Growth, regeneration, and tumorigenesis of the prostate activates the PSCA promoter

Significance of PSCA as a novel prognostic marker and therapeutic target for cancer

One of the contributing factors in the diagnosis and treatment of most cancers is the identification of their surface antigens. Cancer tissues or cells have their specific antigens. Some antigens that are present in many cancers elicit different functions. One of these antigens is the prostate stem cell antigen (PSCA) antigen, which was first identified in the prostate. PSCA is a cell surface protein that has different functions in different tissues. It can play an inhibitory role in cell proliferation as well as a tumor-inducing role. PSCA has several genetic variants involved in cancer susceptibility in some tissues, so identifying the characteristics of this antigen and its relationship with clinical features can provide more information on diagnosis and treatment of patients with cancers. Most studies on the PSCA have focused on prostate cancer. While it is also expressed in other cancers, little attention has been paid to its role as a valuable diagnostic, prognostic, and therapeutic tool in other cancers. PSCA has several genetic variants that seem to play a significant role in cancer susceptibility in some tissues, so identifying the characteristics of this antigen and its relationship and variants with clinical features can be beneficial in concomitant cancer therapy and diagnosis, as theranostic tools. In this study, we will review the alteration of the PSCA expression and its polymorphisms and evaluate its clinical and theranostics significance in various cancers.

Identification of Critical Molecular Factors and Side Effects Underlying the Response to Thalicthuberine in Prostate Cancer: A Systems Biology Approach

Background

Uncontrolled mitosis of cancer cells and resistance cells to chemotherapy drugs are the challenges of prostate cancer. Thalicthuberine causes a mitotic arrest and a reduction of the effects of drug resistance, resulting in cell death. In this study, we applied bioinformatics and computational biology methods to identify functional pathways and side effects in response to Thalicthuberine in prostate cancer patients.

Methods

Microarray data were retrieved from Gene Expression Omnibus (GEO), and protein-protein interactions and gene regulatory networks were constructed, using the Cytoscape software. The critical genes and molecular mechanisms in response to Thalicthuberine and its side effects were identified, using the Cytoscape software and WebGestalt server, respectively. Finally, GEPIA2 was used to predict the relationship between critical genes and prostate cancer.

Results

The POLQ, EGR1, CDKN1A, FOS, MDM2, CDC20, CCNB1, and CCNB2 were identified as critical genes in response to this drug. The functional mechanisms of Thalicthuberine include a response to oxygen levels, toxic substances and immobilization stress, cell cycle regulation, regeneration, the p53 signaling pathway, the action of the parathyroid hormone, and the FoxO signaling pathway. Besides, the drug has side effects including muscle cramping, abdominal pains, paresthesia, and metabolic diseases.

Conclusion

Our model suggested newly predicted crucial genes, molecular mechanisms, and possible side effects of this drug. However, further studies are required.

RNA interference targeting PSCA suppresses primary tumor growth and metastasis formation of human prostate cancer xenografts in SCID mice

BACKGROUND AND OBJECTIVES

Prostate stem cell antigen (PSCA) is a cell surface, glycosylphosphatidylinositol (GPI)-anchored glycoprotein. Its overexpression has been detected in both local and metastatic prostate cancer (PCa), making it a potential therapeutic target. We previously reported that silencing PSCA by small interfering RNA targeting human PSCA (siRNA-PSCA) inhibited biological activity of PSCA-positive PCa cells leading to reduced proliferation, motility and invasion in vitro. In this study, we extended this in vitro findings to in vivo settings in order to investigate the effects of this specific siRNA on the tumor growth and metastasis development of PCa in vivo.

MATERIALS AND METHODS

The siRNA-PSCA and ectopically overexpressed-PSCA vector were constructed and transfected into human PCa PC-3M and LNCaP cells, respectively, and were subcutaneously inoculated into the male SCID mice. Tumor growth was measured with a caliper, and formation of metastasis in mice bearing xenograft tumors was studied by magnetic resonance imaging (MRI) and autopsy analysis. Western blot and immunohistochemistry were used to assess the expression levels of PSCA protein in tumor tissues from xenograft and distant metastases.

RESULTS

Consistent with our previous in vitro findings, the subcutaneous xenografts of PC-3M-siPSCA exhibited the almost completely inhibited expression of PSCA protein in their tumors tissues (P < 0.001 and P < 0.001, respectively), and consequently had a significant reduction in tumor growth volumes (P < 0.05 for all), and metastasis onset and sites (P < 0.001 for all) compared to those of PC-3M and PC-3M-siScrm. Conversely, LNCaP-PSCA showed significantly enhanced primary tumor growth and metastasis formation of xenografts compared to LNCaP-vehicle and LNCaP cells (P < 0.001 for all). Moreover, the up-regulated expression of PSCA protein was detected in the distant metastases of xenograft tumors from all groups.

CONCLUSIONS

Taken together, these observations suggest that PSCA has a promoting role in the growth and metastasis of PCa and siRNA-PSCA may be a potential therapeutic strategy for PSCA-positive PCa.

PSCA acts as a tumor suppressor by facilitating the nuclear translocation of RB1CC1 in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is an aggressive malignancy; its mechanisms of development and progression are poorly understood. By high-throughput transcriptome sequencing (RNA-Seq) profiling of three pairs of primary ESCCs and their corresponding non-tumorous tissues, we identified that prostate stem cell antigen (PSCA), a gene that encodes a glycosylphosphatidylinositol-anchored protein, is significantly downregulated in ESCC. Here, we reported decreased expression of PSCA in 188/218 (86.2%) of primary ESCC cases and was negatively regulated by its transcription factor sex-determining region Y-box5 that was significantly associated with the poor differentiation (P = 0.003), increased lymph node metastasis (P < 0.0001), advanced stage (P = 0.007), and disease-specific survival (P < 0.0001), but not associated with the recently reported transcrible rs2294008 (C > T) polymorphism in ESCC. Functional studies showed that PSCA could arrest cell cycle progression and promote cell differentiation independent of the start codon polymorphism. Further mechanistic studies revealed that retinoblastoma 1-inducible coiled-coil 1 (RB1CC1), a key signaling node to regulate cellular proliferation and differentiation, interacted specifically with PSCA in ESCC cells. Binding of PSCA and RB1CC1 in cytoplasm resulted in stabilization and translocation of RB1CC1 into nucleus, thereby activating key factors involved in cell cycle arrest and differentiation. Collectively, our data provide a novel molecular mechanism for the tumor suppressor role of PSCA and may help design effective therapy targeting PSCA-RB1CC1 pathway to control esophageal cancer growth and differentiation.

Prostate stem cell antigen and cancer risk, mechanisms and therapeutic implications

Prostate stem cell antigen (PSCA) was originally identified as a tumor antigen in prostate cancer. Recent studies indicated that PSCA was correlated with many cancer types. In this review, we will consider the origin of PSCA, discuss the expression of PSCA in normal and cancer tissue, describe PSCA polymorphisms and cancer risk, summarize potential mechanisms for PSCA involvement in cancer; and look into the therapeutic implications of PSCA. PSCA is upregulated in prostate cancer, pancreatic cancer and bladder cancer, as well as a number of others, making it an ideal clinical target for both diagnosis and therapy. Future studies will be required to explore its mechanisms on various cancer types, and to confirm its clinical utility for diagnosis and immunotherapy strategies. The study of PSCA regulation and expression may also provide information on normal prostate development and prostate carcinogenesis.

Prostate stem cell antigen - novel biomarker and therapeutic target?

Prostate stem cell antigen gene was originally identified through an analysis of genes upregulated in the human prostate cancer LAPC-4 xenograft model. PSCA was named inaccurately since it is not a marker for a stem cell population nor is it exclusively expressed in the prostate. The function of PSCA in normal cellular processes or carcinogenesis is currently unknown.

