GRK5 and malignant colon neoplasm: Because PGE2 stimulates TOPFLASH and CREB reporter activities through the PGE2 receptor subtype 2, EP2, in DLD-1 colon cancer cells [19], the effects of GRK5 expression on PGE2-stimulated TOPFLASH and CREB reporter activities in EP2-transfected HCT116 cells were analyzed.