Molecular biology of bladder cancer: prognostic and clinical implications

Single-cell RNAseq and longitudinal proteomic analysis of a novel semi-spontaneous urothelial cancer model reveals tumor cell heterogeneity and pretumoral urine protein alterations

Bladder cancer, one of the most prevalent malignancies worldwide, remains hard to classify due to a staggering molecular complexity. Despite a plethora of diagnostic tools and therapies, it is hard to outline the key steps leading up to the transition from high-risk non-muscle-invasive bladder cancer (NMIBC) to muscle-invasive bladder cancer (MIBC). Carcinogen-induced murine models can recapitulate urothelial carcinogenesis and natural anti-tumor immunity. Herein, we have developed and profiled a novel model of progressive NMIBC based on 10 weeks of OH-BBN exposure in hepatocyte growth factor/cyclin dependent kinase 4 (R24C) (Hgf-Cdk4R24C) mice. The profiling of the model was performed by histology grading, single cell transcriptomic and proteomic analysis, while the derivation of a tumorigenic cell line was validated and used to assess in vivo anti-tumor effects in response to immunotherapy. Established NMIBC was present in females at 10 weeks post OH-BBN exposure while neoplasia was not as advanced in male mice, however all mice progressed to MIBC. Single cell RNA sequencing analysis revealed an intratumoral heterogeneity also described in the human disease trajectory. Moreover, although immune activation biomarkers were elevated in urine during carcinogen exposure, anti-programmed cell death protein 1 (anti-PD1) monotherapy did not prevent tumor progression. Furthermore, anti-PD1 immunotherapy did not control the growth of subcutaneous tumors formed by the newly derived urothelial cancer cell line. However, treatment with CpG-oligodeoxynucleotides (ODN) significantly decreased tumor volume, but only in females. In conclusion, the molecular map of this novel preclinical model of bladder cancer provides an opportunity to further investigate pharmacological therapies ahead with regards to both targeted drugs and immunotherapies to improve the strategies of how we should tackle the heterogeneous tumor microenvironment in urothelial bladder cancer to improve responses rates in the clinic.

lncRNA and Mechanisms of Drug Resistance in Cancers of the Genitourinary System

Available systemic treatment options for cancers of the genitourinary system have experienced great progress in the last decade. However, a large proportion of patients eventually develop resistance to treatment, resulting in disease progression and shorter overall survival. Biomarkers indicating the increasing resistance to cancer therapies are yet to enter clinical routine. Long non-coding RNAs (lncRNA) are non-protein coding RNA transcripts longer than 200 nucleotides that exert multiple types of regulatory functions of all known cellular processes. Increasing evidence supports the role of lncRNAs in cancer development and progression. Additionally, their involvement in the development of drug resistance across various cancer entities, including genitourinary malignancies, are starting to be discovered. Consequently, lncRNAs have been suggested as factors in novel therapeutic strategies to overcome drug resistance in cancer. In this review, the existing evidences on lncRNAs and their involvement in mechanisms of drug resistance in cancers of the genitourinary system, including renal cell carcinoma, bladder cancer, prostate cancer, and testicular cancer, will be highlighted and discussed to facilitate and encourage further research in this field. We summarize a significant number of lncRNAs with proposed pathways in drug resistance and available reported studies.

Molecular Prognostication in Bladder Cancer

Clinical outcomes for patients with bladder cancer have largely remained unchanged over the last three decades despite improvements in surgical techniques, perioperative therapies, and postoperative management. Current management still heavily relies on pathologic staging that does not always reflect an individual patient's risk. The genesis and progression of bladder cancer is now increasingly recognized as being a result of alterations in several pathways that affect the cell cycle, apoptosis, cellular signaling, gene regulation, immune modulation, angiogenesis, and tumor cell invasion. Multiplexed assessment of biomarkers associated with alterations in these pathways offers novel insights into tumor behavior while identifying panels that are capable of reproducibly predicting patient outcomes. Future management of bladder cancer will likely incorporate such prognostic molecular models for risk stratification and treatment personalization.

Oncolytic virotherapy for urological cancers

Oncolytic virotherapy is a cancer treatment in which replication-competent viruses are used that specifically infect, replicate in and lyse malignant tumour cells, while minimizing harm to normal cells. Anecdotal evidence of the effectiveness of this strategy has existed since the late nineteenth century, but advances and innovations in biotechnological methods in the 1980s and 1990s led to a renewed interest in this type of therapy. Multiple clinical trials investigating the use of agents constructed from a wide range of viruses have since been performed, and several of these enrolled patients with urological malignancies. Data from these clinical trials and from preclinical studies revealed a number of challenges to the effectiveness of oncolytic virotherapy that have prompted the development of further sophisticated strategies. Urological cancers have a range of distinctive features, such as specific genetic mutations and cell surface markers, which enable improving both effectiveness and safety of oncolytic virus treatments. The strategies employed in creating advanced oncolytic agents include alteration of the virus tropism, regulating transcription and translation of viral genes, combination with chemotherapy, radiotherapy or gene therapy, arming viruses with factors that stimulate the immune response against tumour cells and delivery technologies to ensure that the viral agent reaches its target tissue.

