In del[13q]CLL cells, the microRNA (miR) cluster miR-15a/miR-16-1 is deleted, leading to the loss of its tumor suppression function and overexpression of the antiapoptotic proteins B-cell lymphoma-2 (BCL-2) and myeloid cell leukemia-1 (MCL-1). The gene discussed is BCL2; the disease is B-cell chronic lymphocytic leukemia.