Oxymatrine induces cell cycle arrest and apoptosis and suppresses the invasion of human glioblastoma cells through the EGFR/PI3K/Akt/mTOR signaling pathway and STAT3

Oxymatrine (OM), a natural quinolizidine alkaloid extracted from the traditional Chinese herb Sophora flavescens, has been revealed to produce antitumor activities in various cancer cell lines, including glioblastoma lines, in vitro. However, the mechanisms by which OM exerts its antitumor effect against glioma are poorly understood. The aim of this study was to investigate the role of OM in the proliferation, apoptosis and invasion of glioma cells and to reveal the underlying mechanisms. The effects of OM on U251MG cells in vitro were determined using a Cell Counting Kit-8 (CCK-8) assay, flow cytometric analysis, Annexin V-FITC/PI staining, DAPI staining, a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay, a Transwell assay and western blotting. Our data indicated that OM inhibited proliferation, arrested the cell cycle at the G0/G1 phase, decreased the expression levels of G1 cell cycle regulatory proteins (cyclin D1, CDK4 and CDK6), inhibited invasion and induced apoptosis in glioma cells. Additional investigations revealed that the expression levels of p-STAT3 and key proteins in the EGFR/PI3K/Akt/mTOR signaling pathway, such as p-EGFR, p-Akt and p-mTOR, were markedly decreased after OM treatment, while the total STAT3, EGFR, Akt and mTOR levels were not affected. These findings indicated that the EGFR/PI3K/Akt/mTOR signaling pathway and STAT3 suppression may be a potential mechanism of the OM-mediated antitumor effect in glioblastoma cells and that EGFR may be a target of OM. Hence, OM may be a promising drug and may offer a novel therapeutic strategy for malignant gliomas in the future.