Indirubin-3-monooxime induced cell cycle arrest and apoptosis in Hep-2 human laryngeal carcinoma cells

The commercially available analogue of indirubin, indirubin-3-oxime, is known for its antitumor activities. To further establish its role in anticancer activity, we tested its potential against human laryngeal carcinoma cell line (Hep-2). We investigated the molecular mechanisms of indirubin-induced apoptosis and growth arrest in human laryngeal carcinoma cells. Upon treatment with indirubin-3-monooxime, a time dependent inhibition of cell growth was observed and cells developed many hallmark features of apoptosis. The increase of chromatin condensation after treatment with indirubin-3-oxime identified by staining with chromatin stain Hoechst 333258 indicates apoptosis. The observed increase in DNA fragmentation after indirubin-3-oxime in DNA gel electrophoresis indicates the apoptotic feature exhibited by the drug. Flow cytometric analysis confirmed that indirubin increased populations of apoptotic phase G1. Indirubin-3-oxime-induced growth inhibition was associated with induction of Cdk inhibitor p21, inhibition of cyclin D1 and activation of caspase-3. We conclude that indirubin-3-oxime induces cell death and apoptosis in human laryngeal carcinoma cells.