Emodin-8-O-β-D-glucopyranoside, a natural hydroxyanthraquinone glycoside from plant, suppresses cancer cell proliferation via p21-CDKs-Rb axis

Emodin-8-O-β-D-glucopyranoside (EG), a natural hydroxyanthraquinone glycoside from some traditional medicinal plants, has been demonstrated to have potential antitumor effects in our previous studies. Herein, we confirm that EG remains stable in the cell culture medium. It suppresses cell viability and proliferation and induces G1 cell cycle arrest in human colorectal cancer and neuroblastoma cells in vitro. EG inhibits tumor growth in human colorectal cancer cell HCT 116-bearing xenograft mice with low toxicity in the liver and kidney. The transcriptome analysis shows that the p53 signaling pathway is the most enriched cellular pathway and EG affects the proliferation of HCT 116 cells through modulating cell cycle related genes, such as CDKN1A and Cyclin-dependent kinases (CDKs). We demonstrate that the protein expression level of p21 was up-regulated, and CDK1/CDK2 were reduced significantly in both HCT 116 and SH-SY5Y cells after EG treatment. The switch from hypo- to hyper-phosphorylated Retinoblastoma (Rb), which is believed as a result of activated CDKs, was inhibited when cells were treated with EG. These findings indicate that EG suppresses cancer cell proliferation via p21-CDKs-Rb axis.