Consistent genomic alterations in carcinoma in situ of the urinary bladder confirm the presence of two major pathways in bladder cancer development

Comparative analysis of non-coding and coding DNA mutations in flat urothelial lesions: biological implications and insights

Recent research in urothelial carcinoma (UC) has focused on coding mutations, leaving the significance of non-coding mutations unexplored. This study aims to evaluate non-coding DNA mutation frequencies compared to coding regions in normal urothelium and flat lesions, exploring their implications for tumor biology. Using targeted next-generation sequencing with UC-related gene panel, we analyzed non-coding and coding DNA mutation frequencies across 119 samples of flat urothelium encompassing various lesion types. Mutation patterns were examined based on the presence of associated flat or papillary tumors, and we investigated the correlation between mutation rates in target genes and genetic mutations within genomic regions. Intronic mutations (IMs) displayed variability across lesions, with normal urothelium (NU) exhibiting the highest frequency (43%) and urothelial carcinoma in situ (CIS) the lowest (9%). We observed similar sets of frequently mutated genes in both intronic and exonic regions, distinct from promoter region mutations. Although IMs paralleled exonic mutations in NU, reactive atypia, and atypia of unknown significance (AUS), they were less prevalent in dysplasia (DYS) and CIS. In contrast to CIS-associated AUS and DYS lesions, AUS-DYS lesions associated with papillary tumors exclusively exhibited recurrent intronic mutations involving FGFR3 and ERCC2, aligning with mutation patterns seen in exonic regions. ERCC2 intronic mutations correlated with the mutation rates of the gene panel. Our findings suggest that intronic mutations significantly contribute to tumor heterogeneity in urothelial lesions and may potentially be linked to genomic instability, warranting further investigation.

Targeted Next-Generation Sequencing of Flat Urothelial Lesions Reveals Putative Pathobiological Pathways, Potential Biomarkers, and Rational Therapeutic Targets

Flat urothelial lesions are controversial diagnostic and prognostic urologic entities whose importance relies mainly on their ability to progress to muscle-invasive tumors via urothelial carcinoma in situ (CIS). However, the carcinogenetic progression of preneoplastic flat urothelial lesions is not well established. Moreover, predictive biomarkers and therapeutic targets of the highly recurrent and aggressive urothelial CIS lesion are lacking. Using a targeted next-generation sequencing (NGS) panel of 17 genes directly involved in bladder cancer pathogenesis, we investigated alterations of genes and pathways with clinical and carcinogenic implications on 119 samples of flat urothelium, including normal urothelium (n = 7), reactive atypia (n = 10), atypia of unknown significance ( n = 34), dysplasia ( n = 23), and CIS (n = 45). The majority of the flat lesions were tumor-associated but grossly/microscopically or temporally separated from the main tumor. Mutations were compared across flat lesions and concerning the concomitant urothelial tumor. Associations between genomic mutations and recurrence after intravesical bacillus Calmette-Guerin treatment were estimated with Cox regression analysis. TERT promoter mutations were highly prevalent in intraurothelial lesions but not in the normal or reactive urothelium, suggesting that it is a critical driver mutation in urothelial tumorigenesis. We found that synchronous atypia of unknown significance-dysplasia-CIS lesions without concomitant papillary urothelial carcinomas had a similar genomic profile that differed from atypia of unknown significance-dysplasia lesions associated with papillary urothelial carcinomas, which harbored significantly more FGFR3, ARID1A, and PIK3CA mutations. KRAS G12C and ERBB2 S310F/Y mutations were exclusively detected in CIS and were associated with recurrence after bacillus Calmette-Guerin treatment (P = .0006 and P = .01, respectively). This targeted NGS study revealed critical mutations involved in the carcinogenetic progression of flat lesions with putative pathobiological pathways. Importantly, KRAS G12C and ERBB2 S310F/Y mutations were identified as potential prognostic and therapeutic biomarkers for urothelial carcinoma.

Animal Models in Bladder Cancer

BACKGROUND

Bladder cancer (urothelial cancer of the bladder) is the most common malignancy affecting the urinary system with an increasing incidence and mortality. Mouse models of bladder cancer should possess a high value of reproducibility, predictability, and translatability to allow mechanistic, chemo-preventive, and therapeutic studies that can be furthered into human clinical trials.

OBJECTIVES

To provide an overview and resources on the origin, molecular and pathological characteristics of commonly used animal models in bladder cancer.

METHODS

A PubMed and Web of Science search was performed for relevant articles published between 1980 and 2021 using words such as: "bladder" and/or "urothelial carcinoma" and animal models. Animal models of bladder cancer can be categorized as autochthonous (spontaneous) and non-autochthonous (transplantable). The first are either chemically induced models or genetically engineered models. The transplantable models can be further subclassified as syngeneic (murine bladder cancer cells implanted into immunocompetent or transgenic mice) and xenografts (human bladder cancer cells implanted into immune-deficient mice). These models can be further divided-based on the site of the tumor-as orthotopic (tumor growth occurs within the bladder) and heterotopic (tumor growth occurs outside of the bladder).

