Pancreatic Ductal Adenocarcinoma Model Research Articles

Abstract 6818: Obesity-mediated perineural invasion promotes PDAC tumorigenesis

Abstract Obesity is a modifiable host factor that has been reported to increase the risk of pancreatic ductal adenocarcinoma (PDAC) by ~60% and the mortality by two-fold, however, the exact mechanisms by which obesity enhances PDAC aggressiveness is incompletely understood. Given that nearly 74% of U.S. adults are overweight or obese (US Center for Disease Control), resolving the complex association between obesity and PDAC may unveil new targets for prevention and/or intervention to decrease incidence and improve outcomes. The prevailing notion is that obesity-induced tumor in situ factors (i.e., oxidative, hypoxic, nutrient, and biochemical) play crucial roles in enhancing cancer cell fitness and survival. However, these concepts have yet to lead to the identification of any actionable target in patients, with obesity-related cancer in general and PDAC in particular. Prior studies and our preliminary data show the presence of a distinctive tumor immune profile in PDAC models under conditions of obesity, which encompasses immune suppressive myeloid and type 2 immune cells, namely M2-like tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs), that inhibit effector CD8+ T cell expansion and function enabling PDAC progression. However, the genesis of this ‘type 2 immune cell’ dominant tumor-immune microenvironment (TIME) of obesity-driven PDAC remains to be fully understood. This led us to take a holistic approach utilizing multiple genetically engineered mouse models (GEMMs), pharmacological inhibitors, transcriptomic analysis (RNA-seq, spatial transcriptomic, and scRNA-seq), fresh PDAC patient samples, and imaging technologies (confocal microscopy) to understand the molecular mechanisms. Our novel mechanistic study using some of the above-mentioned tools shows that obesity-driven PDAC has significantly higher perineural invasion (PNI) that enhances PDAC progression. We found that sympathetic nerve terminals (of the PNI) via neurotransmitter release control the expression of integral cytokines that cause a dramatic remodeling of the TIME. Specifically, the PNI-mediated neuro-adrenergic signaling activates β2-adrenergic receptor (β2-AR) on PDAC cells, leading to increased tumor cell production/proliferation and secretion of the ‘alarmins’ IL-33 and IL-1β. Importantly, we showed that mitigation of adrenergic signaling using two separate approaches: (i) pharmacological antagonists of β2-ARs (β-blockers), and (ii) the use of a thermoneutral model leads to substantial abrogation of obesity-mediated tumor progression. These, and other key data raise the provocative question that reducing adrenergic signaling-dependent IL-33 expression and release favor a pro-inflammatory TIME and significantly increase patient survival in obesity-driven PDAC. Citation Format: Shyamananda Singh Mayengbam, Aftab Alam, Sharon Senchanthisai, Irmak Bektas, Prasenjit Dey. Obesity-mediated perineural invasion promotes PDAC tumorigenesis [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 6818.

Abstract 5373: Decoding the role of intrinsic pancreatic cellular signaling in shaping the immunosuppressive tumor microenvironment

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) has the highest mortality rate among major cancers, with over 50% of patients having liver metastases at diagnosis. Conventional T-cell-based immunotherapies are ineffective against PDAC liver metastases due to the intricate hepatic tumor microenvironment (TME) that hinders effective immune responses. Thus, it is vital to promote the influx of cytotoxic lymphocytes and prime antitumor immunity. PDAC cells exhibit plasticity and intrinsic cellular heterogeneity, leading to varying immune cell infiltrates and immune responses. Concurrently, early metastases to the liver create an immunosuppressive environment. Our study employs multiple PDAC models, originating from a congenic array of distinct PDAC cell clone tumors with varying degrees of T cell infiltration to delineate the signaling pathways that lead to immunosuppression in the pancreas and liver. Methods: The compendium of congenic PDAC murine cell clones mirrors immune heterogeneity observed in tumors, spanning from low to high T cell infiltration. To overcome a scarcity of tumor-specific neoepitopes in PDAC, we engineered PDAC cell clones expressing chicken ovalbumin (OVA) for antigen-specific T and B cell responses. By subcutaneous and intraportal vein injection of PDAC cell clones into mice, we induce primary pancreatic and metastatic liver tumors to explore immune phenotypes and assess anti-tumor adaptive immune responses, including myeloid and lymphoid cell subsets. Results: In vivo engraftment of PDAC clones showed varied CD4+/CD8+ T cells and polymorphonuclear myeloid-derived suppressor cells, accentuated with immunogenic OVA antigen expression. While all OVA+ PDAC lines elicited antigen-specific immune responses, only ‘TIL high’ tumors were eradicated, while ‘TIL low’ clones persisted in vivo. Additionally, ‘TIL low’ clones formed liver metastases upon intraportal injection, despite OVA expression. RNAseq unveiled differential expression in IL-1 family cytokines and receptors, chemokine-like factor gene superfamily, parathyroid hormone relevant function and metabolism. Current investigations include altering these pathways to re-program the tumor microenvironment and induce local immune suppression. Conclusion: Using diverse PDAC models, we created tumors with immune heterogeneity and altered transcriptional profiles. We identified validated differentially expressed immune altering cytokines, such as CXCL1 and CSF3, and potential novel IL-1 family genes and parathyroid signaling genes. The altered TME conferred protection against tumor antigen-specific immunity in certain clones, both in subcutaneous and liver metastasis models. Ongoing studies will assess the impact of these genes in the distinct environments, offering avenues for immunotherapeutic strategies targeting pancreatic cancer liver metastasis. Citation Format: Bushangqing Liu, Ethan Agritelley, Daniel Nussbaum, Junping Wei, Gangjun Lei, Melissa Gajda, Zachary Hartman. Decoding the role of intrinsic pancreatic cellular signaling in shaping the immunosuppressive tumor microenvironment [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 5373.

Abstract 4267: Inflammation mediated expression of integrin αvβ3 potentiates KRAS driven PDAC oncogenesis

Abstract Understanding how pancreatic epithelial cells respond to inflammation and why some become tumorigenic and aggressive could identify new methods of early detection and novel therapeutic targets to control disease progression. Here, we leveraged an in vivo model in which mice with pancreas-specific expression of mutant Kras progress from pre-malignant intraepithelial neoplasias (PanINs) to pancreatic ductal adenocarcinoma (PDAC) following caerulein-induced chronic pancreatitis. During the transition from PanINs to PDAC, we observe two classes of neoplastic lesions: classically-described PanIN tubular structures that are highly organized and previously uncharacterized atypical highly disorganized lesions that are marked by robust integrin αvβ3 expression, observations which are consistent with human pancreatitis and PDAC. In vitro, we report that immune-, stroma-, and tumor cell-derived inflammatory cytokines induce β3 expression in a STAT3-dependent manner leading to increased integrin αvβ3. Considering that we previously established αvβ3 as a driver of cancer cell stress tolerance, drug resistance, and a stem-like phenotype, the acquisition of αvβ3 during chronic inflammation may promote tumorigenesis. Indeed, using the spontaneous tumor mouse model and xenograft models of human PDAC, we find that cells with an inability to upregulate β3 during tumor initiation fail to form tumors. These findings implicate integrin αvβ3 as a critical driver of inflammation-mediated pancreatic tumorigenesis. Citation Format: Ryan M. Shepard, Alejandro D. Campos, Zachary M. Ortega, Hiromi I. Wettersten, Tami Von Schalscha, Sara M. Weis, David A. Cheresh. Inflammation mediated expression of integrin αvβ3 potentiates KRAS driven PDAC oncogenesis [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 4267.

