Abstract 5175: γ-Mangostin, a natural xanthone derivative targets Wnt signaling pathway in colon cancer cells

Background: Colorectal cancer is the third most common cancer in incidence and cause of death in the United States. The current treatment modalities include chemotherapy, radiation, and surgery. Many people are genetically predisposed for colon cancer through mutations in genes such as adenomatous polyposis coli (APC).  While the absence of APC causes aberrant Wnt/Beta catenin signaling, the APC mutations are found in more than 80% of colorectal tumors.  γ-Mangostin is a major bioactive compound present in Mangosteen (Garcinia mangostana) which possess significant anti-cancer activity. Herein, we investigated the effects of γ -Mangostin on colon cancer growth and elucidated its mechanistic action through Wnt signaling pathway.

Methods: HCT116, SW480 and RKO cell lines were used in the study. The effects of γ-Mangostin on cell proliferation were assessed by hexosaminidase and clonogenicity assays. Effects of γ-Mangostin on apoptosis were evaluated by cell cycle and western blot analysis. Moreover the effect of γ-Mangostin on colonosphere formation was also evaluated. Furthermore, the effect of γ-Mangostin on Wnt signaling proteins was evaluated by western blot analysis. The in vivo anti-cancer effect of γ -Mangostin was investigated on the HCT116 subcutaneous tumor xenograft model implanted in five-week-old male athymic nude mice. Further, the effect of γ -Mangostin was assessed by the specific marker expression in tissue samples by western blot analysis and immunohistochemistry.

Results: γ-Mangostin treatment resulted in a dose and time dependent inhibition of proliferation and colony formation in all the three cell lines. Treatment also induced colon cancer cells to undergo G0/G1 and S-phase arrest. Apoptosis was confirmed by increased levels of Bax/Bcl2 ratio, coupled with a reduction in cyclin D1. γ -Mangostin significantly reduced the number and size of colonospheres. Moreover, γ-Mangostin treatment decreased the expression of Wnt signaling proteins, which suggest that γ-Mangostin inhibits the colon cancer growth through Wnt signaling pathway. To determine the effect of γ-Mangostin on tumor growth in vivo, nude mice harboring HCT116 tumor xenografts in their flanks were administered with 5mg/Kg γ-Mangostin intraperitoneally for 21 days. γ-Mangostin treatment significantly reduced the tumor growth, with notably lower tumor volume and weight. Western blot and immunohistochemistry analyses revealed significant decrease in the expression of Wnt signaling proteins.

Conclusion: Together, these data suggest that γ-Mangostin inhibits colon cancer growth through Wnt signaling pathway. γ-Mangostin may be a potential therapeutic agent for colon cancer.

Citation Format: Balaji Krishnamachary, Dharmalingam Subramaniam, Thomas Attard, Seth Septer, Shrikant Anant. γ-Mangostin, a natural xanthone derivative targets Wnt signaling pathway in colon cancer cells [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 5175. doi:10.1158/1538-7445.AM2017-5175

Delayed Progression of Lung Metastases Following Delivery of a Prodrug-activating Enzyme

BACKGROUND

Chemotherapy is an effective option to treat recurrent or metastatic cancer but its debilitating side-effects limit the dose and time of exposure. Prodrugs that can be activated locally by an activating enzyme can minimize collateral damage from chemotherapy. We previously demonstrated the efficacy of a poly-L-lysine-based theranostic nanoplex containing bacterial cytosine deaminase (bCD) that locally converted 5-fluorocytosine (5-FC) to the chemotherapeutic agent 5-fluorouracil in MDA-MB-231 primary tumor xenografts.

MATERIALS AND METHODS

Here we used a more effective variant of bCD to target metastatic red fluorescence protein expressing MDA-MB-435 cells in the lungs. We used an intravenous injection of tumor cells and monitored tumor growth in the lungs for 5 weeks by which time metastatic nodules were detected with optical imaging. The animals were then treated with the bCD-nanoplex and 5-FC.

RESULTS

We observed a significant decrease in metastatic burden with a single dose of the enzyme-nanoplex and two consecutive prodrug injections.

CONCLUSION

These results are a first step towards the longitudinal evaluation of such a strategy with multiple doses. Additionally, the enzyme can be directly coupled to imaging reporters to time prodrug administration for the detection and treatment of aggressive metastatic cancer.

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.

Collagen fibers mediate MRI-detected water diffusion and anisotropy in breast cancers

Collagen 1 (Col1) fibers play an important role in tumor interstitial macromolecular transport and cancer cell dissemination. Our goal was to understand the influence of Col1 fibers on water diffusion, and to examine the potential of using noninvasive diffusion tensor imaging (DTI) to indirectly detect Col1 fibers in breast lesions. We previously observed, in human MDA-MB-231 breast cancer xenografts engineered to fluoresce under hypoxia, relatively low amounts of Col1 fibers in fluorescent hypoxic regions. These xenograft tumors together with human breast cancer samples were used here to investigate the relationship between Col1 fibers, water diffusion and anisotropy, and hypoxia. Hypoxic low Col1 fiber containing regions showed decreased apparent diffusion coefficient (ADC) and fractional anisotropy (FA) compared to normoxic high Col1 fiber containing regions. Necrotic high Col1 fiber containing regions showed increased ADC with decreased FA values compared to normoxic viable high Col1 fiber regions that had increased ADC with increased FA values. A good agreement of ADC and FA patterns was observed between in vivo and ex vivo images. In human breast cancer specimens, ADC and FA decreased in low Col1 containing regions. Our data suggest that a decrease in ADC and FA values observed within a lesion could predict hypoxia, and a pattern of high ADC with low FA values could predict necrosis. Collectively the data identify the role of Col1 fibers in directed water movement and support expanding the evaluation of DTI parameters as surrogates for Col1 fiber patterns associated with specific tumor microenvironments as companion diagnostics and for staging.

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.

Targeting choline phospholipid metabolism: GDPD5 and GDPD6 silencing decrease breast cancer cell proliferation, migration, and invasion

Abnormal choline phospholipid metabolism is associated with oncogenesis and tumor progression. We have investigated the effects of targeting choline phospholipid metabolism by silencing two glycerophosphodiesterase genes, GDPD5 and GDPD6, using small interfering RNA (siRNA) in two breast cancer cell lines, MCF-7 and MDA-MB-231. Treatment with GDPD5 and GDPD6 siRNA resulted in significant increases in glycerophosphocholine (GPC) levels, and no change in the levels of phosphocholine or free choline, which further supports their role as GPC-specific regulators in breast cancer. The GPC levels were increased more than twofold during GDPD6 silencing, and marginally increased during GDPD5 silencing. DNA laddering was negative in both cell lines treated with GDPD5 and GDPD6 siRNA, indicating absence of apoptosis. Treatment with GDPD5 siRNA caused a decrease in cell viability in MCF-7 cells, while GDPD6 siRNA treatment had no effect on cell viability in either cell line. Decreased cell migration and invasion were observed in MDA-MB-231 cells treated with GDPD5 or GDPD6 siRNA, where a more pronounced reduction in cell migration and invasion was observed under GDPD5 siRNA treatment as compared with GDPD6 siRNA treatment. In conclusion, GDPD6 silencing increased the GPC levels in breast cancer cells more profoundly than GDPD5 silencing, while the effects of GDPD5 silencing on cell viability/proliferation, migration, and invasion were more severe than those of GDPD6 silencing. Our results suggest that silencing GDPD5 and GDPD6 alone or in combination may have potential as a new molecular targeting strategy for breast cancer treatment. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Choline Metabolism Alteration: A Focus on Ovarian Cancer

Compared with normal differentiated cells, cancer cells require a metabolic reprograming to support their high proliferation rates and survival. Aberrant choline metabolism is a fairly new metabolic hallmark reflecting the complex reciprocal interactions between oncogenic signaling and cellular metabolism. Alterations of the involved metabolic network may be sustained by changes in activity of several choline transporters as well as of enzymes such as choline kinase-alpha (ChoK-α) and phosphatidylcholine-specific phospholipases C and D. Of note, the net outcome of these enzymatic alterations is an increase of phosphocholine and total choline-containing compounds, a "cholinic phenotype" that can be monitored in cancer by magnetic resonance spectroscopy. This review will highlight the molecular basis for targeting this pathway in epithelial ovarian cancer (EOC), a highly heterogeneous and lethal malignancy characterized by late diagnosis, frequent relapse, and development of chemoresistance. Modulation of ChoK-α expression impairs only EOC but not normal ovarian cells, thus supporting the hypothesis that "cholinic phenotype" is a peculiar feature of transformed cells and indicating ChoK-α targeting as a novel approach to improve efficacy of standard EOC chemotherapeutic treatments.