Positive and negative regulation of prostate stem cell antigen expression by Yin Yang 1 in prostate epithelial cell lines

Prostate cancer is influenced by epigenetic modification of genes involved in cancer development and progression. Increased expression of Prostate Stem Cell Antigen (PSCA) is correlated with development of malignant human prostate cancer, while studies in mouse models suggest that decreased PSCA levels promote prostate cancer metastasis. These studies suggest that PSCA has context-dependent functions, and could be differentially regulated during tumor progression. In the present study, we identified the multi-functional transcription factor Yin Yang 1 (YY1) as a modulator of PSCA expression in prostate epithelial cell lines. Increased YY1 levels are observed in prostatic intraepithelial neoplasia (PIN) and advanced disease. We show that androgen-mediated up-regulation of PSCA in prostate epithelial cell lines is dependent on YY1. We identified two direct YY1 binding sites within the PSCA promoter, and showed that the upstream site inhibited, while the downstream site, proximal to the androgen-responsive element, stimulated PSCA promoter activity. Thus, changes in PSCA expression levels in prostate cancer may at least partly be affected by cellular levels of YY1. Our results also suggest multiple roles for YY1 in prostate cancer which may contribute to disease progression by modulation of genes such as PSCA.

Small interference RNA-mediated silencing of prostate stem cell antigen attenuates growth, reduces migration and invasion of human prostate cancer PC-3M cells

OBJECTIVES

Prostate stem cell antigen (PSCA), a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein, is highly expressed in both local and metastatic prostate cancer (CaP). Elevated PSCA expression has been shown to correlate with malignant phenotype and clinical progression. The purpose of the current study is to investigate the therapeutic potential of small interference RNA (siRNA) targeting PSCA on human CaP cells.

MATERIALS AND METHODS

A set of two siRNAs directed different regions of human PSCA (siRNA-PSCA) were designed and transfected into a human CaP PC-3M cell line. The silencing effect was screened by RT-PCR and Western blotting. The biological effects of siRNA-PSCA on PC-3M cells were investigated by examining the cell proliferation through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell cycle distribution through flow cytometry, and migration and invasion potencies through transwell invasion assay upon the PSCA silencing.

RESULTS

PC-3M cells had positive PSCA expression on immunocytochemical assay. PSCA expression was depleted at 48 hours after transfection with siRNA-PSCA. Silencing of PSCA significantly suppressed cell proliferation. Cell cycle assay showed that the anti-proliferation effect of siRNA-PSCA was mediated by arresting cells in the G0/G1 phase rather than apoptosis. Furthermore, PSCA knockdown resulted in a marked decrease of cell migration and invasion capabilities in PC-3M cells.

CONCLUSIONS

The present study provides the first evidence that silencing PSCA using siRNA can inhibit the proliferation and invasiveness properties of human CaP cells, which may provide a promising therapeutic strategy for CaP and open a novel avenue toward the investigation of the role of PSCA overexpression in cancers.

Prostate stem cell antigen: a Jekyll and Hyde molecule?

Prostate stem cell antigen (PSCA) is a glycosylphosphatidylinositol (GPI)-anchored cell surface protein. Although PSCA is thought to be involved in intracellular signaling, much remains unknown about its physiological function and regulatory mechanism in normal and cancer cells. It is up-regulated in several major cancers including prostate, bladder, and pancreatic cancers. The expression of PSCA is positively correlated with advanced clinical stage and metastasis in prostate cancers and is also associated with malignant progression of premalignant prostate lesions. Therefore, PSCA has been proposed as a biomarker of diagnosis and prognosis, as well as a target of therapy for these cancers. In addition, PSCA has also shown clinical potential in immunotherapy as a prostate-specific antigen, which, when presented by dendritic cells, may elicit strong tumor-specific immunity. In contrast, PSCA is down-regulated in esophageal and gastric cancer and may have a tumor-suppressing function in the gastric epithelium. Recent exciting findings that genetic variations of PSCA conferred increased risks of gastric cancer and bladder cancer have opened up a new avenue of research about the pathological function of PSCA. PSCA seems to be a Jekyll and Hyde molecule that plays differential roles, tumor promoting or suppressing, depending on the cellular context.

In vitro propagation and characterization of neoplastic stem/progenitor-like cells from human prostate cancer tissue

BACKGROUND

According to the cancer stem cell hypothesis, tumor growth is sustained by a subpopulation of cancer stem/progenitor-like cells. Self-renewal and high clonogenic potential are characteristics shared by normal stem and neoplastic stem/progenitor-like cells. We investigated whether human prostate cancer specimens contain cells with these properties.

METHODS

Self-renewal and clonogenic potential were assessed by serial passaging of spheres and colony formation, respectively. Gene expression was analyzed by real time PCR. Protein expression was detected by immunocytochemistry. The neoplastic nature of the cells was verified by detection of the TMPRSS2/ERG gene fusion expression.

RESULTS

The epithelial fraction isolated from surgical specimens generated colonies in 68% (19/28) of the patients. Laminin adhesion selected for cells with high clonogenic potential. The epithelial fraction from 85% (42/49) of the patients generated primary prostaspheres. Serial passaging of prostaspheres demonstrated their self-renewal capacity, which is also supported by their expression of the stem cell markers Oct-4, Nanog, Bmi-1, and Jagged-1 mRNA. Cells derived from prostaspheres were more clonogenic than the parental epithelial fraction. The pattern of mRNA expression in prostaspheres resembled that of the basal compartment of the prostate (CK5(+)/CK14(+)/CK19(high)/CK18(-/low)/c-met(+)/AR(-/low)/PSA(-/low)), but also included stem cell markers (CD49b(+)/CD49f(+)/CD44(+)/DeltaNp63(+)/Nestin(+)/CD133(+)). The distribution of marker expression in prostaspheres suggests their heterogeneous cell composition. Prostaspheres expressed significantly higher PSCA mRNA levels than the epithelial fraction.

CONCLUSION

Human prostate cancer specimens contain neoplastic cells with self-renewal and clonogenic potential, which can be enriched and perpetuated in prostaspheres. Prostaspheres should prove valuable for the identification of prostate cancer stem/progenitor-like cells.

Targeting of prostate cancer cells by a cytotoxic lentiviral vector containing a prostate stem cell antigen (PSCA) promoter

BACKGROUND

The efficacy of prostate cancer gene therapy is limited by the inefficiency of prostate-specific promoters as compared to ubiquitous viral promoters. The purpose of this investigation was to evaluate the specificity and efficacy of a lentiviral vector driven by a PSCA promoter.

METHODS

Prostate cancer (LNCap, C42-B, and LAPC-4) and non-prostate cancer (HeLa, MB231, and MCF-7) cells were transduced with a lentiviral vector expressing either the luciferase or the HSV-TK suicide gene and driven by a short PSCA promoter. Specificity and efficacy were evaluated in vitro and in vivo.

RESULTS

Luciferase expression was only detected in prostate cancer cells and was comparable to the universal CMV promoter. Luciferase expression in prostate cancer cells cultured with androgen was higher than that in cells cultured without androgen. In subsequent cytotoxicity experiments in which the luciferase marker gene was replaced with the HSV-TK gene, the lentiviral vector harboring the PSCA promoter induced cytotoxicity in prostate cancer cell lines while demonstrating a minimal effect on non-prostate cells. Cellular toxicity was correlated to increasing concentrations of the prodrug ganciclovir. Androgen had a positive effect on the cytotoxicity of this lentiviral construct. Intratumoral injection of prostate cancer xenografts with the lentiviral construct induced tumor growth inhibition versus saline controls.

