Previously, we reported that mice with the combination of upregulated BCL2 and deficient TRAF2 signaling in B cells develop small B cell lymphoma (SBL)/CLL with high incidence, while neither deficient TRAF2 function nor BCL2 upregulation alone were sufficient to induce CLL or other malignancies in mice (31, 32). Here, BCL2 is linked to B-cell chronic lymphocytic leukemia.