Molecular substratification of bladder cancer: moving towards individualized patient management

Despite advances in surgical techniques, perioperative therapies and postoperative management, outcomes for patients with bladder cancer have largely remained unchanged. Current management of bladder cancer still relies on pathologic staging that does not always reflect the risk for an individual patient. Studies assessing molecular alterations in individual tumors are offering insights into the myriad of cellular pathways that are deregulated in bladder tumorigenesis and progression. Alterations in pathways involved in cell-cycle regulation, apoptosis, cell signaling, angiogenesis and tumor-cell invasion have been shown to influence disease behavior. High-throughput assays are now allowing multiplexed assessment of biomarker alterations, thereby enabling characterization of novel molecular subtypes of bladder cancer. Such approaches have also been used for discovery and validation of robust prognostic molecular signatures. The future of bladder cancer management will rely on the use of validated multimarker panels for risk stratification, optimal surgical management, and theranostic strategies to identify and target specific alterations in individual tumors.

Differentially expressed genes in metastatic advanced Egyptian bladder cancer

BACKGROUND

Bladder cancer is one of the most common cancers worldwide. Gene expression profiling using microarray technologies improves the understanding of cancer biology. The aim of this study was to determine the gene expression profile in Egyptian bladder cancer patients.

MATERIALS AND METHODS

Samples from 29 human bladder cancers and adjacent non-neoplastic tissues were analyzed by cDNA microarray, with hierarchical clustering and multidimensional analysis.

RESULTS

Five hundred and sixteen genes were differentially expressed of which SOS1, HDAC2, PLXNC1, GTSE1, ULK2, IRS2, ABCA12, TOP3A, HES1, and SRP68 genes were involved in 33 different pathways. The most frequently detected genes were: SOS1 in 20 different pathways; HDAC2 in 5 different pathways; IRS2 in 3 different pathways. There were 388 down-regulated genes. PLCB2 was involved in 11 different pathways, MDM2 in 9 pathways, FZD4 in 5 pathways, p15 and FGF12 in 4 pathways, POLE2 in 3 pathways, and MCM4 and POLR2E in 2 pathways. Thirty genes showed significant differences between transitional cell cancer (TCC) and squamous cell cancer (SCC) samples. Unsupervised cluster analysis of DNA microarray data revealed a clear distinction between low and high grade tumors. In addition 26 genes showed significant differences between low and high tumor stages, including fragile histidine triad, Ras and sialyltransferase 8 (alpha) and 16 showed significant differences between low and high tumor grades, like methionine adenosyl transferase II, beta.

CONCLUSIONS

The present study identified some genes, that can be used as molecular biomarkers or target genes in Egyptian bladder cancer patients.

Beyond conventional chemotherapy: Emerging molecular targeted and immunotherapy strategies in urothelial carcinoma

Advanced urothelial carcinoma is frequently lethal, and improvements in cytotoxic chemotherapy have plateaued. Recent technological advances allows for a comprehensive analysis of genomic alterations in a timely manner. The Cancer Genome Atlas (TCGA) study revealed that there are numerous genomic aberrations in muscle-invasive urothelial carcinoma, such as TP53, ARID1A, PIK3CA, ERCC2, FGFR3, and HER2. Molecular targeted therapies against similar genetic alterations are currently available for other malignancies, but their efficacy in urothelial carcinoma has not been established. This review describes the genomic landscape of malignant urothelial carcinomas, with an emphasis on the potential to prosecute these tumours by deploying novel targeted agents and immunotherapy in appropriately selected patient populations.

Molecular biology and targeted therapies for urothelial carcinoma

Metastatic urothelial cancer (UC) is associated with poor prognosis. In the first-line setting, platinum-based chemotherapy is the standard of care but resistance rapidly occurs. With no validated treatment proven to increase survival after platinum failure, there is an urgent unmet medical need to develop new and efficacious cytotoxic agents. A better understanding of the molecular signaling pathways regulating UC has led to the development of new and innovative therapeutic strategies. Despite this, many recent drugs show only modest activity as single agents, and combining them with standard chemotherapy does not seem to enhance efficacy. Ongoing research is producing, however, a generation of new drugs that are showing promising results in clinical trials. This paper aims to review the most important mechanisms in bladder cancer tumorigenesis and describe the new therapeutic options currently undergoing evaluation in clinical trials.

