Human Pancreatic Ductal Adenocarcinoma Tumors Research Articles

Abstract 7217: Orthogonal targeting of NAD metabolism and ErbB2/ErbB3 signaling in pancreatic adenocarcinoma

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is now the third leading cause for cancer related deaths in the US with a five-year survival of ~10% that has improved little over the past 20 years. Thus, there is a critical need to fully understand mechanisms of PDAC tumorigenesis in order to develop novel and effective therapies. Nicotinamide Adenine Dinucleotide (NAD), a critical co-factor and energy source required for cellular processes such as DNA repair and epigenetic regulation is frequently upregulated in PDAC. We recently reported a novel oncogenic axis connecting the NAD-dependent epigenetic regulator and oncogene C-terminal Binding Protein (CtBP) with the EGFR family growth factor receptors ErbB2/ErbB3 (ErbB2/3) in PDAC cells and tumors. Indeed, previous reports have shown ~30% of human PDAC tumors overexpress ErbB3, and our work has shown that PDAC tumor cell growth relies on maintenance of ErbB3 expression. Moreover, we show that the majority of PDAC cells with high levels of ErbB3 expression are uniquely sensitive to the ErbB2-targeted tyrosine kinase inhibitor lapatinib. In addition, we have recently shown that co-targeting NAD and CtBP with small molecule inhibitors is an effective and synergistic therapeutic strategy in PDAC model systems. Methods and Results: In the current study, we demonstrate NAD-dependent regulation of ErbB2/3 signaling in PDAC cells in vitro. Upon depletion of NAD using the NAD salvage pathway inhibitor GMX1778 in human PDAC cells, we observed a striking coordinate decrease in the levels of both ErbB2 and ErbB3. Furthermore, stable knockdown of the limiting enzyme of the complementing Preiss-Handler NAD synthetic pathway, Nicotinamide Adenine Phosphoribosyl Transferase, also resulted in robust downregulation of ErbB2/3 protein levels, suggesting a direct linkage in PDAC cells between the status of NAD metabolism and synthesis and activity of the key growth factor receptors ErbB2/3. Conclusions: Our findings highlight the novel connection between NAD and ErbB2/3 in PDAC. Furthermore, our data suggests combining chemical or biologic inhibitors of ErbB2/3 with an inhibitor of NAD synthesis may result in highly synergistic cytotoxic effects in PDAC cells and PDAC preclinical models. Such data could support the future development of a human PDAC clinical trial repurposing agents targeting NAD synthesis and ErbB2/3 that are already FDA-approved or currently in clinical testing. Citation Format: Kranthi Kumar Chougoni, Nari Kim, Martin M. Dcona, Diana T. Dcona, Gautam K. Malhotra, Steven R. Grossman. Orthogonal targeting of NAD metabolism and ErbB2/ErbB3 signaling in pancreatic adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7217.

Abstract A054: PP2A activation alters macropinosome processing in pancreatic cancer cells leading to metabolic stress and cancer cell death

Abstract The majority of pancreatic ductal adenocarcinoma (PDAC) patients present with late-stage, metastatic disease that is often resistant to therapeutics, resulting in the lowest survival rate of all major cancers. Metabolic rewiring in response to oncogenic signals plays a critical role in PDAC cell survival, tumor growth, and metastasis. In contrast to normal epithelial cells, these metabolic alterations make PDAC tumors dependent on glutamine for survival, highlighting a unique metabolic vulnerability that can be therapeutically exploited. However, during times of nutrient stress, PDAC cells can circumvent this vulnerability by engulfing extracellular fluids to replenish amino acids, including glutamine, in a process called, macropinocytosis. Macropinocytosis occurs downstream of oncogenic KRAS, a small GTPase that is almost universally mutated in PDAC patients. The inhibition of macropinocytosis in vivo reduces PDAC tumor growth, underscoring the importance of this pathway to cancer cell survival. However, the signaling mechanisms that regulate this process and the contribution of macropinocytic signaling to aggressive cancer phenotypes remains poorly understood. Protein phosphatase 2A (PP2A) is a heterotrimeric complex that regulates a wide variety of cell signaling pathways, including KRAS, and is commonly deregulated in human PDAC tumors. Recently, PP2A has been implicated as an important regulator of macropinocytosis, but the mechanism by which this occurs is unknown. We demonstrate that the genetic loss of the specific PP2A subunit, B56a, accelerates the formation of KRAS-driven pancreatic lesions in an in vivo mouse model, implicating this subunit as a critical negative regulator of KRAS phenotypes during PDAC progression. Here, we show that acute PP2A-B56a activation prevents the fusion of macropinosomes with lysosomes, robbing PDAC cells of critical metabolic nutrients and driving cell death. Consistent with these findings, PP2A activation also reduces glutamine levels and suppresses oxidative phosphorylation. Finally, we determined that PP2A activating compounds can function synergistically with metabolic inhibitors, supporting a new therapeutic strategy in this aggressive and deadly cancer. Together, our results implicate PP2A as a critical suppressor of PDAC metabolic plasticity and highlight the use of PP2A activating compounds to prevent PDAC nutrient scavenging. Citation Format: Garima Baral, Claire M. Pfeffer, Indiraa Doraivel, Brittany L. Allen-Petersen. PP2A activation alters macropinosome processing in pancreatic cancer cells leading to metabolic stress and cancer cell death [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A054.

