Dual-track pathway of bladder carcinogenesis: practical implications

Loss of LPAR6 and CAB39L dysregulates the basal-to-luminal urothelial differentiation program, contributing to bladder carcinogenesis

We describe a strategy that combines histologic and molecular mapping that permits interrogation of the chronology of changes associated with cancer development on a whole-organ scale. Using this approach, we present the sequence of alterations around RB1 in the development of bladder cancer. We show that RB1 is not involved in initial expansion of the preneoplastic clone. Instead, we found a set of contiguous genes that we term "forerunner" genes whose silencing is associated with the development of plaque-like field effects initiating carcinogenesis. Specifically, we identified five candidate forerunner genes (ITM2B, LPAR6, MLNR, CAB39L, and ARL11) mapping near RB1. Two of these genes, LPAR6 and CAB39L, are preferentially downregulated in the luminal and basal subtypes of bladder cancer, respectively. Their loss of function dysregulates urothelial differentiation, sensitizing the urothelium to N-butyl-N-(4-hydroxybutyl)nitrosamine-induced cancers, which recapitulate the luminal and basal subtypes of human bladder cancer.

Integrative Single Cell Atlas Revealed Intratumoral Heterogeneity Generation from an Adaptive Epigenetic Cell State in Human Bladder Urothelial Carcinoma

Intratumor heterogeneity (ITH) of bladder cancer (BLCA) contributes to therapy resistance and immune evasion affecting clinical prognosis. The molecular and cellular mechanisms contributing to BLCA ITH generation remain elusive. It is found that a TM4SF1-positive cancer subpopulation (TPCS) can generate ITH in BLCA, evidenced by integrative single cell atlas analysis. Extensive profiling of the epigenome and transcriptome of all stages of BLCA revealed their evolutionary trajectories. Distinct ancestor cells gave rise to low-grade noninvasive and high-grade invasive BLCA. Epigenome reprograming led to transcriptional heterogeneity in BLCA. During early oncogenesis, epithelial-to-mesenchymal transition generated TPCS. TPCS has stem-cell-like properties and exhibited transcriptional plasticity, priming the development of transcriptionally heterogeneous descendent cell lineages. Moreover, TPCS prevalence in tumor is associated with advanced stage cancer and poor prognosis. The results of this study suggested that bladder cancer interacts with its environment by acquiring a stem cell-like epigenomic landscape, which might generate ITH without additional genetic diversification.

Molecular profile of bladder cancer progression to clinically aggressive subtypes

Bladder cancer is a histologically and clinically heterogenous disease. Most bladder cancers are urothelial carcinomas, which frequently develop distinct histological subtypes. Several urothelial carcinoma histological subtypes, such as micropapillary, plasmacytoid, small-cell carcinoma and sarcomatoid, show highly aggressive behaviour and pose unique challenges in diagnosis and treatment. Comprehensive genomic characterizations of the urothelial carcinoma subtypes have revealed that they probably arise from a precursor subset of conventional urothelial carcinomas that belong to different molecular subtypes - micropapillary and plasmacytoid subtypes develop along the luminal pathway, whereas small-cell and sarcomatoid subtypes evolve along the basal pathway. The subtypes exhibit distinct genomic alterations, but in most cases their biological properties seem to be primarily determined by specific gene expression profiles, including epithelial-mesenchymal transition, urothelial-to-neural lineage plasticity, and immune infiltration with distinct upregulation of immune regulatory genes. These breakthrough studies have transformed our view of bladder cancer histological subtype biology, generated new hypotheses for therapy and chemoresistance, and facilitated the discovery of new therapeutic targets.

Detecting Muscle Invasion of Bladder Cancer: An Application of Diffusion Kurtosis Imaging Ratio and Vesical Imaging-Reporting and Data System

BACKGROUND

Independent factors are needed to supplement vesical imaging-reporting and data system (VI-RADS) to improve its ability to identify muscle invasive bladder cancer (MIBC).

PURPOSE

To assess the correlation between MIBC and diffusion kurtosis imaging (DKI) ratio, VI-RADS, and other factors (such as tumor location).

STUDY TYPE

Retrospective.

POPULATION

Sixty-eight patients (50 males and 18 females; age: 70.1 ± 9.5 years) with bladder urothelial carcinoma.

FIELD STRENGTH/SEQUENCE

1.5 T, conventional diffusion-weighted imaging (DWI), and DKI (single shot echo-planar sequence).

ASSESSMENT

Three radiologists independently measured the diffusion parameters of each bladder cancer (BCa) and obturator internus, including the mean apparent diffusion coefficient (ADCmean), mean kurtosis (MK), and mean diffusion (MD). And the ratio of diffusion parameters between BCa and obturator internus was calculated (diffusion parameter ratio = bladder cancer:obturator internus). Based on the VI-RADS, the target lesions were independently scored. Furthermore, the actual tumor-wall contact length (ACTCL) and absolute tumor-wall contact length (ABTCL) were measured.

STATISTICAL TESTS

Multicollinearity among independent variables was evaluated using the variance inflation factor (VIF). Multivariable logistic regression analysis was used to determine the independent risk factors of MIBC. The receiver operating characteristic curve was used to evaluate the efficacy of each variable in detecting MIBC. The DeLong test was used to compare the area under the curve (AUC). A P < 0.05 was considered statistically significant.

RESULTS

MKratio (median: 0.62) and VI-RADS were independent risk factors for MIBC. AUCs for MKratio, VI-RADS, and MKratio combined with VI-RADS in assessing MIBC were 0.895, 0.871, and 0.973, respectively. MKratio combined with VI-RADS was more effective in diagnosing MIBC than VI-RADS alone.

DATA CONCLUSIONS

MKratio has potential to assist the assessment of MIBC. MKratio can be used as a supplement to VI-RADS for detecting MIBC.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY: Stage 2.

Molecular Taxonomy and Immune Checkpoint Therapy in Bladder Cancer

Bladder cancer is a heterogeneous disease, which exhibits a wide spectrum of clinical and pathologic features. Recent genomic studies have revealed that distinct molecular alterations may underlie the diverse clinical behaviors of bladder cancer, leading to a novel molecular classification. The intrinsic molecular subtypes exhibit distinct gene expression signatures and different clinicopathologic features. Genomic alterations also underlie the development of bladder cancer histologic subtypes. Genomic characterization provides new insights to understanding the biology of bladder cancer and improves the diagnosis and treatment of this complex disease. Biomarkers can aid the selection of patients for immune checkpoint therapy.

