PAP Human

PAP is classified as a protein tyrosine phosphatase. Its primary function involves the dephosphorylation of tyrosine residues on proteins, which plays a crucial role in various cellular processes. In prostate cancer (PCa) cells, PAP dephosphorylates the ErbB-2/Neu/HER-2 receptor at phosphotyrosine residues, leading to reduced tumorigenicity . This interaction also regulates the androgen sensitivity of PCa cells, influencing their growth and proliferation .

PAP is found in high concentrations in seminal fluid, where it is believed to be involved in the liquefaction process of semen . The enzyme is also present in other tissues, including the bone, blood cells, and lysosomes, albeit in lower concentrations .

Historically, PAP was used as a biomarker for detecting prostate cancer and monitoring its progression. Elevated levels of PAP in the serum were associated with prostate cancer, particularly in cases with bone metastasis . However, with the advent of prostate-specific antigen (PSA) testing, the clinical use of PAP as a diagnostic marker has diminished .

The expression of PAP is regulated by various factors, including the NF-κB signaling pathway. Promoter analysis has revealed a novel binding sequence for NF-κB, suggesting that PAP expression can be regulated in an androgen-independent manner . This regulation is significant for understanding the progression of prostate cancer and developing potential therapeutic strategies.

Recent research has focused on the role of cellular PAP (cPAcP) in prostate cancer. Knockdown of cPAcP expression has been shown to allow androgen-sensitive PCa cells to develop a castration-resistant phenotype, where cells can proliferate under androgen-reduced conditions . Understanding the function and regulation of PAP could have a significant impact on prostate cancer therapy and management.