BCL2 Inhibitor (ABT-737): A Restorer of Prednisolone Sensitivity in Early T-Cell Precursor-Acute Lymphoblastic Leukemia with High MEF2C Expression?

Early T-cell precursor-acute lymphoblastic leukemia (ETP-ALL) has been identified as a high-risk subtype of pediatric T-cell acute lymphoblastic leukemia (T-ALL). Conventional chemotherapy is not fully effective for this subtype of leukemia; therefore, potential therapeutic targets need to be explored. Analysis of the gene expression patterns of the transcription factors in pediatric T-ALL revealed that MEF2C and FLT3 were expressed at higher levels in ETP-ALL than typical T-ALL. Using human T-ALL and BaF3 cell lines with high expression levels of MEF2C, the present study tested whether the BCL2 inhibitor (ABT-737) restores the sensitivity to prednisolone (PSL), because MEF2C causes PSL resistance, possibly by augmenting the anti-apoptotic activity of BCL2. Treatment with PSL and ABT-737 caused a significant reduction in the IC50 of PSL in the MEF2C-expressing LOUCY cells, in addition to the MEF2C-transduced BaF3 cells, but not in the non-MEF2C-expressing Jurkat cells. The combination treatment significantly accelerated the killing of primary leukemic blast cells of ETP-ALL with high expression levels of MEF2C, which were co-cultured with murine stromal cells. These findings suggest that BCL2 inhibitors may be a therapeutic candidate in vivo for patients with ETP-ALL with high expression levels of MEF2C.