DNA replication regulation protein Mcm7 as a marker of proliferation in prostate cancer

BACKGROUND: Recent studies have shown that minichromosome maintenance (MCM) proteins (Mcm2-7) may be useful proliferation markers in dysplasia and cancer in various tissues. AIMS: To investigate the use of Mcm7 as a proliferation marker in 79 lymph node negative prostate cancers and compare it with Ki-67, a commonly used cell proliferation marker. METHODS: The percentage of proliferating cells (proliferation index; PI) was calculated for basal and luminal epithelial cells in benign prostate tissue, prostatic intraepithelial neoplasia (PIN), and epithelial cells in adenocarcinoma. The PI for each biomarker was correlated with the preoperative prostate specific antigen concentration, the Gleason score, surgical resection margin status, and the AJCC pT stage for each patient. RESULTS: The mean PIs for Ki-67 and Mcm7 were: benign luminal epithelium 0.7 and 1.2 and benign basal epithelium 0.8 and 8.2; PIN non-basal epithelium 4.9 and 10.6 and PIN basal epithelium 0.7 and 3.1; adenocarcinoma 9.8 and 22.7, respectively. Mcm7 had a significantly higher mean PI (p<0.0001) than Ki-67 for all cell categories except benign luminal epithelial cells. Mcm7 was a better discriminatory marker of proliferation between benign epithelium, PIN, and invasive adenocarcinoma (p<0.0001) than Ki-67. The drop in Mcm7 mean basal cell PI from benign epithelium to PIN epithelium was significantly larger than for Ki-67 (p<0.0001). Mcm7 had a significantly higher PI than Ki-67 at each risk level. CONCLUSION: Mcm7 may be a useful proliferation marker in prostatic neoplasia and warrants further evaluation as a complementary tool in the diagnosis of PIN and prostate carcinoma.     

Glutathione S-transferase: differential expression of alpha, mu, and pi isoenzymes in benign prostate, prostatic intraepithelial neoplasia, and prostatic adenocarcinoma

Glutathione S-transferases (GST) comprise a family of enzymes which are critical for inactivation of toxins and carcinogens. We examined the cellular expression of multiple subclasses of GST immunohistochemically in 25 radical prostatectomy specimens with clinically localized prostate cancer. Gleason scores ranged from 5 to 9, and pathologic stages varied from pT2a to pT3b (all N0M0). Antibodies were directed against GST Ya, Yc, and Yk (alpha subclass), Yb1 (micro subclass), and YPr (pi subclass). The percentage of positive cells and intensity of staining was assessed for benign epithelium, high-grade prostatic intraepithelial neoplasia (PIN), and adenocarcinoma. GSTalpha (Ya) was detected in 30% of cells (mean) in benign acini, 4.9% of cells in high-grade PIN, and 4.5% of cells in adenocarcinoma. The corresponding results for alpha (Yk), micro (Yb1), and pi (Yp) were 12.7%, 10.9%, and 3.5%; 8.7%, 5.2%, and 0.6%; and 66.7,% 0%, and 0%, respectively. GST Yc (alpha subclass) displayed the lowest level of expression, with diffuse weak staining in scattered benign secretory cells and only single cells (<1%) in high-grade PIN and carcinoma. These results demonstrate consistent reduction or loss of expression of all subclasses of GST with progression of prostatic neoplasia from benign epithelium to high-grade PIN and carcinoma. We hypothesize that carcinogenesis in the prostate results from impaired cellular handling of mutagenic agents owing to reduction or loss of expression of multiple GST and other detoxifying and antimutagenesis agents.     

Expression of group IIA secretory phospholipase A2 is elevated in prostatic intraepithelial neoplasia and adenocarcinoma

