HTLV-1-positive (HuT-102) and HTLV-1-negative (Jurkat) CD4+ malignant T-cell lines were treated with TQ, dox, and combinations. Viability and cell cycle effects were determined by MTT assay and flow cytometry analysis, respectively. Combination effects on mitochondrial membrane potential and generation of ROS were assessed. Expression levels of key cell death proteins were investigated by Western blotting. A mouse xenograft model of ATLL in NOD/SCID was used for testing drug effects, and tumor tissues were stained for Ki67 and TUNEL. Here, CD4 is linked to adult T-cell leukemia/lymphoma.