Prognostic value of PDCD6 polymorphisms and the susceptibility to bladder cancer

Programmed cell death 6 (PDCD6) has recently been found dysregulated in tumors of various origin. The aim of this study is to explore the association between PDCD6 genetic polymorphisms and susceptibility to bladder cancer and survival of patients with bladder cancer. Two tag SNPs of PDCD6, rs3756712 and rs4957014, were genotyped in 332 patients with bladder cancer and 509 controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and correlated with patients' survival. The frequencies of G allele and GG genotype of rs3756712 in patients were significantly lower than that of controls (P = 0.001, odds ratio [OR] = 0.68 for G allele; P = 0.024, OR = 0.53 for GG genotype in the recessive genetic model, respectively). The GT genotype of rs4957014 was associated with decreased susceptibility to bladder cancer in the overdominant genetic model (P = 0.023, OR = 0.72). Kaplan-Meier curves revealed a significant higher risk for death in superficial bladder cancer patients harboring GG homozygous of rs3756712 (P < 0.001), and an increased risk for recurrence in invasive bladder cancer patients carrying GT heterozygous of rs4957014 (P = 0.04). Multiple Cox regression analysis identified rs3756712 GG genotype as an independent prognostic factor for death in superficial bladder cancer patients (hazard ratio [HR] = 5.11, P = 0.01), and rs4957014 GT genotype as an independent prognostic factor for recurrence in invasive bladder cancer patients (HR = 1.93, P = 0.03). PDCD6 may represent a biomarker candidate gene that could help to identify a group of patients at high risk for recurrence and death.

Cholera toxin, a typical protein kinase A activator, induces G1 phase growth arrest in human bladder transitional cell carcinoma cells via inhibiting the c-Raf/MEK/ERK signaling pathway

The biotoxin cholera toxin has been demonstrated to have anti-tumor activity in numerous types of cancer, including glioma. However, the role of cholera toxin in the tumorigenesis of transitional cell carcinoma (TCC), the most common malignant tumor of the bladder, remains to be elucidated. To address this, in the present study, two TCC cell lines, T24 and UM-UC-3, were treated with cholera toxin [protein kinase A (PKA) activator] and KT5720 (PKA inhibitor). Cell survival and proliferation, cell cycle alterations and apoptosis were analyzed using Hoechst staining, the MTT assay, fluorescence microscopy and flow cytometry. Western blot analysis was used to detect the expression of proteins involved in cell cycle regulation. The results revealed that cholera toxin significantly induced G1 arrest and downregulated the expression of cyclin D1 and cyclin-dependent kinase 4/6 in the TCC cell lines, and this was rescued by KT5720. Furthermore, it was demonstrated that cholera toxin downregulated the activation of the c-Raf/Mek/Erk cascade, an important mediator of tumor cell proliferation, via the PKA-dependent c-Raf phosphorylation at Ser-43. Furthermore, inhibition of Mek activity with UO126 mimicked the effects of cholera toxin. In conclusion, these results confirmed that cholera toxin specifically inhibited proliferation and induced G1 phase arrest in human bladder TCC cells. This effect was due to PKA-dependent inactivation of the c-Raf/Mek/Erk pathway. This suggested that cholera toxin may be a viable therapeutic treatment against tumorigenesis and proliferation in bladder cancer.

Transcriptome profiling of a multiple recurrent muscle-invasive urothelial carcinoma of the bladder by deep sequencing

Urothelial carcinoma of the bladder (UCB) is one of the commonly diagnosed cancers in the world. The UCB has the highest rate of recurrence of any malignancy. A genome-wide screening of transcriptome dysregulation between cancer and normal tissue would provide insight into the molecular basis of UCB recurrence and is a key step to discovering biomarkers for diagnosis and therapeutic targets. Compared with microarray technology, which is commonly used to identify expression level changes, the recently developed RNA-seq technique has the ability to detect other abnormal regulations in the cancer transcriptome, such as alternative splicing. In this study, we performed high-throughput transcriptome sequencing at ∼50× coverage on a recurrent muscle-invasive cisplatin-resistance UCB tissue and the adjacent non-tumor tissue. The results revealed cancer-specific differentially expressed genes between the tumor and non-tumor tissue enriched in the cell adhesion molecules, focal adhesion and ECM-receptor interaction pathway. Five dysregulated genes, including CDH1, VEGFA, PTPRF, CLDN7, and MMP2 were confirmed by Real time qPCR in the sequencing samples and the additional eleven samples. Our data revealed that more than three hundred genes showed differential splicing patterns between tumor tissue and non-tumor tissue. Among these genes, we filtered 24 cancer-associated alternative splicing genes with differential exon usage. The findings from RNA-Seq were validated by Real time qPCR for CD44, PDGFA, NUMB, and LPHN2. This study provides a comprehensive survey of the UCB transcriptome, which provides better insight into the complexity of regulatory changes during recurrence and metastasis.

