Expression Of Prostatic Acid Phosphatase Research Articles

Analysis of the molecular networks in androgen dependent and independent prostate cancer revealed fragile and robust subsystems.

Androgen ablation therapy is currently the primary treatment for metastatic prostate cancer. Unfortunately, in nearly all cases, androgen ablation fails to permanently arrest cancer progression. As androgens like testosterone are withdrawn, prostate cancer cells lose their androgen sensitivity and begin to proliferate without hormone growth factors. In this study, we constructed and analyzed a mathematical model of the integration between hormone growth factor signaling, androgen receptor activation, and the expression of cyclin D and Prostate-Specific Antigen in human LNCaP prostate adenocarcinoma cells. The objective of the study was to investigate which signaling systems were important in the loss of androgen dependence. The model was formulated as a set of ordinary differential equations which described 212 species and 384 interactions, including both the mRNA and protein levels for key species. An ensemble approach was chosen to constrain model parameters and to estimate the impact of parametric uncertainty on model predictions. Model parameters were identified using 14 steady-state and dynamic LNCaP data sets taken from literature sources. Alterations in the rate of Prostatic Acid Phosphatase expression was sufficient to capture varying levels of androgen dependence. Analysis of the model provided insight into the importance of network components as a function of androgen dependence. The importance of androgen receptor availability and the MAPK/Akt signaling axes was independent of androgen status. Interestingly, androgen receptor availability was important even in androgen-independent LNCaP cells. Translation became progressively more important in androgen-independent LNCaP cells. Further analysis suggested a positive synergy between the MAPK and Akt signaling axes and the translation of key proliferative markers like cyclin D in androgen-independent cells. Taken together, the results support the targeting of both the Akt and MAPK pathways. Moreover, the analysis suggested that direct targeting of the translational machinery, specifically eIF4E, could be efficacious in androgen-independent prostate cancers.

Expression of prostatic acid phosphatase (PSAP) in transurethral resection specimens of the prostate is predictive of histopathologic tumor stage in subsequent radical prostatectomies

Clinical management of incidental prostate cancer (IPC) remains challenging since its clinical course cannot be predicted by conventional histopathology. Aiming to define predictive factors in IPC, we correlated the immunohistochemically detected expression of prostate-specific antigen (PSA), prostatic acid phosphatase (PSAP), alpha-methylacyl-CoA racemase (AMACR, p504s), and androgen receptor in transurethral resection specimens with Gleason scores and histologic staging on the corresponding radicals in a cohort of 54 patients (mean age, 65.9 years; range, 49-80 years). PSAP expression showed a significant correlation with tumor staging (rho = -0.37; p = 0.02) but not with Gleason scores (rho = -0.06; p = 0.69). K-statistics revealed a highly significant moderate interobserver agreement concerning the evaluation of PSAP staining (K = 0.47; p < 0.001). In contrast, the other markers assessed failed to correlate with conventional histopathology. Therefore, PSAP might be predictive of tumor stage in IPC and represent a valuable adjunct for clinical decisions in terms of individual therapeutic management.

Prostatic Acid Phosphatase as a Target Molecule in Specific Immunotherapy for Patients With Nonprostate Adenocarcinoma

Prostatic acid phosphatase (PAP) is one of the prostate-related antigens that are applicable to specific immunotherapy for patients with prostate cancer. In this study, we determined whether or not PAP could be a target molecule in specific immunotherapy for patients with nonprostate cancer. A variety of adenocarcinoma cell lines were examined for their PAP expression at the mRNA and protein levels by reverse transcription polymerase chain reaction and western blot analysis, respectively. Considerable percentages of colon, gastric, and breast cancer cell lines were found to be positive for PAP at both the mRNA and the protein levels. The PAP expression in cancer tissues was also confirmed by immunohistochemical staining. In addition, we examined whether cancer-reactive cytotoxic T lymphocytes (CTLs) could be induced from peripheral blood mononuclear cells (PBMCs) of human leukocyte antigen (HLA) A24+ nonprostate cancer patients by in vitro stimulation with a PAP peptide. As a result, tumor-specific CTLs could be induced from the PBMCs of HLA-A24+ colon and gastric cancer patients. Their cytotoxicity against HLA-A24+ cancer cells was dependent on PAP peptide-specific and CD8+ T cells. These findings indicate that PAP could be a target molecule in specific immunotherapy for patients with nonprostate adenocarcinomas including colon and gastric cancers.

