MCL1 and Burkitt lymphoma: In order to analyze the effect of the cell-permeable Bak BH3 peptide on the viability of cell lines obtained from hematologic malignancies, Ramos cells from Burkitt's lymphoma, an aggressive human B non-Hodgkin's lymphoma expressing the Bax, Bak, Bcl-XL, and Mcl-1 proteins but not Bcl-2 (Figure 1(b)) and CCRF-CEM cells originating from human T-cell acute lymphoblastic leukemia and expressing Bax, Bak, and Bcl-XL and slightly expressing Bcl-2 and Mcl-1 also (Figure 1(b)), were treated with 20 μM of the different peptides and controls.