MCL1 and cancer: The altered expression levels of anti-apoptotic members of the Bcl-2 (B-cell lymphoma 2) protein family is a common feature in cancer.15 Most cancer cell models overexpress one or more of the three major proteins: Bcl-2, Bcl-xL (B-cell lymphoma-extra-large) and Mcl-1 (myeloid cell leukemia-1).