Blood expression of CTLA-4, PD-1, and PD-L1 as potential prognostic and diagnostic markers for breast cancer: a systematic review.

The risk of developing cancer is significantly higher for individuals with compromised immune function, as the immune system plays a crucial role in defending the body against tumor cells. In the present study, we aimed to evaluate the blood expression of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) as prognostic markers for patients with breast cancer. We searched the PubMed, EMBASE, Web of Science, and Medline (Ovid) databases to find relevant studies. The search strategy encompassed utilization of CTLA-4, PD-1, PD-L1, breast cancer, mRNA expression, blood, and prognostic markers as keywords. We chose seven studies published between July 2010 and July 2022, involving 1328 patients. Our study indicated that blood mRNA expression of CTLA-4, PD-1, and PD-L1 is higher in patients with breast cancer than in healthy individuals. Blood CTLA-4, PD-1, and PD-L1 high levels can be considered as poor prognosis in patients with breast cancer. However, it appears that simultaneously using several prognostic biomarkers at the same time can be more useful.