell viability in vitro in response to hypoxia in the presence of 5-FC was assessed by MTS assay. In vivo studies were performed by inoculating 2×10⁁6 PC-3-HRE-Luc cells and PC-3-HRE-yCD+Luc cells on either flank of 5-week-old male severely combined immune deficient (SCID) mice. BLI was performed once tumors reached ∼200mm3 followed by 5-FC injection through the tail vein (200mg/kg) and intraperitoneally (250mg/kg). BLI was performed 3 days after the first 5-FC injection and continued through the treatment protocol. At the end of the treatment protocol, tumors were excised, and a part of the tumor was processed for immunohistochemistry. Bioluminescence was detected in both PC3-HRE-Luc and PC-3-HRE-yCD+Luc cells only in response to the hypoxia mimetic cobalt chloride or hypoxia (1% O2) confirming the regulation of luciferase by hypoxia and activation of CD. Expression of yCD and its ability to convert the prodrug 5-FC to 5-FU, with increased cell kill was evident under hypoxia. In vivo, engineered PC-3-HRE-yCD+Luc cells reported hypoxia, and showed significant reduction of hypoxic regions and tumor volume. Morphologically, PC-3-HRE-yCD+Luc tumors exhibited extensive necrosis. We are currently evaluating the effects of eliminating hypoxic cancer cells on distant metastasis as well as on aggressive subpopulations such as cancer stem cells in the primary tumor.

References: [1] Philip, B., et al., Carcinogenesis, 2013. 34(8):1699-707.,[2] Longley DB, et al., Nat Rev Cancer, 2003. 3: 330-38.

Acknowledgements: This work was supported by NIH R01CA136576 and P50 CA103175. We thank Mr. Gary Cromwell for technical assistance

Citation Format: Balaji Krishnamachary, Louis Dore-Savard, Santosh Kumar Bharti, Flonne Wildes, Yelena Mironchik, Margaret E. Black, Zaver M. Bhujwalla. Imaging and targeting of hypoxic microenvironments in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4228.

Detection of Pancreatic Cancer-Induced Cachexia Using a Fluorescent Myoblast Reporter System and Analysis of Metabolite Abundance

The dire effects of cancer-induced cachexia undermine treatment and contribute to decreased survival rates. Therapeutic options for this syndrome are limited, and therefore efforts to identify signs of precachexia in cancer patients are necessary for early intervention. The applications of molecular and functional imaging that would enable a whole-body "holistic" approach to this problem may lead to new insights and advances for diagnosis and treatment of this syndrome. Here we have developed a myoblast optical reporter system with the purpose of identifying early cachectic events. We generated a myoblast cell line expressing a dual tdTomato:GFP construct that was grafted onto the muscle of mice-bearing human pancreatic cancer xenografts to provide noninvasive live imaging of events associated with cancer-induced cachexia (i.e., weight loss). Real-time optical imaging detected a strong tdTomato fluorescent signal from skeletal muscle grafts in mice with weight losses of only 1.2% to 2.7% and tumor burdens of only approximately 79 to 170 mm(3). Weight loss in cachectic animals was also associated with a depletion of lipid, cholesterol, valine, and alanine levels, which may provide informative biomarkers of cachexia. Taken together, our findings demonstrate the utility of a reporter system that is capable of tracking tumor-induced weight loss, an early marker of cachexia. Future studies incorporating resected tissue from human pancreatic ductal adenocarcinoma into a reporter-carrying mouse may be able to provide a risk assessment of cachexia, with possible implications for therapeutic development.

