CCR8 and adult T-cell leukemia/lymphoma: To further investigate whether anti-CCR8 CAR T cells suppress ATLL cell growth in vitro, we performed a cytotoxicity assay with C1028z and C1928z and 1928z T cells in two ATLL cell lines that did not express CD19 (Figure S4A), and showed that C1028z and C1928z T cells exhibited higher cytotoxicity than 1928z T cells after coculture with MT-4-GFP-2A-Luciferase (GL) and C8166-GL cells at the indicated effector:target (E:T) ratio in vitro (Figures 3A, B).