Global metabolic profile identifies choline kinase alpha as a key regulator of glutathione-dependent antioxidant cell defense in ovarian carcinoma

Epithelial Ovarian Cancer (EOC) "cholinic phenotype", characterized by increased intracellular phosphocholine content sustained by over-expression/activity of choline kinase-alpha (ChoKα/CHKA), is a metabolic cellular reprogramming involved in chemoresistance with still unknown mechanisms.By stable CHKA silencing and global metabolic profiling here we demonstrate that CHKA knockdown hampers growth capability of EOC cell lines both in vitro and in xenotransplant in vivo models. It also affected antioxidant cellular defenses, decreasing glutathione and cysteine content while increasing intracellular levels of reactive oxygen species, overall sensitizing EOC cells to current chemotherapeutic regimens. Natural recovering of ChoKα expression after its transient silencing rescued the wild-type phenotype, restoring intracellular glutathione content and drug resistance. Rescue and phenocopy of siCHKA-related effects were also obtained by artificial modulation of glutathione levels. The direct relationship among CHKA expression, glutathione intracellular content and drug sensitivity was overall demonstrated in six different EOC cell lines but notably, siCHKA did not affect growth capability, glutathione metabolism and/or drug sensitivity of non-tumoral immortalized ovarian cells. The "cholinic phenotype", by recapitulating EOC addiction to glutathione content for the maintenance of the antioxidant defense, can be therefore considered a unique feature of cancer cells and a suitable target to improve chemotherapeutics efficacy.

Magnetic Resonance Spectroscopy of siRNA-Based Cancer Therapy

Small interfering RNA (siRNA) is routinely used as a biological tool to silence specific genes, and is under active investigation in cancer treatment strategies. Noninvasive magnetic resonance spectroscopy (MRS) provides the ability to assess the functional effects of siRNA-mediated gene silencing in cultured cancer cells, and following nanoparticle-based delivery in tumors in vivo. Here we describe the use of siRNA to downregulate choline kinase, a critical enzyme in choline phospholipid metabolism of cancer cells and tumors, and the use of (1)H MRS of cells and (1)H magnetic resonance spectroscopic imaging (MRSI) of tumors to assess the efficacy of the downregulation.

PSMA-specific theranostic nanoplex for combination of TRAIL gene and 5-FC prodrug therapy of prostate cancer

Metastatic prostate cancer causes significant morbidity and mortality and there is a critical unmet need for effective treatments. We have developed a theranostic nanoplex platform for combined imaging and therapy of prostate cancer. Our prostate-specific membrane antigen (PSMA) targeted nanoplex is designed to deliver plasmid DNA encoding tumor necrosis factor related apoptosis-inducing ligand (TRAIL), together with bacterial cytosine deaminase (bCD) as a prodrug enzyme. Nanoplex specificity was tested using two variants of human PC3 prostate cancer cells in culture and in tumor xenografts, one with high PSMA expression and the other with negligible expression levels. The expression of EGFP-TRAIL was demonstrated by fluorescence optical imaging and real-time PCR. Noninvasive (19)F MR spectroscopy detected the conversion of the nontoxic prodrug 5-fluorocytosine (5-FC) to cytotoxic 5-fluorouracil (5-FU) by bCD. The combination strategy of TRAIL gene and 5-FC/bCD therapy showed significant inhibition of the growth of prostate cancer cells and tumors. These data demonstrate that the PSMA-specific theranostic nanoplex can deliver gene therapy and prodrug enzyme therapy concurrently for precision medicine in metastatic prostate cancer.

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.

Breast cancer cell adhesome and degradome interact to drive metastasis

BACKGROUND

Although primary breast tumors are detected early in most cases, it is inevitable that many patients remain at risk for future recurrence and death due to micrometastases. We investigated interactions between the degradome and the adhesome that drive metastasis, and have focused on matrix metalloproteases (MMPs) within the degradome and integrins and E-cadherin within the adhesome.

AIMS

The aim of this study is to identify interaction networks between adhesion molecules and degradative enzymes in breast cancer metastasis.

METHODS

We compared non-metastatic (BT-474, T47D, MCF7) and metastatic (MDA-MB-231, SUM149, SUM159) human breast cancer cell lines and xenografts, in which we measured growth rate, migration, invasion, colony formation, protein expression, and enzyme activity in vitro and in vivo.

RESULTS

The metastatic breast cancer lines and xenografts displayed higher expression and activity levels of MMPs, which was also confirmed by noninvasive imaging in vivo. These metastatic breast cancer models also displayed elevated heterophilic cell-extracellular matrix (ECM) and lower homophilic cell-cell adhesion compared with those of non-metastatic models. This was conferred by an increased expression of the heterophilic cell adhesion molecule integrin β1 (ITGB1) and a decreased expression of the homophilic cell adhesion molecule E-cadherin. Inhibition of MMPs in metastatic cells led to a reduced expression of ITGB1, and stimulation of ITGB1 resulted in higher MMP activities in metastatic cancer cells, demonstrating reciprocal dependencies between degradome and adhesome. Re-expression of E-cadherin (CDH1) led to an increased expression of the precursor form of ITGB1.

CONCLUSIONS

Our results point toward a concerted interdependence of MMPs, ITGB1, and CDH1 that is critical for breast cancer metastasis.

Imaging transplanted stem cells in real time using an MRI dual-contrast method

Stem cell therapies are currently being investigated for the repair of brain injuries. Although exogenous stem cell labelling with superparamagnetic iron oxide nanoparticles (SPIONs) prior to transplantation provides a means to noninvasively monitor stem cell transplantation by magnetic resonance imaging (MRI), monitoring cell death is still a challenge. Here, we investigate the feasibility of using an MRI dual-contrast technique to detect cell delivery, cell migration and cell death after stem cell transplantation. Human mesenchymal stem cells were dual labelled with SPIONs and gadolinium-based chelates (GdDTPA). The viability, proliferation rate, and differentiation potential of the labelled cells were then evaluated. The feasibility of this MRI technique to distinguish between live and dead cells was next evaluated using MRI phantoms, and in vivo using both immune-competent and immune-deficient mice, following the induction of brain injury in the mice. All results were validated with bioluminescence imaging. In live cells, a negative (T2/T2*) MRI contrast predominates, and is used to track cell delivery and cell migration. Upon cell death, a diffused positive (T1) MRI contrast is generated in the vicinity of the dead cells, and serves as an imaging marker for cell death. Ultimately, this technique could be used to manage stem cell therapies.

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 341: Breast cancer cell adhesion and degradome interact to drive metastasis

Although primary breast tumors are detected early in most cases, it is inevitable that many patients remain at risk for future recurrence and death due to micrometastases. We investigated the metastatic process with a focus on matrix metalloproteases (MMPs) within the degradome and on integrins and E-cadherin within the adhesome. We have performed comparative studies with a set of non-metastatic (BT-474, T47D, MCF7) versus metastatic (MDA-MB-231, SUM149, SUM159) human breast cancer cell lines and xenografts. Experiments were performed to measure growth rate, migration, invasion, and colony formation. Immunoblotting and immunohistochemistry revealed a higher expression of MMPs and heterophilic cell adhesion molecules integrin β1 and lower expression of homophilic cell adhesion molecule E-cadherin in the metastatic tumor cells and xenografts. Using zymography and activatable fluorescent probes for noninvasive imaging of MMPs, we demonstrated that metastatic breast cancer cells and tumors displayed an elevated degradome activity as compared to non-metastatic cells and tumors. Cell adhesion and cell aggregation assays showed an increased heterophilic and decreased homophilic adhesion in the metastatic models. Inhibiting MMPs reduced the expression of integrin β1, and stimulating integrin β1 resulted in higher MMP activities in metastatic cells. Re-expression of E-cadherin in metastatic cells led to a reduced expression of active integrin β1. Finally, circulating breast cancer cells and cells from lung metastatic nodules generated from metastatic tdTomato-fluorescing breast cancer cells displayed a reduced expression of active integrin β1 and less epithelial-mesenchymal-transition (EMT) marker protein S100A4. Our results indicate that proteolytic ECM remodeling by MMPs and cell adhesion by integrin β1 and E-cadherin are interdependent processes that control transformation from benign to invasive carcinoma and are critical for metastasis.

