Neoplastic Prostate Tissue Research Articles

Characterization of the cell-specific expression of parathyroid hormone–related protein in normal and neoplastic prostate tissue

Objectives. Parathyroid hormone–related protein (PTHrP) is a primary factor in the pathogenesis of malignancy-associated hypercalcemia. By alternative splicing, the human PTHrP gene can generate three different species of mRNA that encode three initial translational isoforms of 139, 173, and 141 amino acids. We recently reported that PTHrP was present in normal prostatic neuroendocrine cells and was overexpressed in prostate cancer tissue as demonstrated by immunostaining. This study was undertaken to further clarify the complex expression of PTHrP gene in normal prostate tissue and prostate cancer. Methods. PTHrP mRNA in samples prepared from normal prostate tissue, prostate cancer, and three prostate cancer cell lines, PC3, LNCaP, and DU145 was assessed using Northern hybridization. Expressed PTHrP isoforms were deduced from differential reverse transcription-polymerase chain reaction (RT-PCR) assays with exon-specific primers. Further localization of different species of PTHrP mRNA was performed using nonradioactive in situ hybridization with exon-specific probes on consecutive sections of normal and neoplastic prostate tissue. Results. Northern hybridization showed that the PTHrP expression level was higher in prostate cancer than in normal prostate tissue. All three PTHrP isoforms could be detected in normal prostate tissues and prostate cancer with differential RT-PCR. Further analysis using in situ hybridization with exon-specific probes revealed that all three PTHrP isoforms were present in prostatic neuroendocrine cells and only PTHrP-1–139 isoform could be clearly detected in prostate cancer tissue. Two androgen-insensitive cell lines, PC3 and DU145, derived from a bone metastasis and a brain metastasis, respectively, expressed all three mRNA species encoding for the three isoforms, but DU145 cells expressed less than PC3 cells. Androgen-sensitive LNCaP cells exhibited a low level of expression of mRNA species encoding for PTHrP-1–139 and PTHrP-1–173, and no expression of PTHrP1-141 isoform. Conclusions. All three initial translational isoforms of PTHrP are produced by prostatic neuroendocrine cells. The mature products of PTHrP might exert their effects on other prostatic epithelial cells in a paracrine fashion and also participate in the homeostatic regulation of the ejaculate. In prostate cancer, differential expression of these three isoforms is evident and PTHrP-1–139 isoform is more abundant than the other two forms. These findings are valuable for designing future research studies to further elucidate the biological functions of PTHrP in normal prostatic glands and prostate cancer.

DIFFERENTIAL EXPRESSION OF INSULIN-LIKE GROWTH FACTOR BINDING PROTEINS IN HIGH VERSUS LOW GLEASON SCORE PROSTATE CANCER

Purpose The insulin-like growth factor (IGF) system appears to be important in human prostate cancer biology. Expression of specific IGF binding proteins (IGFBPs) by prostate cancer tissues may modulate IGF cellular actions, and possibly determine both IGF-dependent tumor growth and biological aggressiveness in vivo. The purpose of this study was to examine the differential expression of all six IGFBP genes in benign and malignant prostate tissue samples. Materials and Methods Using RNAse protection assays, we examined expression of IGFBPs 1 through 6 in 23 paired benign and neoplastic prostate tissue samples obtained from the same prostatectomy specimen. RNA expression levels on each tissue sample were determined densitometrically and groups compared using standard Student's t test. Results We found expression of IGFBPs 2 through 6, but not IGFBP-1, in both malignant and benign tissues. A statistically significant differential expression of IGFBPs 2, 3 and 5 was found between tumors with high Gleason score and those with low scores and benign tissues. Expression of IGFBPs 2 and 5 was higher (p = 0.002 and 0.04, respectively) while that of IGFBP-3 was lower (p = 0.05) in high versus low Gleason score cancer specimens. Expression of IGFBPs 4 and 6 was no different between tumors (p = 0.052 and 0.25, respectively). No significant differences in IGFBP expression were evident between benign and tumor tissues when tumor grade was not considered. Conclusion Our results indicate that differential expression of certain IGFBPs in human prostate cancer correlates with tumor Gleason score. Thus, expression of certain IGFBPs in prostate cancer may be used as a surrogate marker of aggressive clinical behavior.

