PD-1(+) immune cell infiltration inversely correlates with survival of operable breast cancer patients.

The programmed death-1 (PD-1) molecule is mainly expressed on functionally "exhausted" CD8(+) T cells, dampening the host antitumor immune response. We evaluated the ratio between effective and regulatory T cells (Tregs) and PD-1 expression as a prognostic factor for operable breast cancer patients. A series of 218 newly diagnosed invasive breast cancer patients who had undergone primary surgery at Ruijin Hospital were identified. The influence of CD8(+) cytotoxic T lymphocytes, FOXP3(+) (Treg cell marker), and PD-1(+) immune cell counts on prognosis was analyzed utilizing immunohistochemistry. Both PD-1(+) immune cells and FOXP3(+) Tregs counts were significantly associated with unfavorable prognostic factors. In bivariate, but not multivariate analysis, high tumor infiltrating PD-1(+) cell counts correlated with significantly shorter patient survival. Our results suggest a prognostic value of the PD-1(+) immune cell population in such breast cancer patients. Targeting the PD-1 pathway may be a feasible approach to treating patients with breast cancer.