Adipose-Tumor Crosstalk contributes to CXCL5 Mediated Immune Evasion in PDAC

Background

CXCR1/2 inhibitors are being implemented with immunotherapies in PDAC clinical trials. Cytokines responsible for stimulating these receptors include CXCL ligands, typically secreted by activated immune cells, fibroblasts, and even adipocytes. Obesity has been linked to poor patient outcome and altered anti-tumor immunity. Adipose-derived cytokines and chemokines have been implicated as potential drivers of tumor cell immune evasion, suggesting a possibility of susceptibility to targeting specifically in the context of obesity.

Methods

RNA-sequencing of human PDAC cell lines was used to assess differential influences on the cancer cell transcriptome after treatment with conditioned media from peri-pancreatic adipose tissue of lean and obese PDAC patients. The adipose-induced secretome of PDAC cells was then assessed by cytokine arrays and ELISAs. Lentiviral transduction and CRISPR-Cas9 was used to knock out CXCL5 from a murine PDAC cell line for orthotopic tumor studies in diet-induced obese, syngeneic mice. Flow cytometry was used to define the immune profiles of tumors. Anti-PD-1 immune checkpoint blockade therapy was administered to alleviate T cell exhaustion and invoke an immune response, while the mice were monitored at endpoint for differences in tumor size.

Results

The chemokine CXCL5 was secreted in response to stimulation of PDAC cells with human adipose conditioned media (hAT-CM). PDAC CXCL5 secretion was induced by either IL-1β or TNF, but neutralization of both was required to limit secretion. Ablation of CXCL5 from tumors promoted an immune phenotype susceptible to PD-1 inhibitor therapy. While application of anti-PD-1 treatment to control tumors failed to alter tumor growth, knockout CXCL5 tumors were diminished.

Conclusions

In summary, our findings show that known adipokines TNF and IL-1β can stimulate CXCL5 release from PDAC cells in vitro. In vivo , CXCL5 depletion alone is sufficient to promote T cell infiltration into tumors in an obese setting, but requires checkpoint blockade inhibition to alleviate tumor burden.

DATA AVAILABILITY STATEMENT

Raw and processed RNAseq data will be further described in the GEO accession database ( awaiting approval from GEO for PRJ number ). Additional raw data is included in the supplemental material and available upon reasonable request.

WHAT IS ALREADY KNOWN ON THIS TOPIC

Obesity is linked to a worsened patient outcome and immunogenic tumor profile in PDAC. CXCR1/2 inhibitors have begun to be implemented in combination with immune checkpoint blockade therapies to promote T cell infiltration under the premise of targeting the myeloid rich TME.

WHAT THIS STUDY ADDS

Using in vitro/ex vivo cell and tissue culture-based assays with in vivo mouse models we have identified that adipose derived IL-1β and TNF can promote tumor secretion of CXCL5 which acts as a critical deterrent to CD8 T cell tumor infiltration, but loss of CXCL5 also leads to a more immune suppressive myeloid profile.

HOW THIS STUDY MIGHT AFFECT RESEARCH PRACTICE OR POLICY

This study highlights a mechanism and emphasizes the efficacy of single CXCR1/2 ligand targeting that could be beneficial to overcoming tumor immune-evasion even in the obese PDAC patient population.

Combined MEK and STAT3 Inhibition Uncovers Stromal Plasticity by Enriching for Cancer-Associated Fibroblasts With Mesenchymal Stem Cell-Like Features to Overcome Immunotherapy Resistance in Pancreatic Cancer

BACKGROUND & AIMS

We have shown that reciprocally activated rat sarcoma (RAS)/mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) and Janus kinase/signal transducer and activator of transcription 3 (STAT3) pathways mediate therapeutic resistance in pancreatic ductal adenocarcinoma (PDAC), while combined MEK and STAT3 inhibition (MEKi+STAT3i) overcomes such resistance and alters stromal architecture. We now determine whether MEKi+STAT3i reprograms the cancer-associated fibroblast (CAF) and immune microenvironment to overcome resistance to immune checkpoint inhibition in PDAC.

METHODS

CAF and immune cell transcriptomes in MEKi (trametinib)+STAT3i (ruxolitinib)-treated vs vehicle-treated Ptf1aCre/+;LSL-KrasG12D/+;Tgfbr2flox/flox (PKT) tumors were examined via single-cell RNA sequencing (scRNAseq). Clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeats associated protein 9 silencing of CAF-restricted Map2k1/Mek1 or Stat3, or both, enabled interrogation of CAF-dependent effects on immunologic remodeling in orthotopic models. Tumor growth, survival, and immune profiling via mass cytometry by time-of-flight were examined in PKT mice treated with vehicle, anti-programmed cell death protein 1 (PD-1) monotherapy, and MEKi+STAT3i combined with anti-PD1.

