In our metastatic breast cancer model utilizing E0771-LG cells, suppression of CD8+ T cell cytotoxicity by MAMPC (M-MDSC) was reversed by a combination of catalase and SOD but not by L-NMMA, suggesting that M-MDSCs in the metastatic site of breast cancer use ROS rather than NO to suppress T cell functions. Here, CD8A is linked to breast cancer.