Abstract 5737: Enhancing cancer treatment Via a nanostructured chemoimmunotherapy gel facilitating interleukin-2 delivery and immunogenic cell death induction

Abstract Background: The landscape of immunotherapy, employing recombinant cytokines like interleukin-2 (IL-2), confronts challenges marked by its short half-life, systemic toxicity, and constrained tumor accumulation. These hurdles are particularly evident in the context of the immunosuppressive milieu characterizing pancreatic ductal adenocarcinoma (PDAC). Chemo-immuno-therapeutic synergies, notably those provoking immunogenic cell death (ICD), have demonstrated superior efficacy. This investigation delves into Pt-NHC as a type II ICD inducer to surmount immunosuppression and amplify antitumor immunity within a highly tumor-accumulated liposomal drug delivery system. Additionally, the co-administration of the angiotensin receptor blocker, losartan, mitigates desmoplasia in PDAC, further augmenting the efficacy of immunotherapy. Methods: To address the constraints of IL-2, a lipid-coated nanogel, IL2-Pt@Nanogel, was innovated, amalgamating silk fibroin-loaded IL-2 with Pt-NHC. The nanogel aimed to enhance IL-2 pharmacokinetics and optimize tumor targeting. Concurrently, losartan was employed to alleviate desmoplasia within the tumor microenvironment. Result: The chemoimmunotherapy nanogel, when coupled with losartan, showcased therapeutic potential in murine models of desmoplastic PDAC. Pt-NHC induced ER-localized reactive oxygen species (ROS) and DAMP release, reshaping the immunosuppressive microenvironment by repolarizing M2-type macrophages to M1 and diminishing the regulatory T-cell population. Co-delivery of IL-2 and Pt-NHC in the nanogel enhanced T-cell infiltration and activation, curbing tumor progression in primary and liver metastasized PDAC models. Importantly, the addition of losartan reduced collagen accumulation within tumors, resulting in heightened infiltration of effector T cells and more pronounced suppression of tumor growth in PDAC and metastasized liver. Conclusion: This study introduces an innovative nanogel delivery system (IL2-Pt@Nanogel) for chemoimmunotherapy, effectively addressing the challenges associated with IL-2 therapy. Leveraging the enhanced permeability and retention (EPR) effect, the nanogel improves IL-2 stability and tumor delivery. Pt-NHC incorporation induces ICD, reshaping the tumor microenvironment, and in synergy with losartan, elicits robust anticancer immunity. This strategy holds promise for clinical translation as a secure and efficient treatment for immunosuppressive and desmoplastic cancers, such as PDAC, presenting a distinctive therapeutic avenue. Citation Format: Hsuan Yu Mu, Yen-Nhi Ngoc Ta, Jing Rui Max Tham, Fu-Fei Hsu, Yu-Chieh Lin, Hsi-Chien Huang, Yun-Chieh Sung, Chih-I Huang, Ching-Ling Wu, Chao-Hung Chang, Sheng Yang, Tsung-Ying Lee, Jane Wang, Dan G. Duda, Yves Boucher, Jen-Huang Huang, Wee Han Ang, Yunching Chen. Enhancing cancer treatment Via a nanostructured chemoimmunotherapy gel facilitating interleukin-2 delivery and immunogenic cell death induction [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 5737.

Abstract 1262: Comparative analysis of TP53 alleles in pancreatic ductal adenocarcinoma

Abstract The transcription factor p53 is a tumor suppressor capable of inducing cell cycle arrest, senescence, and apoptosis. Both truncating loss-of-function mutations and point mutations of the TP53 gene (mouse gene Trp53), which encodes for the p53 protein, are frequently observed across human cancers. While point mutations in p53 result in loss of canonical tumor suppressor function, recent studies suggest that these mutated proteins acquire pro-tumorigenic gain-of-function properties. For example, Trp53R172H mutations (the murine homolog of TP53R175H, the most common human TP53 variant) enhance metastatic spread relative to deletion mutations in mouse models of advanced pancreatic ductal adenocarcinoma (PDAC). To further explore the differential functions of p53 point and deletion mutants in cancer progression, we performed a rigorous comparative analysis of Trp53 alleles in vivo using Mosaic Analysis with Double Markers (MADM) in mice. MADM uses stochastic mitotic recombination to induce two genotypically distinct daughter cells - created at 1-to-1 ratios - expressing different Trp53 variants dependent on the genotype of the mouse (+/+ vs. -/-, R172H/R172H vs. +/+, R172H/R172H vs. -/-) and simultaneously label them with unique genetically encoded fluorescent markers (TdTomato vs. GFP). We integrated MADM into a faithful Kras-driven model of pancreatic tumorigenesis and used fluorescence microscopy to trace subclonal populations with various p53 alleles within the same mouse. By analyzing the ratio of TdTomato+ to GFP+ cells, we studied the functional differences between alleles in driving pancreatic cancer at various stages of progression. We found that Trp53−/− cells exhibited greater tumor initiation of preinvasive pancreatic intraepithelial neoplasia (PanINs) and early PanIN cell expansion compared to Trp53+/+ cells. Surprisingly, Trp53R172H/R172H cells were comparable in number to Trp53+/+ cells in early PanINs but were outcompeted by Trp53−/− cells.In contrast, both Trp53R172H/R172H and Trp53−/− cells were capable of facilitating the transition to advanced PDAC with comparable survival times. These phenotypic differences imply that p53R172H retains tumor suppressive properties in early pancreatic tumorigenesis, but similar to the loss of p53, it is incapable of constraining progression to advanced disease, arguing that p53R172H is a separation of function mutation in vivo. Ongoing studies examining the molecular differences between Trp53 alleles by fluorescence-activated cell sorting and RNA-sequencing will shed further light onto the underlying mechanisms that explain these phenotypic differences. Citation Format: Andy Tang, Sherry Agabiti, Hannah Chung, Mandar Deepak Muzumdar. Comparative analysis of TP53 alleles in pancreatic ductal 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 1262.

