SHP2 regulates adipose maintenance and adipocyte-pancreatic cancer cell crosstalk via PDHA1

Adipocytes are the most abundant cell type in the adipose tissue, and their dysfunction is a significant driver of obesity-related pathologies, such as cancer. The mechanisms that (1) drive the maintenance and secretory activity of adipocytes and (2) mediate the cancer cellular response to the adipocyte-derived factors are not fully understood. To address that gap of knowledge, we investigated how alterations in Src homology region 2-containing protein (SHP2) activity affect adipocyte function and tumor crosstalk. We found that phospho-SHP2 levels are elevated in adipose tissue of obese mice, obese patients, and differentiating adipocytes. Immunofluorescence and immunoprecipitation analyses as well as in-silico protein-protein interaction modeling demonstrated that SHP2 associates with PDHA1, and that a positive association promotes a reactive oxygen species (ROS)-driven adipogenic program. Accordingly, this SHP2-PDHA1-ROS regulatory axis was crucial for adipocyte maintenance and secretion of interleukin-6 (IL-6), a key cancer-promoting cytokine. Mature adipocytes treated with an inhibitor for SHP2, PDHA1, or ROS exhibited an increased level of pro-lipolytic and thermogenic proteins, corresponding to an increased glycerol release, but a suppression of secreted IL-6. A functional analysis of adipocyte-cancer cell crosstalk demonstrated a decreased migration, invasion, and a slight suppression of cell cycling, corresponding to a reduced growth of pancreatic cancer cells exposed to conditioned media (CM) from mature adipocytes previously treated with inhibitors for SHP2/PDHA1/ROS. Importantly, PDAC cell growth stimulation in response to adipocyte CM correlated with PDHA1 induction but was suppressed by a PDHA1 inhibitor. The data point to a novel role for (1) SHP2-PDHA1-ROS in adipocyte maintenance and secretory activity and (2) PDHA1 as a regulator of the pancreatic cancer cells response to adipocyte-derived factors.

Combined PI3K and MAPK inhibition synergizes to suppress PDAC

Oncogenic KRAS mutations are nearly ubiquitous in pancreatic ductal adenocarcinoma (PDAC), yet therapeutic attempts to target KRAS as well as its target MAPK pathway effectors have shown limited success due to the difficulty to pharmacologically target KRAS, inherent drug resistance in PDAC cells, and acquired resistance through activation of alternative mitogenic pathways such JAK-STAT and PI3K-AKT. While KRAS canonically drives the MAPK signaling pathway via RAF-MEK-ERK, it is also known to play a role in PI3K-AKT signaling. Our therapeutic study targeted the PI3K-AKT pathway with the drug Omipalisib (p110α/β/δ/γ and mTORC1/2 inhibitor) in combination with MAPK pathway targeting drug Trametinib (MEK1/2 inhibitor) or SHP099-HCL (SHP099), which is an inhibitor of the KRAS effector SHP2. Western blot analysis demonstrated that application of Trametinib or SHP099 alone selectively blocked ERK phosphorylation (pERK) but failed to suppress phosphorylated AKT (pAKT) and in some instances increased pAKT levels. Conversely, Omipalisib alone successfully inhibited pAKT but failed to suppress pERK. Therefore, we hypothesized that a combination therapeutic comprised of Omipalisib with either Trametinib or SHP099 would inhibit two prominent mitogenic pathways, MEK and PI3K-AKT, to more effectively suppress pancreatic cancer. In vitro studies demonstrated that both Omipalisib/Trametinib and Omipalisib/SHP099 combination therapeutic strategies were generally more effective than treatment with each drug individually at reducing proliferation, colony formation, and cell migration compared to vehicle controls. Additionally, we found that while combination Omipalisib/SHP099 treatment reduced implanted tumor growth in vivo , the Omipalisib/Trametinib treatment was significantly more effective. Therefore, we additionally tested the Omipalisib/Trametinib combination therapeutic in the highly aggressive PKT (Ptf1a cre , LSL-Kras G12D , TGFbR2 fl/fl ) spontaneous mouse model of PDAC. We subsequently found that PKT mice treated with the Omipalisib/Trametinib combination therapeutic survived significantly longer than mice treated with either drug alone, and more than doubled the mean survival time of vehicle control mice. Altogether, our data support the importance of a dual treatment strategy targeting both MAPK and PI3K-AKT pathways.

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.

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.