Transcriptional activation of the human prostatic acid phosphatase gene by NF-kappaB via a novel hexanucleotide-binding site.

Human prostatic acid phosphatase (PAcP) is a prostate epithelium-specific differentiation antigen. Cellular PAcP functions as a neutral protein tyrosine phosphatase and is involved in regulating androgen-promoted prostate cancer cell proliferation. Despite the fact that the promoter of the PAcP gene has been cloned, the transcriptional factors that regulate PAcP expression remain unidentified. This article describes our analyses of the promoter of the PAcP gene. Deletion analyses of the promoter sequence up to -4893 (-4893/+87) revealed that a 577 bp fragment (-1356/-779) represents the unique positive cis-active element in human prostate cancer cells but not in HeLa cervix carcinoma cells. Interestingly, the 577 bp fragment contains a non-consensus nuclear factor kappaB (NF-kappaB)-binding site that is required for NF-kappaB up-regulation in prostate cancer cells, while NF-kappaB failed to have the same effect in HeLa cells. Conversely, inhibition of the NF-kappaB pathway stopped p65 NF-kappaB activation of the p1356 promoter activity. Gel shift and mutation analyses determined that AGGTGT (-1254/-1249) is the core sequence for NF-kappaB-binding and activation. Biologically, tumor necrosis factor-alpha (TNF-alpha) activated endogenous PAcP expression in LNCaP human prostate cancer cells. The data collectively indicate that NF-kappaB up-regulates PAcP promoter activity via its binding to the AGGTGT motif, a novel binding sequence located inside the cis-active enhancer element in human prostate cancer cells.

Suppression of LNCaP prostate cancer xenograft tumors by a prostate-specific protein tyrosine phosphatase, prostatic acid phosphatase.

Although the molecular mechanism of androgen-independent prostate cancer growth and progression has been gradually elucidated, there is limited effective treatment for this prevalent disease. Human prostatic acid phosphatase (PAcP), a major protein tyrosine phosphatase in prostate epithelium, plays a critical role in regulating the growth of prostate cancer cells. In prostate carcinomas, the expression of cellular PAcP decreases. To explore directly the possible therapeutic potential of cellular PAcP, we investigated the suppression effect of PAcP by utilizing cDNA direct intratumoral administration in androgen-independent LNCaP xenograft tumors. An androgen-independent LNCaP cell model (C-33 and C-81 cells) and stable subclones of PAcP cDNA-transfected C-81 cells (LNCaP-23 and LNCaP-34 cells) were used for the experiments. We examined the growth property and expression of PAcP and c-ErbB-2 of these different LNCaP cells in vitro and in vivo. We subsequently investigated the growth suppression effect of PAcP cDNA intratumoral injection in pre-established C-81 xenograft tumors, and analyzed the expression of PAcP, prostate-specific antigen (PSA), proliferating cell nuclear antigen (PCNA), and c-ErbB-2 in the tumors by immunohistochemistry and Western blotting. The different LNCaP cells exhibited different growth property and tumorigenicity, both in cell culture and xenograft. Biochemical characterizations revealed that the level of cellular PAcP correlated negatively with the growth property of different LNCaP cells, while the level of tyrophosphorylated c-ErbB-2 had an inverse correlation with cellular PAcP. The single intratumoral administration of the wild type PAcP cDNA showed a significant suppression effect on C-81 xenograft tumor growth, compared to vector alone-injected control (P<0.05). In the tumors injected with this PAcP cDNA, the PAcP expression was detected 1 week (wk) after injection, but was undetectable at 6 wk, which inversely correlated with the level of tyrophosphorylated c-ErbB-2 and the degree of cell proliferation indicated by PCNA staining. Our results clearly demonstrated that cellular PAcP has a suppression effect on the growth of androgen-independent LNCaP xenograft tumors. This effect occurs at least partly through the dephosphorylation of c-ErbB-2 by PAcP, the prostate-specific protein tyrosine phosphatase. The data indicates that human PAcP could be utilized in the corrective gene therapy for a subgroup of androgen-independent human prostate cancer cells that lack cellular PAcP expression.