Abstract 7125: Inhibition of IDH1 impairs homologous recombination and induces sensitivity to PARP inhibitor in pancreatic cancer

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer-related deaths in the United States. While Poly (ADP-ribose) polymerase (PARP) inhibitors hold promise in treating PDAC with Homologous Recombination Deficiency (HRD). However, HRD occurs in only 10% of cases, leaving 90% with intact Homologous Recombination Proficiency (HRP). Our research highlights the key role of wild-type isocitrate dehydrogenase 1 (IDH1) in maintaining cellular function. We found that inhibiting IDH1 increases DNA damage, suppressing the DNA repair pathway crucial for genomic integrity. This makes cancer cells susceptible to PARP inhibitors, offering a new PDAC treatment approach. Methods: The effect of IDH1 inhibition (Ivosidenib) combined with PARP inhibition (Olaparib) on in vitro growth inhibition were assessed through Trypan blue and PicoGreen in drug combination assays. Additionally, we investigated the molecular mechanism underlying the synergistic effects of drug combination. To further evaluate the therapeutic potential of IDH1 inhibition in combination with PARP inhibitors, we examined tumor growth in xenograft models of PDAC in athymic nude mice. Results: Our data report that, mechanistically, IDH1 inhibition decreased expression of HR DNA repair pathway molecules, such as BRCA1 and BRCA2, and leading to decreased HR repair efficiency in pancreatic cancer cells. Short-term cell viability data demonstrated that targeting IDH1 with ivosidenib when combined with DNA-damaging agent (Olaparib) had a synergistic effect in HRP cell lines (MiaPaCa-2 and Panc-1) with a positive synergy score and Bliss score greater than 1. Additionally, we assessed long-term cell survival using colony formation assays, which yielded a dramatic reduction in cell survival for both Panc1 and MiaPaCa-2 cells when olaparib was combined with ivosidenib, as compared to single-agent controls. Consequently, this reduction increased the levels of apoptosis induced by olaparib. Furthermore, we discovered that these two compounds complemented each other in DNA damage response, leading to an increase in the DNA damage biomarker γ-H2AX. In vivo studies using xenograft models demonstrated that the combination of ivosidenib and olaparib synergistically enhanced anti-tumor activity as compared to either single-agent used alone. Conclusion: Our data provides insights into the mechanisms underlying the susceptibility of PDAC tumor growth to a dual treatment approach involving an IDH1 inhibitor and a PARP inhibitor, particularly in the context of HRP cancer. This highlights the promise of precision medicine for pancreatic cancer treatment, though further pre-clinical studies are needed for validation and refinement. Citation Format: Mehrdad Zarei, Omid Hajihassani, Hallie J. Graor, Alexander W. Loftus, Soubhi Tahhan, Faith Nakazzi, Parnian Naji, Luke D. Rothermel, Jonothan R. Brody, Jordan M. Winter. Inhibition of IDH1 impairs homologous recombination and induces sensitivity to PARP inhibitor in pancreatic cancer [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 7125.

Abstract 5306: PTPN22 targeting partners with 41BB/OX40 costimulation to overcome anti-PD1 resistance in pancreatic ductal adenocarcinoma

Abstract Background: The pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME) is notable for a scarcity of cytotoxic T cells and an overabundance of immunosuppressive myeloid and regulatory T cells. Checkpoint immunotherapies targeting PD/L1 or CTLA4 have shown efficacy in immunogenic cancers but remain ineffective in PDAC, highlighting a need for novel approaches. Abrogating protein tyrosine phosphatase non-receptor type 22 (PTPN22), a phosphatase in the TCR signaling cascade, has been shown to modulate multiple mechanisms of immune resistance. Furthermore, 41BB costimulatory pathway has recently been investigated as a potential strategy to enhance immunotherapy against PDAC. Using immune-resistant murine models of PDAC, we investigated PTPN22 as an immunotherapeutic target in combination with 41BB co-stimulation and PD1 inhibition against PDAC. Methods: We employed a well-characterized murine PDAC cell line expressing mutant KrasG12D and Trp53R172H under the Pdx1-cre promoter (KPCY 6419c5). This tumor line is resistant to combination immuno- and chemotherapies. To determine treatment efficacy, PTPN22 deficient mice (KO) were inoculated with KPCY6419c5 cells either subcutaneously or orthotopically into the pancreas. To extend the translatability of PTPN22 targeting, we also injected PTPN22 competent mice with the same tumor cells and treated them with our novel PTPN22 inhibitor L1. Harvested tumors were processed for FFPE and mass cytometry (CyTOF) analysis to track changes in the immune compartment. Results: When PTPN22 was abrogated, treatment with anti-PD1 and 41BB agonism led to a 10-day delay in substantial tumor formation and roughly 75% reduction in tumor volume by 21-days post treatment. These tumors showed elevated levels of OX40 and OX40L primarily in the setting of PTPN22 KO/PD1/41BB therapy. In a subsequent in vivo experiment using an OX40L neutralizing antibody, we found that OX40 signaling is essential for the efficacy of PTPN22 KO/PD1/41BB therapy. Furthermore, combining OX40 agonist with anti-PD1 in PTPN22 KO sufficiently mimicked the efficacy seen with the anti-PD-1 and 41BB combination. CyTOF analysis indicated that OX40 expression is enriched in Tregs and OX40L is enriched in myeloid derived suppressor cells (MDSCs). Moreover, combination therapy efficacy was reproduced using the PTPN22 inhibitor L1. Conclusions: PTPN22 abrogation enhances the success of PD-1 inhibition given with either OX-40 or 41BB agonist therapies. In addition, PTPN22 abrogation together with PD1 inhibition and 41BB costimulation reduces MDSC and Treg suppression of effector T cells via the OX40L-OX40 axis. Finally, PTPN22 can be blocked by a small molecule inhibitor strengthening its candidacy as a therapeutic target. Citation Format: Soren Charmsaz, Nicole E. Gross, Jae W. Lee, Jianping Lin, Alexei G. Hernandez, Erin M. Coyne, Sarah M. Shin, Courtney Cannon, Xuan Yuan, Zhong-Yin Zhang, Elizabeth M. Jaffee, Won Jin Ho. PTPN22 targeting partners with 41BB/OX40 costimulation to overcome anti-PD1 resistance in pancreatic ductal 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 5306.

Abstract 1392: Neutrophil extracellular trap (NET)-induced pancreatic tumor metastasis requires integrin-linked kinase (ILK) signaling

Abstract Neutrophil extracellular traps (NETs) are an important contributor to the immunosuppressive tumor microenvironment and facilitate metastasis of solid cancers. NETs have been shown to stimulate breast and colon cancer cell metastasis through a mechanism potentially involving an interaction between integrin-linked kinase (ILK) and the cell surface receptor coiled-coil domain containing protein 25 (CCDC25). Here, we have interrogated whether ILK is required for NET-induced metastasis in pancreatic ductal adenocarcinoma (PDAC), an inflammation-driven tumor that is difficult to treat. Evaluation of the circulating neutrophil to lymphocyte ratio (NLR) in the blood samples of patients presenting with metastatic PDAC showed that a higher baseline NLR is associated with significantly shorter overall patient survival. Western blot and immunofluorescence analyses demonstrated that human PDAC cell lines, patient-derived xenograft cells, cells derived from the KPCY genetic model of PDAC and patient-derived organoids co-express CCDC25 and ILK. Co-immunoprecipitation analyses showed that CCDC25 and ILK associate in both mouse and human PDAC cells, and that exposure of the cells to NETs results in an increased amount of ILK associated with CCDC25. Exposure of human and KPCY mouse PDAC cells to NETs increases phosphorylation of GSK3-β and ERK, increases activation of Rac1 and Cdc42 and upregulates markers of epithelial-to-mesenchymal transition (EMT), including ZEB1 and Snail, in a time and concentration-dependent manner. Furthermore, time-lapse imaging using Incucyte-based wounding assays showed that exposure to NETs induces pseudopodia-like protrusions, migration and invasion by these cells. RNAi-mediated suppression of ILK expression or inhibition of ILK activity using a highly selective inhibitor of ILK, QLT-0267, significantly inhibits the NET-induced increase in GSK3-β phosphorylation, Rac1/Cdc42 activation, migration and invasion of PDAC cells. In vivo, co-localization of CCDC25 and ILK is observed in tumors and metastases from KPCY mouse and MIA PaCa-2 human PDAC xenograft models stained by multispectral immunofluorescence and analyzed by confocal microscopy. Tumors and metastases show the presence of infiltrating neutrophils and NETs as indicated by staining for myeloperoxidase and citrullinated histone H3. Importantly, doxycycline-inducible shRNA-mediated suppression of ILK expression by luciferase-positive PDAC cells following injection of these cells through the tail vein of mice administered LPS intranasally results in a significant reduction in metastasis as measured by bioluminescence-based imaging, compared to control animals. Collectively, these data identify NET-induced ILK signaling as an important contributor to PDAC progression and suggest the potential for targeting this axis to prevent PDAC progression and metastasis. Citation Format: Paul C. McDonald, Shannon J. Awrey, Hossein Tavakoli, Rebekah Carroll, Zachary J. Gerbec, Joanna M. Karasinska, David F. Schaeffer, Daniel J. Renouf, Shoukat Dedhar. Neutrophil extracellular trap (NET)-induced pancreatic tumor metastasis requires integrin-linked kinase (ILK) signaling [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 1392.

