Alteration of the PATCHED locus in superficial bladder cancer

Low expression of ZSCAN4 predicts unfavorable outcome in urothelial carcinoma of upper urinary tract and urinary bladder

BACKGROUND

With the advance in genome-wide analyses, genetic alternations have been found to play an important role in carcinogenesis and aggressiveness of UC. Through bioinformatic analysis of gene expression profiles of urinary bladder urothelial carcinoma (UBUC) from publicly available GEO dataset (GSE31684), Zinc finger and SCAN domain containing 4 (ZSCAN4) was identified as a significant downregulated gene in muscle-invasive bladder cancer when compared with non-muscle-invasive bladder cancer.

METHODS

The expression of ZSCAN4 was evaluated by immunohistochemistry in 340 upper urinary tract urothelial carcinomas (UTUCs) and 295 UBUCs. The expression profiles of ZSCAN4 and potential signaling pathways were analyzed bioinformatically.

RESULTS

In UTUC, low expression of ZSCAN4 was significantly associated with advanced primary pT stage (P = 0.011), increased nodal metastasis (P = 0.002) and increased vascular invasion (P = 0.019). In UBUC, low expression of ZSCAN4 was significantly correlated with advanced primary pT stage (P < 0.001), increased nodal metastasis (P = 0.001), high histological grade (P = 0.003) and increased vascular invasion (P = 0.003). In survival analysis, low expression of ZSCAN4 acted as an independent negative prognostic factor for disease-specific survival and metastasis-free survival both in UTUC and UBUC. Gene ontology analysis showed that ZSCAN4 mRNA and its co-downregulated genes are associated with the mitotic cell cycle.

CONCLUSIONS

Low expression of ZSCAN4 predicted worse outcome in urothelial carcinoma and might have potential regulatory role in cell mitosis.

Evolution of Urothelial Bladder Cancer in the Context of Molecular Classifications

Bladder cancer is a heterogeneous disease that is not depicted by current classification systems. It was originally classified into non-muscle invasive and muscle invasive. However, clinically and genetically variable tumors are summarized within both classes. A definition of three groups may better account for the divergence in prognosis and probably also choice of treatment. The first group represents mostly non-invasive tumors that reoccur but do not progress. Contrarily, the second group represent non-muscle invasive tumors that likely progress to the third group, the muscle invasive tumors. High throughput tumor profiling improved our understanding of the biology of bladder cancer. It allows the identification of molecular subtypes, at least three for non-muscle invasive bladder cancer (Class I, Class II and Class III) and six for muscle-invasive bladder cancer (luminal papillary, luminal non-specified, luminal unstable, stroma-rich, basal/squamous and neuroendocrine-like) with distinct clinical and molecular phenotypes. Molecular subtypes can be potentially used to predict the response to treatment (e.g., neoadjuvant chemotherapy and immune checkpoint inhibitors). Moreover, they may allow to characterize the evolution of bladder cancer through different pathways. However, to move towards precision medicine, the understanding of the biological meaning of these molecular subtypes and differences in the composition of cell subpopulations will be mandatory.

Sonic Hedgehog Expression is Associated with Lymph Node Invasion in Urothelial Bladder Cancer

Bladder cancer (BC) is a deadly disease characterized by high recurrence rates and frequent progression to an aggressive phenotype. Dysregulation of various signaling pathways have been implicated in BC tumorigenesis, however, the clinical relevance of sonic hedgehog pathway (Shh) remains under investigated. The aim of the current study was to analyze the prognostic value of Shh expression in patients with bladder carcinoma. Immunohistochemical expression of Shh was performed using tissue microarray with 128 specimens from bladder cancer patients. Kaplan-meier survival was analysed and correlation between Shh protein expression and patients' clinicopathological parameters wasexamined using Fisher's exact test. The immuno-staining results revealed that Shh protein exhibits cytoplasmic localization and is expressed in 49% of the analyzed bladder cancer cohort. Our data indicated that high Shh expression significantly correlated with increased lymph node metastasis (p = 0.02), however no association was reported between Shh expression and other clinicopatholigical parameters. High expression of sonic hedgehog was associated with lymph node invasion which may indicate that Shh might play an important role in progression and metastasis of bladder cancer.

The evolution of bladder cancer genomics: What have we learned and how can we use it?

BACKGROUND

With advancements in molecular biology techniques, great progress has been made in the understanding of urothelial carcinoma pathogenesis.

OBJECTIVE

To examine the historic description of molecular alterations in bladder cancer and their evolution towards our current comprehension of the biology of the disease.

RESULTS

Historically, a two-pathway model was described from histological and cytogenetic studies: low-grade papillary non-muscle invasive bladder cancers (NMIBC) were described to arise from epithelial hyperplasia with loss of chromosome 9 as an early event, whereas muscle-invasive bladder cancers (MIBC) were considered to develop from dysplasia, associated with genetic instability. Although there could be connections between the 2 pathways, NMIBC and MIBC were largely believed to develop secondary to different molecular alterations. Next-generation sequencing has allowed important insights into cancer biology and a better understanding of the pathways involved in bladder cancer pathogenesis and heterogeneity. Urothelial carcinoma has been found to have a high frequency of somatic mutations compared to other solid tumors, including several mutations in multiple signaling pathways, such as cell cycle regulators (TP53, RB1), RTK/RAS/RAF pathway, PI3K/AKT/mTOR pathway and TERT gene promoter. Epigenetic changes and mutations in chromatin remodeling genes are especially frequent in bladder cancer. Mutations in FGFR3 and KDM6A are more common in NMIBC than in MIBC, whereas mutations in TP53 and KMT2D are more common in MIBC, suggesting the previously hypothesized 2 different pathways, with a subset of tumors progressing from NMIBC to MIBC. Using comprehensive RNA expression profiling studies, at least 5 subtypes of bladder cancer have been identified, the most fundamental division being Basal/Squamous-like and Luminal. These subtypes have different prognoses, natural histories and responses to systemic treatments: Luminal subtypes are enriched with papillary histology and have a better prognosis, while Basal/Squamous-like subtypes are enriched with squamous features, are associated with advanced stage at presentation, and portend a worse prognosis.