ErbB-2 signaling is involved in regulating PSA secretion in androgen-independent human prostate cancer LNCaP C-81 cells.

The expression and secretion of prostate-specific antigen (PSA) are regulated by androgens in normal prostate secretory epithelial cells. In prostate cancer patients, the serum PSA level is usually elevated and cancer cells are initially responsive to androgens. However, those cancer cells become androgen-independent after androgen ablation therapy. In hormone-refractory cancer patients, even in an androgen-deprived environment, the circulation level of PSA rebounds and is constitutively elevated through a yet unknown mechanism. Tyrosine phosphorylation of ErbB-2 is involved in regulating the androgen-responsive phenotype of prostate cancer cells, and it is at least partly regulated by the cellular form of prostatic acid phosphatase (PAcP), a prostate-unique protein tyrosine phosphatase. We investigated the ErbB-2 signal pathway in androgen-independent PSA secretion. LNCaP C-81 cells, which are androgen-independent LNCaP cells lacking endogenous PAcP expression with a hypertyrosine phosphorylated ErbB-2, secreted a higher level of PSA in conditioned media than did androgen-sensitive LNCaP C-33 parental cells. A restored expression of cellular PAcP in C-81 cells was concurrent with a decrease in tyrophosphorylation of ErbB-2 and reduction of PSA secretion. Moreover, transient transfection of C-33 cells with the wild-type ErbB-2 or a constitutively active mutant of MEK1 cDNA resulted in an increased level of secreted PSA. The elevation of secreted PSA level by the forced expression of ErbB-2 was inhibited by an MEK inhibitor, PD98059. In C-81 cells, the expression of a dominant negative mutant of ErbB-2 reduced the secreted level of PSA. The inhibition of ErbB-2 or mitogen-activated protein (MAP) kinases by specific inhibitors AG879, AG825, or PD98059 led to a decrease in PSA secretion. Taken together, our data clearly indicate that the ErbB-2 signal pathway via MAP kinases (ERK1/2) is involved in regulating the secretion of PSA by androgen-independent human prostate cancer LNCaP C-81 cells in an androgen-depleted environment.

DECREASED EXPRESSION OF CELLULAR PROSTATIC ACID PHOSPHATASE INCREASES TUMORIGENICITY OF HUMAN PROSTATE CANCER CELLS

Understanding cell proliferation regulation in hormone refractory prostate cancer may provide answers for novel solutions. Protein tyrosine phosphatases have been thought to have key roles in regulating cell proliferation and be involved in oncogenesis, although to our knowledge their functional roles in human prostate cancer remain unknown. Human prostatic acid phosphatase (PAcP), a major phosphatase in prostate epithelium, has been shown to function as a neutral protein tyrosine phosphatase in these cells. We evaluated the biological significance of cellular prostatic acid phosphatase expression in human prostate cancer cells. Immunohistochemical testing of human prostate cancer archival specimens was done to evaluate the expression of cellular PAcP. Immunoprecipitation and immunoblotting were performed to determine cellular PAcP and SH2 domain-bearing tyrosine phosphatase-1 levels as well as tyrosine phosphorylation of c-ErbB-2/neu in different human prostate cancer cells. The biological behavior of LNCaP derivative sublines was characterized in vitro and in vivo by soft agar analysis and xenograft animal inoculation. Immunohistochemical staining of human prostate clearly showed that cellular levels of PAcP significantly decreases in prostate cancer cells (p <0.001). The results of biochemical characterization revealed that the cellular level of PAcP but not SHP-1, another differentiation associated protein tyrosine phosphatase, consistently correlated negatively with the growth of several human prostate cancer cell lines. Reintroducing cellular PAcP activity in prostate cancer cells by PAcP complementary DNA transfection resulted in decreased tyrosine phosphorylation of c-ErbB-2/neu, decreased proliferation rates in culture as well as decreased anchorage independent growth in soft agar. The xenograft animal model demonstrated that a higher tumor growth rate as well as larger size is associated with a lower level of cellular PAcP. Cellular PAcP can down-regulate prostate cancer cell growth, at least partially by dephosphorylating c-ErbB-2/neu. Therefore, decreased cellular PAcP expression in cancer cells may be involved in prostate cancer progression.