RESULTS

MEKi+STAT3i attenuates Il6/Cxcl1-expressing proinflammatory and Lrrc15-expressing myofibroblastic CAF phenotypes while enriching for Ly6a/Cd34-expressing CAFs exhibiting mesenchymal stem cell-like features via scRNAseq in PKT mice. This CAF plasticity is associated with M2-to-M1 reprogramming of tumor-associated macrophages, and enhanced trafficking of cluster of differentiation 8+ T cells, which exhibit distinct effector transcriptional programs. These MEKi+STAT3i-induced effects appear CAF-dependent, because CAF-restricted Mek1/Stat3 silencing mitigates inflammatory-CAF polarization and myeloid infiltration in vivo. Addition of MEKi+STAT3i to PD-1 blockade not only dramatically improves antitumor responses and survival in PKT mice but also augments recruitment of activated/memory T cells while improving their degranulating and cytotoxic capacity compared with anti-PD-1 monotherapy. Importantly, treatment of a patient who has chemotherapy-refractory metastatic PDAC with MEKi (trametinib), STAT3i (ruxolitinib), and PD-1 inhibitor (nivolumab) yielded clinical benefit.

CONCLUSIONS

Combined MEKi+STAT3i mitigates stromal inflammation and enriches for CAF phenotypes with mesenchymal stem cell-like properties to overcome immunotherapy resistance in PDAC.

Abstract C060: Adipose-tumor crosstalk alters tumor immune profile by promoting PDAC CXCL5 secretion

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death in the US, due to late detection and limited therapeutic options. While the main cause of PDAC remains unknown, obesity has been shown to be a major risk factor. However, the molecular mechanisms behind adipose-tumor crosstalk are still being elucidated. Therefore, understanding the crosstalk between adipose and PDAC is critical for improving therapeutic approaches. We hypothesize that factors secreted by the adipose tissue reprogram pancreatic cancer cells to drive tumor growth and anti-tumor immunity. We observed enhanced proliferation in cells treated with conditioned media made from adipose tissue collected from PDAC [MV1] patients. Subsequent analysis determined that PDAC cells also secrete high levels of CXCL5 in response to stimulation with adipose conditioned media. Pathway analysis of RNA-sequencing data from conditioned-media-treated human PDAC cell lines implicated IL-1β and TNF-α as being involved in the resulting transcript changes. Using recombinant IL-1β, we stimulated CXCL5 secretion from multiple PDAC cell lines. Additionally, we found an enhanced secretion of IL-1β from obese adipose tissue compared to that from lean adipose and, using an anti-IL-1β blocking antibody we were able to partially depress the CXCL5 secretion from cells stimulated with adipose conditioned media. Because CXCL5 is a known neutrophil activating and attracting protein, we used CRISPR to engineer CXCL5 deficient murine PDAC cells. To determine the effect of tumor-derived CXCL5 on PDAC growth and immune recruitment, we orthotopically injected non-targeting-control and CXCL5-KO K8484 cells into wild-type, syngeneic, obese mice. While CXCL5-KO tumors displayed a similar size, we observed a significant change in the tumor immune profile. Despite an increase in the pro-tumorigenic monocytic myeloid derived suppressor cells (MDSCs), we found that the CXCL5-KO tumors exhibited a significantly enhanced CD8+ T cell infiltration. However, a high percentage of these CD8+ T cells were PD-1 positive, implicating an exhausted phenotype. Subsequently, we treated wildtype and CXCL5 deficient PDAC bearing obese mice with an anti-PD-1 antibody to promote T-cell re-activation, which resulted in a significantly reduced growth of the CXCL5 deficient tumors. In conclusion, obesity and adipose derived factors directly induce tumor cells to support immune suppression and drive PDAC progression.

Citation Format: R. McKinnon Walsh, Joseph Ambrose, Bailey A. Bye, Austin E. Eades, Jarrid L. Jack, Mariana T. Ruckert, Appolinaire A. Olou, Fanuel Messaggio, Prabhakar Chalise, Dong Pei, Michael N. VanSaun. Adipose-tumor crosstalk alters tumor immune profile by promoting PDAC CXCL5 secretion [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C060.

Synthetic adiponectin-receptor agonist, AdipoRon, induces glycolytic dependence in pancreatic cancer cells

Obesity creates a localized inflammatory reaction in the adipose, altering secretion of adipocyte-derived factors that contribute to pathologies including cancer. We have previously shown that adiponectin inhibits pancreatic cancer by antagonizing leptin-induced STAT3 activation. Yet, the effects of adiponectin on pancreatic cancer cell metabolism have not been addressed. In these studies, we have uncovered a novel metabolic function for the synthetic adiponectin-receptor agonist, AdipoRon. Treatment of PDAC cells with AdipoRon led to mitochondrial uncoupling and loss of ATP production. Concomitantly, AdipoRon-treated cells increased glucose uptake and utilization. This metabolic switch further correlated with AMPK mediated inhibition of the prolipogenic factor acetyl coenzyme A carboxylase 1 (ACC1), which is known to initiate fatty acid catabolism. Yet, measurements of fatty acid oxidation failed to detect any alteration in response to AdipoRon treatment, suggesting a deficiency for compensation. Additional disruption of glycolytic dependence, using either a glycolysis inhibitor or low-glucose conditions, demonstrated an impairment of growth and survival of all pancreatic cancer cell lines tested. Collectively, these studies provide evidence that pancreatic cancer cells utilize metabolic plasticity to upregulate glycolysis in order to adapt to suppression of oxidative phosphorylation in the presence of AdipoRon.

