Biology of urothelial tumorigenesis: insights from genetically engineered mice

The Origin and Evolution of Bladder Cancer Stem Cells

Bladder cancer is the most common malignant tumor of the urinary system. Bladder cancer stem cells (BCSCs) play key roles in tumor initiation, metastasis, relapse and drug-resistance. Investigation of BCSCs is of great value. On the basis of a review of normal bladder stem cells and universal cancer stem cells (CSCs), we summarize the origin of BCSCs, isolation and identification of CSCs from bladder cancer, signaling pathway of BCSCs, BCSCs targeted therapy, and relationship of BCSCs with non-muscle invasiveness and muscle invasiveness. This review aims to provide better elucidation about BCSCs, and provide constructive data for classification, prognosis, treatment and early intervention of bladder cancer.

Development, regeneration and tumorigenesis of the urothelium

The urothelium of the bladder functions as a waterproof barrier between tissue and outflowing urine. Largely quiescent during homeostasis, this unique epithelium rapidly regenerates in response to bacterial or chemical injury. The specification of the proper cell types during development and injury repair is crucial for tissue function. This Review surveys the current understanding of urothelial progenitor populations in the contexts of organogenesis, regeneration and tumorigenesis. Furthermore, we discuss pathways and signaling mechanisms involved in urothelial differentiation, and consider the relevance of this knowledge to stem cell biology and tissue regeneration.

PKM2 Is Essential for Bladder Cancer Growth and Maintenance

Pyruvate kinase M2 (PKM2) has been shown to promote tumorigenesis by facilitating the Warburg effect and enhancing the activities of oncoproteins. However, this paradigm has recently been challenged by studies in which the absence of PKM2 failed to inhibit and instead accelerated tumorigenesis in mouse models. These results seem inconsistent with the fact that most human tumors overexpress PKM2. To further elucidate the role of PKM2 in tumorigenesis, we investigated the effect of PKM2 knockout in oncogenic HRAS-driven urothelial carcinoma. While PKM2 ablation in mouse urothelial cells did not affect tumor initiation, it impaired the growth and maintenance of HRAS-driven tumors. Chemical inhibition of PKM2 recapitulated these effects. Both conditions substantially reduced complex formation of PKM2 with STAT3, their nuclear translocation, and HIF1α- and VEGF-related angiogenesis. The reduction in nuclear STAT3 in the absence of PKM2 also correlated with decreased autophagy and increased apoptosis. Time-controlled, inducible PKM2 overexpression in simple urothelial hyperplasia did not trigger tumorigenesis, while overexpression of PKM2, but not PKM1, in nodular urothelial hyperplasia with angiogenesis strongly accelerated tumorigenesis. Finally, in human patients, PKM2 was overexpressed in low-grade nonmuscle-invasive and high-grade muscle-invasive bladder cancer. Based on these data, PKM2 is not required for tumor initiation but is essential for tumor growth and maintenance by enhancing angiogenesis and metabolic addiction. The PKM2-STAT3-HIF1α/VEGF signaling axis may play a critical role in bladder cancer and may serve as an actionable therapeutic target.

SIGNIFICANCE

Genetic manipulation and pharmacologic inhibition of PKM2 in mouse urothelial lesions highlight its essential role in promoting angiogenesis and metabolic addiction, events indispensable for tumor growth and maintenance.

Dominant role of CDKN2B/p15INK4B of 9p21.3 tumor suppressor hub in inhibition of cell-cycle and glycolysis

Human chromosome 9p21.3 is susceptible to inactivation in cell immortalization and diseases, such as cancer, coronary artery disease and type-2 diabetes. Although this locus encodes three cyclin-dependent kinase (CDK) inhibitors (p15^INK4B, p14^ARF and p16^INK4A), our understanding of their functions and modes of action is limited to the latter two. Here, we show that in vitro p15^INK4B is markedly stronger than p16^INK4A in inhibiting pRb1 phosphorylation, E2F activity and cell-cycle progression. In mice, urothelial cells expressing oncogenic HRas and lacking p15^INK4B, but not those expressing HRas and lacking p16^INK4A, develop early-onset bladder tumors. The potency of CDKN2B/p15^INK4B in tumor suppression relies on its strong binding via key N-terminal residues to and inhibition of CDK4/CDK6. p15^INK4B also binds and inhibits enolase-1, a glycolytic enzyme upregulated in most cancer types. Our results highlight the dual inhibition of p15^INK4B on cell proliferation, and unveil mechanisms whereby p15^INK4B aberrations may underpin cancer and non-cancer conditions.

The human chromosome locus 9p21.3 is a tumour suppressor hub which encodes three CDK inhibitors, p15INK4B, p14ARF and p16INK4A. Here, the authors show that p15INK4B inhibits the cell cycle and glycolysis in a murine model of HRas + ‐mediated urothelial carcinoma and has a more relevant role as a tumour suppressor than its neighbouring p16INK4A.

The therapeutic and prognostic implications of molecular biomarkers in urothelial carcinoma

Urothelial cell carcinoma (UCC) of the bladder and upper urinary tract is a heterogeneous disease with distinct biologic features resulting in different clinical behaviors. Bladder cancer (BC) is classified into non-muscle invasive BC (NMIBC) and muscle invasive BC (MIBC). NMIBC is associated with high recurrence rates and risk of progression to invasive disease, whereas MIBC is complicated by systemic recurrence after radical cystectomy because of the limited efficacy of available therapies. UCC of the upper urinary tract (UUT-UCC) is a rare but aggressive urologic cancer characterized by multifocality, local recurrence, and metastasis. Conventional histopathologic evaluation of UCC, including tumor stage and grade, cannot accurately predict the behavior of BC and UUT-UCC. Recent clinical and preclinical studies aimed at understanding the molecular landscape of UCC have provided insight into molecular subtyping, inter- or intratumoral heterogeneity, and potential therapeutic targets. Combined analysis of molecular markers and standard pathological features may improve risk stratification and help monitor tumor progression and treatment response, ultimately improving patient outcomes. This review discusses prognostic and therapeutic biomarkers for BC and UUT-UCC, and describes recent advances in molecular stratification that may guide prognosis, patient stratification, and treatment selection.

