Figure 4

Three safe‐in‐human HDAC inhibitors induce mTORC1‐dependent selective cytotoxicity exclusively in hydrogel culture. A,D) Dose–response cytotoxicity curves of H9 (panel A) and H7 (panel D) cells treated with the indicated HDAC inhibitor for 3 days while cultured on plastic or hydrogel ± 20 × 10⁻⁹m rapamycin. Data fit via four‐parameter logistic regression (mean ± SD; n = 3). B,E) Confidence intervals of HDAC inhibitor maximal toxicity, estimated by four‐parameter logistic regression models generated in panels (A) and (D). C,F) Percentage of SyTOX⁺ cells following temporal HDAC inhibitor treatment (20 × 10⁻⁶m SAHA, 5 × 10⁻⁶m SB939, 1 × 10⁻⁶m LBH589) of H9 (panel C) and H7 (panel F) cells cultured in hydrogel ± 20 × 10⁻⁹m rapamycin (mean ± SD; * = p < 0.05 by two‐factor ANOVA with Bonferroni post hoc comparisons; n = 3). G) Percentage of cells expressing cleaved caspase 3 (CASP3), following 3 day treatment with HDAC inhibitors in hydrogel (20 × 10⁻⁶m SAHA, 5 × 10⁻⁶m SB939, and 1 × 10⁻⁶m LHB589, mean ± SD; * = p < 0.05 by two‐way ANOVA with Dunnett post hoc comparisons to 0 h for each group; n = 5–6). H) Percentage of SyTOX⁺ cells following 3 day HDAC inhibitor treatment (20 × 10⁻⁶m SAHA, 5 × 10⁻⁶m SB939, and 1 × 10⁻⁶m LHB589) in hydrogel ± 25 × 10⁻⁶m Z‐VAD (OMe)‐FMK (mean ± SD; * = p < 0.05 by one‐way ANOVA with Bonferroni post hoc comparisons; n = 4–6).