CONCLUSION

Our results indicate that a lentiviral gene therapy vector driven by a short PSCA promoter can induce prostate-specific cellular toxicity in vivo and in vitro and may provide a strategy to selectively treat local and advanced metastatic prostate cancer. Prostate 69: 1422-1434, 2009. (c) 2009 Wiley-Liss, Inc.

Prostate stem cell antigen mRNA expression in preoperatively negative biopsy specimens predicts subsequent cancer after transurethral resection of the prostate for benign prostatic hyperplasia

BACKGROUND

Recent data showed that prostate stem cell antigen (PSCA) mRNA expression in transurethral resection of the prostate (TURP)-resected tissues predicted the subsequent prostate cancer after TURP in benign prostatic hyperplasia (BPH) patients with both PSA < 4.0 ng/ml and normal DRE findings. This study was to determine whether PSCA mRNA positivity in preoperatively negative prostatic biopsy samples from BPH men with PSA > 4.0 ng/ml and/or suspicious DRE findings had predictive performance following TURP.

MATERIALS AND METHODS

PSCA in situ hybridization was performed on negative prostatic biopsies taken before TURP from 166 enrolled symptomatic BPH patients, who were continuously followed for 5 years postoperatively. Predictive performance of PSCA mRNA for subsequent cancer onset was evaluated by univariate and multivariate Cox proportional hazards models with bootstrapping and concordance indices.

RESULTS

PSCA mRNA was detected in 42/166 (25.3%) of the preoperatively negative biopsy specimens, with a mean positive-labeling cells of 31.6%, in which 31 patients were identified as having subsequent PCa on follow-up. Of 124 patients with negative expression for PSCA mRNA none were subsequently diagnosed with PCa. The examination of Spearman's rank correlation coefficient showed that PSCA mRNA expression levels were positively and statistically correlated with higher Gleason score (r = 0.88, P < 0.001) and clinical T stage (r = 0.84, P < 0.001). A final multivariate Cox proportional hazards model demonstrated that only PSCA mRNA expression in negative prostatic biopsies was predictive of the subsequent cancer development after TURP (hazard ratio = 3.49; 95% CI: 2.02-4.75; P < 0.001), with the concordance index of 0.893.

CONCLUSIONS

This prospective study identifies PSCA mRNA in preoperatively negative prostatic biopsies as a significant predictor of subsequent cancer after TURP.

Immunohistochemical Expression of Prostate Stem Cell Antigen in Cystoprostatectomies with Incidental Prostate Cancer

High expression of Prostate Stem Cell Antigen (PSCA) has been shown to be associated with adverse prognostic features in clinically-diagnosed prostate cancer. The aim of this study is to analyze PSCA expression in cystoprostatectomies with incidental prostate carcinoma (PCa). PSCA expression was evaluated immunohistochemically in normal-looking epithelium (NEp), high-grade prostatic intraepithelial neoplasia (HGPIN) and pT2a Gleason score 6 acinar adenocarcinoma. The evaluation was carried out on 20 cystoprostatectomies (CyPs) with incidental PCa from men with bladder urothelial carcinoma (UC), and 20 radical prostatectomies (RPs) with hormonally untreated PCa from men with clinically detected PCa. Ki-67 was also investigated. The percentages of PSCA positive cells in HGPIN were significantly higher than in NEp (NEp: CyP, mean 2.92% ± standard deviation 6.26%; RP, 3.5% ± 6.46%. HGPIN: CyP, 13.67% ± 12.78%; RP, 14.67% ± 11.34%) (p<0.001). The proportions of positive cells in PCa were greater than in HGPIN (CyP, 20.25% ± 15.96%; RP, 22.58% ± 13.67%) (p0.001). For Ki-67 labeling, the proportions of positive nuclei in the CyPs significantly increased from NEp through HGPIN to PCa. A similar trend was seen in the RPs. In the CyPs the percentages of PSCA and Ki67 positive cells were lower than in the RPs, the differences between the CyP and RP compartments being not statistically significant. Our findings suggest that PSCA is a marker associated with neoplastic transformation of prostate cells, both in CyPs and RPs. However, there are no significant differences between CyPs with incidental prostate carcinoma and RPs with clinically diagnosed cancer.

Hoxb13 regulatory elements mediate transgene expression during prostate organogenesis and carcinogenesis

The prostate requires androgens for development and homeostasis. Prostate cancer shares this dependence, however progression to androgen-independence is common after androgen deprivation. There is considerable interest in achieving therapeutic gene expression after androgen ablation using prostate-specific promoters. Paradoxically, known prostate-restricted cis-regulatory elements are androgen dependent. Hoxb13 expression is restricted in adults to the prostate and colon, and robust Hoxb13 expression persists after castration. To locate regulatory elements conferring this expression pattern, a lacZ reporter was inserted into the Hoxb13 locus on a mouse genomic bacterial artificial chromosome. In transgenic mice, this construct recapitulated the Hoxb13 expression pattern, including expression after castration. Reporter gene activity was maintained during carcinogenesis in a prostate cancer model. Hoxb13 cis-regulatory elements provide a powerful tool to achieve androgen-independent transgene expression in the prostate and distal colon-specific expression in the gastrointestinal tract. These data establish a framework for high-resolution analyses of factors regulating Hoxb13.

Androgen ablation augments prostate cancer vaccine immunogenicity only when applied after immunization

BACKGROUND

Androgen ablation (AA) causes apoptosis of normal and neoplastic prostate cells. It is a standard treatment for advanced prostate cancer. Androgen ablation-mediated immunological effects include bone marrow hyperplasia, thymic regeneration, T and B cell lymphopoeisis and restoration of age-related peripheral T cell dysfunction. Androgens also regulate the transcription of several cytokines. Dendritic cells (DC) are the most potent antigen presenting cells that can activate antigen-specific naïve T cells. Despite myriad clinical trials involving DC-based prostate cancer immunotherapies, the effects of AA on DC function remain largely uncharacterized. Therefore, we investigated the effects of AA on DC and whether it could improve the efficacy of prostate cancer immunotherapy.

METHODS

Cytokine expression changes due to AA were quantified by multiplex ELISA. Flow cytometry was used to assess AA-mediated effects on DC maturation and expression of costimulatory markers. Mixed leukocyte reactions and cell-mediated lysis assays elucidated the role of androgens in DC function. The effect of AA on the efficacy of vaccination against a prostate tumor-associated antigen was tested using Elispot assays.

RESULTS

Androgen ablation increased dendritic cell maturation and costimulatory marker expression, but had no effect on DC costimulatory function. However, DC isolated from castrated mice increased the expression of key cytokines by antigen-experienced T cells while decreasing their expression in naïve cells. Finally, androgen ablation improved immune responses to vaccination only when applied after immunization.

CONCLUSION

Androgen ablation causes differential effects of DC on primary and secondary T cell responses, thus augmenting vaccine immunogenicity only when applied after immunization.

Prostate stem cell antigen: a prospective therapeutic and diagnostic target

The development of novel clinical tools to combat cancer is an intense field of research and recent efforts have been directed at the identification of proteins that may provide diagnostic, prognostic and/or therapeutic applications due to their restricted expression. To date, a number of protein candidates have emerged as potential clinical tools in the treatment of prostate cancer. Discovered over ten year ago, prostate stem cell antigen (PSCA) is a cell surface antigen that belongs to the Ly-6/Thy-1 family of glycosylphosphatidylinositol-anchored proteins. PSCA is highly overexpressed in human prostate cancer, with limited expression in normal tissues, making it an ideal target for both diagnosis and therapy. Several studies have now clearly correlated the expression of PSCA with relevant clinical benchmarks, such as Gleason score and metastasis, while others have demonstrated the efficacy of PSCA targeting in treatment through various modalities. The purpose of this review is to present the current body of knowledge about PSCA and its potential role in the treatment of human prostate cancer.

