Liu C, et al. - In this study including breast cancer patients and sex-matched healthy controls, researchers determined the correlation of mRNA expression of programmed cell death protein 1 (PD-1), cluster of differentiation 28 (CD28), cytotoxic T-lymphocyte antigen-4 (CTLA-4), and cluster of differentiation 25 (CD25) with albumin (ALB)/globulin (GLB) ratio [(AGR)], ALB, GLB, total protein, pre-ALB, hemoglobin (Hb), body mass index (BMI), and prognostic nutritional index (PNI) in the peripheral blood. A negative correlation of AGR with PD-1 and CD25 mRNA levels was observed, while a positive association was seen between GLB and PD-1 mRNA levels. The PD-1 pathway may be influenced by the nutritional status of patients. Nutritional status may have implications for the optimization of cancer therapy.