Leukemias with Suz12 loss are sensitive to inhibitors targeting the HDAC6/HSP90 axis. (A) Graph showing results of drug screen performed on JAK3(M511I)+Suz12gRNA (J+S1) vs JAK3(M511I) (J) leukemia cells ex vivo. A total of 181 drugs in screen are ranked according to J/J+S score. J/J+S score is defined as the ratio of the viability of the JAK3(M511I) leukemia cells (J) divided by the viability of the JAK3(M511I)+Suz12gRNA leukemia cells (J+S). (B) Heat map of a selection of 12 drugs from the screen showing differential sensitivity between J+S1 leukemia cells and J leukemia cells. The average viability of the 2 conditions was centered to 0. (C-E) Drug dose response curves showing viability of (leukemia) cells in response to 24 hours of treatment with increasing concentrations of HDAC6 inhibitor ricolinostat (C), HSP90 inhibitor 17-AAG (D), and HSP90 inhibitor PU-H71 (E). Percentage viability is defined as percentage surviving cells relative to DMSO concentration. GI50 values are shown. (F-H) Intracellular flow cytometry plots and quantifications of HSP90-PE MFIs with SEM after overnight (18 hours) treatment with Ricolinostat (RIC: 1, 2, or 5 μM) vs DMSO in J+S1 (F), S1 (G), and J (H) leukemia cells. (I) Survival curve showing DSS of J+S1 leukemic mice treated with RIC, 17-AAG, or placebo. The P values were calculated with Gehan-Breslow-Wilcoxon test. (J) WBC counts of J+S1 leukemic mice after 5 days of treatment. P values were calculated with 2-tailed unpaired Student t tests. (K) Weights of spleen and thymus at time of sacrifice of J+S1 leukemic mice treated with placebo vs RIC or 17-AAG. P values were calculated with 2-tailed unpaired Student t test.