Proliferative Inflammatory Atrophy Lesions Research Articles

Abstract LB324: STING protein expression is increased in intermediate luminal cells in proliferative inflammatory atrophy of the prostate (PIA) and is absent in the majority of primary prostatic adenocarcinomas

Abstract Unresolved chronic inflammation has been postulated to drive prostate cancer development. We have proposed that proliferative inflammatory atrophy (PIA) can lead to the development of preneoplastic high grade prostatic intraepithelial neoplasia (PIN) lesions and/or directly to adenocarcinoma at times. Additionally, some PIA cells harbor molecular alterations seen in PIN and invasive carcinoma lesions, with a low frequency of PIA cells showing MYC over-expression, partial promoter hypermethylation and silencing of GSTP1, and formation of ETS gene fusions. PIA appears to result from inflammatory injury and regeneration in which proliferative and atrophic epithelial cells have an intermediate cell phenotype with both luminal and basal cell features, including basal cell markers, keratin 5 and BCL2, as well as varying levels of prostate luminal enriched genes such as androgen receptor, PSA and NKX3.1. Also, a number of gene products that are apparently stress induced, which are not expressed in normal prostate are induced in at least a subset of intermediate luminal cells in PIA, including GSTA1, PTGS2, LTF and PIGR (PMIDs:17384581, 37550827). Stimulator of interferon genes (STING), encoded by TMEM173, is a multipass transmembrane ER associated protein, and is a critical hub for innate responses directed against numerous bacterial, viral and parasitic pathogens, and is important for the induction and maintenance of adaptive immunity in a number of situations. Here, we examined STING expression by IHC, using a genetically validated assay, and show that the majority of atrophic prostatic luminal epithelial cells in all PIA lesions (N=20) consistently express high levels of STING, which is present in normal prostatic basal epithelial cells yet absent in normal-appearing prostatic luminal cells. In primary prostatic adenocarcinomas (> 260 tumors), STING protein was either completely negative , or extremely low in ~ 95% of cases. That STING in PIA is activate is supported by single cell RNA sequencing (scRNAseq) data from human prostatectomy tissues that show cells with the phenotype of intermediate luminal cells, indicative of PIA, express a number of interferon response genes that are not expressed in normal luminal cells (PMID 37905029). To our knowledge this is the first systematic report of STING protein staining in human prostate cancer and benign tissues. We postulate that upregulation of STING in human intermediate cells in PIA represents an inflammatory response that can drive interferon stimulated gene expression and inflammation in PIA. This innate immune response is absent, potentially by gene silencing, in prostatic adenocarcinoma, which may help neoplastic cells evade the immune response and could help contribute to the long standing finding that most prostate cancers are immunologically cold. Citation Format: Thomas M. Steele, Alan K. Meeker, Mindy K. Graham, Rulin Wang, Carolina Gomes-Alexandre, William G. Nelson, Fernanda Caramella Pereiria, Sushant Kachhap, Srinivasan Yegnasubramanian, Angelo Michael De Marzo. STING protein expression is increased in intermediate luminal cells in proliferative inflammatory atrophy of the prostate (PIA) and is absent in the majority of primary prostatic adenocarcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB324.

Abstract 3734: Progressive spreading of CpG methylation in the CpG island of Glutathione S-Transferase pi 1 (GSTP1) alleles across transitions from precursor to invasive prostate cancer