Oncological outcomes of concomitant carcinoma in situ at radical cystectomy in pure urothelial bladder cancer and in histological variants

INTRODUCTION

The presence of carcinoma in situ at transurethral resection is known to increase the risk of recurrence and progression to invasive disease. However, the evidence regarding the prognostic role of concomitant carcinoma in situ after radical cystectomy due to bladder cancer is controversial. Moreover, concomitant carcinoma in situ was found to be significantly associated with bladder histological variants. The aim of our study is to evaluate whether the presence of concomitant carcinoma in situ at radical cystectomy, impacts on recurrence and survival outcomes in pure urothelial bladder cancer, compared to histological variants.

METHODS

We evaluated 410 consecutive patients diagnosed with non-metastatic bladder cancer and treated with radical cystectomy at a single tertiary referral centre between January 2009 and May 2019. Patients were stratified according to the presence of carcinoma in situ. The Kaplan-Meier method was used to compare recurrence free, cancer specific and overall survival in pure urothelial and histological variants. Cox proportional hazards regression analyses model was used to predict recurrence, cancer specific and overall mortality in pure urothelial and histological variants bladder cancer, according to pathological stage.

RESULTS

Median age was 71 years. 340 patients (82%) were male. At a median follow-up of 32 months, disease recurrence, cancer specific mortality and overall mortality were, 37% (155 patients), 32.9% (135 patients) and 46.6% (191 patients), respectively. Concomitant and pure carcinoma in situ were found in 39% and 19% of radical cystectomy specimens, respectively. Concomitant carcinoma in situ was more frequent in patients with histological variants (50.9%) compared to pure urothelial bladder cancer (35.4%) (P-value <.001) and was associated with worst pathological features (lymphovascular invasion, lymph node involvement and non-organ confined disease). Recurrence free survival at Kaplan-Meyer analyses was significantly higher in patients with pure carcinoma in situ compared to those with concomitant or no carcinoma in situ (all P <.001), similarly for patients without carcinoma in situ compared with those with concomitant Cis (P =.02) at radical cystectomy. Cancer specific and overall survival were significantly higher in patients with pure carcinoma in situ compared to those with concomitant or no carcinoma in situ (all P <.001). Conversely no significant difference was found between patients without carcinoma in situ and with concomitant carcinoma in situ (P>0.1) at radical cystectomy Moreover, concomitant carcinoma in situ at radical cystectomy in histological variants is associated with higher free recurrence rate compared to the other groups. At multivariate Cox proportional hazards regression analyses the presence of carcinoma in situ at radical cystectomy was not associated with any survival effect or recurrence (all P > .05) in the overall population and when patients are stratified according to histology. However, concomitant carcinoma in situ represents an independent predictor of recurrence in the subgroup of patients with organ confined disease in case of urothelial bladder cancer and histological variants.

CONCLUSION

Concomitant carcinoma in situ should be considered a proxy of aggressiveness in bladder cancer after radical cystectomy. Based on its prognostic implications, concomitant carcinoma in situ should be considered for strict follow-up in patients with organ confined disease which may deserve adjuvant treatment both in pure urothelial bladder cancer and histological variants.

FGFR3 – a Central Player in Bladder Cancer Pathogenesis?

The identification of mutations in FGFR3 in bladder tumors in 1999 led to major interest in this receptor and during the subsequent 20 years much has been learnt about the mutational profiles found in bladder cancer, the phenotypes associated with these and the potential of this mutated protein as a target for therapy. Based on mutational and expression data, it is estimated that >80% of non-muscle-invasive bladder cancers (NMIBC) and ∼40% of muscle-invasive bladder cancers (MIBC) have upregulated FGFR3 signalling, and these frequencies are likely to be even higher if alternative splicing of the receptor, expression of ligands and changes in regulatory mechanisms are taken into account. Major efforts by the pharmaceutical industry have led to development of a range of agents targeting FGFR3 and other FGF receptors. Several of these have entered clinical trials, and some have presented very encouraging early results in advanced bladder cancer. Recent reviews have summarised the drugs and related clinical trials in this area. This review will summarise what is known about the effects of FGFR3 and its mutant forms in normal urothelium and bladder tumors, will suggest when and how this protein contributes to urothelial cancer pathogenesis and will highlight areas that may benefit from further study.

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.

Dataset for the reporting of urinary tract carcinoma-biopsy and transurethral resection specimen: recommendations from the International Collaboration on Cancer Reporting (ICCR)

The International Collaboration on Cancer Reporting (ICCR) is an alliance of major pathology organisations in Australasia, Canada, Europe, United Kingdom, and United States of America that develops internationally standardised, evidence-based datasets for the pathology reporting of cancer specimens. This dataset was developed by a multidisciplinary panel of international experts based on previously published ICCR guidelines for the production of cancer datasets. It is composed of Required (core) and Recommended (noncore) elements identified on the basis of literature review and expert consensus. The document also includes an explanatory commentary explaining the rationale behind the categorization of individual data items and provides guidance on how these should be collected and reported. The dataset includes nine required and six recommended elements for the reporting of cancers of the urinary tract in biopsy and transurethral resection (TUR) specimens. The required elements include specimen site, operative procedure, histological tumor type, subtype/variant of urothelial carcinoma, tumor grade, extent of invasion, status of muscularis propria, noninvasive carcinoma, and lymphovascular invasion (LVI). The recommended elements include clinical information, block identification key, extent of T1 disease, associated epithelial lesions, coexistent pathology, and ancillary studies. The dataset provides a structured template for globally harmonized collection of pathology data required for management of patients diagnosed with cancer of the urinary tract in biopsy and TUR specimens. It is expected that this will facilitate international collaboration, reduce duplication of effort in updating current national/institutional datasets, and be particularly useful for countries that have not developed their own datasets.