Prenatal exposure to low doses of bisphenol A alters the periductal stroma and glandular cell function in the rat ventral prostate.

Environmental estrogens (xenoestrogens) are chemicals that bind to estrogen receptor, mimic estrogenic actions, and may have adverse effects on both human and wildlife health. Bisphenol A (BPA), a monomer used in the manufacture of epoxy resins and polycarbonate has estrogenic activity. In male rodents prenatal exposure to BPA resulted in modifications at the genital tract level. Our objective was to examine the effects of in utero exposure to low, environmentally relevant levels, of the xenoestrogen BPA on proliferation and differentiation of epithelial and stromal cells on the prepubertal rat ventral prostate. To characterize the periductal stromal cells phenotype the expression of vimentin and smooth muscle alpha-actin was evaluated. Androgen receptor (AR) and prostatic acid phosphatase (PAP) expression were also evaluated in epithelial and stromal compartments. Prenatal exposure to BPA increases the fibroblastic:smooth muscle cells ratio and decreases the number of AR-positive cells of periductal stroma of the ventral prostate. In contrast, no differences in AR expression were observed in epithelial cells between control and BPA-treated groups. No changes in proliferation patterns were observed in epithelial and stromal compartments; however, the expression of PAP was diminished in prostate ductal secretory cells of rats in utero exposed to BPA. Our results suggest that prenatal exposure to BPA altered the differentiation pattern of periductal stromal cells of the ventral prostate. These findings are significant in light of the data on human prostate cancers where alterations in the stroma compartment may enhance the invasive and/or malignant potential of the nascent tumor.

INDUCTION OF TUMOR SPECIFIC CYTOTOXIC T LYMPHOCYTES IN PROSTATE CANCER USING PROSTATIC ACID PHOSPHATASE DERIVED HLA-A2402 BINDING PEPTIDE

Human prostatic acid phosphatase is a prostate specific differentiation antigen. Prostatic acid phosphatase levels increase in the serum of patients with prostate cancer and its peptide from positions 299 to 307 (PAP 299-307) is recognized by HLA-A2 restricted cytotoxic T lymphocytes. We investigated whether HLA-A2402 binding prostatic acid phosphatase derived peptides induce HLA-A2402 restricted, tumor specific cytotoxic T lymphocytes from the peripheral blood mononuclear cells of patients with prostate cancer. Peptide binding activity was measured with RMA-S-A*A2402 cell lines and flow cytometry. Cytotoxic T-lymphocyte activity of the peripheral blood mononuclear cells of patients with prostate cancer and healthy donors was measured by interferon-gamma and (51)creatinine release assays. Prostatic acid phosphatase expression in the tumor cell lines at the messenger RNA and protein levels was investigated by reverse transcriptase-polymerase chain reaction and immunohistochemical analysis, respectively. An HLA-A2402 binding, prostatic acid phosphatase derived peptide consisting of the prostatic acid phosphatase amino acid sequence from positions 213 to 221 (PAP 213-221, LYCESVHNF) showed the ability to induce HLA-A2402 restricted and tumor specific cytotoxic T lymphocytes, which are cytoxic to prostatic acid phosphatase positive tumor cells from the peripheral blood mononuclear cells of patients with prostate cancer. PAP 213-221 may be appropriate as a cancer vaccine for specific immunotherapy in patients with HLA-A2402 positive prostate cancer.

Identification of proteins in human prostate tumor material by two-dimensional gel electrophoresis and mass spectrometry.

Protein patterns in cells collected from benign prostatic tissues and prostate carcinomas were analyzed using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry. Polypeptide expression was evaluated by computer-assisted image analysis (PDQUEST). Proteins expressed by prostate tumors were identified via in-gel digestion and subsequent matrix-assisted laser desorption/ionization mass spectrometry. In addition to cytoskeletal and mitochondrial proteins, a 40-kDa protein was identified as prostatic acid phosphatase (PAP). PAP expression decreased approximately twofold between benign and malignant tissue. Increased expression of heat shock protein 70 and decreased expression of tropomyosin 1 were also observed in the malignant tissue. The analysis of prostate material by two-dimensional gel electrophoresis and mass spectrometry shows that particular proteins are of interest as markers of disease.

