TKi enhanced the effect of POLθI against OTK-positive hematological malignancies. (A-C) Lin^-CD34⁺ cells from FLT3(ITD)-positive AMLs (n = 3), JAK2(V617F)-positive MPN (n = 1), BCR-ABL1–positive CML-CPs (n = 3) and normal healthy donors (n = 3), and (D) mononuclear cells from Ph+ ALL (n = 3) and normal healthy donors (n = 3) were incubated with OTK-specific TKi (panel A, 10 nM FLT3 kinase inhibitor quizartinib; panel B, 25 nM JAK1/2 kinase inhibitor ruxolitinib; panels C,D, 1 μM ABL1 kinase inhibitor imatinib) and/or POLθi (25 μM ART558). Results represent the mean percentage of colonies ± SD compared with untreated controls (A,C), mean number of colonies ± SD (B), and mean percentage of living cells ± SD compared with untreated controls (D) ∗P < .05 when compared with individual treatments using two-tailed unpaired t test. (E) PLX treatment experimental diagram. (F) Sensitivity of Lin^-CD34⁺ PLX patient cells to the indicated inhibitors. Results represent the mean percentage of colonies ± SD compared with untreated controls. ^∗P < .05 when compared with individual treatments using response additivity approach. (G) Mean number of hCD45⁺ AML cells ± SD in peripheral blood lymphocyte of PLX-bearing NRGS mice untreated (C) and treated with treated with quizartinib (Q), NVB (N), and the combination (Q + N). ∗P < .05 when compared with individual treatments using two-tailed unpaired t test. (H) Survival curves and MST of the mice. ∗P < .001 in comparison to quizartinib and NVB using Kaplan-Meier log-rank test. MST, median survival time; SD, standard deviation.