CONCLUSION

This new understanding of bladder cancer will optimistically translate into better understanding of this heterogeneous disease and lead to improvement in patient outcome and quality of life through better tailored treatments.

SLC14A1: a novel target for human urothelial cancer

Urinary bladder cancer is the second commonly diagnosed genitourinary malignancy. Previously, bio-molecular alterations have been observed within certain locations such as chromosome 9, retinoblastoma gene and fibroblast growth factor receptor-3. Solute carrier family 14 member 1 (SLC14A1) gene encodes the type-B urea transporter (UT-B) which facilitates the passive movement of urea across cell membrane, and has recently been related with human malignancies, especially for bladder cancer. Herein, we discussed the SLC14A1 gene and UT-B protein properties, aiming to elucidate the expression behavior of SLC14A1 in human bladder cancer. Furthermore, by reviewing some well-established theories regarding the carcinogenesis of bladder cancer, including several genome wide association researches, we have bridged the mechanisms of cancer development with the aberrant expression of SLC14A1. In conclusion, the altered expression of SLC14A1 gene in human urothelial cancer may implicate its significance as a novel target for research.

A novel hedgehog inhibitor iG2 suppresses tumorigenesis by impairing self-renewal in human bladder cancer

Tumor recurrence is still a major challenge for clinical treatment of bladder cancer. Cumulative evidences indicate cancer stem cells (CSCs) contribute to drug resistance and leave a putative source for disease relapse. Identifying novel agents targeting CSCs may represent a new paradigm in the therapy of bladder cancer. Here, we separated a novel hedgehog (Hh) inhibitor, iG2, from streptomyces roseofulvus, which dramatically blocked the activation of Gli2 in bladder cancer cells. The iG2 strongly repressed the growth of cancer cells rather than the peri‐tumor stroma cells. Attenuated proliferation and enhanced apoptosis of tumor cells were observed upon iG2 stimulation. Furthermore, iG2 reduced the self‐renewal ability of bladder CSCs as well as the tumor formation. Collectively, iG2 is potentially used as a novel therapeutic agent for bladder cancer by targeting self‐renewal through inhibiting Hh pathway.

GALNT1-Mediated Glycosylation and Activation of Sonic Hedgehog Signaling Maintains the Self-Renewal and Tumor-Initiating Capacity of Bladder Cancer Stem Cells

The existence of bladder cancer stem cells (BCSC) has been suggested to underlie bladder tumor initiation and recurrence. Sonic Hedgehog (SHH) signaling has been implicated in promoting cancer stem cell (CSC) self-renewal and is activated in bladder cancer, but its impact on BCSC maintenance is unclear. In this study, we generated a mAb (BCMab1) against CD44(+) human bladder cancer cells that recognizes aberrantly glycosylated integrin α3β1. The combination of BCMab1 with an anti-CD44 antibody identified a BCMab1(+)CD44(+) cell subpopulation as BCSCs with stem cell-like properties. Gene expression analysis revealed that the hedgehog pathway was activated in the BCMab1(+)CD44(+) subpopulation and was required for BCSC self-renewal. Furthermore, the glycotransferase GALNT1 was highly expressed in BCMab1(+)CD44(+) cells and correlated with clinicopathologic features of bladder cancers. Mechanistically, GALNT1 mediated O-linked glycosylation of SHH to promote its activation, which was essential for the self-renewal maintenance of BCSCs and bladder tumorigenesis. Finally, intravesical instillation of GALNT1 siRNA and the SHH inhibitor cyclopamine exerted potent antitumor activity against bladder tumor growth. Taken together, our findings identify a BCSC subpopulation in human bladder tumors that appears to be responsive to the inhibition of GALNT1 and SHH signaling, and thus highlight a potential strategy for preventing the rapid recurrence typical in patients with bladder cancer.

Molecular biology of bladder cancer: new insights into pathogenesis and clinical diversity

Urothelial carcinoma of the bladder comprises two long-recognized disease entities with distinct molecular features and clinical outcome. Low-grade non-muscle-invasive tumours recur frequently but rarely progress to muscle invasion, whereas muscle-invasive tumours are usually diagnosed de novo and frequently metastasize. Recent genome-wide expression and sequencing studies identify genes and pathways that are key drivers of urothelial cancer and reveal a more complex picture with multiple molecular subclasses that traverse conventional grade and stage groupings. This improved understanding of molecular features, disease pathogenesis and heterogeneity provides new opportunities for prognostic application, disease monitoring and personalized therapy.

Clinicopathological correlates of Gli1 expression in a population-based cohort of patients with newly diagnosed bladder cancer

INTRODUCTION

Dysregulation of the hedgehog signaling pathway has been linked to the development and progression of a variety of different human tumors including cancers of the skin, brain, colon, prostate, blood, and pancreas. We assessed the clinicopathological factors that are potentially related to expression of Gli1, the transcription factor that is thought to be the most reliable marker of hedgehog pathway activation in bladder cancer.

