Clonality and genetic divergence in multifocal low-grade superficial urothelial carcinoma as determined by chromosome 9 and p53 deletion analysis

17p13 (TP53) Deletions Are Associated With an Aggressive Phenotype but Unrelated to Patient Prognosis in Urothelial Bladder Carcinomas

17p13 deletions including TP53 and other genes represent a common cause for reduced/lost p53 function in tumor cells. In this study, we analyzed the impact of 17p13 (TP53) deletions and p53 expression on tumor aggressiveness and patient prognosis in urothelial carcinoma. The 17p13 copy number status was analyzed by fluorescence in situ hybridization (FISH) on more than 2700 urothelial bladder carcinomas in a tissue microarray format. 17p13 deletion data were compared to p53 expression data measured by immunohistochemistry (IHC) in a previous study. Different types of p53 alterations were compared with tumor phenotype and clinical outcome data. Deletions of 17p13 occurred in 23% of 2185 analyzable carcinomas. The fraction of tumors with 17p13 deletions increased from pTa G2 low (9%) to pTa G3 (24%, p < 0.0001). In muscle-invasive carcinomas, 17p13 deletions were associated with advanced pT stage (p = 0.0246), but unrelated to patient prognosis (p > 0.5). 17p13 deletions were significantly related to p53 immunostaining (p = 0.0375). 17p13 deletions were most common in tumors with complete lack of p53 staining (31%), which supports the concept that many of these tumors have a complete loss of p53 function (p53 null phenotype). 17p13 deletions were also increased in tumors with high p53 staining (25%). In conclusion, 17p13 deletions were most commonly seen in p53 negative cancers, supporting their role as a cause for the p53 null phenotype in urothelial cancer. The association of 17p13 deletions with high grade and advanced pT stage may reflect increasing genomic instability going along with stage and grade progression.

Reconstructing Phylogenetic Relationship in Bladder Cancer: A Methodological Overview

Bladder cancer (BC) expresses itself as a highly heterogeneous disease both at the histological and molecular level, often occurring as synchronous or metachronous multifocal disease with high risk of recurrence and potential to metastasize. Multiple sequencing studies focusing on both non-muscle-invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC) gave insights into the extent of both inter- and intrapatient heterogeneity, but many questions on clonal evolution in BC remain unanswered. In this review article, we provide an overview over the technical and theoretical concepts linked to reconstructing evolutionary trajectories in BC and propose a set of tools and established software for phylogenetic analysis.

Tumor Multifocality is a Significant Risk Factor of Urinary Bladder Recurrence after Nephroureterectomy in Patients with Upper Tract Urothelial Carcinoma: A Single-Institutional Study

The purpose of this study was to identify the significant risk factors of urinary bladder recurrence (UBR) after nephroureterectomy (NUx) in patients with upper tract urothelial carcinoma (UTUC). A total of 550 patients diagnosed with UTUC between January 2001 and December 2015 were included in this retrospective study. The median age of our patients was 68 (range 24–93) and the median follow-up time after NUx was 40.3 months (range 8–191). The most important censored point of this study was the first episode of UBR. Of the 550 patients, UBR occurred in 164 patients (29.8%). One hundred and forty-two (86.6%) patients with UBR were identified within two years after NUx for UTUC, with the median time interval between NUx and UBR being 8.4 months (range 3–59.8). Through univariate analysis, the positive surgical margin (p = 0.049) and tumor multifocality (p = 0.024) were both significant prognostic factors for UBR-free survival after NUx in patients with UTUC. However, only tumor multifocality (p = 0.037) remained a significant prognostic factor by multivariate analysis. In conclusion, tumor multifocality is a significant risk factor of UBR after nephroureterectomy in patients with upper tract urothelial carcinoma.

Molecular changes during progression from nonmuscle invasive to advanced urothelial carcinoma

Molecular changes occurring during invasion and clinical progression of cancer are difficult to study longitudinally in patient‐derived material. A unique feature of urothelial bladder cancer (UBC) is that patients frequently develop multiple nonmuscle invasive tumors, some of which may eventually progress to invade the muscle of the bladder wall. Here, we use a cohort of 73 patients that experienced a total of 357 UBC diagnoses to study the stability or change in detected molecular alterations during cancer progression. The tumors were subtyped by gene expression profiling and analyzed for hotspot mutations in FGFR3, PIK3CA and TERT, the most frequent early driver mutations in this tumor type. TP53 alterations, frequent in advanced UBC, were inferred from p53 staining pattern, and potential genomic alterations were inferred by gene expression patterns at regions harboring frequent copy number alterations. We show that early driver mutations were largely preserved in UBC recurrences. Changes in FGFR3, PIK3CA or TERT mutation status were not linked to changes in molecular subtype and aggressive behavior. Instead, changes into a more aggressive molecular subtype seem to be associated with p53 alterations. We analyze changes in gene expression from primary tumors, to recurrences and progression tumors, and identify two modes of progression: Patients for whom progression is preceded by or coincides with a radical subtype shift, and patients who progress without any systematic molecular changes. For the latter group of patients, progression may be either stochastic or depending on factors already present at primary tumor initiation.

What's new?

Molecular changes occurring during invasion and clinical progression of cancer are difficult to study longitudinally in patient‐derived material. A unique feature of urothelial bladder cancer is that patients frequently develop multiple nonmuscle invasive tumors, some of which may eventually progress to invade the muscle of the bladder wall. Here, the authors perform multi‐level longitudinal analyses on patients with progression from non‐muscle invasive to advanced disease and describe novel modes of progression related to shifts in molecular profiles. Combined with the theory of field cancerization, these results identify limitations in predicting clinical progression based on molecular data from non‐muscle invasive tumors.

Beyond BCG: the approaching era of personalised bladder-sparing therapies for non-muscle-invasive urothelial cancers

Progress in the management of non-muscle invasive bladder cancer has been slow. Despite longstanding use of intravesical therapies (e.g., Bacille Calmette-Guerin; BCG) to complement cystoscopic resection of high-grade lesions, many patients still develop recurrences requiring cystectomy, while others suffer side-effects of BCG without definite benefit. Many questions remain: for example, how many patients receive intravesical prophylaxis without efficacy? Which high-risk patients are best managed with early cystectomy? Could systemic therapies and/or radiotherapy extend bladder preservation times? Such questions may soon be refined by clinicopathologic non-muscle invasive bladder cancer signatures that predict sensitivity to cytotoxic, immune and targeted therapies. Hypothesis-based trials using these signatures should lead to more rational adjuvant treatments, longer bladder preservation times, and better quality of life for patients.