Target protein for Xklp2 (TPX2), a microtubule-related protein, contributes to malignant phenotype in bladder carcinoma

Increasing evidence demonstrated that TPX2 was highly expressed and tightly associated with human tumor development and progression. However, its precise role in bladder carcinoma remains to be delineated. In the present study, we revealed the high expression of TPX2 at both mRNA and protein levels in bladder carcinoma tissues and cells, and TPX2 levels in pN1-3 and pT2-4 status were significantly higher than those in pN0 and pTa-T1 status, respectively. Additionally, high TPX2 level was strongly associated with pT status (P = 0.001), higher histological grade (P = 0.001), lymph node metastasis (P = 0.022), and shorter survival time (P = 0.0279). Further investigation showed that TPX2 level in T24 cells was markedly higher than those in 5637, J82 and RT4 cells, in which RT4, a well-differentiated cell line derived from bladder carcinoma with low-grade non-invasive T0, displayed the lowest TPX2 mRNA and protein levels. Besides, TPX2 overexpression promoted proliferation and tumorigenicity, shortened cell cycle in G0/G1 phase, and suppressed cell apoptosis in T24 cells; conversely, TPX2 depletion exhibited opposite effects. Furthermore, TPX2 overexpression evoked the elevation of cyclin D1 and cdk2 levels as well as reduction of p21 level and caspase-3 activity, whereas reversed effects were observed in TPX2-depleted T24 cells. Taken altogether, TPX2 may play a central role in the development and progression of bladder carcinoma, and thus inhibition of TPX2 level may be a novel strategy for therapy of the patients with bladder carcinoma.

Combination of molecular alterations and smoking intensity predicts bladder cancer outcome: a report from the Los Angeles Cancer Surveillance Program

BACKGROUND

Traditional single-marker and multimarker molecular profiling approaches in bladder cancer do not account for major risk factors and their influence on clinical outcome. This study examined the prognostic value of molecular alterations across all disease stages after accounting for clinicopathological factors and smoking, the most common risk factor for bladder cancer in the developed world, in a population-based cohort.

METHODS

Primary bladder tumors from 212 cancer registry patients (median follow-up, 13.2 years) were immunohistochemically profiled for Bax, caspase-3, apoptotic protease-activating factor 1 (Apaf-1), Bcl-2, p53, p21, cyclooxygenase-2, vascular endothelial growth factor, and E-cadherin alterations. "Smoking intensity" quantified the impact of duration and daily frequency of smoking.

RESULTS

Age, pathological stage, surgical modality, and adjuvant therapy administration were significantly associated with survival. Increasing smoking intensity was independently associated with worse outcome (P < .001). Apaf-1, E-cadherin, and p53 were prognostic for outcome (P = .005, .014, and .032, respectively); E-cadherin remained prognostic following multivariable analysis (P = .040). Combined alterations in all 9 biomarkers were prognostic by univariable (P < .001) and multivariable (P = .006) analysis. A multivariable model that included all 9 biomarkers and smoking intensity had greater accuracy in predicting prognosis than models composed of standard clinicopathological covariates without or with smoking intensity (P < .001 and P = .018, respectively).

CONCLUSIONS

Apaf-1, E-cadherin, and p53 alterations individually predicted survival in bladder cancer patients. Increasing number of biomarker alterations was significantly associated with worsening survival, although markers comprising the panel were not necessarily prognostic individually. Predictive value of the 9-biomarker panel with smoking intensity was significantly higher than that of routine clinicopathological parameters alone.

Investigational cell cycle inhibitors in clinical trials for bladder cancer

INTRODUCTION

Cancer-related cell cycle defects are often mediated by alterations in activity of diverse cell cycle regulators. The development of cell cycle inhibitors has undergone a gradual evolution, and new investigational drugs have been extensively tested as a single agent or combination with conventional chemotherapeutic drugs.

AREAS COVERED

This review covers a broad perspective of how the cell cycle is deregulated in bladder cancer and discusses the clinical trials of cell cycle inhibitors.