Phospholipase A2 (PLA2) enzymes release arachidonic acid from cellular phospholipids in a variety of mammalian tissues, including prostate. Group IIa secretory PLA2 (sPLA2) can generate arachidonate from cellular phospholipids. We examined the group IIa sPLA2 expression in benign prostatic tissues, prostatic intraepithelial neoplasia (PIN), and adenocarcinoma to determine whether sPLA2 expression is altered in the carcinogenesis of human prostatic cancer. Thirty-three of 74 total cases (45%) of benign prostatic tissue showed positive immunohistochemical staining for group IIA sPLA2, whereas 63 of 69 total cases (91%) of high-grade PINs and 70 of 78 total cases (90%) of adenocarcinomas gave positive results. Four of 10 cases of low-grade PIN showed positive immunoreactivity for sPLA2. The number of cells staining for sPLA2 was significantly less in benign epithelium (4%) and low-grade PIN (4%) compared to high-grade PIN (40%) or adenocarcinoma (38%) (P < 0.001). There was no significant difference between high-grade PIN and adenocarcinoma in the number of cells staining positively for sPLA2. The intensity of sPLA2 immunoreactivity was also different among benign prostatic tissue, low-grade PIN, high-grade PIN, and prostatic adenocarcinoma specimens. The malignant cells demonstrated more intense immunohistochemical staining (moderate to strong staining in 81% and 69% cases for high-grade PIN and adenocarcinoma, respectively) than benign glands (moderate staining in 11% of cases). No strong staining was observed in benign glands or low-grade PIN. Our data are consistent with the contention that group IIA sPLA2 expression is elevated in neoplastic prostatic tissue and support the hypothesis that dysregulation of sPLA2 may play a role in prostatic carcinogenesis.     

High-level expression of EphA2 receptor tyrosine kinase in prostatic intraepithelial neoplasia

EphA2 is a transmembrane receptor tyrosine kinase that is overexpressed in many carcinomas. Specific targeting of EphA2 with monoclonal antibodies is sufficient to inhibit the growth, migration and invasiveness of aggressive cancers in animal models. Using immunohistochemical analyses, we measured the expression of EphA2 in prostatic adenocarcinoma, high-grade prostatic intraepithelial neoplasia, and adjacent benign prostate tissue from ninety-three radical prostatectomy specimens. These results were related to multiple clinical and pathologicalcharacteristics. The fraction of cells staining positively with EphA2 in benign prostatic epithelium (mean, 12%) was significantly lower than that in high-grade prostatic intraepithelial neoplasia (mean, 67%, P < 0.001) and prostatic adenocarcinoma (mean, 85%, P < 0.001). Moreover, the intensity of EphA2 immunoreactivity in prostatic adenocarcinoma was significantly higher than in benign prostatic tissue (P < 0.001) or high-grade prostatic intraepithelial neoplasia (P < 0.001). Benign prostatic epithelium showed weak or no immunoreactivity for EphA2 in all cases examined. Whereas EphA2 immunoreactivity related to neoplastic transformation, it did not correlate with other clinical and pathological parameters examined. Our data suggest that EphA2 levels increase as prostatic epithelial cells progress toward a more aggressive phenotype. Progressively higher levels of EphA2 in high-grade prostatic intraepithelial neoplasia and prostatic carcinoma are consistent with recent evidence that EphA2 functions as a powerful oncogene. Moreover, the presence of high levels of EphA2 in these cells suggests opportunities for prostate cancer prevention and treatment.     

Decreased annexin I expression in prostatic adenocarcinoma and in high-grade prostatic intraepithelial neoplasia

AIMS: To analyse annexin I expression in prostatic carcinoma. Annexin I belongs to a family of structurally related calcium and phospholipid-binding proteins implicated in signal transduction, DNA replication, cell proliferation and apoptosis. The decreased expression of annexin I, II and VII proteins has been reported in different types of cancer. METHODS AND RESULTS: Using immunohistochemistry, we analysed annexin I expression in 77 cases of prostatic adenocarcinoma (Gleason score 6, N = 40; Gleason scores 7-8, N = 27; and Gleason scores 9-10, N = 10) and high-grade prostatic intraepithelial neoplasia (PIN, N = 50). Immunoreactivity of annexin I in tumour cells was evaluated as negative (< 5% of cells), focally positive (5-25% of cells) or positive (> 25% of cells). In contrast to positive staining in adjacent benign prostatic epithelium, annexin I expression was decreased (focally positive) in 76% of cases of high-grade PIN (P < 0.0001) and was decreased or absent in 81% of prostatic adenocarcinomas (P < 0.0001). Annexin I expression in all higher grade tumours (Gleason scores 7-10) was only focally positive or absent. CONCLUSIONS: Expression of annexin I inversely correlates with the increasing histological grade of prostatic adenocarcinoma. By showing a progressive loss of annexin I expression in high-grade PIN, intermediate-grade and high-grade cancer, our findings suggest that the loss of annexin I expression occurs early in prostatic tumorigenesis and becomes more prominent throughout tumour progression. The loss of expression of annexin I may serve as a useful marker of prostate cancer development and progression.     