Biomarkers in Bladder Cancer: Present Status and Perspectives

Bladder cancers are a mixture of heterogeneous cell populations, and numerous factors are likely to be involved in dictating their recurrence, progression and the patient's survival. For any candidate prognostic marker to have considerable clinical relevance, it must add some predictive capacity beyond that offered by conventional clinical and pathologic parameters. Here, the current situation in bladder cancer research with respect to identification of suitable prognostic markers is reviewed. A number of individual molecular markers that might predict bladder cancer recurrence and progression have been identified but many are not sufficiently sensitive or specific for the whole spectrum of bladder cancer diseases seen in routine clinical practice. These limitations have led to interest in other molecular parameters that could enable more accurate prognosis for bladder cancer patients. Of particular interest is the epigenetic silencing of tumor suppressor genes. Since the methylation of these genes can correlate with a poor prognosis, the methylation profile may represent a new biomarker that indicates the risk of transitional cell carcinoma development. In addition, bladder cancer research is likely to be revolutionized by high-throughput molecular technologies, which allow rapid and global gene expression analysis of thousands of tumor samples. Initial studies employing these technologies have considerably expanded our ability to classify bladder cancers with respect to their survivability. Future microarray analyses are likely to reveal particular gene expression signatures that predict the likelihood of bladder cancer progression and recurrence, as well as patient's survival and responsiveness to different anti-cancer therapies, with great specificity and sensitivity.

Non-invasive papillary urothelial carcinoma of the vagina: molecular analysis of a rare case identifies clonal relationship to non-invasive urothelial carcinoma of the bladder

We present a rare case of non-invasive papillary urothelial carcinoma of the vagina as the initial presentation of a multicentric urothelial carcinoma also involving bladder and renal pelvis and report for the first time in the literature the molecular alterations observed in the vaginal urothelial lesion and the synchronous lesions of the urinary tract. In this case, the non-invasive papillary urothelial carcinoma in the vagina displayed the same genetic alterations in the FGFR3 and PIK3CA genes as those seen in the non-invasive papillary urothelial carcinoma of the bladder contrasting with the wild phenotype observed in the invasive urothelial carcinoma of the renal pelvis. This observation could reinforce the theory of "seeding" of carcinoma cells as a valid and most likely explanation of this multifocality. In addition, we emphasize in this report the importance of recognizing this rare lesion in the female genital tract and its differential diagnosis.

Immunohistochemical and molecular characterizations in urothelial carcinoma of bladder in patients less than 45 years

Bladder tumours in early-onset patients are rare and seem to exhibit unique clinicopathological features. Only few studies have investigated somatic alterations in this specific age of onset group and evidence is accumulating of a distinct molecular behaviour of early-onset bladder tumours. We collected the largest cohort of early-onset tumours of patients 45 years old or younger and aimed to test genomic alterations typically found in bladder cancer. Tumours of 118 early-onset patients were compared with a consecutive group of 113 cases. Immunohistochemistry of TP53, CK20 and Ki-67 was carried out. Molecular analysis was conducted to test for loss of heterozygosity of chromosome 9 and 17, as well as TP53 and FGFR3 mutations. Fisher´s exact and chi-squared test were appropriately used. No differences in grade/stage characteristics were observed. Overexpressed TP53 was differentially distributed between the two groups. TP53 nuclear accumulation was significantly more frequent in early-onset papillomas, PUNLMPs and pTa low-grade tumours compared to the consecutive cohort (p=0.005). Moreover, chromosome 9 deletions (29.5% vs. 44.6%) and FGFR3 mutations (34.5% vs. 63.7%) were less often detected in early-onset patients (p=0.05 and p<0.0001). By comparing the largest cohort of early-onset bladder cancer patients with an unselected group, we demonstrated that the typical molecular features are not independent of age at diagnosis. Our study supports the hypothesis of a distinct biological behaviour in early-onset tumours.

Spatial and temporal clonal evolution during development of metastatic urothelial carcinoma

Patients with metastatic bladder cancer have a median survival of only 13-14 months. Precision medicine using targeted therapy may improve survival. Here we investigated spatial and temporal tumour evolution and tumour heterogeneity in order to evaluate the potential use of targeted treatment of metastatic bladder cancer. We performed a proof-of-concept study by whole exome sequencing of multiple tumour regions (n = 22) from three patients with metastatic bladder cancer. DNA from primary and metastatic tumour biopsies was analysed for mutations using Mutect and potential therapeutic targets were identified. We identified 256, 265 and 378 somatic mutations per patient, encompassing mutations with an estimated functional impact in 6-12 known disease driver genes per patient. Disease driver mutations present in all tumour regions could be identified in all cases, however, over time metastasis specific driver mutations emerged. For each patient we identified 6-10 potentially therapeutic targets, however very few targets were present in all regions. Low mutational allele frequencies were observed in most regions suggesting a complex mixture of different cancer cells with no spatial demarcation of subclones. In conclusion, primary bladder tumours and metastatic lesions showed heterogeneity at the molecular level, but within the primary tumour the heterogeneity appeared low. The observed lack of potential therapeutic targets common to all cancer cells in primary tumours and metastases emphasizes the challenges in designing rational targeted therapy solely based on analysis of the primary tumours.

Synchronous Endometrial and Ovarian Carcinomas: Evidence of Clonality

Many women with ovarian endometrioid carcinoma present with concurrent endometrial carcinoma. Organ-confined and low-grade synchronous endometrial and ovarian tumors (SEOs) clinically behave as independent primary tumors rather than a single advanced-stage carcinoma. We used 18 SEOs to investigate the ancestral relationship between the endometrial and ovarian components. Based on both targeted and exome sequencing, 17 of 18 patient cases of simultaneous cancer of the endometrium and ovary from our series showed evidence of a clonal relationship, ie, primary tumor and metastasis. Eleven patient cases fulfilled clinicopathological criteria that would lead to classification as independent endometrial and ovarian primary carcinomas, including being of FIGO stage T1a/1A, with organ-restricted growth and without surface involvement; 10 of 11 of these cases showed evidence of clonality. Our observations suggest that the disseminating cells amongst SEOs are restricted to physically accessible and microenvironment-compatible sites yet remain indolent, without the capacity for further dissemination.

Determining the origin of synchronous multifocal bladder cancer by exome sequencing

BACKGROUND

Synchronous multifocal tumours are commonly observed in urothelial carcinomas of the bladder. The origin of these physically independent tumours has been proposed to occur by either intraluminal migration (clonal) or spontaneous transformation of multiple cells by carcinogens (field effect). It is unclear which model is correct, with several studies supporting both hypotheses. A potential cause of this uncertainty may be the small number of genetic mutations previously used to quantify the relationship between these tumours.

METHODS

To better understand the genetic lineage of these tumours we conducted exome sequencing of synchronous multifocal pTa urothelial bladder cancers at a high depth, using multiple samples from three patients.