Abstract Glutathione S-transferase pi 1 (GSTP1) is expressed at low levels in normal prostate luminal cells and becomes induced in most proliferative inflammatory atrophy lesions (PIA). GSTP1 becomes silenced in prostatic intraepithelial neoplasia (PIN) and prostate adenocarcinoma (CaP) via CpG island promoter hypermethylation. However, the specific methylation patterns in CaP and its precursors have not been investigated. We used bisulfite genomic sequencing to examine methylation of 39 CpG sites in the GSTP1 promoter. Radical prostatectomy specimens were selected from 32 subjects that underwent treatment for CaP. Serial sections were subjected to laser capture microdissection for enrichment of epithelial cells from benign, PIA, PIN, and CaP regions. Isolated DNA was bisulfite converted. Sequences corresponding to the GSTP1 promoter CpG island were amplified with nested PCR, and PCR products were cloned. 10 independent clones were sequenced and analyzed with a Java program, DNAMethylMap, to determine the methylation pattern of 39 CpG sites of the GSTP1 promoter in each lesion. The extent of methylation on an individual allele was classified as negative (<10% CpGs), mild (10-25%), moderate (25-50%), or high (>50%). 212 clones from 24 normal epithelium regions, 327 clones from 37 PIA regions, 167 clones from 18 PIN regions, and 202 clones from 23 CaP regions were sequenced, totaling 34863 CpG sites. Normal and PIA lesions were mostly unmethylated with 0.52% and 1.3% of total CpG sites methylated, respectively. Methylated PIA lesions were adjacent to CaP or PIN regions significantly more often than unmethylated PIA lesions (χ2, p = 0.012). PIN and CaP lesions had greater methylation with 24% and 51% of total CpG sites methylated, respectively. PIN lesions generally showed partial methylation with 28.7% of alleles in PIN having mild/moderate methylation density compared to 5.5% in PIA and 11% in CaP. PIA and PIN lesions were enriched for methylation changes at 6 CpG sites that aligned with AP1 and SP1 binding sites. Among 16 PIN and CaP lesions with an overall intermediate level of methylation, 5 of the lesions had clones that clustered into either fully methylated or unmethylated. One patient with 3 CaP lesions displayed significant heterogeneity in methylation patterns: full, moderate, or no methylation across all clones in a given lesion. The results demonstrate that methylation density in the GSTP1 CpG island from PIN was intermediate between normal prostate epithelium/PIA and CaP lesions. The observed methylation in PIA and PIN was enriched at binding sites of key transcription factors, AP1 and SP1. The results are consistent with gradual spreading of DNA methylation centered at the transcription factor binding sites in the putative precursor lesions, with subsequent spreading of methylation across the entire CpG island in transition to CaP. Citation Format: Harshath Gupta, Hitoshi Inoue, Yasutomo Nakai, Masashi Nakayama, William G. Nelson, Angelo M. De Marzo, Srinivasan Yegnasubramanian. Progressive spreading of CpG methylation in the CpG island of Glutathione S-Transferase pi 1 (GSTP1) alleles across transitions from precursor to invasive prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3734.

Morphological and Molecular Characterization of Proliferative Inflammatory Atrophy in Canine Prostatic Samples.

Simple SummaryProstatic diseases are important worldwide, being the prostate cancer (PC) the most common tumor in men. Among the factors associated with PC development, the preneoplastic lesions are well-recognized. Preneoplastic lesions are cellular morphological alterations, induced by different factors and present a potential to progression for PC. In this scenario, dogs are considered spontaneous models. Dogs naturally develops prostatic hyperplasia, preneoplastic lesions and PC. Among the preneoplastic lesions, the proliferative inflammatory atrophy (PIA) develops spontaneously in dogs. PIA is an epithelial lesion induced by prostatic chronic inflammation, leading to a proliferative atrophy of the prostate gland. Thus, this study aimed to perform a full PIA morphological, phenotypical and molecular characterization in dogs. After reviewing the archives of the veterinary pathology service, it was identified 171 dogs containing PIA in the prostate gland, and among the PC cases (N = 84), it was identified PIA lesions surrounding 60.7% of PC cases. Besides that, we identified loss of genes related to the maintenance of prostatic tissue and can predispose to malignant transformation. Moreover, mutations in androgen receptor gene were identified, demonstration alteration in DNA in PIA. Overall, these results support the hypothesis that PIA can be considered a preneoplastic lesion in canine prostate.Proliferative inflammatory atrophy (PIA) is an atrophic lesion of the prostate gland that occurs in men and dogs and is associated with a chronic inflammatory infiltrate. In this study, we retrospectively reviewed canine prostatic samples from intact dogs, identifying 50 normal prostates, 140 cases of prostatic hyperplasia, 171 cases of PIA, 84 with prostate cancer (PC), 14 with prostatic intraepithelial neoplasia (PIN) and 10 with bacterial prostatitis. PIA samples were then selected and classified according to the human classification. The presence of PIA lesions surrounding neoplastic areas was then evaluated to establish a morphological transition from normal to preneoplastic and neoplastic tissue. In addition, the expression of PTEN, P53, MDM2 and nuclear androgen receptor (AR) were analyzed in 20 normal samples and 20 PIA lesions by immunohistochemistry and qPCR. All PIA lesions showed variable degrees of mononuclear cell infiltration around the glands and simple atrophy was the most common histopathological feature. PIA was identified between normal glands and PC in 51 (61%) out of the 84 PC samples. PIA lesions were diffusely positive for molecular weight cytokeratin (HMWC). Decreased PTEN and AR gene and protein expression was found in PIA compared to normal samples. Overall, our results strongly suggest that PIA is a frequent lesion associated with PC. Additionally, this finding corroborates the hypothesis that in dogs, as is the case in humans, PIA is a pre neoplastic lesion that has the potential to progress into PC, indicating an alternative mechanism of prostate cancer development in dogs.

