Relationship of prostatic acid phosphatase localization in human prostate by a monoclonal antibody with the Gleason grading system

Prostatic acid phosphatase (PAP) was localized in human prostate with a monoclonal antibody prepared against PAP isoenzyme II to determine patterns of its expression in normal, hyperplastic (BPH), and cancerous glands. The monoclonal antibody reacted with both isoenzymes II and IV in immunoblot studies. Formalin-fixed, paraffin-embedded tissue was used from patients who had not been treated with hormones or chemotherapy. In normal glands and BPH, there was marked variation in the intensity of PAP staining in morphologically otherwise similar epithelial cells. There was similar heterogeneity of staining in the adenocarcinomas. Rough quantification of the intensity patterns in the clinical groups indicated a slight shift to more intense staining in BPH and well-differentiated carcinomas but a progressive decline in the PAP staining in the moderately and poorly differentiated tumors. This decrease in intracellular staining with decreasing differentiation is not inconsistent with the clinical observation that serum levels of acid phosphatase generally increase with higher grade and disseminated tumors, since the enzyme is simply more accessible to the circulatory system in those cases. The same decrease may explain the few disseminated tumors that are not associated with elevated serum levels.     

Altered distribution of acid phosphatase in neoplastic prostatic cells

Summary Because of the well-known problem of variable cell differentiation encountered in the electron-microscopic evaluation of prostatic cancer, histochemical ultrastructural studies have been performed to assess whether an altered intracellular distribution of acid phosphatase is a more reliable index of malignant change. The results indicate that acid phosphatase activity not restricted to lysosomes is common in malignant cells, and that it may be an intermediate stage in the release of the enzyme into the serum.     

Production of specific antibody to purified prostatic acid phosphatase

Summary Prostatic acid phosphatase may well be a prime antigenic protein in prostatic tissue and fluid. Extraction of the enzyme in highly purified form from prostatic fluid and benign hypertrophic prostatic tissue provides a unique antigen capable of inducing a prompt and specific antibody response in the goat and rabbit as manifested by immunodiffusion, immunoelectrophoresis, and immuno-fluoresence techniques. In prostatic cancer patients with elevated serum acid phosphatase levels it is possible to detect humoral circulating PAP antigen by standard immunoelectrophoretic methods and to confirm the existence of the enzyme by radioautography, L-tartrate inhibition, and the Gomori or Burstone staining procedures. Preliminary indirect prostatic immunofluorescence studies consistently demonstrated characteristic fluorescent foci in the paranuclear areas of benign prostatic epithelial cells, the presumed area of synthesis of prostatic acid phosphatase. Consideration has been given to the possibility of the development of a radioimmunoassay for prostatic acid phosphatase utilizing a heterologous antiserum to the enzyme extracted from human prostatic fluid.     

Radioimmunoassay of bone marrow prostatic acid phosphatase

The clinical value of prostatic acid phosphatase (PAP) measurements in the bone marrow aspirate of patients with prostatic adenocarinoma has been unclear. Using a radioimmunoassay (RIA) to measure PAP, we have evaluated this potential indicator of occult metastases in 127 controls and in 300 patients with prostatic adenocarinoma. Elevations of the tumor marker were found in 9%, 10%, 19%, and 82% of patients with stages B, C, D₁, and D₂ adenocarcinoma respectively. Clinical follow-up ranging from 7 to 43 months (average 23 months) was available for 97 patients without any initial indication of metastasis by bone scan. In this group 11 patients had elevated levels of bone marrow acid phosphatase (BMAP) by RIA and four developed radiological evidence of bone metastais 21 – 25 months following initial staging. However, only three of the 86 patients with normal BMAP levels have developed bone metastasis. Our results indicate that measurement of bone marrow PAP by immunological methods has prognostic significance. Dilution of the bone marrow aspirate by peripheral blood, however, may limit the application of this technique.     