Combining Optical Reporter Proteins with Different Half-lives to Detect Temporal Evolution of Hypoxia and Reoxygenation in Tumors

Here we have developed a hypoxia response element driven imaging strategy that combined the hypoxia-driven expression of two optical reporters with different half-lives to detect temporal changes in hypoxia and hypoxia inducible factor (HIF) activity. For this purpose, human prostate cancer PC3 cells were transfected with the luciferase gene fused with an oxygen-dependent degradation domain (ODD-luc) and a variant of the enhanced green fluorescent protein (EGFP). Both ODD-luciferase and EGFP were under the promotion of a poly-hypoxia-response element sequence (5xHRE). The cells constitutively expressed tdTomato red fluorescent protein. For validating the imaging strategy, cells were incubated under hypoxia (1% O2) for 48 hours and then reoxygenated. The luciferase activity of PC3-HRE-EGFP/HRE-ODD-luc/tdtomato cells detected by bioluminescent imaging rapidly decreased after reoxygenation, whereas EGFP levels in these cells remained stable for several hours. After in vitro validation, PC3-HRE-EGFP/HRE-ODD-luc/tdtomato tumors were implanted subcutaneously and orthotopically in nude male mice and imaged in vivo and ex vivo using optical imaging in proof-of-principle studies to demonstrate differences in optical patterns between EGFP expression and bioluminescence. This novel "timer" imaging strategy of combining the short-lived ODD-luciferase and the long-lived EGFP can provide a time frame of HRE activation in PC3 prostate cancer cells and will be useful to understand the temporal changes in hypoxia and HIF activity during cancer progression and following treatments including HIF targeting strategies.

Abstract 4021: Cyclooxygenase-2 downregulation reduces activated fibroblasts and modifies the extracellular matrix in MDA-MB-231 breast cancer xenograft

COX-2 is an important mediator of inflammation that significantly influences tumor angiogenesis, invasion and metastasis. Here, we have investigated the role of COX-2 in modifying the number of activated cancer associated fibroblasts (CAFs) and in altering the extracellular matrix (ECM) in a breast cancer model.

To investigate the role of COX-2 in modulating the ECM, we used an MDA-MB-231 cell clone (Clone 13) expressing a short hairpin RNA (shRNA) to downregulate COX-2 [1]. Clone 13 cells were characterized for significantly lower basal and TPA-induced COX-2 and PGE2 expression compared to parental MDA-MB-231 cells using ELISA (PGE2), western blot (COX-2 protein) and q-RT-PCR (COX-2 mRNA). Tumors were derived from parental (n = 5) and Clone 13 (n = 6) MDA-MB-231 cells following inoculation in the mammary fat pad in SCID mice. Tumors were excised at ∼ 500 mm3 and immunohistochemically stained to quantify vessel density (CD31) and activated CAFs (α-smooth muscle actin (SMA)) in 5 μm thick formalin fixed sections. Stained sections were digitally scanned and positive staining quantified using manufacturer supplied software (Aperio Technologies, CA).

Clone 13 tumors showed delayed tumor growth compared to parental MDA-MB-231 tumors. We have previously observed that collagen 1 (Col1) fiber density and fiber volume were significantly lower in COX-2 reduced Clone 13 tumors compared to parental tumors [2]. While cancer cells shape Col1 fiber patterns through the secretion of various enzymes, Col1 fiber is laid down by activated CAFs within or around the tumor. Quantification of activated CAFs by immunohistochemistry for α-SMA in the tumors, and immunoblotting for α-SMA of crude protein extracted from the tumors, revealed significantly fewer CAFs and significantly reduced levels of α-SMA protein in Clone 13 tumors compared to parental MDA-MB-231 tumors. We previously observed a significant decrease in permeability as well as reduced influx and efflux of macromolecular transport in Clone 13 tumors compared to parental tumors, but no difference in vascular volume [2]. Immunohistochemistry for CD31 staining of endothelial cells did not detect a significant difference in CD31 density between Clone 13 and parental tumors further confirming our previous observations about vascular volume. These data reveal the multi-faceted effects of COX-2 in modifying the structure and function of the ECM, and identify the ability to attract and activate fibroblasts as one mechanism by which COX-2 modifies the ECM.

Acknowledgements: We thank Mr. Gary Cromwell for technical assistance. This work was supported by NIH R01CA82337 and P50 CA103175.

References: [1] Stasinopoulos, I., et al., Mol Cancer Res, 2007; [2], Stasinopoulos, I., et al., AACR, 2013 Chicago.