Diagnostic Utility of Cytokeratin-5 for the Identification of Proliferative Inflammatory Atrophy in the Canine Prostate

Proliferative inflammatory atrophy (PIA), which is comprised of highly proliferative but atrophic prostate epithelial cells in association with chronic inflammation, is considered a risk lesion for prostate cancer in men, while its role in canine prostate carcinogenesis is still unknown. We evaluated the value of immunohistochemical labelling for the basal cell marker cytokeratin-5 (CK5) in identifying PIA lesions in 87 samples of formalin-fixed and paraffin wax-embedded canine prostate. Canine PIA showed cytological features identical to the human counterpart and in most cases was associated with chronic lymphoplasmacytic inflammation. PIA lesions were identified in a higher number of CK5-labelled slides (43 out of 87) compared with slides stained by haematoxylin and eosin (HE) (24 out of 87). This lesion was frequently present in normal, hyperplastic and neoplastic canine prostates, although it was underestimated on evaluation of HE-stained slides. Therefore, CK5 can be considered a useful basal cell marker with high sensitivity and specificity for PIA.

Abstract 492: Chronic inflammation contributes to neoplastic progression in prostate tissue: a needle biopsy study

Abstract The relationship between inflammation and prostate cancer has not been established, although chronic inflammation has frequently been identified in prostate biopsies, radical prostatectomy and benign prostatic hyperplasia specimens. In the peripheral zone of the prostate, sometimes adjacent to foci of high-grade PIN and cancer, certain morphologic changes are often identified, which may represent active and terminal phases of chronic inflammation. These changes are designated as proliferative inflammatory atrophy (PIA) and post atrophic hyperplasia (PAH), and their morphology is well documented. In our previous studies, we have identified chronic inflammation as a putative contributor to neoplastic progression in prostate epithelial cells, and hypothesized that its adverse effects were related to an increase in Bcl2, a survival protein involved in cell survival and carcinogenesis. We hypothesize that changes in the stromal microenvironment, characterized by infiltration of immune cells, with generation of reactive oxygen species, can induce oxidative stress in the surrounding proliferating epithelium and cause permanent genomic alterations. In the present study, we focused on several key proteins involved in the inflammatory process, COX2 and iNOS; cell survival, Bcl2 and GSTPπ; and evaluated immunohistochemical expression of alpha-methylacyl coenzyme A racemase (AMACR) and basal cell-specific markers 34βE12 and/or p63 to evaluate possible neoplastic alterations in epithelial cells in an inflammatory environment. We evaluated 16 prostate core needle biopsy specimens that exhibited the presence of chronic inflammation as well as PIA and PAH lesions along with immunohistochemical staining for various markers was performed in each set of biopsies. The integrity of the basal layer was maintained in the area of chronic inflammation with high expression of p63 in 72% of these cells. Approximately 68% of luminal cells expressed high to moderate levels of iNOS and COX-2, whereas 55% of these cells express modest levels of GSTP1 and Bcl2. Interestingly, prostatic glands near the areas of chronic inflammation in the PIA lesions exhibit high AMACR expression in luminal cells and weak to patchy p63 expression in basal cells, which was associated with increased expression of the inflammatory markers COX2 and iNOS, as well as loss in pro-survival signal GSTP1 and Bcl2 in the adjacent luminal cells. These neoplastic alterations were observed in 6/16 (38%) of the needle biopsy specimens. Our findings suggest that basal cells undergo alterations in a setting of chronic inflammation. This is important because basal cells are considered to be progenitor cells capable of differentiating into secretory luminal cells, but under the influence of chronic inflammation, they may instead transform into the neoplastic cells that characterize high grade prostatic intraepithelial neoplasia and prostatic adenocarcinoma. Citation Format: Shardul C. Soni, Michael Glover, Qinghu Ren, Gregory T. MacLennan, Pingfu Fu, Sanjay Gupta. Chronic inflammation contributes to neoplastic progression in prostate tissue: a needle biopsy study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 492. doi:10.1158/1538-7445.AM2017-492

