For example, in multiple studies, increased levels of Bcl-2, Bcl-xL, and Mcl-1 proteins were linked to survival of multiple myeloma cells and resistance to chemotherapy (Oancea et al., 2004), while in most cases of chronic lymphocytic leukemia (CLL), elevated Bcl-2 mRNA and protein levels are noted (Tsujimoto et al., 1984). This evidence concerns the gene BCL2 and B-cell chronic lymphocytic leukemia.