Carcinogen-induced bladder cancer in the FVB mouse strain is associated with glandular differentiation and increased Cd274/Pdl-1 expression

BACKGROUND

Creation of genetically engineered mouse models of bladder cancer often involves the use of several background strains in conjunction with the carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). However, carcinogen susceptibility in commonly used strains, as well as phenotypic differences is not well characterized.

OBJECTIVES

To determine differences in susceptibility and phenotypic outcome following BBN exposure of C57BL/6 and FVB, two strains commonly used for model development.

METHODS

Male C57BL/6 and FVB mice were exposed to BBN (0.05%) in drinking water for 12 and 16 weeks. Dissected bladders were characterized by histological and immunohistochemical analyses. Gene Ontology analysis was performed to identify differences in gene expression across strains following BBN exposure.

RESULTS

While the C57BL/6 strain developed non-invasive tumors, FVB mice developed muscle invasive bladder cancer with squamous and/or glandular differentiation. Glandular differentiation was exclusively observed in the FVB strain. FVB tumors were highly immunogenic and inflamed by the presence of high expression of Cd274 (Pdl-1), murine histocompatibility complex (H2) and pro-inflammatory cytokines (Il-5 and Il-17).

CONCLUSIONS

Following BBN exposure, FVB mice undergo rapid tumorigenesis and disease progression characterized by Pdl-1 expression and development of glandular differentiation. These studies identify a degree of tumor heterogeneity in the FVB tumors previously undescribed, and identify FVB mice as a potentially useful model for the study of bladder adenocarcinoma and the inflammatory tumor microenvironment.

Mouse and human urothelial cancer organoids: A tool for bladder cancer research

Bladder cancer is a common malignancy that has a relatively poor outcome. Lack of culture models for the bladder epithelium (urothelium) hampers the development of new therapeutics. Here we present a long-term culture system of the normal mouse urothelium and an efficient culture system of human bladder cancer cells. These so-called bladder (cancer) organoids consist of 3D structures of epithelial cells that recapitulate many aspects of the urothelium. Mouse bladder organoids can be cultured efficiently and genetically manipulated with ease, which was exemplified by creating genetic knockouts in the tumor suppressors Trp53 and Stag2. Human bladder cancer organoids can be derived efficiently from both resected tumors and biopsies and cultured and passaged for prolonged periods. We used this feature of human bladder organoids to create a living biobank consisting of bladder cancer organoids derived from 53 patients. Resulting organoids were characterized histologically and functionally. Organoid lines contained both basal and luminal bladder cancer subtypes based on immunohistochemistry and gene expression analysis. Common bladder cancer mutations like TP53 and FGFR3 were found in organoids in the biobank. Finally, we performed limited drug testing on organoids in the bladder cancer biobank.

Uroplakins play conserved roles in egg fertilization and acquired additional urothelial functions during mammalian divergence

Uroplakin (UP) tetraspanins and their associated proteins are major mammalian urothelial differentiation products that form unique two-dimensional crystals of 16-nm particles (“urothelial plaques”) covering the apical urothelial surface. Although uroplakins are highly expressed only in mammalian urothelium and are often referred to as being urothelium specific, they are also expressed in several mouse nonurothelial cell types in stomach, kidney, prostate, epididymis, testis/sperms, and ovary/oocytes. In oocytes, uroplakins colocalize with CD9 on cell-surface and multivesicular body-derived exosomes, and the cytoplasmic tail of UPIIIa undergoes a conserved fertilization-dependent, Fyn-mediated tyrosine phosphorylation that also occurs in Xenopus laevis eggs. Uroplakin knockout and antibody blocking reduce mouse eggs’ fertilization rate in in vitro fertilization assays, and UPII/IIIa double-knockout mice have a smaller litter size. Phylogenetic analyses showed that uroplakin sequences underwent significant mammal-specific changes. These results suggest that, by mediating signal transduction and modulating membrane stability that do not require two-dimensional-crystal formation, uroplakins can perform conserved and more ancestral fertilization functions in mouse and frog eggs. Uroplakins acquired the ability to form two-dimensional-crystalline plaques during mammalian divergence, enabling them to perform additional functions, including umbrella cell enlargement and the formation of permeability and mechanical barriers, to protect/modify the apical surface of the modern-day mammalian urothelium.

Cruciferous Vegetables, Isothiocyanates, and Bladder Cancer Prevention

Bladder cancer is a significant health burden due to its high prevalence, risk of mortality, morbidity, and high cost of medical care. Epidemiologic evidence suggests that diets rich in cruciferous vegetables, particularly broccoli, are associated with lower bladder cancer risk. Phytochemicals in cruciferous vegetables, such as glucosinolates, which are enzymatically hydrolyzed to bioactive isothiocyanates, are possible mediators of an anticancer effect. In vitro studies have shown inhibition of bladder cancer cell lines, cell cycle arrest, and induction of apoptosis by these isothiocyanates, in particular sulforaphane and erucin. Although not yet completely understood, many mechanisms of anticancer activity at the steps of cancer initiation, promotion, and progression have been attributed to these isothiocyanates. They target multiple pathways including the adaptive stress response, phase I/II enzyme modulation, pro-growth, pro-survival, pro-inflammatory signaling, angiogenesis, and even epigenetic modulation. Multiple in vivo studies have shown the bioavailability of isothiocyanates and their antitumoral effects. Although human studies are limited, they support oral bioavailability with reasonable plasma and urine concentrations achieved. Overall, both cell and animal studies support a potential role for isothiocyanates in bladder cancer prevention and treatment. Future studies are necessary to examine clinically relevant outcomes and define guidelines on ameliorating the bladder cancer burden.

