However, only 20-30% of T-ALL cases are estimated to possess inactive Fbw7 [13], thus it is critical to understand how Fbw7-mediated Mcl-1 ubiquitination is physiologically regulated in vivo, and how Mcl-1 expression is aberrantly elevated in WT-Fbw7 genetic background, which accounts for 70-80% of T-ALL cases. This evidence concerns the gene MCL1 and acute lymphoblastic leukemia.