CNTN2 and adult T-cell leukemia/lymphoma: In the latter two cases, the malignant burden on these cells as well as the additional retroviral burden in MT4 cell-line, which is derived from one human T-lymphotropic virus type 1 (HTLV-1)-positive patient with adult T cell leukemia and expresses the HTLV-1 Tax protein, might enhance the HERV deregulation (21).