Cytochemistry and biochemistry of acid phosphatases VII: Immunohistochemistry of canine prostatic acid phosphatase

Acid phosphatase (E.C. 3.1.3.2.) has been isolated from canine prostatic gland homogenates by gel permeation chromatography (AcA34 or G150), by affinity chromatography (con A-Sepharose), or by using fluid phase liquid chromatography (FPLC) using Superose 12 and Mono P columns. Acid phosphatase-enriched fractions were submitted to analytical SDS-PAGE or to analytical isoelectric focusing. A protein with a molecular weight of 30 kD (on SDS gels) was used for immunization of rabbits. The antiserum produced was cross-reactive with prostatic acid phosphatase (canine and human) as shown by immunoblotting. When applied to paraffin or plastic sections of normal canine prostate, a positive immunoreaction was found exclusively in the secretory cells. In experimentally altered glands (castration and/or hormone treatment), a varying pattern of immunoreactive cells was found. In canine prostatic carcinomas, intensively reacting cell clusters were found along with nonreactive cells. The antiserum was also slightly cross-reactive with the respective human antigen, but the cross-reactivity of an antiserum prepared against human prostatic secretory acid phosphatase with canine prostatic acid phosphatase was far more pronounced.     

Solid-phase immunofluorescent and immunoadsorbent assays of serum prostatic acid phosphatase

Human prostatic acid phosphatase was purified to homogeneity from malignant prostatic tissue by Tween 80 extraction and 40-75% ammonium sulfate precipitation, followed by Con A-Sepharose, DEAE-cellulose, and gel filtration chromatography. A specific antiserum was raised by immunizing female goats or rabbits with the purified enzyme. This antiserum did not cross-react with the acid phosphatase of other human tissues. Two immunochemical methods, a solid-phase fluorescent immunoassay and a solid-phase immunoadsorbent assay, were developed. The IgG antibody fraction from antiprostatic acid phosphatase was conjugated to CNBr-activated Sepharose 4B, which was then used in the two immunoassays to separate serum prostatic acid phosphatase from other acid phosphatases or serum proteins. The enzyme activity was subsequently measured by incubating the solid-phase bound prostatic acid phosphatase with α-naphthyl phosphate and quantitating the fluorescent product with a spectrophotofluorometer (immunofluorometric assay) or quantitating the α-naphthol-FRBS colored complex with a spectrophotometer (immunoadsorbent assay). The sensitivity of this immunofluorometric assay was 60 pg/ml, more sensitive than other immunoassays. The results obtained from clinical evaluation indicate that serum prostatic acid phosphatase in prostate cancer can be detected in significant percentage with early stages of prostatic cancer. The sensitivity of the immunoadsorbent assay was 0.22 IU/l of enzyme activity or 0.88 ng of prostatic acid phosphatase protein per ml serum. Initial clinical evaluation demonstrated that 19 of 25 patients with early stages of prostate cancer and 12 of 14 patients with metastatic prostate cancer exhibited an elevated serum PAP level (over all 79%), as compared with only six and eight patients respectively (overall 35%), by a conventional chemical method.     

Fundamental biochemical and immunological aspects of prostatic acid phosphatase

Prostatic acid phosphatase (PAP) was purified from human malignant prostate tissue by means of ammonium sulfate fractionation followed by sequential chromatographies of ion exchange, affinity column, and gel filtration. PAP has a molecular weight of 100,000 and consists of two subunits of 50,000. Owing, in part, to sialic acid contents in the molecule, PAP has multiple isoelectric points (pIs) at 4.2-5.5. In 0.2 M citrate, PAP has the highest affinity (Km 9.2 × 10^?5 M) in hydrolyzing α-naphthyl phosphate among the phosphomonoesters. Tartrate and heat at 37?C for 2 hours almost completely inhibit PAP enzymic activity. By immunoprecipitate technique, anti-PAP heteroantiserum exhibited a distinct immunologic characteristics. Further, PAP possessed different antibody-binding site from enzyme hydrolytic site.     

