Arsenic trioxide induces G2/M arrest in hepatocellular carcinoma cells by increasing the tumor suppressor PTEN expression

Abstract

Arsenic trioxide (As(2)O(3)), an effective agent against acute promyelocytic leukemia, has been reported to inhibit the viability of solid tumors cell lines recently. The detailed molecular mechanism underlying the As(2)O(3)-induced inactivation of the cdc2 and possible functional role of PTEN in the observed G2/M arrest has yet to be elucidated. Here, we assessed the role of PTEN in regulation of As(2)O(3)-mediated G2/M cell cycle arrest in Hepatocellular carcinoma cell lines (HepG2 and SMMC7721). After 24 h following treatment, As(2)O(3) induced a concentration-dependent accumulation of cells in the G2/M phase of the cell cycle. The sustained G2/M arrest by As(2)O(3) is associated with decreased cdc2 protein and increased phospho-cdc2(Tyr15). As(2)O(3) treatment increased Wee1 levels and decreased phospho-Wee1(642). Moreover, As(2)O(3) substantially decreased the Ser473 and Thr308 phosphorylation of Akt and upregulated PTEN expression. Downregulation of PTEN by siRNA in As(2)O(3) -treated cells increased phospho-Wee1(Ser642) while decreased phospho-cdc2(Tyr15), resulting in decreased the G2/M cell cycle arrest. Therefore, induction of G2/M cell cycle arrest by As(2)O(3) involved upregulation of PTEN.