Abstract C014: CXCR4 inhibition enhances anti-tumor immune response in an ex vivo autologous patient-derived organoids and PBMC model system of pancreatic ductal adenocarcinoma

Abstract Introduction Immune checkpoint blockade either alone or in combination with chemotherapy has been ineffective in pancreatic ductal adenocarcinoma (PDAC) likely due to underlying immunosuppressive pathways. The CXC chemokine receptor type 4 (CXCR4)/chemokine (CXC motif) ligand 12 (CXCL12) axis is one key immunosuppressive pathway. CXCL12 (released by cancer-associated fibroblasts (CAF)) binds to CXCR4 on CD8+ T cells (CTL) and decreases its infiltration into the tumor. Encouraging preclinical studies from murine PDAC models and human PDAC tumor sections have demonstrated infiltration of T cells with tumors after co-inhibition of CXCR4 and PD1/PDL1, however with limited tumor regressions in mouse model. We established an innovative ex vivo autologous patient-derived immune/organoid (PDIO) co-culture system that allows studying the interactions between distinct immune cells and tumor cells. Methods Patient-derived tumor organoids (PDTOs) generated from tumors resected from patients diagnosed with pancreas cancer were grown to confluence in Matrigel domes. We conducted ex vivo migration assays with autologous peripheral blood mononuclear cells (PBMCs) which were placed in the surrounding liquid phase of the matrigels. We separately treated PBMCs and PDTOs with AMD3100, an inhibitor of CXCR4, and tested the role of CXCR4 inhibition on PBMCs and PDTOs in T cell exclusion and immune cell activation. Results Pre-treatment of PBMCs with AMD3100 increased CD8+ T cell mobilization towards autologous PDTOs in matrigel dome migration assays by up to 11-fold. After co-culture in the liquid interphase of PDTOs matrigel domes, AMD3100 pre-treated PBMCs exhibit a more robust proliferative response compared to untreated PBMCs and a significant increase in the number of reactive T cells migrated inside the PDTO matrigel dome and expressing activation markers (p=0.02). Nearly 50% of T cells in proximity of tumor cells produce the cytotoxic factor Granzyme B (p=0.002), with AMD3100 treatment of PBMC increasing it by up to 3-fold compared to untreated PBMC. CXCR4 inhibition of PDTOs resulted in modulation of immune checkpoint ligands involved in the tumor immune response and tumor cell immunogenicity. Combination treatment of PBMCs and PDTOs with AMD3100 and anti-PD1 antibody ultimately resulted in increased tumor cell death with up to 45% of PDTOs exhibiting apoptosis markers after coculture with AMD3100-treated PBMC, implicating a role of this combination in the clinic. Conclusions We demonstrate that inhibition of CXCR4, not only increases migration of autologous T cells towards PDTOs, but also results in proliferation of PBMCs and activation of T cells. Furthermore, CXCR4 inhibition of PDTOs increases antigen presentation and tumor cell death. Inhibition of CXCR4 is an attractive therapeutic target as it enhances anti-tumor immune response via dual targeting of immune and neoplastic compartments. We are testing this combination in a multicenter investigator-initiated clinical trial in treatment-naïve metastatic PDAC patients. Citation Format: Ilenia Pellicciotta. CXCR4 inhibition enhances anti-tumor immune response in an ex vivo autologous patient-derived organoids and PBMC model system of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C014.

Association between SMAD4 Mutations and GATA6 Expression in Paired Pancreatic Ductal Adenocarcinoma Tumor Specimens: Data from Two Independent Molecularly-Characterized Cohorts.

Several molecular biomarkers have been identified to guide induction treatment selection for localized pancreatic ductal adenocarcinoma (PDAC). SMAD4 alterations and low GATA6 expression/modified "Moffitt" basal-like phenotype have each been associated with inferior survival uniquely for patients receiving 5-FU-based therapies. SMAD4 may directly regulate the expression of GATA6 in PDAC, pointing to a common predictive biomarker. To evaluate the relationship between SMAD4 mutations and GATA6 expression in human PDAC tumors, patients with paired SMAD4 mutation and GATA6 mRNA expression data in the TCGA and CPTAC were identified. In 321 patients (TCGA: n = 180; CPTAC: n = 141), the rate of SMAD4 alterations was 26.8%. The rate of SMAD4 alteration did not vary per tertile of normalized GATA6 expression (TCGA: p = 0.928; CPTAC: p = 0.828). In the TCGA, SMAD4 alterations and the basal-like phenotype were each associated with worse survival (log rank p = 0.077 and p = 0.080, respectively), but their combined presence did not identify a subset with uniquely inferior survival (p = 0.943). In the CPTAC, the basal-like phenotype was associated with significantly worse survival (p < 0.001), but the prognostic value was not influenced by the combined presence of SMAD4 alterations (p = 0.960). SMAD4 alterations were not associated with poor clinico-pathological features such as poor tumor grade, advanced tumor stage, positive lymphovascular invasion (LVI), or positive perineural invasion (PNI), compared with SMAD4-wildtype. Given that SMAD4 mutations were not associated with GATA6 expression or Moffitt subtype in two independent molecularly characterized PDAC cohorts, distinct biomarker-defined clinical trials are necessary.

Osteopontin secreted from obese adipocytes enhances angiogenesis and promotes progression of pancreatic ductal adenocarcinoma in obesity.

