Pancreatic Ductal Adenocarcinoma Patient-derived Organoids Research Articles

A pancreatic cancer organoid-in-matrix platform shows distinct sensitivities to T cell killing

Poor treatment responses of pancreatic ductal adenocarcinoma (PDAC) are in large part due to tumor heterogeneity and an immunosuppressive desmoplastic tumor stroma that impacts interactions with cells in the tumor microenvironment (TME). Thus, there is a pressing need for models to probe the contributions of cellular and noncellular crosstalk. Organoids are promising model systems with the potential to generate a plethora of data including phenotypic, transcriptomic and genomic characterization but still require improvements in culture conditions mimicking the TME. Here, we describe an INTERaction with Organoid-in-MatriX ("InterOMaX") model system, that presents a 3D co-culture-based platform for investigating matrix-dependent cellular crosstalk. We describe its potential to uncover new molecular mechanisms of T cell responses to murine KPC (LSL-KrasG12D/+27/Trp53tm1Tyj/J/p48Cre/+) PDAC cells as well as PDAC patient-derived organoids (PDOs). For this, a customizable matrix and homogenously sized organoid-in-matrix positioning of cancer cells were designed based on a standardized agarose microwell chip array system and established for co-culture with T cells and inclusion of stromal cells. We describe the detection and orthogonal analysis of murine and human PDAC cell populations with distinct sensitivity to T cell killing that is corroborated in vivo. By enabling both identification and validation of gene candidates for T cell resistance, this platform sets the stage for better mechanistic understanding of cancer cell-intrinsic resistance phenotypes in PDAC.

Abstract 5: Cytosine base editor ameliorates the safety profile of TCR edited T cells for the adoptive cell therapy of gastrointestinal tumors

Abstract Among gastrointestinal tumors, colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) are major unmet medical needs, with a high mortality rate mainly related to the onset of metastases, hindering the therapeutic efficacy of conventional treatments. Adoptive Cell Therapy (ACT) with TCR-edited T cells is a promising therapeutic strategy for patients with late-stage tumors, but its applicability is limited by the paucity of TCRs targeting relevant tumor antigens and the presence of an immunosuppressive tumor microenvironment. Moreover, the safety of the therapeutic cellular products, generated by genome editing tools, is fundamental for an effective and rapid clinical translation. With the aim of improving the safety profile of T-cell based therapeutic products manufactured by genome editing, we evaluated the efficacy and safety of cytosine base editor (CBE). We disrupted the endogenous TCR to redirect T cells specificity toward tumor cells, and TIGIT, a major inhibitory molecule in gastrointestinal tumors to enhancing T cell ability to counteract immunosuppression. Beyond the high efficiency of CBE in simultaneously disrupting the target genes, we observed only marginal sgRNA-dependent and -independent off-target events as measured by targeted sequencing of the top predicted off-target loci and by ultra-deep whole exome sequencing, respectively. In addition, unlike CRISPR/Cas9-treated cells, we could not detect translocations in CBE edited T cells. To select the antigens to target by engineered T cells, we investigated published datasets and identified 19 relevant tumor-associated antigens. By clonal tracking of the TCR repertoire of T cells stimulated with autologous APCs loaded with the selected antigens, we isolated 5 different TCRs specificities, including mesothelin. Importantly, these antigens are expressed in our cohort of primary and metastatic PDAC and CRC patients. TCR-edited T cells displayed anti-tumor activity against PDAC cell lines, CRC and PDAC patient-derived organoids while sparing HLA-unrelated and antigen-negative controls. To boost the efficacy of anti-tumor T cells, we coupled TIGIT disruption with TCR editing. By challenging TCR-edited TIGITKO T cells in vitro and in an orthotopic model of CRC liver metastases, we observed that TIGIT disruption can ameliorate the ability of tumor-specific T cells to control tumor growth. Our findings suggest that base editors can generate cellular products with a better safety profile and a promising therapeutic efficacy in gastrointestinal tumors. Citation Format: Martina Spiga, Alessia Potenza, Stefano Beretta, Alessia Airaghi, Chiara Iozzi, Martina Fiumara, Samuele Ferrari, Neda Mohammadi, Oronza Botrugno, Maximilian Reichert, Maria Pia Protti, Stefano Crippa, Massimo Falconi, Luigi Naldini, Eliana Ruggiero, Chiara Bonini. Cytosine base editor ameliorates the safety profile of TCR edited T cells for the adoptive cell therapy of gastrointestinal 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 5.

