Prostate-specific antigen (PSA) as a possible biomarker in non-prostatic cancer: A review

Prostate-specific antigen (PSA) is a serine protease produced by epithelial prostatic cells and its main function is to liquefy seminal coagulum. Currently, PSA is a biomarker for the diagnosis and screening of prostate cancer and it was the first cancer biomarker approved by the FDA. The quantity and serum isoforms of male PSA, allows distinguishing between carcinoma and benign inflammatory disease of the prostate. Initially, it was thought that PSA was produced only by the prostate, and thus, a protein that was expressed exclusively in men. However, several authors report that PSA is a protein that is expressed by multiple non-prostatic tissues not only in men but also in women. Some authors also report that in women, the expression of this protein is highly related to breast and colon cancer and therefore can act as a possible biomarker for early detection, diagnosis and prognosis of these cancers in women. In this review, we will focus on the characteristics of the PSA at a molecular level, its current clinical implications, the expression of this protein in non-prostatic tissues, and its relationship with cancer, especially in women.