Obesity is a risk factor and poor prognostic factor for pancreatic ductal adenocarcinoma (PDAC), but the underlying mechanisms remain unclear. PDAC cells and obese visceral adipocytes (O-Ad) derived from mice and humans were used to analyze interactions between the two cell types, and human microvascular endothelial cells were used for angiogenesis assay. A xenograft mouse model with subcutaneously injected PDAC cells was used for animal studies. The relationship between visceral fat and prognosis was analyzed using resected tissues from PDAC patients with and without obesity. Conditioned media (CM) from O-Ad significantly increased PDAC cell growth and migration and angiogenic capacity in both human and mice cells, and blocking osteopontin (OPN) in O-Ad canceled O-Ad-induced effects in both mouse and human cells. In addition, O-Ad directly increased the migratory and tube-forming capacities of endothelial cells, while blocking OPN canceled these effects. O-Ad increased AKT phosphorylation and VEGFA expression in both PDAC and endothelial cells, and OPN inhibition in O-Ad canceled those O-Ad-induced effects. In the xenograft model, PDAC tumor volume was significantly increased in obese mice compared with lean mice, whereas blocking OPN significantly inhibited obesity-accelerated tumor growth. OPN expression in adipose tissues adjacent to human PDAC tumor was significantly higher in obese patients than in non-obese patients. In PDAC patients with obesity, high OPN expression in adipose tissues was significantly associated with poor prognosis. Obese adipocytes trigger aggressive transformation in PDAC cells to induce PDAC progression and accelerate angiogenesis via OPN secretion.

Resistance to Gemcitabine in Pancreatic Cancer Is Connected to Methylglyoxal Stress and Heat Shock Response

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease with poor prognosis. Gemcitabine is the first-line therapy for PDAC, but gemcitabine resistance is a major impediment to achieving satisfactory clinical outcomes. This study investigated whether methylglyoxal (MG), an oncometabolite spontaneously formed as a by-product of glycolysis, notably favors PDAC resistance to gemcitabine. We observed that human PDAC tumors expressing elevated levels of glycolytic enzymes together with high levels of glyoxalase 1 (GLO1), the major MG-detoxifying enzyme, present with a poor prognosis. Next, we showed that glycolysis and subsequent MG stress are triggered in PDAC cells rendered resistant to gemcitabine when compared with parental cells. In fact, acquired resistance, following short and long-term gemcitabine challenges, correlated with the upregulation of GLUT1, LDHA, GLO1, and the accumulation of MG protein adducts. We showed that MG-mediated activation of heat shock response is, at least in part, the molecular mechanism underlying survival in gemcitabine-treated PDAC cells. This novel adverse effect of gemcitabine, i.e., induction of MG stress and HSR activation, is efficiently reversed using potent MG scavengers such as metformin and aminoguanidine. We propose that the MG blockade could be exploited to resensitize resistant PDAC tumors and to improve patient outcomes using gemcitabine therapy.

Abstract 3627: Inhibition of tumor cell-autonomous p38 MAPK suppresses IL1α-mediated inflammatory tumor-stromal crosstalk in pancreatic adenocarcinoma

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) continues to face major therapeutic challenges due to its innate and acquired chemoresistance. Oncogenic, activating KRAS mutations facilitate extensive cytokine-mediated crosstalk between tumor cells and the fibrotic stroma, producing a pro-inflammatory and immunosuppressive tumor microenvironment (TME). We have identified interleukin-1α (IL1α), downstream of KRAS, as a critical mediator of the inflammatory response due to its pleiotropic effects on cancer-associated fibroblast (CAF) activation and immune evasion. However, the regulatory mechanisms of IL1α expression remain incompletely understood. We identified p38 stress-associated MAPK α (p38α) as a central, KRAS-driven regulatory pathway involved in IL1α production within PDAC tumor cells. Methods: Differential gene expression analyses were performed on patient data from The Cancer Genome Atlas (TCGA) was queried for overactive pathways downstream KRAS in “high-IL1A” PDAC cases. Inhibition of p38α was achieved pharmacologically with pexmetinib and genetically with an shRNA lentiviral system in human and murine PDAC cell lines. ChIP-qPCR and co-immunoprecipitation were performed on a human PDAC cell line with and without p38α inhibition. Single-cell RNA sequencing (scRNA-seq) and flow cytometry were performed on tumors from a PDAC murine model, Ptf1aCre/+; LSL-KrasG12D/+; Tgfbr2flox/flox (PKT), treated with or without pexmetinib. PKT mice were treated daily with pexmetinib, gemcitabine and paclitaxel chemotherapy, or combination therapy for downstream analysis and survival studies. Results: Both pharmacologic and genetic inhibition of p38α significantly reduced IL1A transcription and protein levels in human and murine PDAC tumor cell lines. Furthermore, p38α inhibition reduced binding of Sp1 and NF-κB to the IL1A promoter and prevented IL1α-mediated polarization of inflammatory CAFs in vitro. In PKT mice, p38α inhibition reduced tumor cell-specific Il1a and inflammatory CAF gene signatures by scRNA-seq, and favorably altered the infiltrating immune populations by flow cytometry. Lastly, pexmetinib with chemotherapy significantly reduced tumor burden and improved overall survival in a PDAC murine model. Conclusions: These findings provide a new therapeutic opportunity to target the p38α MAPK pathway for suppression of IL1α-mediated stromal activation and combination with chemotherapy to overcome therapeutic resistance by modulating the stromal and immune microenvironment in PDAC. Citation Format: Samara Singh, Austin R. Dosch, Siddharth Mehra, Iago de Castro Silva, Anna Bianchi, Vanessa Tonin Garrido, Zhiqun Zhou, Haleh Amirian, Edmond W. Box, Jashodeep Datta, Nagaraj Nagathihalli, Nipun B. Merchant. Inhibition of tumor cell-autonomous p38 MAPK suppresses IL1α-mediated inflammatory tumor-stromal crosstalk in pancreatic adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3627.

