MCL1 and B-cell chronic lymphocytic leukemia: For instance, NOTCH1 and NOTCH2 signaling are constitutively activated in chronic lymphocytic leukemia (CLL) tumors, and inhibition of NOTCH1 and NOTCH2 has been found to enhance apoptosis in CLL cells, which is accompanied by downregulation of MCL1 and upregulation of IL4.