CMTM6 and breast cancer: Notably, increasing evidence proved that CMTM6 can maintain the expression of PD-L1 and enhance the ability of the expression of PD-L1 in tumor cells to inhibit T cells (Burr et al., 2017; Mezzadra et al., 2017), and the dual knockdown of CMTM6 and CMTM7 observably downregulated the expression of PD-L1 in the breast cancer cell line MCF-7Mes than the single knockdown of CMTM6 (Xiao et al., 2021).