METHODS

Bladder cancer cases were identified from the New Hampshire State Cancer Registry as histologically confirmed primary bladder cancer diagnosed between January 1, 2002, and July 31, 2004. Immunohistochemical analysis was performed on a tissue microarray to detect Gli1 and p53 expression in these bladder tumors. We computed odds ratios (ORs) and their 95% CIs for Gli1 positivity for pathological category using T category (from TNM), invasiveness, and grade with both the World Health Organization 1973 and World Health Organization International Society of Urological Pathology criteria. We calculated hazard ratios and their 95% CI for Gli1 positivity and recurrence for both Ta-category and invasive bladder tumors (T1+).

RESULTS

A total of 194 men and 67 women, whose tumors were assessable for Gli1 staining, were included in the study. No appreciable differences in Gli1 staining were noted by sex, age, smoking status, or high-risk occupation. Ta-category tumors were more likely to stain for Gli1 as compared with T1-category tumors (adjusted OR = 0.38, CI: 0.17-0.87). Similarly, low-grade (grades 1-2) tumors were more likely to stain for Gli1 as compared with high-grade tumors (grade 3) (adjusted OR = 0.44, CI: 0.21-0.93). In a Cox proportional hazards regression analysis, non-muscle-invasive bladder tumors expressing Gli1 were less likely to recur (adjusted hazard ratio = 0.48; CI: 0.28-0.82; P<0.05) than those in which Gli1 was absent.

CONCLUSION

Our findings indicate that Gli1 expression may be a marker of low-stage, low-grade bladder tumors and an indicator of a reduced risk of recurrence in this group.

Distinct effects of the mesenchymal dysplasia gene variant of murine Patched-1 protein on canonical and non-canonical Hedgehog signaling pathways

Hedgehog (Hh) signaling requires regulation of the receptor Patched-1 (Ptch1), which, in turn, regulates Smoothened activity (canonical Hh signaling) as well as other non-canonical signaling pathways. The mutant Ptch1 allele mesenchymal dysplasia (mes), which truncates the Ptch1 C terminus, produces a limited spectrum of developmental defects in mice as well as deregulation of canonical Hh signaling in some, but not all, affected tissues. Paradoxically, mes suppresses canonical Hh signaling and binds to Hh ligands with an affinity similar to wild-type mouse Ptch1 (mPtch1). We characterized the distinct activities of the mes variant of mPtch1 mediating Hh signaling through both canonical and non-canonical pathways. We demonstrated that mPtch1 bound c-src in an Hh-regulated manner. Stimulation with Sonic Hedgehog (Shh) of primary mammary mesenchymal cells from wild-type and mes animals activated Erk1/2. Although Shh activated c-src in wild-type cells, c-src was constitutively activated in mes mesenchymal cells. Transient assays showed that wild-type mPtch1, mes, or mPtch1 lacking the C terminus repressed Hh signaling in Ptch1-deficient mouse embryo fibroblasts and that repression was reversed by Shh, revealing that the C terminus was dispensable for mPtch1-dependent regulation of canonical Hh signaling. In contrast to these transient assays, constitutively high levels of mGli1 but not mPtch1 were present in primary mammary mesenchymal cells from mes mice, whereas the expression of mPtch1 was similarly induced in both mes and wild-type cells. These data define a novel signal transduction pathway involving c-src that is activated by the Hh ligands and reveals the requirement for the C terminus of Ptch in regulation of canonical and non-canonical Hh signaling pathways.

Hedgehog signaling regulates bladder cancer growth and tumorigenicity

The role of Hedgehog (HH) signaling in bladder cancer remains controversial. The gene encoding the HH receptor and negative regulator PATCHED1 (PTCH1) resides on a region of chromosome 9q, one copy of which is frequently lost in bladder cancer. Inconsistent with PTCH1 functioning as a classic tumor suppressor gene, loss-of-function mutations in the remaining copy of PTCH1 are not commonly found. Here, we provide direct evidence for a critical role of HH signaling in bladder carcinogenesis. We show that transformed human urothelial cells and many urothelial carcinoma cell lines exhibit constitutive HH signaling, which is required for their growth and tumorigenic properties. Surprisingly, rather than originating from loss of PTCH1, the constitutive HH activity observed in urothelial carcinoma cell lines was HH ligand dependent. Consistent with this finding, increased levels of HH and the HH target gene product GLI1 were found in resected human primary bladder tumors. Furthermore, on the basis of the difference in intrinsic HH dependence of urothelial carcinoma cell lines, a gene expression signature was identified that correlated with bladder cancer progression. Our findings therefore indicate that therapeutic targeting of the HH signaling pathway may be beneficial in the clinical management of bladder cancer.

Hedgehog pathway activation in human transitional cell carcinoma of the bladder

BACKGROUND

The Hedgehog (Hh) signalling pathway functions as an organiser in embryonic development. Recent studies have shown constitutive activation of this pathway in various malignancies, but its role in bladder cancer remains poorly studied.

METHODS

Expression levels of 31 genes and 9 microRNAs (miRNAs) involved in the Hh pathway were determined by quantitative real-time RT-PCR in 71 bladder tumour samples (21 muscle-invasive (MIBC) and 50 non-muscle-invasive (NMIBC) bladder cancers), as well as in 6 bladder cancer cell lines.

