PTC299 and decitabine synergize on primary MDS cells. (A) MTS assays showing the viability of primary MDS cells treated with the indicated doses of PTC299 and/or DAC relative to the untreated control. CD34⁺ MDS cells were cultured in the presence of SCF, TPO, IL-3, GM-CSF, and FLT3 ligand. Cell growth was examined by MTS assays at 48 to 72 hours in culture. Each diagnosis was shown at the right of patient ID. MDS EB-1, MDS with excess blasts-1; MDS EB-2, MDS with excess blasts-2. (B) MTS assays showing the viability of primary MDS cells derived from ID-4 patient treated with the indicated doses of PTC299 in combination with the indicated doses of DAC relative to the untreated control (left). Combination indexes (CI) are in the right panel. (C) Colony formation by CD34⁺ MDS and normal BM cells treated with PTC299 and/or DAC in methylcellulose. The number of colonies were counted at day 10 of culture. (D) Colony formation by CD34⁺ MDS BM cells treated with PTC299 in methylcellulose. The number of colonies were counted at day 10 of culture (left). Quantitative RT-PCR analysis of c-MYC in MDS cells treated with 10 nM PTC299 for 48 hours. GAPHD was used to normalize the amount of input RNA. Data are shown as the mean ± SD. *P < .05, **P < .01, ***P < .001; ns, not significant by 1-way ANOVA.