[Identification of human salivary stem cells from cultured labial minor salivary cells]

Stem cell therapy is expected to be a promising approach for the compensation of lost organs. The various organization cells that compose an animal's body are always being renewed for the maintenance of homeostasis. The cells that become the source of new cells are a body's own stem cells. Cell therapy, using stem cells, has a few of bioethical problems but there is the advantage that it is not necessary to worry about the immunity rejection of the transplant because the body's stem cell is from it's own body. In our present study we identified side population cells (SP cells), which are highly enriched for stem cell activity in human salivary glands. Isolated SP cells expressed high level of DNp63 and PSCA (prostate stem cell antigen), but not nestin, Oct4 and CD34. Real time PCR analysis revealed that the expression of DNp63, detected in immature salivary epithelial cells, gradually decreased through cell differentiation. In contrast, PSCA can be distinguished among early differentiating and later transit-amplifying salivary epithelial cells in tissue culture. Our study suggested that these markers may mark the transition of human salivary epithelial cells.

Flutamide reduced prostate cancer development and prostate stem cell antigen mRNA expression in high grade prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (HGPIN) appears to represent an ideal target for chemoprevention of prostate cancer (PCa). HGPIN responds to androgen ablation and has prostate stem cell antigen (PSCA) mRNA expression. One hundred and seventy two patients with isolated HGPIN were randomized in a double-blind manner to receive flutamide 250 mg/day (86 cases) or a placebo (86 cases) for 12 months and were rebiopsied at 12 and 60 months. PSCA mRNA expression was assessed in the prestudy and 12-month biopsies by in situ hybridization. The incidence of subsequent PCa was 11.6% in the flutamide group when compared with 30.2% in the placebo group over a follow-up period of 5 years (p = 0.0027). PSCA mRNA expression levels were significantly declined after treatment compared with that before treatment (p < 0.001). After treatment, 66 patients had reduced PSCA mRNA expression, in whom none was found with cancer on follow-up, however, 13 cases had increased PSCA mRNA expression levels, in whom 11 were found with cancer. Cox regression analysis demonstrated that HGPIN with increased PSCA mRNA expression after flutamide had an increased relative risk of 4.33 to develop subsequent cancer (95% confidence intervals: 2.48-7.36; p < 0.001). Seventeen (19.8%) cases had the flutamide-associated side effects, which were graded as mild, but all did not discontinue study. Flutamide can effectively and safely reduce PCa development and significantly suppress PSCA mRNA expression in men with isolated HGPIN, whereas the increased PSCA mRNA expression after therapy may be a clinically adverse predictor for cancer onset.

Deletion of PSCA increases metastasis of TRAMP-induced prostate tumors without altering primary tumor formation

BACKGROUND

Prostate stem cell antigen (PSCA) is expressed in normal epithelium of various tissues, in embryos and adult animals. PSCA expression is upregulated in up to 70% of prostate tumors and metastases, and a subset of bladder and pancreatic cancers. However, its function is unknown. We studied the effect of targeted gene deletion of PSCA on normal organ development and prostate carcinogenesis.

METHODS

PSCA +/+, PSCA +/-, and PSCA -/- mice were bred and aged to 22 months. A cohort of animals was treated with gamma-irradiation at 2 and 6 months of age. PSCA knockout mice were crossed to TRAMP mice and TRAMP+ PSCA +/+, TRAMP+ PSCA +/-, and TRAMP+ PSCA -/- mice and offspring aged to 10 months of age. Tissues were analyzed by RT-PCR, histology, and immunohistochemistry for markers of proliferation, apoptosis, angiogenesis, and tumor progression.

RESULTS

PSCA knockout animals were viable, fertile and indistinguishable from wild-type littermates. Spontaneous or radiation-induced primary epithelial tumor formation was also similar in wild-type and PSCA knockout mice. We observed an increased frequency of metastasis in TRAMP+ PSCA heterozygous and knockout mice, compared to TRAMP+ wild-type mice. Metastases were largely negative for PSCA and androgen receptor. Cleaved-caspase 3 and CD31 staining was similar in all genotypes. Aurora-A and Aurora-B kinases were detected in the cytoplasm of PSCA heterozygous and knockout tumors, suggesting aberrant kinase function.

CONCLUSION

These data suggest that PSCA may play a role in limiting tumor progression in certain contexts, and deletion of PSCA may promote tumor migration and metastasis.

The association of prostate stem cell antigen (PSCA) mRNA expression and subsequent prostate cancer risk in men with benign prostatic hyperplasia following transurethral resection of the prostate

BACKGROUND

Prior data showed prostate stem cell antigen (PSCA) mRNA expression in benign prostatic hyperplasia (BPH) tissues. The purpose of the present investigation was to determine whether PSCA mRNA expression in resected BPH samples was associated with the subsequent presence of cancer following transurethral resection of the prostate (TURP).

METHODS

PSCA in situ hybridization was performed on the TURP-resected tissues from 288 patients, who were histopathologically confirmed BPH without cancer. All these patients were continuously followed for 9-70 months postoperatively. Univariate and multivariate cox regression analyses were used to evaluate the predictive performance of PSCA mRNA for subsequent cancer onset following TURP.

RESULTS

PSCA mRNA was detected in 93/288 (32.3%) of the resected BPH specimens, with a mean positive-labeling cells of 23.8%, in which 22 patients (23.7%) were identified as having PCa on follow-up. Of 195 patients with negative expression for PSCA mRNA 2 (1.0%) were subsequently found with PCa. PSCA mRNA expression levels were directly proportional to higher Gleason score and clinical T stage. Univariate and multivariate cox regression analyses demonstrated that only PSCA mRNA expression was predictive of the subsequent cancer development after TURP, however, PSA velocity was an univariately significant but not multivariately significant predictor.

CONCLUSIONS

This prospective study identifies PSCA mRNA in BPH as a significant predictor of cancer development after TURP, suggesting that PSCA may be used to identify patients who are at high risk for subsequent cancer onset following TURP for BPH and the PSCA test may be useful when applied for repeat biopsies.

Reverse transcriptase-polymerase chain reaction and immunohistochemical studies for detection of prostate stem cell antigen expression in prostate cancer: potential value in molecular staging of prostate cancer

OBJECTIVES

To determine whether detection of prostate stem cell antigen (PSCA) expression has potential for molecular staging in prostate cancer (PCa), we examined the relationship between established prognostic factors, biochemical recurrence (BCR) and PSCA expression.

METHODS

This study was comprised of 66 patients who underwent radical prostatectomy for the treatment of PCa. We employed reverse transcriptase-polymerase chain reaction (RT-PCR) to detect PSCA mRNA-bearing cells in peripheral blood, and used immunohistochemical (IHC) techniques to identify PSCA protein expression in microarrayed tissue.

RESULTS

PSCA-mRNA was detected in the peripheral blood of nine (13.6%) patients by RT-PCR. Whereas 3.2% of patients with low-grade disease were PSCA positive, 22.9% of patients with high-grade disease were PSCA positive (P = 0.030). There was also a significant relationship of RT-PCR PSCA positivity to whether or not the tumor was confined to the prostate. Whereas only 6.8% of patients with prostate-confined disease were RT-PCR PSCA positive, 27.3% of extraprostatic diseases were RT-PCR PSCA positive (P = 0.022). IHC studies of tumor tissue microarrays demonstrated that PSCA expression intensity was related to both extraprostatic extension (P = 0.014) and positive surgical margin (P = 0.053). Whereas 23.8% of prostate-confined diseases were high intensity, 54.5% of extraprostatic diseases were high intensity. BCR developed in seven patients (10.6%) during the follow-up period (median, 16.2 months; range, 9-25 months). Prognostic factors increasing the risk of BCR included: seminal vesicle invasion (P = 0.004), extraprostatic disease (P = 0.019), lymphovascular emboli (P = 0.036) and RT-PCR PSCA positivity (P = 0.004) in univariate analysis.