A patient-derived orthotopic xenograft model enabling human high-grade urothelial cell carcinoma of the bladder tumor implantation, growth, angiogenesis, and metastasis

High-grade urothelial cell carcinoma of the bladder has a poor prognosis when lymph nodes are involved. Despite curative therapy for clinically-localized disease, over half of the muscle-invasive urothelial cell carcinoma patients will develop metastases and die within 5 years. There are currently no described xenograft models that consistently mimic urothelial cell carcinoma metastasis. To develop a patient-derived orthotopic xenograft model to mimic clinical urothelial cell carcinoma progression to metastatic disease, the urothelial cell carcinoma cell line UM-UC-3 and two urothelial cell carcinoma patient specimens were doubly tagged with Luciferase/RFP and were intra-vesically (IB) instilled into NOD/SCID mice with or without lymph node stromal cells (HK cells). Mice were monitored weekly with bioluminescence imaging to assess tumor growth and metastasis. Primary tumors and organs were harvested for bioluminescence imaging, weight, and formalin-fixed for hematoxylin and eosin and immunohistochemistry staining. In this patient-derived orthotopic xenograft model, xenograft tumors showed better implantation rates than currently reported using other models. Xenograft tumors histologically resembled pre-implanted primary specimens from patients, presenting muscle-invasive growth patterns. In the presence of HK cells, tumor formation, tumor angiogenesis, and distant organ metastasis were significantly enhanced in both UM-UC-3 cells and patient-derived specimens. Thus, we established a unique, reproducible patient-derived orthotopic xenograft model using human high-grade urothelial cell carcinoma cells and lymph node stromal cells. It allows for investigating the mechanism involved in tumor formation and metastasis, and therefore it is useful for future testing the optimal sequence of conventional drugs or the efficacy of novel therapeutic drugs.

Orthotopic Mouse Models of Urothelial Cancer

Orthotopic mouse models of urothelial cancer are essential for testing novel therapies and molecular manipulations of cell lines in vivo. These models are either established by orthotopic inoculation of human (xenograft models) or murine tumor cells (syngeneic models) in immunocompromised or immune competent mice. Current techniques rely on inoculation by intravesical instillation or direct injection into the bladder wall. Alternative models include the induction of murine bladder tumors by chemical carcinogens (BBN) or genetic engineering (GEM).

Adjuvant treatment following radical cystectomy for muscle-invasive urothelial carcinoma and variant histologies: Is there a role for radiotherapy?

Comprehensive molecular characterisation of muscle-invasive urothelial carcinoma and variant histological subtypes has led to the identification of recurrent driver mutations that are distinct in these aggressive subgroups of bladder cancer. While distant metastasis dominates as a pattern of relapse following radical cystectomy or chemoradiotherapy, loco-regional control rates are also suboptimal with single modality local treatment, and likewise, harbour equivocal implications on the long-term prognosis of patients. The role of adjuvant radiotherapy for optimising disease control within the pelvis is controversial, with limited evidence to support its efficacy. Herein, we present a stepwise review on adjuvant radiotherapy post-cystectomy; first, discussing the evidence to date supporting the concept that adjuvant radiotherapy is effective in targeting occult metastases within the pelvis, and adds to the benefits of adjuvant chemotherapy. Next, we outlined the principles underlying the definition of radiotherapy target volumes. To conclude, we addressed the need for appropriate patient stratification for treatment intensification, based on existing clinical models and novel molecular indices of aggression in muscle-invasive urothelial cancers and variant histological subtypes.

Proceedings of the 3rd Annual Albert Institute for Bladder Cancer Research Symposium

The Third Annual Albert Institute Bladder Symposium was held on September 8–10th, 2016, in Denver Colorado. Participants discussed several critical topics in the field of bladder cancer: 1) Best practices for tissue analysis and use to optimize correlative studies, 2) Modeling bladder cancer to facilitate understanding and innovation, 3) Targeted therapies for bladder cancer, 4) Tumor phylogeny in bladder cancer, 5) New Innovations in bladder cancer diagnostics. Our understanding of and approach to treating urothelial carcinoma is undergoing rapid advancement. Preclinical models of bladder cancer have been leveraged to increase our basic and mechanistic understanding of the disease. With the approval of immune checkpoint inhibitors for the treatment of advanced urothelial carcinoma, the treatment approach for these patients has quickly changed. In this light, molecularly-defined subtypes of bladder cancer and appropriate pre-clinical models are now essential to the further advancement and appropriate application of these therapeutic improvements. The optimal collection and processing of clinical urothelial carcinoma tissues samples will also be critical in the development of predictive biomarkers for therapeutic selection. Technological advances in other areas including optimal imaging technologies and micro/nanotechnologies are being applied to bladder cancer, especially in the localized setting, and hold the potential for translational impact in the treatment of bladder cancer patients. Taken together, advances in several basic science and clinical areas are now converging in bladder cancer. These developments hold the promise of shaping and improving the clinical care of those with the disease.