RESULTS

Phylogenetic analysis of high confidence single nucleotide variants (SNV) demonstrated that the sequenced multifocal bladder cancers arose from a clonal origin in all three patients (bootstrap value 100 %). Interestingly, in two patients the most common type of tumour-associated SNVs were cytosine mutations of TpC* dinucleotides (Fisher's exact test p < 10(-41)), likely caused by APOBEC-mediated deamination. Incorporating these results into our clonal model, we found that TpC* type mutations occurred 2-5× more often among SNVs on the ancestral branches than in the more recent private branches (p < 10(-4)) suggesting that TpC* mutations largely occurred early in the development of the tumour.

CONCLUSIONS

These results demonstrate that synchronous multifocal bladder cancers frequently arise from a clonal origin. Our data also suggests that APOBEC-mediated mutations occur early in the development of the tumour and may be a driver of tumourigenesis in non-muscle invasive urothelial bladder cancer.

Molecular markers in bladder cancer: Novel research frontiers

Bladder cancer (BC) is a heterogeneous disease encompassing distinct biologic features that lead to extremely different clinical behaviors. In the last 20 years, great efforts have been made to predict disease outcome and response to treatment by developing risk assessment calculators based on multiple standard clinical-pathological factors, as well as by testing several molecular markers. Unfortunately, risk assessment calculators alone fail to accurately assess a single patient's prognosis and response to different treatment options. Several molecular markers easily assessable by routine immunohistochemical techniques hold promise for becoming widely available and cost-effective tools for a more reliable risk assessment, but none have yet entered routine clinical practice. Current research is therefore moving towards (i) identifying novel molecular markers; (ii) testing old and new markers in homogeneous patients' populations receiving homogeneous treatments; (iii) generating a multimarker panel that could be easily, and thus routinely, used in clinical practice; (iv) developing novel risk assessment tools, possibly combining standard clinical-pathological factors with molecular markers. This review analyses the emerging body of literature concerning novel biomarkers, ranging from genetic changes to altered expression of a huge variety of molecules, potentially involved in BC outcome and response to treatment. Findings suggest that some of these indicators, such as serum circulating tumor cells and tissue mitochondrial DNA, seem to be easily assessable and provide reliable information. Other markers, such as the phosphoinositide-3-kinase (PI3K)/AKT (serine-threonine kinase)/mTOR (mammalian target of rapamycin) pathway and epigenetic changes in DNA methylation seem to not only have prognostic/predictive value but also, most importantly, represent valuable therapeutic targets. Finally, there is increasing evidence that the development of novel risk assessment tools combining standard clinical-pathological factors with molecular markers represents a major quest in managing this poorly predictable disease.

[Carcinogenic pathways and natural history of upper tract urothelial carcinomas: state-of-the-art review for the yearly scientific report of the French National Association of Urology]

OBJECTIVE

To describe natural history and carcinogenesis of upper tract urothelial carcinoma (UTUC).

METHODS

A systematic review of the scientific literature was performed in the Medline database (Pubmed) using different associations of the following keywords: upper tract urothelial carcinoma; clonality; carcinogenesis; mutation; chromosomal instability; Lynch syndrome; genetic polymorphism.

RESULTS

Local development of UTUC is characterized by a highly prevalent multifocality that might be explained by the overlap of "field change" and "intraluminal seeding and implantation" theories. UTUC and bladder tumors share common carcinogenesis mechanisms such as mutations of FGFR3 and TP53 defining two distinct pathways of pathogenesis. Epigenetic alterations corresponding to the hypermethylation of different promoters regulating genes expression and chromosomal instability such as chromosome 9 deletions are also involved in UTUC carcinogenesis. Furthermore, specific genetic risk factors fro UTUC including Lynch syndrome and different polymorphisms might explain an individual susceptibility for developing these tumors.

CONCLUSIONS

Significant advances have been done in the field of basic research in UTUCs in recent years and have been of particular interest to provide better descriptions of their natural history. Despite these important findings however, some carcinogenic mechanisms remains not elucidated and unknown in the field of UTUC so far.

The relationship of cancer stem cells in urological cancers

Numerous studies are ongoing to identify and isolate cancer stem cells from cancers of genito-urinary tracts. Better understanding of their role in prostate, urothelial and kidney cancer origin, growth and progression opens new pathways in development of more effective treatment methods. However there are still many issues before advances in this field can be introduced for clinical application. This review addresses current achievements in cancer stem cells research in uro-oncology.

Comparison of the clonality of urothelial carcinoma developing in the upper urinary tract and those developing in the bladder

Purpose

To identify the origin of synchronous and metachronous urothelial carcinoma (UC) of the bladder and upper urinary tract to get a better understanding of the basic mechanism behind the multifocality of UC, which may provide a sound bases for the future development of new strategies for detection, prevention and therapy.

Methods

Six patients with UC of the bladder and synchronous or metachronous UC of the upper urinary tract were studied. Genetic analysis involving the study of loss of heterozygosity (LOH) has been evaluated on their tumours using well characterised and new markers of UC (D9S171, D9S177, D9S303 and TP53).

Results

Five of the six patients demonstrated informative results. Four of five (80%) of patients had synchronous or metacharonous UC tumour and showed patterns of LOH consistent with tumorigenesis from monoclonal tumour origin. One of five (20%) patients exhibited a LOH consistent with oligoclonal tumorigenesis.

Conclusion

These findings suggest that both the monoclonal and field cancerization theory of tumorigenesis may play a role in tumors of the urothelial tract. However, more data is needed.

Molecular basis of urinary bladder cancer

Bladder cancer is a relatively common and potentially life-threatening neoplasm. The diagnosis of urothelial carcinoma usually entails a lifelong surveillance to detect recurrent disease. In recent years, significant progress has been made in understanding the molecular mechanisms of carcinogenesis in urinary bladder. An early step in the process of carcinoma development is establishment of a premalignant abnormal urothelial patch that may give rise to various types of urothelial carcinoma and may provide a fertile ground for development of multifocal synchronous and metachronous tumors. Two distinct molecular pathways are involved. Low-grade papillary carcinoma is associated with mutation in the FGFR3 or in some cases mutations in RAS genes. High-grade in situ/muscle-invasive carcinoma on the other hand is characterized by alteration of p53 and pRB. Loss of function of these key genes, which play a crucial role in the control of cell cycle, leads to accumulation of additional mutations and deletions of genes resulting in an aggressive phenotype. It is hoped that a thorough understanding of the molecular basis of urothelial cancer will facilitate early diagnosis and will lead to development of new modalities for the management and treatment of these carcinomas.

Analysis of molecular intra-patient variation and delineation of a prognostic 12-gene signature in non-muscle invasive bladder cancer; technology transfer from microarrays to PCR

Background:

Multiple clinical risk factors and genetic profiles have been demonstrated to predict progression of non-muscle invasive bladder cancer; however, no easily clinical applicable gene signature has been developed to predict disease progression independent of disease stage and grade.

Methods:

We measured the intra-patient variation of an 88-gene progression signature using 39 metachronous tumours from 17 patients. For delineation of the optimal quantitative reverse transcriptase PCR panel of markers, we used 115 tumour samples from patients in Denmark, Sweden, UK and Spain.