RESULTS

The SHH ligand gene and Gli-inducible target genes (FOXM1, IGF2, OSF2, H19, and SPP1) were overexpressed in tumour samples as compared with normal bladder tissue. SHH overexpression was found in 96% of NMIBC and 52% of MIBC samples, as well as in two bladder cancer cell lines. Altered expression of miRNAs supported their oncogene or tumour-suppressor gene status. In univariate analysis, high expression levels of PTCH2, miRNA-92A, miRNA-19A, and miRNA-20A were associated with poorer overall survival in MIBC (P=0.02, P=0.012, P=0.047, and P=0.036, respectively).

CONCLUSION

We observed constitutive activation of the Hh pathway in most NMIBC and about 50% of MIBC. We also found that some protein-coding genes and miRNAs involved in the Hh pathway may have prognostic value at the individual level.

Targeting metastatic upper gastrointestinal adenocarcinomas

Upper gastrointestinal (GI) tumors, including adenocarcinoma of the esophagus, stomach, pancreas, and biliary tree, have traditionally been difficult to treat with cytotoxic chemotherapeutic agents. There has been little drug development success in treating these cancers over the last 20 years, perhaps a reflection of a combination of the aggressive biology of these tumors, the void in effective and specific drug development for these varied tumors, and the lack of properly designed, biologically-based clinical trials. Recently, so called "targeted agents" have risen to the forefront in the care of cancer patients and have made strong impacts in many areas of oncology, particularly gastrointestinal stromal tumors (GIST), colon, breast, and lung cancers. Unfortunately, slow progress has been made using such agents in upper GI tumors. However, more recently, trials in some tumor types have demonstrated gains in progression free survival and overall survival. In this review, we discuss the drugs and pathways that have been most successful in the treatment of upper GI tumors and present the relevant data supporting their use for each tumor site. Additionally, we will explore a few novel pathways that may prove effective in the treatment of upper GI malignancies in the near future.

Bladder cancer or bladder cancers? Genetically distinct malignant conditions of the urothelium

Despite the fact that the current histopathologic classification for bladder cancer has led to improved concepts for the clinical management of the disease, key questions with regard to assessment of risk for recurrence and/or progression to invasive disease remain. In addition, response to specific therapies cannot be predicted accurately. Bladder tumors comprise a heterogeneous group with respect to both histopathology and clinical behavior. Thus, it is anticipated that a thorough knowledge and interpretation of the molecular alterations involved in tumor development and progression will lead to greater prognostic and predictive power. This may not only lead to better comprehension of the biology of the disease, but may also lead to the development of novel individualized therapies. Novel means of stratification are urgently needed to provide a new subclassification of urothelial lesions. This review discusses and summarizes the genetic alterations that have been reported in bladder cancer and relates these to the current 2-pathway model for tumor development. The molecular pathogenesis of high-grade noninvasive papillary tumors and of T1 tumors is not yet clear, and possibilities are discussed.

Genetic variations in the sonic hedgehog pathway affect clinical outcomes in non-muscle-invasive bladder cancer

Sonic hedgehog (Shh) pathway genetic variations may affect bladder cancer risk and clinical outcomes. Therefore, we genotyped 177 single-nucleotide polymorphisms (SNP) in 11 Shh pathway genes in a study including 803 bladder cancer cases and 803 controls. We assessed SNP associations with cancer risk and clinical outcomes in 419 cases of non-muscle-invasive bladder cancer (NMIBC) and 318 cases of muscle-invasive and metastatic bladder cancer (MiMBC). Only three SNPs (GLI3 rs3823720, rs3735361, and rs10951671) reached nominal significance in association with risk (P ≤ 0.05), which became nonsignificant after adjusting for multiple comparisons. Nine SNPs reached a nominally significant individual association with recurrence of NMIBC in patients who received transurethral resection (TUR) only (P ≤ 0.05), of which two (SHH rs1233560 and GLI2 rs11685068) were replicated independently in 356 TUR-only NMIBC patients, with P values of 1.0 × 10(-3) (SHH rs1233560) and 1.3 × 10(-3) (GLI2 rs11685068). Nine SNPs also reached a nominally significant individual association with clinical outcome of NMIBC patients who received Bacillus Calmette-Guérin (BCG; P ≤ 0.05), of which two, the independent GLI3 variants rs6463089 and rs3801192, remained significant after adjusting for multiple comparisons (P = 2 × 10(-4) and 9 × 10(-4), respectively). The wild-type genotype of either of these SNPs was associated with a lower recurrence rate and longer recurrence-free survival (versus the variants). Although three SNPs (GLI2 rs735557, GLI2 rs4848632, and SHH rs208684) showed nominal significance in association with overall survival in MiMBC patients (P ≤ 0.05), none remained significant after multiple-comparison adjustments. Germ-line genetic variations in the Shh pathway predicted clinical outcomes of TUR and BCG for NMIBC patients.

Activation of Hedgehog signaling by the environmental toxicant arsenic may contribute to the etiology of arsenic-induced tumors

Exposure to the environmental toxicant arsenic, through both contaminated water and food, contributes to significant health problems worldwide. In particular, arsenic exposure is thought to function as a carcinogen for lung, skin, and bladder cancer via mechanisms that remain largely unknown. More recently, the Hedgehog signaling pathway has also been implicated in the progression and maintenance of these same cancers. Based on these similarities, we tested the hypothesis that arsenic may act in part through activating Hedgehog signaling. Here, we show that arsenic is able to activate Hedgehog signaling in several primary and established tissue culture cells as well as in vivo. Arsenic activates Hedgehog signaling by decreasing the stability of the repressor form of GLI3, one of the transcription factors that ultimately regulate Hedgehog activity. We also show, using tumor samples from a cohort of bladder cancer patients, that high levels of arsenic exposure are associated with high levels of Hedgehog activity. Given the important role Hedgehog signaling plays in the maintenance and progression of a variety of tumors, including bladder cancer, these results suggest that arsenic exposure may in part promote cancer through the activation of Hedgehog signaling. Thus, we provide an important insight into the etiology of arsenic-induced human carcinogenesis, which may be relevant to millions of people exposed to high levels of arsenic worldwide.