Abstract 157: DUSP6 modulates migration and glycolysis in PDAC cells

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor and is the seventh cause of death for cancer worldwide, fifth in the US. The highly malignant profile is mainly caused by the constitutive activation of mutant KRAS - found in approximately 90% of PDAC cases. The undruggability of genetic KRAS mutations has led to efforts to find new therapeutical targets that focus on downstream molecules in this pathway. DUSP6 is a dual-specificity phosphatase that regulates ERK1/2 phosphorylation and, therefore, downstream RAS pathway activation. DUSP6 has been demonstrated to be differentially expressed during PDAC tumorigenesis, which we believe is critical for tumor progression and metastasis. In silico analysis on the TCGA dataset revealed that DUSP6 is overexpressed in primary tumor samples compared to normal pancreatic tissue. This data was confirmed in an independent dataset (GSE71729) that further revealed DUSP6 overexpression in metastatic samples compared to primary tumor samples. Additionally, patients with higher DUSP6 expression have worse overall survival than patients with low DUSP6 expression (P = 0.039), reaffirming its clinical relevance. We then assessed DUSP6 expression in tumor sections derived from KC and KPC mice using the RNAscope technology and observed that DUSP6 was strongly overexpressed in tumorigenic lesions, and largely co-localized with KRT19 expression. Using BCI - a pharmacological DUSP6 inhibitor - we observed significantly reduced viability in vitro in all the cell lines (P < 0.0001). DUSP6 inhibition also promoted ERK1/2 activation, as expected. Surprisingly, we observed that BCI-mediated DUSP6 inhibition increased migratory capacity in AsPC-1 (P < 0.0001), but not on BxPC-3 cells. Furthermore, murine AKC cells presented the completely opposite phenotype, with a significant decrease in migratory capacity (P < 0.0001), indicating a possible context dependent response. To further understand the molecular mechanisms behind DUSP6 in PDAC, we performed a gene set enrichment analysis using the TCGA and GSE15471 datasets and observed a strong correlation between DUSP6 and the glycolysis pathway. Therefore, we knocked down DUSP6 in K8484 cells and evaluated their proliferation in response to 2-DG, which was significantly decreased in comparison to treated parental cells (P < 0.001). In accordance with that, DUSP6 knockdown cells were significantly more impacted by 2-DG treatment than the parental cells regarding migratory capacity, bringing it to the basal level. Collectively, these results suggest that DUSP6 appears to modulate the metastatic process, and this phenotype correlates with the altered glycolytic capacity of pancreatic cancer cells. We are currently expanding our studies to additional cell lines and using in vivo models to further investigate if the observed phenotype is context dependent. To assess glycolytic changes in the cells, we are currently performing Seahorse-based assays.

Citation Format: Mariana T. Ruckert, Bailey A. Bye, Michael N. VanSaun, Vanessa S. Silveira. DUSP6 modulates migration and glycolysis in PDAC cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 157.

Abstract 4027: Dual MEK and AKT inhibition suppresses pancreatic cancer growth and migration

Pancreatic cancer is one of the deadliest cancers, due to late diagnosis and very few available therapeutic treatments. The Kras gene is frequently mutated in pancreatic cancer, but previous clinical trials using RAS inhibitors have proven ineffective. Additionally, many drug treatments targeting the MAPK pathway have shown little success due to the inherent drug resistance of pancreatic cancer cells and to acquired resistance through activation of alternative proliferative pathways such as JAK-STAT and PI3K-AKT. Our pathway analysis after MEK inhibition in pancreatic cancer cells displayed sustained and/or upregulation of AKT activity in multiple cell lines. Therefore, we hypothesize that a combination treatment of Trametinib and Omipalisib would block two prominent mitogenic pathways (MEK and AKT, respectively) to suppress cancer cell proliferation and migration. Multiple analyses including Western blot, clonogenic, 5-Ethynyl-2’-Deoxyuridine (EDU), and scratch migration assays were employed to determine the augmentation of cellular function in murine and anthropic pancreatic cancer cell lines after single or combination treatment with Trametinib and/or Omipalisib. Results demonstrated that application of Omipalisib alone was successful at blocking pAKT but failed to suppress pERK. Conversely, Trametinib alone selectively inhibited pERK but did not affect pAKT levels. The combination treatment successfully suppressed both pathways in relatively low quantities, indicating their efficacy as a dual therapeutic. Dual therapy was further effective at inhibiting cell growth as evidenced by clonogenic and EdU assays. Recovery and closure from an in vitro scratch wound was also significantly inhibited with combination of Omipalisib and Trametinib. In vivo studies demonstrated that both the pancreatic xenograft mean tumor growth and final tumor size were significantly reduced in response to the combination treatment compared to vehicle. In conclusion, dual therapy with Omipalisib and Trametinib showed a greater anti-tumor efficacy than treatment with either drug alone. Currently, we are determining the prolonged effectiveness of this combination treatment program in genetically-engineered mouse models. If successful, a pharmacological application of Omipalisib and Trametinib has the potential to provide a beneficial therapeutic option to pancreatic cancer patients.

Citation Format: Jarrid Jack, Alexandra Pierce, Bailey Bye, McKinnon Walsh, Prabhakar Chalise, Michael N. VanSaun. Dual MEK and AKT inhibition suppresses pancreatic cancer growth and migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4027.

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.

Abstract 2824: SHP2-PDHA metabolic axis is critical for adipocyte function by mitigating ER stress-induced adipocytes dysfunction: Implication for obesity-driven pancreatic ductal adenocarcinoma progression

Obesity remains a major risk factor for the development of pancreatic cancer. Animal studies demonstrated that obese mice develop larger and more metastatic pancreatic cancer compared to their lean counterpart. Within the tumor environment are adipocytes that secrete adipokines, which promote inflammation and directly stimulate pancreatic cancer cells. Understanding the mechanisms that alter adipocyte function and adipokine secretion is critical for circumventing adipocyte-mediated influence on pancreatic cancer progression. Targeting of the Src homology region 2 containing protein tyrosine phosphatase (SHP-2) in the cancer cells has recently shown promising potential, yet the effect of SHP2 inhibition on stromal components has not been addressed. Here we demonstrate that SHP2 and the mitochondrial protein pyruvate dehydrogenase (PDHA) are critical mediators of adipocyte function, through mitigation of ER stress in adipocytes. In order to understand the role of SHP2 and PDHA in adipocytes, we performed Oil Red O staining and western blot assays on cultured adipocytes. We found that the transition from pre-adipocytes to fully developed adipocytes is marked by significant accumulation of phospho-SHP2, PDHA and the ER stress marker Bip. Chemical inhibition of SHP2 or PDHA augmented ER stress and impaired lipid production in the adipocytes; these effects were reversed by the ER stress inhibitor, 4-Phenylbyturic acid (4-PBA). Moreover, pancreatic cancer cells exposed to conditioned media from differentiated adipocytes, in which either SHP2 or PDHA was inhibited, are less aggressive and invasive compared to PDAC cells grown in conditioned media from control adipocytes with no inhibitor treatment. Therefore, our studies indicate that SHP2 and PDHA, in adipocytes, are key mediators of obesity-driven pancreatic cancer progression. Future studies will focus on understanding the SHP2-PDHA axis in adipocytes and further to elucidate how cancer cell extrinsic effects of SHP2 inhibition could alter PDAC progression.

