Previously, we investigated the transcriptional control of CCR4 expression in ATLL and have found that an activating protein 1 (AP1) family member, FBJ murine osteosarcoma viral oncogene homolog (FOS)-related antigen 2 (FRA2), is consistently expressed at high levels in ATLL and, together with v-JUN avian sarcoma virus 17 oncogene homolog D (JUND), up-regulates the expression of CCR4 as well as that of several proto-oncogenes such as v-MYB myeloblastosis viral oncogene homolog (MYB), murine double minute 2 homolog (MDM2), and B-cell lymphoma 6 (BCL6).