CD8A and neoplasm: To define the impact of ATRi on CD8+ T cell activation and proliferation in vivo, we treated CT26 tumor-bearing mice with 75 mg/kg ATRi on days 1, 2, and 3 and immunoprofiled CD8+ T cells in tumor-infiltrating lymphocytes (TILs) and the periphery (spleen and draining lymph node [DLN]) on day 4.