Kaempferol induces autophagic cell death of hepatocellular carcinoma cells via activating AMPK signaling

In the present study, we demonstrate that Kaempferol inhibited survival and proliferation of established human hepatocellular carcinoma (HCC) cell lines (HepG2, Huh-7, BEL7402, and SMMC) and primary human HCC cells. Kaempferol treatment in HCC cells induced profound AMP-activated protein kinase (AMPK) activation, which led to Ulk1 phosphorylation, mTOR complex 1 inhibition and cell autophagy. Autophagy induction was reflected by Beclin-1/autophagy gene 5 upregulation and p62 degradation as well as light chain 3B (LC3B)-I to LC3B-II conversion and LC3B puncta formation. Inhibition of AMPK, via AMPK alpha 1 shRNA or dominant negative mutation, reversed above signaling changes. AMPK inhibition also largely inhibited Kaempferol-induced cytotoxicity in HCC cells. Autophagy inhibition, by 3-methyaldenine or Beclin-1 shRNA, also protected HCC cells from Kaempferol. Kaempferol downregulated melanoma antigen 6, the AMPK ubiquitin ligase, causing AMPK alpha 1 stabilization and accumulation. We conclude that Kaempferol inhibits human HCC cells via activating AMPK signaling.