The G protein-coupled P2Y6 receptor promotes colorectal cancer tumorigenesis by inhibiting apoptosis

Colorectal tumors are immersed in an array of tumor-promoting factors including extracellular nucleotides such as uridine 5'-diphosphate (UDP). UDP is the endogenous agonist of the G protein-coupled P2Y(6) receptor (P2Y(6)R), which may contribute to the formation of a tumor-promoting microenvironment by coordinating resistance to apoptosis. Colorectal cancer (CRC) was chemically induced in P2ry(6) knockout (P2ry(6)(-/-)) mice using azoxymethane and dextran sulfate sodium challenges. Mice were euthanatized and their tumor load determined. Fixed tissues were stained for histological and immunohistochemistry analysis. Tumoroids were also prepared from CRC tumors resected from P2ry6(+/+) mice to determine the role of P2Y(6)R in resistance to apoptosis, whereas HT29 carcinoma cells were used to elucidate the signaling mechanism involved in P2Y(6)R anti-apoptotic effect. P2ry(6)(-/-) mice developed a reduced number of colorectal tumors with apparent tumors having smaller volumes. Overall dysplastic score was significantly lower in P2ry(6)(-/-) animals. Stimulation of P2Y(6)R with the selective agonist MRS2693 protected HT-29 cells from TNF alpha-induced apoptosis. This protective effect was mediated by the stabilizing phosphorylation of the X-linked inhibitor of apoptosis protein (XIAP) by AKT. Using CRC-derived tumoroids, P2Y(6)R activation was found to contribute to chemoresistance since addition of the P2Y(6)R agonist MRS2693 significantly prevented the cytotoxic effect of 5-fluorouracil. The present study shows that sustained activation of P2Y(6)R may contribute to intestinal tumorigenesis by blocking the apoptotic process and by contributing to chemoresistance, a substantial concern in the treatment of patients with CRC. These results suggest that P2Y(6)R may represent a prime target for reducing colorectal carcinogenesis.