Transcriptional activation of H-ras, K-ras and N-ras proto-oncogenes in human bladder tumors

Conformational fluidity of intrinsically disordered proteins in crowded environment: a molecular dynamics simulation study

The class of intrinsically disordered proteins lacks stable three-dimensional structures. Their flexibility allows them to engage in a wide variety of interactions with other biomolecules thus making them biologically relevant and efficient. The intrinsic disorders of these proteins, which undergo binding-induced folding, allow alterations in their topologies while conserving their binding sites. Due to the lack of well-defined three-dimensional structures in the absence of their physiological partners, the folding and the conformational dynamics of these proteins remained poorly understood. Particularly, it is unclear how these proteins exist in the crowded intracellular milieu. In the present study, molecular dynamic simulations of two intrinsically unstructured proteins and two controls (folded proteins) were conducted in the presence and absence of molecular crowders to obtain an in-depth insight into their conformational flexibility. The present study revealed that polymer crowders stabilize the disordered proteins through enthalpic as well as entropic effects that are significantly more than their monomeric counterpart. Taken together, the study delves deep into crowding effects on intrinsically disordered proteins and provides insights into how molecular crowders induce a significantly diverse ensemble of dynamic scaffolds needed to carry out diverse functions.Communicated by Ramaswamy H. Sarma.

MyD88 Signaling Accompanied by Microbiota Changes Supports Urinary Bladder Carcinogenesis

Urinary bladder cancer (BC) inflicts a significant impairment of life quality and poses a high mortality risk. Schistosoma haematobium infection can cause BC, and the urinary microbiota of BC patients differs from healthy controls. Importantly, intravesical instillation of the bacterium Bacillus Calmette-Guerin stands as the foremost therapy for non-muscle invasive BC. Hence, studying the receptors and signaling molecules orchestrating bacterial recognition and the cellular response in the context of BC is of paramount importance. Thus, we challenged Toll-like receptor 4 (Tlr4) and myeloid differentiation factor 88 (Myd88) knock-out (KO) mice with N-butyl-N-(4-hydroxylbutyl)-nitrosamine (BBN), a well-known urinary bladder carcinogen. Gut microbiota, gene expression, and urinary bladder pathology were followed. Acute exposure to BBN did not reveal a difference in bladder pathology despite differences in the animal's ability to recognize and react to bacteria. However, chronic treatment resulted in reduced cancer invasiveness among Myd88KO mice while the absence of functional Tlr4 did not influence BC development or progression. These differences correlate with a heightened abundance of the Faecalibaculum genus and the lowest microbial diversity observed among Myd88KO mice. The presented data underscore the important role of microbiota composition and MyD88-mediated signaling during bladder carcinogenesis.

G-quadruplexes in cancer-related gene promoters: from identification to therapeutic targeting

INTRODUCTION

Guanine-rich DNA sequences can fold into four-stranded noncanonical secondary structures called G-quadruplexes (G4s) which are widely distributed in functional regions of the human genome, such as telomeres and gene promoter regions. Compelling evidence suggests their involvement in key genome functions such as gene expression and genome stability. Notably, the abundance of G4-forming sequences near transcription start sites suggests their potential involvement in regulating oncogenes.

AREAS COVERED

This review provides an overview of current knowledge on G4s in human oncogene promoters. The most representative G4-binding ligands have also been documented. The objective of this work is to present a comprehensive overview of the most promising targets for the development of novel and highly specific anticancer drugs capable of selectively impacting the expression of individual or a limited number of genes.

EXPERT OPINION

Modulation of G4 formation by specific ligands has been proposed as a powerful new tool to treat cancer through the control of oncogene expression. Actually, most of G4-binding small molecules seem to simultaneously target a range of gene promoter G4s, potentially influencing several critical driver genes in cancer, thus producing significant therapeutic benefits.

Targeted Long-Read Sequencing Decodes the Transcriptional Atlas of the Founding RAS Gene Family Members

The complicity of human RAS proteins in cancer is a well-documented fact, both due to the mutational hyperactivation of these GTPases and the overexpression of the genes encoding these proteins. Thus, it can be easily assumed that the study of RAS genes at the transcriptional and post-transcriptional level is of the utmost importance. Although previous research has shed some light on the basic mechanisms by which GTPases are involved in tumorigenesis, limited information is known regarding the transcriptional profile of the genes encoding these proteins. The present study highlights for the first time the wide spectrum of the mRNAs generated by the three most significant RAS genes (KRAS, NRAS and HRAS), providing an in-depth analysis of the splicing events and exon/intron boundaries. The implementation of a versatile, targeted nanopore-sequencing approach led to the identification of 39 novel RAS mRNA transcript variants and to the elucidation of their expression profiles in a broad panel of human cell lines. Although the present work unveiled multiple hidden aspects of the RAS gene family, further study is required to unravel the biological function of all the novel alternative transcript variants, as well as the putative protein isoforms.

