Inhibition of STAT3 signalling contributes to the antimelanoma action of atractylenolide II

Our previous studies showed that atractylenolide II (AT-II) has antimelanoma effects in B16 melanoma cells. In this study, we investigated the involvement of STAT3 signalling in the antimelanoma action of AT-II. Daily administration of AT-II (12.5, 25 mg/kg, i.g.) for 14 days significantly inhibited tumor growth in a B16 xenograft mouse model and inhibited the activation/phosphorylation of STAT3 and Src in the xenografts. In B16 and A375 cells, AT-II (20, 40 μm) treatment for 48 h dose-dependently reduced protein expression levels of phospho-STAT3, phospho-Src, as well as STAT3-regulated Mcl-1 and Bcl-xL. Overexpression of a constitutively active variant of STAT3, STAT3C in A375 cells diminished the antiproliferative and apoptotic effects of AT-II. These data suggest that inhibition of STAT3 signalling contributes to the antimelanoma action of AT-II. Our findings shed new light on the mechanism of action underlying the antimelanoma effects of AT-II and provide further pharmacological basis for developing AT-II as a novel melanoma chemopreventive/chemotherapeutic agent.