Expression of Granulocyte-Macrophage Colony-Stimulating Factor Receptors in Human Prostate Cancer

We studied the expression and function of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor in the human prostate carcinoma cell line LNCaP and looked for its presence in normal and neoplastic human prostatic tissue. The GM-CSF receptor is composed of two subunits, alpha and beta. While the isolated alpha subunit binds GM-CSF at low-affinity, the isolated beta subunit does not bind GM-CSF by itself; but complexes with the alpha subunit to form a high-affinity receptor. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) showed expression of mRNAs encoding the alpha and beta subunits of the GM-CSF receptor in LNCaP cells, and the presence of the alpha and beta proteins was confirmed by immunolocalization with anti-alpha and anti-beta antibodies. Receptor binding studies using radiolabeled GM-CSF showed that LNCaP cells have about 150 high-affinity sites with a kd of 40 pmol/L and approximately 750 low-affinity sites with a kd of 2 nmol/L. GM-CSF signaled, in a time- and dose-dependent manner, for protein tyrosine phosphorylation and induced the proliferation of the LNCaP cells. Immunolocalization studies showed low level expression of GM-CSF alpha and beta subunits in normal prostate tissue, with substantial expression in benign prostatic hyperplasia and prominent expression in neoplastic prostate tissue. Maximal expression of both subunits was observed in prostatic carcinomas metastatic to lymph node and bone. Tumor cells that stained positively with anti-alpha subunit antibodies were also reactive with anti-beta subunit antibodies, indicating that they express high-affinity GM-CSF receptors. Our data show that the LNCaP cells express functional GM-CSF receptors and that prostatic carcinomas have prominent GM-CSF receptor expression. These findings imply that both hyperplastic and neoplastic prostatic tissues may be responsive to GM-CSF.

Expression of Granulocyte-Macrophage Colony-Stimulating Factor Receptors in Human Prostate Cancer

AbstractWe studied the expression and function of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor in the human prostate carcinoma cell line LNCaP and looked for its presence in normal and neoplastic human prostatic tissue. The GM-CSF receptor is composed of two subunits, α and β. While the isolated α subunit binds GM-CSF at low-affinity, the isolated β subunit does not bind GM-CSF by itself; but complexes with the α subunit to form a high-affinity receptor. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) showed expression of mRNAs encoding the α and β subunits of the GM-CSF receptor in LNCaP cells, and the presence of the α and β proteins was confirmed by immunolocalization with anti-α and anti-β antibodies. Receptor binding studies using radiolabeled GM-CSF showed that LNCaP cells have about 150 high-affinity sites with a kd of 40 pmol/L and approximately 750 low-affinity sites with a kd of 2 nmol/L. GM-CSF signaled, in a time- and dose-dependent manner, for protein tyrosine phosphorylation and induced the proliferation of the LNCaP cells. Immunolocalization studies showed low level expression of GM-CSF α and β subunits in normal prostate tissue, with substantial expression in benign prostatic hyperplasia and prominent expression in neoplastic prostate tissue. Maximal expression of both subunits was observed in prostatic carcinomas metastatic to lymph node and bone. Tumor cells that stained positively with anti-α subunit antibodies were also reactive with anti-β subunit antibodies, indicating that they express high-affinity GM-CSF receptors. Our data show that the LNCaP cells express functional GM-CSF receptors and that prostatic carcinomas have prominent GM-CSF receptor expression. These findings imply that both hyperplastic and neoplastic prostatic tissues may be responsive to GM-CSF.