EXPERT OPINION

Although diverse cell cycle inhibitors have been considered as relevant drug candidates for cancer therapy owing to their potential role in restoring control of the cell cycle, these inhibitors have not been yet widely tested in human bladder cancer. Numerous studies already reported that deregulation of cell cycle controls has been commonly observed in bladder cancer cells, thus warranting clinical trials of these inhibitors in advanced bladder cancer patients. In addition, nonmuscle invasive bladder cancer (NMIBC) and muscle invasive bladder cancer (MIBC) show different clinical and molecular biological characteristics, although ∼ 10 - 20% of NMIBC will progress to MIBC. Therefore, adequate cell cycle inhibitors have to be chosen for bladder cancer treatment based on the different genetic features between NMIBC and MIBC related to cell cycle regulators.

Prognostic value of cell-cycle regulation biomarkers in bladder cancer

The determination of prognosis in bladder cancer is currently based on staging methods that rely primarily on the pathological stage of a tumor with limited objective correlates. The development and progression of bladder cancer involve alterations in several cellular pathways. Dysregulation in markers associated with cell-cycle regulation has been the most extensively examined molecular aberration in this cancer. Individual alterations of these markers have been associated with disease outcome, with several observations suggesting that their prognostic potential is independent of pathological stage. While many individual molecules in the cell growth receptor signaling, p53, and retinoblastoma (Rb) pathways have been identified, there is a general lack of consensus on which markers can be adopted in the clinical setting. More recent studies have suggested that the combination of markers as concise panels may be more beneficial in determining the degree of aggressiveness of a given tumor and its impending outcome than individual markers alone. This review will discuss alterations in molecules within pathways controlling cell-cycle regulation in the context of bladder cancer, and their impact on patient outcome when examined individually and in combination.

Over-expression of HER-2 is associated with the stage in carcinomas of the urinary bladder

BACKGROUND

The frequency of over-expression of human epidermal growth factor receptor-2 (HER-2) in bladder cancer is one of the highest among all human malignancies. This over-expression is thought to play a role in aberrant proliferation of cancer cells. Studies on HER-2 expression in bladder carcinoma have shown heterogeneous results.

PURPOSE

The aim of the study was to evaluate the status of HER-2 protein expression in patients with invasive carcinomas of the urinary bladder as related to tumor grade and stage.

MATERIALS AND METHODS

Archival samples from 39 patients (6 women, 33 males) with urinary bladder cancer were analyzed for HER-2 over-expression, using immunohistochemistry with the HercepTest.

RESULTS

HER-2 over-expression was observed in 23/39 tumors (59%) and was more frequent in high-grade than in low-grade carcinomas, but the difference was not statistically significant. A significant correlation was established between HER-2 over-expression and tumor stage (p=0.011). HER-2 expression was more frequent in transitional cell carcinomas (TCC) and adenocarcinomas (AC) as compared with squamous cell carcinoma (SCC). Patients' age and sex were not related to HER-2 over-expression.

CONCLUSION

Over-expression of HER-2 was frequent in carcinomas of the urinary bladder. Knowing the HER-2 status would be helpful in formulating a rational treatment strategy for patients with urinary bladder cancer.

Molecular markers in transitional cell carcinoma of the bladder: New insights into mechanisms and prognosis

Urothelial carcinoma is potentially life-threatening and expensive to treat since for many patients, the diagnosis entails a lifetime of surveillance to detect recurrent disease. Advancements in technology have provided an understanding of the molecular mechanisms of carcinogenesis and defined distinct pathways in tumorigenesis and progression. At the molecular level, urothelial carcinoma is being seen as a disease with distinct pathways of carcinogenesis and progression and thus markers of these processes should be used as both diagnostics and predictors of progression and patient outcome. Herein we present a selective overview of the molecular underpinning of urothelial carcinogenesis and progression and discuss the potential for proteins involved in these processes to serve as biomarkers. The discovery of biomarkers has enabled the elucidation of targets for novel therapeutic agents to disrupt the deregulation underlying the development and progression of urothelial carcinogenesis.

Current therapeutic strategies for invasive and metastatic bladder cancer

BACKGROUND

Bladder cancer is one of the most common cancers in Europe, the United States, and Northern African countries. Muscle-invasive bladder cancer is an aggressive epithelial tumor, with a high rate of early systemic dissemination. Superficial, noninvasive bladder cancer can most often be cured; a good proportion of invasive cases can also be cured by a combined modality approach of surgery, chemotherapy, and radiation. Recurrences are common and mostly manifest as metastatic disease. Those with distant metastatic disease can sometime achieve partial or complete remission with combination chemotherapy.

RECENT DEVELOPMENTS

Better understanding of the biology of the disease has led to the incorporation of molecular and genetic features along with factors such as tumor grade, lympho-vascular invasion, and aberrant histology, thereby allowing identification of 'favorable' and 'unfavorable' cancers which helps a more accurate informed and objective selection of patients who would benefit from neoadjuvant and adjuvant chemotherapy. Gene expression profiling has been used to find molecular signature patterns that can potentially be predictive of drug sensitivity and metastasis. Understanding the molecular pathways of invasive bladder cancer has led to clinical investigation of several targeted therapeutics such as anti-angiogenics, mTOR inhibitors, and anti-EGFR agents.

