Acid phosphatases are enzymes capable of hydrolyzing orthophosphoric acid esters in an acid medium. This gene is upregulated by androgens and is down-regulated by estrogens in the prostate cancer cell line. ACPT dephosphorylates receptor tyrosine-protein kinase erbB-4 and inhibits the ligand-induced proteolytic cleavage. ACPT is predominantly expressed in testis but exhibits a lower level of expression in testicular cancer tissues than in normal tissues. ACPT has structural similarity to prostatic and lysosomal acid phosphatases. Alternatively spliced transcript variants have been described, but their biological validity has not been determined.