We previously reported that the soft coral-derived bioactive substance, sinuleptolide, can inhibit the proliferation of oral cancer cells in association with oxidative stress. The functional role of oxidative stress in the cell-killing effect of sinuleptolide on oral cancer cells was not investigated as yet. To address this question, we introduced the reactive oxygen species (ROS) scavenger (N-acetylcysteine [NAC]) in a pretreatment to evaluate the sinuleptolide-induced changes to cell viability, morphology, intracellular ROS, mitochondrial superoxide, apoptosis, and DNA damage of oral cancer cells (Ca9-22). After sinuleptolide treatment, antiproliferation, apoptosis-like morphology, ROS/mitochondrial superoxide generation, annexin V-based apoptosis, and γH2AX-based DNA damage were induced. All these changes were blocked by NAC pretreatment at 4 mM for 1 h. This showed that the cell-killing mechanism of oral cancer cells of sinuleptolide is ROS dependent.
Keywords: N-acetylcysteine; oral cancer; oxidative stress; soft corals; γH2AX.