Neuroendocrine cells in benign and malignant prostate tissue: Morphogenesis, proliferation, and androgen receptor status

The presence of neuroendocrine (NE) differentiation in benign and neoplastic prostate tissue has attracted increasing attention in contemporary prostate cancer research. The present review focuses on the proliferation and androgen receptor (AR) status of NE phenotypes and their morphogenetic origin in benign and malignant prostate tissue. Recent data have documented phenotype relation between NE cells and other cell lineages in benign and malignant prostate tissue indicating their common origin. NE cell types (as defined by the most commonly used endocrine marker, chromogranin A) do not show evidence of cell proliferation and consistently lack the nuclear AR in both benign and malignant conditions. Prostatic NE cells most likely derive from local stem cells and represent terminally differentiated and androgen-insensitive cell populations in benign prostate tissue. The frequent occurrence of NE differentiation in prostatic adenocarcinoma obviously reflects the differentiation repertoire of its stem cells. Neoplastic NE cells devoid of nuclear AR constitute an androgen-insensitive cell population in prostate cancer. Furthermore, the absence of proliferation activity may endow NE tumor cells with relative resistance toward cytotoxic drugs and radiation therapy.

Distribution of WAF1 (p21<sup>WAF1</sup>) in Normal and Neoplastic Prostate Tissue

Distribution of WAF1 (p21<sup>WAF1</sup>) in Normal and Neoplastic Prostate Tissue

Can Androgen Deprivation With Leuprolide be Predicted From Histology Alone? If Not, Why Not?

Purpose Androgen deprivation therapy with analogues of luteinizing hormone-releasing hormone produces distinctive histological changes in neoplastic and nonneoplastic prostate tissue. Others have described these features in cases in which treatment status was known. To our knowledge the specificity and sensitivity of luteinizing hormone-releasing hormone effects based only on histology and possible reasons for interobserver variation have not been addressed previously. Materials and Methods Slides from 97 prostatectomies performed in a 3-year period were reviewed by 2 observers blinded to knowledge of previous hormonal treatment. The observers evaluated each case, recording the presence or absence of 14 features associated with androgen deprivation therapy, and then made an overall assessment regarding treatment status. Results Of the 97 patients 31 had received androgen deprivation therapy with the luteinizing hormone-releasing hormone agonist leuprolide. A luteinizing hormone-releasing hormone effect was identified by the 2 observers in 26 and 28, respectively, of the 3 cases (83.9 versus 90.3% sensitivity and 92.4 versus 80.3% specificity). Including focal changes as consistent with androgen deprivation therapy increased sensitivity but decreased specificity. Of the 14 features 12 had a significant association for predicting treatment status. Conclusions Interobserver variations in interpretation occurred although both examiners were experienced in the evaluation of luteinizing hormone-releasing hormone effects and they used exactly the same criteria. These variations were apparently due to differences in the value (mental weight) given by each observer to the features assessed in each case. Predicting treatment status was optimized by noting a luteinizing hormone-releasing hormone effect only when changes were diffuse, improving specificity significantly with only a modest decrease in sensitivity.

The fibrinolytic system in neoplasia.

During activation of the fibrinolytic system plasminogen is converted to plasmin by tissue plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA). t-PA is predominantly released from endothelial cells, u-PA primarily by renal parenchymal cells. The activation of plasminogen is regulated by plasminogen activator inhibitor-1 (PAI-1), plasmin is controlled by alpha 2-plasmin inhibitor. The fibrinolytic system is not only involved in the intravascular dissolution of fibrin (thrombi), it also plays a vital role in normal physiologic reproduction, wound repair, angiogenesis, and tissue remodeling. Fibrinolysis is also a vital component in the pathogenesis of neoplastic disease. It is essential in releasing cells from their primary site of origin, providing nutrition for neoplastic cell growth and promoting cell mobility and motility. In neoplastic cells the degradation of the extracellular matrix proteins is facilitated by excessive expression of u-PA, t-PA, and u-PAR. In many forms of carcinoma increased expression of u-PAR and u-PA is associated with significantly shorter survival. Greater expression of u-PA in breast cancer cells, for example, is associated with shorter survival and increased relapse rate. Progressively aggressive neoplastic cells evidence high expression of u-PA and u-PAR activities, variable expression of t-PA, and enhanced PAI-1 and PAI-2 activities. In acute nonlymphocytic leukemias, poor outcome correlates with high t-PA levels. In acute progranulocytic leukemia there is a high incidence of DIC. Neoplastic prostatic tissue also expresses high u-PA activity and the more aggressive the cell line, the greater the number of u-PAR and the higher the u-PA activity. In gynecologic malignancies, a greater expression of u-PA in combination with cathepsin D is associated with widespread disease and poor prognosis. High u-PA values were also seen in patients with brain, gastric, and hepatic malignancies. It is evident that the plasminogen-plasmin system is a vital component in the biology of neoplastic disease and that it is, in theses conditions, in no way beneficial to the host.

