Several studies reported that the miR-155 is over-expressed in CLL [126,127,128] and its overexpression correlates with un-mutated immunoglobulin heavy variable (IGHV) genes status and high levels of ZAP-70 [126]; the involvement of miR-155 in promoting a B-cell disease was also underlined in mice models; indeed Eμ-miR-155 transgenic mice developed a high-grade B-cell malignancy [129]. The gene discussed is ZAP70; the disease is B-cell chronic lymphocytic leukemia.