Systematic screening of protein-coding gene expression identified HMMR as a potential independent indicator of unfavorable survival in patients with papillary muscle-invasive bladder cancer

Papillary and non-papillary are two histological patterns of bladder carcinogenesis and are considered as dual-track oncogenic pathways, which have different genetic alterations. The TCGA-bladder cancer (BLCA) database contains clinicopathological, genomic and survival data from over 400 muscle-invasive bladder cancer patients. In this study, using data from this database, we performed a systematic screening of gene expression to identify the protein-coding gene that might have prognostic value in papillary and non-papillary muscle-invasive bladder cancer (MIBC). The data of patients with primary MIBC in TCGA-BLCA was acquired from the UCSC Xena project (http://xena.ucsc.edu) for re-analysis. By setting |log2 fold change|≥2 and adjusted p value <0.01 as the screening criteria, we found 751 significantly dysregulated genes, including 183 overexpressed and 568 downregulated genes. HMMR was identified as a potential prognostic marker with unique expression. Multivariate analysis showed that its expression was an independent prognostic indicator of shorter progression-free survival (PFS) (HR: 1.400, 95%CI: 1.021-1.920, p = 0.037) in the papillary subtype. ENST00000393915.8 and ENST00000358715.3, two transcripts that contain all 18 exons and encode the full length of HMMR, were significantly upregulated in cancer tissues compared with normal bladder tissues. None of the 17 CpG sites in its DNA locus was relevant to HMMR expression. 26/403 (6.5%) MIBC cases had HMMR gene-level amplification, which was associated with upregulated HMMR expression compared with the copy-neutral and deletion groups. Gene set enrichment analysis (GSEA) in papillary MIBC found that the high HMMR expression group was associated with upregulated genes enriched in multiple gene sets with well-established role in BC development, including G2M checkpoint, E2 F Targets, Myc Targets V1, Myc Targets V2 and Glycolysis. Based on these findings, we infer that HMMR expression might be a specific prognostic marker in terms of PFS in papillary MIBC. DNA amplification might be an important mechanism of its elevation.

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.

Nuclear expression of Y box binding-1 is important for resistance to chemotherapy including gemcitabine in TP53-mutated bladder cancer

The development and acquisition of multiple drug resistance in cancer cells remain a major obstacle in the treatment of bladder cancer. Nuclear translocation of Y box binding-1 (YB-1), which is a member of a family of DNA-binding proteins that contain a cold shock domain, plays a significant role in the acquisition of drug resistance by upregulating expression of the multidrug resistance-1 (MDR-1) gene product, p-glycoprotein. The tumor suppressor protein p53 is thought to be essential for nuclear translocation of YB-1. We hypothesized that nuclear translocation of YB-1 might be associated with drug resistance of bladder cancer with an abnormality of the TP53 gene that results in a mutated p53 protein. To test this hypothesis, we analyzed the association of YB-1 with drug resistance of TP53-mutated bladder cancer, including immunohistochemical analysis of YB-1, p-glycoprotein and p53 in vivo as well as the function of YB-1 nuclear translocation and regulation of its translocation by p53 in vitro. Additionally, we examined the association between the nuclear translocation of YB-1 and gemcitabine, a major anticancer-drug for bladder cancer, in cancer cell lines. Nuclear expression of YB-1 was correlated with the expression of p-glycoprotein and p53 in bladder cancer cases (p<0.05). In vitro, both introduction of TP53 and gemcitabine induced nuclear translocation of YB-1. These data indicate that YB-1 translocates to the nucleus coordinately with p53 expression and is involved in gemcitabine resistance in bladder cancer. Nuclear expression of YB-1 is important for resistance to chemotherapy including gemcitabine in TP53-mutated bladder cancer.

The presence of carcinoma in situ at radical cystectomy increases the risk of urothelial recurrence: Implications for follow-up schemes

INTRODUCTION

To evaluate the incidence of carcinoma in situ (CIS) in patients treated with radical cystectomy (RC) due to bladder cancer and to assess its effect on recurrence and survival rates.

METHODS

The study focused on 1,128 consecutive nonmetastatic patients with bladder cancer treated with RC at a single tertiary care referral center from 1994 to 2014. The Kaplan-Meier method was used to compare recurrence, cancer-specific mortality (CSM), and overall mortality-free rates in the overall population and in pT0-pT2 and pT3-pT4 patients after stratifying according to the presence of CIS. Multivariable (MVA) Cox regression analyses tested the effect of the presence of CIS on survival outcomes. MVA competing risk analyses were performed to assess the effect of CIS on urothelial recurrence.

