High expression of the checkpoint molecule PD-1 on regulatory and helper CD4+ T cells in metastatic breast cancer patients with poor prognosis

Abstract

Background: Recurrence and metastasis are common in patients of breast cancer even after chemotherapy and radiotherapy. This recurrence may occur due to the emergence of immunoregulatory T (Treg) cells and the immune checkpoint molecules such as programmed cell death protein 1 (PD-1) which are known to suppress anti-tumor immunity. Aim: The aim of this study is to investigate the numbers of Treg cells and the expression of PD-1 molecule on T cells in the peripheral blood of breast cancer patients at different stages (II, III, and IV) compared to healthy individuals. Materials and Methods: Blood samples were collected from early diagnosed metastatic cancer patients before surgery. Leucocytes were stained with different antibodies including CD4, CD25, CD127, and PD1, and then were analyzed by multiparametric flow cytometry. Results: The results showed that the relative and absolute numbers of Treg cells were significantly increased in breast cancer patients. Interestingly, we found a correlation between the numbers and cancer progression from stages II to III and IV, as compared with healthy individuals. Furthermore, significant increases in PD-1 expression were observed on Treg cells and CD4+ T cells in cancer patients as compared to healthy controls. This profile of PD-1 expression was also correlated with the poor prognosis of the patients. Conclusion: The results provide a better understanding of the immunomodulatory role of Treg cells and PD-1 expression in breast cancer patients who are the target for immunotherapy using checkpoint inhibitors.