Objective: Dysregulation 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 methods: AML 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.
Results: In 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 >or= 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 (IC(50)=3 microM, vs 10 microM for AML-CFC and normal CFC, respectively, n=5).
Conclusion: Combined inhibition of ILK and FLT-3 with a small molecule kinase inhibitor can achieve selective targeting of AML rather than normal hematopoietic progenitors.