Abstract 2406: Molecular characterization of ciclooxigenase-2 in canine proliferative inflammatory atrophy of the prostate

Abstract Due to the importance and incidence of prostatic carcinoma in man, some animals are being used as a model in the investigation of the pathogenesis and development of this lesion. Similarly to men, the dog presents a spontaneous development of prostate cancer, which is locally invasive and can develop bone metastasis. Proliferative inflammatory atrophy (PIA) is considered a pre-neoplastic lesion in men. Overexpression of COX-2 has been associated with PIA, PIN and prostatic carcinoma playing a role in angiogenesis, apoptosis inhibition, increasing of invasive capacity, metastasis and inflammation in different prostatic affections. The aim of this study was to assess the protein and gene expression of COX-2 in laser capture microdissected stroma and epithelial cells of PIA foci in canine prostate by immunohistochemistry (IHC) and qRT-PCR. For IHC, 38 PIA lesions arranged in a tissue microarray were evaluated. Frozen fragments from 17 PIA and 3 normal prostatic tissues were used for COX2 gene expression. Our results showed increased COX2 gene expression in stromal cells compared to epithelial cells. High level of COX-2 protein expression was observed in 87% of PIA lesions, despite epithelial or stromal compartment. The In the present study, the stroma presented an important role, since the COX-2 gene expression in canine PIA lesions was increased in this cell compartment. To the best of our knowledge, this is the first report of COX2 gene expression in canine PIA. Since high levels of COX-2 have been associated to the risk of developing of prostate cancer in man, dog can be used as a natural model for this disease. The stroma can act as paracrine way in the epithelial cells, stimulating epithelial proliferation, reducing the apoptosis of this compartment and promoting angiogenesis in the microenvironment, factor that contribute to prostatic carcinogenesis and that the protein expression is increased in this lesion. Sponcer: Fapesp (Fundação de Apoio a Pesqusia do Estado de São Paulo) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2406. doi:10.1158/1538-7445.AM2011-2406

804 IL-17 EXPRESSED LEUKOCYTES ARE CHARACTERISTIC OF PROSTATE INFLAMMATORY ATROPHY LESIONS IN PATIENTS WITH PROSTATE CANCER