Citation Format: Asif Rizwan, Menglin Cheng, Zaver M. Bhujwalla, Balaji Krishnamachary, Lu Jiang, Kristine Glunde. Breast cancer cell adhesion and degradome interact to drive metastasis. [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 341. doi:10.1158/1538-7445.AM2015-341

Abstract 5364: Delayed progression of lung metastases in a triple-negative breast cancer model following delivery of cytosine deaminase that converts chemotherapeutic prodrug 5-fluorocytosine to 5-fluorouracil

Triple negative breast cancer (TNBC) is aggressive, has a very poor prognosis with a high rate of reoccurrence and is refractory to standard chemo- and radiotherapy. Still, chemotherapy is an effective option to treat recurrent or metastatic cancers if the debilitating side effects limiting the dose and time of exposure can be diminished. The use of pro-drugs that can be activated locally by a prodrug enzyme can minimize collateral damage since the presence of the enzyme in the tumor and clearance from normal tissue can be verified noninvasively with imaging, which allows for optimal timing of prodrug administration (1). We previously demonstrated the efficacy of the prodrug 5-fluorocytosine (5-FC) in primary triple negative MDA-MB-231 xenografts following administration of a poly-L-lysine based theranostic nanoplex containing bacterial cytosine deaminase (bCD) that converts 5-FC to the chemotherapeutic agent 5-fluorouracil. The size of the bCD-nanoplex of ∼ 300 kD allowed its delivery into the tumor interstitium through leaky tumor vasculature but not through normal vasculature (1). Here we used a more effective variant of bCD (2) to target metastatic MDA-MB-231 cells. We injected 2 × 106 td-tomato fluorescent protein expressing MDA-MB-231 cells intravenously and monitored metastases formation in the lungs for 5 weeks by which time metastatic nodules were detected. We then treated the animals with the bCD-nanoplex (300 mg/kg i.v.). Twenty-four hours later, we injected a first dose of 5-FC (200 mg/kg i.v. and 250 mg/kg i.p.), repeated at 72 hours. The animals were followed for 2 weeks with weekly optical imaging at the end of which mice were euthanized and the lungs excised. We histologically evaluated metastatic burden (area occupied by metastatic cells/total lung area) in mice treated with bCD-nanoplex + 5-FC (n = 5) and in mice injected with the bCD-nanoplex only (n = 6). We observed a 32% decrease in metastatic burden in the pro-drug treated group vs the control group (14.8% + 1.5% in treated mice vs 22.0% + 2.6% in control mice, p = 0.03). These results are a first step towards the longitudinal evaluation of such a strategy with multiple doses. Additionally, the nanoplex can be coupled to multimodal imaging reporters (1) to time prodrug administration and improve the detection and treatment of triple negative, hormone refractory metastatic cancers.

References. 1. Li et al., Clin Can Res., 2008; 2. Fuchita et al., Can Res., 2009.

This work was supported by NIH R01CA138515 and P50 CA103175.

Citation Format: Louis Dore-Savard, Zhihang Chen, Paul T. Winnard, Balaji Krishnamachary, Marie-France Penet, Venu Raman, Margaret E. Black, Zaver Bhujwalla. Delayed progression of lung metastases in a triple-negative breast cancer model following delivery of cytosine deaminase that converts chemotherapeutic prodrug 5-fluorocytosine to 5-fluorouracil. [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 5364. doi:10.1158/1538-7445.AM2015-5364

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 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

Abstract 2484: IR700-conjugated anti-CD44 monoclonal antibody for phototherapy theranostics of triple-negative breast cancer

CD44 transmembrane glycoproteins are cell adhesion molecules that play a role in cancer cell proliferation, migration, and invasion.1 CD44 expression is associated with stem-like breast cancer cells1 and is upregulated under hypoxia2 making it a significant target. Monoclonal antibody (mAb)-linked to photosensitizers have achieved targeted phototherapy.3 We developed a CD44 mAb-targeted photosensitizer complex for combined fluorescent detection and phototherapy (PT) of CD44 expressing triple negative breast cancer cells. The mAb conjugate is activated by near-infrared (NIR) light, and demonstrates phototoxic effects selectively in CD44 expressing breast cancer cells following cell membrane binding.

CD44 mAb was conjugated with a NIR phthalocyanine dye, IR700, to form CD44-IR700. MB-MDA-231 (CD44 positive), MCF-7 and BT-474 (CD44 negative) were selected for the cell studies. SDS-PAGE, UV spectroscopy and confocal fluorescence imaging were performed to determine purity, composition and cellular localization of the conjugate. Microscopic observation and cell viability tests were performed to study CD44-specific cell death. Tumor models were established by inoculating 2×106 MB-MDA-231 or BT-474 cells in the upper-right mammary fat pad of athymic female mice. In vivo fluorescence imaging was performed on a Li-Cor Pearl® Impulse scanner. Tumor bearing mice (n = 5 per group) injected with PBS, IR700, anti-CD44 mAb, IgG-IR700 and CD44-IR700 were monitored over a 3 week-period and sacrificed to harvest tumors. NIR light at a dose of 30 J/cm2 was applied on day 1 after injection.

CD44-IR700 demonstrated preferential binding to the cell membrane of MB-MDA-231 but not MCF-7 or BT-474 cells. CD44-specific cell death was initiated by CD44-IR700-mediated PT (>90% of MB-MDA-231 cells were killed immediately, while 88% of MCF-7 cells and 90% of BT-474 cells were alive). Irradiation itself was harmless to cells and there was no cytotoxicity associated with IR700 and CD44 antibody or with CD44-IR700 in the absence of irradiation. In vivo fluorescence imaging verified the 3-fold increased retention of CD44-IR700 in MB-MDA-231 tumors compared to BT-474 tumors. CD44-IR700 injection together with a therapeutic dose of NIR light exposure resulted in significant growth delay in MB-MDA-231 tumors, but not BT-474 tumors. We did not observe tumor growth delay in separate groups of mice injected with PBS, IR700, anti-CD44 mAb, or IgG-IR700, irrespective of NIR light application. Histological studies confirmed a significant increase of necrosis in the treated MDA-MB-231 tumors.

This novel PT theranostic strategy provides a promising opportunity for treating CD44 expressing primary and metastatic triple negative breast cancer.

References: 1. Louderbough et al, Mol Can Res, 2011; 2. Krishnamachary et al, PloS one, 2012; 3. Mitsunaga et al, Nat Med, 2011.

Supported by NIH R01 CA136576 and P50 CA103175.

Citation Format: Jiefu Jin, Balaji Krishnamachary, Hisataka Kobayashi, Zaver Bhujwalla. IR700-conjugated anti-CD44 monoclonal antibody for phototherapy theranostics of triple-negative breast cancer. [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 2484. doi:10.1158/1538-7445.AM2015-2484

Molecular imaging of the tumor microenvironment for precision medicine and theranostics

Morbidity and mortality from cancer and their associated conditions and treatments continue to extract a heavy social and economic global burden despite the transformative advances in science and technology in the twenty-first century. In fact, cancer incidence and mortality are expected to reach pandemic proportions by 2025, and costs of managing cancer will escalate to trillions of dollars. The inability to establish effective cancer treatments arises from the complexity of conditions that exist within tumors, the plasticity and adaptability of cancer cells coupled with their ability to escape immune surveillance, and the co-opted stromal cells and microenvironment that assist cancer cells in survival. Stromal cells, although destroyed together with cancer cells, have an ever-replenishing source that can assist in resurrecting tumors from any residual cancer cells that may survive treatment. The tumor microenvironment landscape is a continually changing landscape, with spatial and temporal heterogeneities that impact and influence cancer treatment outcome. Importantly, the changing landscape of the tumor microenvironment can be exploited for precision medicine and theranostics. Molecular and functional imaging can play important roles in shaping and selecting treatments to match this landscape. Our purpose in this review is to examine the roles of molecular and functional imaging, within the context of the tumor microenvironment, and the feasibility of their applications for precision medicine and theranostics in humans.