CONCLUSIONS

We were able to detect PSCA mRNA-bearing cells in peripheral blood by RT-PCR, and also identify PSCA protein expression in tumors by IHC analysis of tissue microarrays. RT-PCR PSCA positivity in peripheral blood may be a potential modality for molecular staging of PCa.

Prostate stem cell antigen (PSCA) mRNA expression in prostatic intraepithelial neoplasia: implications for the development of prostate cancer

BACKGROUND

Prior data clearly demonstrated the expression of prostate stem cell antigen (PSCA) mRNA in prostatic intraepithelial neoplasia (PIN) tissues. The purpose of the present investigation was to determine whether PSCA mRNA expression was associated with the presence of cancer in this disease.

METHODS

One hundred seventeen men were diagnosed with isolated PIN on initial prostate biopsy, 51 with low-grade form (LGPIN), and 66 with high-grade form (HGPIN). PSCA mRNA expression in initial PIN and subsequent cancer was examined by in situ hybridization (ISH). The differences of the PSCA mRNA expression level between the groups were analyzed by the Chi-square and Student's t-test. Univariate and multivariate logistic regression analyses were performed to evaluate the predictive performance of PSCA mRNA.

RESULTS

PSCA mRNA expression level in 34 subsequent cancers was statistically increased compared with their paired PIN (P < 0.001), with a Gleason's dependence. HGPIN showed statistically high PSCA mRNA expression compared with LGPIN (P < 0.01). PSCA mRNA expression levels were significantly stronger in the initial isolated LGPIN and isolated HGPIN with subsequent cancer than those without (P < 0.001 and P < 0.001, respectively). Multivariate logistic regression analysis demonstrated that only PSCA mRNA was predictive of the onset of subsequent cancer in patients with isolated LGPIN and in those with isolated HGPIN, respectively.

CONCLUSIONS

Our data identify PSCA mRNA in initial PIN as a significant predictor of subsequent cancer, suggesting that PSCA implies in prostatic tumorigenesis and may be used to identify the patients with isolated PIN who are at high risk for cancer onset in the disease process.

Self-renewal and multilineage differentiation in vitro from murine prostate stem cells

Murine prostate stem cells express integrin alpha 6, which modulates survival, proliferation, and differentiation signaling through its interaction with the extracellular protein laminin. When plated in vitro in laminin containing Matrigel medium, 1 of 500-1,000 murine prostate cells can grow and form clonogenic spheroid structures that we term prostate spheres. Prostate spheres can be serially passaged individually or in bulk to generate daughter spheres with similar composition, demonstrating that sphere-forming cells are capable of self-renewal. Spheres spontaneously undergo lineage specification for basal and transit-amplifying cell types. P63-expressing cells localized to the outer layers of prostate spheres possess higher self-renewal capacity, whereas cells toward the center display a more differentiated transit-amplifying phenotype, as demonstrated by the expression of the prostate stem cell antigen. When dihydrotestosterone is added to the medium, the androgen receptor is stabilized, is imported to the nucleus, and drives differentiation to a luminal cell-like phenotype. A fraction of sphere cells returned to an in vivo environment can undergo differentiation and morphogenesis to form prostate tubular structures with defined basal and luminal layers accompanied by prostatic secretions. This study demonstrates self-renewal and multilineage differentiation from single adult prostate stem/progenitor cells in a specific in vitro microenvironment.

External beam radiotherapy (EBRT) suppressed prostate stem cell antigen (PSCA) mRNA expression in clinically localized prostate cancer

BACKGROUND

Prostate stem cell antigen (PSCA), a recently identified glycosylphosphatidylinositol (GPI)-anchored cell surface protein belonging to the Thy-1/Ly-6 family of cell surface antigens, is overexpressed in human prostate cancer (PCa). Our recent data indicated that complete androgen ablation could significantly suppress PSCA mRNA expression in primarily organ-confined PCa. The effect of external beam radiotherapy (EBRT), one of the curative treatment options for localized PCa, on tumor PSCA mRNA expression has not been elucidated. The purpose of the present study was to investigate the variations in the expression levels of PSCA mRNA before and after EBRT, and further evaluate the prognostic value of PSCA in this disease.

MATERIALS AND METHODS

Between January 1999 and June 2005, 87 men with clinically localized adenocarcinoma of the prostate received only EBRT with a total dose of 65-70 Gy for 6.5-7 weeks. PSCA in situ hybridization (ISH) was performed on the cancerous pretreatment biopsy or transurethral resection of prostate (TURP) tissue and post-treatment biopsy tissue of all 87 men, respectively. Tumor cytoplasmic staining of PSCA mRNA was evaluated by two independent pathologists and the differences of PSCA mRNA expression levels between the samples before and after EBRT were analyzed using the Student's t-test. Twenty-four to seventy months continuous follow-up studies after treatment were performed and aimed at assessing the correlation of PSCA mRNA expression level with biochemical relapse and/or distant metastases from the cancer.

RESULTS

The percent of cells positive for PSCA mRNA by ISH labeling declined from 71.2% (0-93%) +/- 9.7% before EBRT to 30.7% (0-90%) +/- 5.3% after EBRT (P<0.001). Before EBRT, 81 of 87 cases (93.1%) were positive for PSCA mRNA labeling, however, after EBRT the percentage of positive reactivity of PSCA mRNA was decreased to 62 of 81 cases (76.5%), in which 59 men (95.2%) were found without biochemical relapse or distant metastases on follow-up. This decline in PSCA mRNA labeling was directly proportional to higher pretreatment serum PSA level, higher tumor grade (Gleason score), and higher clinical T stage. The rest 19 cases had the increased percentage of cells positive for PSCA mRNA after EBRT, in which 15 cases developed biochemical relapse and/or distant metastases from tumor on follow-up.

CONCLUSIONS

We found that EBRT for PCa can significantly suppress PSCA mRNA expression and the elevated PSCA mRNA level after EBRT may be a clinically adverse predictor for tumor progression.

Gene expression profiling in R-flurbiprofen-treated prostate cancer: R-Flurbiprofen regulates prostate stem cell antigen through activation of AKT kinase

We have used gene expression profiling to characterize genes regulated by the anti-tumor non-steroidal anti-inflammatory drug (NSAID)-like agent R-flurbiprofen (RFB) in murine TRAMP prostate cancer. Mice with spontaneous, palpable tumors were treated with RFB 25 mg/(kgd) x 7d orally, or vehicle only. RNA was then extracted from tumor tissue and used for microarray analysis with Affymetrix chips. Fifty-eight genes were reproducibly regulated by RFB treatment. One of the most highly up-regulated genes was prostate stem cell antigen (psca). We used TRAMP C1 murine prostate cancer cells to examine potential mechanisms through which RFB could regulate psca. RFB induced dose-dependent expression of PSCA protein, and activity of the psca promoter, in TRAMP C1 cells in culture. Increased psca promoter activity was also seen following treatment of cells with sulindac sulfone, another NSAID-like agent, but not with celecoxib treatment. RFB activation of the psca promoter could be attenuated by co-transfection of dominant-negative akt and h-ras constructs, but not by dominant-negative mek1 plasmids. Immunoblotting revealed that RFB increased expression of phosphorylated AKT at concentrations that stimulated psca promoter activity, and that increased PSCA protein expression. In addition, RFB-dependent up-regulation of PSCA protein expression could be blocked by AKT inhibitors. These data demonstrate that RFB, and possibly other NSAID-like analogs, can increase expression of the psca gene both in vivo and in culture. They further suggest the utility of combining RFB with AKT inhibitors or with monoclonal antibodies targeting PSCA protein, for treatment or prevention of prostate cancer.