Abstract 6597: CD40 agonism induces CD4 T cell mediated rejection of major histocompatibility complex class I deficient pancreatic tumors

Abstract Cytotoxic CD8 T cells are the canonical mediators of tumor clearance by the adaptive immune system. As such, current immunotherapies, including immune checkpoint blockade (ICB), target exhausted CD8 T cells with the hope of reinvigorating the CD8 T cells to drive tumor clearance. However, many tumors, including pancreatic ductal adenocarcinoma (PDAC), can evade CD8 T cell detection via downregulation of the antigen presentation molecule, major histocompatibility complex I (MHC I) as either primary or acquired resistance to immunotherapy. We have previously reported that agonistic CD40 antibody (αCD40), which promotes the maturation and licensing of dendritic cells to drive T cell priming, synergizes with ICB to induce tumor rejection dependent on both CD4 and CD8 T cells in mouse models of PDAC. Given the potential mechanisms of resistance to CD8 T cell immunity, we hypothesized that interrogation of the mechanisms underlying αCD40-induced CD4 T cell rejection of PDAC will reveal targets for improving CD4 T cell-directed immunotherapies. Here, we show that implantation of an MHC I deficient PDAC cell line derived from the genetically engineered KrasG12DTrp53R172HPdx1-Cre (KPC) mouse model results in normal tumor establishment and progression. Upon treatment with combined αCD40 and ICB, tumor growth was significantly decreased in a CD4, but not CD8, T cell-dependent manner. Using genetic knockout mice, we determined that tumor regression was perforin-independent and identified host expression of IFNγ as requisite for therapeutic efficacy. To identify the cellular subset mediating CD4 T cell-rejection of the tumor, we assessed the major histocompatibility complex II (MHC II) positive cells in the tumor microenvironment (TME), which possess the ability to directly synapse with CD4 T cells to drive anti-tumorigenic T cell programs. We determined that macrophage and myeloid cells were dispensable for treatment efficacy, however non-immune cells in the TME can also interact with CD4 T cells through expression of MHC II. Interrogation of stromal cells reveals an increase in the proportion of MHC II+ subsets after combined αCD40/ICB treatment, with a concomitant decrease in the proportion of MHC II+ tumor cells. These data support the notion that CD4 T cell control of tumors may be mediated by both direct and indirect mechanisms of tumor killing. Findings from this work will elucidate non-canonical mechanisms of CD4 T cell-mediated rejection of tumors and may be leveraged to discover novel translational targets for immunotherapy. Citation Format: Margaret E. Haerr, Samuel I. Kim, Charu Arora, Kyle P. Gribbin, Robert H. Vonderheide, Katelyn T. Byrne. CD40 agonism induces CD4 T cell mediated rejection of major histocompatibility complex class I deficient pancreatic tumors [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 6597.

Abstract 1578: RAS-GTP inhibition modulates Hedgehog signaling, suppressing myCAFs and promoting iCAFs in pancreatic ductal adenocarcinoma

Abstract More than 90% of human pancreatic ductal adenocarcinoma (PDAC) cases are driven by activating mutations in KRAS. RMC-7977 is a potent inhibitor of GTP-bound RAS proteins (RAS(ON), including both wild type and mutant variants of KRAS, NRAS, and HRAS. The related investigational agent, RMC-6236, is a first-in-class, potent, orally bioavailable, RASMULTI(ON) inhibitor currently in Phase 1/1b clinical trials (NCT05379985). We performed preclinical studies in a range of models of PDAC, including the highly chemoresistant K-rasLSL.G12D/+, p53LSL.R172H/+, Pdx1Cretg/+ (KPC) genetically engineered mouse. RMC-7977 exhibited broad anti-tumor activity at tolerable doses, provoking radiographic responses in KPC pancreatic tumors and extending overall survival by 3-fold, the largest response observed yet in this model. RMC-7977 dosing produced a metronomic effect on RAS signaling in tumor and normal tissues. This yielded tumor-selective effects on apoptosis and proliferation, consistent with RAS oncogene addition in PDAC. PDAC tumors are characterized by an expansive stroma that harbors multiple subtypes of cancer associated fibroblasts (CAFs) that manufacture a fibrotic, inflammatory extracellular matrix. CAF proliferation is driven by signals emanating from the malignant epithelial cells, such as Sonic Hedgehog (SHH), a secreted ligand that drives downstream Hedgehog pathway signaling in myofibroblastic CAFs (myCAFs). To understand the impact of RAS-GTP inhibition on paracrine signaling to CAFs in PDAC, To understand the dynamic responses of malignant epithelial cells following GTP-RAS inhibition, we performed single cell RNA sequencing (scRNAseq) on KPC pancreatic tumors treated with RMC-7977 or vehicle at multiple timepoints. Using the ARACNe and VIPER algorithms, we performed single cell regulatory network analysis on the expression profiles of >210,000 cells to calculate the activities of thousands of transcriptional regulatory protein in each cell. We found that the RAS-GTP inhibition blocked SHH expression in malignant epithelial cells, resulting in loss of downstream Hh pathway activity in CAFs within 24 hours of treatment. By one week of treatment, myCAFs were significantly depleted whereas inflammatory CAFs (iCAFs) were significantly accumulated. Strikingly, CAF heterogeneity was restored in KPC pancreatic tumors that acquired resistance to RMC-7977, despite continued suppression of Hedgehog pathway signaling. Consistent with prior studies of Smoothened inhibitors, the depletion of myCAFs from RAS-GTP inhibition was associated with the rapid opening and hypersprouting of intra-tumoral blood vessels. Ongoing studies using the mutant-selective KRASG12D inhibitor RM-044 should discriminate between direct effects of wild type RAS inhibition in CAFs versus the paracrine consequences of mutant RAS inhibition in malignant epithelial cells. Citation Format: Marie Hasselluhn, Lorenzo Tomassoni, Urszula Wasko, Alvaro Curiel-Garcia, Tanner Dalton, Steve A. Sastra, Carmine Palermo, Andrea Califano, Kenneth P. Olive. RAS-GTP inhibition modulates Hedgehog signaling, suppressing myCAFs and promoting iCAFs in pancreatic ductal 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 1578.