Abstract 4140: Oncogenic KRAS inhibition with ADT-007 primes T cell responses in pancreatic ductal adenocarcinoma

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) has low (&amp;lt;11%) 5-year survival due to the presence of advanced disease at diagnosis. Currently standard of care provides a median survival of 1 year in the majority of patients presenting with advanced disease. Targeting oncogenic KRAS, which is mutated in &amp;gt;90% of human PDAC tumors, provides an opportunity to inhibit a critical pathway and significantly impact standard of care in patients diagnosed with PDAC. Furthermore, evidence indicates that inhibiting-oncogenic KRAS signaling modulates anti-tumor immune responses and demonstrates synergy with immune checkpoint blockade in pre-clinical models. The purpose of this study is to evaluate efficacy and impact on anti-tumor immunity of a novel inhibitor, ADT-007 that demonstrates pan-RAS inhibitory activity. Methods: Female C57BL/6J, C57BL/6J. Ifng/Thy1.1 KI;Cg-Tg-IL2tm1/eGFP/Weav (IFNg-Thy1.1/IL-2-GFP reporter mice), or immune deficient (T/B cells) Rag 1 −/− mice (n=5-10/group) were implanted SQ with 106 mouse derived PDAC cell lines (7160c2 and 2838c3) bearing KRASG12D mutation, and then randomized (day 7), into vehicle (5% DMSO/5% Kolliphor/90% H2O) or ADT-007 treatment, which was administered SQ (peritumoral), BID at 5 mg/kg for 2 - 3 weeks. Tumor growth in vitro (IC50), KRAS-MAPK/AKT signaling, in vivo tumor volumes (tv = L x W2/2), and tumor immune responses were assessed by CellTiter Glo, phosphoflow/western blotting, bi-weekly caliper measurements, and multi-parameter flow cytometry, respectively. Results: ADT-007 inhibited KRAS-MAPK/AKT signaling in human and mouse PDAC cell lines inducing G2-M phase arrest and apoptosis at low nanomolar concentrations. Peritumoral administration of ADT-007 inhibited tumor cell growth in vivo, modulating T cells in the tumor microenvironment (TME), specifically, an increase in tumor infiltrating, CD44+ CD62L− CD4+ and CD8+ T cells and increases in production of TNFα, IFN-γ, IL-2, and granzyme B upon stimulation with PMA/ionomycin. Conclusion: The small molecule inhibitor, ADT-007 blocks oncogenic KRAS signaling and modulates T cell activation and function in the TiME of immune competent, syngeneic mouse models of PDAC. More broadly, these findings indicate that a pan-RAS inhibitor is capable of modulating anti-tumor immune responses extending previous observations that targeted inhibition of oncogenic KRASG12C modulates tumor immunity in animal models of colon and lung cancer. Citation Format: Jeremy B. Foote, Tyler E. Mattox, Adam B. Keeton, Ganji N. Purnachandra, Yulia Maxuitenko, Xi Chen, Jacob Valiyaveettil, Donald J. Buchsbaum, Gary A. Piazza, Bassel F. El-Rayes. Oncogenic KRAS inhibition with ADT-007 primes T cell responses in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4140.

The divergent role of the GM-CSF/GM-CSFR signaling pathway in cholangiocarcinoma and pancreatic ductal adenocarcinoma.

736 Background: The granulocyte-macrophage colony-stimulating factor ligand and receptor (GM-CSF/GM-CSFR) pathway plays a multifaceted role in the setting of cancer, exerting an anti-tumorigenic or pro-tumorigenic effect depending on GM-CSF expression. In previous work, we and others have shown increased GM-CSF expression to correlate with poor prognosis in patients with cholangiocarcinoma (CCA) and pancreatic ductal adenocarcinoma (PDAC). We also demonstrated how GM-CSF neutralization leads to reduced tumor size in murine CCA models, in part due to inhibition of alternative macrophage polarization. Here, we explore the impact of blocking GM-CSFR signaling in CCA and PDAC, two immunologically cold tumors with poor prognoses. Methods: Immunohistochemistry (IHC) and digital quantification of staining was performed on tissue from a human PDAC and CCA databank. Murine F4/80+ bone marrow-derived macrophages were cultured in tumor-conditioned media (TCM) derived from PDAC (KP2) or CCA (URCCA4.3) cell lines, with and without anti-GM-CSFR antibody. Quantitative real time PCR (qRT-PCR) analysis was performed for gene expression. URCCA4.3 and a luciferase-labeled PDAC (KCKO) cell line were orthotopically implanted into Bc/BIL3 knockout (KO) mice which lack GM-CSFR and C57BL/6 mice. Mice implanted with URCCA4.3 were enrolled into vehicle or gemcitabine treatment groups. Mice implanted with KCKO were untreated. Tumor growth was monitored by ultrasonography or bioluminescence imaging. Results: Digital analysis of IHC staining for GM-CSFR in human PDAC tumors revealed low expression to be associated with improved overall survival (OS) and greater number of days to recurrence, while high levels were associated with worse OS and fewer days to recurrence (p&lt;0.01). In addition, human CCA specimens had greater GM-CSFR expression compared to normal uninvolved liver (p&lt;0.01). qRT-PCR analysis of RNA from bone marrow-derived macrophages exposed to either CCA or PDAC TCM demonstrated lower expression of genes associated with alternative macrophage polarization ( Arg1, Cd274, Pdcd1lg2) and chronic inflammation ( Ccl2, Ccl17, Irf4) (all p&lt;0.01) in response to GM-CSFR blockade. GM-CSFR KO mice implanted with URCCA4.3 demonstrated no differences in tumor growth with or without chemotherapy, compared to wild-type controls. Similarly, KO mice implanted with an immunogenic PDAC cell line (KCKO) had no differences in tumor size compared to wild-type controls. Conclusions: GM-CSFR expression is prognostic in the setting of PDAC and elevated in human CCA compared to normal liver. In vitro, GM-CSFR blockade downregulated pro-tumor genes associated with immunosuppression and inflammation. However, complete disruption of GM-CSFR signaling reversed the efficacy generated with GM-CSF ligand neutralization, suggesting some signaling is required for inducing anti-tumor immune responses.

