CNR1 and melanoma: However, treatment of the CB2 and (interestingly, mostly intracellular) CB1 expressing COLO38 (a melanoma-associated proteoglycan [MPG] antigen positive human melanoma cell line) and OCM-1 (non-metastatic human ocular choroidal melanoma cells) melanoma cells with WIN55,212-2 (2–5 μM) reduced viability in a CB1/CB2-independent manner, and induced phosphorylation of the ERK1/2 MAPK cascade (5 μM; 24 h).