Citation Format: Balaji Krishnamachary, Ioannis Stassinopoulos, Samata M. Kakkad, Marie-France Penet, Desmond Jacob, Flonne Wildes, Yelena Mironchik, Arvind Pathak, Meiyappan Solaiyappan, Zaver M. Bhujwalla. Cyclooxygenase-2 downregulation reduces activated fibroblasts and modifies the extracellular matrix in MDA-MB-231 breast cancer xenograft. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4021. doi:10.1158/1538-7445.AM2015-4021

Abstract 1484: Pancreatic cancer and normal pancreas water content and its impact in metabolite quantification

The absence of early symptoms in pancreatic cancer creates a critical need for identifying new noninvasive biomarkers. Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) are being evaluated in the diagnosis of several solid malignancies. A hallmark of most solid tumors is the detection of elevated phosphocholine (PC) and total choline (tCho). We previously observed elevated levels of tCho in several pancreatic cancer cell lines and tumor xenografts (1). Initial single voxel studies performed in humans suggest that the tCho signal normalized to water may be relatively high in normal pancreas compared to pancreatic tumor (2). Since metabolites are normalized to the water signal it is important to determine differences in its content for accurate quantification. Here, we quantified tCho in orthotopic and subcutaneous Panc1 pancreatic xenografts, and in normal pancreas. 1H MRSI acquired on a 9.4T spectrometer showed heterogeneous tCho signal in orthotopic tumors. To further determine differences in tCho, tumor tissues and pancreas were embedded in agarose and imaged ex vivo with 1H MRSI. Concentration of tCho was 3.38 ± 0.95 mM in orthotopic tumors, 1.32 ± 0.59 mM in subcutaneous tumors, and 1.27 ± 0.52 mM in normal pancreas (n = 2), when using the uncorrected water signal for normalization. Despite a much higher tCho signal in the subcutaneous tumors, tCho concentrations were comparable to the pancreas.

We next estimated the water content of the tumors and the pancreas as a ratio of wet weight to dry weight (measured after 72h of lyophilization) and confirmed a significantly higher water content in tumors compared to the pancreas (wet to dry weight ratio of ∼ 6 vs ∼ 4). A separate set of tumors were freeze-clamped and used for high-resolution 1H MRS. Tumor and pancreas extracts were obtained using a dual-phase extraction method and 1H MR spectra were acquired as previously described (3). To determine the tCho concentration, peak integrations from spectra for choline, PC and glycerophosphocholine were compared to an internal standard. Integrals of the metabolites of interest were determined and normalized first to the tissue wet weight. Once the tCho concentration in tumors and pancreas was corrected for differences in water content, a two-fold higher tCho concentration was observed in tumor tissue compared to normal pancreas. These data support the use of 1H MRSI that provides a tCho map rather than the placement of single voxels to address heterogeneities in the pancreas and in pancreatic cancers. The results highlight the importance of quantifying water content in the calculation of metabolite concentration when comparing different tissues.

Work supported by NIH P50CA103175. (1) Penet et al., Clin Cancer Res (2014). (2) Ma et al., Journal of computer assisted tomography (2011). (3) Shah et al., NMR Biomed (2012).

Citation Format: Marie-France Penet, Balaji Krishnamachary, Tariq Shah, Yelena Mironchik, Anirban Maitra, Zaver M. Bhujwalla. Pancreatic cancer and normal pancreas water content and its impact in metabolite quantification. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1484. doi:10.1158/1538-7445.AM2015-1484

Abstract 5110: Initial characterization of an optical reporter myoblast cell line for non-invasive imaging in a cancer cachexia model in mice