Metastatic breast cancer cells in lymph nodes increase nodal collagen density

The most life-threatening aspect of breast cancer is the occurrence of metastatic disease. The tumor draining lymph nodes typically are the first sites of metastasis in breast cancer. Collagen I fibers and the extracellular matrix have been implicated in breast cancer to form avenues for metastasis. In this study, we have investigated extracellular matrix molecules such as collagen I fibers in the lymph nodes of mice bearing orthotopic human breast cancer xenografts. The lymph nodes in mice with metastatic MDA-MB-231 and SUM159 tumor xenografts and tumor xenografts grown from circulating tumor cell lines displayed an increased collagen I density compared to mice with no tumor and mice with non-metastatic T-47D and MCF-7 tumor xenografts. These results suggest that cancer cells that have metastasized to the lymph nodes can modify the extracellular matrix components of these lymph nodes. Clinically, collagen density in the lymph nodes may be a good marker for identifying lymph nodes that have been invaded by breast cancer cells.

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

Abstract 4890: Collagen 1 fibers are a key component in the establishment of distant pulmonary metastasis by breast cancer cells

We previously observed that silencing COX-2 significantly reduced the expression of degradative enzymes such as matrix metalloproteinase 1 (MMP1), and altered the expression of ECM components such as hyaluronan and lumican that play a role in intra-fibrillar collagen spacing [1]. We have also observed that primary human breast cancers that have metastasized have higher collagen 1 (Col1) fiber density and volume [2]. Here, for the first time, we have investigated Col1 fiber patterns in metastatic lung nodules established by metastatic MDA-MB-231 breast cancer cells and their subclone Clone 13 cells that express shRNA to significantly reduce, but not silence, COX-2 expression.

Second harmonic generation (SHG) microscopy studies were performed on H&E stained lung sections obtained from SCID mice five weeks post intravenous injection of MDA-MB-231 (five mice) and Clone 13 (three mice) human breast cancer cells. SHG images of 5-7 fields of view per mouse were acquired from the lung sections on an Olympus FV1000MPE multiphoton microscope, and analyzed for inter-fiber distance and percentage of fiber per metastatic area using in-house software [2]. Reducing COX-2 expression resulted in a significant reduction of metastatic lung burden in mice. Analysis of the Col1 fiber structures of similar sized metastatic nodules revealed significantly fewer fibers and larger inter fiber distance in lung nodules of mice injected with Clone 13 cells compared to parental MDA-MB-231 cells.

Reducing COX-2 resulted in the establishment of significantly fewer metastatic lung nodules with significantly sparser Col1 fibers. These data suggest that the ability to lay down Col1 fibers is a key requirement for the successful establishment of metastatic lesions. Reducing COX-2 expression in MDA-MB-231 breast cancer cells affects the ability of these cancer cells to lay down a Col1 fiber scaffold suitable for cancer cell growth in the lungs. These data identify new aspects of the role of Col1 fibers and COX-2 in the establishment of metastatic lesions.

References: [1] I. Stasinopoulos et al., Neoplasia (2008); [2] S. Kakkad et al., J Biomed Opt (2012).

This work was supported by NIH R01CA82337 and P50CA103175.

Citation Format: Desmond Jacob, Samata M. Kakkad, Balaji Krishnamachary, Ioannis Stasinopoulos, Meiyappan Solaiyappan, Flonne Wildes, Kristine Glunde, Zaver M. Bhujwalla. Collagen 1 fibers are a key component in the establishment of distant pulmonary metastasis by breast cancer cells. [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 4890. doi:10.1158/1538-7445.AM2014-4890

Abstract 3164: Cancer cell adhesion and degradome interact to metastasize

Background: Adhesion molecules of cancer cells interact with the cancer cell degradome. This is evident from (i) co-localized expression of adhesion molecules such as integrins and degradative enzymes such matrix metalloproteases (MMPs), (ii) regulation of degradome activity by integrin signaling, (iii) key integrins and MMPs binding to the same extracellular matrix (ECM) components, and (iv) interaction between integrins and membrane-bound MMPs in cell-ECM communication in several types of cancer (1-8). Integrins and the degradome have both been implicated in breast cancer metastasis. We are testing for the first time the hypothesis that it is the interactome between these two molecular networks that is critical for breast tumor metastasis to occur.

Experimental Design: We performed comparative studies with a panel of non-metastatic (BT-474, T47D, MCF7, SKBr3) versus metastatic (MDA-MB-231, SUM149, SUM159, MDA-MB-468) human breast cancer cell lines and xenografts. All cell lines stably expressed tdTomato fluorescent protein for optical tracking. Comparative immunoblotting, zymography, migration and invasion assays were performed. Enzymatically activatable optical imaging probes IntegriSense (integrins), MMPSense (MMP), and Angiosense (blood vessels) from PerkinElmer were used in our in vivo imaging studies. Primary tumor sizes of 200 mm3 and 600 mm3 were used to account for different stages of tumors growth.

Results: Analysis of 1,144 genes from a panel of 28 human breast cancer cell lines from publicly available data bases (9) showed that metastatic breast cancer cells have significantly (p<0.01) higher levels of cell adhesion (integrin α-1,4,5,6,v, integrin β-1, CD44) and ECM degrading enzymes (MMP-2,3,11,14,16,19). Metastatic human breast cancer cell lines expressed elevated protein levels of MMP-1 and MMP-14 compared to nonmetastatic lines. Zymography demonstrated that metastatic breast cancer cells secreted increased amounts of active MMP-2 and MMP-9 compared to non-metastatic cell lines. Metastatic tumor xenografts displayed significantly higher combined MMP-1,-2,-3,-9,-13 activity along with increased integrin expression compared to non-metastatic tumors in vivo.

Conclusion: Our results show that elevated activity and expression levels of integrins and MMPs coincide in metastatic breast cancer cell lines and xenografts, which indicates that they may cooperate and interact to enable cancer cell escape from the primary tumor and metastasis. We will perform additional studies to further test our hypothesis by combining cancer cell and tumor studies.

References: 1. Knoblauch et al, FASEB J 2007. 2. Friedl et al, Nat Rev Cancer 2003. 3. Birkedal et al, Biol Med 1993. 4. Deryugina et al, Exp Cell Res 2001. 5. Brooks et al, Cell 1996. 6. Mitchell et al, Cancer Res 2010. 7. Gonzalo et al, Biofactors 2008. 8. Chapman et al, Thromb Haemost 2001. 9. Hollestelle et al, Cancer Res Treat 2009.

Citation Format: Asif Rizwan, Menglin Cheng, Balaji Krishnamachary, Lu Jiang, Zaver Bhujwalla, Glunde Kristine. Cancer cell adhesion and degradome interact to metastasize. [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 3164. doi:10.1158/1538-7445.AM2014-3164

Silencing of the glycerophosphocholine phosphodiesterase GDPD5 alters the phospholipid metabolite profile in a breast cancer model in vivo as monitored by (31) P MRS

Abnormal choline phospholipid metabolism is an emerging hallmark of cancer, which is implicated in carcinogenesis and tumor progression. The malignant metabolic phenotype is characterized by high levels of phosphocholine (PC) and relatively low levels of glycerophosphocholine (GPC) in aggressive breast cancer cells. Phosphorus ((31) P) MRS is able to non-invasively detect these water-soluble metabolites of choline as well as ethanolamine phospholipid metabolism. Here we have investigated the effects of stably silencing glycerophosphoester diesterase domain containing 5 (GDPD5), which is an enzyme with glycerophosphocholine phosphodiesterase activity, in MDA-MB-231 breast cancer cells and orthotopic tumor xenografts. Tumors in which GDPD5 was stably silenced with GDPD5-specific shRNA contained increased levels of GPC and phosphoethanolamine (PE) compared with control tumors.

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.

Characterization of choline kinase in human endothelial cells

High choline kinase-α (Chk-α) expression is frequently observed in cancer cells, making it a novel target for pharmacological and molecular inhibition. As inhibiting agents are delivered systemically, it is important to determine Chk-α expression levels in endothelial cells that line both normal and tumor vasculature, and the effect of Chk-α downregulation on these cells. Here, we characterized Chk-α expression and the effect of its downregulation in human umbilical vein endothelial cells (HUVECs) relative to MDA-MB-231 human breast cancer cells. We used small interfering RNA (siRNA) to downregulate Chk-α expression. Basal mRNA levels of Chk-α were approximately three-fold lower in HUVECs relative to MDA-MB-231 breast cancer cells. Consistent with the differences in Chk-α protein levels, phosphocholine levels were approximately 10-fold lower in HUVECs relative to MDA-MB-231 cells. Transient transfection with siRNA-Chk resulted in comparable levels of mRNA and protein in MDA-MB-231 breast cancer cells and HUVECs. However, there was a significant reduction in proliferation in MDA-MB-231 cells, but not in HUVECs. No significant difference in CD31 immunostaining was observed in tumor sections obtained from mice injected with control luciferase-short hairpin (sh)RNA or Chk-shRNA lentivirus. These data suggest that systemically delivered agents that downregulate Chk-α in tumors will not affect endothelial cell proliferation during delivery, and further support the development of Chk-α downregulation as a cancer-specific treatment.