Abstract 3155: Metabolic stress induces an intrinsic inflammatory CAF phenotype that regulates stromal architecture in pancreatic cancer

Abstract Macropinocytosis is a critical amino acid supply pathway that fuels the metabolism of tumor cells and cancer-associated fibroblasts (CAFs) in pancreatic ductal adenocarcinoma (PDAC). PDAC tumors are deficient in glutamine, a critical amino acid that tumor cells and CAFs use to sustain their cellular fitness. We have previously shown that both PDAC cells and CAFs stimulate macropinocytosis as an adaptive response to glutamine depletion. How these linked metabolic mechanisms might co-operate to control stromal architecture remains elusive. In this study, we employed glutamine starvation and 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), a selective inhibitor of macropinocytosis, to investigate how metabolic stress impacts the tumor microenvironment. We find that concomitant suppression of glutamine metabolism and macropinocytosis synergizes to drive an intrinsic inflammatory CAF phenotype that requires metabolic stress-induced ERK/MAPK signaling. Utilizing immunocompetent syngeneic mouse models of PDAC, we find that blocking macropinocytosis in these glutamine-depleted tumors diminishes tumor growth and reorganizes the tumor stroma by decreasing collagen deposition, increasing vasculature expansion and enhancing the infiltration of both CD8+ and CD4+ T cells. Alterations in the stromal landscape under these conditions are linked to the enhancement of CAFs that display an inflammatory signature while simultaneously suppressing more myofibroblastic identities within the tumor. Interestingly, we find that these effects on the tumor microenvironment can be harnessed to improve therapeutic responses. We determine that combining macropinocytosis inhibition with immune checkpoint blockade reduces PDAC tumor burden and significantly inhibits metastasis. We also find that macropinocytosis inhibition enhances drug delivery, thereby improving the efficacy of gemcitabine chemotherapy. Our findings demonstrate that intratumoral metabolic stress plays a critical part in preserving and modulating the tumor stroma. Citation Format: Yijuan Zhang, Swetha Maganti, Jennifer Hope, Li Lin, Cheska Marie Galapate, Florent Carrette, Linda Bradley, Cosimo Commisso. Metabolic stress induces an intrinsic inflammatory CAF phenotype that regulates stromal architecture in pancreatic cancer [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 3155.

Abstract 2896: Elucidating the role of transglutaminase 2 (TGM2) in pancreatic ductal adenocarcinoma pathogenesis and its therapeutic implications

Abstract Pancreatic cancer remains one of the deadliest malignancies, with limited therapeutic options and a poor prognosis due to delayed symptom presentation and disease detection. Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of less than 8%, predominantly attributed to oncogenic KRAS mutations and loss-of-function mutations in TP53, SMAD4, and P16. Our lab is interested in studying Transglutaminase 2 (TGM2), a multifunctional enzyme involved in protein cross-linking and cellular signaling, because it is highly correlated with cancer cell survival, malignancy, metastasis, and treatment resistance. Clinically, overexpression of TGM2 is associated with poorer survival in patients with Pancreatic Ductal Adenocarcinoma so it is imperative to understand the mechanism of its action in disease progression. To elucidate the role of TGM2 in PDAC, we studied the targeted deletion of TGM2 in the context of a mouse model of PDAC and saw a significant reduction in PDAC incidence and precursor lesion formation, suggesting that TGM2 has a role in the tumor microenvironment. Using single cell sequencing, we found TGM2 levels to be elevated in certain cell populations, specifically endothelial cells and cancer cells. We discovered high TGM2 levels in TIE2-GFP mouse vessels and subsequently found high TGM2 levels in patient tumor vasculature. Further studies aim to conditionally ablate TGM2 in endothelial cells to assess its mechanistic involvement in PDAC initiation and progression. Additionally, we are studying concurrent conditional TGM2 and SMAD4 deletions in mice to investigate pancreatic cancer precursor lesion formation and are further evaluating the protective mechanisms of a TGM2 deletion in a more aggressive mouse model of PDAC. Our preliminary findings substantiate TGM2 as a critical player in PDAC pathogenesis, opening avenues for targeted therapeutics to ultimately improve patient prognosis. Citation Format: Polina Wright, Azeddine Atfi. Elucidating the role of transglutaminase 2 (TGM2) in pancreatic ductal adenocarcinoma pathogenesis and its therapeutic implications [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 2896.

Abstract 3300: Dual inhibition of PIKfyve and KRAS/MAPK as a potential for therapeutic strategy for pancreatic ductal adenocarcinoma

Abstract Background: PIKfyve is a lipid kinase that serves as the single source for PI(3,5)P2, a critical molecule for lysosome functions, including autophagy. Pancreatic Ductal Adenocarcinoma (PDAC) is known to utilize autophagy as well as other lysosome functions to survive in its harsh microenvironment. Considering the role of PIKfyve in autophagy, we hypothesized that PIKfyve is important for PDAC pathophysiology. Indeed, we screened multiple cell lines of different cancer lineages and found that PDAC cell lines were highly sensitive to PIKfyve inhibitors apilimod and ESK981. Given these results, we aimed to establish PIKfyve inhibition as a therapeutic strategy for PDAC. Importantly, this idea is rapidly translatable as both apilimod and ESK981 have both cleared phase-1 clinical trials. Additionally, PDAC nearly ubiquitously harbors a mutation in KRAS, leading to the overactivation of the KRAS-RAF-MEK-ERK pathway, which is known to be the driver of PDAC. Recent reports showed that inhibition of this pathway results in induction of autophagic flux as a protective mechanism in PDAC. Thus, we aimed to investigate the therapeutic potential of PIKfyve inhibition in blocking protective autophagy induced by KRAS/MAPK inhibition. Methods and results: In order to determine the potential of PIKfyve inhibition as a therapeutic for PDAC treatment, we first established that PIKfyve inhibition disrupts the autophagic flux in cells. Specifically, we used PIKfyve inhibitors ESK981 and apilimod as well as CRISPRi-mediated knockdown and saw a decrease in autophagic flux through western blot and GFP-LC3-RFP-LC3∆G-based autophagic flux probe analyses. Finally, PIKfyve inhibition decreased cell viability with IC50s in the nanomolar range.To evaluate the potential of combined inhibition of KRAS/MAPK and PIKfyve, we first confirmed that genetic or pharmacological KRAS/MAPK perturbation indeed increases autophagic flux utilizing the autophagic flux probe. Importantly, we found that PIKfyve inhibition attenuates the autophagic flux induced by KRAS/MAPK inhibition. Moreover, we determined that dual inhibition of PIKfyve and KRAS/MAPK resulted in synergistic growth inhibition employing CellTiter-Glo-based synergy assays. Further, to investigate the in vivo potential of this combination, we utilized a syngeneic orthotopic model of PDAC. Surprisingly, most mice were cured when treated with both ESK981 and trametinib while each individual treatment only modestly decreased tumor burden. Additionally, we established a patient-derived xenograft model where mice treated with a combination of ESK981 and trametinib (MEK inhibitor) or ESK981 and MRTX-1133 (KRASG12D inhibitor) displayed substantial tumor regression in comparison to single treatment or control groups. Taken together, the dual inhibition of PIKfyve and KRAS holds promise as a therapeutic strategy for PDAC treatment. Citation Format: Jasmine P. Wisniewski, Caleb Cheng, Bailey Jackson, Ahmet Korkaya, Sydney Peters, Yuanyuan Qiao, Costas A. Lyssiotis, Arul M. Chinnaiyan. Dual inhibition of PIKfyve and KRAS/MAPK as a potential for therapeutic strategy for pancreatic ductal 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 3300.

