CD274 and breast cancer: Additionally, we found that treatment of breast cancer patients with everolimus plus letrozole showed the tendency to increase the ratio of peripheral Tregs to CD4+ T cells and PD-L1 expression in tumor and decrease tumor Ki67 index and tumor-infiltrating Tregs, and patients with a greater increase of tumor-specific CTLs showed more sensitive to neoadjuvant everolimus in combination with letrozole.