GPR55 and melanoma: In another study, 1–10 μM AM251 (48–72 h) induced apoptosis and G2/M cell cycle arrest in A375 human melanoma cells in a GPR55-, TRPA1-, and COX2-independent manner, whereas the combination of AM251 with COX2-inhibitor celecoxib produced a synergistic antitumor activity [396].