Toward the integration of Omics data in epidemiological studies: still a "long and winding road"

Primary and secondary prevention can highly benefit a personalized medicine approach through the accurate discrimination of individuals at high risk of developing a specific disease from those at moderate and low risk. To this end precise risk prediction models need to be built. This endeavor requires a precise characterization of the individual exposome, genome, and phenome. Massive molecular omics data representing the different layers of the biological processes of the host and the nonhost will enable to build more accurate risk prediction models. Epidemiologists aim to integrate omics data along with important information coming from other sources (questionnaires, candidate markers) that has been proved to be relevant in the discrimination risk assessment of complex diseases. However, the integrative models in large-scale epidemiologic research are still in their infancy and they face numerous challenges, some of them at the analytical stage. So far, there are a small number of studies that have integrated more than two omics data sets, and the inclusion of non-omics data in the same models is still missing in most of studies. In this contribution, we aim at approaching the omics and non-omics data integration from the epidemiology scope by considering the "massive" inclusion of variables in the risk assessment and predictive models. We also provide already available examples of integrative contributions in the field, propose analytical strategies that allow considering both omics and non-omics data in the models, and finally review the challenges imbedding this type of research.

Metabolic Pathway Signatures Associated with Urinary Metabolite Biomarkers Differentiate Bladder Cancer Patients from Healthy Controls

PURPOSE

Our previous high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry study identified bladder cancer (BCA)-specific urine metabolites, including carnitine, acylcarnitines, and melatonin. The objective of the current study was to determine which metabolic pathways are perturbed in BCA, based on our previously identified urinary metabolome.

MATERIALS AND METHODS

A total of 135 primary BCA samples and 26 control tissue samples from healthy volunteers were analyzed. The association between specific urinary metabolites and their related encoding genes was analyzed.

RESULTS

Significant alterations in the carnitine-acylcarnitine and tryptophan metabolic pathways were detected in urine specimens from BCA patients compared to those of healthy controls. The expression of eight genes involved in the carnitine-acylcarnitine metabolic pathway (CPT1A, CPT1B, CPT1C, CPT2, SLC25A20, and CRAT) or tryptophan metabolism (TPH1 and IDO1) was assessed by RT-PCR in our BCA cohort (n=135). CPT1B, CPT1C, SLC25A20, CRAT, TPH1, and IOD1 were significantly downregulated in tumor tissues compared to normal bladder tissues (p<0.05 all) of patients with non-muscle invasive BCA, whereas CPT1B, CPT1C, CRAT, and TPH1 were downregulated in those with muscle invasive BCA (p<0.05), with no changes in IDO1 expression.

CONCLUSION

Alterations in the expression of genes associated with the carnitine-acylcarnitine and tryptophan metabolic pathways, which were the most perturbed pathways in BCA, were determined.

Role of isoenzyme M2 of pyruvate kinase in urothelial tumorigenesis

The conversion of precancerous lesions to full-fledged cancers requires the affected cells to surpass certain rate-limiting steps. We recently showed that activation of HRAS proto-oncogene in urothelial cells of transgenic mice causes simple urothelial hyperplasia (SUH) which is persistent and whose transition to low-grade papillary urothelial carcinoma (UC) must undergo nodular urothelial hyperplasia (NUH). We hypothesized that NUH, which has acquired fibrovascular cores, plays critical roles in mesenchymal-to-epithelial signaling, breaching the barriers of urothelial tumor initiation. Using proteomics involving two-dimensional gel electrophoresis, immunoblotting with pan-phosphotyrosine antibody and MALDI-mass spectrometry, we identified isoform 2 of pyruvate kinase (PKM2) as the major tyrosine-phosphorylated protein switched on during NUH. We extended this finding using specimens from transgenic mice, human UC and UC cell lines, establishing that PKM2, but not its spliced variant PKM1, was over-expressed in low-grade and, more prominently, high-grade UC. In muscle-invasive UC, PKM2 was co-localized with cytokeratins 5 and 14, UC progenitor markers. Specific inhibition of PKM2 by siRNA or shRNA suppressed UC cell proliferation via increased apoptosis, autophagy and unfolded protein response. These results strongly suggest that PKM2 plays an important role in the genesis of low-grade non-invasive and high-grade invasive urothelial carcinomas.

The cAMP responsive element binding protein 1 transactivates epithelial membrane protein 2, a potential tumor suppressor in the urinary bladder urothelial carcinoma

In this study, we report that EMP2 plays a tumor suppressor role by inducing G₂/M cell cycle arrest, suppressing cell viability, proliferation, colony formation/anchorage-independent cell growth via regulation of G₂/M checkpoints in distinct urinary bladder urothelial carcinoma (UBUC)-derived cell lines. Genistein treatment or exogenous expression of the cAMP responsive element binding protein 1 (CREB1) gene in different UBUC-derived cell lines induced EMP2 transcription and subsequent translation. Mutagenesis on either or both cAMP-responsive element(s) dramatically decreased the EMP2 promoter activity with, without genistein treatment or exogenous CREB1 expression, respectively. Significantly correlation between the EMP2 immunointensity and primary tumor, nodal status, histological grade, vascular invasion and mitotic activity was identified. Multivariate analysis further demonstrated that low EMP2 immunoexpression is an independent prognostic factor for poor disease-specific survival. Genistein treatments, knockdown of EMP2 gene and double knockdown of CREB1 and EMP2 genes significantly inhibited tumor growth and notably downregulated CREB1 and EMP2 protein levels in the mice xenograft models. Therefore, genistein induced CREB1 transcription, translation and upregulated pCREB1(S133) protein level. Afterward, pCREB1(S133) transactivated the tumor suppressor gene, EMP2, in vitro and in vivo. Our study identified a novel transcriptional target, which plays a tumor suppressor role, of CREB1.

