Abstract 990: Saxifragifolin D induces autophagy via activating IRE1α/ JNK pathway in breast cancer cells

Abstract

Abstract Background and Objective: Saxifragifolin D (SD) was isolated from Androsace umbellata by our group. It has been reported to inhibit some types of cancer cells, such as Hep3B, HepG2, SK-OV-3, A549, HCT-115 and multidrug resistante cell line HepG2/ADM. However, the growth inhibitory effect of SD on breast cancer cells and the mechanisms is still unclear. In this study, we explored the underlying molecular mechanisms of SD-induced autophagy in breast cancer cells. Methods and Results: The autophagosomes, double membrane vacuolar structures, were observed in SD-treated MCF-7 and MDA-MB-231 cells by transmission electronic microscopy. And the autophagic vacuoles labeled by MDC were also increased in a time-dependent manner significantly. Besides, the autophagic ratio, quantified by using Cyto-ID® detection kit, was enhanced in a dose-dependent manner in these two cells. What's more, the marker of autophagy, LC3, was activated in MCF-7 and MDA-MB-231 cells treated with SD showed by western blot assay, further confirmed autophagy induced by SD. We also found that IRE1α which associated with endoplasmic reticulum (ER) stress was activated, and the JNK and Bcl-2 were phosphorylated in SD-treated MCF-7 and MDA-MB-231 cells by western blot assay. Accordingly, the up-regulation of Beclin1, Vps34, Atg5 and Atg16L were also detected in these two cells. Furthermore, suppression of autophagy by pretreating with Beclin1 siRNA or bafilomycin A1 decreased apoptosis and cell death, and resulted in decreases in expression of LC3- II and cleaved PARP. It's worth noting that inhibition of ER stress by IRE1α siRNA or TUDCA suppress autophagy and apoptosis, and the down-expression of LC3- II and cleaved PARP were measured. Conclusion: SD induces autophagy associated with IRE1α/ JNK pathway in breast cancer cells and these findings will provide molecular bases for molecular mechanistic studies of SD-treated breast cancer cells. Key words: Saxifragifolin D, autophagy, breast cancer. Citation Format: Liang-Liang Bai, Jun-Min Shi, Min-Feng Chen, Dong-Mei Zhang, Ying Wang, Wen-Cai Ye. Saxifragifolin D induces autophagy via activating IRE1α/ JNK pathway in breast cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 990. doi:10.1158/1538-7445.AM2015-990