Effects of selective checkpoint kinase 1 inhibition on cytarabine cytotoxicity in acute myelogenous leukemia
Clinical Cancer Research, 08/08/2012
Schenk EL et al. – These results not only provide evidence for cytarabine-induced S phase checkpoint activation in AML in the clinical setting, but also show that a selective Chk1 inhibitor can overcome the S phase checkpoint and enhance the cytotoxicity of cytarabine.Methods
- AML marrow aspirates harvested before and during cytarabine infusion were examined by immunoblotting.
- Human AML lines treated with cytarabine in the absence or presence of SCH 900776 were assayed for checkpoint activation by immunoblotting, nucleotide incorporation into DNA and flow cytometry.
- Long-term effects in AML lines, clinical AML isolates, and normal myeloid progenitors were assayed using clonogenic assays.
- Immunoblotting demonstrated increased Chk1 phosphorylation, a marker of checkpoint activation, in over half of Chk1-containing AMLs after 48 h of cytarabine infusion.
- In human AML lines, SCH 900776 not only disrupted cytarabine-induced Chk1 activation and S phase arrest, but also markedly increased cytarabine-induced apoptosis.
- Clonogenic assays demonstrated that SCH 900776 enhanced the anti-proliferative effects of cytarabine in AML cell lines and clinical AML samples at concentrations that had negligible impact on normal myeloid progenitors.