Assessment of Luminal and Basal Phenotypes in Bladder Cancer

Genomic profiling studies have demonstrated that bladder cancer can be divided into two molecular subtypes referred to as luminal and basal with distinct clinical behaviors and sensitivities to frontline chemotherapy. We analyzed the mRNA expressions of signature luminal and basal genes in bladder cancer tumor samples from publicly available and MD Anderson Cancer Center cohorts. We developed a quantitative classifier referred to as basal to luminal transition (BLT) score which identified the molecular subtypes of bladder cancer with 80–94% sensitivity and 83–93% specificity. In order to facilitate molecular subtyping of bladder cancer in primary care centers, we analyzed the protein expressions of signature luminal (GATA3) and basal (KRT5/6) markers by immunohistochemistry, which identified molecular subtypes in over 80% of the cases. In conclusion, we provide a tool for assessment of molecular subtypes of bladder cancer in routine clinical practice.

A novel tumor suppressing gene, ARHGAP9, is an independent prognostic biomarker for bladder cancer

Screening for genes or markers relevant to bladder cancer (BC) tumorigenesis and progression is of vital clinical significance. The present study used reverse-transcription quantitative PCR reaction assays to examine the expression of mRNA encoding Rho GTPase-activating protein 9 (ARHGAP9) in BC tissue samples and to determine whether ARHGAP9 is an independent prognostic biomarker for non-muscle invasive BC (NMIBC) and muscle invasive BC (MIBC). The results revealed that the downregulation of ARHGAP9 expression in the tissue of patients with NMIBC or MIBC was significantly associated with a poor prognosis. In patients with NMIBC, a high expression of ARHGAP9 was significantly associated with prolonged recurrence-free survival, whereas in MIBC patients, it was significantly associated with an increased progression-free and cancer-specific survival. The risk of cancer-specific death was 2.923 times higher (95% confidence interval, 1.192–7.163) when ARHGAP9 levels were decreased. In conclusion, lower expressions of ARHGAP9 correlated with BC prognosis, indicating that it may be a useful marker for guiding treatment application.

Preparation of allyl isothiocyanate nanoparticles, their anti-inflammatory activity towards RAW 264.7 macrophage cells and anti-proliferative effect on HT1376 bladder cancer cells

BACKGROUND

Allyl isothiocyanate (AITC), a volatile and water-insoluble compound present in several cruciferous vegetables, has been shown to possess several biological qualities such as anti-bacterial, anti-fungal, and anti-cancer activity. In this study, water-soluble allyl isothiocyanate nanoparticles (AITC-NPs) were prepared by oil dispersed in water (O/W) microemulsion and complex coacervation techniques and evaluated for their anti-inflammatory activity towards macrophage cell RAW 264.7 and anti-cancer effect on human bladder cancer cell HT1376.

RESULTS

The AITC-NPs with a particle size of 9.4 nm were stable during heating up to 110 °C or three freeze-thawing cycles. No significant cytotoxicity was shown on Caco-2 and intestine epithelial IEC-6 cells at AITC-NP doses ranging from 0.25 to 2 g L^-1 (8.75-70 mg L^-1 AITC). However, at 2 g L^-1 dosage, AITC-NPs could inhibit the growth of human bladder cancer cells HT1376 by 90%, while their low dosage at 0.25 g L^-1 could inhibit migration ability by 83.7, 71.3, 58.4 and 31.4% after 4, 8, 12, and 24 h of incubation, respectively. Compared to AITC and NPs, AITC-NPs showed a better inhibition on lipopolysaccharide (LPS)-induced TNF-α, IL-6, NO and iNOS production in RAW 264.7 macrophage cells.

CONCLUSION

The results demonstrate the potential of AITC-NPs as therapeutic agents for the treatment of bladder cancer and the enhancement of immune function. © 2018 Society of Chemical Industry.

Bladder Cancer in the Genomic Era

CONTEXT.—

Bladder cancer is a heterogeneous disease that exhibits a wide spectrum of clinical and pathologic features. The classification of bladder cancer has been traditionally based on morphologic assessment with the aid of immunohistochemistry. However, recent genomic studies have revealed that distinct alterations of DNA and RNA in bladder cancer may underlie its diverse clinicopathologic features, leading to a novel molecular classification of this common human cancer.

OBJECTIVE.—

To update recent developments in genomic characterization of bladder cancer, which may shed insights on the molecular mechanisms underlying the origin of bladder cancer, dual-track oncogenic pathways, intrinsic molecular subtyping, and development of histologic variants.

DATA SOURCES.—

Peer-reviewed literature retrieved from PubMed search and authors' own research.

CONCLUSIONS.—

Bladder cancer is likely to arise from different uroprogenitor cells through papillary/luminal and nonpapillary/basal tracks. The intrinsic molecular subtypes of bladder cancer referred to as luminal and basal exhibit distinct expression signatures, clinicopathologic features, and sensitivities to standard chemotherapy. Genomic characterization of bladder cancer provides new insights to understanding the biological nature of this complex disease, which may lead to more effective treatment.

Predicting the tumorigenic phenotype of human bladder cancer cells by combining with fetal rat mesenchyme

BACKGROUND

In nonmuscle invasive bladder cancer patients, prediction of pTa and pT1 bladder cancer recurrence and progression must be established. Micropapillary structures have been defined as small clusters of invasive cancer cells having features of the epithelial-mesenchymal transition. Since the stromal microenvironment helps to induce the epithelial-mesenchymal transition, interactions between cancer cells and stroma should be closely examined to predict the tumorigenic phenotype of human bladder cancer cells.

MATERIALS AND METHODS

To investigate differences in the responsiveness of cancer cells to stroma, we combined 3 established human bladder cancer cell lines (high-grade T24 and UM-UC-3 cells, and low-grade papillary RT4 cells) with fetal rat mesenchyme.