Characterization of a Prostate-specific Tyrosine Phosphatase by Mutagenesis and Expression in Human Prostate Cancer Cells

The cellular form of human prostatic acid phosphatase (PAcP) is a neutral protein-tyrosine phosphatase (PTP) and may play a key role in regulating the growth and androgen responsiveness of prostate cancer cells. The functional role of the enzyme is at least due in part to its dephosphorylation of c-ErbB-2, an in vivo substrate of the enzyme. In this study, we investigated the molecular mechanism of phosphotyrosine dephosphorylation by cellular PAcP. We mutated several amino acid residues including one cysteine residue that was proposed to be involved in the PTP activity of the enzyme by serving as the phosphate acceptor. The cDNA constructs of mutant enzymes were transiently transfected into C-81 LNCaP and PC-3 human prostate cancer cells that lack the endogenous PAcP expression. The phosphotyrosine level of ErbB-2 in these transfected cells was subsequently analyzed. Our results demonstrated that the phosphotyrosine level of ErbB-2 in cells expressing H12A or D258A mutant PAcP is similar to that in control cells without PAcP expression, suggesting that these mutants are incapable of dephosphorylating ErbB-2. In contrast, cells expressing C183A, C281A, or wild-type PAcP had a decreased phosphotyrosine level of ErbB-2, compared with the control cells. Similar results were obtained from in vitro dephosphorylation of immunoprecipitated ErbB-2 by these mutant enzymes. Furthermore, transient expression of C183A, C281A, or the wild-type enzyme, but not H12A or D258A, decreased the growth rate of C-81 LNCaP cells. The data collectively indicate that His-12 and Asp-258, but not Cys-183 or Cys-281, are required for the PTP activity of PAcP.

Isolation and characterization of propagable cell lines (HUNC) from the androgen-sensitive Dunning R3327H rat prostatic adenocarcinoma.

The Dunning H rat prostate tumor (R3327H) is a widely used experimental model of human prostatic adenocarcinoma (CaP). The Dunning H tumor has been characterized as androgen-sensitive, androgen-receptor (AR) positive, prostate-specific antigen and prostatic acid phosphatase (PAP) positive. To date, the tumor has been maintained by serial passage in vivo because of the lack of an in vitro cell line that retains the characteristics of the in vivo tumor. The objective of the present study was to establish a propagable cell line from R3327H adenocarcinoma that maintained androgen sensitivity and expression of AR, PSA and PAP. Tissue harvested from an in vivo R3327H tumor was dissociated with collagenase and placed into Richter's improved media (with supplements). A cytokeratin-positive epithelial cell line (HUNC-E) and a vimentin-positive stromal cell line (HUNC-S) were generated from the primary culture, subcultured continuously for >300 days, and passaged >50 times. Survival of the HUNC-E cell line in vitro depended on several media supplements, including nicotinamide, insulin, transferrin, selenium and epidermal growth factor (EGF). HUNC-E cells expressed AR and produced PSA and PAP throughout the culture period, as confirmed by immunocytochemistry and Western blot analyses. Addition of 14 nM testosterone (T) or dihydrotestosterone (DHT) to HUNC-E cells, stimulated DNA synthesis as well as anchorage-independent growth and PSA production, which demonstrated the androgen-sensitive nature of the cells in vitro. When HUNC-E and HUNC-S cells were combined in a 3:1 ratio and introduced subcutaneously into syngeneic male hosts, tumors formed in 2/3 animals with an average latency of 7 months. RT-PCR and immunocytochemical characterization of the HUNC cell lines revealed that the cells expressed several growth factors and their cognate receptors, including HGF, TGF-alpha and the TGF-betas, indicating the establishment of potential autocrine loops in the neoplastic cells. The HUNC-E and HUNC-S CaP cell lines, which retain the characteristics of the epithelial and stromal components of the in vivo R3327H tumor, will allow a more thorough and informative molecular and biological analysis of prostatic adenocarcinoma.