Inhibition of cholesterol metabolism underlies synergy between mTOR pathway inhibition and chloroquine in bladder cancer cells

Mutations to fibroblast growth factor receptor 3 (FGFR3) and phosphatase and tensin homologue (PTEN) signalling pathway components (for example, PTEN loss, PIK3CA, AKT1, TSC1/2) are common in bladder cancer, yet small-molecule inhibitors of these nodes (FGFR/PTENi) show only modest activity in preclinical models. As activation of autophagy is proposed to promote survival under FGFR/PTENi, we have investigated this relationship in a panel of 18 genetically diverse bladder cell lines. We found that autophagy inhibition does not sensitise bladder cell lines to FGFR/PTENi, but newly identify an autophagy-independent cell death synergy in FGFR3-mutant cell lines between mTOR (mammalian target of rapamycin) pathway inhibitors and chloroquine (CQ)—an anti-malarial drug used as a cancer therapy adjuvant in over 30 clinical trials. The mechanism of synergy is consistent with lysosomal cell death (LCD), including cathepsin-driven caspase activation, and correlates with suppression of cSREBP1 and cholesterol biosynthesis in sensitive cell lines. Remarkably, loss of viability can be rescued by saturating cellular membranes with cholesterol or recapitulated by statin-mediated inhibition, or small interfering RNA knockdown, of enzymes regulating cholesterol metabolism. Modulation of CQ-induced cell death by atorvastatin and cholesterol is reproduced across numerous cell lines, confirming a novel and fundamental role for cholesterol biosynthesis in regulating LCD. Thus, we have catalogued the molecular events underlying cell death induced by CQ in combination with an anticancer therapeutic. Moreover, by revealing a hitherto unknown aspect of lysosomal biology under stress, we propose that suppression of cholesterol metabolism in cancer cells should elicit synergy with CQ and define a novel approach to future cancer treatments.

Primary Sarcomatoid Tumor of the Bladder: A Different Entity but the Same Approach?

Bladder cancer remains a frequent cancer worldwide, and most tumors are diagnosed at localized stages. Urothelial carcinoma (UC) accounts for 90% of bladder cancer cases. Sarcomatoid carcinoma (SaC) of the bladder is a rare variant (0.5% of total bladder cancers) characterized by 2 components based on histology; the epithelial and mesenchymal phenotypes, which can be easily differentiated by immunohistochemistry. SaC has similar epidemiologic features to UC but different behavior, aggressiveness, and prognosis. In this review, we summarize the main differences between UC bladder cancers and SaC subtypes. The therapeutic strategies used in SaC today do not differ much from those used for the urothelial variant. However, there is still no standard treatment--the result of a lack of clinical trials for the sarcomatoid variant. Further multicenter comparative studies are needed to devise a better treatment strategy for patients with this rare histologic tumor subtype.

Animal models for bladder cancer: The model establishment and evaluation (Review)

Bladder cancer is the most common type of tumor in the urogenital system. Approximately 75% of patients with bladder cancer present with non-muscle-invasive cancer, which is generally treated by transurethral resection and intravesical chemotherapy. In spite of different therapeutic options, there remains a very variable risk of recurrence and progression. Novel therapeutic methods of treating bladder cancer are urgently required. The exploration and preclinical evaluation of new treatments requires an animal tumor model that mimics the human counterpart. Animal models are key in bladder cancer research and provide a bridge to the clinic. Various animal bladder cancer models have been described to date, but the tumor take rate is reported to be 30-100%. Establishment of reliable, simple, practicable and reproducible animal models remains an ongoing challenge. The present review summarizes the latest developments with regard to the establishment of animal models and tumor evaluation.

MiRNA in bladder carcinogenesis: A review

Bladder cancer (BC) is the second urological malignancy in incidence, currently being one of the most neoplasms studied with profile and biology poorly defined. In the world, BC is responsible by about 386000 new cases and 150000 deaths annually with considerable economic impact and high costs for health systems. After its discovery more than 20 years, micro RNAs (miRNAs) have been recognized as molecules that work specifically in post-transcriptional control in majority of eukaryote genomes. MiRNAs are a family of small non-coding RNAs of 19-25 nucleotides in length, expressed in a wide variety of organisms, comprising plants, worms and mammals, including humans. They have a fundamental role in physiological and pathological processes in organs and tissues in a context-dependent manner. This review brings new roles of protective and oncogenic miRNAs linked to carcinogenesis of urothelial carcinoma of the bladder, and associated with behavior of disease. Many studies have demonstrated promising roles of miRNAs working as diagnostic and prognostic biomarkers or involved in target therapies, consolidating miRNAs as crucial players in human cancer. This review allowed a reflection about the true functions of miRNAs in bladder carcinogenesis. Not only by their wide capacities of action, but also by abilities in define the cell date. The future of anti-tumor target therapies will be based not in one, but in groups of miRNAs working together in several steps of carcinogenic process, being able to identify the disease, predicting behavior and effectively treat bladder cancer.