RESULTS

Among 3 bladder cancer cell lines, the expression profiles of p63 isoforms were distinct, i.e., p63γ in T24 cells, p63β in UM-UC-3 cells, and p63α in RT4 cells. Tumors formed by T24 cells combined with fetal mesenchyme formed micropapillary-like structures, whereas those formed by T24 cells alone did not. T24 cells combined with fetal mesenchyme showed poor differentiation, e.g., innumerable chromatic atypia in the nuclei, higher levels of chromatic condensation, and increased nucleoli. In contrast, both UM-UC-3 and RT4 cells combined with fetal mesenchyme did not form micropapillary-like structures. Ki-67 and p63 labeling indices were significantly elevated by combining fetal mesenchyme with T24 cells but not with the others.

CONCLUSIONS

By mixing cancer cells with fetal mesenchyme, our data demonstrated that formation of micropapillary-like structures may predict the tumorigenic phenotype of invasive bladder cancer cells. Taken together, distinct expression profiles of p63 isoforms may predict poor outcomes in invasive bladder cancer.

Mutational Analysis of the BRAF Gene in Transitional Cell Carcinoma of the Bladder

Purpose

Mutational activation of the MAP kinase pathway is frequently found in many types of cancer. Recently, activating mutations in the BRAF gene, an important activator of this pathway, have been described in several tumor types including melanoma, colorectal and papillary thyroid cancer. The most frequent mutation in exon 15 (V600E) as well as several other mutations within exons 11 and 15 result in constitutive activation of the oncoprotein.

Materials and methods

Our study aimed to investigate BRAF mutations in 30 human bladder tumors and their adjacent normal tissues. The V600E mutation was screened by PCR/RFLP and exons 11, 14 and 15 of BRAF including intron-exon boundaries were sequenced.

Results

We detected two tumor specimens bearing two different mutations, both of which were found in exon 15. One sample showed the T1799A (V600E) and the other the G1798T (V600L) mutation. The first specimen was stage pT1a and grade II, whereas the second was stage pT2b and grade III. No mutations within the coding region of exons 11, 14, 15 and the intron-exon junctions for the remaining samples were found.

Conclusions

Our results suggest that involvement of BRAF mutations in the development of transitional cell carcinoma of the bladder is infrequent.

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).

Noninvasive Papillary Basal-like Urothelial Carcinoma: A Subgroup of Urothelial Carcinomas With Immunohistochemical Features of Basal Urothelial Cells Associated With a High Rate of Recurrence and Progression

BACKGROUND

We investigated the clinical and pathologic significance of a subgroup of noninvasive papillary urothelial carcinomas (UCs) expressing reactivity to urothelial basal cell markers.

DESIGN

In total, 302 consecutive cases of noninvasive papillary UC were evaluated immunohistochemically with cytokeratin 5 (CK5)/CD44. Any UC that was reactive for greater than 25% thickness of the urothelium was designated as basal-like urothelial carcinoma (BUC); remaining UC cases were designated as non-BUC. The follow-up period was up to 3 years. Historical review of UC was extended for up to 3 retrospective years.

RESULTS

Among 302 noninvasive UC, BUC was identified in 33 of 256 (12.9%) low-grade UC and 8 of 46 (17%) high-grade UC (P=0.041). Immunoreactivity for CD44 was similar to that of CK5, but displayed weaker and more diffuse staining. CK20 was reactive in 9 cases, primarily high-grade BUC. Other basal cell markers (34bE12, p63, bcl2, and EP4) were found to be neither sensitive nor specific in detecting UC with high CK5 expression. In comparison with non-BUC, BUC was associated with increased multifocality, larger tumor size, higher recurrence rate, and more frequent upgrading and stage progression. In the follow-up period of 3 years, distant metastasis occurred in 6 cases of which 5 were in the BUC subgroup.

CONCLUSIONS

Our results showed that noninvasive papillary BUC represents a small subset associated with increased risk of tumor recurrence and progression. The aggressive behavior is likely associated with basal-like features of BUC, as seen in carcinomas with basal cell features in other body sites.

Insights from animal models of bladder cancer: recent advances, challenges, and opportunities

Bladder cancer (urothelial cancer of the bladder) is the most common malignancy affecting the urinary system with increasing incidence and mortality. Treatment of bladder cancer has not advanced in the past 30 years. Therefore, there is a crucial unmet need for novel therapies, especially for high grade/stage disease that can only be achieved by preclinical model systems that faithfully recapitulate the human disease. Animal models are essential elements in bladder cancer research to comprehensively study the multistep cascades of carcinogenesis, progression and metastasis. They allow for the investigation of premalignant phases of the disease that are not clinically encountered. They can be useful for identification of diagnostic and prognostic biomarkers for disease progression and for preclinical identification and validation of therapeutic targets/candidates, advancing translation of basic research to clinic. This review summarizes the latest advances in the currently available bladder cancer animal models, their translational potential, merits and demerits, and the prevalent tumor evaluation modalities. Thereby, findings from these model systems would provide valuable information that can help researchers and clinicians utilize the model that best answers their research questions.

Aurora Kinase A is a Biomarker for Bladder Cancer Detection and Contributes to its Aggressive Behavior

The effects of AURKA overexpression associated with poor clinical outcomes have been attributed to increased cell cycle progression and the development of genomic instability with aneuploidy. We used RNA interference to examine the effects of AURKA overexpression in human bladder cancer cells. Knockdown had minimal effects on cell proliferation but blocked tumor cell invasion. Whole genome mRNA expression profiling identified nicotinamide N-methyltransferase (NNMT) as a downstream target that was repressed by AURKA. Chromatin immunoprecipitation and NNMT promoter luciferase assays revealed that AURKA’s effects on NNMT were caused by PAX3-mediated transcriptional repression and overexpression of NNMT blocked tumor cell invasion in vitro. Overexpression of AURKA and activation of its downstream pathway was enriched in the basal subtype in primary human tumors and was associated with poor clinical outcomes. We also show that the FISH test for the AURKA gene copy number in urine yielded a specificity of 79.7% (95% confidence interval [CI] = 74.2% to 84.1%), and a sensitivity of 79.6% (95% CI = 74.2% to 84.1%) with an AUC of 0.901 (95% CI = 0.872 to 0.928; P < 0.001). These results implicate AURKA as an effective biomarker for bladder cancer detection as well as therapeutic target especially for its basal type.

