Sulforaphane inhibits histone deacetylase causing cell cycle arrest and apoptosis in oral squamous carcinoma cells.

ABSTRACT

Background: Biologic compounds have recently generated interest in cancer chemoprevention. Sulforaphane (SFN), an isothiocyanate from cruciferous vegetables, has profound epigenetic actions. Since epigenetic aetiology is crucial for oral cancer, this study evaluated the role of SFN in oral cancer prevention. Methods: Oral squamous cell carcinoma cells (UPCI-SCC-172) were treated with SFN in three concentrations 10 µM, 20 µM and 30 µM for two time periods 24 h and 48 h. MTT assay assessed cell proliferation. Histone deacetylase (HDAC) enzyme activity was colorimetrically estimated in the nuclear extracts. Flow cytometry determined cell cycle stages, reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP) changes. Extrinsic and intrinsic apoptotic pathways were evaluated from caspase enzyme assays. Results: Cell proliferation and HDAC activity (44% in 24 h and 40% in 48 h) were significantly inhibited (p < 0.01). For 10 µM concentration, G2/M cell cycle arrest was found with a reduction in G1 phase cell population at 24 h and 48 h. Concentrations of 20 µM and 30 µM SFN presented cells in apoptosis marked by increased sub G1 cells at 48 h. Concentrations of 10 µM and 20 µM SFN showed a 1.3 to 2.8-fold increase in ROS generation at 24 h and 48 h. The concentration of 30 µM SFN showed a drop in ROS production, denoting cells already in apoptosis. Fall in MMP was also dose- and time-dependent. Caspase enzyme assays (p < 0.001) demonstrated activation of both extrinsic and intrinsic apoptotic pathways. Conclusion: Inhibitory action of SFN on oral cancer cell proliferation and HDAC activity led to cell cycle arrest and apoptosis. These effects marked by increase in ROS, a decrease in MMP and activation of apoptotic pathways offer exciting therapeutic options.