These data indicate that, first, a combination of a GPR55 agonist with a CB2 blocker could be an efficient anti-cancer drug combination, and second, that in the tumors positive for both GPR55 and CB2, a CB2 knockout or knockdown could lead to a potential switch of GPR55 from the pro-proliferative to the cytotoxic mode. Here, GPR55 is linked to cancer.