Cell viabilities of oral cancer cells after manoalide treatment and its N-acetylcysteine (NAC)/apoptosis inhibitor Z-VAD-FMK (Z-VAD) effects. Cells were treated with 0, 5, 10, and 20 μM of manoalide. All treatments have the same concentration of DMSO. (A) MTS assay-based cell viabilities for 24 h. Oral cancer (CAL 27, Ca9-22, OECM-1, OC-2, HSC 3, and SCC9) cells and oral normal (HGF-1) cells were included. (B) MTS assay-based cell viabilities for 48 and 72 h for oral cancer (CAL 27 and Ca9-22) and oral normal (HGF-1) cells. (C) Statistical of 3D spheroid formation for manoalide-treated oral cancer (Ca9-22 and CAL 27) cells for 72 h. (D) NAC and Z-VAD effects on MTS viability of manoalide-treated oral cancer cells. Pretreatment conditions were 8 mM, 1 h for NAC and 100 μM, 2 h for Z-VAD. Following pretreatment or not, oral cancer (Ca9-22 and CAL 27) cells were post-incubated with 5 and 10 μM manoalide for 24 h. Data, means ± SDs (n = 3). Data were analyzed by one-way ANOVA with Tukey HSD Post Hoc Test. Data showing the same small lettersrepresent nonsignificant differences whereas data showing no overlapping same small letters are significant difference (p < 0.05–0.001).