Citation Format: Appolinaire A. Olou, Jarrid Jack, Sharon Manley, Joseph Ambrose, McKinnon Walsh, Austin Eades, Michael N. VanSaun. SHP2-PDHA metabolic axis is critical for adipocyte function by mitigating ER stress-induced adipocytes dysfunction: Implication for obesity-driven pancreatic ductal adenocarcinoma progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2824.

Abstract 2467: Adiponectin receptor agonism induces a metabolic switch in pancreatic cancer cells from oxidative phosphorylation to glycolysis

Understanding the impact of risk factors on the progression of pancreatic cancer is critical for the development of novel therapeutics. Multiple studies have clearly shown that obesity positively correlates with increased progression of pancreatic adenocarcinoma (PDAC). We have demonstrated that individual adipose derived cytokines (aka adipokines) can elicit either pro-tumorigenic or anti-tumorigenic effects on PDAC progression. We previously demonstrated that adiponectin receptor agonism effectively suppresses pancreatic cancer growth in vitro as well as in vivo, through suppression of MAPK as well as STAT3 pathways. Yet, adiponectin is well known to stimulate the AMPK pathway and therefore we hypothesized that adiponectin agonism could also be affecting metabolic function in PDAC. In our current studies, we defined multiple metabolic alterations in pancreatic cancer cells in response to adiponectin receptor agonism using a seahorse-based assay. Human and murine PDAC cell lines were seeded into XFe96 microplates and subjected to a mitochondrial stress test as well as the glycolysis stress test. Our results demonstrate that adiponectin receptor activation impairs pancreatic cancer mitochondrial function leading to a metabolic switch from mitochondrial respiration to glycolysis. We further demonstrate that this switch is associated with AMPK phosphorylation-mediated inhibition of Acetyl Coenzyme A Carboxylase (ACC), the lipogenic enzyme whose inhibition induces fatty acid breakdown. Thus, our results support a role for adipose-secreted factors to influence the metabolic phenotype of pancreatic cancer. Since metabolic rewiring is often associated with development of chemotherapeutic resistance in cancer, we are currently testing whether dual therapeutic targeting of the mitochondrial respiration, via adiponectin receptor agonism, and glycolysis would provide an efficacious therapeutic.

Citation Format: Sharon J. Manley, Jarrid Jack, Joseph Ambrose, Appolinaire A. Olou, Michael N. VanSaun. Adiponectin receptor agonism induces a metabolic switch in pancreatic cancer cells from oxidative phosphorylation to glycolysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2467.

Abstract 3168: Pancreatic cancer lipid theft is mediated by MAP Kinase signaling in adipocytes

Obesity is a major risk factor which drives cancer progression in a variety of cancers, including pancreatic ductal adenocarcinoma (PDAC). In obese individuals the adipose tissue becomes reactive, therefore the crosstalk between adipose tissue and PDAC tumors is essential to understand the mechanisms underlying PDAC progression and cancer associated conditions like cachexia. Lipid loading in pancreatic cancer has been shown to drive a variety of protumor phenotypes, including increased growth and invasiveness. Previous work has shown that cancers including breast, ovarian, and melanoma have the capability to induce lipid transfer from adipocytes to cancer cells. However, lipid transfer from adipocytes to pancreatic cancer cells has not been shown nor has the mechanism been elucidated. In addition, most work has focused on how adipose tissue factors affect the cancer cells, while little has been done to understand how the cancer cells affect the adipocytes. We believe pancreatic cancer cells are capable of inducing lipid release from adipocytes by inducing the destabilization of lipid droplets. To test the capacity of PDAC to induce lipid release and transfer from adipocytes, differentiated adipocytes were loaded with the fatty acid, BODIPY 568 C12, and then co-cultured with pancreatic cancer cells using a transwell coculture system to prevent direct contact. BODIPY labeled lipid uptake was detected in cancer cells using both immunofluorescence microscopy and flow cytometry. In the adipocytes, we observed destabilization of lipid droplet via loss in perilipin 1 immunofluorescence, decreased perilipin levels in western blot analysis, and as a reduction in lipid droplet size after co-culture. Similar results were observed when the experiment was repeated using cancer cell conditioned media instead of a co-culture system. Exposure to cancer conditioned media was found to induce increased pERK in the adipocytes. To determine whether cancer conditioned media was affecting adipocyte mitochondrial function, we used the Agilent Seahorse mitochondrial stress test. Results demonstrated that cancer conditioned media impaired the maximal mitochondrial respiration of adipocytes, which was blocked by MEK inhibition. We conclude that pancreatic cancer cells are capable of inducing lipid transfer from adipocytes by secreting soluble factors which increase lipolysis and MAP kinase signaling in adipocytes. Once lipids have been liberated from the adipocytes, the pancreatic cancer cells scavenge them as an energy source to drive cancer progression. We believe our findings demonstrate an active role for tumor-adipocyte crosstalk and could provide therapeutic targets for the treatment of PDAC in obese individuals or for cancer associated cachexia.