Two-dimensional characterization of prostatic acid phosphatase, prostatic specific antigen and prostate binding protein in expressed prostatic fluid

Specimens of pooled prostatic fluid, collected by rectal massage from men under 50 years of age with no apparent prostatic disorders, were subjected to two-dimensional gel electrophoresis to study the composition of its proteins. In a preliminary study, a total of 57 major protein groups were detected. In the present study, we attempted to identify, in the two-dimensional gels, those that are related to prostate-associated proteins, i.e., prostatic acid phosphatase (PAP), prostatic specific antigen (PSA), and prostate binding protein (PBP). Individual proteins were recognized by the procedure of Western Blot using specific antisera with peroxidase-antiperoxidase as the staining reagent. Each protein spot in the two-dimensional gel was expressed, along the abscissa, by its isoelectric point (pI) and, along the ordinate, by the molecular weight (MW). PAP consisted of a train of more than ten protein spots that occupied an area in the gel from pI 7.0, MW 45,000 to pI 6.0, MW 50,000. Four protein spots with a MW of 34,000 and a pI range of 8.2-8.8 were identified as PSA. PBP was observed as having three protein spots that were located at pI 5.6-6.6 with a single MW of 15,000. For PAP and PSA, additional protein spots with lower MWs also stained positively with the specific antisera, suggestive of the presence of degradative products of these proteins. Following the removal of the serum-related proteins by an extensive absorption with anti-human serum antibody by affinity chromatography, the prostatic fluid contained 27 major groups of non-serum proteins. These non-serum proteins in the prostatic fluid included PAP, PSA, PBP, and their related smaller molecular species. These results indicate that the prostatic fluid contains PAP, PSA, PBP and that their presence and the patterns of their distribution in the two-dimensional gels should be considered as the characteristic property of the prostatic secretions.     

Immunohistochemical prostatic acid phosphatase level as a prognostic factor of prostatic carcinoma

To determine whether prostatic acid phosphatase (PAP) immunoreactivity in prostatic adenocarcinoma is a reliable prognostic factor, the PAP immunohistochemical distribution has been examined in 78 prostatic carcinoma cases. The intensity of PAP immunostaining was graded from 0 to 2, and the scores of the primary and the secondary staining patterns were added to assess the extent of the PAP expression in needle biopsy specimens. As a result, a higher cancer-specific survival rate was observed in patients showing a greater PAP immunostaining (P less than 0.01). Further, a multivariate analysis was made of possible prognostic factors (age, stage, Gleason score, serum PAP, PAP-immunostaining score, and the initial treatment) to estimate the extent of their impact on cancer-specific survival. Results have confirmed that the difference in PAP immunoreactivity is an excellent, independent prognostic factor for prostatic carcinoma.     

Immunoelectron microscopic demonstration of prostatic acid phosphatase in human hyperplastic prostate

Immunoelectron microscopic studies were done on prostatic tissues obtained from patients with benign hyperplasia. Rabbit IgG-peroxidase conjugate against purified human prostatic acid phosphatase band 2 (HPAP-2) was used for studies. Under the light microscope, the columnar secretory epithelia of prostatic glands showed different intensity and distribution of immunostaining whereas the basal cells were unstained. Under the electron microscope, the secretory epithelial cells often showed electron-dense reaction product in the Golgi apparatus and secretory vesicles and vacuoles, and only sparingly in the cisternae of nuclear envelope and rough ER. Sometimes, fusion of secretory vacuolar membrane and plasma membrane and discharge of the vacuolar contents into the extracellular space were noted. The surfaces of microvilli at the apical portion of the columnar epithelia and the lumen of the glandular acini always showed reaction product. These findings suggest that HPAP-2 may be synthesized in the rough ER and transported to the Golgi apparatus where it is concentrated and transferred to the secretory vesicles and vacuoles. HPAP-2 is finally discharged into the extracellular spaces through exocytosis, a secretory mechanism similar to that of other secretory proteins.     

Counterimmunoelectrophoretic studies of serum prostatic acid phosphatase

A counterimmunoelectrophoretic (CIEP) assay for the specific determination of prostatic acid phosphatase (PAP) is described. PAP was obtained from benign human prostatic tissue and a specific antiserum to this enzyme was produced in rabbits and goats. The lowest detectable activity of PAP was at 0.3 IU/l or 4 ng./0.1 ml. This CIEP method was compared to a standard biochemical method (Roy) on a wide spectrum of prostatic and nonprostatic disease. Nonprostatic malignancies and other disorders associated with hyperacidphosphatasemia by the biochemical method were found to be nonreactive for PAP by CIEP. Patients under treatment with various stages of prostatic carcinoma showed comparable elevations by both methods (35%). In untreated patients, the CIEP was statistically most sensitive in stage A (39% by CIEP and 14% by chemical).     