Abstract 4345: PSMA-targeted theranostic nanoplex combining TRAIL gene cDNA and prodrug enzyme delivery for prostate cancer treatment

Prostate cancer (PCa) is the second leading cause of death from cancer in men in the U.S, and there is a compelling need for the development of effective treatments for metastatic PCa. Theranostic approaches that combine detection with treatment hold significant promise for cancer-cell-specific treatments especially with molecular reagents such as cDNA or siRNA that can increase or decrease the expression of genes of interest. We have reported on a prostrate specific membrane antigen (PSMA)-based platform to deliver a prodrug enzyme and small interfering RNA (siRNA) to downregulate gene expression for theranostic imaging of metastatic PCa[1]. Here we expanded this platform for gene delivery and expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) cDNA. PSMA, which is highly expressed by castration-resistant PCa, was used for PCa-specific delivery and localization of the nanoplex that delivered TRAIL cDNA and a prodrug enzyme, bacterial cytosine deaminase (bCD). TRAIL has been reported to specifically kill malignant cells but to be relatively nontoxic to normal cells. The GFP-TRAIL cDNA used expresses a GFP-TRAIL fusion protein that can be detected with optical imaging to evaluate cDNA expression. The prodrug enzyme bCD converts the non-toxic prodrug 5-fluorocytosine (5-FC) to the active cytotoxic drug 5-fluorouracil (5-FU) that can be monitored by 19F MRS. Our prototype nanoplex was synthesized by conjugating: (i) a low molecular weight urea-based PSMA targeting moiety (2-(3-[1-carboxy-5-[7-(2,5-dioxo-pyrrolidin-1-yloxycarbonyl)-heptanoylamino]-pentyl]-ureido)-pentanedioic acid, (ii) the prodrug-activating enzyme bCD that converts nontoxic 5-FC to cytotoxic 5-FU, (iii) the near-infrared fluorescent probe Cy5.5 labeled linker poly-L-lysine (PLL), and (iv) the GFP-TRAIL pDNA delivery vector: PEI (polyethyleneimine)-PEG (polythethyeneglycol) co-grafted-polymer. Imaging studies with PSMA targeted nanoplexes were performed with PC-3 human prostate cancer cells genetically engineered to overexpress PSMA (PC3-PIP); non-PSMA expressing PC-3 cells (PC3-Flu) were used as controls. Cell imaging studies indicated higher expression of GFP-TRAIL fusion protein in PC3-PIP cells. In vivo images obtained from PIP and Flu tumors demonstrated increased accumulation of the nanoplex in PIP tumors. In ex vivo imaging studies, increased uptake of the nanoplex as detected by Cy5.5 fluorescence, and higher expression of GFP in PIP compared to Flu tumors was observed. 19F MRS indicated the prodrug enzyme bCD efficiently converted the prodrug 5-FC to 5-FU at 24 h. Tumor growth studies showed increased inhibition of PIP tumor growth. Collectively, these data demonstrate the ability to express a gene of interest using a theranostic nanoplex specifically targeting cancer cells.

Citation Format: Zhihang Chen, Marie-France Penet Penet, Balaji Krishnamachary, Cong Li, Paul T. Winnard, Martin G. Pomper, Zaver M. Bhujwalla. PSMA-targeted theranostic nanoplex combining TRAIL gene cDNA and prodrug enzyme delivery for prostate cancer treatment. [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 4345. doi:10.1158/1538-7445.AM2013-4345

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

Glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) expression correlates with malignant choline phospholipid metabolite profiles in human breast cancer

Altered choline phospholipid metabolism is a hallmark of cancer, leading to malignant choline metabolite profiles consisting of low glycerophosphocholine (GPC) and high phosphocholine (PC) in human breast cancers. Glycerophosphocholine phosphodiesterase (GPC-PDE) catalyzes the degradation of GPC to free choline and glycerol-3-phosphate. The gene(s) encoding for the GPC-PDE(s) responsible for GPC degradation in breast cancers have not yet been identified. Here, we demonstrate for the first time that the GPC-PDE encoded by glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) is associated with breast cancer malignancy. Two human breast cancer cell lines (n = 8 and n = 10) and primary human breast tumor samples (n = 19) were studied with combined MRS and quantitative reverse transcription-polymerase chain reaction to investigate several isoforms of GDPD expression with respect to choline phospholipid metabolite levels. Of the five GDPDs tested, GDPD5 was found to be significantly overexpressed in highly malignant estrogen receptor negative (ER(-)) compared with weakly malignant estrogen receptor positive (ER(+)) human breast cancer cells (p = 0.027) and breast tumors from patients (p = 0.015). GDPD5 showed significantly positive correlations with PC (p < 0.001), total choline (tCho) (p = 0.007) and PC/GPC (p < 0.001) levels in human breast tumors. GDPD5 showed a trend towards a negative correlation with GPC levels (p = 0.130). Human breast cancers with malignant choline metabolite profiles consisting of low GPC and high PC levels highly co-expressed GDPD5, choline kinase alpha (CHKA) and phosphatidylcholine-specific phospholipase D1 (PLD1), whereas cancers containing high GPC and relatively low PC levels displayed low co-expression of GDPD5, CHKA and PLD1. GDPD5, CHKA and PLD1 were significantly overexpressed in highly malignant ER(-) tumors in our patient cohort. Our study identified GDPD5 as a GPC-PDE that probably participates in the regulation of choline phospholipid metabolism in breast cancer, which possibly occurs in cooperation with CHKA and PLD1.

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.

Scientific validation of the different purification steps involved in the preparation of an Indian Ayurvedic medicine, Lauha bhasma

ETHNOPHARMACOLOGICAL RELEVANCE

Lauha bhasma (iron ash) is one of the iron-based herbo-metallic preparations used in Ayurvedic medicine for treating various ailments due to iron deficiency.

MATERIALS AND METHODS

The preparation of Lauha bhasma (iron ash) requires normal purification (heat treatment in vegetable and animal products), special purification (treatment with herbal constituents) and calcination steps aimed at converting the raw material to a suitable therapeutic form. In this study, we have systematically and scientifically evaluated through a series of qualitative tests and modern analytical tools the importance of the treating media.

RESULTS

Our data demonstrates that these steps are necessary to remove the grease and scales in the raw material. While heating, microcracks appeared on the surface of the iron, which improved the reactivity with the herbal constituents in addition to incorporating nanostructured features. Further, the use of plant products facilitated the removal of Fe³⁺ present in the raw material by forming soluble complexes. The Fe²⁺ present in the raw materials also forms an insoluble complex with the herbal constituents in the presence of UV radiation.

CONCLUSIONS

In conclusion, our data summarily suggest that the purification steps involved in the preparation of Lauha bhasma (iron ash) are critical.

Metabolic signatures imaged in cancer-induced cachexia

Cancer-induced cachexia is a complex and poorly understood life-threatening syndrome that is characterized by progressive weight loss due to metabolic alterations, depletion of lipid stores, and severe loss of skeletal muscle protein. Gaining the ability to noninvasively image the presence or onset of cachexia is important to better treat this condition, to improve the design and optimization of therapeutic strategies, and to detect the responses to such treatments. In this study, we employed noninvasive magnetic resonance spectroscopic imaging (MRSI) and [(18)F]fluoro-2-deoxy-D-glucose ((18)FDG) positron emission tomography (PET) to identify metabolic signatures typical of cachectic tumors, using this information to analyze the types and extents of metabolic changes induced by the onset of cachexia in normal tissues. Cachexia was confirmed by weight loss as well as analyses of muscle tissue and serum. In vivo, cachexia-inducing murine adenocarcinoma (MAC)16 tumors were characterized by higher total choline (tCho) and higher (18)FDG uptake than histologically similar noncachectic MAC13 tumors. A profound depletion of the lipid signal was observed in normal tissue of MAC16 tumor-bearing mice but not within the tumor tissue itself. High-resolution (1)H magnetic resonance spectroscopy (MRS) confirmed the high tCho level observed in cachectic tumors that occurred because of an increase of free choline and phosphocholine. Higher succinate and lower creatine levels were also detected in cachectic tumors. Taken together, these findings enhance our understanding of the effect of cancer on host organs and tissues as well as promote the development of noninvasive biomarkers for the presence of cachexia and identification of new therapeutic targets.

