Combined inhibition of integrin linked kinase and FMS-like tyrosine kinase 3 is cytotoxic to acute myeloid leukemia progenitor cells

ObjectiveDysregulation of signaling pathways leading to enhanced cell proliferation and resistance to apoptosis is frequent in acute myeloid leukemia (AML). The effectiveness of inhibiting two such pathways, the phosphatidylinosityl-3-kinase pathway via the intermediate integrin-linked kinase (ILK), and FMS-like tyrosine kinase–3 (FLT-3) signaling pathway in killing AML cells was studied.Materials and MethodsAML colony-forming cell (CFC) assays were used to determine the effects of a small molecule inhibitor of both ILK and FLT-3 (QLT0267) on poor prognosis primary AML sample viability. Kinase assays and Western blots were used to analyze effects of the compound on target molecules.ResultsIn 31/36 AML blast samples p-Akt was detected indicating phosphatidylinosityl-3-kinase activation. ILK was ubiquitously and FLT-3 abundantly expressed. Downregulation of ILK in the AML cell line TF-1 using small interfering RNA caused ≥50% CFC death, suggesting ILK inhibition might also be toxic to primary AML cells. In vitro kinase assays on three AML samples showed inhibition of both ILK and FLT-3 by QLT0267. Treatment of AML patient blast cells (n = 27) with QLT0267, caused a dose- and time-dependent downregulation of p-Akt and kill of AML-CFC with AML samples containing FLT-3 mutations being more sensitive to QLT0267 than those without. AML samples were more sensitive to QLT0267 killing than normal bone marrow (IC50 = 3 μM, vs 10 μM for AML-CFC and normal CFC, respectively, n = 5).ConclusionCombined inhibition of ILK and FLT-3 with a small molecule kinase inhibitor can achieve selective targeting of AML rather than normal hematopoietic progenitors.