Combined Blockade of MEK and CDK4/6 Pathways Induces Senescence to Improve Survival in Pancreatic Ductal Adenocarcinoma

Activating KRAS mutations, a defining feature of pancreatic ductal adenocarcinoma (PDAC), promote tumor growth in part through the activation of cyclin-dependent kinases (CDK) that induce cell-cycle progression. p16INK4a (p16), encoded by the gene CDKN2A, is a potent inhibitor of CDK4/6 and serves as a critical checkpoint of cell proliferation. Mutations in and subsequent loss of the p16 gene occur in PDAC at a rate higher than that reported in any other tumor type and results in Rb inactivation and unrestricted cellular growth. Therefore, strategies targeting downstream RAS pathway effectors combined with CDK4/6 inhibition (CDK4/6i) may have the potential to improve outcomes in this disease. Herein, we show that expression of p16 is markedly reduced in PDAC tumors compared with normal pancreatic or pre-neoplastic tissues. Combined MEK inhibition (MEKi) and CDK4/6i results in sustained downregulation of both ERK and Rb phosphorylation and a significant reduction in cell proliferation compared with monotherapy in human PDAC cells. MEKi with CDK4/6i reduces tumor cell proliferation by promoting senescence-mediated growth arrest, independent of apoptosis in vitro We show that combined MEKi and CDK4/6i treatment attenuates tumor growth in xenograft models of PDAC and improves overall survival over 200% compared with treatment with vehicle or individual agents alone in Ptf1acre/+ ;LSL-KRASG12D/+ ;Tgfbr2flox/flox (PKT) mice. Histologic analysis of PKT tumor lysates reveal a significant decrease in markers of cell proliferation and an increase in senescence-associated markers without any significant change in apoptosis. These results demonstrate that combined targeting of both MEK and CDK4/6 represents a novel therapeutic strategy to synergistically reduce tumor growth through induction of cellular senescence in PDAC.

Metabolomic changes in human adipose tissue derived products following non-enzymatic microfacturing

OBJECTIVE

In this study, we evaluated the metabolomic profiling of cryopreserved Lipogems® tissue products and the initial lipoaspirates before microfracturing, to determine altered metabolites that could result from the non-enzymatic processing or the cryopreservation method.

MATERIALS AND METHODS

Human Lipoaspirate samples (n=10) were divided in two aliquots, of which one was non-processed and the other was processed by Lipogems® device. Non-processed lipoaspirates and Lipogems® processed tissues were stored at -80°C fresh frozen (N=3 per group) or in the presence of 0.5 M dimethyl sulfoxide (DMSO) (N=7 per group). A global non-targeted metabolic profile on these samples was performed.

RESULTS

Differences were observed in carbohydrate and nucleotide metabolism. These alterations translated in long chain and polyunsaturated fatty acid levels and amino acid metabolites showed divergent trends. When Lipogems® and Lipoaspirate tissue products were cryopreserved with DMSO, amino acids tended to increase in Lipogems® product. However, in the absence of DMSO aminoacids and their catabolites, tended to decrease in Lipogems® fat tissue product.

CONCLUSIONS

Microfractured human adipose tissue has been shown to provide a more effective source of adult stromal cells compared to the initial lipoaspirated tissue material. These could be, according to our findings, due to the changes in the metabolic profile of lipoaspirate tissues products.

Tobacco Carcinogen-Induced Production of GM-CSF Activates CREB to Promote Pancreatic Cancer

Although smoking is a significant risk factor for pancreatic ductal adenocarcinoma (PDAC), the molecular mechanisms underlying PDAC development and progression in smokers are still unclear. Here, we show the role of cyclic AMP response element-binding protein (CREB) in the pathogenesis of smoking-induced PDAC. Smokers had significantly higher levels of activated CREB when compared with nonsmokers. Cell lines derived from normal pancreas and pancreatic intraepithelial neoplasm (PanIN) exhibited low baseline pCREB levels compared with PDAC cell lines. Furthermore, elevated CREB expression correlated with reduced survival in patients with PDAC. Depletion of CREB significantly reduced tumor burden after tobacco-specific nitrosamine 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) treatment, suggesting a CREB-dependent contribution to PDAC growth and progression in smokers. Conversely, NNK accelerated PanIN lesion and PDAC formation via GM-CSF-mediated activation of CREB in a PDAC mouse model. CREB inhibition (CREBi) in mice more effectively reduced primary tumor burden compared with control or GM-CSF blockade alone following NNK exposure. GM-CSF played a role in the recruitment of tumor-associated macrophages (TAM) and regulatory T cell (Treg) expansion and promotion, whereas CREBi significantly reduced TAM and Treg populations in NNK-exposed mice. Overall, these results suggest that NNK exposure leads to activation of CREB through GM-CSF, promoting inflammatory and Akt pathways. Direct inhibition of CREB, but not GM-CSF, effectively abrogates these effects and inhibits tumor progression, offering a viable therapeutic strategy for patients with PDAC.Significance: These findings identify GM-CSF-induced CREB as a driver of pancreatic cancer in smokers and demonstrate the therapeutic potential of targeting CREB to reduce PDAC tumor growth.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/21/6146/F1.large.jpg Cancer Res; 78(21); 6146-58. ©2018 AACR.