Results:

Analysis of intra-patient variation of the molecular markers showed 71% similar classification results. A final panel of 12 genes was selected, showing significant correlation with outcome. In multivariate Cox regression analysis, we found that the 12-gene signature was an independent prognostic factor (hazard ratio=7.4 (95% confidence interval: 3.4–15.9), P<0.001) when adjusting for stage, grade and treatment. Independent validation of the 12-gene panel and the determined cut-off values is needed and ongoing.

Conclusion:

Intra-patient marker variation in metachronous tumours is present. Therefore, to increase test sensitivity, it may be necessary to test several metachronous tumours from a patient’s disease course. A PCR-based 12-gene signature significantly predicts disease progression in patients with non-muscle invasive bladder cancer.

Molecular heterogeneity in malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1

Neurofibromatosis type-1 (NF1), resulting from NF1 gene loss of function, is characterized by an increased risk of developing benign and malignant peripheral nerve sheath tumors (MPNSTs). Whereas the cellular heterogeneity of NF1-associated tumors has been well studied, the molecular heterogeneity of MPNSTs is still poorly understood. Mutational heterogeneity within these malignant tumors greatly complicates the study of the underlying mechanisms of tumorigenesis. We have explored this molecular heterogeneity by performing loss of heterozygosity (LOH) analysis of the NF1, TP53, RB1, PTEN, and CDKN2A genes on sections of 10 MPNSTs derived from 10 unrelated NF1 patients. LOH data for the TP53 gene was found to correlate with the results of p53 immunohistochemical analysis in the same tumor sections. Further, approximately 70% of MPNSTs were found to display intra-tumoral molecular heterogeneity as evidenced by differences in the level of LOH between different sections of the same tumor samples. This study constitutes the first systematic analysis of molecular heterogeneity within MPNSTs derived from NF1 patients. Appreciation of the existence of molecular heterogeneity in NF1-associated tumors is important not only for optimizing somatic mutation detection, but also for understanding the mechanisms of NF1 tumorigenesis, a prerequisite for the development of specifically targeted cancer therapeutics.

Tissue engineering for the oncologic urinary bladder

Urinary diversion after radical cystectomy in patients with bladder cancer normally takes the form of an ileal conduit or neobladder. However, such diversions are associated with a number of complications including increased risk of infection. A plausible alternative is the construction of a neobladder (or bladder tissue) in vitro using autologous cells harvested from the patient. Biomaterials can be used as a scaffold for naturally occurring regenerative stem cells to latch onto to regrow the bladder smooth muscle and epithelium. Such engineered tissues show great promise in urologic tissue regeneration, but are faced with a number of challenges. For example, the differentiation mesenchymal stem cells from various sources can be difficult and the smooth muscle cells formed do not precisely mimic the natural cells.

Pathobiology and chemoprevention of bladder cancer

Our understanding of the pathogenesis of bladder cancer has improved considerably over the past decade. Translating these novel pathobiological discoveries into therapies, prevention, or strategies to manage patients who are suspected to have or who have been diagnosed with bladder cancer is the ultimate goal. In particular, the chemoprevention of bladder cancer development is important, since urothelial cancer frequently recurs, even if the primary cancer is completely removed. The numerous alterations of both oncogenes and tumor suppressor genes that have been implicated in bladder carcinogenesis represent novel targets for therapy and prevention. In addition, knowledge about these genetic alterations will help provide a better understanding of the biological significance of preneoplastic lesions of bladder cancer. Animal models for investigating bladder cancer development and prevention can also be developed based on these alterations. This paper summarizes the results of recent preclinical and clinical chemoprevention studies and discusses screening for bladder cancer.

Bladder cancer: translating molecular genetic insights into clinical practice

Transitional cell (urothelial) carcinoma of the bladder is the second most common urologic malignancy and is one of the best understood neoplasms, with relatively well-defined pathogenetic pathways, natural history, and tumor biology. Conventional clinical and pathologic parameters are widely used to grade and stage tumors and to predict clinical outcome of transitional cell carcinoma; but the predictive ability of these parameters is limited, and there is a lack of indices that could allow prospective assessment of risk for individual patients. In the last decade, a wide range of candidate biomarkers representing key pathways in carcinogenesis have been reported to be clinically relevant and potentially useful as diagnostic and prognostic molecular markers, and as potential therapeutic targets. The use of molecular markers has facilitated the development of novel and more accurate diagnostic, prognostic, and therapeutic strategies. FGFR3 and TP53 mutations have been recognized as key genetic pathways in the carcinogenesis of transitional cell carcinoma. FGFR3 appears to be the most frequently mutated oncogene in transitional cell carcinoma; its mutation is strongly associated with low tumor grade, early stage, and low recurrence rate, which confer a better overall prognosis. In contrast, TP53 mutations are associated with higher tumor grade, more advanced stage, and more frequent tumor recurrences. These molecular markers offer the potential to characterize individual urothelial neoplasms more completely than is possible by histologic evaluation alone. Areas in which molecular markers may prove valuable include prediction of tumor recurrence, molecular staging of transitional cell carcinoma, detection of lymph node metastasis and circulating cancer cells, identification of therapeutic targets, and prediction of response to therapy. With accumulating molecular knowledge of transitional cell carcinoma, we are closer to the goal of bridging the gap between molecular findings and clinical outcomes. Assessment of key genetic pathways and expression profiles could ultimately establish a set of molecular markers to predict the biological nature of tumors and to establish new standards for molecular tumor grading, classification, and prognostication. The main focus of this review is to discuss clinically relevant biomarkers that might be useful in the management of transitional cell carcinoma and to provide approaches in the analysis of molecular pathways that influence the clinical course of bladder cancer.

Analysis of NF1 somatic mutations in cutaneous neurofibromas from patients with high tumor burden

Neurofibromatosis type 1, (NF1) is a complex, autosomal dominant disorder characterized by benign and malignant tumors which result from NF1 gene mutations. The molecular mechanisms that underlie NF1 tumorigenesis are still poorly understood although inactivation of other modifying loci in conjunction with NF1 mutations is postulated to be involved. These modifying loci may include deficiencies in mismatch repair genes and elements involved in cell cycle regulation (TP53, RB1, and CDKN2A). We have analyzed the somatic mutations in 89 cutaneous neurofibromas derived from three unrelated NF1 patients with high tumor burden, by loss of heterozygosity (LOH) analysis of the NF1, TP53, RB1, and CDKN2A genes, by assessing microsatellite instability (MSI), by direct sequencing of the NF1, TP53, and several mismatch repair (MMR) genes and by multiplex ligation-dependent probe amplification of the NF1 and TP53 genes. The aim was both to assess the possible clonality of these tumors and also to assess the involvement of other potential genetic loci in the development of these neurofibromas. Somatic NF1 mutations were identified in 57 (64%) of neurofibroma samples. Each mutation was distinct demonstrating the independent origin of each tumor. While somatic LOH of the TP53 gene was identified in four tumors, no specific deletions or sequence variations were identified. LOH of markers flanking the RB1 gene was also found in one tumor but no CDKN2A mutations were detected. Although evidence of MSI was seen in 21 tumors, no MMR gene alterations were identified. The identification of LOH involving TP53 and RB1 loci is a novel finding in benign cutaneous neurofibromas possibly demonstrating an alternative underlying molecular mechanism associated with the development of these benign tumors from this cohort of patients.