RESULTS

The presence of CIS was reported in 277 (24.6%) patients. During a median follow-up of 6 years, 355 recurrences, 377 CSM, and 468 overall mortality were reported. At MVA Cox regression analyses, the presence of concomitant CIS was not associated with any survival effect when the overall population was considered (all P≥0.3). At MVA Cox regression analyses, there was no effect of CIS on survival outcomes in pT3-pT4 patients (all P>0.2); on the contrary, the presence of CIS was associated with worse CSM in pT0-pT2 patients only (hazard ratio [HR] = 1.82; CI: 1.01-3.29; P = 0.04). At MVA competing risk analyses predicting urothelial recurrence only, the presence of CIS was associated to an increased risk of urothelial recurrence in pT0-pT2 patients (HR = 2.99; CI: 1.05-8.53; P = 0.04), pT3-pT4 patients (HR = 10.29; CI: 1.40-75.75; P = 0.02), and in the overall population (HR = 4.47; CI: 1.81-11.07; P = 0.001).

CONCLUSION

An increased risk of developing urothelial recurrence only was recorded in patients diagnosed with CIS at RC. Physicians should consider this aspect ensuring a more severe follow-up schemes in patients who harbored this pathological feature.

[Preneoplastic lesions and precursors of urothelial cancer]

As even a mere thickening of the urothelium can harbor genetic changes identical to that of low grade papillary urothelial tumors, it is not always possible to clearly recognize a precursor lesion of urothelial carcinoma by routine histological diagnostics. Complementary immunohistochemical and molecular diagnostic methods assist the recognition of these entities. These methods especially help to identify clinically important genetically unstable cells as the hallmark of carcinoma in situ (CIS). Little is known about the clinical significance of the morphological subtypes of CIS, which range from large cell to micropapillary variants. For a better understanding of special types of bladder cancer (e.g. adenocarcinoma and squamous cell carcinoma), it seems to be important to define the phenotype and the molecular pattern of non-urothelial lesions, such as intestinal metaplasia and squamous metaplasia, better and more precisely.

Targeting mTOR and p53 Signaling Inhibits Muscle Invasive Bladder Cancer In Vivo

Urothelial tumors, accompanied by mutations of the tumor suppressor protein TP53 and dysregulation of mTOR signaling, are frequently associated with aggressive growth and invasiveness. We investigated whether targeting these two pathways would inhibit urothelial tumor growth and progression. Six-week-old transgenic UPII-SV40T male mice (n = 15/group) were fed control diet (AIN-76A) or experimental diets containing mTOR inhibitor (rapamycin, 8 or 16 ppm), p53 stabilizing agent [CP31398 (CP), 150 ppm], or a combination. Mice were euthanized at 40 weeks of age. Urinary bladders were collected and evaluated to determine tumor weight and histopathology. Each agent alone, and in combination, significantly inhibited tumor growth. Treatment with rapamycin alone decreased tumor weight up to 67% (P < 0.0001). Similarly, CP showed approximately 77% (P < 0.0001) suppression of tumor weight. The combination of low-dose rapamycin and CP led to approximately 83% (P < 0.0001) inhibition of tumor weight. There was no significant difference in tumor weights between rapamycin and CP treatments (P > 0.05). However, there was a significant difference between 8 ppm rapamycin and the combination treatment. Tumor invasion was also significantly inhibited in 53% (P < 0.005) and 66% (P < 0.0005) mice after 8 ppm and 16 ppm rapamycin, respectively. However, tumor invasion was suppressed in 73% (P < 0.0001) mice when CP was combined with 8 ppm rapamycin. These results suggest that targeting two or more pathways achieve better treatment efficacy than a single-agent high-dose strategy that could increase the risk of side effects. A combination of CP and rapamycin may be a promising method of inhibiting muscle-invasive urothelial transitional cell carcinoma.

Modelling bladder cancer in mice: opportunities and challenges

The prognosis and treatment of bladder cancer have improved little in the past 20 years. Bladder cancer remains a debilitating and often fatal disease, and is among the most costly cancers to treat. The generation of informative mouse models has the potential to improve our understanding of bladder cancer progression, as well as to affect its diagnosis and treatment. However, relatively few mouse models of bladder cancer have been described, and in particular, few that develop invasive cancer phenotypes. This Review focuses on opportunities for improving the landscape of mouse models of 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.

Molecular characteristics of urothelial neoplasms in children and young adults: a subset of tumors from young patients harbors chromosomal abnormalities but not FGFR3 or TP53 gene mutations

Urothelial neoplasms in children and young adult patients are rare and hypothesized to have a lower rate of recurrence and progression than those of older adults. Because of their rarity, data regarding molecular abnormalities in these tumors are limited. We studied molecular characteristics of urothelial neoplasms from patients under age 30 years using UroVysion fluorescence in situ hybridization (chromosomes 3, 7, 17, and 9p21) and DNA mutational analysis for the FGFR3 and TP53 genes. Seventeen tumors were identified in patients 6-26 years of age, including low-grade papillary urothelial carcinoma (n=10), high-grade papillary urothelial carcinoma (n=5), urothelial papilloma (n=1), and papillary urothelial neoplasm of low malignant potential (n=1). No tumor demonstrated mutation of FGFR3 or TP53. Chromosomal abnormalities were detected only in patients aged ≥19 years: two low-grade urothelial carcinomas had loss of 9p21 as a sole chromosomal abnormality and three high-grade urothelial carcinomas had other or multiple chromosomal abnormalities. Under age 19 years, no tumor showed molecular abnormalities with either method (five low-grade papillary urothelial carcinomas and one each of high-grade papillary urothelial carcinoma, papillary urothelial neoplasm of low malignant potential, and urothelial papilloma). Our results support the idea that mutations of the FGFR3 and TP53 genes are rare or absent in urothelial neoplasms of young patients. In contrast, chromosomal abnormalities detected by UroVysion fluorescence in situ hybridization are sometimes present in patients above 19-20 years of age. This finding supports the recently proposed hypothesis that an age of 19-20 years separates distinct molecular pathways of urothelial carcinogenesis.