Tumoral Versus Flat Intraepithelial Neoplasia of Pancreatobiliary Tract, Gallbladder, and Ampulla of Vater

Context.—The identification of a precursor lesion is important to understanding the histopathologic and genetic alterations in carcinogenesis. There are a plethora of terminologies that describe precursor lesions of the pancreatobiliary tract, ampulla of Vater, and gallbladder. The current terminologies for precursor lesions may make it difficult to understand the tumor biology. Here, we propose the concept of tumoral and flat intraepithelial neoplasia to improve our understanding of precursor lesions of many epithelial organs, including the pancreatobiliary tract, ampulla of Vater, and gallbladder.

Objective.—To understand the dichotomous pattern of tumoral and flat intraepithelial neoplasia in carcinogenesis of pancreatobiliary tract, ampulla of Vater, and gallbladder.

Data Sources.—Review of relevant literatures indexed in PubMed.

Conclusions.—Tumoral intraepithelial neoplasia presents as an intraluminal or intraductal, mass-forming, polypoid lesion or a macroscopic, visible, cystic lesion without intracystic papillae. Microscopically, tumoral intraepithelial neoplasia shows various proportions of papillary and tubular architecture, often with a mixed pattern, such as papillary, tubular, and papillary-tubular. The malignant potential depends on the degree of dysplasia and the cell phenotype of the epithelium. Flat intraepithelial neoplasia presents as a flat or superficial, spreading, mucosal lesion that is frequently accompanied by an invasive carcinoma. Tumoral and flat intraepithelial neoplasias are not homogeneous entities and may exhibit histopathologic spectrum changes and different genetic profiles. Although intraepithelial neoplasia showed a dichotomous pattern in the tumoral versus flat types, they can coexist. Tumoral and flat intraepithelial neoplasia can be interpreted as part of a spectrum of changes in the carcinogenesis pathway of each organ.

Gene Expression Profile of the Clinically Aggressive Micropapillary Variant of Bladder Cancer

BACKGROUND

Progression of conventional urothelial carcinoma of the bladder to a tumor with unique microscopic features referred to as micropapillary carcinoma is coupled with aggressive clinical behavior signified by a high propensity for metastasis to regional lymph nodes and distant organs resulting in shorter survival.

OBJECTIVE

To analyze the expression profile of micropapillary cancer and define its molecular features relevant to clinical behavior.

DESIGN, SETTING, AND PARTICIPANTS

We retrospectively identified 43 patients with micropapillary bladder cancers and a reference set of 89 patients with conventional urothelial carcinomas and performed whole-genome expression messenger RNA profiling.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The tumors were segregated into distinct groups according to hierarchical clustering analyses. They were also classified according to luminal, p53-like, and basal categories using a previously described algorithm. We applied Ingenuity Pathway Analysis software (Qiagen, Redwood City, CA, USA) and gene set enrichment analysis for pathway analyses. Cox proportional hazards models and Kaplan-Meier methods were used to assess the relationship between survival and molecular subtypes. The expression profile of micropapillary cancer was validated for selected markers by immunohistochemistry on parallel tissue microarrays.

RESULTS AND LIMITATIONS

We show that the striking features of micropapillary cancer are downregulation of miR-296 and activation of chromatin-remodeling complex RUVBL1. In contrast to conventional urothelial carcinomas that based on their expression can be equally divided into luminal and basal subtypes, micropapillary cancer is almost exclusively luminal, displaying enrichment of active peroxisome proliferator-activated receptor γ and suppression of p63 target genes. As with conventional luminal urothelial carcinomas, a subset of micropapillary cancers exhibit activation of wild-type p53 downstream genes and represent the most aggressive molecular subtype of the disease with the shortest survival. The involvement of miR-296 and RUVBL1 in the development of micropapillary bladder cancer was identified by the analyses of correlative associations of genome expression profiles and requires mechanistic validation.

CONCLUSIONS

Micropapillary cancer evolves through the luminal pathway and is characterized by the activation of miR-296 and RUVBL1 target genes.

PATIENT SUMMARY

Our observations have important implications for prognosis and for possible future development of more effective therapies for micropapillary bladder cancer.

Invasive urothelial carcinoma exhibiting basal cell immunohistochemical markers: A variant of urothelial carcinoma associated with aggressive features

We characterize invasive urothelial carcinoma (UC) exhibiting urothelial basal cell immunohistochemical markers. Consecutive invasive UCs were immunostained with CK20 and urothelial basal cell markers, cytokeratin 5 (CK5)/CD44. Immunostaining for CK5 and CD44 was scored as follows: positive for staining of more than 25% thickness of the epithelial nest or epithelium and low for lesser immunoreactivity. Invasive urothelial carcinoma (UC) exhibiting positive CK5/CD44 staining was designated as basal-like UC (BUC). In this study, of 251 invasive UC (pT1 in 57% and pT2-4 in 43%), BUC accounted for 40% of cases (accounting for most pT2-4 UC) and often presented as non-papillary UC without previous history of UC. In addition, BUC exhibited uniform nuclei with lesser degree of atypia than non BUC and decreased or negative cytokeratin 20 reactivity. Nested and microcystic variants of UC immunohistochemically stained as BUCs. Invasive non-BUCs were often papillary with marked cytologic atypia and pleomorphism, and accounted for most pT1 UC. The rates of perivesical invasion, lymph node and distant metastases were higher for BUC than non-BUC. All nine cases with absent/minimal residual in situ UC in 102 radical cystectomy specimens were from invasive non-BUC. BUC is distinguished from non-BUC due to this aggressive behavior, distinct immunohistochemical profile, and predominant non-papillary architecture. Our findings are consistent with recent studies identifying a subtype of muscle-invasive UC with molecular expression of basal cell and luminal cell molecular profiles. Our study further supports categorizing invasive UCs into these subtypes with different biological behaviors, possibly contributing to better therapeutic strategies.

eIF3a is over-expressed in urinary bladder cancer and influences its phenotype independent of translation initiation

PURPOSE

The eukaryotic translation initiation factor (eIF) 3a, the largest subunit of the eIF3 complex, is a key functional entity in ribosome establishment and translation initiation. In the past, aberrant eIF3a expression has been linked to the pathology of various cancer types but, so far, its expression has not been investigated in transitional cell carcinomas. Here, we investigated the impact of eIF3 expression on urinary bladder cancer (UBC) cell characteristics and UBC patient survival.

