In the treatment of CCR4-positive ATLL, PTCL and CTCL, mogamulizumab works as a “molecular-targeted reagent” that directly kills malignant cells via ADCC: The target cells (CCR4-positive cells) of mogamulizumab must be abundant in the host, compared to the present study in which mogamulizumab was used for the treatment of advanced or recurrent solid (CCR4-negative) tumors as a “cancer immunotherapy reagent” that kills eTreg cells. Here, CCR4 is linked to adult T-cell leukemia/lymphoma.