Staging and reporting of urothelial carcinoma of the urinary bladder

Significant progress has been made in the standardization of bladder neoplasm classification and reporting. Accurate staging using the American Joint Committee on Cancer/International Union Against Cancer (AJCC/UICC) TNM system is essential for patient management, and has been reinforced by clinical evidence in recent years. It is now recognized that 'superficial' bladder carcinomas are a heterogenous group of tumors with diverse biological and clinical manifestations. The term 'superficial,' therefore, is no longer used for bladder tumor nomenclature. Recognition of diagnostic pitfalls associated with lamina propria invasion is critical for the evaluation of bladder tumor specimens. Neither the 1973 nor the 2004 WHO grading system appears to be useful for predicting the clinical outcome of invasive urothelial carcinoma. This review will discuss recent progress and controversial issues on the staging and substaging of bladder carcinomas. Essential elements for handling and reporting of bladder tumor specimens will also be discussed.

Coexistent intraurothelial carcinoma and muscle-invasive urothelial carcinoma of the bladder: clonality and somatic down-regulation of DNA mismatch repair

Muscle-invasive urothelial carcinomas are heterogeneous neoplasms for which the clonal relationship with low-grade urothelial dysplasia and carcinomas in situ remains unknown, and both monoclonal and field change models have been proposed. Low-grade dysplasia (18) and carcinoma in situ (12) associated with muscle-invasive urothelial carcinoma were microdissected and topographically analyzed (intraepithelial and invasive superficial and deep to muscularis mucosa) for methylation pattern of androgen receptor alleles, TP53, RB1, WT1, and NF1 microsatellite analysis to assess clonal identity; MLH1 and MSH2 sequencing/immunostaining. Appropriate controls were run. Carcinoma in situ (100%) and invasive urothelial carcinoma (100%) revealed monoclonal patterns, whereas low-grade dysplasia was preferentially polyclonal (80%). Carcinoma in situ showed aneuploid DNA content and more abnormal microsatellites than the corresponding invasive compartments, opposite to low-grade dysplasia. Absent MLH1 protein expression with no gene mutations were identified in carcinoma in situ and nodular-trabecular urothelial carcinoma with high microsatellite abnormalities. Somatic mismatch repair protein down-regulation and the accumulation of tumor suppressor gene microsatellite abnormalities contribute to a molecular evolution for monoclonal carcinoma in situ divergent from coexistent muscle-invasive urothelial carcinoma. Low-grade dysplasia is however unlikely connected with this molecular progression.

Molecular biomarkers in urothelial bladder cancer

Bladder cancers are a mixture of heterogeneous cell populations, and numerous factors are likely to be involved in dictating their recurrence, progression, and the patient's survival. For any candidate prognostic marker to have considerable clinical relevance, it must add some predictive capacity beyond that offered by the conventional clinical and pathological parameters. None of the biomarkers reported to date have shown sufficient sensitivity and specificity for detecting the whole spectrum of bladder cancer diseases in routine clinical practice. The limitations of established prognostic markers requires us to identify better molecular parameters that could be of interest in predicting the prognosis of bladder cancer patients, in particular, the high-risk patient groups that are at risk of progression and recurrence. Recent progress in epigenetic modification and gene silencing opened a new avenue for the identification of epigenetic markers, which appears to be more useful for cancer diagnosis and prognosis. Although epigenetic markers also have limitations, the combined epigenetic marker approach may increase sensitivity and reliability. The epigenetic silencing of tumor-suppressor genes is interesting from a clinical standpoint because of the possibility of reversing epigenetic changes and restoring gene function in a cell. In addition, microarray technology provides us with additional tools for the analysis of global gene-expression analysis of tumor samples. Future microarray analyses are likely to reveal particular gene-expression signatures that predict the likelihood of bladder cancer progression and recurrence, as well as a patient's survival and responsiveness to different anticancer therapies, with great specificity and sensitivity.

A Hidden Markov Model to estimate population mixture and allelic copy-numbers in cancers using Affymetrix SNP arrays

Background

Affymetrix SNP arrays can interrogate thousands of SNPs at the same time. This allows us to look at the genomic content of cancer cells and to investigate the underlying events leading to cancer. Genomic copy-numbers are today routinely derived from SNP array data, but the proposed algorithms for this task most often disregard the genotype information available from germline cells in paired germline-tumour samples. Including this information may deepen our understanding of the "true" biological situation e.g. by enabling analysis of allele specific copy-numbers. Here we rely on matched germline-tumour samples and have developed a Hidden Markov Model (HMM) to estimate allelic copy-number changes in tumour cells. Further with this approach we are able to estimate the proportion of normal cells in the tumour (mixture proportion).

Results

We show that our method is able to recover the underlying copy-number changes in simulated data sets with high accuracy (above 97.71%). Moreover, although the known copy-numbers could be well recovered in simulated cancer samples with more than 70% cancer cells (and less than 30% normal cells), we demonstrate that including the mixture proportion in the HMM increases the accuracy of the method. Finally, the method is tested on HapMap samples and on bladder and prostate cancer samples.

Conclusion

The HMM method developed here uses the genotype calls of germline DNA and the allelic SNP intensities from the tumour DNA to estimate allelic copy-numbers (including changes) in the tumour. It differentiates between different events like uniparental disomy and allelic imbalances. Moreover, the HMM can estimate the mixture proportion, and thus inform about the purity of the tumour sample.

Low frequency of molecular changes and tumor recurrence in inverted papillomas of the urinary tract

AIM

Inverted papilloma (IP) of the urinary tract can be difficult to distinguish from noninvasive urothelial carcinoma with prominent inverted growth pattern (invNIUC). Ancillary markers may help to resolve such cases and clarify the reported malignant potential of some IPs.

METHODS

Eighty-nine urothelial lesions initially diagnosed as IP were reviewed by 4 experienced urologic pathologists and studied immunohistochemically (Ki67, p53, CK20, MSH2, MLH1, and MSH6). Mutations of the FGFR3 gene, deletions (loss of heterozygosity) of 9p, 9q, and 17p, microsatellite instability, and elevated microsatellite instability at selected tetranucleotides were also analyzed.

