Saikosaponin D regulates apoptosis and autophagy of pancreatic cancer Panc-1 cells via Akt/mTOR pathway

Abstract

This study aims to investigate the effect and mechanism of saikosaponin D on the proliferation, apoptosis, and autophagy of pancreatic cancer Panc-1 cells. The cell counting kit(CCK-8) was used to examine the effects of 7, 10, 13, 16, 19, 22, 25, and 28 μmol·L~(-1) saikosaponin D on the proliferation of Panc-1 cells. Three groups including the control(0 μmol·L~(-1)), low-concentration(10 μmol·L~(-1)) saikosaponin D, and high-concentration(16 μmol·L~(-1)) saikosaponin D groups were designed. The colony formation assay was employed to measure the effect of saikosaponin D on the colony formation rate of Panc-1 cells. The cells treated with saikosaponin D were stained with hematoxylin-eosin(HE), and the changes of cell morphology were observed. Hoechst 33258 fluorescent staining was used to detect the effect of saikosaponin D on the cell apoptosis. The autophagy staining assay kit with MDC was used to examine the effect of saikosaponin D on the autophagy of Panc-1 cells. Western blot and immunocytochemistry(ICC) were employed to examine the effect of saikosaponin D on the expression levels and distribution of B-cell lymphoma-2(Bcl-2), Bcl-2-associated X protein(Bax), cysteine-aspartic acid protease-3(caspase-3), cleaved caspase-3, autophagy-associated protein Beclin1, microtubule-associated protein light chain 3(LC3), protein kinase B(Akt), phosphorylated protein kinase B(p-Akt), mammalian target of rapamycin(mTOR), and phosphorylated mammalian target of rapamycin(p-mTOR). The results showed that compared with the control group, saikosaponin D decreased the proliferation rate of Panc-1 cells in a dose-dependent and time-dependent manner. The colony formation rate of the cells significantly decreased after saikosaponin D treatment. Compared with the control group, the cells treated with saikosaponin D became small, accompanied by the formation of apoptotic bodies. The saikosaponin D groups showed increased apoptosis rate and autophagic vesicle accumulation. Compared with the control group, saikosaponin D up-regulated the expression of Bax, cleaved caspase3, Beclin1, LC3Ⅱ/LC3Ⅰ and down-regulated the expression of Bcl-2, caspase-3, p-Akt/Akt, and p-mTOR/mTOR. In addition, these proteins mainly existed in the cytoplasm. In conclusion, saikosaponin D can inhibit the proliferation and induce the apoptosis and autophagy of Panc-1 cells via inhibiting the Akt/mTOR pathway.