Lymphocyte subsets: new hope for noninvasive biomarkers of prostate cancer.

Tumorigenesis and progression are driven by immune dysregulation and escape, thus evaluating immune function is crucial for the identification of diseases or health conditions. Currently, there is a lack of noninvasive biomarkers in the overall management of PCa to assess a patient's immune status and immune response to different treatment regimens. Lymphocyte subsets are directly involved in the surveillance, defense and regulation of the human immune system, and are primarily composed of T cells, B cells, and NK cells. The combined assay of lymphocyte subsets number, phenotype and function is currently a more accepted method of assessing immune function. Quantitative aspects are presented in terms of both absolute counts and relative percentages. Phenotypic molecules reflect host immunity mainly through markers such as HLA-DR, CD25, CD45RO, CD45RA, CCR7, and CD28. Markers, such as IFN-γ, Fas ligand, perforin, granzyme B, TCF-1 (marker for maintaining the stem cell nature, self-renewal, and undifferentiated state), TOX (marker of T cell exhaustion), and immune checkpoint molecules (TIM-3, PD-1, LAG3) can be used to represent the functions of lymphocyte subsets. Nevertheless, existing research conclusions are miscellaneous, and no studies have systematically reviewed the role of lymphocyte subsets in the diagnosis, treatment, and prognosis of PCa. In order to strengthen the comprehensive understanding and grasp of its role by urological surgeons, this review first introduces lymphocyte subsets in detail, and then condenses and summarizes the research progress of lymphocyte subsets in PCa from peripheral blood and tumor infiltration, respectively.