You have accessJournal of UrologyInfections/Inflammation of the Genitourinary Tract: Prostate & Genitalia1 Apr 2010804 IL-17 EXPRESSED LEUKOCYTES ARE CHARACTERISTIC OF PROSTATE INFLAMMATORY ATROPHY LESIONS IN PATIENTS WITH PROSTATE CANCER Eugene Vykhovanets, Gregory MacLennan, Olena Vykhovanets, and Sanjay Gupta Eugene VykhovanetsEugene Vykhovanets More articles by this author , Gregory MacLennanGregory MacLennan More articles by this author , Olena VykhovanetsOlena Vykhovanets More articles by this author , and Sanjay GuptaSanjay Gupta More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.1480AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The phenotype of intraprostatic mononuclear cells (MNC) is still illusive, despite their role for chronic inflammation and prostate cancer (PCa). Expression of interleukin (IL)-17 is a characteristic of a CD4 T cell subset called T helper 17 (TH17) cells. Their role in host defense and in autoimmunity was recently established. Little is known about other IL-17 expressing cells at sites of tissue inflammation. Based on our previous findings we hypothesized that the IL-17 producing cells may be targets of specific inflammatory signals that initiate inflammation at sites of proliferative inflammatory atrophy (PIA) of the prostate. METHODS To immunophenotype MNC infiltrates we evaluated 30 formalin-fixed paraffin-embedded whole mount radical prostatectomy specimens. Two-color immuno-histochemestry was employed to distinguish macrophages (Mφ), B, T, and CD4 T helper cells. Quantitation of IL-17 cells was performed in all sites of MNC accumulation in the entire prostate, noting their relationships to PCa, PIA, or benign tissue. RESULTS T and B cells were commonly observed at the site of MNC accumulation (“hot spots”). The number of hot spots varied significantly from case to case (mean = 24±12 [SD] per prostate). MNC aggregates were found in and around areas of PCa, and in areas of PIA. The numbers of B and T cells were almost equal within the MNC hot spots. CD4 helper cells were the predominant T cells in the MNC hot spots. Levels of IL-17 cells were similar in zones of benign prostate tissue and areas of PCa. Pronounced intraluminal and peri-glandular IL-17 cell accumulation characterized the MNC infiltrates associated with PIA lesions. The number of IL-17 cells in the intraluminal and peri-glandular areas of PIA lesions was 5 fold higher than in the MNC aggregates within areas of PCa and 5 fold higher than in benign tissue populated by only scattered MNC. The number of IL-17 cells in the intraluminal and peri-glandular areas of PIA lesions was 3 fold higher than in MNC aggregates in benign tissue adjacent to PCa, and 3 fold higher than in randomly situated MNC aggregates in benign prostate tissue. Consecutive slide analysis indicated that glandular and peri-glandular Mφ and neutrophils, rather than TH17 cells, were the predominant IL-17 producing cells in PIA lesions. CONCLUSIONS These data demonstrate that release of inflammatory IL-17 by MNC may be the initiating factor in prostatic PIA. The accumulation of IL-17 producing cells in PIA lesions presents direct evidence of an inflammatory microenvironment that may support the development and progression of PCa. Cleveland, OH© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e314 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Eugene Vykhovanets More articles by this author Gregory MacLennan More articles by this author Olena Vykhovanets More articles by this author Sanjay Gupta More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Morphological transition of proliferative inflammatory atrophy to high‐grade intraepithelial neoplasia and cancer in human prostate

Inflammation has been implicated as a potential etiological agent in human prostate cancer (PCa). Proliferative inflammatory atrophy (PIA) in prostate consists of areas of glandular atrophy associated with chronic inflammation and epithelial cell proliferation. It has been suggested that PIA is a candidate precursor of prostate malignancy. We aimed to explore the morphological transition between PIA and co-existing high-grade prostate intraepithelial neoplasia (HGPIN) and/or PCa. Serial slides of 50 whole-mounted radical prostatectomies were studied with H&E staining and immunostaining of cytokeratin 5 (CK5), glutathione S-transferase pi (GSTP1), hepatocyte growth factor receptor (c-MET), CCAAT/enhancer binding protein beta (C/EBPbeta), and Ki-67. Utilizing immunohistochemical stains to examine HGPIN, PIA-merging HGPIN, and PIA-merging PCa lesions, respectively. A total of 1,188 HGPIN lesions were identified, of which 17% (198) were in the morphological process of merging with PIA. Thirty-six PIA-merging PCa lesions were also detected. The atrophic epithelial cells in such merging lesions had increased Ki-67 index and an intermediate phenotype: increased expression for CK5, GSTP1, c-MET, and C/EBPbeta. In addition, clusters of atypical epithelial cell hyperplasia, that is, with nuclear enlargement, hyperchromasia, and prominent nucleoli, were found in 16 PIA lesions. Such clusters of atypical cells that meet the criteria for HGPIN still expressed CK5 and were adjacent to focal chronic inflammation. Direct morphological transition between PIA and HGPIN and/or PCa was present. The atrophic cells in these merging lesions had an intermediate phenotype. Clusters of atypical epithelial cell hyperplasia might represent the earliest transition from PIA to HGPIN. Prostate 69: 1378-1386, 2009. (c) 2009 Wiley-Liss, Inc.

