EGCG and ECG induce apoptosis and decrease autophagy via the AMPK/mTOR and PI3K/AKT/mTOR pathway in human melanoma cells

Catechins have been proven to exert antitumor effects in different kinds of cancers. However, the underlying mechanisms have not been completely clarified yet. This study aimed to assess the effects and mechanisms of (-)-epigallocatechin-3-gallate (EGCG) and (-)-epicatechin-3-gallate (ECG) on human melanoma skin A375 cells. Results showed that EGCG and ECG inhibited the proliferation of A375 cells and ECG showed better inhibitory effect. Flow cytometry analysis had shown that EGCG and ECG induced apoptosis and led to cell cycle arrest. EGCG and ECG decreased Bcl-2 expression and upregulated Caspase-3 protein level, indicating the development of apoptosis. Furthermore, EGCG and ECG could decreased mitochondrial membrane potential of A375 cells. In addition, the expression of Beclin-1, LC3 and Sirt3 were downregulated at protein levels, which known to be associated with autophagy. After autophagy was increased by rapamycin, the apoptotic trend was not change, indicating that apoptosis and autophagy are independent. Mechanistically, EGCG and ECG treatments decreased phosphorylated-AMPK (p-AMPK) and increased the ratios of p-PI3K, p-AKT and p-mTOR in melanoma cells. Conclusively, EGCG and ECG induced apoptosis via mitochondrial signaling pathway, downregulated autophagy through modulating the AMPK/mTOR and PI3K/AKT/mTOR signaling pathway. It indicated that EGCG and ECG may be utilized in human melanoma treatment.