Citation Format: Joseph Ambrose, Austin E. Eades, McKinnon Walsh, Michael N. VanSaun. Pancreatic cancer lipid theft is mediated by MAP Kinase signaling in adipocytes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3168.

Src kinase inhibition restores E-cadherin expression in dasatinib-sensitive pancreatic cancer cells

The Src family of non-receptor tyrosine kinases are frequently activated in pancreatic ductal adenocarcinoma (PDAC), contributing to disease progression through downregulation of E-cadherin and induction of epithelial-to-mesenchymal transition (EMT). The purpose of this study was to examine the efficacy of Src kinase inhibition in restoring E-cadherin levels in PDAC. Immunohistochemical analysis of human PDAC samples showed Src activation is inversely correlated with E-cadherin levels. Protein and mRNA levels of E-cadherin, the gene expression of its various transcriptional repressors (Zeb1, Snail, Slug, LEF-1, TWIST), and changes in sub-cellular localization of E-cadherin/β-catenin in PDAC cells were characterized in response to treatment with the Src inhibitor, dasatinib (DST). DST repressed Slug mRNA expression, promoted E-cadherin transcription, and increased total and membranous E-cadherin/β-catenin levels in drug-sensitive PDAC cells (BxPC3 and SW1990), however no change was observed in drug-resistant PANC1 cells. BxPC3, PANC1, and MiaPaCa-2 flank tumor xenografts were treated with DST to examine changes in E-cadherin levels in vivo. Although DST inhibited Src phosphorylation in all xenograft models, E-cadherin levels were only restored in BxPC3 xenograft tumors. These results suggest that Src kinase inhibition reverses EMT in drug-sensitive PDAC cells through Slug-mediated repression of E-cadherin and identifies E-cadherin as potential biomarker for determining response to DST treatment.

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.

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 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.

Pancreatic stellate cell secreted IL-6 stimulates STAT3 dependent invasiveness of pancreatic intraepithelial neoplasia and cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is a dynamic tumor supported by several stromal elements such as pancreatic stellate cells (PSC). Significant crosstalk exists between PSCs and tumor cells to stimulate oncogenic signaling and malignant progression of PDAC. However, how PSCs activate intercellular signaling in PDAC cells remains to be elucidated. We have previously shown that activated signal transducer and activator of transcription 3 (STAT3) signaling is a key component in the progression of pancreatic neoplasia. We hypothesize that PSC secreted IL-6 activates STAT3 signaling to promote PanIN progression to PDAC. Human PDAC and mouse PanIN cells were treated with PSC-conditioned media (PSC-CM), and phospho- and total-STAT3 levels by immunoblot analysis were determined. IL-6 was quantified in PSC-CM and cell invasion and colony formation assays were performed in the presence or absence of a neutralizing IL-6 antibody and the JAK/STAT3 inhibitor AZD1480. Serum from Ptf1aCre/+;LSL-KrasG12D/+;Tgfbr2flox/flox (PKT) and LSL-KrasG12D/+; Trp53R172H/+; Pdx1Cre/+ (KPC) mice demonstrated increased levels of IL-6 compared to serum from non-PDAC bearing KC and PK mice. PSC secreted IL-6 activated STAT3 signaling in noninvasive, precursor PanIN cells as well as PDAC cells, resulting in enhanced cell invasion and colony formation in both cell types. There was a significant positive linear correlation between IL-6 concentration and the ratio of phosphorylated STAT3/total STAT3. IL-6 neutralization or STAT3 inhibition attenuated PSC-CM induced activation of STAT3 signaling and tumorigenicity. These data provide evidence that PSCs are directly involved in promoting the progression of PanINs towards invasive carcinoma. This study demonstrates a novel role of PSC secreted IL-6 in transitioning noninvasive pancreatic precursor cells into invasive PDAC through the activation of STAT3 signaling.

Modulation of the leptin receptor mediates tumor growth and migration of pancreatic cancer cells

Obesity has been implicated as a significant risk factor for development of pancreatic cancer. In the setting of obesity, a systemic chronic inflammatory response is characterized by alterations in the production and secretion of a wide variety of growth factors. Leptin is a hormone whose level increases drastically in the serum of obese patients. High fat diet induced obesity in mice leads to an overall increased body weight, pancreatic weight, serum leptin, and pancreatic tissue leptin levels. Here we report the contribution of obesity and leptin to pancreatic cancer growth utilizing an in vivo orthotopic murine pancreatic cancer model, which resulted in increased tumor proliferation with concomitant increased tumor burden in the diet induced obese mice compared to lean mice. Human and murine pancreatic cancer cell lines were found to express the short as well as the long form of the leptin receptor and functionally responded to leptin induced activation through an increased phosphorylation of AKT473. In vitro, leptin stimulation increased cellular migration which was blocked by addition of a PI3K inhibitor. In vivo, depletion of the leptin receptor through shRNA knockdown partially abrogated increased orthotopic tumor growth in obese mice. These findings suggest that leptin contributes to pancreatic tumor growth through activation of the PI3K/AKT pathway, which promotes pancreatic tumor cell migration.

Host and tumor derived MMP13 regulate extravasation and establishment of colorectal metastases in the liver

BACKGROUND

Non alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in the United States and worldwide. Our studies have previously shown an increase in metastatic burden in steatotic vs. normal livers using a mouse model of diet induced steatosis. In the present study we aim to identify and evaluate the molecular factors responsible for this increase in tumor burden.