Increased p53 immunoreactivity in proliferative inflammatory atrophy of prostate is related to focal acute inflammation

Proliferative inflammatory atrophy (PIA) of prostate has been proposed as a precursor lesion of prostate cancer. The aim of the current study was to evaluate the expression of p53 protein in PIA lesions and to investigate the relationship between p53 staining and Ki-67, glutathione S-transferase-pi (GSTP1) and cyclooxygenase-2 (COX-2) immunohistochemical expression. The results revealed that p53 nuclear immunostaining appeared in PIA lesions in 2.1+/-3.4% (mean+/-SD) of the basal and 0.9+/-2.3% of the luminal epithelial cells. Both these values were significantly higher than those in normal-appearing acini (p<0.0001). Increased p53 expression in luminal cells was related to focal infiltration of polymorphonuclear leucocytes. A positive correlation between p53 expression and Ki-67 was found in COX-2-positive PIA lesions (r=0.610, p<0.0001). Half of the p53-positive epithelial cells expressed diffuse GSTP1 immunostaining in the same lesions. The present study demonstrates an increased p53 expression in PIA lesions, and inflammation, especially acute inflammation, may play a role in the induction of p53 over-expression, particularly as cells in PIA lesions are known to have a reduced defence against DNA damage.

Increased expression of CCAAT/enhancer‐binding protein beta in proliferative inflammatory atrophy of the prostate: Relation with the expression of COX‐2, the androgen receptor, and presence of focal chronic inflammation

Proliferative inflammatory atrophy (PIA) in the prostate has been proposed to be a precursor to prostate cancer. CCAAT/enhancer-binding protein beta (C/EBPbeta) is an important transcription factor involved in cellular proliferation and differentiation. Activation of C/EBPbeta plays a crucial role during the initial stage of cyclo-oxygenase 2 (COX-2) induction by proinflammatory mediators. Overexpression of C/EBPbeta has been reported in several human tumors. Nevertheless, the C/EBPbeta expression and functions in human prostate tissue are basically unknown. C/EBPbeta immunohistochemical staining was performed on 45 benign prostate hyperplasia (BPH) samples. The expression of C/EBPbeta in PIA lesions and normal-appearing acini was analyzed. In addition, by using double-IHC staining, C/EBPbeta expression and the association with chronic inflammatory cell density, co-expression of COX-2 and androgen receptor (AR) were also investigated. C/EBPbeta was occasionally observed in normal-appearing prostate acini (4.9% +/- 6.7%, Mean +/- SD) but was clearly overexpressed in PIA lesions (81.8% +/- 16.4%) (P < 0.0001). Atrophic glands with T-lymphocyte and macrophage inflammation expressed higher level of C/EBPbeta. Furthermore, C/EBPbeta correlated significantly with COX-2 expression. Downregulation of the AR was common in PIA and was also related to the C/EBPbeta overexpression. The data demonstrated that chronic inflammation appeared to play roles in the induction of C/EBPbeta expression in prostate epithelium, which was in turn associated with increased COX-2 expression and AR downregulation. In combining with other molecular alteration in the epithelium of PIA, it is suggested that these cells might be a kind of intermediate cells and involved in the pathogenesis of prostate cancer.

