Although further experiments are warranted in order to fully elucidate other factors apart from ZAP-70 involved in the regulation and functional role of miR-21 in CLL, these results help to enlighten the biology behind the adverse clinical outcome of patients with CLL having high expression of ZAP-70 and enhanced activation of the BCR signaling pathway. This evidence concerns the gene ZAP70 and B-cell chronic lymphocytic leukemia.