Background
ABT‐737 is a BH3 mimetic small‐molecule inhibitor that binds with high affinity to Bcl‐2 to induce apoptosis in malignant cells and has shown promise as an effective anti‐leukemic agent in pediatric preclinical tests. This study focuses on the effects of ABT‐737 on leukemia cells with MLL rearrangement and identifies some of the biological correlates of its activity.
Procedure
Cells were cultured in the presence of increasing concentrations of ABT‐737 alone or in combination with other agents. After 4 days in culture, cell growth inhibition was measured by Alamar blue assay. The expression and activation of potential intracellular targets of ABT‐737 activity were determined by Western blot analysis.
Results
Significant Bcl‐2 expression was detected in all infant leukemia cells investigated. ABT‐737 induced cell death in all cell lines studied although the IC50 values differed somewhat between cell lines. Western blot analysis identified the effects of ABT‐737 on survival and apoptosis‐regulatory proteins PARP, caspase‐8, and cytochrome‐c. Drug combination studies indicated synergy with distinct anti‐neoplastic agents, including the multi‐tyrosine kinase inhibitor sunitinib. This effective drug synergy appears to be mediated by the combined inhibition of Bcl‐2 and intracellular signaling pathways.
Conclusions
We describe the in vitro studies to demonstrate the activity and drug combinability of ABT‐737 against MLL rearranged leukemia cells. In addition, identification of the molecular changes that occur in the presence of ABT‐737 provides information regarding effective target validation and target modulation analyses in future clinical trials. Pediatr Blood Cancer 2011;56:353–360. © 2010 Wiley‐Liss, Inc.