Cancer associated cachexia affects a majority of patients during cancer progression, compromising therapeutic interventions and contributing to decreased survival rates. Identifying factors involved in the onset of cachexia will provide a better understanding of early treatment strategies. To this end, we developed a mouse model system that allows for real time longitudinal monitoring of cancer induced wasting and has the potential of identifying early cachectic events. Several attributes of our system are new. 1) The construction of a dual optical reporter vector with green fluorescence protein (GFP) expression constitutively driven from an EF1α promoter and red fluorescence protein (tdTomato) expression driven by an engineered skeletal muscle specific inducible promoter. The latter is a synthetic sequence of a triple-tandem repeat of the glucocorticoid-FOXO1 response element region from the proximal promoter of the human MuRF1 gene. 2) Generation of a rat L6 myoblast optical reporter cell line (To3B cells) with stable integration of the dual reporter vector construct, which provides living reporter grafts within mouse muscle. 3) A human pancreatic cancer cell line (Pa04C) that as an orthotopic or subcutaneous xenograft causes weight loss in male SCID mice. In preliminary studies, we tested several human pancreatic cancer cell lines as orthotopic xenografts in male SCID mice. We found that red fluorescence signals were reproducibly detected in live mice only from To3B grafts in mice undergoing weight loss, while graft size and viability were readily monitored by imaging GFP fluorescence in all animals. In addition, mice bearing Pa04C tumors lost the most weight while mice bearing Panc1 tumors gained weight. Therefore, Pa04C and Panc1 cells were used for subcutaneous xenografts in male SCID mice and weight loss was followed with optical monitoring of To3B grafts. Importantly, in weight losing mice, we found that red fluorescence could be detected and quantified at a nascent stage of the syndrome; e.g., unambiguous red fluorescent signals were quantified at weight losses of only 1.2 to 2.7% at very low tumor burdens of only ∼0.079 to ∼0.170 cm3. Red fluorescence remained very low to undetectable in mice that gained weight. Tumor sizes were comparable between groups, which was an indication that factors independent of tumor growth were involved in switching on red fluorescence. Ex vivo fluorescence microscopy confirmed a robust presence of red fluorescence only in To3B grafts in skeletal muscle from Pa04C tumor bearing mice. The evidence from this initial development of a unique optical reporter myoblast cell line indicates the potential to detect the onset of cancer cachexia. These studies set the ground work for future research aimed at identifying initiating systemic as well as local molecular events in the muscle of cachectic mice.

Supported by NIH P50CA103175

Citation Format: Paul T. Winnard, Marie-France Penet, Yelena Mironchik, Flonne Wildes, Anirban Maitra, Zaver M. Bhujwalla. Initial characterization of an optical reporter myoblast cell line for non-invasive imaging in a cancer cachexia model in mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5110. doi:10.1158/1538-7445.AM2015-5110

Abstract 1490: Matrigel rescues breast cancer cells from the growth inhibitory effects of HIF-1α and HIF-2α silencing

Tumor microenvironments are frequently hypoxic and result in the stabilization of hypoxia inducible factors (HIF-1/2) that transcriptionally activate genes involved in invasion, metastasis, metabolism and angiogenesis [1]. The role of hypoxia and the contribution of HIF in the angiogenic switch leading to tumor progression and resistance to treatment are well documented. This angiogenic response to HIF activity is largely mediated through activation of vascular endothelial growth factor (VEGF). Noninvasive characterization of the loss of both isoform of HIFs (HIF-1α & HIF-2α) on tumor vascularization is relatively unexplored. Here we investigated the effect of HIF silencing on tumor growth in the presence or absence of Matrigel that resembles the complex extracellular matrix (ECM) found in most tumors and determined its effect on tumor vasculature using noninvasive MRI.

MDA-MB-231 human breast cancer cells expressing shRNA against both HIF-1α and HIF-2α (231-DK) were established as previously described [2]. In vivo studies were performed using MDA-MB-231 breast cancer cells expressing an empty vector control (231-EV) and 231-DK cells implanted in the mammary fat pad of female SCID mice. Tumor growth curves were obtained from cells inoculated either in 0.05 ml of Hanks balanced salt solution (HBSS) or together with Matrigel solution (8.8 mg/ml). All MRI studies were performed on a 9.4T Bruker Biospec horizontal bore scanner. 3D maps of vascular volume (V/V) and permeability (VP) were obtained using a rapid gradient-echo sequence and albumin-GdDTPA (0.5 g/kg) as the contrast agent (CA). A proton density (PD) image was acquired prior to CA injection, using a 3D gradient echo sequence, with TE/TR = 1.5/10 ms and 3° flip angle and analysis of the images were performed as previously described [3].