P16 Is upregulated in proliferative inflammatory atrophy of the prostate

Proliferative inflammatory atrophy (PIA) of the prostate is a common histological finding that has been postulated to be associated with prostate cancer. We examine PIA lesions for the expression of p16/CDKN2, a cyclin-dependent kinase inhibitor frequently altered in prostate cancer. Within tissues from two independent patient populations ("Test Set" and "Validation Set") undergoing radical prostatectomy, PIA lesions were identified and subjected to immunohistochemical staining for p16. Atrophic epithelial cells and regional normal epithelium were scored for the extent of p16 staining. In the Test Set, staining was also performed for the proliferation marker Ki-67. Double label immunofluorescence was employed to co-localize staining for p16 and Ki-67. p16 expression was elevated in PIA in both data sets compared to normal epithelium (mean percent of cells staining positive in PIA = 11.1%-16.2%; mean percent of cells staining positive in normal = 0.6%-1.3%) (P = 0.0001). As expected from prior studies, the mean Ki-67 index was higher in PIA lesions (mean 8.2% staining positive) versus normal epithelium (mean 1.9% staining positive) (P = 0.0001), and the extent of staining for p16 correlated with Ki-67 (r = 0.7, P < 0.0001). However, co-localization immunofluorescent studies did not demonstrate staining for nuclear p16 and Ki-67 in the same cells. Increased p16 expression accompanies increased cell proliferation in PIA lesions of the prostate. Yet, on the individual cell level, the upregulation of p16 in PIA lesions appears to represent a non-proliferative stress response, possibly to oxidative damage.

THE ROLE OF INFLAMMATION IN THE PATHOGENESIS OF PROSTATE CANCER

A new hypothesis for the etiology of prostate cancer is that chronic or recurrent prostate inflammation may initiate and promote prostate cancer development. We reviewed the current direct and indirect evidence from epidemiology, genetics, molecular biology and histopathology implicating inflammation in the pathogenesis of prostate cancer. The case for prostate inflammation as a cause of prostate cancer is compelling. Epidemiology data have correlated prostatitis and sexually transmitted infections with increased prostate cancer risk and intake of anti-inflammatory drugs and antioxidants with decreased prostate cancer risk. Genetic studies have identified RNASEL, encoding an interferon inducible ribonuclease, and MSR1, encoding subunits of the macrophage scavenger receptor, as candidate inherited susceptibility genes for familial prostate cancer. Somatic silencing of GSTP1, encoding a glutathione S-transferase capable of defending against oxidant cell and genome damage, has been found in almost all prostate cancer cases. Proliferative inflammatory atrophy lesions containing activated inflammatory cells and proliferating epithelial cells appear likely to be precursors to prostatic intraepithelial neoplasia lesions and prostatic carcinomas. Emerging hints that prostate inflammation may contribute to prostatic carcinogenesis will provide opportunities for the discovery and development of new drugs and strategies for prostate cancer prevention.

Intermediate Cells in Human Prostate Epithelium Are Enriched in Proliferative Inflammatory Atrophy