Promoter hypomethylation as potential confounder of Ras gene overexpression and their clinical significance in subsets of urothelial carcinoma of bladder

Overexpression of normal Ras and its aberrant CpG island methylation in the promoter regions have been shown to direct cells for uncontrolled abnormal growth and bladder tumor formation and therefore, fetched recent attention as a marker of diagnosis and prognosis to predict the biological behavior of urothelial carcinoma of bladder (UCB). Methylation pattern at CpG islands of the promoter regions of rat sarcoma (Ras) gene homologues namely Kristen-Ras (K-Ras), Harvey (H-Ras), and Neuroblastoma (N-Ras) were examined by methylation specific polymerase chain reaction (MSP). Real time-quantitative polymerase chain reaction (RT-qPCR) was done to determine transcriptomic expressions of these Ras isoforms in the prospective series of 42 NMIBC (non-muscle invasive bladder cancer) and 45 MIBC (muscle invasive bladder cancer) biopsies. CpG loci in H-Ras and K-Ras were observed to be more hypomethylated in MIBC, whereas more hypomethylation in N-Ras was noted in NMIBC. Strong association of hypomethylation index with tumor stage, grade, type and size validate them it as marker of diagnosis in UCB patients. Differential overexpression of H-Ras, N-Ras and K-Ras genes in NMIBC and MIBC and their association with patients' demographics identify them as important diagnostic markers in pathogenesis of UCB. Given the reported ability of promoter hypomethylation to activate Ras expression, correlation studies examined positive significant association between hypomethylation index and expression. Study concludes that promoter hypomethylation of N-Ras and K-Ras could be a potential confounder of their increased expression in NMIBC. Biological significance of simultaneous presence of higher expression and promoter hypomethylation of Ras gene isoforms in MIBC is difficult to resolve in a given cohort of patients.

Design, Synthesis, and Evaluation of Novel p-(Methylthio)styryl Substituted Quindoline Derivatives as Neuroblastoma RAS (NRAS) Repressors via Specific Stabilizing the RNA G-Quadruplex

The human proto-oncogene neuroblastoma RAS ( NRAS) contains a guanine-rich sequence in the 5'-untranslated regions (5'-UTR) of the mRNA that could form an RNA G-quadruplex structure. This structure acts as a repressor for NRAS translation and could be a potential target for anticancer drugs. Our previous studies found an effective scaffold, the quindoline scaffold, for binding and stabilizing the DNA G-quadruplex structures. Here, on the basis of the previous studies and reported RNA-specific probes, a series of novel p-(methylthio)styryl substituted quindoline (MSQ) derivatives were designed, synthesized, and evaluated as NRAS RNA G-quadruplex ligands. Panels of experiments turned out that the introduction of p-(methylthio)styryl side chain could enhance the specific binding to the NRAS RNA G-quadruplex. One of the hits, 4a-10, showed strong stabilizing activity on the G-quadruplex and subsequently repressed NRAS's translation and inhibited tumor cells proliferation. Our finding provided a novel strategy to discover novel NRAS repressors by specifically binding to the RNA G-quadruplex in the 5'-UTR of mRNA.

Pseudogenes in gastric cancer pathogenesis: a review article

Cancer burden rises globally at an alarming pace. According to GLOBOCAN 2012, gastric cancer (GC) is regarded as the fifth most common malignancy in the world. Being twice as high in men as in women, GC is the third leading cause of cancer mortality in both sexes globally. Being labeled as 'junk DNA', pseudogenes were considered as nonfunctional 'trash', which contribute nothing to survival of the organism; therefore, a number of strategies have been developed to circumvent their accidental detection. Recent progresses have confirmed that pseudogenes can have broad and multifaceted spectrum of activities in human cancers in general and GC in particular. Furthermore, the mentioned functions are parental gene-dependent and/or -independent. Therefore, pseudogenes can be regarded as the emerging class of elaborate modulators of gene expression involved in pathogenesis of human cancers including gastric adenocarcinoma.