METHODS

We assessed changes in expression of a panel of matrix metalloproteinases (MMPs) using qRT-PCR between normal and steatotic livers and validated them with western blot analysis of protein levels. To evaluate the role of MMP13 on tumor development, we utilized a splenic injection model of liver metastasis in Wildtype and Mmp13 deficient mice, using either parental or stable Mmp13 knockdown cell lines. Further, to evaluate changes in the ability of tumor cells to extravasate we utilized whole organ confocal microscopy to identify individual tumor cells relative to the vasculature. MTT, migration and invasion assays were performed to evaluate the role of tumor derived MMP13 on hallmarks of cancer in vitro.

RESULTS

We found that MMP13 was significantly upregulated in the steatotic liver both in mice as well as human patients with NAFLD. We showed a decrease in metastatic tumor burden in Mmp13-/- mice compared to wildtype mice, explained in part by a reduction in the number of tumor cells extravasating from the hepatic vasculature in the Mmp13-/- mice compared to wildtype mice. Additionally, loss of tumor derived MMP13 through stable knockdown in tumor cell lines lead to decreased migratory and invasive properties in vitro and metastatic burden in vivo.

CONCLUSIONS

This study demonstrates that stromal as well as tumor derived MMP13 contribute to tumor cell extravasation and establishment of metastases in the liver microenvironment.

Abstract 4984: Contribution of MMP13 to tumor development in the steatotic liver microenvironment

With the rising prevalence of obesity there has been a marked increase in the incidence of non alcoholic fatty liver disease (NAFLD). Epidemiologically, NAFLD has been linked to an increased risk for development of primary liver cancer (HCC), however the mechanisms involved are not known. The liver is also a frequent site of metastasis for several types of cancers. To determine the effect of steatosis (fatty liver) on tumor metastasis to the liver, we used a mouse model of diet induced steatosis coupled with the splenic injection model of metastasis to the liver and found a significant increase in the number of tumors in the steatotic livers. To evaluate what molecular changes distinguish the steatotic liver from normal liver, microarray analysis was performed and demonstrated that MMP13, a member of the Matrix Metalloproteinase family recognized to be involved in liver disease and cancer progression, is significantly upregulated in the steatotic liver compared to normal livers of mice. We evaluated MMP13 expression in human patients with NAFLD and found that MMP13 is elevated with the progression of NAFLD. We hypothesize that increased MMP13 levels in the steatotic liver contribute to a more permissive microenvironment for the establishment of liver tumors. To test this hypothesis, mice genetically deficient in MMP13 or control wildtype mice, with and without steatosis, were injected with syngeneic MC38 colon cancer cells. Examination of the two groups demonstrated a significant decrease in the number of tumors in the MMP13 null mice (P <0.01). Additionally, since the tumor cells themselves express MMP13, wildtype mice were injected with either shRNA control or MMP13 knockdown MC38 colon cancer cells to determine the role of tumor cell derived MMP13. Using transwell migration assay and the platypus invasion system with parental and MMP13 shRNA knockdown MC38 cells we found that loss of MMP13 decreases the invasive and migratory properties of the metastatic cancer cells in vitro. In conclusion, we found that MMP13 is elevated in the setting of steatosis and that loss of both stromal and tumor derived MMP13 lead to decreased number of metastatic foci in the liver. Tumor derived MMP13 effects tumor cell migration and invasion invitro. MMP13 may thus be a potential target to control initiation and growth of metastatic cancer of the liver.

Citation Format: Alisha Maria Mendonsa, Michael N. VanSaun, Lee Gorden. Contribution of MMP13 to tumor development in the steatotic liver microenvironment. [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 4984. doi:10.1158/1538-7445.AM2014-4984

Targeting the Wnt pathway in synovial sarcoma models

Synovial sarcoma is an aggressive soft-tissue malignancy of children and young adults, with no effective systemic therapies. Its specific oncogene, SYT-SSX (SS18-SSX), drives sarcoma initiation and development. The exact mechanism of SYT-SSX oncogenic function remains unknown. In an SYT-SSX2 transgenic model, we show that a constitutive Wnt/β-catenin signal is aberrantly activated by SYT-SSX2, and inhibition of Wnt signaling through the genetic loss of β-catenin blocks synovial sarcoma tumor formation. In a combination of cell-based and synovial sarcoma tumor xenograft models, we show that inhibition of the Wnt cascade through coreceptor blockade and the use of small-molecule CK1α activators arrests synovial sarcoma tumor growth. We find that upregulation of the Wnt/β-catenin cascade by SYT-SSX2 correlates with its nuclear reprogramming function. These studies reveal the central role of Wnt/β-catenin signaling in SYT-SSX2-induced sarcoma genesis, and open new venues for the development of effective synovial sarcoma curative agents.

SIGNIFICANCE

Synovial sarcoma is an aggressive soft-tissue cancer that afflicts children and young adults, and for which there is no effective treatment. The current studies provide critical insight into our understanding of the pathogenesis of SYT–SSX-dependent synovial sarcoma and pave the way for the development of effective therapeutic agents for the treatment of the disease in humans.