Molecular subtyping of bladder cancer using Kohonen self-organizing maps

Kohonen self-organizing maps (SOMs) are unsupervised Artificial Neural Networks (ANNs) that are good for low-density data visualization. They easily deal with complex and nonlinear relationships between variables. We evaluated molecular events that characterize high- and low-grade BC pathways in the tumors from 104 patients. We compared the ability of statistical clustering with a SOM to stratify tumors according to the risk of progression to more advanced disease. In univariable analysis, tumor stage (log rank P = 0.006) and grade (P < 0.001), HPV DNA (P < 0.004), Chromosome 9 loss (P = 0.04) and the A148T polymorphism (rs 3731249) in CDKN2A (P = 0.02) were associated with progression. Multivariable analysis of these parameters identified that tumor grade (Cox regression, P = 0.001, OR.2.9 (95% CI 1.6–5.2)) and the presence of HPV DNA (P = 0.017, OR 3.8 (95% CI 1.3–11.4)) were the only independent predictors of progression. Unsupervised hierarchical clustering grouped the tumors into discreet branches but did not stratify according to progression free survival (log rank P = 0.39). These genetic variables were presented to SOM input neurons. SOMs are suitable for complex data integration, allow easy visualization of outcomes, and may stratify BC progression more robustly than hierarchical clustering.

PI3K/AKT pathway activation in bladder carcinogenesis

The PI3K/AKT pathway is considered to play a major role in bladder carcinogenesis, but its relationships with other molecular alterations observed in bladder cancer remain unknown. We investigated PI3K/AKT pathway activation in a series of human bladder urothelial carcinomas (UC) according to PTEN expression, PTEN deletions and FGFR3, PIK3CA, KRAS, HRAS, NRAS and TP53 gene mutations. The series included 6 normal bladder urothelial samples and 129 UC (Ta n = 25, T1 n = 34, T2-T3-T4 n = 70). Expression of phospho-AKT (pAKT), phospho-S6-Ribosomal Protein (pS6) (one downstream effector of PI3K/AKT pathway) and PTEN was evaluated by reverse phase protein Array. Expression of miR-21, miR-19a and miR-222, known to regulate PTEN expression, was also evaluated. pAKT expression levels were higher in tumors than in normal urothelium (p < 0.01), regardless of stage and showed a weak and positive correlation with pS6 (Spearman coefficient RS = 0.26; p = 0.002). No association was observed between pAKT or pS6 expression and the gene mutations studied. PTEN expression was decreased in PTEN-deleted tumors, and in T1 (p = 0.0089) and T2-T3-T4 (p < 0.001) tumors compared to Ta tumors; it was also negatively correlated with miR-19a (RS = -0.50; p = 0.0088) and miR-222 (RS = -0.48; p = 0.0132), but not miR-21 (RS = -0.27; p = 0.18) expression. pAKT and PTEN expressions were not negatively correlated, and, on the opposite, a positive and moderate correlation was observed in Ta (RS = 0.54; p = 0.0056) and T1 (RS = 0.56; p = 0.0006) tumors. Our study suggests that PI3K/AKT pathway activation occurs in the entire spectrum of bladder UC regardless of stage or known most frequent molecular alterations, and independently of low PTEN expression.

FGFR3 has tumor suppressor properties in cells with epithelial phenotype

Background

Due to frequent mutations in certain cancers, FGFR3 gene is considered as an oncogene. However, in some normal tissues, FGFR3 can limit cell growth and promote cell differentiation. Thus, FGFR3 action appears paradoxical.

Results

FGFR3 expression was forced in pancreatic cell lines. The receptor exerted dual effects: it suppressed tumor growth in pancreatic epithelial-like cells and had oncogenic properties in pancreatic mesenchymal-like cells. Distinct exclusive pathways were activated, STATs in epithelial-like cells and MAP Kinases in mesenchymal-like cells. Both FGFR3 splice variants had similar effects and used the same intracellular signaling. In human pancreatic carcinoma tissues, levels of FGFR3 dropped in tumors.

Conclusion

In tumors from epithelial origin, FGFR3 signal can limit tumor growth, explaining why the 4p16.3 locus bearing FGFR3 is frequently lost and why activating mutations of FGFR3 in benign or low grade tumors of epithelial origin are associated with good prognosis. The new hypothesis that FGFR3 can harbor both tumor suppressive and oncogenic properties is crucial in the context of targeted therapies involving specific tyrosine kinase inhibitors (TKIs). TKIs against FGFR3 might result in adverse effects if used in the wrong cell context.

