SCOR in Targeted Therapies for Infant Leukemias Project 2: Targeting Apoptosis in Leukemia in Infants

OBJECTIVES:

• Determine comprehensive gene and protein expression profiles of in vitro sensitivity and resistance to obatoclax mesylate in multiple-lineage leukemia (MLL)-rearranged cell lines and primary infant acute myeloid leukemia (AML) samples.
• Define optimum in vitro combinations of obatoclax mesylate targeting pro-survival BCL-2 family proteins with cytotoxic drugs in MLL-rearranged leukemia cell lines and primary infant AML samples.
• Identify synergistic combinations based on a pharmacodynamic modeling and simulation construct.
• Determine whether combinations of obatoclax mesylate targeting pro-survival BCL-2 family proteins with cytotoxic drugs improves survival in a xenograft model of MLL-rearranged infant AML.

OUTLINE: This is a multicenter study.

Obatoclax mesylate activity is assessed via the MTT assay. A priori features of acute myeloid leukemia (AML) blasts relating to the apoptosis and ATG cell death pathways and their execution are characterized using microarray analysis and quantitative real-time (Q-RT) PCR. Gene and protein expression is described and quantified using Q-RT PCR and western blot analysis at specific time points after obatoclax mesylate exposure to identify pharmacodynamic biomarkers of activity and characterize the cell death mechanism in multiple-lineage leukemia (MLL)+ AML. The MTT assay is performed using obatoclax mesylate-cytotoxic chemotherapy combinations to determine synergy focusing on common cytotoxic drugs employed in AML treatment regimens.

Obatoclax mesylate efficacy is tested in a therapeutic NOG xenograft model of primary MLL+ infant AML.