Benzyl isothiocyanate promotes apoptosis of oral cancer cells via an acute redox stress-mediated DNA damage response

Abstract

Benzyl isothiocyanate (BITC) is a cruciferous vegetable-derived compound with anticancer properties in human cancer cells. However, its anticancer potential and underlying mechanisms remain absent in human oral cancer cells. Results indicate that BITC inhibits growth, promotes G₂/M phase arrest and triggers apoptosis of OC2 cells with a minimal toxicity to normal cells. BITC-induced cell death was completely prevented by pretreatment with thiol-containing redox compounds including N-acetyl-l-cysteine (NAC), glutathione (GSH), dithiothreitol, and 2-mercaptoethanol, but not free radical scavengers mito-TEMPO, catalase, apocynin, l-NAME and mannitol. BITC rapidly produced reactive oxygen species and nitric oxide, triggered oxidative DNA damage. BITC effectively decreased the intracellular GSH and GSH/GSSG ratio and redox balance recovery by thiol-containing redox compounds, but not by free radical scavengers. Accordingly, redox stresses-DNA damage response (DDR) activated ATM, Chk2, p53, and p21 and subsequently resulted in G₂/M phase arrest by inhibiting Cdc2 and cyclin B1. Notably, BITC-induced apoptosis was associated with reduced Mcl-1 and Bcl-2 expression, diminished mitochondrial membrane potential (ΔΨm), and increased PARP cleavage. These BITC-induced redox stress-mediated DDR and apoptosis could be blocked by NAC and GSH. Therefore, BITC can be a rational drug candidate for oral cancer and acted via a redox-dependent pathway.

Keywords: Apoptosis; Benzyl isothiocyanate; DNA damage; Oral squamous cell carcinoma; Redox stress.