Aneuploidy, oncogene amplification and epithelial to mesenchymal transition define spontaneous transformation of murine epithelial cells

Human epithelial cancers are defined by a recurrent distribution of specific chromosomal aneuploidies, a trait less typical for murine cancer models induced by an oncogenic stimulus. After prolonged culture, mouse epithelial cells spontaneously immortalize, transform and become tumorigenic. We assessed genome and transcriptome alterations in cultures derived from bladder and kidney utilizing spectral karyotyping, array CGH, FISH and gene expression profiling. The results show widespread aneuploidy, yet a recurrent and tissue-specific distribution of genomic imbalances, just as in human cancers. Losses of chromosome 4 and gains of chromosome 15 are common and occur early during the transformation process. Global gene expression profiling revealed early and significant transcriptional deregulation. Chromosomal aneuploidy resulted in expression changes of resident genes and consequently in a massive deregulation of the cellular transcriptome. Pathway interrogation of expression changes during the sequential steps of transformation revealed enrichment of genes associated with DNA repair, centrosome regulation, stem cell characteristics and aneuploidy. Genes that modulate the epithelial to mesenchymal transition and genes that define the chromosomal instability phenotype played a dominant role and were changed in a directionality consistent with loss of cell adhesion, invasiveness and proliferation. Comparison with gene expression changes during human bladder and kidney tumorigenesis revealed remarkable overlap with changes observed in the spontaneously transformed murine cultures. Therefore, our novel mouse models faithfully recapitulate the sequence of genomic and transcriptomic events that define human tumorigenesis, hence validating them for both basic and preclinical research.

[Update on FGFR3 mutation and multiple regional epigenetic silencing (MRES) phenotype in urothelial carcinogenesis]

FGFR3 mutation leads to a constitutive activation of the receptor 3 to Fibroblast Growth Factor. This mutation is early in urothelial carcinogenesis and is strongly associated to low grade papillary tumors. Multiple regional epigenetic silencing (MRES) phenotype corresponds to the transcriptional inactivation of chromosomal regions in muscle invasive bladder cancer, and is strongly associated to the molecular signature of carcinoma in situ. These alterations could be targeted by new specific therapies.

The bladder cancer genome; chromosomal changes as prognostic makers, opportunities, and obstacles

During the past decades, the complexity of the bladder cancer genome has become evident. Early cytogenetic studies identified several patterns of chromosomal changes, particularly the frequent loss of chromosome 9. The cytogenetic approach was replaced by molecular methods, such as comparative genome hybridization (CGH) and loss of heterozygosity (LOH) analyses that describe genomic changes at a molecular and higher resolution. With these methods, the full complexity of the bladder cancer genome has been better appreciated. Using CGH and LOH analyses, it also became apparent that premalignant lesions of the bladder, such as hyperplasia and dysplasia, as well as carcinoma in situ (CIS), showed genomic changes. Whole genome analyses showed that low stage, low grade tumors generally show fewer changes than tumors of higher stage and grade. In addition, several genomic alterations were shown to be highly specific for more aggressive and invasive tumors. Based on the general association between complex genomic changes and tumor behavior, several investigations have been directed towards the identification of prognostic genomic markers for urothelial cancer. A complicating factor in the analysis and understanding of bladder cancer genomic progression is that recurring and, hence, chronologically later tumors may show genomes less rearranged than preceding tumors. Furthermore, morphologically normal urothelium in patients with bladder cancer frequently show the same type of genomic alterations as the tumor proper. This makes an issue of to what extent information on genomic changes will produce reliable prognostic information when limited to the tumor proper.

Novel tumor subgroups of urothelial carcinoma of the bladder defined by integrated genomic analysis

PURPOSE

There is a need for improved subclassification of urothelial carcinoma (UC) at diagnosis. A major aim of this study was to search for novel genomic subgroups.

EXPERIMENTAL DESIGN

We assessed 160 tumors for genome-wide copy number alterations and mutation in genes implicated in UC. These comprised all tumor grades and stages and included 49 high-grade stage T1 (T1G3) tumors.

RESULTS

Our findings point to the existence of genomic subclasses of the "gold-standard" grade/stage groups. The T1G3 tumors separated into 3 major subgroups that differed with respect to the type and number of copy number events and to FGFR3 and TP53 mutation status. We also identified novel regions of copy number alteration, uncovered relationships between molecular events, and elucidated relationships between molecular events and clinico-pathologic features. FGFR3 mutant tumors were more chromosomally stable than their wild-type counterparts and a mutually exclusive relationship between FGFR3 mutation and overrepresentation of 8q was observed in non-muscle-invasive tumors. In muscle-invasive (MI) tumors, metastasis was positively associated with losses of regions on 10q (including PTEN), 16q and 22q, and gains on 10p, 11q, 12p, 19p, and 19q. Concomitant copy number alterations positively associated with TP53 mutation in MI tumors were losses on 16p, 2q, 4q, 11p, 10q, 13q, 14q, 16q, and 19p, and gains on 1p, 8q, 10q, and 12q. Significant complexity was revealed in events affecting chromosome 9.

CONCLUSIONS

These findings may lead to improved biologic understanding and the development of prognostic biomarkers. Novel regions of copy number alteration may reveal potential therapeutic targets.