Differential histochemical peanut agglutinin stain in benign and malignant human prostate tumors: Relationship with prostatic specific antigen immunostain and nuclear DNA content

The histochemical binding pattern of the peanut ( Arachis hypogaea) lectin (PNA) was quantitatively described by means of computer-assisted microscope analysis in 28 benign prostatic hyperplasias (BPH), 15 prostatic intraepithelial neoplasias (PIN), and 119 prostatic adenocarcinomas. PNA exhibits noninunune but selective binding to glycoproteins with β-D-galactosyl(1,3)-N-acetyl-D-galactosamine residues. We also investigated whether a relationship existed between the number of histochemical-related PNA acceptors and the histochemical prostate-specific antigen (PSA) stain intensity, and between the number of PNA receptors and DNA ploidy level. The results show that neoplastic prostate tissues and high-grade intraepithelial prostatic neoplasias (PIN2_3) exhibit a significantly higher number of PNA acceptors than benign prostatic hyperplasias and low (PIN1) grade prostatic intraepithelial neoplasias. A statistically significant correlation was observed between the number of histochemically related PNA acceptors and PSA immunostain intensity. Lastly, diploid prostatic tumors, whether benign or malignant, exhibited a significantly higher number of PNA acceptors than aneuploid ones. These results suggest that PNA acceptors play an important role in the biology of prostate tumors.

Effects of neoadjuvant androgen deprivation therapy on prostatic cancer.

In this study, we analyzed the involutive effects of androgen deprivation therapy on normal and neoplastic prostatic tissue, to investigate whether androgen deprivation prior to radical prostatectomy could reduce the incidence of extracapsular extension, positive margins, positive seminal vesicles and positive lymph nodes in patients with prostatic carcinoma. We performed neoadjuvant androgen deprivation therapy (NADT) in 41 patients cT2N0M0 and in 21 patients cT3N0M0. Criteria to evaluate the effectiveness of NADT included prostate volume, tumor volume, serum prostate-specific antigen (PSA), staging, grading, histological modifications of the tumor, and evaluation of indices of cellular proliferation. We observed a decrease in prostate and tumor volume, as well as serum PSA; a down-staging effect was observed in 14.51% of cases. Evaluation of proliferating-cell nuclear antigen (PCNA) revealed a decrease of proliferative activity in treated prostatic carcinoma. The histological modifications after neoadjuvant therapy consisted of cellular necrosis with apoptotic phenomena, dense chromatin without nucleoli, absence of mitosis, inflammatory infiltrate, and interstitial fibrosis. Regressive aspects similar to those of neoplastic cells were observed in prostatic intraepithelial neoplasia. Our assessment of the biologic effects of NADT on tumoral activity of prostatic carcinoma led us to conclude that NADT can reduce the cellular proliferation of neoplastic cells.

Localization and Physical Mapping of the Prostate-Specific Membrane Antigen (PSM) Gene to Human Chromosome 11

The prostate-specific membrane antigen (PSM) was identified by the monoclonal antibody 7E11-C5.3, which was raised against the human prostatic carcinoma cell line LNCaP (3). The PSM antigen is expressed by normal, neoplastic, and metastatic prostatic tissues. The 2.65-kb cDNA encoding the 100-kDa PSM glycoprotein was cloned from LNCaP cells (4). Studies have shown that the expression of PSM is tissue-specific (5). In the present study monochromosomal somatic cell hybrids were used to localize the PSM gene to human chromosome 11. Using this information, initial mapping studies identified two potential PSM gene loci at 11p11.1–p13 and 11q14. Further high-stringency analysis using cosmid probes identified the 11q14 region as the location of the PSM gene.