Silver-stained nucleolar organizer regions in the differentiation of prostatic hyperplasia, intraepithelial neoplasia, and adenocarcinoma.

Nucleolar organizer regions (NORs) are loops of chromosomal DNA that ultimately direct the development of the nucleolus. These NORs are associated with argyrophilic acidic nonhistone proteins which have allowed the demonstration of NORs by a simple silver stain. This staining technique has been used to examine the number of silver-stained NORs (AgNORs) in malignant and benign conditions, and, in general, AgNOR numbers are increased in malignant tissues when compared with normal or benign conditions. More recently, this technique has been applied to premalignant lesions with varying results. We applied this silver stain to prostate lesions where nucleolar features are of diagnostic importance. The stain was applied to ten cases of prostatic hyperplasia, ten cases each of prostatic intraepithelial neoplasia (PIN) grades 1 through 3, and ten cases each of low grade, intermediate grade, and high grade adenocarcinoma. The counting was performed by image analysis. A significant mean difference did exist between low grade and the two higher grades of adenocarcinoma. There was no significant difference in AgNOR counts per nucleus in hyperplasia, PIN, or adenocarcinoma or between the three grades of PIN. The AgNOR silver stain is not useful in the differentiation of hyperplasia, the three grades of PIN, and adenocarcinoma. Also because of overlap among the three grades of adenocarcinoma, it is not useful in the differentiation of these lesions.     

前列腺特异性膜抗原在前列腺癌中的表达及临床意义

目的 研究前列腺特异性膜抗原(PSMA)在前列腺癌中的表达及其与Gleason分级之间的关系,同时探讨其在前列腺癌诊断中的价值.方法 采用免疫组化EnVision法检测PSMA在前列腺癌、前列腺上皮内瘤变(PIN)和良性前列腺增生症(BPH)中的表达.结果 PSMA在BPH、PIN和前列腺癌中均表达.在BPH中,PSMA阳性表达部位在前列腺腔缘或顶端/胞质表达,而在PIN中表达模式为胞质伴胞膜阳性,前列腺癌为顶端/胞质、胞质伴胞膜阳性或胞质表达阳性.PSMA在分化差前列腺癌中多为胞质表达,而在分化好的癌中为顶端/胞质和胞质伴胞膜表达.PSMA表达强度在PIN和前列腺癌中明显高于BPH(P＜0.05),同时PSMA染色强度与Gleason评分呈正相关(P＜0.05).结论 PSMA与Gleason分级密切相关,PSMA表达模式和染色强度的改变对PIN和前列腺癌诊断具有参考价值.     

Expression of androgen receptor and growth factors in premalignant lesions of the prostate

Analysis of growth factors and receptors in putative premalignant lesions of prostatic adenocarcinoma should aid our understanding of their growth pathways. Sixty prostatic TURP (transurethral resection of the prostate) specimens exhibiting atypical adenomatous hyperplasia (AAH) and/or prostatic intraepithelial neoplasia (PIN) lesions were assayed by immunohistochemistry for androgen receptor (AR), epidermal growth factor receptor (EGFR), c-erbB-2, transforming growth factor-alpha (TGF-α), vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), MIB-1, E-cadherin, and high molecular weight keratin. Expression of these factors in the lesions was compared with that in the co-existing benign prostatic hyperplasia (BPH) or prostatic adenocarcinoma. Strong AR nuclear staining was observed in the luminal cells, but not the basal cells, of BPH and PIN lesions and in all the carcinomas examined. A similar growth factor and receptor profile was demonstrated in the secretory epithelium of high-grade PIN and carcinoma with a tendency to higher expression of membranous EGFR and c-erbB-2 and cytoplasmic TGF-α, and lower levels of FGF-2 than in low-grade PIN or BPH glands. Also, increased rates of proliferation, as estimated by MIB-1 stained cells, were observed in high-grade PIN in comparison with low-grade PIN and BPH and were not confined to the basal layer. AAH lesions resembled neither BPH nor carcinoma. Proliferation was virtually absent (MIB-1 expression); both AR and E-cadherin expression was significantly reduced; and, with the exception of FGF-2, all the other growth factors and receptors studied were absent. The results presented would support a premalignant role for high-grade PIN, whilst AAH would appear to represent a quiescent phenotype unlikely to progress to neoplasia. Copyright © 1998 John Wiley & Sons, Ltd.     