The sensitivity of fluorescent-light cystoscopy for the detection of carcinoma in situ (CIS) of the bladder: a meta-analysis with comments on gold standard

What's known on the subject? and What does the study add? Fluorescent-light cystoscopy has a high sensitivity, relative to that of white light cystoscopy, for carcinoma in situ of the bladder. However, this systematic review reveals that the absolute sensitivity is unknown due to the absence of proper gold standard which is microscopic examination of whole bladders. •  A literature search was conducted to identify peer-reviewed study reports on the sensitivity of fluorescent-light cystoscopy (FLC) for the detection of carcinoma in situ (CIS) of the bladder. •  Data from 16 original studies comprising 1503 patients were pooled. •  The claimed sensitivity of FLC for detecting patients with CIS using the most commonly reported intravesical agents 5-aminolevulinic acid or hexaminolevulinic acid was 92.4%, while that of white-light cystoscopy (WLC) was 60.5%. The two agents did not differ significantly for sensitivity. •  It must be pointed out that a 'gold standard' is lacking in FLC studies. •  The occurrence of CIS of the bladder can only be established by the pathological examination of whole bladders. The true sensitivities of various modes of cystoscopy for detecting CIS can be revealed if patients scheduled for cystectomy are first examined with WLC, FLC, and optionally random biopsies. •  The absolute sensitivity of FLC for detecting CIS of the bladder is not yet known.

A novel epigenetic phenotype associated with the most aggressive pathway of bladder tumor progression

Background

Epigenetic silencing can extend to whole chromosomal regions in cancer. There have been few genome-wide studies exploring its involvement in tumorigenesis.

Methods

We searched for chromosomal regions affected by epigenetic silencing in cancer by using Affymetrix microarrays and real-time quantitative polymerase chain reaction to analyze RNA from 57 bladder tumors compared with normal urothelium. Epigenetic silencing was verified by gene re-expression following treatment of bladder cell lines with 5-aza-deoxycytidine, a DNA demethylating agent, and trichostatin A, a histone deacetylase inhibitor. DNA methylation was studied by bisulfite sequencing and histone methylation and acetylation by chromatin immunoprecipitation. Clustering was used to distinguish tumors with multiple regional epigenetic silencing (MRES) from those without and to analyze the association of this phenotype with histopathologic and molecular types of bladder cancer. The results were confirmed with a second panel of 40 tumor samples and extended in vitro with seven bladder cancer cell lines. All statistical tests were two-sided.

Results

We identified seven chromosomal regions of contiguous genes that were silenced by an epigenetic mechanism. Epigenetic silencing was not associated with DNA methylation but was associated with histone H3K9 and H3K27 methylation and histone H3K9 hypoacetylation. All seven regions were concordantly silenced in a subgroup of 26 tumors, defining an MRES phenotype. MRES tumors exhibited a carcinoma in situ–associated gene expression signature (25 of 26 MRES tumors vs 0 of 31 non-MRES tumors, P < 10⁻¹⁴), rarely carried FGFR3 mutations (one of 26 vs 22 of 31 non-MRES tumors, P < 10⁻⁶), and contained 25 of 33 (76%) of the muscle-invasive tumors. Cell lines derived from aggressive bladder tumors presented epigenetic silencing of the same regions.

Conclusions

We have identified an MRES phenotype characterized by the concomitant epigenetic silencing of several chromosomal regions, which, in bladder cancer, is specifically associated with the carcinoma in situ gene expression signature.

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.

Cyclin D3 gene amplification in bladder carcinoma in situ

Carcinoma in situ (CIS) is a non-papillary high-grade, potentially aggressive, and unpredictable manifestation of bladder urothelial carcinoma. The aim of this study was to assess patterns of Cyclin D3 gene amplification in Bacillus Calmette-Guerin (BCG)-treated CIS and correlate gene status with recurrence-free and progression-free survival. A sequential cohort series of 28 primary (isolated) or secondary (concomitant) bladder CIS samples in which there was enough tissue material to assess Cyclin D3 gene status by fluorescent in situ hybridization was the study group. Cyclin D3 gene amplification was present in 29% of secondary CIS; none of primary CIS samples had Cyclin D3 gene amplification. Cyclin D3 amplification was related to recurrence- (p = 0.046) and progression-free survival (p = 0.002). Type of bladder CIS (primary vs. secondary) was unrelated to recurrence- or progression-free survival in the current series. Cox's regression analysis selected Cyclin D3 as an independent predictor of progression-free survival (p = 0.041, relative risk = 61.503, 95% confidence interval = 1.1-274.710). None of primary CIS cases recurred on follow-up; nine secondary CIS recurred and four of them progressed to invasive bladder carcinoma HG T1 (n = 1), T2b N0M0 (n = 1), T3b N1M0 (n = 1) and T4aN1M1 (n = 1). Mean recurrence ± SD (months) occurred at 19.5 ± 2.06 (95% (confidence interval (CI)), 15.5-23.6); mean progression (months) occurred at 23.8 ± 1.46 (95% (CI), 20.9-26.7). Our study suggests that Cyclin D3 gene amplification might be a predictor of aggressiveness in BCG-treated CIS.

Clinical outcome of primary versus secondary bladder carcinoma in situ

PURPOSE

Differences in clinical outcome are still unclear between primary and secondary bladder carcinoma in situ. We compared the clinical outcomes of primary and secondary carcinoma in situ, and identified predictive factors.