Molecular and functional imaging of invasion and metastasis: windows into the metastatic cascade

The ability of cancer cells to invade, metastasize, and form distant colonies, is one of the key characteristics that confers lethality to cancer. Metastatic cancer cells typically become refractory to treatment. The metastatic cascade is a multi-step process that is governed by events within the cancer cell, the tumor microenvironment, and the distant environments that are invaded and colonized by the cancer cells. Noninvasive imaging techniques are facilitating a close examination of the stepwise journey of the cancer cell from the primary tumor to the distant metastatic site. Here we have discussed the metastatic process, and how molecular and functional imaging of cancer are providing new insights into the metastatic cascade that can be exploited for treatment of metastatic disease.

Abstract 2654: 5-Fluorouracil increases and decreases proteins involved in oncogenic pathways

Cancer cells are remarkably adaptive to treatments. 5-Fluorouracil, 5-FU, is a pyrimidine analogue, that is widely used for treatment of solid tumors1. It interferes with nucleoside metabolism and is incorporated into RNA and DNA, leading to cell death1. Its use, however, has been associated with increased cyclooxygenase-2 (COX-2) levels in breast, ovarian, esophageal, and colon cancers2 that could lead to the emergence of a more aggressive phenotype3. Here we have determined the effect of 5-FU in the expression of oncogenic molecules that are involved in phospholipid metabolism (choline kinase (Chk) and phospholipase D1 (PLD1)), inflammation (cyclooxygenase (COX)-2), and hypoxia response (hypoxia inducible factor (HIF)-1α) in order to facilitate a rational therapeutic design. Two triple negative breast cancer cell lines, MDA-MB-231 and SUM-149, were investigated. Cells were treated with 5-FU at various concentrations (1-25 μg/mL) and protein levels were examined at 24 and 48 hrs post treatment. Both HIF-1α and PLD1 levels decreased in a dose dependent manner following 5-FU treatment. In contrast, COX-2 level increased in response to 5-FU treatment together with an increase in Chk. Increased expressions of HIF-1α, PLD1, COX-2, and Chk have been associated with increased invasion and metastasis3-6. Our data suggest that in addition to its ability to interfere with DNA/RNA synthesis, 5-FU inhibits HIF-1α and PLD1 but increases the expression of two enzymes associated with invasive metastatic cancers. Importantly, while the mechanism by which 5-FU elevates COX-2 and Chk levels in these cancer cells remains to be investigated, these results provide a molecular basis for the combinational treatment of 5-FU with COX-2 and/or Chk inhibitors in cancer therapy.

References

(1) Arias J. Molecules, 2008.

(2) Mercer S.J., et al. Anticancer Drugs, 2005.

(3) Stasinopoulos I, et al. Neoplasia, 2008.

(4) Pai J.K., et al. Anticancer Drug Des, 1994.

(5) Shah T., et al. NMR Biomed, 2010.

(6) Lu X and Kang Y. Clin Cancer Res, 2010

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2654. doi:10.1158/1538-7445.AM2011-2654

Abstract 980: Downregulation of choline kinase does not affect endothelial cell proliferation

Elevated phosphocholine (PC) and high choline kinase (Chk) expression are typically observed in cancer. Chk, the enzyme that converts choline (Cho) to PC, is being evaluated as a novel target in cancer treatment using pharmacological and molecular inhibition. We have previously shown that both transient transfection and stable expression of siRNA (siRNA-chk) and shRNA against choline kinase-α (Chk) significantly reduced proliferation in breast cancer cells [1] and tumors [2]. The downregulation of Chk in nonmalignant MCF-12A cells resulted in an almost negligible effect on PC and proliferation [3]. Since endothelial cells are a key component of vasculature and are exposed to agents that are delivered systemically, it is important to determine the effect of Chk on endothelial cells in normal and tumor tissue. We have examined the proliferation and PC levels of human umbilical vein endothelial cells (HUVEC) after transient siRNA-chk transfection and compared the results with human breast cancer cells (MDA-MB-231).

MDA-MB-231 and HUVEC were used in this study. Cells were transiently transfected with 100 nM siRNA-chk for 48 hours using DhamaFECT. Cells were harvested to determine protein and mRNA levels at 48 hour post-transfection. Quantitative real-time PCR (q-RT-PCR) was performed to determine mRNA level using iQ SYBR Green Supermix and gene-specific primers in the iCycler real-time PCR detection system. Fully relaxed 1H MR spectra of water-soluble cell extracts were acquired on a Bruker Avance 500 MR spectrometer. PC level was quantified as mM using integrals of around 3.225 ppm signal in the 1H NMR spectra relative to cell number, cell volume (MDA-MB-231: 2050 µm3 and HUVEC: 4530 µm3), and an internal concentration standard. To exam the prolifelation/viability, cells were transfected with siRNA for 48 hours, changed to culture medium and cultured another 3 days, following which an MTS assay was performed.

After siRNA-chk transfection, Chk mRNA levels of MDA-MB-231 and HUVEC were comparable. Basal levels of Chk mRNA and Chk protein in HUVEC were low to start with, and it was difficult to downregulate Chk in HUVEC further. Immunoblot analysis showed significant downregulation of Chk protein in MDA-MB-231, and downregulation to a lesser extent in HUVEC after transfection of siRNA-chk. MTS assay result showed no significant reduction of proliferation in HUVEC after siRNA-chk transfection, while MDA-MB-231 showed a significant reduction of proliferation. The level of PC in HUVEC was about one tenth compared to MDA-MB-231. PC level was significantly reduced in MDA-MB-231 after siRNA-chk transfection but there was about 10% reduction in HUVEC. These data suggest that Chk inhibition will not affect endothelial cells during systemic administration, nor will it affect tumor vasculature.

[1] Glunde K et al, Cancer Res, 65, (2005); [2] Krishnamachary B et al, Cancer Res, 69, (2009); [3] Mori N et al, Cancer Res, 67, (2007).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 980. doi:10.1158/1538-7445.AM2011-980

Expression of DDX3 is directly modulated by hypoxia inducible factor-1 alpha in breast epithelial cells

DEAD box protein, DDX3, is aberrantly expressed in breast cancer cells ranging from weakly invasive to aggressive phenotypes and functions as an important regulator of cancer cell growth and survival. Here, we demonstrate that hypoxia inducible factor-1α is a transcriptional activator of DDX3 in breast cancer cells. Within the promoter region of the human DDX3 gene, we identified three putative hypoxia inducible factor-1 responsive elements. By luciferase reporter assays in combination with mutated hypoxia inducible factor-1 responsive elements, we determined that the hypoxia inducible factor-1 responsive element at position -153 relative to the translation start site is essential for transcriptional activation of DDX3 under hypoxic conditions. We also demonstrated that hypoxia inducible factor-1 binds to the DDX3 promoter and that the binding is specific, as revealed by siRNA against hypoxia inducible factor-1 and chromatin immunoprecipitation assays. Thus, the activation of DDX3 expression during hypoxia is due to the direct binding of hypoxia inducible factor-1 to hypoxia responsive elements in the DDX3 promoter. In addition, we observed a significant overlap in the protein expression pattern of hypoxia inducible factor-1α and DDX3 in MDA-MB-231 xenograft tumors. Taken together, our results demonstrate, for the first time, the role of DDX3 as a hypoxia-inducible gene that exhibits enhanced expression through the interaction of hypoxia inducible factor-1 with hypoxia inducible factor-1 responsive elements in its promoter region.

Abstract 46: Interdependence of choline kinase and phospholipase D in human breast cancer cells

One hallmark of cancer is an increase of cellular phosphocholine (PC) and total choline-containing compounds (tCho), which are closely related to malignant transformation, invasion and metastasis. Enzymes in choline metabolism present attractive targets that can be exploited for treatment. Choline kinase (Chk) is a cytosolic enzyme that catalyzes the phosphorylation of choline (Cho) to phosphocholine (PC) by using ATP in the presence of magnesium. Over-expression of Chk-α has been observed in breast, prostate and lung cancers, making it an obvious choice for targeting. Down-regulation of Chk-α results in a significant reduction of cell proliferation and increased differentiation in highly invasive MDA-MB-231 human breast cancer cells after siRNA-Chk transfection. Another potential target is phosphatidylcholine-specific phospholipase D (PC-PLD). Two mammalian isoforms of PLD, PLD1 and PLD2 have currently been identified. PLD1 is activated by G proteins such as ARF, Rho and Rac. Elevated PLD1 has been reported in gastric, renal, colon and breast carcinoma.