CONCLUSION

With improvements in the understanding of the biology of bladder cancer, clinical trials studying novel and targeted agents alone or in combination with chemotherapy have increased the armamentarium for the treatment of bladder cancer. Although the novel biomarkers and gene expression profiles have been shown to provide important predictive and prognostic information and are anticipated to be incorporated in clinical decision-making, their exact utility and relevance calls for a larger prospective validation.

Spotlight on differentially expressed genes in urinary bladder cancer

INTRODUCTION

We previously identified common differentially expressed (DE) genes in bladder cancer (BC). In the present study we analyzed in depth, the expression of several groups of these DE genes.

MATERIALS AND METHODS

Samples from 30 human BCs and their adjacent normal tissues were analyzed by whole genome cDNA microarrays, qRT-PCR and Western blotting. Our attention was focused on cell-cycle control and DNA damage repair genes, genes related to apoptosis, signal transduction, angiogenesis, as well as cellular proliferation, invasion and metastasis. Four publicly available GEO Datasets were further analyzed, and the expression data of the genes of interest (GOIs) were compared to those of the present study. The relationship among the GOI was also investigated. GO and KEGG molecular pathway analysis was performed to identify possible enrichment of genes with specific biological themes.

RESULTS

Unsupervised cluster analysis of DNA microarray data revealed a clear distinction in BC vs. control samples and low vs. high grade tumors. Genes with at least 2-fold differential expression in BC vs. controls, as well as in non-muscle invasive vs. muscle invasive tumors and in low vs. high grade tumors, were identified and ranked. Specific attention was paid to the changes in osteopontin (OPN, SPP1) expression, due to its multiple biological functions. Similarly, genes exhibiting equal or low expression in BC vs. the controls were scored. Significant pair-wise correlations in gene expression were scored. GO analysis revealed the multi-facet character of the GOIs, since they participate in a variety of mechanisms, including cell proliferation, cell death, metabolism, cell shape, and cytoskeletal re-organization. KEGG analysis revealed that the most significant pathway was that of Bladder Cancer (p = 1.5×10(-31)).

CONCLUSIONS

The present work adds to the current knowledge on molecular signature identification of BC. Such works should progress in order to gain more insight into disease molecular mechanisms.

Expression profiling for bladder cancer: strategies to uncover prognostic factors

Despite being a common cancer worldwide, management of transitional cell carcinoma of the bladder currently relies primarily on clinical staging and histopathologic parameters. Assaying alterations in molecular pathways can contribute valuable information that can accurately predict outcome and chemotherapeutic response in individual patients with bladder cancer. Medium- to high-throughput gene-expression profiling technologies are now allowing multiplexed assessment of alterations responsible for the genesis and progression of bladder tumors. These investigations employ global or pathway-based approaches to define molecular signatures that can predict prognosis independent of traditional clinical performance metrics. Prognostic panels generated using these strategies can also elucidate the biology of tumor progression and identify potential therapeutic targets.

Methods for the discovery of low-abundance biomarkers for urinary bladder cancer in biological fluids

For the study of bladder cancer and the identification of respective tumor markers, blood and, in particular, urine constitute suitable sources of biological material, while both harboring their specific challenges for analytics concerning low-abundance biomarkers. Dissolved proteins and nucleic acids as well as cells and cell-bound molecules can be the analytes. In urine, exfoliated bladder tumor cells have to be identified and in blood, circulating tumor cells have to be detected among huge amounts of other cells. For the detection of both low-abundance cells and molecules, their specific enrichment prior to analysis is advantageous or even necessary. Adapted methods for the analysis of proteomes and subproteomes by 2D-gel electrophoresis, multidimensional chromatography and antibody arrays are discussed. Analysis of nucleic acid-based markers exploits the high amplification power of PCR and modified PCR combined with previous (subtransciptomes) or subsequent (microarray) enrichment to sensitively and specifically detect markers. DNA mutations, DNA-methylation status and apoptotic DNA fragments, as well as levels of ribonucleic acids including microRNAs, can be analyzed by means of these methods. Finally, the challenge of identifying circulating tumor cells and assigning them to their original tissue is critically discussed.

Systemic therapy of metastatic bladder cancer in the molecular era: current status and future promise

IMPORTANCE OF THE FIELD

Platinum-based chemotherapy is considered the standard-of-care first-line therapy for metastatic bladder cancer. Despite the initial high response rate, the vast majority of patients eventually progress and succumb to their disease, urging the need for development of novel therapies.