Focal amplifications are associated with high grade and recurrences in stage Ta bladder carcinoma

Urinary bladder cancer is a heterogeneous disease with tumors ranging from papillary noninvasive (stage Ta) to solid muscle infiltrating tumors (stage T2+). The risk of progression and death for the most frequent diagnosed type, Ta, is low, but the high incidence of recurrences has a significant effect on the patients' quality of life and poses substantial costs for health care systems. Consequently, the purpose of this study was to search for predictive factors of recurrence on the basis of genetic profiling. A clinically well characterized cohort of Ta bladder carcinomas, selected by the presence or absence of recurrences, was evaluated by an integrated analysis of DNA copy number changes and gene expression (clone-based 32K, respectively, U133Plus2.0 arrays). Only a few chromosomal aberrations have previously been defined in superficial bladder cancer. Surprisingly, the profiling of Ta tumors with a high-resolution array showed that DNA copy alterations are relatively common in this tumor type. Furthermore, we observed an overrepresentation of focal amplifications within high-grade and recurrent cases. Known (FGFR3, CCND1, MYC, MDM2) and novel candidate genes were identified within the loci. For example, MYBL2, a nuclear transcription factor involved in cell-cycle progression; YWHAB, an antiapoptotic protein; and SDC4, an important component of focal adhesions represent interesting candidates detected within two amplicons on chromosome 20, for which DNA amplification correlated with transcript up-regulation. The observed overrepresentation of amplicons within high-grade and recurrent cases may be clinically useful for the identification of patients who will benefit from a more aggressive therapy.

Environmental factors and genetic susceptibility promote urinary bladder cancer

Cancer of the urinary bladder is the second most common malignancy of the genitourinary tract, currently accounting for up to 5% of all newly diagnosed tumours in the western world. Urinary bladder carcinogenesis seems to develop from the interaction of environmental exposure and genetic susceptibility. Smoking, specific industrial chemicals, dietary nitrates and arsenic represent the most important exogenous risk factors. Chromosomal abnormalities, silencing of certain genes by abnormal methylation of their promoter region, alterations in tumour suppressor genes and proto-oncogenes that induce uncontrolled cell proliferation and reduced apoptosis, are molecular mechanisms that have been reported in bladder carcinogenesis. In this article, we discuss the environmental risk factors of bladder cancer and we review the genetic and epigenetic alterations, including aberrant DNA methylation and deregulation of microRNAs expression. We also discuss the role of p53 and retinoblastoma suppressor genes in disease progression. Finally, we present recent reports on the use of molecular profiling to predict disease stage and grade and direct targeted therapy.

Molecular pathogenesis of bladder cancer

Bladder tumors show widely differing histopathology and clinical behavior. This is reflected in the molecular genetic alterations they contain. Much information has accumulated on somatic genomic alterations in bladder tumors of all grades and stages and when this information is related to the common histopathological appearances, a model for the pathogenesis of two major groups of bladder tumors has emerged. This review summarizes the genetic alterations that have been reported in bladder cancer and relates these to the current two-pathway model for tumor development. The molecular pathogenesis of high-grade noninvasive papillary tumors and of T1 tumors is not yet clear and possibilities are discussed.

Comparative genomic hybridization study of arsenic-exposed and non-arsenic-exposed urinary transitional cell carcinoma

To compare the differences in DNA aberrations between arsenic-exposed and non-arsenic-exposed transitional cell carcinoma (TCC), we analyzed 19 arsenic-exposed and 29 non-arsenic-exposed urinary TCCs from Chi-Mei Hospital using comparative genomic hybridization. DNA aberrations were detected in 42 TCCs including 19 arsenic-exposed and 23 non-arsenic-exposed TCCs. Arsenic-exposed TCCs had more changes than unexposed TCCs (mean+/-SD, 6.6+/-2.9 vs. 2.9+/-2.2). Arsenic exposure was significantly associated with the number of DNA aberrations after adjustment for tumor stage, tumor grade and cigarette smoking in multiple regression analysis. The most frequent DNA gains, which were strikingly different between arsenic-exposed and non-arsenic-exposed TCCs, included those at 1p, 4p, 4q and 8q. A much higher frequency of DNA losses in arsenic-exposed TCCs compared with non-arsenic-exposed TCCs was observed in 10q, 11p and 17p. Chromosomal loss in 17p13 was associated not only with arsenic exposure, but also with tumor stage and grade. The p53 immunohistochemistry staining showed that chromosome 17p13 loss was associated with either p53 no expression (25%) or p53 overexpression (75%). The findings suggest that long-term arsenic exposure may increase the chromosome abnormality in TCC, and 17p loss plays an important role in arsenic-induced urinary carcinogenesis.