Abstract 389: MMP12 and myeloid cell populations influence establishment of tumor metastases in the steatotic liver microenvironment

Introduction: Non-alcoholic fatty liver disease (NAFLD), encompassing steatosis and progression to non-alcoholic steatohepatitis (NASH) are liver disorders of increasing clinical significance. Studies in our lab have shown that hepatic steatosis establishes a permissive microenvironment for metastatic tumor seeding and tumor progression in the liver. To understand the molecular factors influencing the initial survival and growth of tumors in the steatotic liver microenvironment, we adopted a candidate approach and performed microarray analysis to compare RNA from normal vs steatotic liver samples in mice. MMP12 (macrophage metalloelastase) was identified as an important proteinase associated with the microenvironments of hepatic steatosis and steatohepatitis. MMP12 can influence immune-mediated injury response by processing latent TNF alpha and regulating neutrophil infiltration, cytokine release as well as macrophage recruitment. We hypothesize that increased MMP12 levels in the steatotic liver contribute to a more permissive microenvironment for primary tumor growth and establishment of metastases by alteration of inflammatory cell populations. Results: Realtime qPCR anlaysis verified a significant increase in MMP12 expression in murine steatotic livers compared to normal control livers. In a splenic injection model, hepatic metastases in steatotic MMP12 deficient livers were significantly reduced as compared to hepatic metastases in steatotic wildtype livers. Flow cytometric analysis demonstrated an alteration in the level of Gr-1 positive inflammatory cell populations in the steatotic livers of both wildtype and MMP12 deficient livers when compared to normal nonsteatotic livers. Although no significant changes were observed in the percentage of F4/80 positive macrophage population, using immunohistochemistry we did observe accumulation of F4/80 positive macrophages into crown-like structures within steatotic MMP12 deficient livers. To determine whether the inflammatory cells in the liver microenvironment were contributing to survival of tumor cells, we performed an in vitro co-culture assay of syngeneic MC38 tumor cells with either CD90.2 cells (pan T cells) or CD11b cells (macrophages/monocytes). Fewer numbers MC38 cells were present 3 days after co-culture with CD11b cells from MMP12 deficient mice, which was corroborated with decreased luciferase measurements from MC38-luc tagged cells. Conclusions: These results suggest a role for MMP12 in mediating the inflammatory response accompanying tumor establishment in the steatotic liver microenvironment. The molecular mechanisms by which MMP12 influences a decrease in metastatic tumor burden in the setting of fatty liver disease are currently being investigated.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 389. doi:1538-7445.AM2012-389

Abstract 299: Modulation of the leptin receptor in pancreatic cancer cells mediates tumor growth

Background: Pancreatic cancer is the fourth leading cause of cancer death with a five year survival rate around 5%, which has not changed in 30 years. Obesity and increased abdominal adipose tissue independently correlate with an increased relative risk for the development of pancreatic cancer. These conditions have been associated with altered levels of adipokines, or adipose secreted cytokines. Circulating serum levels of the adipokine leptin are increasesddramatically in obese patients as well as in high fat diet induced obese mice. Leptin has been shown to induce oncogenic signaling in breast and prostate cancer. We have previously shown an increase in orthotopic pancreatic tumor size in high fat diet induced obese mice compared with regular diet control mice. We hypothesize that leptin signaling mediates pancreatic tumorigenesis. Methods: Leptin receptor status was determined in human as well as murine pancreatic cell lines. Leptin stimulated cell proliferation was determined using a modified BrdU assay. Leptin receptor levels were knocked down in human and murine pancreatic tumor cells using a shRNAmir approach. Leptin receptor shRNA Panc02 knockdown cells were injected orthotopically into the pancreas of C57/Bl6J mice on regular or high fat diet to determine the contribution of leptin to pancreatic tumor growth. Results: We have detected the long form of the leptin receptor in five human and four murine pancreatic cancer cell lines. In vitro administration of leptin stimulated proliferation of Panc1 and CFPAC1 cell lines, which was abrogated with co-incubation of a leptin antagonist. To better understand the mechanism of leptin-mediated signaling, we studied downstream targets and identified a significant increase in phosphorylation of STAT3 in Panc1, BXPC3 and CFPAC1 cell lines after leptin treatment. Orhtotopic injection of leptin receptor shRNA Panc02 cells into normal and obese mice showed a markedly diminished tumor growth in obese mice when compared to the nonsilencing control Panc02 cell growth in obese mice. Conclusion: These results implicate leptin as a mediator of pancreatic tumorigenesis and suggest that leptin activation is mediated in part through STAT3 signaling. Knockdown of the leptin receptor results in inhibition of high fat diet associated tumor growth in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 299. doi:1538-7445.AM2012-299

Abstract 1947: Self-reporting dendritic nanoparticles (nanodendrons) for drug delivery targeted to the tumor microenvironment and with reduced neurotoxicity

Proteinases, including matrix metalloproteinases (MMPs), contribute to cancer progression and other pathologies. Selective MMP expression can be used to distinguish benign from malignant tumors and identify aggressive tumors associated with poor outcome. MMP9, a basement membrane-degrading type-IV collagenase/gelatinase, is associated with tumor invasion and metastasis. In this project, we describe a new class of dendritic nanoparticles, nanodendrons (NDs), with MMP molecular recognition and targeting capabilities. These NDs can be studied as individual dendrons tuned for specific functions such as enhanced imaging or targeted drug treatments. Additionally, the NDs can be coupled to facilitate multifunctional purposes such as in NDs that can self-report drug delivery to tumors. The prototypical system presented here describes NDs that are activated by MMP9: 1) ND-PB, a near infrared imaging beacon; 2) ND-PXL, a therapeutic that delivers paclitaxel (PXL) and 3) NDPB-NDPXL, a bi-functional agent. In vivo studies in two orthotopic models of breast cancer demonstrate efficacy of these NDs to image and treat breast cancer. The proteinase-activated prodrug, NDPXL, delivers PXL to breast cancer through release of the drug in the tumor microenvironment and increases therapeutic efficacy while reducing systemic toxicity (including peripheral neuropathy). The delivery of PXL using the proteolytically activated ND-PXL is effective in inhibiting tumor growth in two orthotopic models of breast cancer (PyVT-R221A and MDA-MB231). Daily treatment of MDA-MB231 tumors with 12.5 mg/kg PXL as either ND-PXL or Abraxane® (Abx), showed similar reduction in tumor growth as compared with vehicle-treated animals. Further investigation of the NDPXL in a fully immunocompetent mouse model (PyVT-R221A) with treatments given on alternate days at a dose of 12.5 mg/kg (ND-PXL or Abx) yielded similar results: an average reduction in tumor growth of 58% and 53% in ND-PXL and Abx cohorts, respectively. Peripheral nerve toxicity, a debilitating, long term side effect of Abx therapy, was assessed in both tumor and non-tumor mice through monitoring behavior indicative of peripheral nerve damage before, during and after administration of each drug. Peripheral neurotoxicity is markedly reduced in the ND-PXL-treated versus Abraxane®-treated mice as evident in a number of behavioral assessments. The development of this novel class of NDs expands upon the current capabilities of modern proteinase-based optical beacons and prodrugs and is a step forward in treatment of both primary and metastatic cancer. [Supported in part by Susan G. Komen for the Cure®]