Interstitial calcinosis in renal papillae of genetically engineered mouse models: relation to Randall's plaques

Genetically engineered mouse models (GEMMs) have been highly instrumental in elucidating gene functions and molecular pathogenesis of human diseases, although their use in studying kidney stone formation or nephrolithiasis remains relatively limited. This review intends to provide an overview of several knockout mouse models that develop interstitial calcinosis in the renal papillae. Included herein are mice deficient for Tamm-Horsfall protein (THP; also named uromodulin), osteopontin (OPN), both THP and OPN, Na(+)-phosphate cotransporter Type II (Npt2a) and Na(+)/H(+) exchanger regulatory factor (NHERF-1). The baseline information of each protein is summarized, along with key morphological features of the interstitial calcium deposits in mice lacking these proteins. Attempts are made to correlate the papillary interstitial deposits found in GEMMs with Randall's plaques, the latter considered precursors of idiopathic calcium stones in patients. The pathophysiology that underlies the renal calcinosis in the knockout mice is also discussed wherever information is available. Not all the knockout models are allocated equal space because some are more extensively characterized than others. Despite the inroads already made, the exact physiological underpinning, origin, evolution and fate of the papillary interstitial calcinosis in the GEMMs remain incompletely defined. Greater investigative efforts are warranted to pin down the precise role of the papillary interstitial calcinosis in nephrolithiasis using the existing models. Additionally, more sophisticated, second-generation GEMMs that allow gene inactivation in a time-controlled manner and "compound mice" that bear several genetic alterations are urgently needed, in light of mounting evidence that nephrolithiasis is a multifactorial, multi-stage and polygenic disease.

miRNA panels as biomarkers for bladder cancer

Aim: Specific miRNA profiles have been identified for several samples from patients with bladder cancer. The results are not always congruent and partly contradictory. A comparison of published data was performed to select potential markers. Materials & methods: A literature search in PubMed identified 79 articles published prior to June 2013. Reports regarding the detection of miRNAs in urine and blood have rarely been published; to date, nine respectively three articles are available. Results: The comparison of published data proved the utility of miRNAs as diagnostic and prognostic indicators of bladder cancer. In urine samples from bladder cancer patients, seven miRNAs were concordantly expressed with tumor tissues. Conclusion: Standardization is strictly required in pre-analytics and methods of miRNA measurements.

[How do metastases of urological tumors develop?]

This overview mainly focuses on the topic of epithelial tumors (carcinomas) because urological tumors are generally of this type. The importance of the topic is reflected by the fact that patients rarely die of the primary tumor, but the majority die of metastases that cause life-threatening situations. More recent findings show that treatment decisions should be based on the metastasis site and less on the tumor's tissue of origin. Given the progression of clinical oncology toward individualized medicine, a better understanding of the biology of metastases is therefore acute and includes some important challenges.

Expression profile of microrna-145 in urothelial bladder cancer

PURPOSE

Bladder cancer (BC) is the second most common malignancy of the urinary tract, with high mortality. The knowledge of the molecular pathways associated with BC carcinogenesis is crucial to identify new diagnostic and prognostic biomarkers. MicroRNAs (miRNAs) are short non-coding RNA molecules that play important roles in the regulation of gene expression by acting directly on mRNAs. miR-145 has been considered as a tumor suppressor, which targets the c-MYC, MUC-1 and FSCN1 genes. Our aim was to evaluate the expression profile of miR-145 in low-grade non-invasive and high-grade invasive bladder urothelial carcinomas.

MATERIALS AND METHODS

We studied 30 specimens of low-grade, non-invasive pTa and 30 of pT2/pT3 high-grade invasive UC obtained by transurethral resection or radical cystectomy, followed over a mean time of 16.1 months. Normal controls were represented by five samples of normal bladder biopsy from patients who underwent retropubic prostatectomy to treat BPH. miRNA extraction and cDNA generation were performed using commercial kits. Analysis was performed by qRT-PCR, and miR-145 expression was calculated using the 2-(▵▵ct) method; we used RNU-43 and RNU-48 as endogenous controls.

RESULTS

miR-145 was under-expressed in 73.3% and 86.7% of pTa and pT2/pT3, respectively, with expression means of 1.61 for the former and 0.66 for the last. There were no significant differences in miR-145 expression and histological grade, tumor stage, angiolymphatic neoplastic invasion and tumor recurrence.

CONCLUSION

miR-145 is under-expressed in low-grade, non-invasive and high-grade invasive urothelial bladder carcinoma and may play an important role in the carcinogenesis pathway, being an interesting candidate diagnostic marker.

Current preclinical models for the advancement of translational bladder cancer research

Bladder cancer is a common disease representing the fifth most diagnosed solid tumor in the United States. Despite this, advances in our understanding of the molecular etiology and treatment of bladder cancer have been relatively lacking. This is especially apparent when recent advances in other cancers, such as breast and prostate, are taken into consideration. The field of bladder cancer research is ready and poised for a series of paradigm-shifting discoveries that will greatly impact the way this disease is clinically managed. Future preclinical discoveries with translational potential will require investigators to take full advantage of recent advances in molecular and animal modeling methodologies. We present an overview of current preclinical models and their potential roles in advancing our understanding of this deadly disease and for advancing care.

Stage, grade and behavior of bladder urothelial carcinoma defined by the microRNA expression profile

PURPOSE

We identified miRNA expression profiles in urothelial carcinoma that are associated with grade, stage, and recurrence-free and disease specific survival.

MATERIALS AND METHODS

The expression of 14 miRNAs was evaluated by quantitative reverse transcriptase-polymerase chain reaction in surgical specimens from 30 patients with low grade, noninvasive (pTa) and 30 with high grade, invasive (pT2-3) urothelial carcinoma. Controls were normal bladder tissue from 5 patients who underwent surgical treatment for benign prostatic hyperplasia. Endogenous controls were RNU-43 and RNU-48. miRNA profiles were compared and Kaplan-Meier curves were constructed to analyze disease-free and disease specific survival.

RESULTS

miR-100 was under expressed in 100% of low grade pTa specimens (p <0.001) and miR-10a was over expressed in 73.3% (p <0.001). miR-21 and miR-205 were over expressed in high grade pT2-3 disease (p = 0.02 and <0.001, respectively). The other miRNAs were present at levels similar to those of normal bladder tissue or under expressed in each tumor group. miR-21 over expression (greater than 1.08) was related to shorter disease-free survival in patients with low grade pTa urothelial carcinoma. Higher miR-10a levels (greater than 2.30) were associated with shorter disease-free and disease specific survival in patients with high grade pT2-3 urothelial carcinoma.

