CNR1 and melanoma: Intriguingly, however, in a more recent study, CB1-silenced human A375 and 501 Mel melanoma cell lines exhibited reduced viability, colony-forming ability and cell migration, due to an arrest at G1/S phase, and suppressed expression of p-Akt and p-ERK1/2, which suggests that both (over)activation and complete loss of CB1 signaling may impair viability.