The expression of prostate stem cell antigen in human clear cell renal cell carcinoma: a quantitative reverse transcriptase-polymerase chain reaction analysis

OBJECTIVES

To analyse the gene expression level of prostate stem cell antigen (PSCA) in human clear cell renal cell carcinoma (CC-RCC) and its relationship with conventional clinicopathological manifestations, to evaluate its prognostic value for patient outcome, and to determine the effect of PSCA on the progression of CC-RCC.

PATIENTS AND METHODS

We quantified PSCA mRNA level in human RCC cell lines (ACHN, A704, KPK-1, Caki-1, and Caki-2) and in 154 surgical tissue samples (81 from CC-RCC, 73 from normal kidney) using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The findings were analysed in relation to clinicopathological factors. Immunohistochemical expression was examined using confocal laser scanning light-microscopy.

RESULTS

PSCA was overexpressed in all RCC cell lines. PSCA mRNA levels were significantly higher in CC-RCC than in normal kidney tissue samples (P < 0.001), in G2-G3 than in G1 tumours (P = 0.028), and in advanced disease (T3-T4) than in organ-confined (T1-T2) tumours (P = 0.016). There was significantly higher PSCA mRNA expression in patients with M1 than in those with M0 disease (P = 0.029). Patients in whom the lesions had high PSCA expression levels had a significantly worse prognosis than those with low PSCA expression levels (P = 0.044). Using immunohistochemical analysis there was markedly greater PSCA expression in CC-RCC than in normal kidney, and in advanced-disease high-grade tumours than in organ-confined low-grade tumours.

CONCLUSIONS

A significant correlation was detected in the gene expression level of PSCA with histological grade, clinicopathological stage and prognosis in CC-RCC. Our data indicate that PSCA is associated with carcinogenesis and progression of CC-RCC.

Monitoring the antitumor response of naive and memory CD8 T cells in RAG1-/- mice by positron-emission tomography

Therapeutic antitumor immunity depends on a highly migratory CTL population capable of activation and trafficking between lymphoid and tumor-bearing microanatomic sites. We recently adapted positron-emission tomography gene expression imaging for noninvasive, longitudinal localization and quantitation of antitumor T lymphocyte migration in vivo. In this study, we apply this system to enumerate the temporal accumulation of naive vs memory T cells. Naive or memory OT-1 CD8(+) T cells, retrovirally marked with the sr39TK gene, were adoptively transferred into RAG1(-/-) animals bearing EL-4 or EG.7 (an OVA-expressing subline), and repetitively imaged by microPET over several weeks. Memory cells demonstrated early accumulation and apparent proliferation, with large T cell numbers at the Ag-positive tumor as early as day 1 after T cell transfer. Naive T cells did not accumulate in the E.G7 tumor until day 8, and reached only 25% of the peak levels achieved by memory T cells. Both naive and memory cells eradicated the Ag-expressing tumor at a comparable density of intratumoral T cells (2-4 x 10(6)/g). However, due to the slower rate of T cell expansion and continued tumor growth, naive cells required approximately 10-fold higher Ag-specific precursor frequency to reach a tumoricidal cell density. As recently reported, memory but not naive T cells accumulated in local lymph nodes and lungs, where they persisted as a resident population after tumor eradication. Positron-emission tomography-based immunologic imaging is a noninvasive modality providing unique and meaningful information on the dynamics of the antitumor CTL response.

Notch signaling is required for normal prostatic epithelial cell proliferation and differentiation

Notch pathway is crucial for stem/progenitor cell maintenance, growth and differentiation in a variety of tissues. Using a transgenic cell ablation approach, we found in our previous study that cells expressing Notch1 are crucial for prostate early development and re-growth. Here, we further define the role of Notch signaling in regulating prostatic epithelial cell growth and differentiation using biochemical and genetic approaches in ex vivo or in vivo systems. Treatment of developing prostate grown in culture with inhibitors of gamma-secretase/presenilin, which is required for Notch cleavage and activation, caused a robust increase in proliferation of epithelial cells co-expressing cytokeratin 8 and 14, lack of luminal/basal layer segregation and dramatically reduced branching morphogenesis. Using conditional Notch1 gene deletion mouse models, we found that inactivation of Notch1 signaling resulted in profound prostatic alterations, including increased tufting, bridging and enhanced epithelial proliferation. Cells within these lesions co-expressed both luminal and basal cell markers, a feature of prostatic epithelial cells in predifferentiation developmental stages. Microarray analysis revealed that the gene expression in a number of genetic networks was altered following Notch1 gene deletion in prostate. Furthermore, expression of Notch1 and its effector Hey-1 gene in human prostate adenocarcinomas were found significantly down-regulated compared to normal control tissues. Taken together, these data suggest that Notch signaling is critical for normal cell proliferation and differentiation in the prostate, and deregulation of this pathway may facilitate prostatic tumorigenesis.

Validation of molecular targets in prostate cancer

As prostate cancer is not a single disease, it is important to identify the pivotal pathway in the patient being treated. The molecular environment is the site of current oncological research to define new therapeutic targets for hormone-refractory disease, offering the potential to eventually individualize treatment through stratification of pathways. Targets may be validated either phenotypically (e.g. androgen receptor, cadherin) or functionally (e.g. prostate cancer-specific genes). In addition, several other candidates are potentially suitable, while others await discovery. Important initial steps have been made in the search for prostate cancer stem cells; identifying stem cells and the stromal, hormonal, and other signalling molecules that influence their behaviour would have important implications for managing prostate cancer. Although individual therapeutic pathways might be ineffective in a particular molecular environment, combinations of approaches might be capable of producing synergistic effects. A multimodal approach thus might be the best solution. Determining where best to search for a molecular target, and validating whether the target is associated with a sufficiently aggressive malignant process to justify further study is difficult, but the potential benefits are enormous.

Complete androgen ablation suppresses prostate stem cell antigen (PSCA) mRNA expression in human prostate carcinoma

BACKGROUND

Prostate stem cell antigen (PSCA) is a recently identified glycosylphosphatidylinositol (GPI)-anchored cell surface protein belonging to the Thy-1/Ly-6 family of cell surface antigens. Prior data in prostate cancers indicated that PSCA is directly regulated by androgens and PSCA expression increases with high-tumor grade, advanced stage, extracapsular invasion, and androgen-independent progression. The effect of complete androgen ablation (CAA) on tumor PSCA mRNA expression has not been elucidated. The purpose of the present study was to investigate the variations in the expression levels of PSCA mRNA before and after CAA, and further evaluate the clinically prognostic value of PSCA in human prostate carcinoma.

MATERIALS AND METHODS

PSCA in situ hybridization (ISH) was performed on the cancerous pretreatment biopsy or transurethral resection of prostate (TURP) tissue of 42 men with primarily organ-confined prostate cancer before CAA, and on their tumor tissue from radical retropubic prostatectomy after CAA with bicalutamide and goserelin acetate for 3 months prior to undergoing radical prostatectomy. Tumor cytoplasmic staining of PSCA mRNA was evaluated by two independent pathologists and the differences of PSCA mRNA expression levels between the samples before and after CAA were analyzed using the Student's t-test. Thirty-six to forty months follow-up studies after radical retropubic prostatectomy were performed and aimed at assessing the correlation of PSCA mRNA expression level with local recurrences or metastases from the cancer.

RESULTS

The percent of cells positive for PSCA mRNA by ISH labeling declined from 67.3% (0-89%)+/-9.4% before CAA to 33.8% (0-92%)+/-7.7% after CAA (P<0.001). Before CAA, 40 of 42 cases (95.2%) were positive for PSCA mRNA labeling, however, after CAA the percentage of positive reactivity of PSCA mRNA was decreased to 27 of 40 cases (67.5%), in which none was found with local recurrences or distant metastases after radical prostatectomy on follow-up. This decline in PSCA mRNA labeling was dependent on the original tumor grade with Gleason score of <or=6: 19.3%+/-4.7%, Gleason score of 7: 38.8%+/-7.2%, and a Gleason score of >or=8: 73.4%+/-13.8% (P<0.05, respectively). The rest 13 cases had the increased percentage of cells positive for PSCA mRNA after CAA, in which 3 cases were found with local recurrences and 4 cases with distant metastases from tumor on follow-up.