Abstract 233: Cabozantinib changes the landscape of the pancreatic tumor microenvironment and improves the efficacy of pembrolizumab

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with an approximate 10% 5-year survival rate. PDAC patients rarely benefit from treatment with immune checkpoint inhibitors (ICIs) due to a tumor microenvironment (TME) associated with constrained effector T cell infiltration, and the presence of a suppressive myeloid cell population. Objective: To identify a combinatorial therapeutic strategy targeting the myeloid derived suppressor cells (MDSCs) and cancer associated fibroblasts (CAFs) within the PDAC TME to increase the efficacy of ICIs. Methods: C57BL/6 mice were orthotopically transplanted with syngeneic 7940b PDAC cells derived from transgenic KPC mouse. 7 days post-transplantation mice were treated with InVivoPlus anti-mouse PD-1 (CD279), cabozantinib (cabo, tyrosine kinase inhibitor) or a combination of drugs for a further 7 days. NanoString CosMx™ spatial molecular imaging (CosMx™ SMI) was performed using FFPE sections collected from core biopsies and surgically resected tissues. PDAC patient derived organoids (PDOs) were generated from the core biopsies or surgical biospecimens. Cancer-associated fibroblasts (CAFs) were isolated from the organoid cultures. Autologous immune cells (IMM) were cultured from patient peripheral blood mononuclear cells. PDO/CAF/IMM co-cultures were used to predict the patient response to cabo plus pembrolizumab combinatorial therapy. Results: Mice treated with a combination of anti-PD-1 and cabo exhibited significant EpCAM/PD-L1-expressing cell death that correlated with increased CTL proliferation and decreased PMN-MDSC death. Mice that were depleted of CD8+ CTLs using anti-CD8 antibody in vivo did not exhibit tumor cell death in response to combinatorial therapy and thus supporting the role of CTLs in driving effective immunotherapy in combination with cabozantinib treatment. Unexpectedly, a significant decrease in extracellular matrix protein fibronectin was observed. Human PDOs orthotopically transplanted into NSG mice developed pathology consistent with human PDAC with strong expression of CD44v9, IL6, vimentin and αSMA. Using PDAC PDO/CAFs/IMM co-cultures, pembro significantly induced tumor cell death in the presence CTLs, MDSCs significantly inhibited this response. Depletion of MDSCs using cabo in the PDO/CAFs/IMM co-cultures resulted in a significant increase in tumor cell death with a concomitant increase in CTL proliferation. Compared to core biopsies, surgical biospecimens collected post-standard of-care demonstrated a shift in cell populations within defined NICHES (local cellular TME) whereby there was 1) increases MDSCs, 2) change in CAFs phenotype and 3) increased expression of CD44v9. Conclusions: Cabozantinib depletes the PDAC TME of MDCSs leading to sensitization to ICI and tumor cell death and thus offers a potential combinatorial therapeutic approach. Citation Format: Pritha Adhikary, Jayati Chakrabarti, Meenu Priya Resmi, Jiang Wang, Davendra Sohal, Rachna T. Shroff, Syed A. Ahmad, Yana Zavros. Cabozantinib changes the landscape of the pancreatic tumor microenvironment and improves the efficacy of pembrolizumab [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 233.

Genetic assessment of pathogenic germline alterations in lysosomal genes among Asian patients with pancreatic ductal adenocarcinoma

BackgroundLysosomes are closely linked to autophagic activity, which plays a vital role in pancreatic ductal adenocarcinoma (PDAC) biology. The survival of PDAC patients is still poor, and the identification of novel genetic factors for prognosis and treatment is highly required to prevent PDAC-related deaths. This study investigated the germline variants related to lysosomal dysfunction in patients with PDAC and to analyze whether they contribute to the development of PDAC.MethodsThe germline putative pathogenic variants (PPV) in genes involved in lysosomal storage disease (LSD) was compared between patients with PDAC (n = 418) and healthy controls (n = 845) using targeted panel and whole-exome sequencing. Furthermore, pancreatic organoids from wild-type and KrasG12D mice were used to evaluate the effect of lysosomal dysfunction on PDAC development. RNA sequencing (RNA-seq) analysis was performed with established PDAC patient-derived organoids (PDOs) according to the PPV status.ResultsThe PPV in LSD-related genes was higher in patients with PDAC than in healthy controls (8.13 vs. 4.26%, Log2 OR = 1.65, P = 3.08 × 10–3). The PPV carriers of LSD-related genes with PDAC were significantly younger than the non-carriers (mean age 61.5 vs. 65.3 years, P = 0.031). We further studied a variant of the lysosomal enzyme, galactosylceramidase (GALC), which was the most frequently detected LSD variant in our cohort. Autophagolysosomal activity was hampered when GALC was downregulated, which was accompanied by paradoxically elevated autophagic flux. Furthermore, the number of proliferating Ki-67+ cells increased significantly in pancreatic organoids derived from Galc knockout KrasG12D mice. Moreover, GALC PPV carriers tended to show drug resistance in both PDAC cell line and PDAC PDO, and RNA-seq analysis revealed that various metabolism and gene repair pathways were upregulated in PDAC PDOs harboring a GALC variant.ConclusionsGenetically defined lysosomal dysfunction is frequently observed in patients with young-onset PDAC. This might contribute to PDAC development by altering metabolism and impairing autophagolysosomal activity, which could be potentially implicated in therapeutic applications for PDAC.

