EGCG-induced selective death of cancer cells through autophagy-dependent regulation of the p62-mediated antioxidant survival pathway
Ho Woon Lee, Jee‐Hye Choi, Dongbeom Seo, Gavaachimed Lkhagvasuren, Jaesung Choi, Sehwan Park, Na Young Min, Dong Ho Lee, Hyoweon Bang, Seung Wook Ham, Jung-Woong Kim, Sung Chul Lee, Sangmyung Rhee, Sang‐Beom Seo, Kwang-Ho Lee
Abstract
The effects of EGCG on the selective death of cancer cells by modulating antioxidant pathways through autophagy were explored in various normal and cancer cells. EGCG positively regulated the p62-KEAP1-NRF2-HO-1 pathway in normal cells, while negatively regulating it in cancer cells, leading to selective apoptotic death of cancer cells. In EGCG-treated MRC5 cells (EGCG-MRC5), autophagic flux was blocked, which was accompanied by the formation of p62-positive aggregates. However, EGCG-treated HeLa cells (EGCG-HeLa) showed incomplete autophagic flux and no aggregate formation. The levels of P-ULK1 S556 and S758 increased in EGCG-MRC5 through AMPK-mTOR cooperative interaction. In contrast, EGCG treatment in HeLa cells led to AMPK-induced mTOR inactivation, resulting in abrogation of P-ULK1 S556 and S758 levels. AMPK knockout in EGCG-HeLa restored positive regulation of the p62-mediated pathway, which was accompanied by increased P-mTOR S2448 and P-ULK1 S758 levels. Knockdown of 67LR in EGCG-HeLa abolished AMPK activity but did not restore the p62-mediated pathway. Surprisingly, both AMPK knockout and 67LR knockdown in EGCG-HeLa markedly increased cell viability, despite differential regulation of the antioxidant enzyme HO-1. In conclusion, EGCG induces the selective death of cancer cells through the modulation of at least two autophagy-dependent and independent regulatory pathways: negative regulation involves the mTOR-ULK1 (S556 and S758)-p62-KEAP1-NRF2-HO-1 axis via AMPK activation, whereas positive regulation occurs through the 67LR-AMPK axis. • EGCG-induced selective death of cancer cells is achieved by regulation of the p62-KEAP1-NRF2-HO-1 antioxidant pathway. • The p62-mediated antioxidant pathway is regulated along with the formation of p62-positive aggregates. • The blockade or activation of autophagy is involved in the differential activation of ULK1 via regulation of mTOR and AMPK. • EGCG-induced apoptotic cell death can also be induced by the 67LR via AMPK activation, independently of the p62 pathway.