Exposure to hypoxia showed no increase in HIF-1 or 2α protein expression in 231-DK compared to 231-EV cells. A significant growth advantage of the 231-DK cells in vivo was observed when inoculated in the presence of Matrigel compared to 231-DK in HBSS. Growth advantage of tumors in the presence of Matrigel was less dramatic for 231-EV cells. When inoculated with Matrigel, 3D reconstructed maps of 231-DK tumors showed significantly increased VP compared to 231-EV tumors with no difference in the VV. Increased vascular permeability in tumors derived from 231-DK cells compared to tumors derived from 231-EV cells can be attributed to VEGF in the Matrigel that is known to exhibit paracrine effects. These data suggest that ECM components may modulate molecular targeting and highlight the importance of the tumor microenvironment in modifying HIF silencing effects. Work is under way to analyze the effects on the metastatic burden in these systems.

References: 1. Semenza, Trends in Mol. Med, 2002; 2. Krishnamachary et al., PLoS One, 2012; 3. Zhu et al., Magn Reson Mater Physics, 2014.

Supported by NIH R01CA136576 and P50 CA103175.

Citation Format: Santosh K. Bharti, Balaji Krishnamachary, Wenlian Zhu, Flonne Wildes, Yelena Mironchik, Samata M. Kakkad, Dmitri Artemov, Zaver M. Bhujwalla. Matrigel rescues breast cancer cells from the growth inhibitory effects of HIF-1α and HIF-2α silencing. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1490. doi:10.1158/1538-7445.AM2015-1490

Metabolic imaging of pancreatic ductal adenocarcinoma detects altered choline metabolism

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and lethal disease that develops relatively symptom-free and is therefore advanced at the time of diagnosis. The absence of early symptoms and effective treatments has created a critical need for identifying and developing new noninvasive biomarkers and therapeutic targets.

EXPERIMENTAL DESIGN

We investigated the metabolism of a panel of PDAC cell lines in culture and noninvasively in vivo with (1)H magnetic resonance spectroscopic imaging (MRSI) to identify noninvasive biomarkers and uncover potential metabolic targets.

RESULTS

We observed elevated choline-containing compounds in the PDAC cell lines and tumors. These elevated choline-containing compounds were easily detected by increased total choline (tCho) in vivo, in spectroscopic images obtained from tumors. Principal component analysis of the spectral data identified additional differences in metabolites between immortalized human pancreatic cells and neoplastic PDAC cells. Molecular characterization revealed overexpression of choline kinase (Chk)-α, choline transporter 1 (CHT1), and choline transporter-like protein 1 (CTL1) in the PDAC cell lines and tumors.

CONCLUSIONS

Collectively, these data identify new metabolic characteristics of PDAC and reveal potential metabolic targets. Total choline detected with (1)H MRSI may provide an intrinsic, imaging probe-independent biomarker to complement existing techniques in detecting PDAC. The expression of Chk-α, CHT1, and CTL1 may provide additional molecular markers in aspirated cytological samples.

Abstract 509: Hypoxia and HIF silencing mediated dysregulation of total choline, CD44 expression, and metastatic burden in MDA-MB-231 human breast cancers