Within the human prostate epithelium four cell populations can be discriminated based on their expression of keratins (K). Basal cells express high levels of K5 and K14, as well as p63, whereas they have very low levels of androgen receptor, prostate-specific antigen (PSA), K8, and K18. Luminal secretory cells lack p63, K5, and K14 but express high levels of K8, K18, androgen receptor, and PSA. Additionally, cells have been identified with a keratin phenotype intermediate between basal and luminal cells that co-express high levels of K5 and K18 (K5/18) as well as hepatocyte growth factor receptor c-MET. Although intermediate cells have been proposed as precursor cells of prostate cancer, their biology is ill defined. Epithelial cells in proliferative inflammatory atrophy (PIA) appear to be cycling rapidly as indicated by expression of Ki-67, and morphological transitions have been identified between PIA and high-grade prostate intraepithelial neoplasia. Many of the atrophic epithelial luminal cells in PIA are candidates for intermediate cells based in part on weak expression of PSA and androgen receptor, high levels of K8/18, and lack of p63. The objective of this study was to further clarify the phenotype of the proposed intermediate cells in PIA and to quantitatively determine the level in which these intermediate cells preferentially occur in PIA lesions. Intermediate cells were immunohistochemically demonstrated using antibodies to K5, K14, K18, and c-MET. Using radical prostatectomy specimens (n = 15) the area fraction of intermediate cells in normally differentiated prostate epithelium and PIA were quantified by a grid point counting method. Atrophic luminal cells of PIA lesions expressed K5 in 39.2 +/- 7.4% of cells compared to 2.4 +/- 2.3% in normal epithelium (P < 0.00001). By contrast, K14 was only expressed in 3.0 +/- 3.2% of the luminal cells. Previous studies have shown that virtually 100% of these atrophic luminal cells are strongly positive for K8/18. c-MET was present in 44.1 +/- 14.1% of luminal cells in PIA but only in 2.1 +/- 2.8% of luminal cells in normal epithelium (P < 0.00001). To unambiguously determine whether intermediate luminal cells in PIA show increased proliferative activity and decreased p27(kip1) expression, double-staining immunofluorescence of Ki-67 and K5, as well as p27(Kip1) and K5 was performed. Luminal cells in PIA often co-expressed K5 and Ki-67. Although p27(Kip1) was strongly expressed in K5-negative differentiated cells in normal epithelium, p27(Kip1) staining was absent in many of the K5-positive cells in the luminal compartment of PIA. We conclude that cells phenotypically intermediate between basal and secretory cells are enriched in PIA lesions. The finding of a large number of highly proliferating intermediate cells in PIA provides further support that these cells may serve as preferred target cells in prostate carcinogenesis.

Preneoplastic prostate lesions: an opportunity for prostate cancer prevention.

Environmental factors, especially the diet, play a prominent role in the epidemic of prostate cancer (PCA), in the United States. Many candidate dietary components have been proposed to influence human prostatic carcinogenesis, including fat, calories, fruits and vegetables, anti-oxidants, and various micronutrients, but the specific roles dietary agents play in promoting or preventing PCA remain controversial. We have collected evidence to suggest that GSTP1, the gene encoding the pi-class glutathione S-transferase (GST), may serve a "caretaker" function for prostatic cells. Although GSTP1 can be detected in normal prostatic epithelium, in almost all PCA cases, PCA cells fail to express GSTP1 polypeptides, and lack of GSTP1 expression most often appears to be the result of somatic "CpG island" DNA methylation changes. Loss of GSTP1 function also appears to be characteristic of prostatic epithelial neoplasia (PIN) lesions, thought to represent PCA precursors. We have recently learned that a new candidate early PCA precursor lesion, proliferative inflammatory atrophy (PIA), characterized by proliferating prostatic cells juxtaposed to inflammatory cells, contains epithelial cells that express high levels of GSTP1. These findings have formed the basis for a new model of prostatic carcinogenesis, in which prostatic cells in PIA lesions, subjected to a barrage of inflammatory oxidants, induce GSTP1 expression as a defense against oxidative genome damage. When cells with defective GSTP1 genes appear amongst the PIA cells, such cells become vulnerable to oxidants and electrophiles that inflict genome damage that tends to promote neoplastic transformation to PIN and PCA cells. Subsequently, PIN and PCA cells with defective GSTPI genes remain vulnerable to similar stresses tending to promote malignant progression. This new model for prostatic carcinogenesis has implications for the design of new prostate cancer prevention strategies. Rational prevention approaches might include: (i) restoration of GSTPI expression via treatment with inhibitors of CpG methylation, (ii) compensation for inadequate GSTPI activity via treatment with inducers of general GST activity, and (iii) abrogation of genome-damaging stresses via avoidance of exogenous carcinogens and/or reduction of endogenous carcinogenic (particularly oxidant) stresses.