Metallothionein isoform II expression in hyperplastic, dysplastic and neoplastic prostatic lesions

BACKGROUND: Metallothionein is a low-molecular-weight cysteine-rich protein that has the ability to bind and sequestrate heavy metal ions. It is associated with metalloregulatory functions such as cell proliferation, growth and differentiation. AIMS: To investigate the expression of metallothionein in hyperplastic, dysplastic and neoplastic prostatic lesions and to correlate its expression with histological grade of prostatic carcinoma. Method: The study was carried out on formalin-fixed and paraffin-wax-embedded tissue blocks from 8 patients with benign prostatic hyperplasia, 6 patients with prostatic intraepithelial neoplasia (PIN) and 30 patients with prostatic carcinoma, using the streptavidin-biotin technique. The histological grade was defined and the carcinomas were divided into low-grade (Gleason Score 2-4), 12 moderate grade (Gleason Score 5-6) and 10 high-grade (Gleason Score 7-10) carcinomas. RESULTS: Patchy metallothionein staining of epithelial cells was observed in normal and benign prostatic tissues. All cases of PIN and 20 of 30 patients with prostatic carcinoma showed positive staining for metallothionein. Metallothionein expression considerably increased from low-grade to high-grade tumours. The proportion of cells staining positively for metallothionein was directly correlated with histological grade of prostatic carcinoma. The epithelial cells lack uniformity in staining intensity, but the percentage of strongly positive cells increased with the histological grade of prostatic carcinoma. CONCLUSIONS: The high incidence of metallothionein expression in PIN in our study suggests that it is associated with early prostate tumorigenesis. Also, metallothionein expression was directly correlated with the histological grade of prostatic carcinoma, suggesting that metallothionein may be a useful marker for predicting the prognosis of prostate cancer.     

Nucleolus organizer regions in prostatic intraepithelial neoplasm

Using a silver staining technique, Nucleolar Organizer Region-associated proteins (NORs) were evaluated on paraffin sections of 16 resected prostatic adenocarcinomas stage A1. Then 30 histological areas was selected which comprised 6 areas for each grade of Prostatic Intraepithelial Neoplasia: PIN 1, PIN 2, PIN 3, 6 areas of normal glandular prostatic epithelium and 6 areas of well differentiated prostatic adenocarcinoma (Gleason I). The mean numbers of argyrophilic nucleolar organizer regions (AgNORs) increased from normal glandular prostatic epithelium to PIN 3, while the mean numbers of well differentiated prostatic adenocarcinoma was similar to PIN 1. A statistically significant difference (P less than 0.01) for AgNORs was found between normal glandular epithelium, PIN 1, PIN 2 and PIN 3 and between PIN 3 and well differentiated adenocarcinoma. It was concluded that AgNORs counts provide to significant kinetic evaluation of PIN and prostatic adenocarcinoma besides to supply a better definition of PIN.     

Localization of epidermal growth factor receptor by immunohistochemical methods in human prostatic carcinoma, prostatic intraepithelial neoplasia, and benign hyperplasia.