AREAS COVERED IN THIS REVIEW

This article discusses the main signaling pathways implicated in the pathogenesis of bladder carcinomas, reviews recently completed and ongoing clinical trials, and anticipates the future direction of molecularly targeted agents.

WHAT THE READER WILL GAIN

This manuscript presents the current status of conventional chemotherapy in advanced bladder cancer, and provides a comprehensive review of molecular targeted agents currently in clinical development for this disease.

TAKE HOME MESSAGE

Improved understanding of the biology of urothelial carcinogenesis has paved the way for the development of novel molecularly targeted therapies, several of which are currently tested in clinical trials. In this regard, VEGF and EGFR pathways are emerging as important therapeutic targets for metastatic bladder cancer, either alone or in combination with conventional chemotherapeutics. Other therapies, including aurora kinase inhibitors, endothelin receptor antagonists, RAS/MAPK pathway inhibitors and novel immunologic strategies, may also prove helpful in the treatment of this disease.

Strategies for molecular expression profiling in bladder cancer

Carcinoma of the urinary bladder involves alterations in multiple cellular pathways that dictate the pathology of the disease and clinical outcome of the patient. This includes alterations in regulation of the cell cycle, apoptotic mechanisms, signal transduction and tumor angiogenesis. Interrogation of alterations in multiple molecules associated with these pathways is leading to the development of biomarker panels that are capable of predicting an individual patient's outcome or response to specific treatments. With respect to gene expression profiling, two broad approaches may be identified: a global approach and a pathway-specific approach. The global approach involves a high-throughput effort to profile the entire genome, while the pathway-specific approach quantifies select genes across several pathways. While the former has a high potential for discovery of novel signatures, the latter is important in generating reproducible and concise panels that have the potential for rapid clinical implementation. A combination of both these approaches is needed for the identification and validation of robust marker panels of potential clinical importance in bladder cancer.

Predicting recurrence and progression of noninvasive papillary bladder cancer at initial presentation based on quantitative gene expression profiles

BACKGROUND

Currently, tumor grade is the best predictor of outcome at first presentation of noninvasive papillary (Ta) bladder cancer. However, reliable predictors of Ta tumor recurrence and progression for individual patients, which could optimize treatment and follow-up schedules based on specific tumor biology, are yet to be identified.

OBJECTIVE

To identify genes predictive for recurrence and progression in Ta bladder cancer at first presentation using a quantitative, pathway-specific approach.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective study of patients with Ta G2/3 bladder tumors at initial presentation with three distinct clinical outcomes: absence of recurrence (n=16), recurrence without progression (n=16), and progression to carcinoma in situ or invasive disease (n=16).

MEASUREMENTS

Expressions of 24 genes that feature in relevant pathways that are deregulated in bladder cancer were quantified by real-time polymerase chain reaction on tumor biopsies from the patients at initial presentation.

RESULTS AND LIMITATIONS

CCND3 (p=0.003) and HRAS (p=0.01) were predictive for recurrence by univariate analysis. In a multivariable model based on CCND3 expression, sensitivity and specificity for recurrence were 97% and 63%, respectively. HRAS (p<0.001), E2F1 (p=0.017), BIRC5/Survivin (p=0.038), and VEGFR2 (p=0.047) were predictive for progression by univariate analysis. Multivariable analysis based on HRAS, VEGFR2, and VEGF identified progression with 81% sensitivity and 94% specificity. Since this is a small retrospective study using medium-throughput profiling, larger confirmatory studies are needed.

CONCLUSIONS

Gene expression profiling across relevant cancer pathways appears to be a promising approach for Ta bladder tumor outcome prediction at initial diagnosis. These results could help differentiate between patients who need aggressive versus expectant management.

Molecular pathogenesis and diagnostics of bladder cancer

Despite elaborate characterization of the risk factors, bladder cancer is still a major epidemiological problem whose incidence continues to rise each year. Urothelial carcinoma is now recognized as a disease of alterations in several cellular processes. The more prevalent, less aggressive, recurrent, noninvasive tumors are characterized by constitutive activation of the Ras-MAPK pathway. The less common but more aggressive invasive tumors, which have a higher mortality rate, are characterized by alterations in the p53 and retinoblastoma pathways. Several diagnostic tests have attempted to identify these molecular alterations in tumor cells exfoliated in the urine, whereas prognostic tests have tried to identify aberrations so as to predict tumor behavior and identify therapeutic targets. The future of bladder cancer patient management will rely on the use of molecular tests to reliably diagnose the presence of disease, predict individual tumor behavior, and suggest potential targeted therapeutics.