Abstract 3983: Antigen-presenting cancer-associated fibroblasts provide an alternate mechanism for CD4 T cell activation in murine pancreatic ductal adenocarcinoma

Abstract Despite the advent of immune checkpoint inhibitors (ICI) that have markedly changed the treatment landscape for select tumors, pancreatic ductal adenocarcinoma (PDAC) remains unresponsive to such an approach. Features of the PDAC tumor microenvironment that contribute to treatment resistance, including the influence of cancer-associated fibroblasts (CAF) on immune and tumor cells, remain poorly understood. Antigen-presenting CAFs (apCAFs) express MHC-II and activate CD4 T cells in genetically engineered PDAC mouse models, but are rarely found in human PDAC. In a human PDAC atlas consisting of six published single-cell RNA-sequencing datasets, we identified 370 apCAFs out of 8736 total CAFs, the majority of which were from one dataset. Understanding apCAF regulation can reveal how to promote their differentiation and enhance T cell activating capacity in PDAC. Methods: Two KPC clones that differ in sensitivity to ICIs, sKPC (sensitive) and rKPC (resistant), derived from the autochthonous KPC murine model of PDAC, were implanted orthotopically into the pancreas or subcutaneously into the flank of syngeneic C57BL/6 mice. Tumors were harvested at 14-28 days post implantation for quantification of T cells, dendritic cells, and CAFs. To evaluate function, apCAFs were sorted and CD11c+ and CD4+ T cells were isolated from tumors. Naïve CD4+ T cells were also isolated from OT-II mice. apCAFs and CD11c+ cells were pulsed with OVA and co-cultured with OT-II CD4+ T cells, or co-cultured with sKPC tumor infiltrating CD4+ T cells in the presence of endogenous peptides. Results: Total CAFs are equivalent between tumors, but apCAFs are significantly more abundant in sKPC tumors. Furthermore, the apCAF to dendritic cell ratio within these tumors ranged from 5:1 to 50:1. CD11c+ dendritic cells sorted from sKPC tumors and pulsed with OVA peptide robustly activate naïve OT-II CD4+ T cells, as expected from professional APCs; sorted apCAFs also activate naïve OT-II CD4+ T cells, although to a lesser degree. When apCAFs or CD11c+ dendritic cells are cultured with tumor-infiltrating CD4+ T cells, however, they upregulate CD4 activation markers to a similar extent. Conclusions: apCAFs are more abundant in tumors derived from ICI-sensitive KPC clones and greatly outnumber dendritic cells. Functionally, apCAFs from sKPC tumors stimulate tumor-derived CD4 T cells to the same degree as CD11c+ dendritic cells, implicating a role in activation of the immune response in ICI-sensitive tumors. Although a small proportion of the tumor microenvironment, the apCAF subset may be enhanced in number and function by CAF-targeted modulators to affect the antitumor response; transcriptomics analyses are currently underway to identify regulators of apCAFs. Such a strategy could provide a solution to the currently unmet need for new and more effective treatments for PDAC patients. Citation Format: Saumya Maru, Lalitya Andaloori, Kathryn Howe, Kabeer Munjal, James Leatherman, Edward J. Pearce, Elizabeth M. Jaffee. Antigen-presenting cancer-associated fibroblasts provide an alternate mechanism for CD4 T cell activation in murine pancreatic ductal 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 3983.

Abstract 5275: Celecoxib and chloroquine enhance the antitumor effect of immune checkpoint blockade therapy, in a syngeneic mouse model for pancreatic cancer

Abstract Immune checkpoint inhibitors (ICIs) have shown impressive clinical activities in some cancer types, but they have yet to demonstrate any meaningful clinical benefit in patients with pancreatic ductal adenocarcinoma (PDAC) except those with microsatellite instability high (MSI-H) tumors. Several recent studies showed that concomitant use of NSAIDs such as celecoxib by patients with certain cancers could improve the survival benefit of ICI treatment (e.g., Sebastian et al, Clin Lung Cancer, 2023;). Furthermore, autophagy inhibitors such as chloroquine were also reported to sensitize pancreatic tumors to the treatment of ICIs in mouse models for PDAC (Yamamoto, et al, Nature, 2020). We recently reported that the combination of chemotherapy (triple combination of nab-paclitaxel + gemcitabine + cisplatin) and a mouse surrogate of the IFc-enhanced anti-CTLA-4 antibody botensilimab, showed significantly improved antitumor activity in immune competent KPC syngeneic mouse model for PDAC [Tanne, et al, Cancer Res (13_Supplement), 2020]. In this study, we sought to determine whether or not the addition of celecoxib and/or chloroquine further improve the antitumor activity of triple chemotherapy and ICI in the syngeneic KPC model. We first found that celecoxib (30mg/kg P.O. QDx21) significantly enhanced the tumor growth inhibition when added to triple chemotherapy (Gemcitabine 70mg/kg I.P., Cisplatin 4mg/kg I.P., Nab-paclitaxel 25mg/kg I.V. days 1,4 and 7) plus the murine equivalents of botensilimab (100ug I.P. BIW for three weeks) and balstilimab (200ug I.P. BIW for three weeks) (p=0.004, N=10). We then performed a pilot study to assess if adding chloroquine could further improve the activity. While adding chloroquine (60mg/kg I.P. QDx21) alone did not significantly affect tumor growth the addition of both chloroquine and celecoxib greatly improve the tumor growth inhibition compared to just the triple chemotherapy and ICIs (p=0.009, N=5). Overall, our data showed that celecoxib or the combination of celecoxib and chloroquine could substantially sensitize the mouse pancreatic tumors to the treatment of chemotherapy and ICIs. (This work was supported in part by the Seena Magowitz Foundation and the Purple Pansies) Citation Format: Jaeger Moore, Dhan Chand, Daniel Levey, Daniel Von Hoff, Haiyong Han. Celecoxib and chloroquine enhance the antitumor effect of immune checkpoint blockade therapy, in a syngeneic mouse model for pancreatic cancer [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 5275.

