MCL1 and B-cell chronic lymphocytic leukemia: Hussain et al[56] conducted a study in 2007 and demonstrated that siRNA-mediated MCL-1 knockdown resulted in mitochondrial membrane depolarization and apoptosis in ALL cell lines and tumor cells from chronic lymphocytic leukemia (CLL) patients; furthermore, MCL-1 down-regulation led to enhanced sensitivity to rituximab-mediated killing by complement-dependent cytotoxicity and direct apoptosis.