The epidermal growth factor receptor (EGFr) is a membrane-bound glycoprotein that is present in a wide variety of human normal and malignant tissues. In this study EGFr expression in frozen sections of prostate tissue obtained from 40 different surgical specimens was examined immunohistochemically with a well-characterized monoclonal antibody to EGFr, Ab-1 (Oncogene Science). Twenty cases of prostate adenocarcinoma and 20 cases of benign prostatic hyperplasia were studied. Six of the 20 cases of adenocarcinoma also contained prostatic intraepithelial neoplasia grade III (severe intraductal dysplasia). All of the cases containing benign glands showed strong immunostaining in a continuous or nearly continuous pattern, with staining restricted to the basal layer of the benign glands. Adenocarcinoma lacked immunostaining in 15 (75%) of 20 cases, while the remaining five cases (25%) showed diffuse cytoplasmic staining, which was weaker than that seen in the benign glands and that lacked basal accentuation. The six cases that contained prostatic intraepithelial neoplasia grade III showed a discontinuous basal pattern of staining, and the gaps in the staining appeared to correspond to areas of disruption of the basal cell layer. We conclude that the antigenic determinant recognized by this antibody to EGFr was detected preferentially in the basal layer in benign prostatic glands. In contrast, a minority of cases of adenocarcinoma expressed EGFr, as assessed by immunoreactivity with the Ab-1 monoclonal antibody. Prostatic intraepithelial neoplasia grade III expressed EGFr with a predominantly discontinuous basal pattern that corresponded to the disrupted basal cell layer typical of this process.     

Chromosomal imbalances, loss of heterozygosity, and immunohistochemical expression of TP53, RB1, and PTEN in intraductal cancer, intraepithelial neoplasia, and invasive adenocarcinoma of the prostate

Recent studies have shown that intraductal prostate carcinoma (IDC-P) should be considered as a separate lesion distinct from prostatic intraepithelial neoplasia (PIN). The purpose of the present study was to analyze the genetic relationship between benign prostatic tissue, PIN, invasive cancer, IDC-P, and extracapsular tumor tissue to get further information about the role of IDC-P in the development of prostate cancer. One hundred five radical prostatectomy specimens were investigated immunohistochemically, 77 cases were analyzed by PCR for LOH of the tumor suppressor genes TP53 and RB1, and 11 cases of IDC-P and 10 cases of PIN were investigated using comparative genomic hybridization (CGH). At CGH analysis, IDC-P showed several chromosomal imbalances in contrast to PIN, where no changes were found. We could demonstrate a significant increase of LOH for TP53 or RB1 from benign tissue to PIN. LOH of both TP53 and RB1 were frequently found in IDC-P (52%), followed by extracapsular tumor tissue (44%), invasive cancer (24%), PIN (19%), and benign prostatic tissue (17%). Increased immunohistochemical expression was found in invasive cancer for TP53, RB1, and for PTEN. Decreased expression could be demonstrated in extracapsular tumor tissue and in IDC-P. Our results indicate that IDC-P in general follows the genetic pathway from normal epithelium over PIN lesion. IDC-P represents a separate prostatic lesion and should be graded as a poorly differentiated carcinoma.     

Prostatic intra-epithelial neoplasia: Expression and location of proliferating cell nuclear antigen in epithelial,endothelial and stromal nuclei

The expression and location of proliferating cell nuclear antigen (PCNA) immunostaining in epithelial, endothelial and stromal nuclei were assessed in prostatic intra-epithelial neoplasia (PIN). It was then compared with patterns in benign lesions and in invasive adenocarcinomas of the prostate. The PCNA-positive nuclei showed homogeneous or granular types of staining, or a mixture of both, and a gradation in the intensity of staining. Nuclei with granular and mixed patterns appeared lighter brown than those with a homogeneous pattern, which were darker and more often noted in PIN and invasive adenocarcinomas than in benign lesions. For epithelial PCNA-stained nuclei, the proportions in the two grades of PIN were greater than in benign prostatic hyperplasia (mean 3.16%, SE 0.31%) and prostatic atrophic ducts and acini (mean 0.56%, SE 0.09%), the values decreasing from the nuclei in the basal position towards those in the luminal layer. In grade 1, the category mean values were 9.51% (SE 1.14%) in the basal, 7.02% (SE 1.27%) in the intermediate and 6.02% (SE 0.90%) in the luminal position. In grade 2, the category mean values were 13.81% (SE 1.42%) in the basal position, 10.99% (SE 1.17%) in the intermediate and 7.91% (SE 1.43%) in the luminal position. In small and large acinar adenocarcinomas, the proportions of positive nuclei were 8.66% (SE 0.30%) and 9.06% (SE 0.30%), respectively. The category mean values in the cribriform adenocarcinomas were 14.40% (SE 0.61%) in the basal position, 11.84% (SE 1.30%) in the intermediate and 9.26% (SE 0.66%) in the luminal position. As in PIN, the proportions of immunostained nuclei in the adenocarcinoma with cribriform pattern decreased from the basal towards the luminal layer. In the solid/trabecular adenocarcinomas, the category mean value in the cell layer adjacent to the stroma was 17.60% (SE 2.92%), whereas in the other cell layers it was lower than that in the cells adjacent the stroma (mean 13.88%, SE 1.71%). For capillary endothelial and stromal cells, the percentages of PCNA-stained nuclei were much lower than those in the epithelial component. The lowest mean values were obtained in benign lesions, whereas the highest were in invasive adenocarcinomas, the percentages in PIN being intermediate.This paper was read in part at the Workshop on Chemoprevention of Premalignant and Early Malignant Lesions of the Prostate, Scottsdale, Arizona, USA, 27–29 March, 1992     