Hypoxic tumors frequently exhibit an aggressive phenotype due to dysregulated gene expression and metabolic changes. Hypoxia results in the stabilization of hypoxia inducible factors (HIF-1/2) that transcriptionally activate genes involved in invasion, metastasis, metabolism, and in the adaptation of cancer cells to their microenvironment. In breast cancer, stem-like breast cancer cells that survive, repopulate and metastasize to distant locations, have elevated expression of CD44. In a previous study, we observed elevated expression of CD44 in hypoxic tumor regions, and identified HIF-1α as a regulator of CD44 expression in breast cancer cells under hypoxic conditions [1]. Hypoxia has also been implicated in increasing the activity of choline kinase (Chk)-alpha, the enzyme responsible for elevated phosphocholine (PC) and total choline (tCho) consistently observed in cancers [2]. In previous studies, lentiviral transduction of MDA-MB-231 breast cancer cells (231 cells) with shRNA against Chk-alpha and the in vivo delivery of the Chk-shRNA virus into tumor bearing mice resulted in decreased CD44 message and expression together with effective silencing of Chk message and expression [3]. Here, using non-invasive proton magnetic resonance spectroscopic imaging (1H MRSI), we have established the importance of HIF in reducing total choline and metastatic tumor burden, and have identified a role for CD44 in establishing lung metastasis. HIF silencing in MDA-MB-231 cells significantly delayed tumor growth in mice. Both, the in vitro 1H and 31P MR spectra and in vivo 1H MRS images of tumors derived from engineered cells showed decreased tCho levels and distribution. This decrease of tCho was statistically significant in tumors derived from double silenced cells. Western blot analysis of tumors detected a decrease in Chk expression in double silenced (HIF-1 and 2) tumors. Silencing HIF-1α, -2α or both resulted in a significant reduction of metastatic lung burden in mice. Additionally, HIF-2α silencing was more effective at reducing lung colonization than HIF-1α, while silencing both was the most effective. Although metastatic burden decreased in HIF-1α silenced cells, the percentage of cells with high CD44 expression in the metastatic foci was comparable to that in the wild type or empty vector foci. These data identify the importance of targeting HIF and CD44 to prevent lung colonization and disrupt the metastatic cascade.

This work was supported by NIH R01CA136576 and P50 CA103175. We thank Mr. Gary Cromwell for valuable technical assistance.

References: 1. Krishnamachary B. et al., PLoS One, 2012; 2. Glunde, K., et al., Cancer Res, 2008; 3. Ackerstaff E. et al., Neoplasia. 2007.

Citation Format: Balaji Krishnamachary, Santosh Kumar Bharti, Marie-France Penet, Samata M. Kakkad, Flonne Wildes, Keve Zoltani, Yelena Mironchik, Zaver M. Bhujwalla. Hypoxia and HIF silencing mediated dysregulation of total choline, CD44 expression, and metastatic burden in MDA-MB-231 human breast cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 509. doi:10.1158/1538-7445.AM2014-509

Phospholipase D1 and choline kinase-α are interactive targets in breast cancer

A consistent metabolic hallmark observed in multiple cancers is the increase of cellular phosphocholine (PC) and total choline-containing compounds (tCho), which is closely related to malignant transformation, invasion, and metastasis. Enzymes in choline phospholipid metabolism present attractive targets to exploit for treatment, but require a clear understanding of the mechanisms underlying the altered choline phospholipid metabolism observed in cancer. Choline kinase-α (Chk-α) is an enzyme in the Kennedy pathway that phosphorylates free choline (Cho) to PC, and its upregulation in several cancers is a major contributor to increased PC levels. Similarly, increased expression and activity of phospholipase D1 (PLD1), which converts phosphatidylcholine (PtdCho) to phosphatidic acid (PA) and Cho, has been well documented in gastric, ovarian and breast cancer. Here we report a strong correlation between expression of Chk-α and PLD1 with breast cancer malignancy. Data from patient samples established an association between estrogen receptor (ER) status and Chk-α and PLD1 expression. In addition, these two enzymes were found to be interactive. Downregulation of Chk-α with siRNA increased PLD1 expression, and downregulation of PLD1 increased Chk-α expression. Simultaneous silencing of PLD1 and Chk-α in MDA-MB-231 cells increased apoptosis as detected by the TUNEL assay. These data provide new insights into choline phospholipid metabolism of breast cancer, and support multiple targeting of enzymes in choline phospholipid metabolism as a strategy for treatment.