Inverse Correlation of STAT3 and MEK Signaling Mediates Resistance to RAS Pathway Inhibition in Pancreatic Cancer

Major contributors to therapeutic resistance in pancreatic ductal adenocarcinoma (PDAC) include Kras mutations, a dense desmoplastic stroma that prevents drug delivery to the tumor, and activation of redundant signaling pathways. We have previously identified a mechanistic rationale for targeting STAT3 signaling to overcome therapeutic resistance in PDAC. In this study, we investigate the molecular mechanisms underlying the heterogeneous response to STAT3 and RAS pathway inhibition in PDAC. Effects of JAK/STAT3 inhibition (STAT3i) or MEK inhibition (MEKi) were established in Ptf1a^cre/+; LSL-Kras^G12D/+ ; and Tgfbr2^flox/flox (PKT) mice and patient-derived xenografts (PDX). Amphiregulin (AREG) levels were determined in serum from human patients with PDAC, LSL-Kras^G12D/+;Trp53^R172H/+;Pdx1^Cre/+ (KPC), and PKT mice. MEKi/STAT3i-treated tumors were analyzed for integrity of the pancreas and the presence of cancer stem cells (CSC). We observed an inverse correlation between ERK and STAT3 phosphorylation. MEKi resulted in an immediate activation of STAT3, whereas STAT3i resulted in TACE-induced, AREG-dependent activation of EGFR and ERK. Combined MEKi/STAT3i sustained blockade of ERK, EGFR, and STAT3 signaling, overcoming resistance to individual MEKi or STAT3i. This combined inhibition attenuated tumor growth in PDX and increased survival of PKT mice while reducing serum AREG levels. Furthermore, MEKi/STAT3i altered the PDAC tumor microenvironment by depleting tumor fibrosis, maintaining pancreatic integrity, and downregulating CD44⁺ and CD133⁺ CSCs. These results demonstrate that resistance to MEKi is mediated through activation of STAT3, whereas TACE-AREG-EGFR-dependent activation of RAS pathway signaling confers resistance to STAT3 inhibition. Combined MEKi/STAT3i overcomes these resistances and provides a novel therapeutic strategy to target the RAS and STAT3 pathway in PDAC.Significance: This report describes an inverse correlation between MEK and STAT3 signaling as key mechanisms of resistance in PDAC and shows that combined inhibition of MEK and STAT3 overcomes this resistance and provides an improved therapeutic strategy to target the RAS pathway in PDAC.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/21/6235/F1.large.jpg Cancer Res; 78(21); 6235-46. ©2018 AACR.

Abstract 1249: Animal model in the prevention of alcoholic pancreatitis

Background: Alcohol abuse is a major risk factor for pancreatitis. Alcohol addiction-induced molecular pathogenesis of pancreatitis remains obscure, and no current effective treatment exists. Therefore, approaches to investigate pathogenesis, prevention and cellular mechanisms by which alcohol causes pancreatitis are necessary for establishing therapeutics. Our efforts demonstrate that alcohol induces activation of a major intracellular transcriptional factor, cyclic AMP response element-binding protein (CREB). We further investigated the functional role of CREB in alcohol-induced pathogenesis of pancreatitis using cellular and genetic mouse models of pancreas.

Materials and Methods: Human tissue microarrays were immunostained to determine the significance of pCREB expression among pancreatic tissues obtained from normal and chronic pancreatitis. Rat acinar cell line AR42J and mouse PSCs (mPSCs) were exposed to alcohol (50 mMol/L). Inducible Ptf1aCreERTM knockin mice and Ptf1aCreERTM;CREBfl/fl (iPC) mice were fed with Lieber Decarli diet alcohol or regular diet for 14 weeks with or without caerulein (50 µg/kg). Mice were then euthanized 24 hours after the last caerulein injection, and pancreas tissues were processed for morphometric analysis (necrosis, vacuolization, hemorrhage, edema and inflammation) and immunohistochemical analysis of amylase, trichrome blue, SMA, collagen 1, fibronectin and pCREB expression. To determine whether alcohol accelerated morbidity in mice, we evaluated pathogenesis of chronic pancreatitis by analyzing acinar atrophy and pancreatic fibrosis.

Results: Expression of pCREB was significantly higher (p <0.001) in chronic pancreatitis vs. normal patient tissues, confirming the role of activated CREB in pancreatitis. Activated CREB levels were very high in alcohol-fed Ptf1aCreERTM mice when compared with control diet-fed mice. Pancreatic sections from alcohol-fed mice challenged with caerulein revealed significantly higher score of acinar cell vacuolization and necrosis, inflammatory infiltrate and hemorrhage compared with minimal lesions in control diet-fed animals receiving caerulein. Pancreatic sections from alcohol-fed Ptf1aCreERTM animals showed higher score of histologic injury, extracellular matrix deposition, collagen deposition and increased pancreatic fibrosis when compared with control-fed mice. iPC mice showed decrease in the pathogenesis of chronic pancreatitis when compared to Ptf1aCreERTM mice with alcohol.

