BCL2 and B-cell chronic lymphocytic leukemia: A driver event in the development of Chronic Lymphocytic Leukemia (CLL) is the deletion of the genomic region encoding for miR-15a/16-1. MicroRNAs are small non-coding RNAs involved in the regulation of gene expression, and loss of miR-15a/16-1 in CLL results in the accumulation of the antiapoptotic gene BCL2 and inhibition of the apoptotic process.