Gambogic Acid Inhibits Melanoma through Regulation of miR-199a-3p/ZEB1 Signalling

Malignant melanoma is an aggressive form of cancer which is highly resistant to chemotherapy. We have previously found that gambogic acid (GA), a kind of polyprenylated xanthone, exhibits an antitumour role in melanoma. The study was designed to investigate novel mechanisms of the antitumour effect of GA in melanoma cells and implanted nude mice. Gambogic acid significantly decreased cell viability, increased apoptosis and reduced migration and invasion in A375 cells. In addition, cisplatin-induced cytotoxicity in both A375 and A375/CDDP cells was increased by GA. The expression of miR-199a-3p was increased by GA in A375 cells and implanted tumours, and inhibition of miR-199a-3p significantly prevented GA-induced effect on cell viability, apoptosis, migration, invasion and cisplatin sensitivity in A375 cells. miR-199a-3p mimics reduced tumour weight and volume in vivo and decreased cell viability, increased apoptosis and reduced migration and invasion in vitro. miR-199a-3p expression was decreased in melanoma tissues and cells, as compared with their controls. miR-199a-3p possessed a potential binding site in the 3′-UTR of zinc finger E-box binding homeobox (ZEB1). ZEB1 expression was increased in melanoma tissues and cells, as compared with their controls. ZEB1 and miR-199a-3p expression was negatively correlated in melanoma tissues. The expression of ZEB1 was decreased by GA in A375 cells and implanted tumours, and up-regulation of ZEB1 significantly prevented GA-induced effect on cell viability, apoptosis, migration, invasion and cisplatin sensitivity. Down-regulation of ZEB1 reduced tumour weight and volume in vivo and decreased cell viability, increased apoptosis and reduced migration and invasion in vitro. We identified the important roles of miR-199a-3p and ZEB1 in melanoma and elucidated the tumour suppressor function of miR-199a-3p through inhibition of ZEB1. The results highlight the importance of miR-199a-3p–ZEB1 signalling in antitumour effect of GA in malignant melanoma and provide novel targets for the chemotherapy of melanoma.