Reduced Chemosensitivity of FLT3/ITD Mutated Cells to Cytarabine and Quizartinib Under Hypoxic Conditions

• Published in: Blood 2016-12, Vol.128 (22), p.1579-1579
• Main Authors: Konig, Heiko, Rogozea, Adriana L, Kinnebrew, Garrett H, Ivan, Mircea
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V128.22.1579.1579

Background: FLT3/ITD mutated AML is characterized by short remission duration and high relapse rates due to the survival of a small fraction of leukemic cells (LCs) that outlive initial therapy. There is compelling evidence that the hypoxic niche in the bone marrow (BM) provides a sanctuary where subpopulations of LCs evade cytotoxic therapy and acquire drug resistance. In order to define the mechanisms involved in this process, multiple studies have focused on the interactions between LCs and the BM microenvironment but less is known about to the role of hypoxia as a modulator of drug resistance. Hence, the effects of standard and investigational therapies under hypoxic conditions are largely unknown. Here, we investigated the cytotoxic response of FLT3/ITD-mutated cells to conventional and targeted therapy under normoxic (21% O2) and hypoxic (1% O2) conditions. Methods: Molm14 (M14) cells and primary cells from relapsed/refractory FLT3/ITD mutated AML patients were incubated in culture medium under normoxic and hypoxic conditions. Cytarabine (Cy) or Quizartinib (Quiz) were added as single agents at the indicated concentrations. After 48 hours proliferation and apoptosis assays were performed using MTT assays, annexin V/PI staining and FACS analysis (M14). Cells were also assessed for FLT3 protein and Hypoxia inducible factor (HIF) target gene expression by western blotting and PCR arrays (RT2 ProfilerTM PCR Array, Human Hypoxia Signaling Pathway Plus, Qiagen) (M14 and primary cells), respectively. Results: We found that M14 cells were significantly less susceptible to treatment under hypoxic conditions, both when exposed to Cy and targeted FLT3 inhibition with Quiz (Growth inhibition, 0.25nM Quiz: 8.5±4.2% (1% O2) vs. 22±2.5% (21% O2), p