PSA

PSA
Name	Prostate-specific antigen
Alt	PSA logo
Uniprot	P07288
Chromosome	19q13.33

PSA is a serine protease encoded by the human gene KLK3 located on chromosome 19. It is produced primarily by epithelial cells of the prostate and is widely measured in blood as a biomarker for prostate-related conditions, including neoplasia and benign disorders. Clinical and epidemiological studies have shaped its role in screening, diagnosis, and monitoring of prostate disease across populations and health systems.

Overview

The protein is a 34 kDa glycoprotein in the kallikrein family related to KLK2 and KLK4, with phylogenetic ties to other mammalian kallikreins studied in comparative genomics. Structural analyses reference crystallography methods used in labs such as those at EMBL and Max Planck Society-affiliated centers. The gene locus has been examined in genome-wide association studies by consortia including the 1000 Genomes Project and International HapMap Project to identify polymorphisms affecting expression. Protein processing and secretion have been characterized in cell lines such as LNCaP and PC-3.

Biology and Biochemistry

The molecule functions as a chymotrypsin-like protease that cleaves semenogelins in seminal plasma; enzymology work has been conducted alongside studies of trypsin, chymotrypsin, and other serine proteases. Post-translational modifications include N-linked glycosylation sites characterized by mass spectrometry labs at institutions like Cold Spring Harbor Laboratory and Scripps Research. Regulation of transcription involves androgen receptor signaling pathways described in literature from groups at Dana-Farber Cancer Institute and Johns Hopkins University, linking it to androgen-responsive elements similar to those studied for SRY-box 9 and FOXA1. Interaction studies cite complexes with protease inhibitors such as alpha-1-antichymotrypsin and alpha-2-macroglobulin.

Clinical Use and Testing

Serum measurement became standardized following methods developed at institutions including Mayo Clinic and companies like Roche and Abbott Laboratories. Assays include immunoassays such as enzyme-linked immunosorbent assay platforms used in clinical laboratories certified by CLIA and quality-controlled through organizations like CAP (College of American Pathologists). Laboratory workflow integrates pre-analytical variables addressed in guidelines from American Association for Clinical Chemistry and proficiency testing from AABB. Specimen handling, assay calibration, and inter-assay comparability have been topics in multicenter trials coordinated by groups including European Association of Urology and National Cancer Institute consortia.

Interpretation and Reference Ranges

Reference limits were initially proposed in cohort studies at Brigham and Women's Hospital and validated in population cohorts such as those from Framingham Heart Study adaptations for male cohorts and in large screening trials like Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Age-specific ranges and race-adjusted considerations were evaluated by teams at Fred Hutchinson Cancer Research Center and Memorial Sloan Kettering Cancer Center. Laboratories report total and, in some cases, free fractions using cutoffs that have been endorsed or debated in statements from USPSTF and American Urological Association.

PSA in Prostate Cancer Screening and Diagnosis

Large randomized trials — notably those run by ERSPC and PLCO Cancer Screening Trial investigators — assessed mortality impact, leading to position statements from entities such as NCCN and US Preventive Services Task Force. Diagnostic algorithms combine serum values with imaging modalities like multiparametric MRI protocols developed at centers including Mayo Clinic and biopsy techniques pioneered at Memorial Sloan Kettering Cancer Center. Risk calculators integrate variables from cohorts studied by Prostate Cancer Prevention Trial and genomic classifiers that reference work from Cancer Genome Atlas efforts.

PSA in Non-malignant Conditions

Levels are influenced by benign prostatic hyperplasia described in pathology series from Johns Hopkins Hospital and by inflammatory processes including acute and chronic prostatitis studied at Mayo Clinic and National Institutes of Health. Iatrogenic elevations are associated with procedures such as transrectal ultrasound-guided biopsy techniques developed by interventional teams at Cleveland Clinic and catheterization practices outlined by American Urological Association guidelines. Ejaculatory activity and recent instrumentation are addressed in patient preparation protocols from European Association of Urology.

Controversies and Guidelines

Debate over population screening balances findings from trials involving ERSPC and PLCO Cancer Screening Trial with harms documented in overdiagnosis analyses by researchers at Harvard School of Public Health and Yale School of Medicine. Guideline differences have been issued by organizations including USPSTF, American Urological Association, European Association of Urology, and NCCN, generating varied recommendations on age thresholds, shared decision-making frameworks promoted by Institute of Medicine-affiliated panels, and use of adjunctive biomarkers developed by commercial entities such as Myriad Genetics and BioMérieux. Emerging strategies incorporate risk stratification using genomic tests from companies studied in multicenter validations supported by National Cancer Institute networks.

Category:Proteins