4-O-carboxymethyl ascochlorin induced autophagy through ER-stress in hepatocellular carcinoma cells

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NCI	MOLBIO-9

Authors

• JH Kang
• M Maurizi

Abstract

The synthetic derivative of ascochlorin, 4-O-carboxymethyl ascochlorin (AS-6), ameliorates type II diabetes in mice and also activates the nuclear hormone receptor, PPAR-γ. We performed a proteomic analysis of human hepatocellular carcinoma HepG2 cells to identify proteins that showed increased or decreased accumulation following treatment with AS-6. We found 58 differentially expressed proteins representing 55 unique protein species. AS-6 treatment led to increased levels of ER stress-related proteins including glucose-regulated protein 78 (BiP/GRP78), protein disulfide isomerase (PDI) and p97(VCP). Western blotting and immunostaining were used to validate the observed changes in expression of GRP78, PDI, p97 and several other proteins, and quantitative PCR confirmed that the observed changes in protein levels reflected up-regulation of transcription. Immunostaining of cells treated with AS-6 showed that the transcription factor CHOP, which mediates ER stress responses, accumulated within the nucleus. In addition, immunoblotting showed that the autophagic markers, LC3-II, beclin1, and ATG5, were increased in AS-6-treated cells. We propose that AS-6 exerts its cytotoxic effect via a mechanism initiated by ER stress followed by autophagy. Because it activates autophagic pathways, AS-6 is a promising lead for development of effective agents for tumor suppression.

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