METHODS AND RESULTS

eIF3a expression was reduced through inducible knockdown in the UBC-derived cell lines RT112, T24, 5637 and HT1197. As a consequence of eIF3a down-regulation, UBC cell proliferation, clonogenic potential and motility were found to be decreased and, concordantly, UBC tumour cell growth rates were found to be impaired in xenotransplanted mice. Polysomal profiling revealed that reduced eIF3a levels increased the abundance of 80S ribosomes, rather than impairing translation initiation. Microarray-based gene expression and ontology analyses revealed broad effects of eIF3a knockdown on the transcriptome. Analysis of eIF3a expression in primary formalin-fixed paraffin embedded UBC samples of 198 patients revealed that eIF3a up-regulation corresponds to tumour grade and that high eIF3a expression corresponds to longer overall survival rates of patients with low grade tumours.

CONCLUSIONS

From our results we conclude that eIF3a expression may have a profound effect on the UBC phenotype and, in addition, may serve as a prognostic marker for low grade UBCs.

Current animal models of bladder cancer: Awareness of translatability (Review)

Experimental animal models are crucial in the study of biological behavior and pathological development of cancer, and evaluation of the efficacy of novel therapeutic or preventive agents. A variety of animal models that recapitulate human urothelial cell carcinoma have thus far been established and described, while models generated by novel techniques are emerging. At present a number of reviews on animal models of bladder cancer comprise the introduction of one type of method, as opposed to commenting on and comparing all classifications, with the merits of a certain method being explicit but the shortcomings not fully clarified. Thus the aim of the present study was to provide a summary of the currently available animal models of bladder cancer including transplantable (which could be divided into xenogeneic or syngeneic, heterotopic or orthotopic), carcinogen-induced and genetically engineered models in order to introduce their materials and methods and compare their merits as well as focus on the weaknesses, difficulties in operation, associated problems and translational potential of the respective models. Findings of these models would provide information for authors and clinicians to select an appropriate model or to judge relevant preclinical study findings. Pertinent detection methods are therefore briefly introduced and compared.

Significance of uroplakin III expression in recurrence of solitary muscle non-invasive bladder cancer

Numerous immunohistochemical biomarkers for patients with urothelial bladder cancer have been identified in order to predict their biological behavior. The aim of this present study was to examine the uroplakin III (UPIII) expression in homogenous group of non-muscle invasive bladder cancer and to correlate its value with clinico-pathological characteristics of patients and moreover with COX-2 expression and tumor infiltrating lymphocytes (TILs). Tumor specimens from 127 patients with non-muscle invasive bladder cancer, divided into two groups: patients who developed recurrent disease during the first five post-operative years (N=78) and patients without recurrent disease during a follow-up of minimum 5 years (N=49), were retrieved for tissue microarrays construction. On paraffin sections, the immunohistochemical analysis of UPIII expression was performed and staining was semiquantitatively evaluated. Expression of UPIII, including luminal, membranous and cytoplasmic one, was found in more than half of the tumors (57%). Specific staining pattern for UPIII was not associated with age and gender of patients, pathological grade, tumor size, disease stage or recurrence of disease. There was no association between UPIII, COX-2 and TILs, except for a negative moderate association between UP and COX-2 in the group of patients without recurrent tumor, and a strong association between UPIII and in the group with tumor recurrence. The present work gives an insight into the very complex mechanisms involved in tumor biology and progression. Moreover, it highlights the importance of further studies that should include multiple molecular markers in models designed to predict the outcome of non-muscle invasive bladder cancer.

Detection of bladder cancer using proteomic profiling of urine sediments

We used protein expression profiles to develop a classification rule for the detection and prognostic assessment of bladder cancer in voided urine samples. Using the Ciphergen PBS II ProteinChip Reader, we analyzed the protein profiles of 18 pairs of samples of bladder tumor and adjacent urothelium tissue, a training set of 85 voided urine samples (32 controls and 53 bladder cancer), and a blinded testing set of 68 voided urine samples (33 controls and 35 bladder cancer). Using t-tests, we identified 473 peaks showing significant differential expression across different categories of paired bladder tumor and adjacent urothelial samples compared to normal urothelium. Then the intensities of those 473 peaks were examined in a training set of voided urine samples. Using this approach, we identified 41 protein peaks that were differentially expressed in both sets of samples. The expression pattern of the 41 protein peaks was used to classify the voided urine samples as malignant or benign. This approach yielded a sensitivity and specificity of 59% and 90%, respectively, on the training set and 80% and 100%, respectively, on the testing set. The proteomic classification rule performed with similar accuracy in low- and high-grade bladder carcinomas. In addition, we used hierarchical clustering with all 473 protein peaks on 65 benign voided urine samples, 88 samples from patients with clinically evident bladder cancer, and 127 samples from patients with a history of bladder cancer to classify the samples into Cluster A or B. The tumors in Cluster B were characterized by clinically aggressive behavior with significantly shorter metastasis-free and disease-specific survival.

Inorganic arsenic in drinking water accelerates N-butyl-N-(4-hydroxybutyl)nitrosamine-induced bladder tissue damage in mice

Epidemiological studies have revealed that exposure to an arsenic-contaminated environment correlates with the incidence of bladder cancer. Bladder cancer is highly recurrent after intravesical therapy, and most of the deaths from this disease are due to invasive metastasis. In our present study, the role of inorganic arsenic in bladder carcinogenesis is characterized in a mouse model. This work provides the first evidence that inorganic arsenic in drinking water promotes N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced bladder tissue damage, including the urothelium and submucosal layer. This damage to the bladder epithelium induced by BBN includes thickening of the submucosal layer, the loss of the glycosaminoglycan layer and an increase in both the deoxyguanosine oxidation and cytosine methylation levels in the DNA. Further, when 10ppm inorganic arsenic is combined with BBN, the number of bladder submucosal capillaries is increased. In addition, inorganic arsenic also increases the deoxyguanosine oxidation level, alters the cytosine methylation state, decreases the activities of glutathione reductase and glucose-6-phosphate dehydrogenase, decreases the protein expression of NAD(P)H quinone oxidoreductase-1 (NQO-1) and increases the protein expression of specific protein 1 (Sp1) in bladder tissues. In summary, our data reveal that inorganic arsenic in drinking water promotes the BBN-induced pre-neoplastic damage of bladder tissue in mice, and that the 8-hydroxy-2'-deoxyguanosine, 5-methylcytosine, NQO-1 protein and Sp1 protein levels may be pre-neoplastic markers of bladder tumors.