Abstract 1602: Leukemia inhibitory factor (LIF)-factor XIIIA mediated macrophage-stromal crosstalk in pancreatic cancer

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy marked by a highly immunosuppressive tumor microenvironment (TME). Macrophages are known to promote immunosuppression and exhibit a profibrotic transcriptional profile with potential involvement in extracellular matrix (ECM) remodeling. Previously, we identified hyperactivation of cancer cell intrinsic cyclic AMP response element binding protein 1 (CREB) regulates leukemia inhibitory factor (LIF) to mediate macrophage infiltration and polarization within the TME of PDAC. Subsequently, we observed that disrupting LIF-LIF receptor (LIFR) signaling therapeutically not only diminishes the infiltration of tumor-associated macrophages (TAMs) but also results in a decrease in ECM deposition. This study delves into the potential regulatory pathway through which LIF induces remodeling of the ECM within the PDAC TME. Methods: We targeted LIF-induced macrophage-stromal crosstalk using the LIFR antagonist (EC359) in an orthotopically tumor implanted LSL-KrasG12D/+; Trp53 R172H/+; Pdx1Cre/+ (KPC) mice model of PDAC. Sirius red staining in tumor sections was performed to assess ECM (collagen) deposition. Moreover, we performed RNA transcriptomics-based analysis of recombinant (rLIF) induced bone marrow derived macrophages harvested from syngeneic C57BL/6 mice. The Cancer Genome Atlas (TCGA) pancreatic cancer (PAAD) data set along with single-cell RNA sequencing (scRNA seq) were employed to assess the expression of major downstream targets of LIF. To validate the RNA-seq results, we conducted immunohistochemical analysis (IHC) on mouse PDAC tissue sections and quantitative polymerase (qPCR) analysis on RAW 264 macrophage cell line treated with rLIF or KPC CREBWT PDAC tumor cells conditioned media. Results: We observed a drastic decrease in both TAM infiltration and, of note, ECM deposition in orthotopically implanted KPC pancreas tumor mice tissue treated with EC359 as compared to vehicle. Mechanistically, our RNA-seq analysis unveiled a significant upregulation of Factor XIIIA (FXIIIa), a major downstream target of LIF. Notably, TCGA data revealed that FXIIIa mRNA expression is upregulated across PDAC tumors marked by poor survival outcomes. Moreover, scRNA seq and IHC established that TAMs highly express FXIIIa in the PDAC TME. In exploring the effect of LIF-LIFR signaling in the ECM, mouse RAW 264.7 macrophage lines incubated in high LIF conditions confirmed transcriptional upregulation of ECM-associated proteins such as FXIIIa as well as fibronectin. Conclusion: Our investigation provides valuable insights into the possible mechanism by which LIF triggers ECM remodeling, thereby contributing to the desmoplastic stroma. Significantly, our findings propose that LIF-regulated FXIIIa signaling in macrophages serves as a plausible mediator of the LIF-induced ECM remodeling in PDAC. Citation Format: Nishah Jaferi, Siddharth Mehra, Varun Krishnamoorthy, Sudhakar Jinka, Anna Bianchi, Vanessa T. Garrido, Luis A. Nivelo, Ban Yuguang, Nagaraj S. Nagathihalli. Leukemia inhibitory factor (LIF)-factor XIIIA mediated macrophage-stromal crosstalk in pancreatic cancer [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 1602.

Abstract 1586: Unraveling the importance of pancreatic cancer extracellular signaling to endothelial cells within the tumor microenvironment

Abstract In many solid tumors, including pancreatic ductal adenocarcinoma (PDAC), the secretion of extracellular vesicles (EVs) has been shown to support tumor progression, chemotherapeutic resistance, and metastasis. Importantly, PDAC tumors are composed of up to 80% non-tumor cells and an extracellular matrix, yet no studies have been performed to determine which cells within PDAC tumors internalized PDAC EVs. Further, the RNA-binding protein HuR plays an important role in PDAC cells, supporting the stability and translation of transcripts that aid tumor cell stress responses. Our lab has recently found that EVs harbor distinct mRNA and phosphorylated protein cargoes from donor cells. Further, HuR knockout (KO) cells produce EVs with significantly different mRNAs and phosphorylated proteins that EVs isolated from HuR wildtype (WT) cells. Specifically, proteins relating to endothelial function and angiogenesis were significantly differentially phosphorylated. Considering the functional impact of EV cargoes on recipient cells, our study aims to identify the specific cell types in the tumor microenvironment that import PDAC EVs and investigate the role of PDAC cell HuR in this signaling process. We have generated human PDAC and mouse KrasG12D Trp53R172H driven (KPC) PDAC cell lines to express an EV reporter, PalmGRET. Utilizing these cells lines in an immunocompetent mouse model of PDAC, we found that endothelial cells are major importers of PDAC EVs. We next performed bulk RNA-sequencing on endothelial cells sorted from these tumors that have (GFP+) versus have not (GFP-) imported PDAC EVs to assess the functional impact of PDAC EVs. Subsequent studies will focus on delineating the importance of this signaling axis by ablating EV secretion in addition to assessing endothelial cell function when treated with EVs from HuR WT vs. KO cells. Collectively, our study sheds light on the preferential uptake of PDAC EVs by endothelial cells and highlights the potential role of tumor cell-intrinsic HuR in this signaling process. These findings expand our understanding of the interactions between PDAC and the tumor microenvironment, potentially paving the way for targeted therapeutic interventions in this devastating disease. Citation Format: Jennifer M. Finan, Yifei Guo, Alexandra Q. Bartlett, Kevin MacPherson, Valerie Calvert, Madeline D. Hedberg, Emanuel Petricoin, Rosalie Sears, Jonathan R. Brody. Unraveling the importance of pancreatic cancer extracellular signaling to endothelial cells within the tumor microenvironment [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 1586.

Abstract 5973: Targeting prolyl 4-hydroxylase subunit alpha 1 with a small molecule inhibitor, diethyl-pythiDC, reduces pancreatic ductal adenocarcinoma growth and metastasis

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease that has a 5-yearrelative survival rate of less than 9%. It is the fourth leading cause of cancer-associated mortality,and is projected to become the second leading cause of cancer-related deaths by 2030. Since most(~80%) PDACs are diagnosed at late stages (metastasized), there is an urgent need to identifymolecular determinants that regulate PDAC progression and serve as candidates for therapeutictargeting. Prolyl 4-hydroxylase subunit alpha 1 (P4HA1) is the major isoform overexpressed inmost cancers, including PDAC. In PDAC, high expression of P4HA1 is associated with tumorprogression and poor clinical outcomes. Thus, we investigated if targeting P4HA1 in PDAC witha small molecule inhibitor; diethyl-pythiDC, had an inhibitory effect on cell proliferation, tumorprogression/growth, and metastasis. Methods: To demonstrate the therapeutic efficacy of diethyl-pythiDC, we performed MTT, colonyformation, wound healing, Transwell, and western blot assays in various PDAC cell lines. Tumorgrowth and metastasis was evaluated with xenografts in NOD/SCID/IL2γ receptor-null (NSG)mice. Additionally, expression of P4HA1 in human PDAC and in adjacent normal pancreatictissues was assessed. Results: In human PDACs, there was elevated expression of P4HA1 protein relative to adjacentnormal pancreatic tissues. Treatment of various PDAC cells (S2VP10, MIA PaCa2, BxPC-3, andPANC-1) with diethyl-pythiDC reduced cell proliferation and colony formation, and inducedG2/M cell cycle arrest. Diethyl-pythiDC reduced migration and invasion of PDAC cells bymodulating epithelial-mesenchymal transition (EMT) markers (N-cadherin, E-cadherin, andvimentin). In addition, diethyl-pythiDC reduced the expression of argonaute-2 (AGO2), acomponent of microRNA biogenesis implicated in tumorigenesis, and its downstream target,matrix metalloproteinase (MMP1). In preclinical animal models of PDAC, diethyl-pythiDCreduced tumor growth and metastasis. Furthermore, in xenograft tumors, diethyl-pythiDCtreatment reduced the expression of AGO2, MMP1, and the proliferative marker, PCNA, andmodulated proteins of the EMT. Conclusions: Treatment with diethyl-pythiDC reduces PDAC progression by decreasing cellproliferation, arresting cells in the G2/M phase, downregulating AGO2/MMP1 expression, andmodulating the EMT. These findings suggest that targeting P4HA1 by diethyl-pythiDC could be aviable strategy to improve treatment for PDACs, particularly those expressing high levels ofP4HA1. They also provide a basis to conduct clinical trials to assess the utility of targeting P4HA1by diethyl-pythiDC. Citation Format: Farrukh Afaq, Mohd Khushman, Prachi Bajpai, Sameer Al Diffalha, Dennis Otali, Sooryanarayana Varambally, Upender Manne. Targeting prolyl 4-hydroxylase subunit alpha 1 with a small molecule inhibitor, diethyl-pythiDC, reduces pancreatic ductal adenocarcinoma growth and metastasis [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 5973.