A clinical assay for prostatic acid phosphatase using choline phosphate as a substrate: Comparison with thymolphthalein phosphate

We describe an assay method using choline O-phosphate as a substrate for the measurement of serum prostatic acid phosphatase as an aid in the diagnosis of prostatic cancer. Choline phosphate is hydrolyzed by homogeneous prostatic acid phosphatase, and it is also hydrolyzed by an acid phosphatase present in the serum of prostatic carcinoma patients. In contrast, serum samples from apparently healthy persons do not exhibit any significant choline O-phosphate phosphatase activity. There is a correlation of 98% (n = 46) between choline O-phosphate phosphatase activity and typical measurement for prostatic acid phosphatase activity carried out using thymolphthalein monophosphate as the substrate. The new method appears to be as accurate as colorimetric methods based on thymolphthalein phosphate as a substrate. Although not as sensitive as immunologically based methods, the present technique for measuring prostatic acid phosphatase activity using choline phosphate as a substrate is economical and relatively simple.     

Creatine kinase isoenzyme (CK-BB) in combination to prostatic acid phosphatase measured by RIA in the diagnosis of prostatic cancer

Summary Creatine kinase isoenzyme (CK-BB) measured by mass was used to determine its value in the early diagnosis of prostatic cancer. Sera of patients with prostatic carcinoma of various stages (treated and untreated) were compared to normal male sera and sera of patients with benign hyperplasia of the prostate (BPH) with respect to CK-BB. The sera were simultaneously tested for PAP content. The sensitivity of the CK-BB-RIA was 1.63+/-0.08 g/l and reproducibility in the higher and lower concentration range 7.6% and 10.5%, respectively. CK-BB alone or in combination with PAP is no marker for early detection of prostatic cancer. In individual cases changes occurred similar to those found with a malignant growth of the prostate.     

Isolation,characterization, and spontaneous interconversion of two forms of human prostatic acid phosphatase

Starting with human prostatic acid phosphatase (HPAP) purified by affinity chromatography on Sepharose-bound N-(6-aminohexyl)tartramic acid [Van Etten, R. L. and Saini, M. S. (1978) Clin. Chem. 24 , 1525], two forms of the enzyme can be separated by gradient elution DEAE-cellulose chromatography. The two enzyme forms are electrophoretically distinguishable on high pH gels. Under some conditions of storage one of these forms undergoes a conversion to the other. Both forms have identical amino acid compositions and V_max values with typical substrates, but differences are observed in circular dichroism spectra, relative fluorescence intensities, K_m values, and carbohydrate composition. It is concluded that the two forms differ only in the structure of their (nonphosphorylated) carbohydrate side chains. In view of the possible interconversion of the two forms upon storage, caution must be observed in any attempt to attach clinical significance to the relative amounts of the two forms.     

Cytochemistry and biochemistry of acid phosphatases. VI: Immunoelectron microscopic studies on human prostatic and leukocytic acid phosphatases

Using different antisera against secretory and lysosomal prostatic acid phosphatases, the localization of the respective antigens was studied in the human prostate at the ultrastructural level. Secretory acid phosphatase was confined exclusively to the secretory vacuoles of the glandular cells. Discharge of the secretory material occurs in a merocrine type of secretion. The identical antigen could be localized in the primary and secondary granules of neutrophil and eosinophil granulocytes separated from human peripheral blood. The antiserum used was also cross-reactive with the canine prostate, where a very distinct immunoreaction was observed with the secretory granules of the glandular cells. The antibodies directed against lysosomal acid phosphatases prepared from prostatic homogenates consistently gave a positive immunoreaction with dense bodies, lipofuscin, and secretory granules. The respective antigens were present also in neutrophil and eosinophil granulocytes. These findings do not identify the existence of a prostate-specific acid phosphatase, which does not exist. The secretory form of the isoenzymes, however, is clearly distinct from the lysosomal form, both of which are present in granulocytes. Therefore the origin of acid phosphatases elevated in peripheral blood in cases of metastatic prostatic cancer could be either the carcinomatous cells or leukocytes destroyed during the process of metastasis.     