Combretastatin A-4 inhibits cell growth and metastasis in bladder cancer cells and retards tumour growth in a murine orthotopic bladder tumour model

BACKGROUND AND PURPOSE

Bladder cancer is a highly recurrent cancer after intravesical therapy, so new drugs are needed to treat this cancer. Hence, we investigated the anti-cancer activity of combretastatin A-4 (CA-4), an anti-tubulin agent, in human bladder cancer cells and in a murine orthotopic bladder tumour model.

EXPERIMENTAL APPROACH

Cytotoxicity of CA-4 was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, propidium iodide (PI) staining assay and clonogenic survival assay. In vivo microtubule assembly assay, cell cycle analyses, Western blot and cell migration assay were used to study the mechanism of CA-4. The effect of intravesical CA-4 therapy on the development of tumours was studied in the murine orthotopic bladder tumour model.

KEY RESULTS

CA-4 inhibited microtubule polymerization in vivo. Cytotoxic IC(50) values of CA-4 in human bladder cancer cells were below 4 nM. Analyses of cell-cycle distribution showed CA-4 obviously induced G(2)-M phase arrest with sub-G(1) formation. The analyses of apoptosis showed that CA-4 induced caspase-3 activation and decreased BubR1 and Bub3 in cancer cells. In addition to apoptosis, CA-4 was also found to induce the formation of multinucleated cells. CA-4 had a significantly reduced cell migration in vitro. Importantly, the in vivo study revealed that intravesical CA-4 therapy retarded the development of murine bladder tumours.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that CA-4 kills bladder cancer cells by inducing apoptosis and mitotic catastrophe. It inhibited cell migration in vitro and tumour growth in vivo. Hence, CA-4 intravesical therapy could provide another strategy for treating superficial bladder cancers.

FGFR3 mutational status and protein expression in patients with bladder cancer in a Jordanian population

Bladder cancer accounts for nearly 5% of all newly diagnosed cancers in Jordan, with a much higher frequency in males. Recent studies have shown that activating mutations in FGFR3 are the most common findings in non-invasive low grade bladder tumors. In this study, we, retrospectively, investigated a cohort of 121 bladder cancer patients with various grades and stages of the tumor for molecular changes in FGFR3. Overexpression of FGFR3 was observed in 49%, 34%, 15%, and 2% of pTa, pT1, pT2, and pT3 cases, respectively. Further, FGFR3 expression was positive in 45%, 26%, and 30% of G1, G2 and G3 cases, respectively. Mutational analysis of exons 7, 10 and 15 of FGFR3 identified four previously reported mutations, namely R248C (n=4; 10%), S249C (n=23; 59%), Y375C (n=7; 18%), G382R (n=4; 10%), and one novel mutation, G382E (n=1; 3%). Our results indicate that both mutations and overexpression of FGFR3 are correlated together, and are more prevalent in early stage (pTa and pT1) and low grade (G1 and G2) bladder tumors. Survival analysis showed no contribution of changes in FGFR3 on the patient's survival. Multivariate Cox proportional hazards model analysis of overall survival for the following variables: age, gender, stage and grade of tumor, and FGFR3 (expression and mutation) revealed that age, stage and grade of tumor are independent predictors of overall survival in patients with bladder cancer. Our work is the first to address the molecular status of FGFR3 in Jordanian patients with bladder cancer, and provides further support for FGFR3 as a key player in the initiation of bladder tumors.

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

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

Biological similarities between murine chemical-induced and natural human bladder carcinogenesis

The present study investigated the similarities between rodent and human urothelial carcinogenesis models using DNA content, p53 and Ki-67 immunoexpression as surrogate markers of bladder carcinogenesis. Following N-butyl-N-(4-hydroxybutyl)-nitrosamine exposure, 49 human cystectomy specimens of bladder cancer and 53 rat bladder specimens were studied. All of the tumours and adjacent mucosa present in each specimen were evaluated. High similarities were observed between the rodent urothelium carcinogenesis process and the corresponding process in humans, in regards to the histopathological features and biological alteration profile: DNA aneuploidy, p53 overexpression and high proliferative index measured by Ki-67 immunoexpression. Despite these similarities, a higher frequency of alterations was observed in earlier stages in the rat chemical-induced carcinogenesis, namely in 5c aneuploid cells, p53 overexpression and higher Ki-67 labelling index. These results confirm that this experimental animal model is a suitable and reproducible model of bladder carcinogenesis, particularly in regards to high-risk non-invasive and invasive urothelial carcinomas. These features mandate its use in the identification of new molecular targets and evaluation of tumour response to new cytotoxic drugs or drug combinations in bladder cancer therapeutic intervention.

Activation of RAS family genes in urothelial carcinoma

PURPOSE

Bladder cancer is the fifth most common malignancy in men in Western society. We determined RAS codon 12 and 13 point mutations and evaluated mRNA expression levels in transitional cell carcinoma cases.

MATERIALS AND METHODS

Samples from 30 human bladder cancers and 30 normal tissues were analyzed by polymerase chain reaction/restriction fragment length polymorphism and direct sequencing to determine the occurrence of mutations in codons 12 and 13 of RAS family genes. Moreover, we used real-time reverse transcriptase-polymerase chain reaction to evaluate the expression profile of RAS genes in bladder cancer specimens compared to that in adjacent normal tissues.

RESULTS

Overall H-RAS mutations in codon 12 were observed in 9 tumor samples (30%). Two of the 9 patients (22%) had invasive bladder cancer and 7 (77%) had noninvasive bladder cancer. One H-RAS mutation (11%) was homozygous and the remaining 89% were heterozygous. All samples were WT for K and N-RAS oncogenes. Moreover, 23 of 30 samples (77%) showed over expression in at least 1 RAS family gene compared to adjacent normal tissue. K and N-RAS had the highest levels of over expression in bladder cancer specimens (50%), whereas 27% of transitional cell carcinomas demonstrated H-RAS over expression relative to paired normal tissues.