Epidermal growth factor-related peptides and the epidermal growth factor receptor in normal and malignant prostate.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) are two closely related peptides that interact with cell-surface epidermal growth factor receptors (EGFR) to induce receptor tyrosine phosphorylation and activation of intracellular signal-transduction pathways. EGF appears to be the predominant EGF-related growth factor in the normal prostate and in benign prostatic hyperplasia (BPH). Evidence indicates that EGF and TGF alpha are important for maintainence of the structural and functional integrity of the benign prostatic epithelium. The EGF-related peptides are primarily localized to the secretory epithelium of the benign prostate, and their production and secretion is augmented by the presence of circulating androgens. EGFR are located in the basal/neuroendocrine (NE) compartment of the benign prostate and exhibit relatively androgen-independent expression. The EGF-related peptides and EGFR are also present in neoplastic prostatic tissues. There is currently no direct evidence to implicate EGFR activation in the pathogenesis of BPH. However, the EGF-related peptides appear to play a functional role in the growth of prostatic carcinoma cells, with TGF alpha being the predominant growth factor. Numerous investigators have demonstrated the functional significance of a TGF alpha/EGFR-mediated autocrine growth pathway in cultured prostatic carcinoma cells. Studies of cultured prostate cancer cells, but not normal epithelial cells, demonstrate constitutive activation of EGFR. Androgen-independent cancer cells exhibit more EGFR expression and phosphorylation than do androgen-responsive prostate cancer cells. Most studies indicate that EGFR do not play a functional role in androgen-stimulated growth of prostate cancer cells. Several studies have correlated EGFR expression with increased nuclear size and tumor dedifferentiation. Future studies should focus on determining both the prognostic significance of EGFR expression and whether manipulation of EGFR-mediated growth can be exploited for therapeutic benefit in human prostate cancer.

Pathology of androgen deprivation therapy in prostate carcinoma. A comparative study of 173 patients.

Leuprolide, an agonist of luteinizing hormone-releasing hormone (LH-RH), and flutamide, an antiandrogen, increasingly are being used in the treatment of clinically localized prostate cancer. Only two small series (of 23 and 12 patients) have been published on the distinctive pathologic changes induced in the prostate by androgen deprivation therapy with discrepancies on the presence of squamous metaplasia, necrosis, and possible tumor destruction by combined androgen deprivation therapy.One hundred and thirteen radical prostatectomy specimens obtained after at least 3 months of leuprolide-flutamide androgen inhibition therapy and 60 nonhormonally treated prostates in randomly selected clinical Stage T2 prostate adenocarcinoma patients were entirely sectioned. Distinctive histologic findings were tabulated and their statistical value determined.Resection margins of excision were involved by tumor in 43% of untreated and in 19% of androgen-deprived patients. Characteristic changes in androgen-inhibited nontumor glands included atrophy, basal cell prominence, vacuolated luminal cell layer, and squamous and transitional cell metaplasia. Prostatic intraepithelial neoplasia (PIN) was observed in 35% of treated patients. The presence of small tumor glands separated by stroma was the most frequently noted effect of androgen deprivation on prostate adenocarcinoma; pyknosis and branching empty spaces were less frequent. Large clear tumor cells within an inflammatory response was a third histologic pattern. Apparently unaltered tumor areas were observed in 43% of prostates exposed to androgen deprivation therapy.Androgen deprivation therapy results in histologically distinctive changes that can be recognized in both nonneoplastic and neoplastic prostate tissue. Residual tumor was present in all 113 treated radical prostatectomy specimens. In addition to glandular shrinkage, therapy was associated with statistically significant reductions in the frequency of high grade PIN and extension of cancer to prostate specimen margins of excisions.

Endocrine-paracrine cell types in the prostate and prostatic adenocarcinoma are postmitotic cells

Neuroendocrine (NE) differentiation frequently occurs in common prostatic malignancies and has potential prognostic and therapeutic implications. In a recent study we were able to provide immunohistochemical evidence that endocrine-paracrine cell types represent an androgen-insensitive cell population in prostate cancer, documented by the consistent lack of the pertinent receptor. In this study we investigated the proliferative activity of endocrine-paracrine cell types in normal, hyperplastic, and neoplastic prostate tissue. Using double-label techniques for the endocrine marker chromogranin A (chr A) and the proliferation-associated MIB-1 antigen, we evaluated the proliferative status of endocrine-paracrine cell types in the prostate and prostatic adenocarcinoma showing marked NE differentiation. In this series of carcinomas and in nonneoplastic tissue the proliferative activities were exclusively restricted to nonendocrine cell populations, whereas endocrine-paracrine cell types characterized by Chr A consistently lack MIB-1 immunoreactivity. This may indicate that prostatic endocrine-paracrine cell types do not participate in the cell cycle during normal, hyperplastic, and neoplastic prostatic growth. Based on the present information, the endocrine phenotype can be considered to be an androgen-insensitive, postmitotic subpopulation in the prostate and prostate cancer.