K-Ras, H-Ras, N-Ras and B-Raf mutation and expression analysis in Wilms tumors: association with tumor growth

Nephroblastoma (Wilms tumor) is a kidney neoplasia, predominately occurring at very young age, resulting from the malignant transformation of renal stem cells. The Ras proto-oncogenes and B-Raf are members of an intracellular cascade pathway, which regulates cell growth and differentiation, and ultimately cancer development. Our objective was to determine the mutation rate and to measure the mRNA levels of the three Ras genes and of B-Raf in formalin-fixed paraffin-embedded tissue samples from 32 patients with nephroblastoma and 10 controls. No mutations were detected in the four studied genes among our Wilms tumors cases, while Ras and B-Raf expression was higher in malignant samples versus controls. Statistical analysis revealed a positive correlation of K-Ras (p < 0.001) and B-Raf (p = 0.006) with tumor size, a negative correlation of K-Ras (p = 0.041) and H-Ras (p = 0.033) with the percentage of tissue necrosis, and an association of N-Ras (p = 0.047) and B-Raf (p = 0.044) with tissue histology. From the above, we deduce that although Ras and B-Raf mutations are rare events in Wilms tumors, their expression pattern suggests that they play an important role in the development and progression of this malignancy.

Incorporating VEGF-targeted therapy in advanced urothelial cancer

Patients with relapsed or refractory urothelial carcinoma (UC) have poor prognosis coupled with few options for systemic treatment. The role of angiogenesis in the evolution of cancers has been established, and studies have shown that it plays a key role in the pathogenesis of UC. Many targeted agents have been used in phase I-II trials for the treatment of UC, with encouraging but modest results. Recently, studies combining angiogenesis inhibitors with other chemotherapeutic agents were able to achieve objective responses higher than most commonly used second-line therapies in UC. Future efforts in investigating these therapies in UC rely on identification of biomarkers and other predictors of response to anti-VEGF therapy.

Nucleic Acid Targeted Therapy: G4 Oligonucleotides Downregulate HRAS in Bladder Cancer Cells through a Decoy Mechanism

In a previous study we have demonstrated that two neighboring G-quadruplexes, hras-1 and hras-2, located immediately upstream of the major transcription start site of HRAS, bind MAZ, a nuclear factor that activates transcription (Cogoi, S.; et al. Nucl. Acid Res. 2014, 42, 8379). For the present study we have designed G4 oligonucleotides with anthraquinone insertions and locked nucleic acids (LNA) modifications mimicking quadruplex hras-1. Luciferase, qRT-PCR, and Western blot data demonstrate that these constructs efficiently down regulate HRAS in T24 bladder cancer cells. The inhibitory efficiency of the G4 oligonucleotides correlates with their nuclease resistance in the cell environment. By chromatin immunoprecipitation we show that the association of MAZ to the HRAS promoter is strongly attenuated by the designed G4 oligonucleotides, thus suggesting that these constructs behave with a decoy mechanism.

Biomarkers for predicting response to tyrosine kinase inhibitors in drug-sensitive and drug-resistant human bladder cancer cells

The epidermal growth factor receptor (EGFR) family is reportedly overexpressed in bladder cancer, and tyrosine kinase inhibitors (TKIs) have been suggested as treatment. Gefitinib (Iressa®) is a selective inhibitor of the EGFR and lapatinib is a dual inhibitor of both the EGFR and HER2 (human EGFR type 2 receptor). Both compounds compete with the binding of ATP to the tyrosine kinase domain of the respective receptors to inhibit receptor autophosphorylation causing suppression of signal transduction. Unfortunately, resistance to these inhibitors is a major clinical issue. The purpose of the present study was to use protein array analysis to compare the signaling pathway(s) induced by gefitinib and lapatinib, in UM-UC-5 (drug-sensitive) and UM-UC-14 (drug-resistant) bladder cancer cells and to identify molecular markers that may be useful predictors of their efficacy. The results revealed that phosphorylation of EGFR, HER3, Met and ERK1/2 was markedly overexpressed in the sensitive cell line (UM-UC-5) and was strongly inhibited by the TKIs. Other notable differences included decreased phosphorylation of RSK, GSK3, AMPK, Akt and c-Jun by TKIs in the sensitive cells. In contrast, phosphorylated p53 was highly expressed in the resistant cell line (UM-UC-14) and TKIs had no effect in the resistant cells. Overall results suggest that phosphorylated HER3, ERK1/2 and p53 may be used as biomarkers to determine the sensitivity of bladder cancers to TKIs. In particular, a combination of these markers may be more likely to predict the sensitivity to TKIs.

