RNF43 and colorectal carcinoma: As such, small-molecule inhibitors of the membrane-bound O-acyltransferase Porcupine have been developed to block WNT signaling [67]; in RNF43-mutated small intestinal tumors, which lack the downstream WNT pathway regulation generally provided by RNF43, preclinical models have shown an effect in both CRC and SBA tumor growth suppression [68,69].