Association between SMAD4 mutations and GATA6 expression in pancreatic adenocarcinoma specimens

Background: Molecular biomarkers may guide systemic treatment for localized pancreatic ductal adenocarcinoma (PDAC). SMAD4 somatic alterations have been associated with inferior clinical outcomes during induction FOLFIRINOX. Additionally, low GATA6 mRNA expression have been associated with inferior clinical outcomes amongst patients receiving 5-FU/LV. In cell-based assays, SMAD4 can directly regulate the expression of GATA6, suggesting that SMAD4 alterations at the genomic level and loss of GATA6 expression may represent a single molecular pathway that confers unique resistance to 5-FU-based therapies. The relationship between SMAD4 mutations and GATA6 expression has not been previously studied in human PDAC tumor samples.

CD73 Inhibits cGAS-STING and Cooperates with CD39 to Promote Pancreatic Cancer.

The ectonucleotidases CD39 and CD73 catalyze extracellular ATP to immunosuppressive adenosine, and as such, represent potential cancer targets. We investigated biological impacts of CD39 and CD73 in pancreatic ductal adenocarcinoma (PDAC) by studying clinical samples and experimental mouse tumors. Stromal CD39 and tumoral CD73 expression significantly associated with worse survival in human PDAC samples and abolished the favorable prognostic impact associated with the presence of tumor-infiltrating CD8+ T cells. In mouse transplanted KPC tumors, both CD39 and CD73 on myeloid cells, as well as CD73 on tumor cells, promoted polarization of infiltrating myeloid cells towards an M2-like phenotype, which enhanced tumor growth. CD39 on tumor-specific CD8+ T cells and pancreatic stellate cells also suppressed IFNγ production by T cells. Although therapeutic inhibition of CD39 or CD73 alone significantly delayed tumor growth in vivo, targeting of both ectonucleotidases exhibited markedly superior antitumor activity. CD73 expression on human and mouse PDAC tumor cells also protected against DNA damage induced by gemcitabine and irradiation. Accordingly, large-scale pharmacogenomic analyses of human PDAC cell lines revealed significant associations between CD73 expression and gemcitabine chemoresistance. Strikingly, increased DNA damage in CD73-deficient tumor cells associated with activation of the cGAS-STING pathway. Moreover, cGAS expression in mouse KPC tumor cells was required for antitumor activity of the CD73 inhibitor AB680 in vivo. Our study, thus, illuminates molecular mechanisms whereby CD73 and CD39 seemingly cooperate to promote PDAC progression.

Abstract C019: FAK suppresses antigen processing and presentation to promote immune evasion in pancreatic cancer

Abstract Immunotherapy for the treatment of Pancreatic Ductal Adenocarcinoma (PDAC) has shown limited efficacy. Poor CD8 T-cell infiltration, low neoantigen load and a highly immunosuppressive tumor microenvironment are key factors that contribute to this lack of response. Here, we identify a novel role for Focal Adhesion Kinase (FAK) in regulating type-II interferon signalling in human and murine PDAC cells and tumors, leading to suppression of antigen processing and presentation pathways critical for T-cell tumor recognition. We find that FAK loss promotes expression of the immunoproteasome and MHC-I, resulting in a significant increase in the diversity of antigens presented by FAK-/- PDAC cells. We show that regulation of the immunoproteasome subunit Psmb8 (β5i) is a critical determinant of this response, optimising the physicochemical properties of the peptide repertoire for high-affinity binding to MHC-I. Expression of the immunoproteasome and MHC-I can be further amplified in a STAT1-dependent manner via co-depletion of FAK and STAT3, leading to extensive CD8 T-cell infiltration into PDAC tumors and further restraint of tumor growth. Regulation of antigen processing and presentation by FAK preferentially occurs in human and murine PDAC cells and tumors of the classical/progenitor molecular subtype, further suggesting that precision medicine approaches based on molecular subtyping should be integrated into current and future clinical testing of FAK targeted therapies for the treatment of pancreatic cancer. Citation Format: Marta Canel, Aleksandra Slawinska, David W. Lonergan, Ashwin A. Kallor, Rosie Upstill-Goddard, Catherine Davidson, Alex von Kriegsheim, Andrew V. Biankin, Adam Bryron, Javier Alfaro, Alan Serrels. FAK suppresses antigen processing and presentation to promote immune evasion in pancreatic cancer [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 C019.