CONCLUSIONS

Four miRNAs were differentially expressed in the 2 urothelial carcinoma groups. miR-100 and miR-10a showed under expression and over expression, respectively, in low grade pTa tumors. miR-21 and miR-205 were over expressed in pT2-3 disease. In addition, miR-10a and miR-21 over expression was associated with shorter disease-free and disease specific survival. miRNAs could be incorporated into the urothelial carcinoma molecular pathway. These miRNAs could also serve as new diagnostic or prognostic markers and new target drugs.

Autophagy limits the cytotoxic effects of the AKT inhibitor AZ7328 in human bladder cancer cells

BACKGROUND

Mutations that activate the PI3K/AKT/mTOR pathway are relatively common in urothelial (bladder) cancers, but how these pathway mutations affect AKT dependency is not known. We characterized the relationship between AKT pathway mutational status and sensitivity to the effects of the selective AKT kinase inhibitor AZ7328 using a panel of 12 well-characterized human bladder cancer cell lines.

METHODS

Sequenome DNA sequencing was performed to identify mutations in a panel of 12 urothelial cancer cell lines. Drug-induced proliferative inhibition and apoptosis were quantified using MTT assays and propidium iodide staining with FACS analyses. Protein activation via phosphorylation was measured by immunoblotting. Autophagy was measured by LC3 immunofluorescence and immunoblotting.

RESULTS

AZ7328 inhibited proliferation and AKT substrate phosphorylation in a concentration-dependent manner but had minimal effects on apoptosis. Proliferative inhibition correlated loosely with the presence of activating PIK3CA mutations and was strengthened in combination with the mTOR inhibitor rapamycin. AZ7328 induced autophagy in some of the lines, and in the cells exposed to a combination of AZ7328 and chemical autophagy inhibitors apoptosis was induced.

CONCLUSIONS

The cytostatic effects of AZ7328 correlate with PIK3CA mutations and are greatly enhanced by dual pathway inhibition using an mTOR inhibitor. Furthermore, AZ7328 can interact with autophagy inhibitors to induce apoptosis in some cell lines. Overall, our results support the further evaluation of combinations of PI3K/AKT/mTOR pathway and autophagy inhibitors in pre-clinical in vivo models and ultimately in patients with PIK3CA mutant bladder cancers.

Loss of the urothelial differentiation marker FOXA1 is associated with high grade, late stage bladder cancer and increased tumor proliferation

Approximately 50% of patients with muscle-invasive bladder cancer (MIBC) develop metastatic disease, which is almost invariably lethal. However, our understanding of pathways that drive aggressive behavior of MIBC is incomplete. Members of the FOXA subfamily of transcription factors are implicated in normal urogenital development and urologic malignancies. FOXA proteins are implicated in normal urothelial differentiation, but their role in bladder cancer is unknown. We examined FOXA expression in commonly used in vitro models of bladder cancer and in human bladder cancer specimens, and used a novel in vivo tissue recombination system to determine the functional significance of FOXA1 expression in bladder cancer. Logistic regression analysis showed decreased FOXA1 expression is associated with increasing tumor stage (p<0.001), and loss of FOXA1 is associated with high histologic grade (p<0.001). Also, we found that bladder urothelium that has undergone keratinizing squamous metaplasia, a precursor to the development of squamous cell carcinoma (SCC) exhibited loss of FOXA1 expression. Furthermore, 81% of cases of SCC of the bladder were negative for FOXA1 staining compared to only 40% of urothelial cell carcinomas. In addition, we showed that a subpopulation of FOXA1 negative urothelial tumor cells are highly proliferative. Knockdown of FOXA1 in RT4 bladder cancer cells resulted in increased expression of UPK1B, UPK2, UPK3A, and UPK3B, decreased E-cadherin expression and significantly increased cell proliferation, while overexpression of FOXA1 in T24 cells increased E-cadherin expression and significantly decreased cell growth and invasion. In vivo recombination of bladder cancer cells engineered to exhibit reduced FOXA1 expression with embryonic rat bladder mesenchyme and subsequent renal capsule engraftment resulted in enhanced tumor proliferation. These findings provide the first evidence linking loss of FOXA1 expression with histological subtypes of MIBC and urothelial cell proliferation, and suggest an important role for FOXA1 in the malignant phenotype of MIBC.

Urothelial tumor initiation requires deregulation of multiple signaling pathways: implications in target-based therapies

Although formation of urothelial carcinoma of the bladder (UCB) requires multiple steps and proceeds along divergent pathways, the underlying genetic and molecular determinants for each step and pathway remain undefined. By developing transgenic mice expressing single or combinatorial genetic alterations in urothelium, we demonstrated here that overcoming oncogene-induced compensatory tumor barriers was critical for urothelial tumor initiation. Constitutively active Ha-ras (Ras*) elicited urothelial hyperplasia that was persistent and did not progress to tumors over a 10 months period. This resistance to tumorigenesis coincided with increased expression of p53 and all pRb family proteins. Expression of a Simian virus 40 T antigen (SV40T), which disables p53 and pRb family proteins, in urothelial cells expressing Ras* triggered early-onset, rapidly-growing and high-grade papillary UCB that strongly resembled the human counterpart (pTaG3). Urothelial cells expressing both Ras* and SV40T had defective G(1)/S checkpoint, elevated Ras-GTPase and hyperactivated AKT-mTOR signaling. Inhibition of the AKT-mTOR pathway with rapamycin significantly reduced the size of high-grade papillary UCB but hyperactivated mitogen-activated protein kinase (MAPK). Inhibition of AKT-mTOR, MAPK and STAT3 altogether resulted in much greater tumor reduction and longer survival than did inhibition of AKT-mTOR pathway alone. Our studies provide the first experimental evidence delineating the combinatorial genetic events required for initiating high-grade papillary UCB, a poorly defined and highly challenging clinical entity. Furthermore, they suggest that targeted therapy using a single agent such as rapamycin may not be highly effective in controlling high-grade UCB and that combination therapy employing inhibitors against multiple targets are more likely to achieve desirable therapeutic outcomes.