RESULTS

Considerable interobserver variability in histopathologic diagnoses was noticed. Only 62 (69.7%) initial diagnoses were confirmed by the review pathologists whereas 23 tumors (25.8%) were redefined as invNIUC. Molecular analyses revealed infrequent alterations in IPs, including microsatellite instability (1.8%), elevated microsatellite instability at selected tetranucleotides (13.2%), FGFR3 mutations (9.8%), 9p deletions (3.9%), 9q deletions (13.2%), 17p deletions (5.1%), nuclear p53 accumulation (18.9%), and aberrant immunostaining for MSH2 (5.8%), MLH1 (11.8%), and MSH6 (3.8%). IP and invNIUC differed in FGFR3 mutations and Ki-67 labeling index (P<0.001 each), and 9q loss of heterozygosity (P=0.03). There were fewer recurrences in IP (5.4%) compared with invNIUC (40.9%; P<0.0001).

CONCLUSIONS

IP is a benign lesion that lacks specific genetic alterations found in exophytic noninvasive papillary urothelial tumors. These lesions could be reactive in nature, perhaps secondary to chronic inflammation or a neoplastic process that lack specific genetic alterations. Nevertheless given the clinical and molecular data of this study a conservative clinical approach is appropriate.

Expression of DNA repair and metabolic genes in response to a flavonoid-rich diet

A diet rich in fruit and vegetables can be effective in the reduction of oxidative stress, through the antioxidant effects of phytochemicals and other mechanisms. Protection against the carcinogenic effects of chemicals may also be exerted by an enhancement of detoxification and DNA damage repair mechanisms. To investigate a putative effect of flavonoids, a class of polyphenols, on the regulation of the gene expression of DNA repair and metabolic genes, a 1-month flavonoid-rich diet was administered to thirty healthy male smokers, nine of whom underwent gene expression analysis. We postulated that tobacco smoke is a powerful source of reactive oxygen species. The expression level of twelve genes (APEX, ERCC1, ERCC2, ERCC4, MGMT, OGG1, XPA, XPC, XRCC1, XRCC3, AHR, CYP1A1) was investigated. We found a significant increase (P < 0.001) in flavonoid intake. Urinary phenolic content and anti-mutagenicity did not significantly change after diet, nor was a correlation found between flavonoid intake and urinary phenolic levels or anti-mutagenicity. Phenolic levels showed a significant positive correlation with urinary anti-mutagenicity. AHR levels were significantly reduced after the diet (P = 0.038), whereas the other genes showed a generalized up regulation, significant for XRCC3 gene (P = 0.038). Also in the context of a generalized up regulation of DNA repair genes, we found a non-significant negative correlation between flavonoid intake and the expression of all the DNA repair genes. Larger studies are needed to clarify the possible effects of flavonoids in vivo; our preliminary results could help to better plan new studies on gene expression and diet.

Genomic aberrations are rare in urothelial neoplasms of patients 19 years or younger

Urothelial neoplasms in patients 19 years of age or younger are rare, and the data regarding clinical outcome are conflicting. Molecular data are not available. Urothelial tumours from 14 patients aged 4 to 19 years were analysed, including FGFR3 and TP53 mutation screening, comparative genomic hybridization (CGH), UroVysion FISH analysis, polymerase chain reaction for human papillomavirus (HPV), microsatellite analysis using the NIH consensus panel for detection of microsatellite instability (MSI) and six markers for loss of heterozygosity on chromosome arms 9p, 9q, and 17p and immunohistochemistry for TP53, Ki-67, CK20 and the mismatch repair proteins (MRPs) hMSH2, hMLH1, and hMSH6. Based on the 2004 WHO classification, one urothelial papilloma, seven papillary urothelial neoplasms of low malignant potential (PUNLMPs), five low-grade, and one high-grade papillary urothelial carcinoma were included. No multifocal tumours were found and recurrence was seen in only one patient with a urothelial papilloma. All patients were alive with no evidence of disease at a median follow-up of 3.0 years. We found no mutations in FGFR3, deletions of chromosome arms 9p, 9q or 17p, MSI or MRP loss, or HPV positivity in any of the patients. Three cases showed chromosome alterations in CGH analyses, urothelial dedifferentiation with CK20 overexpression, or aneuploidy, and one TP53 mutation with TP53 overexpression was found. Urothelial neoplasms in people younger than 20 years are predominantly low grade and are associated with a favourable clinical outcome. Genetic alterations frequently seen in older adults are extremely rare in young patients. Urothelial neoplasms in children and young adults appear to be biologically distinct and lack genetic instability in most cases.

On the origin of syn- and metachronous urothelial carcinomas

OBJECTIVE

To evaluate existing models for the origin of meta- and synchronous urothelial carcinomas in light of the accumulated genetic data.

METHODS

Published studies on the clonal origin and genetic relationships of syn- and metachronous tumors, genetic aberrations in normal and premalignant urothelial lesions, as well as histologic and genetic mapping studies of cystectomized bladder samples are reviewed.

RESULTS

The most common models for the origin of syn- and metachronous tumors are found to conform less well to the accumulated genetic data. A new model is proposed, the field-first-tumor-later model, in which aberrant cells with a stem cell, or stem cell-like, origin spread in the urothelium by cellular displacement, creating fields of premalignant cells. Tumor growth is suggested to be initiated by critical genetic events occurring in individual cells in such fields. Hence, recurring tumors are proposed to originate from a shared field of premalignant cells and not from previous overt tumors.

CONCLUSIONS

The proposed model can better account for the existing genetic and histological data on syn- and metachronous urothelial carcinomas.

Chromosome 9 deletions are more frequent than FGFR3 mutations in flat urothelial hyperplasias of the bladder

Flat urothelial hyperplasias (FUHs) in patients with papillary bladder tumours frequently show deletions of chromosome 9, suggesting that FUH could be the first neoplastic step in the development of papillary bladder cancer. FGFR3 mutations are frequent in non-invasive papillary tumours with low risk of progression. Our aim was to investigate the frequency of FGFR3 mutations and deletions of chromosomes 9p/q and 8p/q in FUH. Thirty FUH and 9 simultaneous or consecutive tumours were detected by 5-ALA-based photodynamic cystoscopy. DNA was isolated from frozen sections and whole genome amplification was done by I-PEP-PCR, followed by LOH analysis on chromosomes 8p/q and 9p/q. FGFR3 mutations were detected by SNaPshot analysis. LOH analysis on FUH revealed deletions at 9p/q (11/30, 37%) and 8p/q (3/30, 10%). FGFR3 mutations were found in 7/30 FUH (23%). Only 2 FUH showed an FGFR3 mutation without deletions of chromosome 9. In contrast, 6 FUH revealed chromosome 9 deletions but wild type FGFR3 (p = 0.03). These results suggest that chromosome 9 deletions are the earliest genetic alterations in bladder cancer. The detection of FGFR3 mutations in FUH further supports the role of this lesion as precursor of papillary bladder cancer.