Abstract C007: Targeting vasoactive intestinal peptide receptor signaling enhances T-cell mediated anti-tumor response to immune checkpoint therapy in pancreatic ductal adenocarcinoma

Abstract Current immune checkpoint therapies including anti-CTLA-4 and anti-PD1 have limited efficacy in the treatment of pancreatic ductal adenocarcinoma (PDAC), largely due to a paucity of effector T cells within the tumor microenvironment (TME). In our study, we show that vasoactive intestinal peptide (VIP), an immunosuppressive neuropeptide, is over-expressed in human PDAC tumors. Thus, we hypothesized that paracrine production of VIP by tumor cells within the PDAC TME constitutes an immune checkpoint pathway that limits the antitumor activity of VIP-receptor (VIP-R) expressing T cells. We first evaluated whether inhibiting VIP-R signaling by peptide-based VIP-R antagonist affects the growth of PDAC cells in vitro. Treatment of PDAC cells with increasing concentrations of VIP-R antagonist did not affect the viability of PDAC cell lines in vitro, except for a transient effect in MT5 albeit not significant. Furthermore, depletion of VIP receptor 2 (VPAC2) in a PDAC cell line, Panc02, by CRISPR-Cas9 KO had similar growth rates in vitro with a slight growth delay in vivo compared to the parental cell line. These data suggest that the expression of VPAC2 on PDAC cells may not confer a significant autocrine effect on tumor growth impacted by VIP signaling. On the contrary, human T cells cultured with VIP-R antagonists had enhanced activation, decreased proportions of Tregs, and exhausted T cells co-expressing PD-1, Tim-3, and Lag-3. Next, we performed pharmacological inhibition with VIP-R antagonists in tumor-bearing mice to model T cell homing, activation, and antitumor responses in preclinical murine models of PDAC. Daily subcutaneous injections of VIP-R antagonists had synergistic antitumor activity when combined with anti-PD-1 therapy with decreased tumor burden and improved survival. In contrast to the limited single-agent activity of anti-PD1 or VIP-R antagonists, combination therapy eliminated tumors in up to 40% of animals. Anti-tumor responses were T cell-dependent, as the combination therapy failed to improve survival in CD4 or CD8 deficient mice using knock-out strains and antibody depletion. In addition, tumor-free mice were resistant to tumor re-challenge, indicating the generation of anti-cancer immunological memory. In correspondent to these data, combination therapy led to enhanced T cell activation in vivo with increased antigen-specific T cells, decreased frequencies of Tregs as well as enhanced T cell infiltration to the tumor site as observed by infiltration of adoptively transferred GFP+ T cells into PDAC tumors. Taken together, our findings show that VIP-VIPR signaling is a targetable mechanism of immune escape in PDAC. Inhibiting VIP-R signaling improves T cell effector properties and enhances the responsiveness of PDAC to immune checkpoint therapy. Further pharmacokinetic and toxicology studies are underway. Citation Format: Tenzin Passang, Sruthi Ravindranathan, Jian-Ming Li, Shuhua Wang, Michael Brandon Ware, Hanwen Zhang, Gregory B. Lesinski, Edmund K. Waller. Targeting vasoactive intestinal peptide receptor signaling enhances T-cell mediated anti-tumor response to immune checkpoint therapy in pancreatic ductal adenocarcinoma [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 C007.

Abstract C058: Remodeling the tumor microenvironment by targeting integrin alpha V beta 3 (αvβ3) expressing cells in pancreatic cancer

Abstract ProAgio is a therapeutic cytotoxin that targets and kills integrin αvβ3-expressing cells, resulting in reduced tumor collagen, decreased formation of new blood vessels in the tumor microenvironment (TME), and prolonged survival in mouse models of pancreatic ductal adenocarcinoma (PDAC). ProAgio is currently being tested in a Phase 1 dose-finding study in patients with solid tumors including pancreas cancers. The cell subsets within the PDAC TME that express integrin αvβ3 and could be subject to ProAgio-mediated killing have not been previously studied. Using the KPC genetically engineered mouse model of PDAC, we found that ProAgio (20 mg/kg daily, x7 days) restrained tumor growth by 20% compared to vehicle treatment without changing the cancer cell proliferation rate. We subsequently re-analyzed publicly available scRNA-seq PDAC datasets to identify cells present in human and mouse PDAC tumors that co-express integrins αv and β3 and could be targets of ProAgio. We found that specific subsets of cancer-associated fibroblasts (CAFs), monocytes and macrophages expressed both integrins. Flow cytometry was performed on cells dissociated from orthotopically implanted KPC-derived tumors treated for 15 days with ProAgio or vehicle to identify TME subsets affected by ProAgio treatment. There was no significant difference in the myofibroblast (myCAF) subset, but an increase in the percentage of inflammatory CAFs (iCAFs) was seen. ProAgio treatment also significantly increased the percentage of conventional dendritic cells which play a pivotal role in antigen recognition and T cell priming. T cell abundance was unchanged, but a decrease in B cells was observed. These data demonstrate that ProAgio treatment modifies specific immune and fibroblast subsets within the PDAC TME. Ongoing studies seek to further delineate the cell subtypes affected by ProAgio and the cytokine and chemokine mediators responsible for these changes. Citation Format: Mayrel Palestino Dominguez, Philip Homan, Xianyu Zhang, Sandra Navas Reyes, Theresa Guerin, Laura Bassel, Zhi-ren Liu, Serguei Kozlov, Christine Alewine. Remodeling the tumor microenvironment by targeting integrin alpha V beta 3 (αvβ3) expressing cells in pancreatic cancer [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 C058.

