Downregulation of the CCK-B Receptor in Pancreatic Stellate Cells Blocks Molecular Proliferative Pathways and Increases Apoptosis to Decrease Pancreatic Cancer Growth In Vitro.

Pancreatic cancer is characterized by an extensive fibrotic stroma largely driven by activated pancreatic stellate cells (PSCs)/fibroblasts, which also function to support tumor growth and metastasis. Cholecystokinin-B receptors (CCK-BRs) are expressed on pancreatic stellate cells (PSCs) and have emerged as a key regulator of PSC activation and tumor-stromal interactions. We hypothesized that disrupting CCK-BR function shifts PSCs to a more quiescent phenotype and reduces their pro-fibrotic and tumor-supportive activity to decrease growth of pancreatic cancer. Murine PSCs were genetically engineered with CRISPR-Cas9 to knockout the CCK-BR. In a series of experiments, the role of the CCK-BR expression was evaluated on cell migration, proliferation, differentially expressed genes, molecular signaling pathways, and in co-culture with murine pancreatic cancer epithelial cells. Next, primary human pancreatic stellate cells were treated with proglumide, a CCK-BR antagonist, to study the effects of pharmacologic blockade of the CCK-BR on cellular signaling and proliferative pathways by RNA sequencing. Knockout of the CCK-BR led to significant decreases in PSC activation and the ability to stimulate growth of pancreatic cancer cells in co-culture. Both genetic knockdown and pharmacologic blockade of the CCK-BR downregulated genes implicated in fibrosis, proliferation, fibroblast activation, and tumorigenesis, while genes implicated in apoptosis and tumor suppression were upregulated. Flow cytometry showed increased apoptosis markers in CCK-BR-knockout cells compared to controls. These experiments combine transcriptomic profiling with functional validation to provide a comprehensive analysis of how targeting CCK-BR interrupts the cross-communication between cancer cells and fibroblasts. Blockade or downregulation of the CCK-BR on pancreatic fibroblasts may provide a strategy to disrupt oncogenic signaling pathways and reprogram the tumor microenvironment.