Cloning and Analysis of the Promoter Activity of the Human Prostatic Acid Phosphatase Gene

Human prostatic acid phosphatase (PAP) has been proposed to be a prostate-epithelium differentiation antigen and its expression can be regulated by androgen. Nevertheless, the regulatory mechanism at the molecular level is not completely understood. In this communication, we demonstrated the tissue-specific expression of PAP in the normal prostate epithelium. Furthermore, results of nuclear run-on experiments indicated that androgen could regulate the transcriptional rate of the PAP gene. This mode of regulation was modulated by cell density. To investigate the transcriptional regulation, we cloned and characterized a 1.4- kilobase (kb) fragment of DNA that flanks the 5′ region of the PAP gene from LNCaP human prostate carcinoma cells. The results demonstrated that this 1.4-kb DNA fragment can drive a chloramphenicol acetyltransferase (CAT) gene expression in LNCaP cells. Also, the promoter activity was inversely correlated with the growth of those cells.

Expression of Human Prostatic Acid Phosphatase Correlates with Androgen-stimulated Cell Proliferation in Prostate Cancer Cell Lines

Androgen plays a critical role in regulating the growth and differentiation of normal prostate epithelia, as well as the initial growth of prostate cancer cells. Nevertheless, prostate carcinomas eventually become androgen-unresponsive, and the cancer is refractory to hormonal therapy. To gain insight into the mechanism involved in this hormone-refractory phenomenon, we have examined the potential role of the androgen receptor (AR) in that process. We have investigated the expression of AR and two prostate-specific androgen-responsive antigens, prostatic acid phosphatase (PAcP) and prostate-specific antigen (PSA), for the functional activity of AR in LNCaP and PC-3 human prostate carcinoma cells. Our results are as follows. (i) Clone 33 LNCaP cells express AR, PAcP, and PSA, and cell growth is stimulated by 5alpha-dihydrotestosterone (DHT). Stimulation of cell growth correlates with decreased cellular PAcP activity. (ii) In clone 81 LNCaP cells, the expression of PAcP decreases with a concurrent decrease in the degree of androgen stimulation of cell growth, whereas the expression of PSA mRNA level is up-regulated by DHT, as in clone 33 cells. Conversely, in PAcP cDNA-transfected clone 81 cells, an additional expression of cellular PAcP correlates with an increased stimulation by androgen, higher than the corresponding control cells. (iii) PC-3 cells express a low level of functional AR with no detectable PAcP or PSA, and the growth of PC-3 cells is not affected by DHT treatment. Nevertheless, in two PAcP cDNA-transfected PC-3 sublines, the expression of exogenous cellular PAcP correlates with androgen stimulation. This androgen stimulation of cell growth concurs with an increased tyrosine phosphorylation of a phosphoprotein of 185 kDa. In summary, the data indicate that the expression of AR alone is not sufficient for androgen stimulation of cell growth. Furthermore, in AR-expressing prostate cancer cells, the expression of cellular PAcP correlates with androgen stimulation of cell proliferation.

Ductal carcinomas of the prostate: a clinicopathological and immunohistochemical study.

To confirm the expression of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) in ductal carcinomas of the prostate, and to analyse p53, Ki67, oestrogen (ER) and androgen (AR) receptors in these tumours. Paraffin-embedded samples from 12 patients with ductal carcinoma of the prostate were assessed for pattern, mitotic count and the presence of a microacinar carcinoma component. There were six pure ductal and six mixed microacinar and ductal carcinomas. Sections were stained immunohistochemically for the expression of PSA, PAP, Ki67, p53, AR and ER. Clinical data were obtained from case notes. Six of the ductal tumours had a papillary pattern whilst the others had a cribriform appearance. The mitotic rates in the ductal areas were high in the tumours from eight of the 12 patients. PSA and PAP immunohistochemistry were positive in all the cases. No ER immunoreactivity was found in any of the patients. Ten of the ductal tumours showed strong reactivity with AR, the other two were weakly positive; two of the tumours were strongly positive for p53 protein. All the ductal carcinomas expressed Ki67, three having > 25% nuclear marking. One patient who was strongly positive for p53 and had a high Ki67 score survived only one year after diagnosis. Survival ranged from 1 to 13 years after diagnosis. This study confirms the expression of PSA and PAP in ductal carcinomas of the prostate. The percentage of tumours expressing p53 was similar to that published for high-grade microacinar carcinomas. The results for Ki67 suggest that ductal tumours have higher scores than microacinar tumours, but further studies are required to ascertain if this is significantly different. As half the patients with ductal tumours had co-existent microacinar tumours, we advise transrectal prostatic biopsies in patients diagnosed with pure ductal carcinomas on transurethral resection specimens, to exclude high-grade microacinar carcinomas. The presence of AR and the lack of ER in all the ductal carcinomas confirms that these tumours are prostatic in origin and should be treated with antiandrogen therapy.