Abstract B044: Bromodomain and Extra-Terminal Protein inhibition decreases pancreatic cancer proliferation via MYC-independent pathways

Abstract Introduction: The bromodomain and extra-terminal (BET) protein family contains proteins which have evolutionarily conserved bromodomains (BRDs) that specifically recognize acetylated lysine residues on the histone tails of chromatin and regulate gene transcription. Deregulation of these BRD-containing proteins has been seen in carcinogenesis as they are also known to play role in the regulation of the cell-cycle and MYC oncogenes. BMS-986158 is an oral BET inhibitor which has been used in the clinical trials for both hematologic and advanced solid tumor cancers. We hypothesized that BET inhibition (BETi) decreases pancreatic ductal adenocarcinoma (PDA) proliferation. Methods: Pancreatic cancer cell lines and patient-derived cell-lines (PDCLs) were treated with 2.5 to 100nM BMS-986158 for 72 hours to study dose-response effect with Incucyte. We performed RNA-seq, qPCR, protein analysis, and flow cytometry to evaluate comprehensive changes and underlying mechanisms/pathways including epithelial to mesenchymal transition (EMT) and the cancer stem cell (CSC) phenotype. Various doses of BMS-986158 were used in PDCL and PDA patient-derived organoids (PDO) in combination with chemotherapy drug to evaluate combinational effects. Results: We found that BETi induced dose-dependent decrease in growth of PDA and PDCLs and induced cancer cell death. BETi demonstrated PDO growth inhibition which was enhanced when combined with gemcitabine and paclitaxel chemotherapy. Next, we found that BETi did not affect MYC expression but decreased expression of the SNAI1 (a mesenchymal marker) protein and increased E-cadherin protein expression in PDA cell line and PDO consistent with decreased activation of an EMT program. BETi also decreased expression of CD133, a marker of CSCs in PDO. BETi also induced G1/S Phase cell cycle arrest in PDA PDCLs. Furthermore, RNA-seq studies revealed that BETi treatment inhibits KRAS pathway and upregulates pathways involved in metabolism of lipids and lysosomal degradation. RNA-seq and qPCR demonstrated that GPX3 (glutathione peroxidase 3, a key protein in reactive oxygen species response) gene expression is upregulated in BETi treated samples. Conclusions: Thus, our data demonstrate that BETi through BMS-986158 is an additional therapy for inhibiting PDA growth through mechanisms that are independent of MYC pathway, inhibition of abnormal lipid metabolism and scavenging of reactive oxygen species. Citation Format: Manjul Rana, Rita G. Kansal, Jie Fang, Benjamin T. Allen, Jun Yang, Evan S. Glazer. Bromodomain and Extra-Terminal Protein inhibition decreases pancreatic cancer proliferation via MYC-independent pathways [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 B044.

Combined Systemic Drug Treatment with Proton Therapy: Investigations on Patient-Derived Organoids.

Simple SummaryRadiotherapy is part of the standard of care for many solid tumors. In pancreatic ductal adenocarcinoma (PDAC), good responses to radiotherapy can only be observed in a minority of patients. In our study, we used PDAC patient-derived organoids (PDO) to investigate alternative radiotherapy approaches for PDAC, such as proton irradiation and combined radiochemotherapy (RCT). Although only very distinct differences in treatment response could be identified, we show the utility of PDOs in translational proton research and found synergistic effects of combined treatments with chemotherapy and proton irradiation in individual PDOs.To optimize neoadjuvant radiochemotherapy of pancreatic ductal adenocarcinoma (PDAC), the value of new irradiation modalities such as proton therapy needs to be investigated in relevant preclinical models. We studied individual treatment responses to RCT using patient-derived PDAC organoids (PDO). Four PDO lines were treated with gemcitabine, 5-fluorouracile (5FU), photon and proton irradiation and combined RCT. Therapy response was subsequently measured via viability assays. In addition, treatment-naive PDOs were characterized via whole exome sequencing and tumorigenicity was investigated in NMRI Foxn1nu/nu mice. We found a mutational pattern containing common mutations associated with PDAC within the PDOs. Although we could unravel potential complications of the viability assay for PDOs in radiobiology, distinct synergistic effects of gemcitabine and 5FU with proton irradiation were observed in two PDO lines that may lead to further mechanistical studies. We could demonstrate that PDOs are a powerful tool for translational proton radiation research.

