Although clock genes have been linked to T-cell depletion (CD8 and CD4 T-cell) and the upregulation of immunosuppressive molecules such as PD-L1 and CTLA-4 (Wu et al., 2019; Zhou J et al., 2020), more research is needed to determine the mechanism of action between circadian genes and immune checkpoints associated with BC prognosis. Here, CTLA4 is linked to breast cancer.