Hepatocellular carcinoma (HCC) is one of the most fatal malignancies with high mortality rate worldwide. In the present study, the underlying antitumor mechanism of gallotannin, a hydrolysable tannic acid, was elucidated in HepG2 and SKHep1 HCC cells. Gallotannin suppressed growth and colony formation and also induced senescence via upregulation of p21, G0 / G1 arrest and higher senescence-associated β-galactosidase (SA-β-gal) activity within 24 h culture in HepG2 and SKHep1 cells. Of note, gallotannin also induced autophagy by increasing the number of protein-cytosol-associated protein light chain 3 (LC3) punctae, LC3B-II conversion and SQSTM1/p62, autophagic vacuoles (AVOs) by transmission electron microscopy (TEM) and decreasing the of Beclin1 in HepG2 and SKHep1 cells. A tandem fluorescent-tagged LC3 reporter plasmid (GFP-mRFP-LC3) transfection revealed that gallotannin increased the number of yellow colored LC3 punctae through the co-localization of GFP and mRFP punctae and yellow colored LC3 punctae were increased by CQ or NH4Cl with accumulation of autophagosomes, LC3B-II and SQSTM1/p62 in HepG2 and SKHep1 cells. Additionally, gallotannin attenuated the of sirtuin1 (SIRT1) and mTOR and activated the phosphorylation of 5′-AMP activated protein kinase (AMPK) in two HCC cells. Furthermore, AMPK activator AICAR significantly enhanced SA-β-gal activity and antiproliferation induced by gallotannin, while AMPK inhibitor compound C did not in two HCC cells. Of note, gallotannin time dependently activated caspase 8 / 3 and time/concentration dependently increased sub G1 portion along with weak cleavages of PARP in two HCC cells. Collectively, gallotannin induces senescence and inhibits late autophagy flux, finally leading to apoptotic cell death in HepG2 and SKHep1 cells via inhibition of SIRT1 and activation of p-AMPK as a potent antitumor agent for HCC treatment.
Citation Format: Hee Young Kwon, Sung-hoon Kim. Gallotannin induces senescence and autophagy leading to cell death via SIRT1 inhibition and AMPK activation in hepatocellular carcinoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3545.