Selective expression of murine prostate stem cell antigen in fetal and adult tissues and the transgenic adenocarcinoma of the mouse prostate model of prostate carcinogenesis

Single-cell transcriptomics of human-skin-equivalent organoids

Several methods for generating human-skin-equivalent (HSE) organoid cultures are in use to study skin biology; however, few studies thoroughly characterize these systems. To fill this gap, we use single-cell transcriptomics to compare in vitro HSEs, xenograft HSEs, and in vivo epidermis. By combining differential gene expression, pseudotime analyses, and spatial localization, we reconstruct HSE keratinocyte differentiation trajectories that recapitulate known in vivo epidermal differentiation pathways and show that HSEs contain major in vivo cellular states. However, HSEs also develop unique keratinocyte states, an expanded basal stem cell program, and disrupted terminal differentiation. Cell-cell communication modeling shows aberrant epithelial-to-mesenchymal transition (EMT)-associated signaling pathways that alter upon epidermal growth factor (EGF) supplementation. Last, xenograft HSEs at early time points post transplantation significantly rescue many in vitro deficits while undergoing a hypoxic response that drives an alternative differentiation lineage. This study highlights the strengths and limitations of organoid cultures and identifies areas for potential innovation.

Regenerative potential of prostate luminal cells revealed by single-cell analysis

Androgen deprivation is the cornerstone of prostate cancer treatment. It results in involution of the normal gland to ~90% of its original size because of the loss of luminal cells. The prostate regenerates when androgen is restored, a process postulated to involve stem cells. Using single-cell RNA sequencing, we identified a rare luminal population in the mouse prostate that expresses stemlike genes (Sca1 ⁺ and Psca ⁺) and a large population of differentiated cells (Nkx3.1 ⁺, Pbsn ⁺). In organoids and in mice, both populations contribute equally to prostate regeneration, partly through androgen-driven expression of growth factors (Nrg2, Rspo3) by mesenchymal cells acting in a paracrine fashion on luminal cells. Analysis of human prostate tissue revealed similar differentiated and stemlike luminal subpopulations that likewise acquire enhanced regenerative potential after androgen ablation. We propose that prostate regeneration is driven by nearly all persisting luminal cells, not just by rare stem cells.

Prognostic significance of YY1 protein expression and mRNA levels by bioinformatics analysis in human cancers: a therapeutic target

Conventional therapeutic treatments for various cancers include chemotherapy, radiotherapy, hormonal therapy and immunotherapy. While such therapies have resulted in clinical responses, they were coupled with non-tumor specificity, toxicity and resistance in a large subset of the treated patients. During the last decade, novel approaches based on scientific knowledge on the biology of cancer were exploited and led to the development of novel targeted therapies, such as specific chemical inhibitors and immune-based therapies. Although these targeted therapies resulted in better responses and less toxicity, there still remains the problem of the inherent or acquired resistance. Hence, current studies are seeking additional novel therapeutic targets that can overcome several mechanisms of resistance. The transcription factor Yin Yang 1 (YY1) is a ubiquitous protein expressed in normal and cancer tissues, though the expression level is much higher in a large number of cancers; hence, YY1 has been considered as a potential novel prognostic biomarker and therapeutic target. YY1 has been reported to be involved in the regulation of drug/immune resistance and also in the regulation of EMT. Several excellent reviews have been published on YY1 and cancer (see below), and, thus, this review will update recently published reports as well as report on the analysis of bioinformatics datasets for YY1 in various cancers and the relationship between reported protein expression and mRNA levels. The potential clinical significance of YY1 is discussed.

Expression of prostate stem cell antigen (PSCA) in prostate cancer: a tissue microarray study of Iranian patients

Proteins expressed in prostate cancer, including prostate stem cell antigen (PSCA), have been investigated as biomarkers for diagnosis and therapy of prostate cancer. Immunohistochemical analysis of PSCA expression was performed on tissue microarrays of 185 paraffin-embedded tissues of Iranian patients, including 114 prostate cancers (PCa), 21 High Grade Prostatic Intraepithelial Neoplasias (HGPIN) and 50 samples of benign prostate tissue. The level of PSCA expression was compared between benign tissues, HGPIN and PCa. Then the correlations of PSCA expression with clinicopathologic parameters were assessed in PCa. The PSCA expression was detected in the membrane and cytoplasm of epithelial secretory cells in normal prostate tissues, HGPIN and PCa with a variety of intensities. The intensity of PSCA staining was significantly increased in the PCa group as compared with HGPIN and benign prostate tissues (P-value<0.05). Moreover, the level of PSCA expression was increased with higher Gleason score of PCa (P-value=0.036). The data presented here revealed that expression of PSCA as a cell surface marker increased from benign prostate tissues (BPH) and HGPIN to PCa, and its expression in PCa was positively associated with poor cell differentiation, suggesting that PSCA could be considered as a valuable target for diagnosis and therapy of PCa.

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.

Urine cytology and adjunct markers for detection and surveillance of bladder cancer

Urine cytology coupled with cystoscopic examination has been and remains the standard in the initial evaluation of lower urinary tract lesions to rule out bladder cancer. However, cystoscopy is invasive and may miss some flat lesions, whereas cytology has low sensitivity in low-grade papillary disease. Additional lab-based or office-based markers are needed to aid in the evaluation of these lesions. Recently, many such markers have been developed for the purpose of improving the cytologic diagnosis of bladder malignancies. In this review, we will first discuss conventional cytomorphologic analysis of urine cytology followed by a discussion of markers that have been developed in the past for detection and surveillance of urothelial carcinoma. We will focus on how these markers can be used in conjunction with urine cytology in daily practice.