Conclusion: CREB is overexpressed in pancreatitis and alcohol activates CREB, which then drives pathogenesis of pancreatitis. Severity of pancreatitis in response to alcohol is diminished in the absence of CREB. Therefore, we conclude that targeting CREB represents a promising treatment for alcohol-induced pancreatitis.

Citation Format: Supriya Srinivasan, Tulasigeri Totiger, Michael VanSaun, Fanuel Messaggio, Chanjuan Shi, Austin Dosch, Eric Nestler, Nipun Merchant, Nagaraj Nagathihalli. Animal model in the prevention of alcoholic pancreatitis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1249.

Adiponectin receptor agonists inhibit leptin induced pSTAT3 and in vivo pancreatic tumor growth

Obesity is a significant risk factor for pancreatic cancer, harboring a chronic inflammatory condition characterized by dysregulation of the adipokines, leptin and adiponectin, that in turn alter oncogenic signaling pathways. We and others have shown that leptin promotes the proliferation and an invasive potential of pancreatic cancer cells through STAT3 mediated signaling. However, the role of adiponectin on the tumorigenicity of pancreatic cancer has not been elucidated. Adiponectin represents an important negative regulator of cytokines, which acts through two receptors, ADIPOR1 and ADIPOR2, to elicit pro-apoptotic, anti-inflammatory, and anti-angiogenic responses. We show that the level and expression of both adiponectin receptors are decreased in pancreatic tumors relative to normal pancreatic tissue. In vitro stimulation with adiponectin or a small molecule adiponectin receptor agonist, AdipoRon, increases apoptosis while inhibiting pancreatic cancer cell proliferation, colony formation, and anchorage independent growth. In addition, adiponectin receptor agonism inhibits leptin mediated STAT3 activation. In vivo, treatment of mice with AdipoRon inhibits orthotopic pancreatic tumor growth. These results demonstrate that adiponectin receptor activation is a key regulator of pancreatic cancer growth and AdipoRon provides a rational agent for the development of novel therapeutic strategies for pancreatic cancer.

Abstract 2802: High fat diet increases development of hepatocellular carcinoma in glycine N-methyltransferase deficient mice

Introduction: Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. HCC typically arises in patients with chronic liver disease or cirrhosis, yet it is increasingly associated with non-alcoholic fatty liver disease (NAFLD), specifically nonalcoholic steatohepatitis (NASH) in the absence of cirrhosis. NAFLD is associated with obesity, metabolic syndrome, and/or patients with type II diabetes. Our previous studies have shown that high fat diet induced hepatic steatosis increases proliferation of hepatocytes and the growth of malignant tumors in a murine model. Glycine N-MethylTransferase (GNMT) expression is lost in over 95% of HCC, and mice deficient in GNMT develop spontaneous HCC by 6 months of age. We hypothesized that GNMT deficient mice would have an increased susceptibility for the development and growth of HCC when a fed high fat diet.

Methods: Wildtype and GNMT deficient mice were placed on lean diet (LD, 13% calories from fat) or high fat diet (HFD, 42% calories from fat) at eight weeks of age. An initial cohort of mice were sacrificed after 3 months on diet (6 months of age) to assess for early tumor burden. A second cohort of mice was analyzed by magnetic resonance imaging (MRI) after 6 months on diet (9 months of age) and then sacrificed to assess for late stage disease. All mice were assessed for body weight, liver weight, pancreatic weight, and proliferative index (Ki67).

Results: GNMT deficient mice failed to gain weight when placed on HFD, which remained at levels equivalent to wildtype LD mice. At three months of age, wildtype mice on HFD had significantly enlarged livers due to hepatic steatosis. HFD fed GNMT deficient mouse livers were nearly 50% the size of wildtype livers and contained only minimal fatty deposits. Further, livers from HFD and LD fed GNMT mice were equivalent after 3 months, yet they were larger than wildtype mice fed LD. After six months on diet, MRI analysis showed significantly larger livers in HFD fed GNMT mice compared to LD fed GNMT mice due to extensive tumor burden. All wildtype mice lacked any tumors after six months regardless of diet. Histological analysis revealed a heightened cellular proliferation via Ki67 staining in GNMT deficient livers compared to wildtype livers. In comparison, GNMT silencing also occurs in pancreatic cancer, yet none of the GNMT deficient mice developed pancreatic tumors. However, small focal areas of pancreatitis were detected regardless of diet. Additionally, pancreatic weight was significantly decreased in HFD fed GNMT deficient mice compared the LD GNMT deficient mice.

Conclusions: While high fat diet did not induce obesity in GNMT deficient mice, it significantly increased cellular proliferation and primary tumor growth in the liver. Understanding dietary factors that impact the microenvironment of the liver and contribute to HCC development and progression is vital to finding new therapeutics for this malignancy.