S6K1 and 4E-BP1 are independent regulated and control cellular growth in bladder cancer

Aberrant activation and mutation status of proteins in the phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) and the mitogen activated protein kinase (MAPK) signaling pathways have been linked to tumorigenesis in various tumors including urothelial carcinoma (UC). However, anti-tumor therapy with small molecule inhibitors against mTOR turned out to be less successful than expected. We characterized the molecular mechanism of this pathway in urothelial carcinoma by interfering with different molecular components using small chemical inhibitors and siRNA technology and analyzed effects on the molecular activation status, cell growth, proliferation and apoptosis. In a majority of tested cell lines constitutive activation of the PI3K was observed. Manipulation of mTOR or Akt expression or activity only regulated phosphorylation of S6K1 but not 4E-BP1. Instead, we provide evidence for an alternative mTOR independent but PI3K dependent regulation of 4E-BP1. Only the simultaneous inhibition of both S6K1 and 4E-BP1 suppressed cell growth efficiently. Crosstalk between PI3K and the MAPK signaling pathway is mediated via PI3K and indirect by S6K1 activity. Inhibition of MEK1/2 results in activation of Akt but not mTOR/S6K1 or 4E-BP1. Our data suggest that 4E-BP1 is a potential new target molecule and stratification marker for anti cancer therapy in UC and support the consideration of a multi-targeting approach against PI3K, mTORC1/2 and MAPK.

Expression of GLUT1 is associated with increasing grade of malignancy in non-invasive and invasive urothelial carcinomas of the bladder

Glucose Transporter 1 (GLUT1) belongs to the expanding mammalian facilitative glucose transporter family. Elevated GLUT1 protein expression has been observed in the majority of urothelial carcinomas, with various effects on clinicopathological parameters. Whereas malignant cells have an accelerated metabolism with increased energy requirements, the membranous expression of GLUTs is amplified. GLUT1 protein expression was evaluated in urothelial tumours of increasing grade of malignancy, supplemented by a tumour proliferation analysis. Particular attention was paid to non-invasive precursors of urothelial carcinoma. A total of 105 paraffin-embedded samples were classified (normal urothelium, low/high-grade papillary carcinoma, carcinoma in situ and invasive carcinoma). Grading and staging were conducted using the 1998 ISUP/2004 WHO criteria. The staining intensity of GLUT1 was assessed with a standard immunoreactive score (IRS). The Ki-67 index was assessed by counting positive nuclei in representative urothelial hot spots. Results showed that an increased GLUT1-IRS and mean count of Ki-67-positive cells were significantly associated with an increased grade of malignancy (p<0.0001), particularly in non-invasive tumours. GLUT1-IRS was significantly associated with a Ki-67-labelled proliferative fraction (p<0.0001). No significant association regarding tumour grade or stage was observed within the invasive carcinoma group. GLUT1 protein expression was found to be strongly correlated with increased malignant potential, particularly in non-invasive urothelial carcinomas. The increase of GLUT1 expression may reflect a preinvasive metabolic switch in terms of enhanced cell metabolism concomitant to known genetic alterations. A further increase in invasive carcinomas may be related to hypoxic conditions.

Contemporary management of low-risk bladder cancer

Bladder cancer comprises a heterogeneous group of tumors, the majority of which are non-muscle-invasive bladder cancer (NMIBC) at initial presentation. Low-risk bladder cancer--defined as pTa low-grade papillary tumors--is the type of NMIBC with the most favorable oncologic outcome. Although the risk of progression is less than 1% in 5 years, almost 15% will recur after 1 year, and 32% after 5 years. A complete transurethral resection, followed by an immediate single postoperative instillation of chemotherapy will reduce the risk of recurrence for the first 2 years. Follow-up cystoscopy is required to detect recurrence; in the vast majority of cases the recurrent tumor is of the same stage and grade as the primary tumor. The first follow-up visit, 3 months after surgery, is the most important in predicting risk of recurrence for the future. Recent developments in profiling urine and cancer tissue make it possible to better predict risk of progression and recurrence. In the future this profiling will play an important role in the timing and the choice of treatment, as well as guiding follow-up procedures.

[Current knowledge in molecular pathology of urothelial cancer]

Results of molecular pathology have supported changes in the 2004 WHO classification of urothelial cancer. Since then new molecular data such as the distribution pattern of the fibroblast growth factor receptor 3 (FGFR3) has further supported the principle of low and high grade entities of urothelial carcinoma. Animal experiments with knockout mice and conditional knockout systems reveal important parallels to humans and results emphasize the cellular context as a trigger for malignancy. One special feature of the urothelium is its high protection of the urothelial cells by members of the retinoblastoma gene family, efficiently inhibiting invasion even in the presence of p53 mutations. In search of the tumor stem cell phenotype the basal cell phenotype is the focus of attention providing a high clonogenic potential. At the same time detailed analysis of the distribution of mutations in the mitochondrial genome within the urothelium will help to gain insight into the spreading of normal cell or tumor cell clones. The overall data in urological oncology provide evidence that diagnostic and prognostic tools for urothelial cancer can only be reached with multiparametric approaches.