Along this line, interestingly, adult T-cell leukemia/lymphoma (ATLL) that developed in HTLV-1-infected T cells expresses high levels of IGSF4 on the cell surfaces, and IGSF4 expression may play a role in promoting cell-cell adhesion to the vascular endothelium, organ infiltration, and tumor growth in ATLL cells (37, 41). Here, CADM1 is linked to adult T-cell leukemia/lymphoma.