PKCι regulates the expression of PDL1 through multiple pathways to modulate immune suppression of pancreatic cancer cells

To investigate the impact of oncogenic protein kinase C isoform iota (PKC iota) on the microenvironment and the immunogenic properties of pancreatic tumors, we prohibit PKC iota activity in various pancreatic ductal adenocarcinoma (PDAC) cell lines and co-culture them with human natural killer NK92 cells. The results demonstrate that PKC iota suppression enhances the susceptibility of PDAC to NK cytotoxicity and promotes the degranulation and cytolytic activity of co-cultured NK92 cells. Mechanistic studies pinpoint that downstream of KRAS, both YAP1 and STAT3 are recruited by oncogenic PKC iota to elevate the expression of PDL1, contributing to constitute an immune suppressive microenvironment in PDAC. Co-culture with NK92 further induces PDL1 upregulation via STAT3 to stimulate immune escape of PDAC cells. Subsequently, inhibition of PKC iota in PDAC alleviates the immune suppression and enhances the cytotoxicity of NK92 towards PDAC through restraining PDL1 over expression. Combined with PD1/PDL1 blocker, PKC iota inhibitor remarkably elevates the cytotoxicity of NK92 against PDAC cells in vitro, establishing PKC iota inhibitor as a promising candidate for boosting the immunotherapy of PDAC.