We characterized the expression of PLD1 in metastatic MDA-MB-231 cells, poorly metastatic MCF-7 cells, and nonmalignant MCF-12A cells and used siRNA to transiently down-regulate PLD1 and Chk-α in MDA-MB-231 and MCF-7 cells. Forty-eight hours post-transfection cells were harvested for protein and RNA. To determine the effective knock-down of Chk-α or PLD1, about 30µg of protein was resolved on 7.5% acrylamide gel, transferred to nitrocellulose membrane and probed with antibody specific to either Chk-α or PLD1. The effects of Chk-α downregulation on PLD1 expression and the effects of PLD1 downregulation on Chk-α expression were determined by western blots, and the message was quantified with q-RT-PCR. Downregulation of Chk resulted in an increase of PLD1 in MDA-MB-231 cells stably expressing shRNA against Chk or transiently transfected with Chk siRNA. Similar data were obtained for MCF-7 cells. PLD1 levels were highest in the metastatic MDA-MB-231 cells. Effective downregulation of PLD1 was achieved with transient PLD1 siRNA transfection, which resulted in an increase of Chk-α in these cells. These data demonstrate the adaptability of cancer cells, the interdependence of Chk-α and PLD1, and the importance of multiple targeting to eliminate any adaptive compensatory effects that would allow cancer cells to survive. This work was supported by NIH P50 CA103175.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 46.

Abstract 652: Magnetic resonance spectroscopy detects silencing of the novel anticancer target GDPD5 in human breast cancer cells

Altered choline phospholipid metabolism in breast cancers provides multiple targets for anticancer therapy. Malignant transformation of breast cancer cells results in a switch from high glycerophosphocholine (GPC) and low phosphocholine (PC) to low GPC and high PC. Glycerophosphocholine phosphodiesterase (E.C. 3.1.4.2; GPC-PDE) catalyzes the degradation of GPC to Cho and glycerol-3-phosphate. The GPC-PDE gene(s) responsible for the low GPC concentration in breast cancer cells have not yet been identified. Glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) is a GPC-PDE that is rapidly inhibited by NaCl and urea (NaCl/urea) in renal cells, and may be a candidate gene for GPC-PDE in breast cancer cells. We chemically inhibited GPC-PDE with NaCl/urea in nonmalignant MCF-12A, and malignant MCF-7 and MDA-MB-231 breast epithelial cell lines. We stably downregulated GDPD5 using short hairpin RNA against GDPD5 (GDPD5-shRNA) delivered by lentiviral transduction in MCF-7 breast cancer cells. Fully relaxed high-resolution 1H magnetic resonance spectroscopy (MRS) of cell extracts was performed on Bruker Avance 500 MR Spectrometer to quantify metabolites. Cell viability/proliferation was measured by WST-1 proliferation assay. Quantitative RT-PCR (qRT-PCR) detected significantly higher GDPD5 mRNA levels compared to the mRNA levels of GDPD1, 2, 3, and 4 in the respective cell line for MCF-12A, MCF-7, and MDA-MB-231 cells. GDPD5 levels were significantly higher in MDA-MB-231 compared to MCF-7 and MCF-12A cells. MRS metabolite quantification demonstrated that exposure of MCF-12A, MCF-7, and MDA-MB-231 cells to NaCl/urea (n=3), as well as transduction with GDPD5-shRNA in MCF-7 cells (n=2), significantly increased GPC and decreased PC, resulting in a decreased [PC]/[GPC] ratio. An increased [PC]/[GPC] ratio is associated with increased malignancy in breast cancer cell lines. We observed a switch from low GPC and high PC to high GPC and low PC following NaCl/urea treatment and following GDPD5-shRNA transduction. GDPD5 inhibition by NaCl/urea significantly decreased cell proliferation/viability in MCF-12A, MCF-7, and MDA-MB-231 cells. Inhibiting or down-regulating GDPD5 altered the choline phospholipid metabolite profile of breast cancer cells toward a less malignant metabolic profile. GDPD5 is at least partially responsible for the decreased GPC levels in breast cancer cells, as indicated by high GDPD5 mRNA and low GPC metabolite levels in MDA-MB-231 cells. Decreased proliferation detected upon GDPD5 inhibition with NaCl/urea further corroborated the importance of GPDP5 in breast cancer. These results indicate that GDPD5 may provide a future target for anticancer therapy. MRS could be used to monitor the GPC increase following downregulation of GDPD5 by RNA interference in such future therapies. This work was supported by NIH R01 CA134695 (to K.G.).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 652.

Abstract 451: HIF-1 alpha silencing in MDA-MB-231 human breast cancer cells alters choline phospholipid metabolism

Hypoxia-inducible factor-1 (HIF-1) over-expression has been associated with an increased patient mortality rate in many cancer types including breast cancer. Suppression of HIF-1 gene expression has been shown to inhibit tumor growth. Here we have studied the effect of HIF-1 silencing on the metabolism of MDA-MB-231 cells using a magnetic resonance (MR)- compatible cell perfusion assay. Previous studies have identified choline kinase (Chk), the enzyme that converts choline to phosphocholine (PC), and the resulting increase of PC and total choline (tCho) as markers of an aggressive phenotype. We found that HIF-1 silencing resulted in significantly reduced Chk expression together with reduced tCho and PC, compared to parental cells.

The sequence for shRNA against HIF-1α was cloned into a lentivirus vector with a green fluorescent protein (GFP) reporter construct (pRRL-pGK-GFP). Viral supernatant preparation and transduction of MDA-MB-231 breast cancer cells was performed following standard protocol. Transduced cells were validated for HIF-1α knock-down by western blots and by quantitative real-time polymerase chain reaction (q RT-PCR). Cell perfusion studies were performed using an MR-compatible perfusion assay to determine intracellular levels of metabolites using 1H and 31P MR spectroscopy (MRS). Experiments were performed in triplicates. The Mann Whitney-U test was used to determine statistical significance (p &lt;0.05).

HIF-1α protein expression increased following treatment with 200μM of the hypoxia mimetic CoCl2 in parental MDA-MB-231 cells but not in cells transduced with HIF-1α shRNA. Reduced expression of Chk in HIF-1α silenced cells was observed following CoCl2 treatment, while its expression was induced in parental cells. Quantitative data from 1H and 31P MRS showed significantly reduced levels of tCho (p &lt;0.05) and PC (p &lt; 0.01) in HIF-1α silenced cells compared to parental MDA-MB-231 cells, confirming that silencing of HIF-1α reduced levels of choline containing metabolites by reducing Chk expression. We previously observed that Chk is up regulated under hypoxia and have established a HIF-1 binding site on the Chk promoter. The reduction of choline metabolites in HIF-1α silenced cells further confirms the role of HIF-1α in the regulation of Chk. The reduction of Chk, total choline and PC levels in HIF-1α silenced cells are also typical of a less aggressive metabolic phenotype.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 451.

Abstract 4172: Multi-parametric characterization of an experimental model of cancer cachexia