Hypermethylation of the human glutathione S-transferase-pi gene (GSTP1) CpG island is present in a subset of proliferative inflammatory atrophy lesions but not in normal or hyperplastic epithelium of the prostate: a detailed study using laser-capture microdissection

Somatic inactivation of the glutathione S-transferase-pi gene (GSTP1) via CpG island hypermethylation occurs early during prostate carcinogenesis, present in approximately 70% of high-grade prostatic intraepithelial neoplasia (high-grade PIN) lesions and more than 90% of adenocarcinomas. Recently, there has been a resurgence of the concept that foci of prostatic atrophy (referred to as proliferative inflammatory atrophy or PIA) may be precursor lesions for the development of prostate cancer and/or high-grade PIN. Many of the cells within PIA lesions contain elevated levels of GSTP1, glutathione S-transferase-alpha (GSTA1), and cyclooxygenase-II proteins, suggesting a stress response. Because not all PIA cells are positive for GSTP1 protein, we hypothesized that some of the cells within these regions acquire GSTP1 CpG island hypermethylation, increasing the chance of progression to high-grade PIN and/or adenocarcinoma. Separate regions (n =199) from 27 formalin-fixed paraffin-embedded prostates were microdissected by laser-capture microdissection (Arcturus PixCell II). These regions included normal epithelium (n = 48), hyperplasticepithelium from benign prostatic hyperplasia nodules (n = 22), PIA (n = 64), high-grade PIN (n = 32), and adenocarcinoma (n = 33). Genomic DNA was isolated and assessed for GSTP1 CpG island hypermethylation by methylation-specific polymerase chain reaction. GSTP1 CpG island hypermethylation was not detected in normal epithelium (0 of 48) or in hyperplastic epithelium (0 of 22), but was found in 4 of 64 (6.3%) PIA lesions. The difference in the frequency of GSTP1 CpG island hypermethylation between normal or hyperplastic epithelium and PIA was statistically significant (P = 0.049). Similar to studies using nonmicrodissected cases, hypermethylation was found in 22 of 32 (68.8%) high-grade PIN lesions and in 30 of 33 (90.9%) adenocarcinoma lesions. Unlike normal or hyperplastic epithelium, GSTP1 CpG island hypermethylation can be detected in some PIA lesions. These data support the hypothesis that atrophic epithelium in a subset of PIA lesions may lead to high-grade PIN and/or adenocarcinoma. Because these atrophic lesions are so prevalent and extensive, even though only a small subset contains this somatic DNA alteration, the clinical impact may be substantial.     

Overexpression of NSAID-activated gene product in prostate cancer

NSAID-activated gene (NAG-1) protein was previously identified by microarray analysis as overexpressed in prostate cancer. We performed immunohistochemistry and Western blotting with rabbit polyclonal antibody to NAG-1. Fifty malignant tissues obtained by prostatectomy and 17 from benign cases were compiled. Cancer tissues included Gleason scores 3-6, 3+4=7, 4+3=7, and 8-10. Cancer and high-grade prostatic intraepithelial neoplasia (PIN) consistently showed moderate to intense cytoplasmic reactivity in 95-100% of epithelium. Staining intensity inversely correlated with preoperative serum prostate-specific antigen (PSA) (p=0.005) and with grade, averaging (on a 0 to 3+ scale) 2.3 +/- 0.6 in the lowest grade group, and 2.0 +/- 0.7, 1.8 +/- 0.5, and 1.5 +/- 0.6 as grade increased (p<0.008). Benign epithelium was nonreactive in 17/17 specimens without concurrent cancer (11 transurethral resection, 2 enucleation, 4 biopsy, p=0.002). Decreased NAG-1 expression in higher grade cancer is consistent with its known antitumorigenic, proapoptotic activities.     