LNCaP prostatic adenocarcinoma cells derived from low and high passage numbers display divergent responses not only to androgens but also to retinoids

In the present paper, two strains of LNCaP cells derived from the same source (American Type Culture Collection), but studied either at a low passage number (LP) or at a high passage number (HP), were compared in their response to R1881 (a synthetic androgen), all-trans-retinoic acid (atRA), and 1alpha,25-dihydroxycholecalciferol (VD3). [3H]Thymidine incorporation and epidermal growth factor receptor (EGF-R) binding were measured as parameters related to the proliferative response of the cells. The secretion of prostate-specific antigen (PSA) and the mRNA expression of PSA, prostatic acid phosphatase (PAP), and diazepam-binding inhibitor (DBI) were used as parameters reflecting differentiated function. Marked differences were noted in the response of LP and HP cells to androgens. [3H]Thymidine incorporation displayed a bell-shaped dose-response curve in both strains. The amplitude of the response, however, was much higher in HP cells and growth inhibition at high levels of R1881 was only observed in LP cells. On the contrary, androgen induction of PSA secretion and PSA mRNA expression, as well as the expression of PAP was much more pronounced in LP cells, whereas DBI expression was not altered according to passage number. LP cells and HP cells also displayed striking differences in their response to atRA. An up to 6-fold stimulation of [3H]thymidine incorporation was observed in LP cells, whereas in HP cells the only significant effect was growth inhibition. VD3, on the contrary, inhibited [3H]thymidine incorporation to a comparable degree in LP and HP cells. Only marginal effects of atRA and VD3 were observed on PSA secretion. In both LP and HP cells EGF-R levels were increased by androgens and to a slight extent also by atRA and VD3. It is concluded that LP and HP LNCaP cells display markedly divergent responses not only to androgens but also to atRA. The proliferative rather than antiproliferative effects of atRA in some strains of LNCaP should caution against the uncontrolled use of these agents, or of drugs affecting their metabolism, in patients with prostate cancer.

Characterization of residual tumor cells following radical radiation therapy for prostatic adenocarcinoma; immunohistochemical expression of prostate-specific antigen, prostatic acid phosphatase, and cytokeratin 8.

Our knowledge about the nature and biological activity of tumor cells residing in the prostate gland after radical radiotherapy (RRT) is limited. In the present study, residual tumor in core biopsies taken from 37 patients after an average of 6.8 years follow-up after radiation, were investigated with immunohistochemistry for the biochemical markers prostate-specific antigen (PSA), prostatic acid phosphatase (PAP), and the epithelial marker, cytokeratin 8 (CK8). Tumor cells were cytokeratin-positive in 33 of 34 evaluable specimens (97%). PSA and PAP were expressed in the tumor cells in 94% (34/36) and 81% (30/37) of cases, respectively. No significant correlation was observed between PSA/PAP expression and tumor grade after treatment. Endocrine treatment administered in addition to RRT in 12 of the 37 patients did not affect the expression of PSA or PAP. The expression of both biochemical markers was reduced after radiotherapy in 10 of the 12 cases for which pre- and post-treatment specimens were available. Tumor cells retain their epithelial characteristics immunohistochemically after radiation, though their morphology sometimes suggests an altered phenotype after treatment. PSA and PAP reactivity was demonstrated in tumor cells nearly 7 years after radiotherapy, which indicates that these cells maintain their biochemical integrity and protein synthesis to a certain extent. Furthermore, endocrine treatment did not abolish PSA or PAP expression in the tumor cells. Whether PSA and PAP immunoexpression provides independent prognostic information needs to be further investigated.