CONCLUSIONS

Our data demonstrate that CAA for prostate cancer can suppress PSCA mRNA expression with a tumor grade dependence and the increased expression of PSCA mRNA after CAA may be a clinically adverse predictor for tumor recurrences or distant metastases.

Prostate stem cell antigen is a putative target for immunotherapy in pancreatic cancer

The prostate stem cell antigen (PSCA) is a glycosylphosphatidyl-inositol (GPI)-linked cell surface antigen expressed in normal prostate and overexpressed in the majority of prostate cancers and correlates with tumor grade and disease stage. Because PSCA has been described to be up-regulated in pancreatic cancer, the purpose was to evaluate the expression of PSCA in human pancreatic cancer. Furthermore, the therapeutic efficacy of a monoclonal anti-PSCA antibody in an in vivo pancreatic cancer model was determined.

METHODS

The expression of PSCA in human pancreatic cancer tissues was determined and compared with chronic pancreatitis and normal pancreas by quantitative reverse transcriptase-polymerase chain reaction. Therapeutic efficacy of the monoclonal anti-PSCA antibody 1G8 was examined in Capan-1 pancreatic tumors grown as subcutaneous grafts in athymic nude mice.

RESULTS

PSCA was strongly up-regulated in human pancreatic cancer compared with chronic pancreatitis and normal pancreas. In addition, the PSCA protein was expressed on the cell surface of pancreatic cancer cells. Treatment with 1G8 significantly reduced tumor growth initiation in an in vivo pancreatic cancer xenograft model. In addition, antibody treatment of established tumors reduced tumor progression.

CONCLUSIONS

These results show a potential therapeutic role for anti-PSCA antibodies in the treatment of pancreatic cancer. Furthermore, PSCA might serve as a novel marker in the diagnosis of pancreatic cancer.

The Sca-1 cell surface marker enriches for a prostate-regenerating cell subpopulation that can initiate prostate tumorigenesis

Sca-1 (stem cell antigen-1) enriches for murine prostate cells capable of regenerating tubular structures containing basal and luminal cell lineages in a dissociated cell prostate regeneration system. Sca-1(+) fractions are enriched for cells at the G(0) stage of the cell cycle, and Sca-1(+) cells cluster in the proximal region of prostatic tubules where replication-quiescent cells have been localized. Castration-induced enrichment for androgen-independent cells results in a concomitant enrichment for Sca-1(+) cells. Genetic perturbations of PTEN/AKT signaling in prostate-regenerating cells leads to the initiation of tumorigenesis, and cancer progression is associated with a dramatic increase in Sca-1(+) cells. Sca-1-enriched prostate-regenerating cells possess multiple stem/progenitor cell properties and can serve as targets for cancer initiation.

Knockin of SV40 Tag oncogene in a mouse adenocarcinoma of the prostate model demonstrates advantageous features over the transgenic model

Prostate cancer (CaP) is the most common cancer in adult men in North America. Since there is no naturally occurring prostate cancer in the mouse, preclinical studies stipulate for the establishment of a genetically manipulated mouse CaP model with features close to the human situation. In view of the limitations of transgenic technique-derived CaP models, herein we report the first application of knockin technology to establish a new mouse adenocarcinoma prostate model (PSP-KIMAP) by targeting of SV40 Tag to a prostate tissue-specific gene, PSP94 (prostate secretory protein of 94 amino acids). In order to demonstrate its novelty, we compared KIMAP to a PSP94 gene-directed transgenic mouse adenocarcinoma of the prostate (PSP-TGMAP) model. The CaP development of the PSP-KIMAP mice started almost immediately after puberty at 10 weeks of age from mouse prostatic intraepithelial neoplasia (mPIN) with microinvasion to well-differentiated CaP, and demonstrated a close-to-human kinetics of prolonged tumor growth and a predominance of well and moderately differentiated tumors. The invasive nature of KIMAP model was demonstrated by multitissue metastases (lymph node, lung and liver etc) and also by immunohistochemical study of multiple invasive prostate tumor markers. PSP-KIMAP model is responsive to androgen deprivation (castration). The knockin technology in our KIMAP model demonstrates highly predictive CaP development procedures and many advantageous features, which the traditional transgenic technique-derived CaP models could not reach for both basic and clinical studies. These features include the high stability of both phenotype and genotype, highly synchronous prostate cancer development, high and precise prostate tissue targeting and with no founder line variation. The differences between the two CaP models were attributed to the introduction of a single endogenous knockin mutation, resulting in a CaP model self-regulated and controlled by a prostate gene promoter/enhancer of PSP94.

Prostate stem cell antigen (PSCA) expression in human prostate cancer tissues: implications for prostate carcinogenesis and progression of prostate cancer

OBJECTIVE

Prostate stem cell antigen (PSCA) is a recently defined homolog of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. The objective of the present study was to examine the expression status of PSCA protein and mRNA in clinical specimens of human prostate cancer (PCa) and to validate it as a potential molecular target for diagnosis and treatment of PCa.

METHODS

Immunohistochemical (IHC) and in situ hybridization (ISH) analyses of PSCA expression were simultaneously performed on paraffin-embedded sections of 20 benign prostatic hyperplasia (BPH), 20 prostatic intraepithelial neoplasm (PIN) and 48 prostate cancer (PCa) tissues, including 9 androgen-independent prostate cancers. The level of PSCA expression was semiquantitatively scored by assessing both the percentage and intensity of PSCA-positive staining cells in the specimens. We then compared the PSCA expression between BPH, PIN and PCa tissues and analyzed the correlations of PSCA expression level with pathological grade, clinical stage and progression to androgen-independence in PCa.

RESULTS

In BPH and low grade PIN, PSCA protein and mRNA staining were weak or negative and less intense and uniform than that observed in high grade PIN (HGPIN) and PCa. Moderate to strong PSCA protein and mRNA expression were noted in 8 of 11 (72.7%) HGPIN and in 40 of 48 (83.4%) PCa specimens examined by IHC and ISH analyses, and their statistical significance was compared with BPH (20%) and low-grade PIN (22.2%) specimens (P < 0.05). The expression level of PSCA increased with a higher Gleason grade, advanced stage and progression to androgen-independence (P < 0.05). In addition, IHC and ISH staining revealed a high degree of correlation between PSCA protein and mRNA overexpression.

CONCLUSIONS

Our data demonstrate that PSCA as a new cell surface marker is overexpressed in a majority of cases of human PCa. PSCA expression correlates positively with adverse tumor characteristics, such as increasing pathological grade (poor cell differentiation), worsening clinical stage and androgen-independence and speculatively with prostate carcinogenesis. PSCA may possess prognostic utility and may be a promising molecular target for diagnosis and treatment of PCa.

Prostate stem cell antigen (PSCA) expression in human prostate cancer tissues and its potential role in prostate carcinogenesis and progression of prostate cancer

BACKGROUND

Prostate stem cell antigen (PSCA) is a recently defined homologue of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. The purpose of the present study was to examine the expression status of PSCA protein and mRNA in clinical specimens of human prostate cancer (Pca) and to validate it as a potential molecular target for diagnosis and treatment of Pca.