CONCLUSIONS

Our results underline the importance of H-RAS activation in human bladder cancer by codon 12 mutations. Moreover, they provide evidence that increased expression of all 3 RAS genes is a common event in bladder cancer that is associated with disease development.

Quantitation of Aurora kinase A gene copy number in urine sediments and bladder cancer detection

BACKGROUND

Chromosome missegregation and the resulting aneuploidy is a common change in neoplasia. The Aurora kinase A (AURKA) gene, which encodes a key regulator of mitosis, is frequently amplified and/or overexpressed in cancer cells, and the level of AURKA amplification is associated with the level of aneuploidy. We examined whether AURKA gene amplification is a biomarker for the detection of bladder cancer.

METHODS

The effect of ectopic expression of Aurora kinase A (AURKA) using an adenoviral vector in simian virus 40-immortalized urothelial cells (SV-HUC) on centrosome multiplication and chromosome copy number was measured in vitro by immunofluorescence and fluorescence in situ hybridization (FISH), respectively. The FISH test was also used to examine AURKA gene copy number in exfoliated cells in voided urine samples from 23 patients with bladder cancer and 7 healthy control subjects (training set), generating a model for bladder cancer detection that was subsequently validated in an independent set of voided urine samples from 100 bladder cancer patients and 148 control subjects (92 healthy individuals and 56 patients with benign urologic disorders). An AURKA gene score (the proportion of cells with three or more AURKA signals) was used to produce receiver operating characteristic (ROC) curves and to calculate the specificity and sensitivity of the AURKA FISH test. Differences between mean AURKA scores in different pathogenetic groups of bladder cancer stratified according to histological grade and stage were tested by unpaired Mann-Whitney t tests or one-way Wilcoxon tests. All statistical tests were two-sided.

RESULTS

Forced overexpression of AURKA in urothelial cells induced amplification of centrosomes, chromosome missegregation, and aneuploidy, and natural overexpression was detectable in in situ lesions from patients with bladder cancer. The FISH test for the AURKA gene copy number performed on the validation set yielded a specificity of 96.6% (95% confidence interval [CI] = 92.3% to 98.5%) and sensitivity of 87% (95% CI = 79.0% to 92.2%) and an area under the ROC curve of 0.939 (95% CI = 0.906 to 0.971; P < .001).

CONCLUSION

Overexpression of AURKA can cause aneuploidy in urothelial cells, and the AURKA gene copy number is a promising biomarker for detection of bladder cancer.

Understanding the development of human bladder cancer by using a whole-organ genomic mapping strategy

The search for the genomic sequences involved in human cancers can be greatly facilitated by maps of genomic imbalances identifying the involved chromosomal regions, particularly those that participate in the development of occult preneoplastic conditions that progress to clinically aggressive invasive cancer. The integration of such regions with human genome sequence variation may provide valuable clues about their overall structure and gene content. By extension, such knowledge may help us understand the underlying genetic components involved in the initiation and progression of these cancers. We describe the development of a genome-wide map of human bladder cancer that tracks its progression from in situ precursor conditions to invasive disease. Testing for allelic losses using a genome-wide panel of 787 microsatellite markers was performed on multiple DNA samples, extracted from the entire mucosal surface of the bladder and corresponding to normal urothelium, in situ preneoplastic lesions, and invasive carcinoma. Using this approach, we matched the clonal allelic losses in distinct chromosomal regions to specific phases of bladder neoplasia and produced a detailed genetic map of bladder cancer development. These analyses revealed three major waves of genetic changes associated with growth advantages of successive clones and reflecting a stepwise conversion of normal urothelial cells into cancer cells. The genetic changes map to six regions at 3q22-q24, 5q22-q31, 9q21-q22, 10q26, 13q14, and 17p13, which may represent critical hits driving the development of bladder cancer. Finally, we performed high-resolution mapping using single nucleotide polymorphism markers within one region on chromosome 13q14, containing the model tumor suppressor gene RB1, and defined a minimal deleted region associated with clonal expansion of in situ neoplasia. These analyses provided new insights on the involvement of several non-coding sequences mapping to the region and identified novel target genes, termed forerunner (FR) genes, involved in early phases of cancer development.

The origins of bladder cancer

Bladder cancer, arising from the transitional cells of the mucosal urothelium, may present as a noninvasive, papillary tumor protruding from the mucosal surface, or as a solid, nonpapillary tumor that invades the bladder wall and has a high propensity for metastasis. The nonpapillary tumors originate from in situ dysplasia. The most common environmental risk for bladder cancer is active smoking; occupational exposure to arsenic or other carcinogens is also a risk factor. A possible familial component to bladder cancer has been described. Conventional models of carcinogenesis suppose the existence of successive mutation events within a specific cell clone, enabling its eventual escape from regulation of cell division and maintenance of genomic integrity. Important new information has emerged from whole-organ mapping of the mucosal genome in bladders resected for invasive cancer (Majewski et al, Lab Invest; published online 5 May 2008). Mapping of genetic hits across the entire mucosa demonstrates genetic alterations in six chromosomal regions, not only in mucosal regions of evident dysplasia, but also in morphologically normal mucosa. These clonally expanded regions cover vast expanses of the bladder surface, as a 'first wave' of pre-neoplasia. Target genes in these regions are termed 'forerunner genes' (FR genes), based on the concept that these genes enable the initial clonal expansion of in situ urothelial neoplasia. Extensive further analysis of human populations with urothelial cancer implicates genetic polymorphisms in one of these genes, P2RY5, as being present in a familial cluster of cancers of multiple organs, and as imparting risk for development of bladder cancer in active smokers. P2RY5 is a gene encoded within intron 17 of RB1, a prototypic tumor suppressor gene whose expression is lost at a later stage of bladder carcinogenesis. Alterations of the FR gene status provide a novel opportunity to screen individuals at risk for the earliest stage of bladder pre-neoplasia and represent attractive targets for therapeutic and chemopreventive interventions. These findings support the hypothesis that bladder carcinogenesis is initiated by clonal expansion of genetically altered but histologically normal cells that cover broad expanses of the mucosa. Effort must now be given to identifying the biological function of these novel FR genes.