Citation Format: Michael N. VanSaun, Alisha Mendonsa, Fanuel Messaggio, Nagaraj Nagathihalli, Lee Gorden. High fat diet increases development of hepatocellular carcinoma in glycine N-methyltransferase deficient mice [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 2802. doi:10.1158/1538-7445.AM2017-2802

Abstract B75: Targeting the immune-microenvironment with combined inhibition of MEK and STAT3 in a mouse model of pancreatic cancer

Introduction: Activating KRAS mutations are commonly found in PDAC and lead to constitutive downstream activation of MEK, which results in uncontrolled proliferation. We have previously shown that MEK inhibition results in activation of STAT3 signaling which confers drug resistance and continued cancer cell growth while combined STAT3 and MEK inhibition overcomes this resistance. Since STAT3 is a critical mediator of cytokine signaling and MEK is a mediator of cytokine production, we sought to determine the effects of MEK and STAT3 inhibition on the immune tumor microenvironment (TME). Tumor infiltrating immune/inflammatory cells, such as regulatory T cells (Tregs), myeloid –derived suppressor cells (MDSCs) and macrophages support tumor growth and contribute to therapeutic resistance. We hypothesized that combined MEK and STAT3 inhibition down regulates the suppressive immune infiltrates and promotes an anti-tumor microenvironment.

Experimental procedure: To understand the effect of MEK and/or STAT3 inhibition of PDAC cells, three dimensional spheroid cultures of PDAC cells (MiaPaCa-2, Panc-1, BxPC3) were prepared. Spheroid cultures were treated with inhibitors to MEK (AZD6244) and/or STAT3 (AZD1480) for 10 days. At the end of treatment, spheroids were quantified for size and metabolic activity. To determine in vivo effects, Ptf1a Cre/+ ; LSL-KrasG12D; Tgfbr2fl/fl (PKT) mice were treated with either vehicle, MEK inhibition, STAT3 inhibition, or the combination for 2 weeks. Post-treated pancreatic tissue was extracted, weighed, and examined for pancreatic integrity using immuno-histological and enzymatic analyses. Alternately, the pancreas and spleen were extracted from the mice, cells were isolated from the tissue, and subsequently labeled with antigens for macrophages (CD45, F4/80, CD86, CD80, CD206, CD204), myeloid cells (CD45, CD11b, Ly6g, Ly6c), and T cells (CD45, CD3e, CD4, CD8, CD25, FoxP3) before assessing population percentages by flow cytometric analysis.

Results: Treatment with MEK inhibition resulted in slightly reduced spheroid size and metabolic activity; however, combined MEK/STAT3 treatment led to a significant decrease in spheroid size as well as metabolic activity. In PKT mice, treatment with combined inhibitors for MEK and STAT3 resulted in the enhanced suppression of tumor formation compared to either agent alone. Histological analysis of combined MEK/STAT3 significantly inhibited tumor size, maintained a higher percentage of pancreatic integrity, displaying increased percentage of normal acini, reduced CK-19 staining, reduced collagen deposition and minimal alcian blue stain. Analysis of the tumor immune infiltrates revealed a significant reduction in the immunosuppressive/tumor promoting myeloid derived suppressor cell (MDSC) population (CD45+CD11b+Ly6g+Ly6c+) and regulatory T cell population (CD45+CD3e+CD4+CD25+FoxP3+) in the pancreas of mice treated with combined MEK/STAT3 inhibition compared to control mice or mice treated with single agents. Alternately, combined MEK/STAT3 inhibition promoted an increased neutrophil population (7AAD-CD11b+Ly6c+Ly6g-), but a decreased inflammatory M1 macrophage population (CD45+F4/80+CD80+CD86+).

Conclusions: Combined MEK/STAT3 inhibition downregulates the tumor promoting immune infiltrates resulting in dramatically reduced tumor burden and enhanced normal pancreatic tissue in a highly aggressive mouse model of pancreatic cancer.

Citation Format: Casey Roberts, Michael N. VanSaun, Purushottam Lamichhane, Fanuel Messaggio, Krisztina Kovacs, Supriya Srinivasan, Xizi Dai, Jennifer Barretta, Nagaraj Nagathihalli, Nipun B. Merchant.{Authors}. Targeting the immune-microenvironment with combined inhibition of MEK and STAT3 in a mouse model of pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B75.

Abstract B78: RAD51 sensitizes pancreatic cancer cells to AKT inhibition

Introduction: Cell survival after DNA damage relies on DNA repair processes to protect the integrity of the genome. The repair process involves DNA homologous recombination system that requires numerous factors including the recombinase RAD51 and BRCA2, which co-localize to replication centers within the damaged cell nucleus. The defective DNA repair mechanisms in cancer cells can be exploited for therapy, when abrogated DNA double-strand breaks (DSB) repair causes genomic instability and increase in cancer cell sensitivity to consequential cellular apoptosis. Targeted therapies are challenged by emergence of tumor cell resistance associated with downstream components of KRAS signaling pathways in pancreatic ductal adenocarcinoma (PDAC). It is, therefore, essential to develop novel therapeutic strategies to overcome chemoresistance. The PI3K/AKT pathway is activated in human PDAC and mouse models of KRAS-driven PDAC. We sought to determine the effects of RAD51 on therapeutic sensitivity and resistance to AKT inhibition.