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 (<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.

Abstract PO-098: Longitudinal profiling of pancreatic cancer patients identifies interleukin-8 as a mediator of myeloid-epithelial crosstalk

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer-related death in the US. A key hallmark of this disease is that, while tumors initially show susceptibility to standard chemotherapeutic agents, most patients eventually develop resistance, leading to poor survival. While the mechanisms of chemoresistance are unclear, murine studies have implicated the myeloid compartment of the tumor immune microenvironment. Correlative data in human tumors supports this notion, however, mechanistic studies are lacking, thus impairing translation to the clinic. The study of human pancreatic cancer has historically been challenging due to difficulty of fresh biospecimen acquisition, patient heterogeneity, and a diverse tumor microenvironment. Moreover, the vast majority of pancreatic cancer patients do not qualify for surgical resection, further limiting tissue availability. We have overcome these difficulties by developing a pipeline to analyze human tumor samples and matched blood using high-fidelity techniques including single-cell RNA sequencing (scRNAseq) and mass cytometry (CyTOF), together with establishment of organoids from the same tumors. Notably, in this pipeline we can use small amounts of tissue from endoscopic fine needle biopsies, thus allowing us to sample tumors from patients at any disease stage. Results: We performed CyTOF on longitudinally-matched peripheral blood mononuclear cells (PBMCs) from 30 patients and single-cell RNA sequencing on 6 patients in the treatment naïve and on-treatment (FOLFIRINOX) state. CyTOF revealed distinct alterations in the myeloid population, with a shift toward CXCR2hiPD-L1hi granulocytes with FOLFIRINOX treatment over time. Analysis of PBMCs from scRNAseq showed a distinct myeloid gene signature with FOLFIRINOX and in particular highlighted interleukin-8 (IL8), a chemokine involved in myeloid cell chemotaxis that is associated with poor prognosis in pancreatic cancer. Further mapping of IL8 in tumor tissue by scRNAseq showed that it is highly expressed in subpopulations of tumor epithelial cells and tumor-infiltrating granulocytes. IL8-high tumor-infiltrating granulocytes also highly expressed VEGF and CXCR4, suggesting immunosuppressive and angiogenic roles. IL8-high tumor epithelial cells were found to have a basal-like phenotype and also expressed a network of other chemokines including CXCL1, CXCL3, CXCL5, which are known to recruit immunosuppressive myeloid cells. Conclusions: Through longitudinal and multimodal mapping using PDAC patient blood and tumor biospecimens, we have identified IL8 as a potential mediator of epithelial-myeloid crosstalk in PDAC chemoresistance and tumor aggression. Validation studies using an all-human co-culture system of PDAC patient-derived organoids and myeloid cells are currently underway. Citation Format: Eileen S. Carpenter, Samantha Kemp, Padma Kadiyala, Nina Steele, Ahmed Elhossiny, Stephanie The, Valerie Gunchick, Rémy Nicolle, Michelle Anderson, Wenting Du, Carlos Espinoza, Richard Kwon, Erik-Jan Wamsteker, Anoop Prabhu, Allison Schulman, Vaibhav Sahai, Timothy Frankel, Filip Bednar, Marina Pasca di Magliano. Longitudinal profiling of pancreatic cancer patients identifies interleukin-8 as a mediator of myeloid-epithelial crosstalk [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-098.

Shared extracellular vesicle miRNA profiles of matched ductal pancreatic adenocarcinoma organoids and blood plasma samples show the power of organoid technology

Extracellular vesicles (EV) are considered as a promising diagnostic tool for pancreatic ductal adenocarcinoma (PDAC), a disease with a poor 5-year survival that has not improved in the past years. PDAC patient-derived 3D organoids maintain the intratumoral cellular heterogeneity, characteristic for the tumor in vivo.Thus, they represent an ideal in vitro model system to study human cancers. Here we show that the miRNA cargo of EVs from PDAC organoids largely differs among patients. However, we detected a common set of EV miRNAs that were present in matched organoids and blood plasma samples of individual patients. Importantly, the levels of EV miR-21 and miR-195 were higher in PDAC blood EV preparations than in healthy controls, albeit we found no difference compared to chronic pancreatitis (CP) samples. In addition, here we report that the accumulation of collagen I, a characteristic change in the extracellular matrix (ECM) in both CP and PDAC, largely increases EV release from pancreatic ductal organoids. This provides a possible explanation why both CP and PDAC patient-derived plasma samples have an elevated amount of CD63 + EVs. Collectively, we show that PDAC patient-derived organoids represent a highly relevant model to analyze the cargo of tumor cell-derived EVs. Furthermore, we provide evidence that not only driver mutations, but also changes in the ECM may critically modify EV release from pancreatic ductal cells.