Molecular targets and targeted therapies in bladder cancer management

Bladder cancer remains a significant health problem. Currently, conventional histopathologic evaluation criteria (tumor grade and stage) are limited in their ability to accurately predict tumor behavior. A significant number of patients with muscle-invasive or extravesical disease treated by radical cystectomy alone die of metastasis. Intense research efforts are being made to better identify and categorize tumors by their molecular alterations and biological characteristics. A majority of the aggressive, invasive bladder carcinomas have alterations in the p53 and retinoblastoma pathways that regulate the cell cycle by interacting with signal transduction pathways. Angiogenesis further contributes to the neoplastic growth by providing a constant supply of oxygen and nutrients. It is becoming apparent that the accumulation of genetic and molecular changes ultimately determines a tumor's phenotype and subsequent clinical behavior. We provide a contemporary outline of our current understanding of the molecular and genetic events associated with tumorigenesis and progression. We emphasize the ways by which molecular biology is likely to affect the development of future therapies that will be able to target molecular alterations in individual tumors based on their respective profiles. The current status of targeted therapies for bladder cancer is also presented as well as the ongoing clinical trials.

p53 and retinoblastoma pathways in bladder cancer

A majority of the aggressive, invasive bladder carcinomas have alterations in the p53 and retinoblastoma genes and pathways. Examination of the alterations in the molecules in these pathways that regulate the cell cycle and their effects on the prognosis of bladder cancer are areas of active research. While defects in the p53-Mdm2-p14 axis have been implicated in urothelial cancer, perturbations in the cyclin-dependent kinases and their inhibitors have also been extensively studied in this context. Genetic alterations of the retinoblastoma gene and aberrant post-translational modifications of its protein have also been incriminated in invasive bladder cancer. This article reviews the individual prognostic roles of alterations in these molecules in the context of bladder cancer. Additionally, we review findings from recent studies that are attempting to analyze these markers in combination in an effort to construct molecular panels that can serve as more robust outcome predictors. More importantly, alterations in these molecules are now becoming enticing targets for novel therapeutics. We also review some of these agents that can restore the tumor cells' altered homeostatic mechanisms, thereby having potential in transitional cell carcinoma therapy. Future management of bladder cancer will employ validated marker panels for outcome prediction, and novel genetic and pharmacologic agents that will be able to target molecular alterations in individual tumors based on their respective profiles.

Sunitinib malate and sorafenib may be beneficial at the treatment of advanced bladder cancer due to their anti-angiogenic effects

Due to the poor prognosis of advanced bladder carcinoma and the insufficient affects of the chemotherapy agents for this disease, the investigation of the novel genetic and pharmacologic agents including anti-angiogenic agents that can target pathway-specific molecules has been the subject of several publications especially for the last 2 years. Although the clinical trials of these agents are still lacking, the experimental and the preliminary studies are giving hope for the future treatment of advanced bladder carcinoma. Sunitinib malate and sorafenib are the novel food and drug administration (FDA) approved anti-angiogenic agents, which have recently been demonstrated to improve the progression-free survival in patients with metastatic renal cell carcinoma. The main mechanism of these two drugs are defined as preventing the tumor growth by the inhibition of angiogenesis and the induction of apoptosis and necrosis via acting on different types of vascular endothelial growth factor (VEGF) such as the several agents which have been demonstrated to be beneficial for bladder carcinoma. According to this knowledge we suggest that these two new agents may also increase the progression-free survival of the patients with advanced bladder carcinoma due to their anti-angiogenic and tumor cell apoptotic effects. We believe that the evaluation of the effects of these agents on bladder cancer population by clinical, prospective and placebo controlled studies may prove our hypothesis and add critical findings to the literature which is still lacking.

Molecular Pathways in Invasive Bladder Cancer: New Insights Into Mechanisms, Progression, and Target Identification

Papillary and invasive cancers of the urinary bladder appear to evolve and progress through distinct molecular pathways. Invasion in bladder cancer forebodes a graver prognosis, and these tumors are generally characterized by alterations in the p53 and retinoblastoma (RB) pathways that normally regulate the cell cycle by interacting with the Ras–mitogen activated protein kinase signal transduction pathway. Tumor angiogenesis further contributes to the neoplastic growth by providing a constant supply of oxygen and nutrients. Distinct epigenetic and genetic events characterize the interplay between the molecules involved in these pathways, thus affording their use as indicators of prognosis. Efforts are now underway to construct molecular panels comprising multiple markers that can serve as more robust predictors of outcome. While clinical trials for targeted chemotherapy for bladder cancer have commenced, novel genetic and pharmacologic agents that can target pathway-specific molecules are currently under development. The next generation of clinical management for urothelial carcinoma will witness the use of multimarker panels for prognostic prediction and combination therapy directed at novel molecular targets for treatment.