Comparison of allelic losses in chondroblastoma and primary chondrosarcoma of bone and correlation with fluorescence in situ hybridization analysis

Chondroblastoma (CBL) is a benign neoplasm of bone for which the genomic characteristics remain unclear. We compared the status of allelic losses of CBL with that seen in a set of chondrosarcomas (CS) to determine whether differences in their natural history and behavior are also reflected genetically. Eleven cases of CBL and 10 cases of CS of different grades were included. Tumors were subjected to microdissection and polymerase chain reaction using 17 markers located near genes on chromosomes 5, 9, 11, 13, 17, and 19. The selected chromosomes are known to be involved in several mesenchymal neoplasms. Fluorescence in situ hybridization was also performed on tumors displaying allelic losses, with dual-color probes for 9p, 17p, and 13q. Fractional allelic losses per gene ranged from 18.2% to 63.7% in CBLs and from 28.6% to 66.7% in CSs. Loss of heterozygosity (LOH) of 5q, 9p, 11p, 13q, and 19q occurred in both CBLs and CSs. Loss of heterozygosity of 17p (p53 locus) occurred in 7 of 11 CBLs and in only 1 case of recurrent CS. The pattern of allelic loss was similar in low-grade CSs and CBLs. Loci with LOH in both tumor types suggest possible involvement of the genes p53, RB1, CDKN2/p16, ERC, and XRCC in tumorigenesis. Overall correlation between LOH and fluorescence in situ hybridization results was 90% with 17p13, 80% with 9p, and 60% with 13q. The role of p53 in CBL is uncertain; however, given the benign behavior of this tumor, it is probably unrelated to tumor progression.

Intratumoral DNA stem-line heterogeneity in superficial spreading melanoma

BACKGROUND

In primary melanomas, data on the degree of intratumoral heterogeneity to date have been lacking.

OBJECTIVE

Our purpose was to investigate intratumoral DNA stem-line heterogeneity in superficial spreading melanoma (SSM).

METHODS

Multiple measuring fields of 54 SSMs (tumor thickness median 1.60 mm) were studied by DNA image cytometry to obtain data on the number of DNA stem lines per tumor, their ploidy characteristics, and intratumoral distribution. Results were compared with standard histopathological criteria.

RESULTS

Twenty-three of 54 SSMs were found to have two or three distinct proliferating tumor cell stem lines (1.46 +/- 0.57 per tumor). Stem lines appeared spatially separated in 22 of 23 SMMs. At least 3 measuring fields per tumor were necessary to identify all stem lines with a likelihood of 95%. DNA heterogeneity correlated with tumor thickness, but occurred in 5 of 19 cases of pT1 melanoma.

CONCLUSIONS

Primary SSMs can be regarded as potentially clonally unstable with a tendency for spatial separation of tumor cell stem lines.

Bladder cancer, a two phased disease?

The processes of intraepithelial migration, intraluminal seeding, and field cancerization as models for initiation, spread, and recurrences of urothelial cell carcinoma (UCC) are reviewed in light of recent molecular investigations. The accumulated molecular data on synchronous and metachronous tumors indicate that the majority of recurrent and multiple tumors are monoclonal. Molecular data has also shown the presence of chromosomal and genetic changes in precursor lesions as well as in normal urothelial cells. Genetic-histological mapping of cystectomized bladders has shown that overt tumors occur as local events in areas of genetically altered urothelium. A model is put forward in which the tumor process is initiated by genetically altered but histologically normal cells that produce fields of altered cells by intraepithelial displacement. By the accumulation of further genetic changes the fields of altered urothelium reaches a state of criticality, which locally may produce frank tumors.

Improved clonality analysis of multifocal bladder tumors by combination of histopathologic organ mapping, loss of heterozygosity, fluorescence in situ hybridization, and p53 analyses

The clonality status of multifocal bladder tumors is still controversially discussed with experimental evidence for both monoclonality and field cancerization. Methodologically, loss of heterozygosity (LOH) and genomic sequencing analyses are widely used in clonality analysis of malignant tumors. In the present study, we used LOH analysis and genomic sequencing in combination with fluorescence in situ hybridization (FISH) and extensive histopathologic whole-organ mapping to determine the clonal relationship of multifocal bladder cancer disease. Tissue sections (1 cm(2)) covering the entire urothelial lining were systematically dissected from 2 cystectomy specimens (cystectomy 1, no urothelial lesions, bladder infiltration by a leiomyosarcoma of the vaginal wall; cystectomy 2, multifocal pT3G3 tumors). The location of each sample was documented (bladder mapping). Urothelial cells were microdissected for LOH (chromosomes 9, 17p) and FISH analysis (CDKI2 (9p21), FACC (9q22), p53 (17p13.1), and centromeric probes for corresponding chromosome). Exons 5 to 9 of the p53 gene were sequenced in all tumor samples. No chromosomal alterations were detected in the cystectomy specimen without urothelial malignancies. The tumor-bearing bladder showed an increasing frequency of deletions with increasing malignancy of the investigated lesions. LOH analysis detected deletions only on chromosomes 9p and 17p. In contrast, FISH analysis revealed deletions of all investigated genes at chromosomes 9p, 9q, and 17p in all samples analyzed (preneoplastic and neoplastic tissue). An identical p53 mutation in codon 281 was found in all 7 analyzable tumor samples. Combination of molecular data with histopathologic bladder mapping suggested a monoclonal development of the multifocal lesions mostly via intraurothelial migration. Our data strengthen the results from recently published studies that patients with advanced urothelial carcinoma seem to have a monoclonal panurothelial disease in most cases. FISH showed a much higher sensitivity for detection of chromosomal losses than classical LOH analysis, especially in preneoplastic and small lesions. Combining 3 molecular approaches together with histopathologic organ mapping presents a valuable tool to determine the clonality status of multifocal bladder tumors.

Persistence, recurrence, and progression rates of superficial bladder tumours after resection using the differentiated technique

OBJECTIVE

To investigate whether the differentiated resection technique for excising superficial bladder cancer leads to higher recurrence and progression rates as compared with regular resection.

SUBJECTS AND METHODS

We evaluated 163 patients, 66 undergoing a differentiated and 97 a regular resection. All patients underwent a routine second resection within 6-10 weeks. Recurrence and progression rates as well as tumour persistence on second resection were analyzed.

RESULTS

Patients with differentiated resections of bladder tumours did not have higher tumour recurrence and progression rates. Also, these patients had a significantly higher percentage of tumour-free second resections (p = 0.03).

CONCLUSION

The differentiated resection technique for excising superficial bladder cancer has no negative influence on recurrence and progression rates, but it leads to a reduced tumour persistence.

