BCL2 and hematologic disorder: The protein product of the larger mRNA, Bcl-xl, was similar in size and predicted structure to Bcl-2.31 Similar to Bcl-2 and Mcl-1, elevated Bcl-xl expression has been frequently observed in hematologic malignancies and is implicated to have a role in disease progression.32bcl-x−/− mice died at embryonic day 13 and displayed massive cell death of immature hematopoietic cells and thus severe defects in the development of the hematopoietic system,33 underlining the essential role of Bcl-x for the survival and development of lymphoid cells.