Association and haplotype analysis of prostate stem cell antigen with gastric cancer in Tibetans

Genetic factors are known to be important in the development of gastric cancer (GC). Prostate stem cell antigen (PSCA) has been shown to be expressed in diffuse-type GC, and PSCA variation is associated with susceptibility to diffuse-type GC in Japanese and Korean populations. The aim of this study was to investigate the association between PSCA gene polymorphisms and GC in a Tibetan population. We analyzed single-nucleotide polymorphisms of the PSCA gene in 196 patients with GC and 246 controls in a Tibetan population, using a polymerase chain reaction/ligase detection reaction test. The rs2294008 C/T polymorphism of the PSCA gene was significantly associated with the susceptibility to GC. The CT genotype was associated with a significantly higher risk of GC when compared with the CC genotype (odds ratio [OR] = 1.50; 95% confidence interval [CI], 1.01-2.23). Patients carrying the T allele had a significantly higher risk for developing GC compared with individuals carrying the C allele (OR = 1.34; 95% CI, 1.00-1.79). Haplotype analyses showed that CA haplotype was associated with a significantly decreased risk of GC when compared with the CG haplotype (OR = 0.47; 95% CI, 0.24-0.93). Our data indicate that PSCA gene polymorphisms may be associated with GC in Tibetans.

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.

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.

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.

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.

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.

Characterization of the human Ly-6 antigens, the newly annotated member Ly-6K included, as molecular markers for head-and-neck squamous cell carcinoma

The E48 antigen is a successfully explored molecular marker for the diagnosis and therapy of HNSCC. The applicability of E48 as an HNSCC-associated antigen, however, is restricted due to its heterogeneous expression in 30% of tumors; and identification of additional target antigens is therefore desired. E48 belongs to the Ly-6 antigen family, comprising a group of highly homologous, low m.w., GPI-anchored surface proteins, of which some show tissue-restricted expression patterns. To identify novel human HNSCC-associated Ly-6 members with squamous cell-associated expression patterns, we performed comprehensive gene-screening consisting of BLAST searches within GenBank databases, followed by expression analysis. Using this approach, the Ly-6K gene could be annotated as a novel member of the human Ly-6 family. Expression of the human Ly-6 genes E48, Ly-6K, PSCA, GML, RIG-E, G6C and Ly-6H was prescreened by qualitative RT-PCR and subsequently analyzed by quantitative RT-PCR in normal keratinocytes, HNSCC cell lines, normal mucosa, HNSCC tumors as well as normal peripheral blood and bone marrow cells. PSCA was highly expressed in normal mucosa, but 100-fold decreased expression was seen in HNSCC. For Ly-6H, GML and G6C, no or very low expression was observed in keratinocytes and HNSCC. Expression of RIG-E was high in normal and malignant squamous cells and in peripheral blood and bone marrow cells, thus limiting its applicability as an HNSCC-associated marker. In contrast, besides the E48 gene, the Ly-6K gene also appeared to be selectively expressed in HNSCC and normal squamous cells. Moreover, expression of Ly-6K was shown in HNSCC cell lines, in which no E48 expression could be detected. These data justify further evaluation of Ly-6K as potential target antigen for the diagnosis and therapy of HNSCC.

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.

Isolation and characterization of the murine prostate short-chain dehydrogenase/reductase 1 (Psdr1) gene, a new member of the short-chain steroid dehydrogenase/reductase family

We report the isolation and characterization of a complementary DNA (cDNA) encoding a novel member of the short-chain dehydrogenase/reductase (SDR) gene family that we have designated murine prostate short-chain dehydrogenase/reductase 1 (Psdr1). Psdr1 was cloned as a 3.2 kbp transcript from mouse testis cDNA based on the sequence of the recently described androgen-regulated human PSDR1 gene (Cancer Res. 61 (2001) 1611). The putative protein encoded by Psdr1 consists of 316 amino acids with 85% identity to human PSDR1. A search against the BLOCKS database of conserved protein motifs indicates that Psdr1 retains features essential for SDR function. Northern analyses demonstrate that Psdr1 is highly expressed in the murine testis and liver and exhibits several isoforms. Cloning and sequence analysis of the putative Psdr1 promoter region identified motifs with homology to the consensus androgen response element and progesterone response element. The Psdr1 gene was mapped to mouse chromosome 12q31-34, which has synteny with the human PSDR1 chromosomal location (14q23-24.3). Together, these data describe a new member of the SDR gene family that may be involved in the tissue-specific metabolism of retinoids or steroid hormones.

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

The prostate gland undergoes dramatic changes in growth status during normal physiologic development, following androgen administration to castrate animals, and during tumor development. The prostate stem cell antigen (PSCA, named for its strong sequence homology to the thymocyte marker stem cell antigen 2) is a cell surface molecule associated with human and murine prostate cancer. To help define the regulation of this molecule, we created a transgenic mouse strain, which uses the human PSCA promoter region to control the expression of enhanced green fluorescent protein (GFP). Expression of GFP was detected in mid-gestation following the appearance of prostatic buds from the urogenital sinus. In adult mice, GFP expression was restricted to a subset of cells located in the distal tips of the glands. GFP expression increased during puberty and regeneration driven by androgen and associated with expansive growth of the prostate. GFP-positive cells coexpressed markers associated with both basal and secretory cells in the human prostate. Prostate carcinogenesis driven by T antigen in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model results in an increased percentage and intensity level for PSCA promoter-driven GFP-positive cells. This transgenic system helps define the range of cellular changes associated with altered expression of PSCA, shows that transcriptional control is a major component regulating PSCA levels, and provides a useful tool to study subpopulations of prostate epithelial cells and factors that regulate the PSCA promoter.