Abstract 3798: Epigallocatechin-3-gallate and atorvastatin induce translocation of eGFP-LC3 in immortalized baby mouse kidney cells suggesting of a link between autophagy and apoptosis

Abstract

Abstract Epigallocatechin-3-gallate (EGCG), the major polyphenolic compound in green tea, and atorvastatin (ATST), a commonly used cholesterol-lowing medication, have been reported to have cancer preventive activities and to induce cancer cell apoptosis. However, the mechanisms of these activities are still unclear. Here we report that EGCG and ATST could induce cell autophagy, which may be linked to the induction of cell apoptosis. In immortalized baby mouse kidney (iBMK) cells that overexpress eGFP-tagged LC3, EGCG at 3, 6 and 12 μM exhibited a dose-dependent induction of the translocation of eGFP-LC3, an indicator of the formation of autophagosomes, as observed by fluorescent microscopy. ATST at 2 and 4 μM also induced the translocation of eGFP-LC3. Western-blot analysis showed that 25 μM EGCG and 4 μM ATST treatment for 24 h induced the appearance of LC3-II, a higher migrating band, indicating the occurrence of autophagy. Beclin +/− iBMK cells also displayed autophagy upon treatment with 25 μM EGCG for 24h, but to a less extent as compared to Beclin +/+ cells. The induction of the appearance of eGFP-LC3 puncta could not be eliminated by addition of superoxide dismutase plus catalase, enzymes that were used to inhibit the auto-oxidation of EGCG and the production of reactive oxygen species. The results suggest that the induction of autophagy is not caused by EGCG auto-oxidation produced oxidative stress. ATST inhibited the proliferation of iBMK cells in 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, but the inhibition was to a less extent in Beclin +/− cells as compared to Beclin +/+ cells. EGCG and ATST treatment resulted in an increase of cleaved caspase 3, a hallmark of cell apoptosis, and a decrease of anti-apoptotic Bcl-2. Beclin +/+ iBMK cells showed stronger and earlier induction of these apoptotic markers than Beclin +/− cells, indicating that induction of apoptotic marker is correlated to the ability of cells to produce autophagy. EGCG at 25 μM and ATST at 2 μM also induced the appearance of endogenous LC3-II in human colon cancer HCT116 cells. The induction of autophagy may be a key mechanism for EGCG and ATST to inhibit cancer growth and formation (This research is supported by NIH grants CA 120915 and CA 133021). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3798.