Ginsenoside Rh2 inhibits proliferation but promotes apoptosis and autophagy by down-regulating microRNA-638 in human retinoblastoma cells.

Abstract

Even though recent therapeutic advances make retinoblastoma (RB) becomes a curable tumor, the outcome of long-term survival is poor due to the risk of developing secondary tumors. We aimed to explore the functional role of Ginsenoside Rh2 (GRh2) in human RB cells and the underlying mechanisms. Human RB Y79 and RBL-13 cells were incubated with or without GRh2, followed by assessments of cell viability, proliferation and apoptosis using Cell Counting Kit-8, bromodeoxyuridine, and flow cytometry assays. Meanwhile, expression levels of proteins associated with cell cycle, apoptosis, autophagy and the phosphatidylinositol-3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) pathway as well as p53 were measured by Western blot analysis. The mRNA expression of cyclinD1, autophagy-related gene 7 (ATG7) and p53, and microRNA (miR)-638 expression were analyzed using quantitative reverse transcription PCR. Then, miR-638 was overexpressed in Y79 and RBL-13 cells followed by treatment with GRh2, and p53 and proteins involved in the PI3K/AKT/mTOR pathway were assessed. Results showed that Y79 and RBL-13 cells viabilities were significantly reduced by 20-50\u202fμM GRh2. Cell proliferation was decreased, and cell apoptosis and autophagy were promoted by 30\u202fμM GRh2 in Y79 and RBL-13 cells. GRh2 decreased miR-638 expression, up-regulated p53 expression, and reduced phosphorylated levels of PI3K, AKT and mTOR. More experiments showed GRh2-induced alterations of p53, phospho (p)-PI3K, p-AKT and p-mTOR were all reversed by miR-638 overexpression. The observations demonstrated that GRh2 functioned in cell proliferation, apoptosis and autophagy in Y79 and RBL-13 cells through miR-638-mediated up-regulation of p53 and inactivation of the PI3K/AKT/mTOR pathway.