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1947. doi:1538-7445.AM2012-1947

Reprogramming of mesenchymal stem cells by the synovial sarcoma-associated oncogene SYT-SSX2

Cell identity is determined by its gene expression programs. The ability of a cell to change its identity and produce cell types outside its lineage is achieved by the activity of transcription controllers capable of reprogramming differentiation gene networks. The synovial sarcoma (SS)-associated protein, SYT-SSX2, reprograms myogenic progenitors and human bone marrow-derived mesenchymal stem cells (BMMSCs) by dictating their commitment to a pro-neural lineage. It fulfills this function by directly targeting an extensive array of neural-specific genes as well as genes of developmental pathway mediators. Concomitantly, the ability of both myoblasts and BMMSCs to differentiate into their normal myogenic and adipogenic lineages was compromised. SS is believed to arise in mesenchymal stem cells where formation of the t(X/18) translocation product, SYT-SSX, constitutes the primary event in the cancer. SYT-SSX is therefore believed to initiate tumorigenesis in its target stem cell. The data presented here allow a glimpse at the initial events that likely occur when SYT-SSX2 is first expressed, and its dominant function in subverting the nuclear program of the stem cell, leading to its aberrant differentiation, as a first step toward transformation. In addition, we identified the fibroblast growth factor receptor gene, Fgfr2, as one occupied and upregulated by SYT-SSX2. Knockdown of FGFR2 in both BMMSCs and SS cells abrogated their growth and attenuated their neural phenotype. These results support the notion that the SYT-SSX2 nuclear function and differentiation effects are conserved throughout sarcoma development and are required for its maintenance beyond the initial phase. They also provide the stem cell regulator, FGFR2, as a promising candidate target for future SS therapy.

Increased diacylglycerols characterize hepatic lipid changes in progression of human nonalcoholic fatty liver disease; comparison to a murine model

Background and Aims

The spectrum of nonalcoholic fatty liver disease (NAFLD) includes steatosis, nonalcoholic steatohepatitis (NASH), and progression to cirrhosis. While differences in liver lipids between disease states have been reported, precise composition of phospholipids and diacylglycerols (DAG) at a lipid species level has not been previously described. The goal of this study was to characterize changes in lipid species through progression of human NAFLD using advanced lipidomic technology and compare this with a murine model of early and advanced NAFLD.

Methods

Utilizing mass spectrometry lipidomics, over 250 phospholipid and diacylglycerol species (DAGs) were identified in normal and diseased human and murine liver extracts.

Results

Significant differences between phospholipid composition of normal and diseased livers were demonstrated, notably among DAG species, consistent with previous reports that DAG transferases are involved in the progression of NAFLD and liver fibrosis. In addition, a novel phospholipid species (ether linked phosphatidylinositol) was identified in human cirrhotic liver extracts.

Conclusions

Using parallel lipidomics analysis of murine and human liver tissues it was determined that mice maintained on a high-fat diet provide a reproducible model of NAFLD in regards to specificity of lipid species in the liver. These studies demonstrated that novel lipid species may serve as markers of advanced liver disease and importantly, marked increases in DAG species are a hallmark of NAFLD. Elevated DAGs may contribute to altered triglyceride, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) levels characteristic of the disease and specific DAG species might be important lipid signaling molecules in the progression of NAFLD.

Abstract 390: Increased orthotopic pancreatic tumor cell growth in obese mice

Pancreatic cancer remains one of the eight deadliest cancers due to its late detection and high propensity to metastasize. Increased risk for the development of pancreatic cancer has been associated with obesity, type II diabetes and pancreatitis. The contribution of adipocytes and adipokines to pancreatic cancer progression remains largely unknown and requires further analysis. We hypothesize that increased pancreatic fat compromises the pancreatic microenvironment and increases primary tumor growth as well as metastasis. The condition of non-alcoholic fatty pancreatic disease has been characterized in humans as well as mice and lymph node positive patients were found to have increased pancreatic fat1,2. Adipose secreted cytokines, also known as adipokines, have both been implicated in various aspects of cancer cell survival, growth, and migration. To understand the influence that increased pancreatic fat has on the growth of tumors, both primary and metastatic, we have investigated a high fat diet induced murine model. Male mice fed a 42% fat diet for three months develop increased inter-pancreatic and intra-pancreatic fat as well as acute localized pancreatitis when compared to mice fed a 13% fat diet. To test the affect of pancreatic fat on tumor cells, we used an orthotopic tumor injection model to determine the rate of primary tumor growth and progression to metastasis. Further, we are implementing the use of Panc02-luciferase tagged cells to monitor and measure pancreatic tumor growth over time and to detect the presence of metastases in the liver and/or lungs. Preliminary evidence has confirmed that orthotopic tumors grown in obese mice led to an increased tumor size as well as massive expansion of tumor cells into the interpancreatic fat. In conclusion, increased pancreatic fat promotes the growth of orthotopically implanted murine tumor cells, yet the molecular mechanisms remain undetermined.