MATERIALS AND METHODS

Immunohistochemical (IHC) and in situ hybridization (ISH) analyses of PSCA expression were simultaneously performed on paraffin-embedded sections from 20 benign prostatic hyperplasia (BPH), 20 prostatic intraepithelial neoplasm (PIN) and 48 prostate cancer (Pca) tissues, including 9 androgen-independent prostate cancers. The level of PSCA expression was semiquantitatively scored by assessing both the percentage and intensity of PSCA-positive staining cells in the specimens. Then compared PSCA expression between BPH, PIN and Pca tissues and analysed the correlations of PSCA expression level with pathological grade, clinical stage and progression to androgen-independence in Pca.

RESULTS

In BPH and low grade PIN, PSCA protein and mRNA staining were weak or negative and less intense and uniform than that seen in HGPIN and Pca. There were moderate to strong PSCA protein and mRNA expression in 8 of 11 (72.7%) HGPIN and in 40 of 48 (83.4%) Pca specimens examined by IHC and ISH analyses, with statistical significance compared with BPH (20%) and low grade PIN (22.2%) samples (p < 0.05, respectively). The expression level of PSCA increased with high Gleason grade, advanced stage and progression to androgen-independence (p < 0.05, respectively). In addition, IHC and ISH staining showed a high degree of correlation between PSCA protein and mRNA overexpression.

CONCLUSIONS

Our data demonstrate that PSCA as a new cell surface marker is overexpressed by a majority of human Pca. PSCA expression correlates positively with adverse tumor characteristics, such as increasing pathological grade (poor cell differentiation), worsening clinical stage and androgen-independence, and speculatively with prostate carcinogenesis. PSCA protein overexpression results from upregulated transcription of PSCA mRNA. PSCA may have prognostic utility and may be a promising molecular target for diagnosis and treatment of Pca.

Prostate Stem Cell Antigen Expression is Associated With Gleason Score, Seminal Vesicle Invasion and Capsular Invasion in Prostate Cancer

PURPOSE

Few successful therapeutic options exist for men who present with metastatic prostate cancer (CaP) or for the 30% with recurrence. The development and characterization of molecular markers are vital to the development of prognostic and therapeutic modalities in CaP. We investigated the expression and potential clinical usefulness of prostate stem cell antigen (PSCA) in CaP using tissue microarrays.

MATERIALS AND METHODS

Immunohistochemical analysis using a PSCA monoclonal antibody was performed on tissue microarrays constructed from paraffin embedded specimens from 246 patients who underwent radical retropubic prostatectomy. PSCA staining was correlated with established prognostic factors, such as Gleason score, prostate specific antigen (PSA), and seminal vesicle invasion. In addition, recurrence-free survival was analyzed.

RESULTS

A high PSCA intensity of 3 was associated with adverse prognostic features, such as Gleason score 7 and above (p = 0.001), seminal vesicle invasion (p = 0.005) and capsular involvement (p = 0.033). On univariate analysis tumors with a PSCA intensity of 3 carried an increased risk of PSA recurrence (p = 0.031, HR 1.77, 95% CI 1.05 to 2.96). However, after adjusting for these variables a PSCA intensity of 3 was no longer an independent predictor of PSA recurrence.

CONCLUSIONS

We found that high PSCA intensity is significantly associated with adverse prognostic features such as high Gleason score and extra-organ disease. The results of this study suggest that PSCA is a promising tumor marker for the selection of patients at high risk but additional studies are necessary to assess the usefulness of PSCA in patient biopsies.

Immunocytochemical analysis of prostate stem cell antigen as adjunct marker for detection of urothelial transitional cell carcinoma in voided urine specimens

PURPOSE

Prostate stem cell antigen (PSCA), a homologue of the Ly-6/Thy-1 family of cell surface antigens, has been shown to be increased in a majority of human transitional cell carcinomas. We tested the possibility of using PSCA as an adjunct marker for urine cytology.

MATERIALS AND METHODS

Immunocytochemical analysis was performed on 44 archived voided urine samples obtained from 3 groups of patients based on initial voided urine cytological results and subsequent followup biopsy findings. Group 1 (14 of 44 patients) had positive findings on cytology and histology, group 2 (16 of 44) had negative cytology but positive histology, and group 3 (14 of 44) had negative findings on cytology and histology. Cytological slides prepared from 10 fresh voided urine samples were also analyzed. Papanicoloau stained archived urine slides were de-stained and re-stained immunocytochemically with a monoclonal antibody against PSCA. Immunofluorescence followed by laser scanning cytometer analysis was also performed on archived slides from 2 representative cases.

RESULTS

Sensitivity and specificity were 46.7% and 100% for cytology alone, respectively, and 80% and 85.7% for PSCA alone, respectively. PSCA immunostaining was positive in 92.8% group 1, 68.8% group 2 and only 14.3% group 3 samples. The difference in positive PSCA findings in groups 2 and 3 were statistically significant at p <0.01 by chi-square test. Whereas some superficial umbrella cells showed slight staining by immunocytochemistry, it was feasible to distinguish the expression levels between tumor and normal superficial umbrella cells quantitatively using immunofluorescence coupled with laser scan cytometry analysis.

CONCLUSIONS

Immunocytochemical analysis of PSCA on archived voided urine samples may provide a simple and quantitative adjunct marker for cytological diagnosis of urothelial carcinoma.

Identification of an androgen-dependent enhancer within the prostate stem cell antigen gene

Prostate stem cell antigen (PSCA) is emerging as an important diagnostic marker and therapeutic target in prostate cancer. Previous studies indicated that PSCA was directly regulated by androgens, but the mechanism has not been elucidated. Here we describe the identification of a compact cell-specific and androgen-responsive enhancer between 2.7 and 3 kb upstream of the transcription start site. The enhancer functions autonomously when positioned immediately adjacent to a minimal promoter. Deoxyribonuclease I footprinting analysis with recombinant androgen receptor (AR) reveals that the enhancer contains two AR binding sites at one end. Mutational analysis of the AR binding sites revealed the importance of the higher affinity one. The dissociation constant of the high affinity binding site (androgen response element I) was determined to be approximately 87 nM. The remainder of the enhancer contains elements that function synergistically with the AR. We discuss the structural organization of the PSCA enhancer and compare it with that found in other AR-regulated genes.

Role of prostate stem cell antigen in prostate cancer research

PURPOSE OF REVIEW

The identification of cell surface antigens is critical to the development of future prognostic and therapeutic modalities for the treatment of prostate cancer. Several prostate-specific proteins have been identified and are under investigation. This review reports on prostate stem cell antigen (PSCA), a protein with restricted expression that may have prognostic and therapeutic utility.

RECENT FINDINGS

PSCA is a glycosylphosphatidylinositol-anchored cell-surface protein belonging to the Ly-6/Thy-1 family of cell surface antigens, and a murine homologue has been described. It is expressed in the normal human prostate and overexpressed in human prostate cancers. Its overexpression has been correlated with increased Gleason score, advanced stage and bone metastasis. PSCA is co-amplified with MYC, an independent predictor of progression and death. PSCA may therefore be a useful predictor of tumor biology and a useful target of immunotherapy against prostate cancer. Evidence suggests a potential role in strategies employing cytotoxic T cell lymphocytes. Anti-tumor activity has been demonstrated with monoclonal antibodies in tumor take and established tumor xenograft models. Conjugated antibody has recently been reported to have anti-tumor activity in preclinical models.

SUMMARY

PSCA may serve as a tool in refining the prognosis of an individual cancer and may be a useful therapeutic target for immunotherapy. Future studies will be required to confirm its clinical utility as a prognostic factor. Future animal and clinical studies will be required to test various immunotherapy strategies for safety and efficacy. The study of PSCA regulation and expression may provide information on normal prostate development and prostate carcinogenesis.

Mouse models of prostate carcinogenesis

In recent years, numerous mouse models have been generated that recapitulate salient features of prostate carcinogenesis in humans. Here we review progress in the generation and validation of mouse models for prostate cancer, discuss current limitations of these models, and highlight directions of future research.