Basaloid squamous cell carcinoma arising in [corrected] the renal pelvis

Basaloid squamous cell carcinoma is an uncommon and highly aggressive variant that can occur anywhere squamous cancers occur. It is most often seen in the head and neck, the perianal region, and the female genital tract. It is extremely rare in the urinary system. In this article, we report the first known case of basaloid squamous cell carcinoma arising in the renal pelvis. Given the aggressive nature of this neoplasm, it should not be omitted from the differential diagnosis of neoplasms arising from the urothelium.

Clinical significance of urine heparanase in bladder cancer progression

Heparanase is an endo-beta-glucuronidase capable of cleaving heparan sulfate (HS), an activity implicated in tumor metastasis. Heparanase expression is upregulated in primary human tumors, correlating with reduced post operative survival and elevated microvessel density. An ELISA method was used to quantify heparanase in urine from 282 individuals. Urine was collected from healthy volunteers (n = 41), patients diagnosed with noncancerous pathologic disorders (n = 90), and bladder cancer patients (n = 92). Fifty-nine bladder carcinoma patients after transurethral resection (TUR) with no evidence of disease (NED) were also included. Heparanase levels were significantly elevated in urine from bladder cancer patients compared with healthy controls (P < .001) and with noncancerous urinary disorders (P < .05). Heparanase elevation strongly correlated with tumor grade (P < .001) and stage (P = .027). An optimal cutoff value of 154 pg/ml was determined. Of 199 individuals enrolled (59 patients after TUR and 24 patients with recurring disease were excluded), 65 had heparanase levels above 154 pg/ml. Only 3 of 65 (4.6%) were healthy individuals. In contrast, 52.3% (34 of 65) of individuals with heparanase levels above 154 pg/ml were bladder cancer patients. The results indicate that urine heparanase levels are elevated during bladder cancer progression, suggesting that the ELISA method may be applied for bladder cancer diagnosis.

Bladder cancer angiogenesis and metastasis--translation from murine model to clinical trial

In the majority of cases, death from bladder cancer results from metastatic disease. Understanding the closely linked mechanisms of invasion, metastasis and angiogenesis in bladder cancer has allowed us to develop new therapeutic strategies that harbor the promise of decisive improvements in patient survival. The essential link between cell based experiments and the translation of novel agents into human patients with bladder cancer is the animal model. With emphasis on the orthotopic xenograft model, this review outlines some key mechanisms relevant to angiogenesis and the development of metastasis in bladder cancer. We highlight especially pathways related to MMP-9, IL-8, VEGF and EGFR. Most commonly, expression patterns of these markers in patients have correlated to disease progression and patient survival, which has led to laboratory investigations of these markers and eventually novel targeted therapies that are translated back into the clinic by means of clinical trials. Although imperfect in their translatability into clinical efficacy, animal models remain a critical tool in bladder cancer research.

Persistent uroplakin expression in advanced urothelial carcinomas: implications in urothelial tumor progression and clinical outcome

As the terminal differentiation products of human urothelium, uroplakins (UPs) would be expected to diminish during urothelial tumorigenesis. Surprisingly, recent studies found UPs to be retained even by well-advanced urothelial carcinomas, suggesting that the loss of UPs does not strictly parallel urothelial transformation. Little is known, however, about whether the status of UPs is associated with a particular pathologic parameter, the tumor's biological behavior, or patient outcome. Here we assessed UP expression by immunohistochemistry on tissue arrays from 285 patients with bladder urothelial carcinomas or nontumor conditions. UPs were expressed in all 9 normal urothelial specimens, 63 of 74 (85%) patients with non-muscle-invasive urothelial carcinomas on transurethral resection, 104 of 202 (51.5%) patients who underwent radical cystectomy for advanced urothelial carcinomas, and 33 of 50 (66%) lymph node metastases. Normally associated with urothelial apical surface, UPs were localized aberrantly in tumors, including microluminal, basal-laminal, cytoplasmic, or uniform patterns. In non-muscle-invasive diseases, there was no association between UP expression and disease recurrence, progression, or mortality. In contrast, in invasive diseases, absent UP expression was significantly associated with advanced pathologic stage, lymph node metastases, disease recurrence, and bladder cancer-specific mortality (P = .042, P = .035, P = .023, and P = .022, respectively) in univariate analyses. Furthermore, UP status was independent of key cell-cycle regulators, including p53, pRb, p27, and cyclin D1, thus excluding a functional link between these 2 groups of proteins. Our data demonstrate for the first time that persistent UP expression is associated with a favorable clinical outcome and that UPs may be used as adjunct markers for predicting the prognoses of patients with invasive and metastatic bladder carcinomas. Our results also suggest that UP-positive and -negative carcinomas have different clonal origins or may be derived from different cancer stem cells.

Forerunner genes contiguous to RB1 contribute to the development of in situ neoplasia

We used human bladder cancer as a model system and the whole-organ histologic and genetic mapping strategy to identify clonal genetic hits associated with growth advantage, tracking the evolution of bladder cancer from intraurothelial precursor lesions. Six putative chromosomal regions critical for clonal expansion of intraurothelial neoplasia and development of bladder cancer were identified by using this approach. Focusing on one of the regions, which includes the model tumor suppressor RB1, we performed allelotyping of single-nucleotide polymorphic sites and identified a 1.34-Mb segment around RB1 characterized by a loss of polymorphism associated with the initial expansion of in situ neoplasia. This segment contains several positional candidate genes referred to by us as forerunner genes that may contribute to such expansion. We subsequently concentrated our efforts on the two neighbor genes flanking RB1, namely ITM2B and CHC1L, as well as P2RY5, which is located inside RB1. Here, we report that ITM2B and P2RY5 modulated cell survival and were silenced by methylation or point mutations, respectively, and thus by functional loss may contribute to the growth advantage of neoplasia. We also show that homozygous inactivation of P2RY5 was antecedent to the loss of RB1 during tumor development, and that nucleotide substitutions in P2RY5 represent a cancer predisposing factor.