Characterization of residual tumor cells following radical radiation therapy for prostatic adenocarcinoma; Immunohistochemical expression of prostate‐specific antigen, prostatic acid phosphatase, and cytokeratin 8

BACKGROUND Our knowledge about the nature and biological activity of tumor cells residing in the prostate gland after radical radiotherapy (RRT) is limited. METHODS In the present study, residual tumor in core biopsies taken from 37 patients after an average of 6.8 years follow-up after radiation, were investigated with immunohistochemistry for the biochemical markers prostate-specific antigen (PSA), prostatic acid phosphatase (PAP), and the epithelial marker, cytokeratin 8 (CK8). RESULTS Tumor cells were cytokeratin-positive in 33 of 34 evaluable specimens (97%). PSA and PAP were expressed in the tumor cells in 94% (34/36) and 81% (30/37) of cases, respectively. No significant correlation was observed between PSA/PAP expression and tumor grade after treatment. Endocrine treatment administered in addition to RRT in 12 of the 37 patients did not affect the expression of PSA or PAP. The expression of both biochemical markers was reduced after radiotherapy in 10 of the 12 cases for which pre- and post-treatment specimens were available. CONCLUSIONS Tumor cells retain their epithelial characteristics immunohistochemically after radiation, though their morphology sometimes suggests an altered phenotype after treatment. PSA and PAP reactivity was demonstrated in tumor cells nearly 7 years after radiotherapy, which indicates that these cells maintain their biochemical integrity and protein synthesis to a certain extent. Furthermore, endocrine treatment did not abolish PSA or PAP expression in the tumor cells. Whether PSA and PAP immunoexpression provides independent prognostic information needs to be further investigated. Prostate 31:91–97, 1997. © 1997 Wiley-Liss, Inc.

Tyrosine Phosphorylation of a 185 kDa Phosphoprotein (pp185) Inversely Correlates with the Cellular Activity of Human Prostatic Acid Phosphatase

Human prostatic acid phosphatase (PAcP), a prostate epithelium-specific differentiation antigen, was determined to exhibit the endogenous protein tyrosine phosphatase activity. We investigated the phosphoprotein(s) that might be dephosphorylated by PAcP in human prostate carcinoma cells. Several lines of evidence were presented to show that the tyrosine phosphorylation level of a 185 kDa phosphoprotein (pp185) is negatively correlated with the cellular activity of PAcP. (i) In DU145, PC-3 and high passaged LNCaP prostate carcinoma cells that have no or low PAcP expression, the phosphotyrosine (p-tyr) level of pp185 was higher than that in low passaged LNCaP cells that express an endogenous PAcP. (ii) In LNCaP cells grown in the presence of L(+)-tartrate, an inhibitor of PAcP, the tyrosine phosphorylation of pp185 was increased. (iii) Mediated by Lipofectin, a cationic liposome, the incorporation of purified PAcP protein into DU145 cells resulted in the decreased phosphorylation of pp185. Thus, the results taken collectively demonstrated that the p-tyr level of pp185 is inversely correlated with the cellular activity of PAcP and indicated that the pp185 may be a putative substrate of PAcP in prostate carcinoma cells.

The expression of prostatic acid phosphatase is transcriptionally regulated in human prostate carcinoma cells

The expression of prostatic acid phosphatase (PAcP) in three human prostate carcinoma cell lines including LNCaP, DU 145 and PC-3, was studied to explore its potential role as a marker in the progression of prostate cancer. Although Southern blot analysis suggested the presence of PAcP gene in all three prostate carcinoma cell lines, the Northern blot analysis and the reverse transcriptase-polymerase chain reaction (RT-PCR) assay showed that PAcP mRNA can be detected only in LNCaP cells. As one of the major differences between LNCaP cells and PC-3 as well as DU 145 cells is the androgen-sensitivity of LNCaP cells, we then focused on the influence of PAcP expression by the presence of androgen receptor (AR) in hman AR cDNA-transfected PC-3 cells and high passages of LNCaP cells. The results demonstrated that the transfection of human AR cDNA into PC-3 cells did not have any detectable effect on the expression of PAcP. Further, in LNCaP cells, while the level of PAcP mRNA diminished upon passage, the AR mRNA level remained approximately the same. Together, these data suggested that the differential expression of PAcP in different prostate carcinoma cells including high passages of LNCaP cells may occur at the transcriptional level and may have little linkage to the expression of AR.