Prostatic Acid Phosphatase (PAP) is an enzyme primarily secreted by prostate epithelial cells, historically recognized for its role in hydrolyzing phosphate esters in seminal fluid. Though largely replaced by prostate-specific antigen (PSA) as a diagnostic marker, PAP remains relevant in specific clinical and research contexts. Elevated PAP levels in serum were once a key indicator of metastatic prostate cancer, but its current utility lies in immunohistochemistry (IHC) to distinguish prostate cancer from other malignancies and to monitor disease recurrence.
PAP antibodies are critical tools for detecting PAP expression in tissues or biological samples via techniques like IHC, ELISA, and Western blotting. These antibodies aid in studying PAP's biological functions, including its debated roles in tumor progression, bone metastasis, and immune modulation. Recent studies highlight PAP's potential as a therapeutic target, particularly in immunotherapies like sipuleucel-T, an FDA-approved vaccine for advanced prostate cancer that utilizes PAP-derived antigens to stimulate anti-tumor immune responses.
Structurally, PAP belongs to the hydrolase family, encoded by the ACPP gene on human chromosome 3. It exists as a homodimer, with enzymatic activity dependent on pH and substrate specificity. While its physiological role beyond the prostate remains unclear, PAP is also detected in non-prostatic tissues, including macrophages and neurons, suggesting broader regulatory functions. Research continues to explore its involvement in neuroendocrine cancers and interactions with cellular signaling pathways, reinforcing its dual significance as a diagnostic relic and emerging therapeutic avenue.