Among them, MEC1/MEC2, PCL12, and HG3 are the most frequently used; they express a clonotypic BcR bearing either mutated (MEC1 and MEC2) or unmutated (PCL12 and HG3) IGHV genes, thus representing the two different subgroups of CLL cases. This evidence concerns the gene ATR and B-cell chronic lymphocytic leukemia.