Phenotypic relationships of prostatic intraepithelial neoplasia to invasive prostatic carcinoma.

Thirty-one snap-frozen human prostate specimens containing examples of benign hyperplasia, prostatic intraepithelial neoplasia (PIN), and invasive carcinoma were analyzed using a panel of 24 antibodies and one lectin. Twenty-seven additional routinely processed radical prostatectomy specimens were studied using selected probes known to work on formalin-fixed paraffin-embedded material. Three probes, anticytokeratin KA4, anti-vimentin V9, and the lectin from Ulex europaeus (UEA-1), demonstrated phenotypic similarities between PIN and invasive carcinoma. Whereas the luminal cells of normal or hyperplastic prostatic epithelium are minimally reactive with KA4 (4%) or UEA-1 (0%) and strongly reactive with anti-vimentin (91%), both the PIN and invasive carcinoma are reactive with KA4 (89% and 93%, respectively) and UEA-1 (96% and 93%, respectively) and minimally reactive with anti-vimentin (15% and 0%, respectively). The increased KA4 staining was shown to be in part due to detection of cytokeratin 19, by using cytokeratin-19-specific antibodies, 4.62 and LP2K. The reasons for the increased expression of this cytokeratin and the decreased expression of vimentin are unclear but seem to indicate a phenotypic relationship between the PIN lesions and invasive carcinoma.     

Overexpression of IGBFB2 is a marker for malignant transformation in prostate epithelium

Insulin-like growth factor binding protein 2 (IGFBP2) has been shown to be overexpressed in prostatic intraepithelial neoplasia (PIN) and invasive cancer and the serum level to parallel that of prostate-specific antigen (PSA) in prostate cancer. A combination of cDNA and tissue microarray results recently demonstrated overexpression of IGFBP2 in hormone refractory prostate cancer, indicating that the IGF system may be part of a key growth regulatory pathway in prostate cancer. The present study reexamines the immunohistochemical expression of IGFBP2 and its relationship to grade in tissue from 193 radical prostatectomy specimens from patients with localized prostate adenocarcinoma. We found a significant overexpression of IGFBP2 in all instances of PIN and in more than 90% of cancers regardless of the grade. An intense overexpression was noted in the neuroendocrine cells in normal glands as well as in cancer. The IGFBP2 expression was also analyzed in 18 cases of biopsy diagnosed prostate cancer. In all these cases, the glands interpreted as invasive cancer in hematoxylin-eosin stained sections overexpressed IGFBP2, without a significant correlation to grade. We conclude that overexpression of IGFBP2 is a powerful marker for malignant transformation in the prostate epithelium and suggest that optimized immunohistochemical detection of IGFBP2 expression may be an adjunct tool in the diagnosis of prostate cancer.     

Precursors of prostate cancer

High-grade prostatic intraepithelial neoplasia (PIN) is the only accepted precursor of prostatic adenocarcinoma, according to numerous studies of animal models and man; other proposed precursors include atrophy and malignancy-associated changes (with no morphologic changes). PIN is characterized by progressive abnormalities of phenotype and genotype that are intermediate between benign prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. The only method of detection of PIN is biopsy because it does not significantly elevate serum prostate-specific antigen concentration and cannot be detected by ultrasonography. The mean incidence of PIN in biopsies is 9% (range, 4%-16%), representing about 115,000 new cases of isolated PIN diagnosed each year in the United States. The clinical importance of PIN is its high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent carcinoma, especially when multifocal or observed in association with atypical small acinar proliferation (ASAP). Carcinoma develops in most patients with PIN within 10 years. Androgen deprivation therapy and radiation therapy decrease the prevalence and extent of PIN, suggesting that these forms of treatment may play a role in prevention of subsequent cancer. Multiple clinical trials to date of men with PIN have had modest success in delaying or preventing subsequent cancer.