Origin of multifocal carcinomas of the bladder and upper urinary tract: molecular analysis and clinical implications

The simultaneous or metachronous development of multifocal tumors with identical or variable histological features in the urothelial tract in a single patient is a well-known characteristic of urothelial cancer. To explain this phenomenon, two distinct concepts have been proposed: the 'field defect' hypothesis according to which urothelial cells in patients are primed to undergo transformation by previous carcinogenic insults and the 'single progenitor cell' hypothesis, which asserts that the multifocal development is caused by the seeding or intraepithelial spread of transformed cells. Results of recent molecular genetic studies support the 'single progenitor cell' hypothesis, and indicate that the genetic and phenotypic diversity observed in multifocal urothelial tumors is a consequence of clonal evolution from a single transformed cell. An understanding of the mechanism of the heterotopic recurrence of urothelial cancer may provide new prospects for early molecular detection and prevention of heterotopic recurrence of urothelial cancer.

Analysis of genetic events in 17p13 and 9p21 regions supports predominant monoclonal origin of multifocal and recurrent bladder cancer

Clonality was tested in 86 tumours from 25 patients with recurrent and multifocal superficial bladder transitional cell carcinomas (TCCs) using the analysis of TP53 mutations and of LOH in the 17p13 and 9p21 regions. Tumours from the majority of individuals showed either absence or presence of the same TP53 mutation and/or an identical LOH pattern, with the same allele lost in all tumours. Only two pairs of tumours from two patients had discordant findings, which were incompatible with monoclonality. Therefore, our results rather support the monoclonal model of development of highly recurrent superficial bladder TCCs.

Molecular evidence supporting field effect in urothelial carcinogenesis

PURPOSE

Human urothelial carcinoma is thought to arise from a field change that affects the entire urothelium. Multifocality of urothelial carcinoma is a common finding at endoscopy and surgery. Whether these coexisting tumors arise independently or are derived from the same tumor clone is uncertain. Molecular analysis of microsatellite alterations and X-chromosome inactivation status in the cells from each coexisting tumor may further our understanding of urothelial carcinogenesis.

EXPERIMENTAL DESIGN

We examined 58 tumors from 21 patients who underwent surgical excision for urothelial carcinoma. All patients had multiple separate foci of urothelial carcinoma (two to four) within the urinary tract. Genomic DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-capture microdissection. Loss of heterozygosity (LOH) assays for three microsatellite polymorphic markers on chromosome 9p21 (IFNA and D9S171), regions of putative tumor suppressor gene p16, and on chromosome 17p13 (TP53), the p53 tumor suppressor gene locus, were done. X-chromosome inactivation analysis was done on the urothelial tumors from 11 female patients.

RESULTS

Seventeen of 21 (81%) cases showed allelic loss in one or more of the urothelial tumors in at least one of the three polymorphic markers analyzed. Concordant allelic loss patterns between each coexisting urothelial tumor were seen in only 3 of 21 (14%) cases. A concordant pattern of nonrandom X-chromosome inactivation in the multiple coexisting urothelial tumors was seen in only 3 of 11 female patients; of these 3 cases, only one displayed an identical allelic loss pattern in all of the tumors on LOH analysis.

CONCLUSION

LOH and X-chromosome inactivation assays show that the coexisting tumors in many cases of multifocal urothelial carcinoma have a unique clonal origin and arise from independently transformed progenitor urothelial cells, supporting the "field effect" theory for urothelial carcinogenesis.

Loss of heterozygosity on chromosome 9q and p53 alterations in human bladder cancer

BACKGROUND

Somatic loss of the 9q allele as well as alteration of the tumor suppressor p53 occurs commonly in bladder cancers. Although alteration of p53 has been strongly associated with invasive stage disease, the prognostic significance of 9q loss of heterozygosity (LOH) and the relations between these alterations are less well defined.

METHODS

The 9q LOH was examined at five microsatellites and p53 alterations (mutation and persistent immunohistochemical staining) in a population-based case series of 271 newly diagnosed bladder cancer patients. Loss of heterozygosity was scored quantitatively and p53 mutation completed using single-strand conformation polymorphism screening followed by sequencing.

RESULTS

Overall, allelic loss at 9q was detected in 74.5% (202/271) of cases and allele loss was associated with invasive disease (P < 0.05). Although based on small numbers, all nine in situ lesions contained 9q LOH. Age, gender, and smoking were not significantly associated with chromosome 9q allele loss. Both intense persistent p53 staining and LOH at 9q were independently associated with invasive disease (P < 10(-14) and P < 0.05, respectively).

CONCLUSIONS

These data, using a population-based sample, suggest a relation between 9q LOH and invasive stage bladder cancer, and thereby suggests that a tumor suppressor gene at this loci, in addition to p53, may be important in the development of this more aggressive form of the disease.

Diagnosis of urothelial carcinoma of the bladder using fluorescence endoscopy

Bladder cancer is a frequent disease and represents the second most common genitourinary neoplasm. Although many aspects of the management of superficial bladder cancer are now well established, significant challenges remain, which influences patient outcome. Early detection and treatment of recurrent disease is required to optimize bladder preservation, reduce patient morbidity, and increase quality of life and survival. Fluorescence endoscopy, often referred to as 'photodynamic diagnosis' (PDD), with intravesical application of photosensitizing agents, has been developed to enhance the early detection of bladder cancer. There is growing evidence that PDD using 5-aminolaevulinic acid (ALA), hexyl-ALA ester or hypericin enhances the detection of bladder cancer, particularly of high-grade flat lesions. Furthermore, transurethral resection of bladder tumour under fluorescence guidance reduces the risk of recurrent tumours. However, the impact on the progression of disease remains unclear and must be investigated in prospective randomized trials.

On the emergence of multifocal cancers

Several tumors can exist as multiple lesions within a tissue. The lesions may either arise independently, or they may be monoclonal. The importance of multiple lesions for tumor staging, progression, and treatment is subject to debate. Here we use mathematical models to analyze the emergence of multiple, clonally related lesions within a single tissue. We refer to them as multi-focal cancers. We find that multifocal cancers can arise through a dynamical interplay between tumor promoting and inhibiting factors. This requires that tumor promoters act locally, while tumor inhibitors act over a longer range. An example of such factors may be angiogenesis promoters and inhibitors. The model further suggests that multifocal cancers represent an intermediate stage in cancer progression as the tumor evolves away from inhibition and towards promotion. Different patterns of progression can be distinguished: (i) If tumor inhibition is strong, the initial growth occurs as a unifocal and self contained lesion; progression occurs through bifurcation of the lesion and this gives rise to multiple lesions. As the tumor continues to evolve and pushes the balance between inhibition and promotion further towards promotion, the multiple lesions eventually give rise to a single large mass which can invade the entire tissue. (ii) If tumor inhibition is weaker upon initiation, growth can occur as a single lesion without the occurrence of multiple lesions, until the entire tissue is invaded. The model suggests that the sum of the tumor sizes across all lesions is the best characteristic which correlates with the stage and metastatic potential of the tumor.