MATERIALS AND METHODS

We retrospectively analyzed the records of 476 patients with high grade cTis, including 221 with primary and 255 with secondary carcinoma in situ, from 1990 to 2008 at a high volume cancer center after transurethral resection and intravesical bacillus Calmette-Guerin therapy. End points were time to progression to invasive disease (cT1 or higher) or radical cystectomy before progression, and progression to muscle invasive disease (cT2 or higher) or radical cystectomy before progression. We used Cox proportional hazards regression models.

RESULTS

Patients with primary carcinoma in situ responded significantly more within 6 months of bacillus Calmette-Guerin than those with secondary carcinoma in situ (65% vs 39%, p <0.001). In the primary vs secondary groups the 5-year cumulative incidence of progression to cT1 or higher was 43% (95% CI 36-51) vs 32% (95% CI 27-39) and for progression to cT2 or higher it was 17% (95% CI 12-23) vs 8% (95% CI 5-13). On multivariate analysis primary carcinoma in situ was significantly more likely to progress to cT1 or higher (HR 1.38, 95% CI 1.05-1.81, p = 0.020) and to cT2 or higher, or radical cystectomy (HR 1.72, 95% CI 1.27-2.33, p = 0.001). We found no significance for age, gender or response to bacillus Calmette-Guerin as outcome predictors. Median followup was 5.1 years.

CONCLUSIONS

Patients presenting with primary carcinoma in situ have a worse outcome than those with secondary carcinoma in situ, suggesting a need to differentiate these 2 entities in the treatment decision process.

Urothelial carcinoma: stem cells on the edge

Tumors are heterogeneous collections of cells with highly variable abilities to survive, grow, and metastasize. This variability likely stems from epigenetic and genetic influences, either stochastic or hardwired by cell type-specific lineage programs. That differentiation underlies tumor cell heterogeneity was elegantly demonstrated in hematopoietic tumors, in which rare primitive cells (cancer stem cells (CSCs)) resembling normal hematopoietic stem cells are ultimately responsible for tumor growth and viability. Because of the compelling clinical implications CSCs pose--across the entire spectrum of cancers--investigators applied the CSC model to cancers arising in tissues with crudely understood differentiation programs. Instead of relying on differentiation, these studies used empirically selected markers and statistical arguments to identify CSCs. The empirical approach has stimulated important questions about "stemness" in cancer cells as well as the validity and stoichiometry of CSC assays. The recent identification of urothelial differentiation programs in urothelial carcinomas (UroCas) supports the idea that solid epithelial cancers (carcinomas) develop and differentiate analogously to normal epithelia and provides new insights about the spatial localization and molecular makeup of carcinoma CSCs. Importantly, CSCs from invasive UroCas (UroCSCs) appear well situated to exchange important signals with adjacent stroma, to escape immune surveillance, and to survive cytotoxic therapy. These signals have potential roles in treatment resistance and many participate in druggable cellular pathways. In this review, we discuss the implications of these findings in understanding CSCs and in better understanding how UroCas form, progress, and should be treated.

Molecular genesis of non-muscle-invasive urothelial carcinoma (NMIUC)

Urothelial carcinoma (UC) is the most common type of bladder cancer in Western nations. Most patients present with the non-muscle-invasive (NMIUC) form of the disease, while up to a third harbour the invasive form (MIUC). Specifically, the aetiology of NMIUC appears to be multifactorial and very different from that of MIUC. Loss of specific tumour suppressor genes as well as gain-of-function mutations in proteins within defined cellular signalling pathways have been implicated in NMIUC aetiology. The regions of chromosome 9 that harbour CDKN2A, CDKN2B, TSC1, PTCH1 and DBC1 are frequently mutated in NMIUC, resulting in functional loss; in addition, HRAS and FGFR3, which are both proto-oncogenes encoding components of the Ras-MAPK signalling pathway, have been found to harbour activating mutations in a large number of NMIUCs. Interestingly, some of these molecular events are mutually exclusive, suggesting functional equivalence. Since several of these driving changes are amenable to therapeutic targeting, understanding the signalling events in NMIUC may offer novel approaches to manage the recurrence and progression of this disease.

Diagnosis, evaluation and treatment of carcinoma in situ of the urinary bladder: the state of the art

Urothelial carcinoma in situ (CIS) is regarded as a precursor of invasive bladder carcinoma. Although relatively uncommon as a primary entity, CIS is frequently seen in conjunction with other bladder tumors and represents a significant source of difficulty for surveillance of patients with known bladder cancer. CIS lesions are difficult to detect by cystoscopic examination or by currently available screening markers. Urothelial CIS is infrequently reported in the literature as a primary process; however, a wide variety of emerging methodologies are becoming available for screening and follow-up of bladder cancer. Most new methods demonstrate sensitivity and specificity similar to the current standard of urine cytology and cystoscopy. Detection of high-grade lesions such as CIS by these methods appears generally better than detection of low-grade lesions. Current molecular evidence suggests that a spectrum of genetic aberrations including p53 mutations are strongly associated with the potentially invasive CIS phenotype in contrast to low-grade papillary and hyperplastic lesions. These low-grade lesions frequently recur but infrequently become invasive. Patients with high-grade lesions including CIS and high-grade papillary tumors warrant aggressive treatment and life-long surveillance.