GPR55 and colorectal carcinoma: One explanation for this is that CP 55,940 has been found to act as an antagonist against GPR55, while WIN 55,212-2 has no appreciable activity at this receptor.30–32 The ability of CP 55,940 to antagonize GPR55 is consistent with our finding that CBD, but not THC, was able to reduce the viability of CRC cells.