Targeting vasoactive intestinal peptide-mediated signaling enhances response to immune checkpoint therapy in pancreatic ductal adenocarcinoma

A paucity of effector T cells within tumors renders pancreatic ductal adenocarcinoma (PDAC) resistant to immune checkpoint therapies. While several under-development approaches target immune-suppressive cells in the tumor microenvironment, there is less focus on improving T cell function. Here we show that inhibiting vasoactive intestinal peptide receptor (VIP-R) signaling enhances anti-tumor immunity in murine PDAC models. In silico data mining and immunohistochemistry analysis of primary tumors indicate overexpression of the neuropeptide vasoactive intestinal peptide (VIP) in human PDAC tumors. Elevated VIP levels are also present in PDAC patient plasma and supernatants of cultured PDAC cells. Furthermore, T cells up-regulate VIP receptors after activation, identifying the VIP signaling pathway as a potential target to enhance T cell function. In mouse PDAC models, VIP-R antagonist peptides synergize with anti-PD-1 antibody treatment in improving T cell recruitment into the tumors, activation of tumor-antigen-specific T cells, and inhibition of T cell exhaustion. In contrast to the limited single-agent activity of anti-PD1 antibodies or VIP-R antagonist peptides, combining both therapies eliminate tumors in up to 40% of animals. Furthermore, tumor-free mice resist tumor re-challenge, indicating anti-cancer immunological memory generation. VIP-R signaling thus represents a tumor-protective immune-modulatory pathway that is targetable in PDAC.

Abstract 2177: Myeloid-derived arginase depletes microenvironmental arginine in PDAC tumors and leads to activation of arginine de novo biosynthesis in cancer cells

Abstract Arginine is an amino acid critical for various cellular processes, not only protein synthesis but also metabolism of other essential metabolites, like polyamines, as well as a signaling factor for pathways such as the growth regulator mTOR. Previously, our group measured arginine levels in the interstitial fluid of tumors (TIF) of pancreatic ductal adenocarcinoma (PDAC) murine models and found extremely low arginine levels (2-5 uM) in the tumor microenvironment (TME). Despite near complete absence of this critical nutrient in the TME, pancreatic tumors exhibit aggressive growth. We have sought to understand both how the PDAC TME becomes arginine limited and how PDAC cells adapt to proliferate in the absence of arginine. Using genetically engineered mice, we find that arginase activity in the myeloid compartment of PDAC tumors is responsible for arginine depletion in the TME. Staining of Arg1+ myeloid populations in human PDAC samples suggest a similar mechanism reduces arginine availability in human PDAC tumors as well. We then leveraged our newfound knowledge of PDAC TIF composition to develop a novel ex vivo cell culture media formulation with physiologically relevant nutrient levels and monitored arginine acquisition pathways using isotope tracing and metabolomics assays to determine how PDAC cells cope with arginine deprivation. Under TME nutrient conditions, PDAC cells consume available citrulline and use it to produce arginine by de novo synthesis. Starving cells of citrulline or genetically perturbing arginosuccinate synthase (ASS1), key enzyme in arginine biosynthesis, significantly reduces PDAC cellular arginine and proliferative capacity. Immunohistochemical analysis of both human and mouse PDAC tumors indicates that the de novo arginine synthesis pathway is highly expressed in PDAC but not in untransformed pancreas, suggesting a key role for this pathway in PDAC progression. Altogether, we find that myeloid-derived arginase challenges PDAC cells by limiting arginine availability and suggest that de novo arginine synthesis may be a critical metabolic pathway that enables PDAC tumors to cope with this metabolic challenge. Citation Format: Juan Apiz-Saab, Alex Muir. Myeloid-derived arginase depletes microenvironmental arginine in PDAC tumors and leads to activation of arginine de novo biosynthesis in cancer 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 2177.

Abstract A029: Identification of tumor microenvironment components in patient-derived pancreatic ductal adenocarcinoma organoids

