Abstract B77: PORCN inhibition prolongs survival, decreases tumor burden, and alters the immune microenvironment in ovarian cancer

Background: Wnt/β-catenin pathway upregulation has been correlated with immune evasion in multiple cancers, including epithelial ovarian cancer (EOC). Porcupine (PORCN) is an enzyme necessary for cells to produce WNT ligand, which is necessary for the activation of the pathway. Our hypothesis was that the administration of a PORCN inhibitor (CGX1321) would decrease Wnt signaling and thereby lead to a decrease in immune evasion, creating a “hot” tumor microenvironment (TME), which would result in increased survival and a decrease tumor burden. Methods: RNA sequencing was performed in a cohort of primary ovarian cancer samples. CGX1321 was administered to C57Bl6 mice injected intraperitoneally with ID8 or ID8p53−/− cells. Tumor growth was measured by bioluminescence and omental weight. H&E slides were analyzed for amount of tumor in the omentum. Amount of tumor-infiltrating lymphocytes (TILs), Tregs, dendritic cells (DCs), macrophages, and monocytes in the TME were quantified via flow cytometry. CD11c-cre x β-catenin-flox C57Bl6 mice, a mouse model with no DC-intrinsic β-catenin, and the administration of anti-CD8β antibody were used to evaluate tumor burden with and without CGX1321. Results: Increased Wnt activity was correlated with a decreased T-cell signature in our human ovarian cancer samples. Treatment with CGX1321 prolonged survival (P=0.0001) and decreased omentum weight (P=0.0056) in mice injected with ID8 cells. H&E slides revealed decreased amount of tumor in the omentum with treatment. There was an increase of DCs (P=0.0159), macrophages (P=0.0079), and monocytes (P value=0.0079) with treatment, which was only significant for mice injected with ID8 cells, not ID8p53−/− mice. Tumor burden was decreased in CD11c-cre x β-catenin-flox mice (P=0.1014) without treatment, and with CGX 1321 treatment (P=0.0450). Tumor burden was not decreased with CGX1321 treatment in the absence of CD8+ T-cells (P=0.3175). Conclusions: Consistent with EOC TCGA data, we identified a correlation between increased Wnt signaling and decreased T-cell signature (i.e., “cold” tumor). ID8 cells have a higher level of total β-catenin and expression of WNT related genes compared with ID8p53−/−, which may explain the prolonged survival, decreased tumor burden, and more profound increase of DCs, macrophages, and monocytes in the TME. This may suggest a reliance on these cells for tumor recognition with PORCN inhibition. Furthermore, tumor burden was decreased in a DC-intrinsic β-c