The effect of HPB242 on cell viability of oral cancer cells. (A) Chemical structure of HPB242. (B) The cell viability effect of HPB242 on HN22 and HSC4 cells. HN22 cells (2 × 103 cells/well) and HSC4 (3 × 103 cells/well) cells were seeded in 96-well plates and incubated for 24 hours and 48 hours with increasing concentrations of HPB242 in 10% FBS-DMEM. Cell viability was estimated using the trypan blue dye exclusion method, as described under Methods. Results are indicated as cell viability relative to the untreated HPB242, and data are represented as means ± SD from three independent experiments. The asterisk indicates a significant difference compared to the negative control (untreated cells) (*p < 0.05). (C) Morphological changes observed in the HPB242 treated (5, 10, and 20 μg/ml) or untreated HN22 and HSC4 cells 48 hours post-treatment.