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is highly drug resistant with no change in therapeutic approach for the last decade. The PDAC tumor microenvironment (TME) is highly desmoplastic and associated with altered treatment response. Our group previously identified 9 distinct cell types in human PDAC tumors using single-cell RNA-sequencing, demonstrating a diverse TME. However, the TME of in vitro organoid PDAC models remains underexplored. We initiated characterization of the TME from PDAC patient derived organoids (PDOs) to establish a working model for accurate drug sensitivity testing. Methods: We performed immunofluorescence (IF) staining on whole-mount early passage (&amp;lt;P4) PDO lines and corresponding paraffin-embedded primary PDAC specimens to evaluate for activated cancer-associated fibroblasts (CAFs) using antibodies against α-smooth muscle actin (α-SMA) and fibroblast activated protein (FAP); and to evaluate for T-regulatory (Treg) cells with antibodies against interleukin-2 receptor α (IL-2Rα) and forkhead box protein P3 (FOXP3). Results: CAFs promote an immunosuppressive TME in PDAC and have recently been subclassified into inflammatory fibroblasts and myofibroblasts, which can both restrain and promote tumor progression. In this study, we identified three distinct subtypes of CAFs in PDOs, which are consistent with the subtypes found in matched clinical tumor specimens: α-SMA+, which has been reported to be indicative of pancreatic stellate cell activation and associated with increased desmoplasia; FAP+, which influences cancer cell motility, invasion, and cycle progression, extracellular matrix deposition, and angiogenesis within the TME; and α-SMA+/FAP+, which is a myofibroblast subtype. We additionally identified Treg populations in PDOs with peripheral IL-2Rα and central FOXP3 expression in the organoid spheres. Tregs have previously been shown to be overexpressed in the PDAC TME, making this finding clinically relevant. Conclusions: In this preliminary study, we show that PDAC PDOs demonstrate TME components that mirror primary tumor specimens, including CAFs and Tregs. The demonstration of a tumor-matched, immunocompetent TME in PDAC PDOs provides a more clinically relevant in vitro tumor model for patient-matched drug sensitivity testing. Citation Format: Mei Gao, Charles J. Bailey, Megan M. Harper, Michael J. Cavnar, Prakash Pandalai, Shadi A. Qasem, Joseph Kim. Identification of tumor microenvironment components in patient-derived pancreatic ductal adenocarcinoma organoids [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr A029.

Gα13 loss in Kras/Tp53 mouse model of pancreatic tumorigenesis promotes tumors susceptible to rapamycin.

SUMMARYGα13 transduces signals from G-protein-coupled receptors. While Gα13 functions as a tumor suppressor in lymphomas, it is not known whether Gα13 is pro-tumorigenic or tumor suppressive in genetically engineered mouse (GEM) models of epithelial cancers. Here, we show that loss of Gα13 in the Kras/Tp53 (KPC) GEM model promotes well-differentiated tumors and reduces survival. Mechanistically, tumors developing in KPC mice with Gα13 loss exhibit increased E-cadherin expression and mTOR signaling. Importantly, human pancreatic ductal adenocarcinoma (PDAC) tumors with low Gα13 expression also exhibit increased E-cadherin expression and mTOR signaling. Treatment with the mTOR inhibitor rapamycin decreases the growth of syngeneic KPC tumors with Gα13 loss by promoting cell death. This work establishes a tumor-suppressive role of Gα13 in pancreatic tumorigenesis in the KPC GEM model and suggests targeting mTOR in human PDAC tumors with Gα13 loss.

Modulation of the Human Pancreatic Ductal Adenocarcinoma Immune Microenvironment by Stereotactic Body Radiotherapy.

Stereotactic body radiotherapy (SBRT) is an emerging treatment modality for pancreatic ductal adenocarcinoma (PDAC), which can effectively prime cytotoxic T cells by inducing immunogenic tumor cell death in preclinical models. SBRT effects on human PDAC have yet to be thoroughly investigated; therefore, this study aimed to characterize immunomodulation in the human PDAC tumor microenvironment following therapy. Tumor samples were obtained from patients with resectable PDAC. Radiotherapy was delivered a median of 7 days prior to surgical resection, and sections were analyzed by multiplex IHC (mIHC), RNA sequencing, and T-cell receptor sequencing (TCR-seq). Analysis of SBRT-treated tumor tissue indicated reduced tumor cell density and increased immunogenic cell death relative to untreated controls. Radiotherapy promoted collagen deposition; however, vasculature was unaffected and spatial analyses lacked evidence of T-cell sequestration. Conversely, SBRT resulted in fewer tertiary lymphoid structures and failed to lessen or reprogram abundant immune suppressor populations. Higher percentages of PD-1+ T cells were observed following SBRT, and a subset of tumors displayed more clonal T-cell repertoires. These findings suggest that SBRT augmentation of antitumor immunogenicity may be dampened by an overabundance of refractory immunosuppressive populations, and support the continued development of SBRT/immunotherapy combination for human PDAC.

Metabolic reprogramming by driver mutation-tumor microenvironment interplay in pancreatic cancer: new therapeutic targets.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers globally with a mortality rate exceeding 95% and very limited therapeutic options. A hallmark of PDAC is its acidic tumor microenvironment, further characterized by excessive fibrosis and depletion of oxygen and nutrients due to poor vascularity. The combination of PDAC driver mutations and adaptation to this hostile environment drives extensive metabolic reprogramming of the cancer cells toward non-canonical metabolic pathways and increases reliance on scavenging mechanisms such as autophagy and macropinocytosis. In addition, the cancer cells benefit from metabolic crosstalk with nonmalignant cells within the tumor microenvironment, including pancreaticstellate cells, fibroblasts, and endothelial and immune cells. Increasing evidence shows that this metabolic rewiring is closely related to chemo- and radioresistance and immunosuppression, causing extensive treatment failure. Indeed, stratification of human PDAC tumors into subtypes based on their metabolic profiles was shown to predict disease outcome. Accordingly, an increasing number of clinical trials target pro-tumorigenic metabolic pathways, either as stand-alone treatment or in conjunction with chemotherapy. In this review, we highlight key findings and potential future directions of pancreatic cancer metabolism research, specifically focusing on novel therapeutic opportunities.