Abstract C001: Transforming Growth Factor-β Blockade in Pancreatic Cancer Enhances Sensitivity to Combination Chemotherapy in Mice

Abstract Background: TGFβ plays a critical role in promoting pancreatic tumor progression, attenuating CD8 T cell proliferation and cytokine production, enhancing the differentiation of myofibroblasts and the deposition of extracellular matrix. However, single agent TGFβ blockade has shown limited efficacy in mouse models of pancreatic cancer. Methods: We evaluated the TGFβ- blocking antibody NIS793 in combination with gemcitabine/nanoparticle (albumin-bound) - paclitaxel or FOLFIRINOX (folinic acid FOL, 5-fluorouracil F, irinotecan IRI and oxaliplatin OX) in orthotopic pancreatic cancer models. Single-cell RNA sequencing and immunofluorescence were used to evaluate changes in tumor cell state and the tumor microenvironment. Results: Blockade of TGFβ with chemotherapy reduced tumor burden in poorly immunogenic pancreatic cancer, without affecting the metastatic rate of cancer cells. Efficacy of combination therapy was not dependent on CD8 T cells, because response to TGFβ blockade was preserved in CD8-depleted or recombination activating gene 2 (RAG2-/-) mice. TGFβ blockade decreased total α-smooth muscle actin-positive fibroblasts but had minimal effect on fibroblast heterogeneity. Bulk RNA sequencing on tumor cells sorted ex vivo revealed that tumor cells treated with TGFβ blockade adopted a classical lineage consistent with enhanced chemosensitivity, and immunofluorescence for cleaved caspase 3 confirmed that TGFβ blockade increased chemotherapy-induced cell death in vivo. Conclusions: TGFβ regulates pancreatic cancer cell plasticity between classical and basal cell states. TGFβ blockade in orthotropic models of pancreatic cancer enhances sensitivity to chemotherapy by promoting a classical malignant cell state. This study provides scientific rationale for evaluation of NIS793 with FOLFIRINOX or gemcitabine/nanoparticle (albumin-bound) paclitaxel chemotherapy backbone in the clinical setting and supports the concept of manipulating cancer cell plasticity to increase the efficacy of combination therapy regimens. This study provided the scientific rationale for the evaluation of TGFβ with both chemotherapy backbones in the clinical setting. Ongoing evaluation of samples from the stopped clinical trials will inform as to the role of TGFb in human PDAC. Citation Format: Li Qiang, Megan Hoffman, Lestat Ali, Jaime Ivan Castillo Silva, Lauren Kageler, Ayantu Temesgen, Patrick Lenehan, Jennifer Wang, Elisa Bello, Victoire Cardot-Ruffino, Giselle Uribe, Annan Yang, Michael Dougan, Andrew Aguirre, Srivatsan Raghavan5, Marc Pelletier, Viviana Cremasco, Stephanie Dougan. Transforming Growth Factor-β Blockade in Pancreatic Cancer Enhances Sensitivity to Combination Chemotherapy in Mice abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84 (17 Suppl₂): Abstract nr C001.