Induction of sonic hedgehog mediators by transforming growth factor-beta: Smad3-dependent activation of Gli2 and Gli1 expression in vitro and in vivo

Hedgehog (Hh) and transforming growth factor-beta (TGF-beta) family members are involved in numerous overlapping processes during embryonic development, hair cycle, and cancer. Herein, we show that TGF-beta induces the expression of the Hh signaling molecules Gli1 and Gli2 in various human cell types, including normal fibroblasts and keratinocytes, as well as various cancer cell lines. Gli2 induction by TGF-beta is rapid, independent from Hh receptor signaling, and requires a functional Smad pathway. Gli1 expression is subsequently activated in a Gli2-dependent manner. In transgenic mice overexpressing TGF-beta1 in the skin, Gli1 and Gli2 expression is also elevated and depends on Smad3. In pancreatic adenocarcinoma cell lines resistant to Hh inhibition, pharmacologic blockade of TGF-beta signaling leads to repression of cell proliferation accompanied with a reduction in Gli2 expression. We thus identify TGF-beta as a potent transcriptional inducer of Gli transcription factors. Targeting the cooperation of Hh and TGF-beta signaling may provide new therapeutic opportunities for cancer treatment.

Fibroblast Growth Factor Receptor 3 Mutations in Epidermal Nevi and Associated Low Grade Bladder Tumors

Epidermal nevi (EN) are benign lesions presenting at birth or in childhood. Based on the occurrence of fibroblast growth factor receptor 3 (FGFR3) mutations in seborrheic keratosis and urothelial carcinomas (UC), and the identification of two young patients with EN and UC, we hypothesized that mutations might occur in EN. The R248C mutation was found in 6/23 (26.1%) EN but it was absent from unaffected skin. In two patients with EN and UC, both lesions were FGFR3 wild type. Our findings indicate that: (1) FGFR3 mutations occur in mosaicism and can cause EN and (2) other genes are involved in EN.

Understanding urothelial carcinoma through cancer pathways

Urothelial carcinoma (UC), the common histological subtype of bladder cancer, presents as a papillary tumor or as an invasive, often lethal form. To study UC molecular biology, candidate gene and genome-wide approaches have been followed. Here, it is argued that a 'cancer pathway' perspective is useful to integrate findings from both approaches. According to this view, papillary cancers typically exhibit activation of the MAPK pathway, as a consequence of oncogenic mutations in FGFR3 or HRAS, with increased Cyclin D1 expression. In contrast, invasive UC are characterized by severe disturbances in proximate cell cycle regulators, e.g. RB1 and CDKN2A/p16(INK4A), which decrease dependency on mitogenic signaling. In addition, these disturbances permit, promote and are in turn exacerbated by chromosomal instability, which is further enhanced by loss of TP53 function. In another vicious cycle, defective cell cycle regulation interacts with DNA methylation alterations. The transition toward invasive UC may require concomitant and interacting defects in cell cycle regulation and the control of genomic stability. Intriguingly, neither canonical WNT/beta-Catenin nor hedgehog signaling appear to play major roles in UC. This may reflect its origin from more differentiated urothelial cells possessing a high regenerative potential rather than a stem cell population.

PTCH mutations and deletions in patients with typical nevoid basal cell carcinoma syndrome and in patients with a suspected genetic predisposition to basal cell carcinoma: a French study

The patched (PTCH) mutation rate in nevoid basal cell carcinoma syndrome (NBCCS) reported in various studies ranges from 40 to 80%. However, few studies have investigated the role of PTCH in clinical conditions suggesting an inherited predisposition to basal cell carcinoma (BCC), although it has been suggested that PTCH polymorphisms could predispose to multiple BCC (MBCC). In this study, we therefore performed an exhaustive analysis of PTCH (mutations detection and deletion analysis) in 17 patients with the full complement of criteria for NBCCS (14 sporadic and three familial cases), and in 48 patients suspected of having a genetic predisposition to BCC (MBCC and/or age at diagnosis ⩽40 years and/or familial BCC). Eleven new germline alterations of the PTCH gene were characterised in 12 out of 17 patients harbouring the full complement of criteria for the syndrome (70%). These were frameshift mutations in five patients, nonsense mutations in five patients, a small inframe deletion in one patient, and a large germline deletion in another patient. Only one missense mutation (G774R) was found, and this was in a patient affected with MBCC, but without any other NBCCS criterion. We therefore suggest that patients harbouring the full complement of NBCCS criteria should as a priority be screened for PTCH mutations by sequencing, followed by a deletion analysis if no mutation is detected. In other clinical situations that suggest genetic predisposition to BCC, germline mutations of PTCH are not common.

Sequence variations of microRNAs in human cancer: alterations in predicted secondary structure do not affect processing

Expression levels of microRNAs (miRNAs) are globally reduced in cancer compared with matched normal tissues, and miRNA function has recently been implicated in tumorigenesis. To test whether epigenetic silencing contributes to miRNA suppression in tumors, lung cancer cells were treated with inhibitors of DNA methylation or histone deacetylation. No significant alteration in miRNA expression was detected using microarray profiling. To search for tumor-associated mutations that could affect processing and expression of mature miRNAs, a panel of 91 cancer-derived cell lines was analyzed for sequence variations in 15 miRNAs implicated in tumorigenesis by virtue of their known target transcripts (let-7 family targeting oncogenic Ras) or their localization to sites of frequent chromosomal instability (miR-143, miR-145, miR-26a-1, and miR-21). No mutations were detected within any of the short mature miRNA sequences. In addition to previously reported polymorphisms, 1 sequence variant in a precursor miRNA and 15 variants in primary miRNA (pri-miRNA) transcripts were identified. Despite pri-miRNAs having dramatic changes in the predicted secondary folding structure flanking putative cleavage sites, processing and miRNA maturation were not affected in vivo. Thus, genetic variants in miRNA precursors are common in cancer cells but are unlikely to have physiologic significance.