Abstract 2670: Metabolomic and molecular insights into pancreatic cancer-induced cachexia

Pancreatic cancer is an aggressive and lethal neoplasm that induces cachexia and is typically detected at an advanced stage. Better understanding of the disease, early detection, and new therapeutic targets are urgently needed. Here we have investigated the metabolism of multiple pancreatic tumors, and their effect on mouse body weight. To understand the interactions between the tumor and normal tissue, we are developing a cell-based optical biosensor using genetically engineered myoblasts to detect the early onset of cachexia-inducing signals in muscle tissue. We have also characterized the expression of choline kinase (Chk), which is known to be overexpressed in aggressive cancer, and cyclooxygenase 2 (COX-2), a critically important inflammation mediator that significantly influences cancer angiogenesis, invasion, and metastasis. Human pancreatic adenocarcinoma cell lines Pa02C and Pa04C (Jones et al, Science 2008), as well as Panc1, and BxPC3 (obtained from ATCC), were inoculated subcutaneously in male SCID mice. Mouse bodyweight was followed for approximately 6 weeks. Tumors (500 mm3) were excised and freeze-clamped for immunoblot and high-resolution 1H MRS analyses. A loss of body weight was observed after inoculation of Pa04C and Panc1 cells but not BxPc3 and Pa02C cells. Panc1 tumors exhibited high expression levels of COX-2 and the highest levels of Chk. However, Pa04C tumors showed low levels of those two proteins. 1H MRS analysis revealed that Panc1 tumors contained the highest level of total choline, mainly due to a high level of phosphocholine, correlating with the high level of Chk. Panc1 tumors were also characterized by a high level of lactate. Pa04C tumors presented with the second highest levels of total choline and lactate. To determine the effect of pancreatic cancer cells on muscle, we transiently co-transfected primary human myoblasts with constitutive EF-1α driven eGFP expression and with either a control vector, triple-tandem repeat of a NFκB cis-element lacking a minimal promoter (mp) sequence, or with the same tandem repeat fused to a minimal promoter sequence (3xNFκB-mp) driving tdTomato expression. The transfected myoblasts were differentiated into myotubes and then treated for 24 h with conditioned medium from pancreatic tumor cells. We observed that the 3xNFκB-mp promoter was inducible in the presence of conditioned medium obtained from both Panc1 and Pa04C cells. No red fluorescence was induced in undifferentiated myoblasts or in confluent myoblasts. The acquisition of in vivo 1H MRSI is ongoing, and should further improve the characterization of those pancreatic cell lines, and the correlation between the metabolites measured in vivo and weight loss. Our data identify increased total choline and lactate as potential imaging biomarkers to detect pancreatic cancer, and Chk and COX-2 as potential therapeutic targets of this devastating disease.

This work was supported by NIH P50CA103175.

Citation Format: Marie-France Penet, Paul T. Winnard, Flonné Wildes, Yelena Mironchik, Tariq Shah, Anirban Maitra, Zaver M. Bhujwalla. Metabolomic and molecular insights into pancreatic cancer-induced cachexia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2670. doi:10.1158/1538-7445.AM2013-2670

Abstract 3745: Validation of the co-expression of breast cancer stem cell markers with HIF-1α in tumors