Abstract 6749: A dendritic cell targeted nanosystem to overcome immune suppression and enhance the efficacy of the standard of care for pancreatic cancer

Abstract The development of novel therapies for pancreatic ductal adenocarcinoma (PDAC) remains an urgent unmet medical need, as it was proven to be refractory to most conventional anti-neoplastic therapies. PDAC is characterized by highly dense stroma, immunosuppressive tumor microenvironment (TME), high resistance to chemotherapy, and poor presentation of tumor-associated antigens (TAA) by dendritic cells (DC), which results in low immune cell infiltration to the tumor site. To that end, we designed a DC-targeted nanovaccine (NV) containing PDAC TAA and TLR agonists to modulate the PDAC immune-microenvironment. In recent years, the combination of immunotherapy with chemotherapy has been explored for PDAC therapy to improve efficacy. Therefore, we demonstrate the effect of our NV on the anti-tumor immune-mediated response in PDAC-bearing mice, alone and in combination with Gemcitabine and Nab-Paclitaxel (Gem/NabP). Our DC-targeted NV was formulated by the double emulsion method and loaded with PDAC’s TAA and immune potentiators. We conjugated the NV to a mannose moiety as a targeting moiety for the mannose receptor expressed on DC to increase the NV uptake, which resulted in the enhanced presentation of the encapsulated TAA. Followed by physicochemical characterization and evaluation of preclinical safety of the NV, the stimulation of T cell-specific response against PDAC tumor was assessed in vivo and ex vivo. The NV induced significant changes in PDAC’s TME, such as increased CD8+ T cells, decreased CD4+ T regulatory cells, and induced memory immunity in the tumor site. The combination of NV and Gem/NabP inhibited tumor growth and prolonged survival compared to mice treated with Gem/NabP alone. This could also be related to the immunogenic cell death effect caused by the chemotherapies. In addition to our mice model of PDAC, we also established a patient-derived model, in which we generate 3D-spheroids from the patient’s tumor and activate PBMCs with our NV from the same patient. This unique 3D model enables us to evaluate ex vivo the NV effect in a more clinically relevant manner. The NV proposed herein could induce a strong antigen-specific immune response against PDAC with restricted tumor growth while re-shaping PDAC immunosuppressive TME. Furthermore, our 3D patient-derived PDAC model allows us to assess the ability of our NV to generate specific immune responses in patients and to test other possible drug combinations predicting the clinical outcome. Citation Format: Ron Kleiner, Daniella Vaskovich-Koubi, Rita Acúrcio, Barbara Carreira, Helena Florindo, Ronit Satchi-Fainaro. A dendritic cell targeted nanosystem to overcome immune suppression and enhance the efficacy of the standard of care for pancreatic cancer [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 6749.

Abstract 3874: Adaptive heterogeneity enables the survival of residual malignant PDAC cells in response to RAS-GTP inhibition

Abstract More than 90% of human pancreatic ductal adenocarcinoma (PDAC) cases are driven by activating mutations in KRAS. RMC-7977 is a potent inhibitor of GTP-bound RAS proteins (RAS(ON)), including both wild type and mutant variants of KRAS, NRAS, and HRAS. The related investigational agent, RMC-6236, is a first-in-class, potent, orally bioavailable, RASMULTI(ON) inhibitor currently in Phase 1/1b clinical trials (NCT05379985). We performed preclinical studies in a range of models of PDAC, including the highly chemoresistant K-rasLSL.G12D/+, p53LSL.R172H/+, Pdx1Cretg/+ (KPC) genetically engineered mouse. RMC-7977 exhibited broad anti-tumor activity at tolerable doses, provoking radiographic responses in KPC pancreatic tumors and extending overall survival by 3-fold, the largest response observed yet in this model. RMC-7977 dosing produced a metronomic effect on RAS signaling in tumor and normal tissues, with full pathway inhibition at 4 hours post treatment that was restored by 24 hours. This pattern yielded tumor-selective effects on apoptosis and proliferation, consistent with RAS oncogene addition in PDAC. To understand the dynamic response of malignant cells following RAS-GTP inhibition, we did single cell RNA sequencing on KPC pancreatic tumors treated with RMC-7977 or vehicle at multiple timepoints. Using the ARACNe and VIPER algorithms [Maroling., et al. 2006; Alvarez., et al. 2016], we performed regulatory network analysis on the expression profiles of >210,000 cells to calculate the activities of >5000 transcriptional regulatory proteins per cell. Additionally, we assessed the impact of treatment on malignant cell subtypes as previously identified by our team based on their sets of hyperactivated developmental transcription factors [Laise., et al. 2022]. As expected, RAS pathway transcription factors, such as FOS and JUN, were repressed relative to controls in malignant cells by 4 hours after treatment with RMC-7977. However, at 24 hours, responses varied by cellular subtype: well-differentiated Gastrointestinal Lineage State (GLS) cells had restored MAPK activity, while poorly differentiated Morphogenic State (MOS) cells were still inactivated. Strikingly, we found that after one week of treatment (in actively regressing tumors, representing a state of residual disease), nearly all malignant cells had assumed the GLS state. Acquisition of resistance after weeks or months of treatment was associated with a restored diversity of malignant cell states, suggesting that the GLS state serves as a regulatory “safe harbor” in which residual malignant cells can undergo evolution and adaptation. Mechanistically, we found that RAS pathway signaling directly activates transcriptional regulators that drive the MOS state, elucidating an early adaptive response to RAS-GTP inhibition that enables residual cells to survive treatment prior to development of acquired resistance. Citation Format: Lorenzo Tomassoni, Urszula N. Wasko, Alvaro C. Garcia, Tanner C. Dalton, Pasquale Laise, Stephen A. Sastra, Carmine F. Palermo, Andrea Califano, Kenneth P. Olive. Adaptive heterogeneity enables the survival of residual malignant PDAC cells in response to RAS-GTP inhibition [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 3874.