In contrast to HTLV-1, which is also transmitted from simians to humans and leads to adult T-cell leukemia/lymphoma (ATLL), the transactivator Tax was reported to protect cells from apoptosis by regulating mitochondrial apoptosis pathway-associated cytokines expression, such as Bcl-2, Bcl-XL [43–45] and Bak, Bax [46]. Here, BCL2L1 is linked to adult T-cell leukemia/lymphoma.