Neuroendocrine cells in the normal, hyperplastic and neoplastic prostate

Neuroendocrine cells can be demonstrated in normal, hyperplastic and neoplastic prostatic tissues. The products secreted by these cells can be used as tissue and/or serum markers but may also have biological effects. Neuroendocrine cells in prostate cancer most probably do not contain the androgen receptor and are therefore primarily androgen independent. Some of the neuropeptides secreted by the neuroendocrine cells may act as growth factor by activation of membrane receptors in an autocrine-paracrine fashion or by ligand-independent activation of the androgen receptor in neighboring non-neuroendocrine cells. Evidence is accumulating from experiments with tumor models that neuropeptides indeed can influence the growth of prostatic tumor cells. Future research on neuroendocrine differentiation may answer some questions concerning the biological behavior of clinical prostatic tumors.

Expression of bone morphogenetic protein messenger RNAs by normal rat and human prostate and prostate cancer cells

Human prostate cancer cells are known to produce several growth regulatory factors, including transforming growth factor beta (TGF beta) and heparin-binding fibroblast growth factors (FGFs), which may play as-yet-undefined roles in prostate gland morphogenesis, as well as in prostate cancer cell behavior. Recently, a family of proteins in the extended TGF beta family, the bone morphogenetic proteins (BMPs), has been identified which stimulates bone formation in vivo, and in which, the proteins are likely involved in a variety of morphogenetic processes during embryogenesis. These powerful morphogenetic factors are capable of redirecting muscle mesenchyme cells to differentiate along the lines of bone tissue. We examined a number of well-characterized rat and human prostate cancer cell lines for the expression of BMP 2, 3, 4, and 6 messenger RNA. Poly(A+)-RNA was isolated from normal human and rat ventral prostate, from the rat prostate adenocarcinoma PAIII tumor and cultured cells derived from it, and from human prostate cancer cell lines PC-3, LNCaP, and DU-145. BMP mRNA levels were measured using BMP 2, 3, 4 and Vgr-1 (BMP 6) cDNA probes. Both normal and neoplastic prostate tissue expressed these BMP mRNAs, although the level of expression varied from tumor to tumor. Normal human prostate expressed BMP 4 mRNA predominantly, as did the human prostate cancers PC-3 and DU-145. PC-3 also expressed BMP 2 mRNA and BMP 3 mRNA in large amounts. Normal rat ventral prostate expressed all these BMP mRNAs, but the rat prostate adenocarcinoma PAIII expressed predominantly BMP 3 mRNA. The reason that different BMPs are expressed in varying amounts by these normal and neoplastic cells is unknown. However, if these BMPs are expressed in biologically active form, they could be responsible for important effects on normal prostate growth and morphogenesis, on neoplastic prostate cell behavior, and could even contribute to the capacity of prostatic cancer cells to stimulate new bone formation at metastatic tumor sites in bone.

Immunohistochemical localization of chromogranins A and B and secretogranin II in normal, hyperplastic and neoplastic prostate.

Routinely processed normal, hyperplastic and neoplastic prostatic tissue was immunohistochemically investigated with antibodies against chromogranin A and B and secretogranin II. In normal and hyperplastic prostates all three peptides were immunolocalized in scattered neuroendocrine cells situated within the glandular epithelium. In 17 prostatic carcinomas with pronounced neuroendocrine differentiation and in a case of prostatic carcinoid, chromogranin B was the major component whereas chromogranin A and secretogranin II were virtually absent in poorly differentiated (grade III) tumours. Neuroendocrine differentiation in prostatic cancer is most likely to be associated with a poor clinical outcome; thus, chromogranin B appears to be a useful marker in the histopathological diagnosis of these neoplasms.