1. Mathur, A. et al. J Am Coll Surg. 2009 May;208(5):989-94.

2. Mathur, A. et al. HPB (Oxford). 2007;9(4):312-8.

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 390. doi:10.1158/1538-7445.AM2011-390

Abstract LB-378: Establishment of hepatic metastases in a steatotic microenvironment is enhanced by stromal derived MMP-12

Non-alcoholic fatty liver disease (NAFLD), encompassing steatosis and progression to non-alcoholic steatohepatitis (NASH) are liver disorders of increasing clinical significance. We have shown that hepatic steatosis establishes a permissive microenvironment for metastatic seeding and tumor progression in the liver. We have identified MMP-12 (macrophage metalloelastase) as an important molecular component associated with hepatic steatosis and steatohepatitis. Wildtype mice in the C57Bl/6 background were fed a 42% fat diet for three months to induce hepatic steatosis. Affymetrix microarray analysis was performed on steatotic vs. normal murine livers to determine candidate genes altered between these liver microenvironments. Our results noted 715 significant changes in gene expression, of which matrix metalloproteinase 12 was among the most significantly up regulated genes in the steatotic microenvironment. Importantly, we have detected an upregulation of MMP-12 in human steatotic and steatohepatitis samples. MMP-12 deficient mice gained weight and developed diet-induced hepatic steatosis similar to wildtype mice. To determine whether MMP-12 affected metastasis, normal and steatotic MMP-12 deficient mice were tested with an experimental metastasis model via splenic injection of MC38 tumor cells. The number of resultant tumors per unit of tissue area in wildtype steatotic livers showed a 25 fold increase compared to tumors in MMP-12 deficient mice. Comparison of tumors between regular diet livers in wildtype and MMP12−/−mice was not significant. Immunohistochemical staining for F4/80 showed a reduction in the number of positive cells in MMP-12 deficient steatotic livers.

Conclusions: Modulation of host factors is known to be important in tissue/site specific susceptibility to cancer metastases. MMP-12 can influence immune-mediated injury response by processing latent TNF alpha and regulating macrophage recruitment. Upregulation of matrix metalloproteinase 12 suggest a role for this protease in inflammatory mediated events in the distinct microenvironments of steatosis and steatohepatitis. The molecular mechanisms underlying the decreased establishment of metastatic tumors in MMP-12 deficient mice requires further investigation.

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 LB-378.

Optical imaging of matrix metalloproteinase-7 activity in vivo using a proteolytic nanobeacon

Matrix metalloproteinases (MMPs) are extracellular proteolytic enzymes involved in tumor progression. We present the in vivo detection and quantitation of MMP7 activity using a specific near-infrared polymer-based proteolytic beacon, PB-M7NIR. PB-M7NIR is a pegylated polyamidoamine PAMAM-Generation 4 dendrimer core covalently coupled to a Cy5.5-labeled peptide representing a selective substrate that monitors MMP7 activity (sensor) and AF750 as an internal reference to monitor relative substrate concentration (reference). In vivo imaging of tumors expressing MMP7 had a median sensor to reference ratio 2.2-fold higher than a that of a bilateral control tumor. Ex vivo imaging of intestines of multiple intestinal neoplasia (APC Min) mice injected systemically with PB-M7NIR revealed a sixfold increase in the sensor to reference ratio in the adenomas of APC Min mice compared with control intestinal tissue or adenomas from MMP7-null Min mice. PB-M7NIR detected tumor sizes as small as 0.01 cm2, and the sensor to reference ratio was independent of tumor size. Histologic sectioning of xenograft tumors localized the proteolytic signal to the extracellular matrix; MMP7-overexpressing tumors displayed an approximately 300-fold enhancement in the sensor to reference ratio compared with nonexpressing tumor cells. In APC Min adenomas, the proteolytic signal colocalized with the endogenously expressed MMP7 protein, with sensor to reference ratios approximately sixfold greater than that of normal intestinal epithelium. PB-M7NIR provides a useful reagent for the in vivo and ex vivo quantitation and localization of MMP-selective proteolytic activity.

Matrix metalloproteinases and cellular motility in development and disease

The movement of cells and the accompanied remodeling of the extracellular matrix is a critical step in many developmental processes. The matrix metalloproteinases (MMPs) are well recognized as mediators of matrix degradation, and their activity as regulators of signaling pathways by virtue of the cleavage of nonmatrix substrates has been increasingly appreciated. In this review, we focus on the role of MMPs in altering processes that influence cellular motility. MMP involvement in cellular adhesion, lamellipodia-directed movement, invadopodial protrusion, axonal growth cone extension, and chemotaxis are discussed. Although not designed to be comprehensive, these examples clearly demonstrate that cellular regulation of the MMPs influences cell motility in a variety of ways, including regulating cell-cell interactions, cell-matrix interactions, matrix degradation, and the release of bioactive signaling molecules. Deregulation of these interactions can ultimately result in disorders including inflammatory diseases, vascular diseases, bone diseases, neurological disorders, and cancer.