Cancer-initiating cells in human pancreatic cancer organoids are maintained by interactions with endothelial cells.

Pancreatic ductal adenocarcinoma (PDAC) shows poor prognosis and high malignancy due to the presence of cancer-initiating cells (CICs) and characteristics of the tumor microenvironment (TME). Organoids are useful for studying PDAC, and establishing organoids is dependent on stem cell growth factors, including Wnt signaling. Herein, using a conventional organoid culture system, we demonstrated that CD44(+)CD24(+) and CD44(+)CD24(+)EpCAM(+) CICs were enriched >65% in a PDAC patient-derived organoid. CICs expressing CD44 formed lumen structures by gathering into circles. Additionally, organoid-derived CD44(-) cancer cells were capable of organoid re-formation and could be re-programed as CD44-expressing CICs in the organoid culture system. To mimic a TME absent artificial stem cell growth factors, a PDAC organoid with vascular niche was established. CICs in the PDAC tumor organoid were maintained by paracrine effects and direct interactions with endothelial cells. Interestingly, CD44(+) cells in PDAC tumor tissue were detected primarily in the vascular niche. Inhibiting both Wnt and Notch signaling in endothelial cells suppressed organoid formation and the maintenance of CD24(+)CD44(+) CICs. Collectively, our results suggest that PDAC patient-derived organoids maintain CICs by interacting with endothelial cells via Wnt and Notch pathways.

Abstract 3198: Therapeutic potential of MET inhibitor combined with immune checkpoint blockade in pancreatic cancer

Abstract Novel Combination Therapeutic Targeting of the Immune Checkpoint PD-1 and c-MET in Pancreatic Cancer Introduction: Therapeutic regimens incorporating immune checkpoint inhibitors (ICIs) have improved survival in many cancers, but have had little impact in pancreatic ductal adenocarcinoma (PDAC). We previously discovered that these ICIs directly target autonomously expressed and functional PD-1 on PDAC cells. We sought to investigate downstream effectors of PD-1 signaling in PDAC cells as potential novel therapeutic targets. Methods: We performed a Phospho Explorer Array, which measures the levels of over 200 phospho-specific antibodies and their corresponding total proteins, to determine activated signaling pathways following exposure of PDAC cells to PD-L1 (the ligand for PD-1). Upon detecting upregulation of PD-1 mediated MET signaling, we verified MET pathway activation by exposing PDAC cells (MIAPaCa-2 and PANC-1) to PD-L1 and measuring levels of phosphorylated MET by immunoblotting. Then, we tested whether the MET small molecule inhibitor blocked PD-1 mediated MET signaling. Finally, PDAC patient-derived organoids (PDOs) were utilized to test the cytotoxicity of ICIs alone or in combination with cabozantinib. Results: The phospho-protein array revealed 10-fold upregulation of MET activity followed exposure of PDAC cells to PD-L1. Western blot assay verified increased levels of MET phosphorylation that varied in a time-dependent manner following PD-L1 treatment in both PANC-1 and MIAPaCa-2 cell lines. Pre-treatment of PDAC cells with cabozantinib completely blocked PD-1/PD-L1 mediated MET phosphorylation. By CellTiter-Glo assay the IC50 of cabozantinib was calculated in MIAPaCa-2 and PANC-1 cells as 9.5 µM and 8.6 µM, respectively. Combining cabozantinib with clinical grade anti-PD-1 monoclonal antibodies nivolumab and pembrolizumab revealed synergistic cytotoxicity in PDAC cells and PDOs. Conclusion: In these preliminary studies, we report PD-1 activation of the MET pathway and synergy killing of PDAC cancer models with novel combination therapy of cabozantinib and ICIs in PDAC. This positive data warrants further exploration of the interaction of MET with the PD-1/PD-L1 axis and its role in PDAC progression. Note: This abstract was not presented at the meeting. Citation Format: Mei Gao, Miranda Lin, Yachao Yang, Joseph Kim. Therapeutic potential of MET inhibitor combined with immune checkpoint blockade in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3198.