Multidirectional differentiation in the normal, hyperplastic, and neoplastic human prostate: Simultaneous demonstration of cell-specific epithelial markers

The prostatic epithelium is composed of three distinct cell populations: secretory luminal, basal, and endocrine-paracrine cells. It is currently unknown whether these basic epithelial cell types are related in a hierarchical pathway of differentiation or are independent and separate entities. In the present study we used double-label techniques for cell-specific markers to search for multidirectional differentiation in normal, hyperplastic, and neoplastic prostate tissue. In normal and hyperplastic conditions subsets of basal cells revealed synchronous expression of basal cell-specific cytokeratins and the prostate-specific antigen, indicating intermediate differentiation between basal and secretory luminal cell types. Furthermore, endocrine-paracrine cells of the closed type focally showed simultaneous expression of chromogranin A and basal cell-specific cytokeratins. These findings highlight the phenotypic plasticity of the basal cell layer in the human prostate. In prostatic adenocarcinoma co-expression of exocrine (prostate-specific antigen) and endocrine (chromogranin A) markers was detected frequently in subsets of malignant cells. Conversely, this amphicrine phenotype was rarely found in hyperplastic glands. The occurrence of multidirectional differentiation within the prostatic endocrine cell system may indicate that endocrine-paracine cells derive from pluripotent stem cells of endodermal origin. Furthermore, the phenotypic plasticity of basal cells suggests that this epithelial compartment houses stem cell populations that give rise to all epithelial cell lineages encountered in the normal, hyperplastic, and neoplastic human prostate.

PSA AND PAP AS IMMUNOHISTOCHEMICAL MARKERS IN PROSTATE CANCER

This article describes the immunoreactivity of PSA and PAP in non-neoplastic and neoplastic prostate tissue. Listed are examples of cross reactivity of PSA and PAP in non-neoplastic and neoplastic tissue from other organs. The use of PSA and PAP to identify tumors of prostatic origin in different sites is also described. Finally, the diagnostic uses of immunohistochemistry for PSA and PAP in prostate biopsies and for prognostication are discussed.

Differential expression of α6 and α2 very late antigen integrins in the normal, hyperplastic, and neoplastic prostate: Simultaneous demonstration of cell surface receptors and their extracellular ligands

The very late antigens (VLAs) are αβ-heterodimeric transmembrane proteins that include surface cell receptors for laminin (VLA-6) and collagen (VLA-2), which mediate cell-matrix and cell-cell adhesion. We investigated the distribution of VLA-6 (α6, β1) and VLA-2 (α2, β1) proteins in normal, hyperplastic, and neoplastic human prostate tissue and lymph node metastases by the avidin-biotin complex method. In normal and hyperplastic glands we observed two staining patterns that differed according to the density of α6- and α2-receptors at the site of co-expression with their corresponding ligands (laminin, type IV collagen) in acinar basement membranes (BMs). Band-like deposits with high receptor density suggested strong anchorage of the prostate epithelium to acinar BMs, whereas the absence of this pattern most probably reflected reduced cellular attachment. Very late antigen-6 immunoreactivity showed the band-like pattern in approximately 70% of normal and hyperplastic glands compared with VLA-2, which showed the same pattern in only 5% of cases. In prostatic adenocarcinoma the band-like pattern significantly decreased with dedifferentiation and was consistently absent in grade III lesions. Compared with staining intensities in normal and hyperplastic conditions, grade I and II tumors maintained or overexpressed the VLA-6 receptor in 85% of cases, whereas the VLA-2 receptor was downregulated in approximately 70% of cases. Grade III tumors were characterized by a heterogenous expression of VLA-6 and VLA-2 proteins, but frequently upregulated their receptors in corresponding lymph node metastases. Regardless of the staining intensity, all primary and metastatic carcinomas investigated expressed VLA-6 and VLA-2 receptors whose extracellular domains were extensively co-expressed with their ligands in neoplastic BM formations. These findings suggest that VLA-6 and VLA-2 receptors mediate attachment of tumor cells to neoplastic BM material, which, in turn, may endow these cells with an increased ability to invade the extracellular matrix.