Allelic loss at Drosophila patched gene is highly prevalent in Basal and squamous cell carcinomas of the skin

The human homolog of the Drosophila Patched gene (PTCH), located at chromosome 9q22.3, is frequently altered in both nevoid basal cell carcinoma syndrome, and sporadic basal cell carcinomas (BCCs). However, alteration of the PTCH gene locus has been poorly studied in squamous cell carcinoma (SCC). We analyzed loss of heterozygosity (LOH) at five markers in and around the PTCH gene in 276 keratinocyte tumors from a population-based study in New Hampshire. We found a high prevalence of any 9q22.3 LOH in both BCC (75.5%) and SCC (60.8%), with BCC being significantly more likely to have LOH than SCC (P<0.009). The PTCH gene was specifically lost in 60% of BCC, and 50% of SCC tumors. Among SCC tumors, 9q22 LOH was significantly more likely to occur in those who tend to burn (P<0.05), and this association was strongest for tumors that occurred on sun-exposed areas of the body (P<0.04). Additionally, 9q22 LOH occurred more frequently in SCC tumors associated with a history of severe sunburns (P<0.08). Thus, in our large, population-based sample, 9q22 loss, including PTCH, was highly prevalent in both BCC and SCC. Overall, these data support the hypothesis that PTCH loss is a common, early lesion for SCC and BCC.

A mouse prostate cancer model induced by Hedgehog overexpression

Hedgehog is a regulatory protein during embryonic development and its abnormal activation in adult tissues has been implicated in tumorigenesis within sites where epithelial-mesenchymal interactions take place. In the prostate, Hedgehog signaling activation was observed during advanced cancer progression and metastasis, but whether Hedgehog overexpression can initiate prostate tumorigenesis remains unknown. We introduced a Hedgehog-expressing vector by intra-prostate injection and electroporation to address the effects of Hedgehog overexpression. The manipulation caused lesions with characteristic prostatic intraepithelial neoplasia or even prostatic cancer (CaP) phenotypes within 30 days, with Hedgehog overexpression demonstrated by immunohistochemistry and Western blot detections. The tumorigenic phenotypes were confirmed by discontinuity of basal cell marker p63, mix-up of CK-8/CK-18 positive epithelial cells in the stoma as well as absence of alpha-SMA positive fibro-muscular sheath. Comparable Hedgehog overexpression was found in human CaP specimen. Thus, Hedgehog overexpression induced prostate tumorigenesis starting from the normal status. Furthermore, a mouse prostate cancer model induced by Hedgehog overexpression was established and may be used for testing novel therapeutical approaches targeting at Hedgehog signaling pathway.

Molecular subtypes of bladder cancer: Jekyll and Hyde or chalk and cheese?

Cancer of the bladder shows divergent clinical behaviour following diagnosis and it has been proposed that two major groups of tumours exist that develop via different molecular pathways. Low-grade, non-invasive papillary tumours recur frequently, but patients with these tumours do not often suffer progression of disease to muscle invasion. In contrast, tumours that are invading muscle at diagnosis are aggressive and associated with significant mortality. Molecular studies have identified distinct genetic, epigenetic and expression changes in these groups. However, it is not yet clear whether there is direct progression of low-grade superficial tumours to become invasive (a Jeckell and Hyde scenario) or whether in those patients who apparently progress from one form of the disease to the other, different tumour clones are involved and that the two tumour groups are mutually exclusive ('chalk and cheese'). If the latter is true, then attempts to identify molecular markers to predict progression of low-grade superficial bladder tumours may be fruitless. Similarly, it is not clear whether other subgroups of tumours exist that arise via different molecular pathways. There is now a large amount of molecular information about bladder cancer that facilitates examination of these possibilities. Some recent studies provide evidence for the existence of at least one further group of tumours, high-grade superficial papillary tumours, which may develop via a distinct molecular pathway. Patients with such tumours do show increased risk of disease progression and for these there may exist a real progression continuum from non-invasive to invasive. If this is the case, definition of the molecular signature of this pathway and improved understanding of the biological consequences of the events involved will be pivotal in disease management.

The hedgehog signalling pathway in the gastrointestinal tract: implications for development, homeostasis, and disease

The hedgehog signalling pathway is critical to normal mammalian gastrointestinal development. Through epithelial-mesenchymal interactions, hedgehog signalling ensures appropriate axial patterning of the embryonic gut. Congenital abnormalities, including malrotations, anorectal malformations, and tracheoesophageal fistula are associated with germ-line mutations/deletion of genes encoding hedgehog signalling components in man and present in genetically engineered animal models. In adults, there is evidence that the pathway plays a role in maintaining stem cell populations in the stomach and directing epithelial cell differentiation in the intestine. Recent data implicate hedgehog signalling in the formation and maintenance of a number of malignancies, including those of the upper gastrointestinal (GI) tract and pancreas, in which abrogation of the pathway offers a novel therapeutic approach in animal models. Most recently, evidence in vitro indicates that there is a recapitulation of embryonic hedgehog signalling in acute epithelial injury and chronic inflammation, a finding with key implications for inflammatory disorders of the intestine, such as inflammatory bowel diseases. This pathway may provide an important link between chronic inflammation and cancer. We summarize the available evidence demonstrating that this developmental pathway has continuing roles in adult homeostasis and is dysregulated in malignancy and inflammation of the gastrointestinal tract.