Cachexia is a complex syndrome that is characterized by a massive loss of adipose tissue and skeletal mass. It is encountered in up to 50% of cancer patients and accounts for more than 20% of cancer related deaths. Currently, there is no known cure for cachexia, since mechanisms underlying its manifestation are not defined clearly enough to design effective therapeutic strategies. Here we have used magnetic resonance imaging (MRI) to characterize the vascular properties of cachectic vs. non-cachectic tumors. We have also analyzed the glucose metabolism of these tumors by using [18F]fluorodeoxyglucose (FDG) with positron emission tomography (PET). These studies will provide further insight into the cachectic phenotype that can be used to design treatments to arrest or reverse this condition. We used cachectic (MAC16) and non-cachectic (MAC13) murine colon adenocarcinoma tumors. The cell lines, originally from Dr. Tisdale's laboratory, were obtained from Dr. Sidransky with Dr. Tisdale's permission. Approximately 2 × 106 cells were inoculated in the flank of male SCID mice. MRI studies were performed on a 4.7T Bruker Avance spectrometer. Mice were anesthetized with an i.p. injection of ketamine and acepromazine. For vascular imaging, the tail vein was catheterized before placing the animal in the spectrometer. Multislice relaxation rate maps were obtained by a saturation recovery method combined with fast T1 SNAPSHOT-FLASH imaging. An M0 map with a recovery delay of 7 s was acquired from four 1 mm thick slices through the tumor followed by corresponding images obtained with three relaxation delays (100 ms, 500 ms, and 1 s). The T1 maps were obtained before i.v. injection of albumin-GdDTPA and repeated over a 21 minute period. For PET imaging, mice fasted overnight were injected with 0.2 mCi of FDG. At 60 min post injection, a 15 min static image was acquired over the tumors. Images were decay corrected and reconstructed using 2D OSEM. Cachectic MAC16 tumors induced extensive weight loss, unlike the non-cachectic MAC13 tumors. The difference in the weight of mice became significant within 2 weeks after inoculation. Mice with comparable tumor volumes were imaged 3 to 4 weeks after inoculation. While vascular volumes were not significantly different between the two groups, we did observe significantly lower permeability in the cachectic tumors. Consistent with the MRI data we found significantly lower levels of VEGF mRNA in quantitative-RT-PCR of tumor extracts of MAC16 tumors compared to MAC13 tumors but not in MAC16 cells compared to MAC13 cells. FDG PET imaging revealed increased glycolytic activity in a cachectic MAC16 tumor compared to a non-cachectic MAC13 tumor. These studies are part of our ongoing work to obtain a comprehensive characterization of the cachectic phenotype using noninvasive multi-modality imaging that will allow us to detect cancer-induced cachexia and identify new targets to prevent or reverse this condition.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4172.

Hypoxia inducible-factor1alpha regulates the metabolic shift of pulmonary hypertensive endothelial cells

Severe pulmonary hypertension is irreversible and often fatal. Abnormal proliferation and resistance to apoptosis of endothelial cells (ECs) and hypertrophy of smooth muscle cells in this disease are linked to decreased mitochondria and preferential energy generation by glycolysis. We hypothesized this metabolic shift of pulmonary hypertensive ECs is due to greater hypoxia inducible-factor1alpha (HIF-1alpha) expression caused by low levels of nitric oxide combined with low superoxide dismutase activity. We show that cultured ECs from patients with idiopathic pulmonary arterial hypertension (IPAH-ECs) have greater HIF-1alpha expression and transcriptional activity than controls under normoxia or hypoxia, and pulmonary arteries from affected patients have increased expression of HIF-1alpha and its target carbonic anhydrase IX. Decreased expression of manganese superoxide dismutase (MnSOD) in IPAH-ECs paralleled increased HIF-1alpha levels and small interfering (SI) RNA knockdown of MnSOD, but not of the copper-zinc SOD, increased HIF-1 protein expression and hypoxia response element (HRE)-driven luciferase activity in normoxic ECs. MnSOD siRNA also reduced nitric oxide production in supernatants of IPAH-ECs. Conversely, low levels of a nitric oxide donor reduced HIF-1alpha expression in normoxic IPAH-ECs. Finally, mitochondria numbers increased in IPAH-ECs with knockdown of HIF-1alpha. These findings indicate that alterations of nitric oxide and MnSOD contribute to pathological HIF-1alpha expression and account for lower numbers of mitochondria in IPAH-ECs.

Noninvasive detection of lentiviral-mediated choline kinase targeting in a human breast cancer xenograft

Elevated phosphocholine (PC) and total choline (tCho) metabolites are widely established characteristics of most cancer cells, including breast cancer. Effective silencing of choline kinase (chk), the enzyme that converts choline to PC, is associated with reduced tumor growth. The functional importance and down-regulation of chk using RNA interference has been previously established. Here, we report on the preclinical evaluation of lentiviral vector-mediated down-regulation of chk using short hairpin RNA (shRNA) in established tumors derived from human breast cancer cells. Concentrated lentivirus expressing shRNA against chk was injected i.v. in the tail vein of MDA-MB-231 tumor-bearing female severe combined immunodeficient mice. Transduction efficiency in cells and tumors in vivo was assessed optically by enhanced green fluorescent protein expression and additionally from chk mRNA and protein levels. An 80% reduction in chk mRNA and protein was achieved following approximately 90% transduction efficiency in cells. After transduction with chk-shRNA, (1)H magnetic resonance spectroscopy (MRS) of cell and tumor extracts showed decreases in PC and tCho levels (P < 0.01 and 0.05, respectively) in comparison with controls. PC levels were monitored noninvasively by (31)P MRS in tumors and by (1)H MRS in cell and tumor tissue extracts. Noninvasive (31)P MR spectra of chk-shRNA-transduced tumors in vivo showed lower PC and phosphomonoester levels that were associated with reduced tumor growth and proliferation. This study shows the use of lentiviral vectors to target chk in a human breast cancer xenograft and noninvasive MRS detection of this targeting.

Hypoxia-induced human endonuclease G expression suppresses tumor growth in a xenograft model

We have developed a hypoxia-inducible gene therapy approach for the expression of the mature form of human endonuclease G to facilitate cell death in hypoxic regions of the tumor. The chimeric therapeutic gene is placed under the control of a hypoxia response element based promoter and contains a translocation motif linked in frame to an oxygen-dependent degradation domain and the endonuclease G gene. Transient expression of the chimeric therapeutic gene in breast and prostate cancer cell lines resulted in efficient cell death under hypoxia-mimetic conditions. Stable MDA-MB-435 cells expressing the chimeric therapeutic gene under 1% O2 showed an increase in stable HIF-1alpha protein levels and synthesis of the endonuclease G protein in a time-dependent manner. In normoxic conditions, these stable transgenic cells exhibited no change in growth rate, invasion and motility when compared to parental cells. Moreover, xenografts generated using the transgenic cells exhibited highly significant suppression of tumor growth in a preclinical cancer model compared to the parental cell line. Thus, the hypoxia-modulated endonuclease G expression has the potential to be used as a gene-based-therapy system to kill malignant cells within hypoxic regions of tumors.

HIF-1 inhibits mitochondrial biogenesis and cellular respiration in VHL-deficient renal cell carcinoma by repression of C-MYC activity

Many cancer cells are characterized by increased glycolysis and decreased respiration, even under aerobic conditions. The molecular mechanisms underlying this metabolic reprogramming are unclear. Here we show that hypoxia-inducible factor 1 (HIF-1) negatively regulates mitochondrial biogenesis and O(2) consumption in renal carcinoma cells lacking the von Hippel-Lindau tumor suppressor (VHL). HIF-1 mediates these effects by inhibiting C-MYC activity via two mechanisms. First, HIF-1 binds to and activates transcription of the MXI1 gene, which encodes a repressor of C-MYC transcriptional activity. Second, HIF-1 promotes MXI-1-independent, proteasome-dependent degradation of C-MYC. We demonstrate that transcription of the gene encoding the coactivator PGC-1beta is C-MYC dependent and that loss of PGC-1beta expression is a major factor contributing to reduced respiration in VHL-deficient renal carcinoma cells.

Analysis of hypoxia-inducible factor 1alpha expression and its effects on invasion and metastasis

Hypoxia-inducible factor 1 (HIF-1) plays an important role in human cancer cell invasion and metastasis. As a result, overexpression of the HIF-1alpha subunit in biopsy specimens is associated with increased patient mortality in several common cancers, including breast adenocarcinoma and oropharyngeal squamous cell carcinoma. Here, we describe methods for immunohistochemical detection of HIF-1alpha in tumor biopsy sections and ex vivo assays for analyzing the effects of hypoxia and HIF-1 on cancer cell invasiveness and cell-cell adhesion.

Spontaneous transformation of cultured mouse bone marrow-derived stromal cells

Bone marrow-derived stromal cells have engendered interest because of their therapeutic potential for promoting tissue vascularization and repair. When mononuclear cells isolated from mouse bone marrow were cultured in DMEM supplemented with 10% fetal bovine serum, cell populations arose that showed rapid proliferation and loss of contact inhibition. These cells formed invasive soft tissue sarcomas after i.m. injection into nude or scid mice. I.v. injection resulted in the formation of tumor foci in the lungs. The tumors were transplantable into syngeneic immunocompetent mice. Direct injection of cultured cells into immunocompetent mice also resulted in tumor formation. Karyotype analysis showed that increased chromosome number and multiple Robertsonian translocations occurred at passage 3 coincident with the loss of contact inhibition. The remarkably rapid malignant transformation of cultured mouse bone marrow cells may have important implications for ongoing clinical trials of cell therapy and for models of oncogenesis.