A novel hybridoma antibody (PASE/4LJ) to human prostatic acid phosphatase suitable for immunohistochemistry

Abstract

Summary A murine monoclonal antibody PASE/4LJ to prostatic acid phosphatase (PAP) was used to immunostain a wide variety of sections of benign and malignant tissues (654 blocks). Non-neoplastic adult and fetal prostatic glands, primary and metastatic prostatic carcinomas, and scattered cells in prostatic and penile urethra were positive. Rat, dog and rabbit prostates were negative. Nine of 400 tumours of non-prostatic origin showed some positivity: 6/36 carcinoids, 1/9 islet cell tumours, 1/55 ovarian adenocarcinomas (serous) and one carcinosarcoma of the lung (epithelial portion). Positive staining was seen in islet cells in 4/5 specimens of normal pancreas, and in 4/9 blocks of normal pancreas surrounding a pancreatic tumour. Loops of Henle, maculae densae, and distal tubules in 10/10 fetal and 2/9 adult kidneys were also positive, with proximal tubules and collecting ducts negative. All other 159 blocks of non-neoplastic adult and fetal tissues were negative. The antibody was also affinity purified from ascitic fluid, and shown not to inhibit the enzyme activity of prostatic acid phosphatase.

Prostatic acid phosphatase expression in human tissues

“…In contrast, several studies failed to observe PAP staining in normal tissues, including bladder, breast, colon/rectum, epidermis, kidney, liver, lung, ovary, salivary glands, stomach, testes, and urethra [11,12,15,16]. Using qPCR to measure relative levels of PAP mRNA transcripts, Cunha and colleagues [14] found that, relative to prostate, PAP mRNA was expressed at low levels in several normal tissues, most notably in placenta, kidney, and testis.…”

“…Likewise, Cohen et al found weak diffuse PAP immunostaining in islets cells, but concluded the weak PAP signal was non-specific [21]. Additional studies have found PAP expressed in normal pancreatic tissue [11,12,18].…”

“…The studies have generally confirmed that the preponderance of PAP expression is in the prostate, though several studies have noted some extra-prostatic expression. PAP expression has been reported in liver cells, normal adult kidney [11,15]; granulocytes, parietal cells of the stomach [15]; urethral glands [16,17]; anal gland non-mucosal epithelium, rectal tissue [16]; salivary glands [18]; and ectopic prostate tissue in both uterine cervix and vagina [19].…”

“…In healthy individuals, PAP serum levels are low, on the order of 1-3 ng/mL, whereas serum levels are elevated in many individuals with metastatic prostate cancer [8][9][10]. Data from immunohistochemistry (IHC) studies indicate that > 95% of normal adult prostate tissue samples, including normal tissue adjacent to tumor, strongly express PAP [5,11,12]. Analyses of PAP mRNA levels by RNA blotting methods [13] and quantitative polymerase chain reaction (qPCR) using pooled tissue samples [14] indicate high levels of PAP mRNA expression in normal prostate tissue.…”

“…There is renewed interest in PAP as a prognostic tissue marker for T4 tumors [22], as a serum marker in clinical staging of prostate cancer [23], and for predicting recurrence after radical prostatectomy [24]. PAP is expressed in > 95% of the primary prostate adenocarcinomas as determined by IHC [11,12,15]. Goldstein observed that 80% (176 of 219) of PAP positive prostate adenocarcinomas from patients with Gleason scores of 6 to 10 expressed PAP in more than 25% of the malignant cells [25].…”