Extensive modulation of a set of microRNAs in primary glioblastoma

MicroRNAs (miRNAs) are short non-coding RNA molecules playing regulatory roles in animals and plants by repressing translation or cleaving RNA transcripts. The specific modulation of several microRNAs has been recently associated to some forms of human cancer, suggesting that these short molecules may represent a new class of genes involved in oncogenesis. In our study, we examined by microarray the global expression levels of 245 microRNAs in glioblastoma multiforme, the most frequent and malignant of primary brain tumors. The analysis of both glioblastoma tissues and glioblastoma cell lines allowed us to identify a group of microRNAs whose expression is significantly altered in this tumor. The most interesting results came from miR-221, strongly up-regulated in glioblastoma and from a set of brain-enriched miRNAs, miR-128, miR-181a, miR-181b, and miR-181c, which are down-regulated in glioblastoma.

Hedgehog signaling in normal urothelial cells and in urothelial carcinoma cell lines

Constitutive activation of hedgehog signaling, often caused by PTCH1 inactivation and leading to inappropriate activation of GLI target genes, is crucial for the development of several human tumors including basal cell carcinoma of the skin and medulloblastoma. The PTCH1 gene at 9q22 is also considered as a candidate tumor suppressor in transitional cell carcinoma (TCC), of which >50% show LOH in this region. However, only rare mutations have been found in PTCH1. We have therefore investigated GLI-dependent promoter activity and expression of hedgehog pathway components in TCC cell lines and proliferating normal urothelial cells. Normal urothelial cells cultured in serum-free medium, but not TCC lines exhibited low, but significant promoter activity under standard growth conditions. Accordingly, GLI1-3 and PTCH1 mRNAs were expressed at moderate levels, and sonic hedgehog (SHH) mRNA expression was low to undetectable. In co-transfection experiments GLI1 increased promoter activity significantly in one TCC line and further in normal urothelial cells, but less strongly in other TCC lines. Expression patterns of GLI factor mRNAs did not correlate with inducibility. No significant effects of SHH or cyclopamine on proliferation were observed, ruling out autocrine effects. However, SHH induced GLI-dependent promoter activity in normal urothelial cells. Taken together, our data suggest that the hedgehog pathway is weakly active in normal adult urothelial cells and of limited importance in TCC.

Accelerated Induction of Bladder Cancer inPatchedHeterozygous Mutant Mice

The PATCHED (PTC) gene is recognized as a tumor suppressor in basal cell carcinoma. Mapping of a minimal region of deletion at 9q22.3 and observation of a decreased PTC expression in superficial papillary bladder tumors led us to hypothesize that it could also be involved in this cancer. To further investigate this hypothesis, we submitted Ptc(+/-) heterozygous mutant mice and their wild-type littermates to chemical carcinogenesis by adding N-butyl-N-(4-hydroxybutyl) nitrosamine to their drinking water. Preneoplastic and neoplastic changes were observed significantly earlier in the Ptc(+/-) than in the wild-type mice. Our data support the hypothesis of Ptc acting as a tumor suppressor gene in bladder cancer.

High-resolution analysis of genomic copy number alterations in bladder cancer by microarray-based comparative genomic hybridization

We have screened 22 bladder tumour-derived cell lines and one normal urothelium-derived cell line for genome-wide copy number changes using array comparative genomic hybridization (CGH). Comparison of array CGH with existing multiplex-fluorescence in situ hybridization (M-FISH) results revealed excellent concordance. Regions of gain and loss were defined more accurately by array CGH, and several small regions of deletion were detected that were not identified by M-FISH. Numerous genetic changes were identified, many of which were compatible with previous results from conventional CGH and loss of heterozygosity analyses on bladder tumours. The most frequent changes involved complete or partial loss of 4q (83%) and gain of 20q (78%). Other frequent losses were of 18q (65%), 8p (65%), 2q (61%), 6q (61%), 3p (56%), 13q (56%), 4p (52%), 6p (52%), 10p (52%), 10q (52%) and 5p (43%). We have refined the localization of a region of deletion at 8p21.2-p21.3 to an interval of approximately 1 Mb. Five homozygous deletions of tumour suppressor genes were confirmed, and several potentially novel homozygous deletions were identified. In all, 15 high-level amplifications were detected, with a previously reported amplification at 6p22.3 being the most frequent. Real-time PCR analysis revealed a novel candidate gene with consistent overexpression in all cell lines with the 6p22.3 amplicon.

[The PATCHED/Sonic Hedgehog signalling pathway in superficial bladder cancer]

Superficial bladder cancer shows a high frequency of total or partial chromosome 9 losses. Loss of heterozygosity at position 9q22.3 is one of the most frequent and is associated with highly recurrent tumours. The PATCHED gene, ortholog of a gene first described in the drosophila as a segment polarity gene, is located at 9q22.3. It is a member of a signal transduction pathway and a tumour suppressor gene (TSG), involved in basal cell carcinoma. We propose PATCHED as a TSG candidate in superficial bladder cancer.

Developmental biology informs cancer: the emerging role of the hedgehog signaling pathway in upper gastrointestinal cancers

The hedgehog (Hh) signaling pathway plays many roles in invertebrate and vertebrate development. For example, specific inhibition of sonic Hh expression is critical during early stages of pancreas organogenesis, but an active Hh pathway appears to be required for maintenance of adult endocrine functions. Mutational inactivation of the Hh pathway has been demonstrated in human malignancies of the skin, cerebellum, and skeletal muscle. Now, two papers implicate aberrant Hh signaling in human upper gastrointestinal cancers including those developing from the esophagus, stomach, biliary tract, and pancreas.