Stem-like breast cancer cells (SBCCs) are drug resistant, invasive, and likely to lead to tumor recurrence and repopulation. High expression of the adhesion molecule CD44, the drug transporter ABCG2, and of the enzyme ALDH1A1 are well-established markers associated with SBCC-enriched tumor populations [1]. Hypoxic tumor microenvironments are frequently associated with increased aggressiveness and resistance to chemo and radiation therapy. Hypoxia results in the stabilization of the hypoxia inducible factor -1 (HIF-1), a transcription factor that activates a battery of genes, including those associated with SBCCs, that help cancer cells to survive, repopulate and finally metastasize to distant location. Recently, we reported the role of hypoxia and HIF-1α in regulating the expression of CD44 and its variant isoforms in triple negative breast cancer [2]. Here we have validated the association between hypoxia and CD44 expression in these tumors. We used tumors derived from MDA-MB-231 cells genetically engineered to express red fluorescent protein (tdtomato) under the control of hypoxia response element (231-HRE-RFP). Optical imaging (Nikon fluorescence microscope) was performed to detect hypoxia in fresh tissue slices, followed by immunohistochemistry (IHC) staining for HIF-1α, CD44 and ABCG2 expression in 5μm thickness adjacent sections from paraffin embedded 231-HRE-RFP tumors. Slides were scanned on an Image Scope digital scanner. Analysis for HIF-1 α nuclear staining was performed by drawing regions of interest (ROI) on scanned images using manufacturer supplied macro (Aperio Technologies Inc. CA, USA). For co-registration and quantification studies, ROI drawn images of HIF-1α and CD44 were co-registered to the bright field and fluorescent optical images using an in-house program developed in MATLAB (Mathworks Inc.). Statistical analysis (t-test) was performed using Microsoft Excel 2010 (Microsoft Inc. Seattle, USA). Following co-registration, intensely fluorescing regions of 231-HRE-RFP tumors were found to be associated with elevated nuclear HIF-1α expression and higher CD44 membrane expression. A trend of increased optical intensity (p≤0.09) and significantly increased CD44 pixel intensity (p≤0.05) was observed in the high HIF-1α ROI compared to the low HIF-1α ROI. Work is under way to co-register other breast cancer stem cell markers such as ABCG2 and ALDH1A1 in these tumors. These data further highlight the role of hypoxia in engendering a stem-like phenotype, and the potential importance of targeting hypoxia to minimize the burden of cells with stem-like characteristics in tumors. All animal protocols were approved by the JHU animal care and use committee.

This work was supported by NIH R01CA136576 and P50 CA103175.

1. Al-Hajj, M et al., Proc Natl Acad Sci U S A, 2003.

2. Krishnamachary.B. et al., PLoS One 2012;7(8)e44078-

Citation Format: Balaji Krishnamachary, Samata Kakkad, Marie-France Penet, Keve Zoltani, Venu Raman, Mayur Gadiya, Yelena Mironchik, Flonne Wildes, Zaver M. Bhujwalla. Validation of the co-expression of breast cancer stem cell markers with HIF-1α in tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3745. doi:10.1158/1538-7445.AM2013-3745

Hypoxia regulates CD44 and its variant isoforms through HIF-1α in triple negative breast cancer

BACKGROUND

The CD44 transmembrane glycoproteins play multifaceted roles in tumor progression and metastasis. CD44 expression has also been associated with stem-like breast cancer cells. Hypoxia commonly occurs in tumors and is a major cause of radiation and chemo-resistance. Hypoxia is known to inhibit differentiation and facilitates invasion and metastasis. Here we have investigated the effect of hypoxia on CD44 and two of its isoforms in MDA-MB-231 and SUM-149 triple negative human breast cancer cells and MDA-MB-231 tumors using imaging and molecular characterization.

METHODS AND FINDINGS

The roles of hypoxia and hypoxia inducible factor (HIF) in regulating the expression of CD44 and its variant isoforms (CD44v6, CD44v7/8) were investigated in human breast cancer cells, by quantitative real-time polymerase chain reaction (qRT-PCR) to determine mRNA levels, and fluorescence associated cell sorting (FACS) to determine cell surface expression of CD44, under normoxic and hypoxic conditions. In vivo imaging studies with tumor xenografts derived from MDA-MD-231 cells engineered to express tdTomato red fluorescence protein under regulation of hypoxia response elements identified co-localization between hypoxic fluorescent regions and increased concentration of (125)I-radiolabeled CD44 antibody.

CONCLUSIONS

Our data identified HIF-1α as a regulator of CD44 that increased the number of CD44 molecules and the percentage of CD44 positive cells expressing variant exons v6 and v7/8 in breast cancer cells under hypoxic conditions. Data from these cell studies were further supported by in vivo observations that hypoxic tumor regions contained cells with a higher concentration of CD44 expression.