Experimental procedure: RAD51 expression was determined in human pancreatic tissues from a tissue microarray (TMA) and analyzed for overall survival (OS). Cell lysates from mouse cell lines derived from the LSL-KrasG12D/+;Pdx1Cre/+ (PanIN) and LSL-KrasG12D/+; Trp53R172H/+;Pdx1Cre/+ (PDA and LMP) genetic mouse models of PDAC were immunoblotted for RAD51 expression. IC50 values of B02 (a RAD51 inhibitor) treatment in human PDAC cell lines were determined. Orthotopic tumors were generated with direct injections of luciferase-tagged PANC1 cells and were treated with B02. Bioluminescence imaging (BLI) was utilized to monitor orthotopic tumor growth and treatment response. Colony formation, spheroid generation size and metabolic activity, cell cycle analysis and apoptosis assays were performed in human PDAC cells treated with inhibitors for RAD51 (B02) and/or AKT (MK2206). PDA (express low RAD51) and LMP (express high RAD51) cell lines from mice were treated with B02 and/or MK2206 and analyzed for their colony forming ability. The in vitro sensitivities of BRCA2 deficient Capan1 and BRCA2 proficient MiaPaCa2 cell lines to MK2206 were compared by analyzing cell proliferation and colony formation. RAD51 knockdown cells were treated with MK2206 and analyzed for cell proliferation and apoptosis using flow cytometry.

Results: RAD51 expression confirmed a stepwise increase from normal pancreas to chronic pancreatitis through advancing grade and stage of PDAC. Patients with PDAC tumors expressing high levels of RAD51 had significantly higher tumor grade, stage, and lower OS when compared with patients with tumors that had low RAD51 expression (median survival of 15 months vs 37 months, respectively; P=0.025). BRCA2 deficient Capan1 PDAC cells were sensitive to MK2206 when compared to BRCA2 proficient MiaPaCa2 cells. Bioluminescent imaging (BLI) guided tumor growth analysis confirmed that RAD51 inhibition with B02 treatment decreased tumor growth in PDAC cells. B02 and MK2206 treated PDA and LMP cells showed synergistic downregulation of colony formation in comparison to either B02 or MK2206 drugs treated cells. RAD51 knockdown cells treated with MK2206 showed enhanced cell apoptosis and attenuated cell proliferation.

Conclusions: Our findings indicate that RAD51 inhibition increases sensitivity to AKT inhibition. RAD51 expression levels in PDAC tumors may be useful in identification of PDAC patients who will benefit from this therapy.

Citation Format: Surpiya Srinivasan, Chanjuan Shi, Casey Roberts, Xizi Dai, Fanuel Messaggio, Krisztina Kovacs, Michael VanSaun, Nipun Merchant, Nagaraj Nagathihalli.{Authors}. RAD51 sensitizes pancreatic cancer cells to AKT inhibition. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B78.

Abstract A46: AdipoRon suppresses ERK and STAT3 to inhibit pancreatic cancer growth

Introduction: The increasing incidence of pancreatic cancer is associated with a rising prevalence of obesity, a documented risk factor for the disease. Obesity harbors a systemic chronic inflammatory disorder characterized by increased production and secretion of pro-inflammatory adipokines leptin, TNF-α, and IL-6; while exhibiting a decrease in the anti-inflammatory adipokine; adiponectin. Dysregulation of these factors is thought to be a key mechanism of obesity associated cancers, contributing to increased activation of mitogenic pathways including PI3K and MAPK. Adiponectin represents an important negative regulator of leptin, TNF-α and IL-6. We previously demonstrated that adiponectin inhibits pancreatic cancer proliferation and tumor growth, however, the molecular mechanisms by which adiponectin regulates these processes are unknown. We hypothesize that Adiponectin Receptor (AdipoR) agonists elicit anti-tumor effects through suppression of RAS-MAPK mediated pathways and its downstream signaling components in pancreatic cancer progression.

Experimental Procedures: The anti-tumor effects of AdipoRon, a novel small molecule agonist of the AdipoR, were assessed in vitro on human (MiaPaca-2 and Panc-1) and murine (P-4313 and K8484) pancreatic cancer cell lines. Cells were treated with AdipoRon in a dose-dependent manner and then assayed for cellular proliferation, apoptosis, colony formation and anchorage-independent growth. The effect of AdipoRon on activation of key RAS-MAPK signaling regulators was investigated by immunoblot analysis. To determine whether AdipoRon could inhibit the effects of obesity associated pro-tumorigenic cytokines, human and mouse pancreatic cancer cells were exposed to plasma collected from obese mice or specifically with recombinant cytokines. To determine whether AdipoRon could inhibit tumor growth in vivo, mice were orthotopically injected in the pancreas with the murine KrasG12D mutant P-4313 cell line. Tumors were allowed to establish for two weeks and treated with either vehicle or AdipoRon. Tumor size and number of Ki67 positive cells were assessed.