Prostatic acid phosphatase in the serially transplantable human prostatic tumor lines PC-82 and PC-EW

Summary The correlation between tumor volume of untreated tumor-bearing nude mice and serum concentration of prostatic acid phosphatase (PAP/RIA) was studied in the hormone-dependent serially transplantable human prostatic tumor models PC-82 and PC-EW. The normal serum level of PAP in control male nude mice without tumor was found to be 0.9±0.3 ng/ml. Elevated PAP serum concentrations were never found in animals without tumor (a highly specific diagnostic technique). A close correlation was observed between the concentration of PAP in the serum (range 0.3 to 154 ng/ml) and the tumor volume (range 10.0 to 6, 530 mm³) of 104 untreated mice bearing a PC-82 or PC-EW human prostatic tumor. This correlation was comparable in both tumor lines (p<0.001). The positive effect of endocrine manipulation which resulted in tumor diameter decrease or growth arrest with regressive histogical patterns, showed the normal PAP serum level, too. After successful treatment PAP was found to be normal, independent from the residual tumor mass. By contrast, in the event of only retarded tumor growth, the PAP level still correlated with the tumor burden.Supported by the Wilhelm Sander Foundation Grant 85.029.1     

Spontaneous circadian fluctuations of prostate specific antigen and prostatic acid phosphatase serum activities in patients with prostatic cancer

Summary Spontaneous circadian variations of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP), determined simultaneously by radioimmunoassay (RIA), were investigated by multiple sampling, over a 24-hour period, in 32 patients with prostatic cancer. In 29/32 patients (91%), the coefficient of variation of 24-hour values, for either marker, was greater than that of the RIA method at the same range of values; stage D patients showed the greatest spontaneous variability. Fluctuations around the mean of 24-hour values ranged from-65% to +85% for PAP, from-72% to +190% for PSA, occurring random and independently for each marker. Variability was about 20% greater for PSA than for PAP. The existence of spontaneous fluctuations should be considered in multiple marker evaluation of prostatic cancer patients.Preliminary results of this study have been presented at the International Symposium on Hormonal Therapy of Prostatic Diseases —Basic and Clinical Aspects, April 6–8, 1987, Milan, Italy     

Prostatic acid phosphatase levels (enzymatic method) from completely sectioned,clinically benign,whole prostates

Clinically benign, whole, untrimmed prostates were obtained from 104 patients at autopsy, completely sectioned, and examined microscopically. The histological and gross findings of the prostate were correlated with premortem prostatic acid phosphatase levels (PAP, enzymatic method, ACA, Dupont Co.) to determine how often carcinoma of the prostate (CAP) affected PAP levels and to identify other findings within the prostate associated with elevated PAP levels. Sixty (58%) prostates did not have CAP, 34 (33%) had CAP smaller than 1 ml in volume, and 10 (10%) had CAP larger than 1 ml in volume. PAP levels were elevated (greater than 1 U/L) in 8 of the 60 (13%) prostates without CAP, in 2 of the 34 (6%) prostates with CAP smaller than 1 ml, and in 1 of the 10 (10%) prostates with CAP larger than 1 ml. These differences were not statistically significant. Likewise, a statistically significant correlation between PAP levels and patient age, patient race, severe inflammation, or high grade prostatic intraepithelial neoplasia (PIN) was not found. However, there was a statistically significant correlation between PAP levels and prostate weight (P < 0.0001). This study suggests that PAP cannot distinguish between patients with clinically undetected CAP and patients without CAP. Furthermore, elevated PAP levels are often not due to metastatic CAP and additional evidence should be present, even in patients with known CAP, before an elevated PAP level is considered to be conclusive evidence of metastatic CAP. © 1996 Wiley-Liss, Inc.