Results: Compared to vehicle treatment, in vitro assessment confirmed that AdipoRon was highly effective at inhibiting cell proliferation, increasing apoptosis and preventing colony formation for all pancreatic cell lines tested. Anchorage independent growth was drastically reduced for both Panc1 (3.8 fold) and MiaPaca-2 (5.1 fold) cell lines in the presence of AdipoRon. Treatment of both murine and human pancreatic cancer cell lines with AdipoRon caused a significant dose dependent decrease in pSTAT3, pERK1, and pERK2 with a simultaneous increase in pAMPK. Importantly, AdipoRon completely antagonized the stimulatory effects of obese plasma or recombinant IL-6 on the activation of pSTAT3. Administration of AdipoRon to P-4313 orthotopic pancreatic tumor bearing mice resulted in four fold decrease in tumor size and a 50% reduction in tumor cell proliferation.

Conclusions: AdipoRon, an adiponectin receptor agonist, suppresses KRAS signaling mediators ERK and STAT3 while simultaneously increasing AMPK resulting in inhibition of pancreatic cancer proliferation and tumor growth. Targeting of adiponectin receptors can provide a viable therapeutic strategy for the treatment of pancreatic cancer.

Citation Format: Fanuel Messaggio, Alisha M. Mendonsa, Jason A. Castellanos, Casey Roberts, Nagaraj S. Nagathihalli, Nipun B. Merchant, Lee D. Gorden, Michael N. VanSaun.{Authors}. AdipoRon suppresses ERK and STAT3 to inhibit pancreatic cancer growth. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A46.

Human Lipoaspirate as Autologous Injectable Active Scaffold for One-Step Repair of Cartilage Defects

Research on mesenchymal stem cells from adipose tissue shows promising results for cell-based therapy in cartilage lesions. In these studies, cells have been isolated, expanded, and differentiated in vitro before transplantation into the damaged cartilage or onto materials used as scaffolds to deliver cells to the impaired area. The present study employed in vitro assays to investigate the potential of intra-articular injection of micro-fragmented lipoaspirate as a one-step repair strategy; it aimed to determine whether adipose tissue can act as a scaffold for cells naturally present at their anatomical site. Cultured clusters of lipoaspirate showed a spontaneous outgrowth of cells with a mesenchymal phenotype and with multilineage differentiation potential. Transduction of lipoaspirate clusters by lentiviral vectors expressing GFP evidenced the propensity of the outgrown cells to repopulate fragments of damaged cartilage. On the basis of the results, which showed an induction of proliferation and ECM production of human primary chondrocytes, it was hypothesized that lipoaspirate may play a paracrine role. Moreover, the structure of a floating culture of lipoaspirate, treated for 3 weeks with chondrogenic growth factors, changed: tissue with a high fat component was replaced by a tissue with a lower fat component and connective tissue rich in GAG and in collagen type I, increasing the mechanical strength of the tissue. From these promising in vitro results, it may be speculated that an injectable autologous biologically active scaffold (lipoaspirate), employed intra-articularly, may 1) become a fibrous tissue that provides mechanical support for the load on the damaged cartilage; 2) induce host chondrocytes to proliferate and produce ECM; and 3) provide cells at the site of injury, which could regenerate or repair the damaged or missing cartilage.

Characteristics and Properties of Mesenchymal Stem Cells Derived from Microfragmented Adipose Tissue

The subcutaneous adipose tissue provides a clear advantage over other mesenchymal stem cell sources due to the ease with which it can be accessed, as well as the ease of isolating the residing stem cells. Human adipose-derived stem cells (hADSCs), localized in the stromal–vascular portion, can be isolated ex vivo using a combination of washing steps and enzymatic digestion. In this study, we report that microfragmented human lipoaspirated adipose tissue is a better stem cell source compared to normal lipoaspirated tissue. The structural composition of microfragments is comparable to the original tissue. Differently, however, this procedure activates the expression of antigens, such as β-tubulin III. The hADSCs derived from microfragmented lipoaspirate tissue were systematically characterized for growth features, phenotype, and multipotent differentiation potential. They fulfill the definition of mesenchymal stem cells, although with a higher neural phenotype profile. These cells also express genes that constitute the core circuitry of self-renewal such as OCT4, SOX2, and NANOG, and neurogenic lineage genes such as NEUROD1, PAX6, and SOX3. Such findings suggest further studies by evaluating Microfrag-AT hADSC action in animal models of neurodegenerative conditions.

A specific combination of zeaxanthin, spermidine and rutin prevents apoptosis in human dermal papilla cells

Hair follicle (HF) regression is characterized by the activation of apoptosis in HF cells. Dermal papilla cells play a leading role in the regulation of HF development and cycling. Human follicular dermal papilla cells (HFDPC) were used to investigate the protective activities of rutin, sperimidine and zeaxanthine. HFDP cell incubation with staurosporine caused apoptosis, which was completely inhibited by exposure to rutin (2.2 μM), spermidine (1 μM) and zeaxanthin (80 μM). These agents were much less effective when applied as single compounds. Moreover, treatment preserved the expression of anti-apoptotic molecules such as Bcl-2, MAP-kinases and their phosphorylated forms. In conclusion, the investigated agents may represent an effective treatment for the prevention of apoptosis, one of the leading events involved in hair bulb regression.