HRAS is silenced by two neighboring G-quadruplexes and activated by MAZ, a zinc-finger transcription factor with DNA unfolding property

The HRAS promoter contains immediately upstream of the transcription start site two neighboring G-elements, each capable of folding into a G-quadruplex structure. We have previously found that these G-quadruplexes bind to the zinc-finger transcription factors MAZ and Sp1. In the present study we have examined the interaction between the HRAS promoter and MAZ, demonstrating for the first time that the protein unfolds the G-quadruplex structures. We also demonstrate that MAZ-GST, in the presence of the complementary strands, promotes a rapid transformation of the two HRAS quadruplexes into duplexes. By a mutational analysis of the HRAS G-elements, we dissected the MAZ-binding sites from the quadruplex-forming motifs, finding that the two neighboring G-quadruplexes bring about a dramatic repression of transcription, in a synergistic manner. We also discovered that the two G-quadruplexes are strong targets for small anticancer molecules. We found that a cell-penetrating anthratiophenedione (ATPD-1), which binds tightly to the G-quadruplexes (ΔT > 15°C), promotes the total extinction of HRAS transcription. In contrast, when one of the two G-quadruplexes was abrogated by point mutations, ATPD-1 repressed transcription by only 50%. Our study provides relevant information for the rationale design of targeted therapy drugs specific for the HRAS oncogene.

Investigation of the pharmacological profiles of dinuclear metal complexes as novel, potent and selective cytotoxic agents against ras-transformed cells

Around the world scientists try to design successful cures against still incurable diseases, especially cancers. New targets for prevention and new agents for therapy need to be identified. We synthesized novel metal complexes [Au(L1)(L2)Pt]Cl2 and [Ru(L1)2(L2)Pt]Cl2 for determining their cytotoxic and apoptotic effects. The complexes are synthesized by using 1,8-diaminonaphthalene (L1), and bis-1,4-di[([1,10]phenanthroline-5-il)aminomethyl]cyclohexane (L2) as ligands. This is the first study to examine these metals and these molecules in cancer treatment. We elucidated the effects of test compounds with embryonic rat fibroblast-like cells (F2408) and H-ras oncogene activated embryonic rat fibroblast-like cancer cells (5RP7). Results showed that our complexes are more effective than cisplatin to kill ras-transformed cells. Although the [Au(L1)(L2)Pt]Cl2 compound showed a cytotoxic potency higher than [Ru(L1)2(L2)Pt]Cl2 against cancer cells, it proved to be almost five times less effective in decreasing cell viability over healthy cells. Au(III) compound selectively targets the cancer cells but not the healthy cells.

Mismatch repair hMSH2, hMLH1, hMSH6 and hPMS2 mRNA expression profiles in precancerous and cancerous urothelium

Changes in the expression of the mismatch repair (MMR) genes hMSH2, hMLH1, hMSH6 and hPMS2 reflect dysfunction of the DNA repair system that may allow the malignant transformation of tissue cells. The aim of the present study was to address the mRNA expression profiles of the mismatch DNA repair system in cancerous and precancerous urothelium. This is the first study to quantify MMR mRNA expression by applying quantitative real-time PCR (qPCR) and translate the results to mRNA phenotypic profiles (r, reduced; R, regular or elevated) in bladder tumors [24 urothelial cell carcinomas (UCCs) and 1 papillary urothelial neoplasm of low malignant potential (PUNLMP)] paired with their adjacent normal tissues (ANTs). Genetic instability analysis was applied at polymorphic sites distal or close to the hMSH2 and hMLH1 locus. Presenting our data, reduced hMSH2, hMSH6 and hPMS2 mRNA expression profiles were observed in cancerous and precancerous urothelia. Significantly, the ANTs of UCCs revealed the highest percentages of reduced hMSH2 (r(2)), hMSH6 (r(6)) and hPMS2 (p(2)) mRNA phenotypes relative to their tumors (P<0.03). In particular, combined r(2)r(6) (P<0.02) presented a greater difference between ANTs of low-grade UCCs vs. their tumors compared with ANTs of high-grade UCCs (P= 0.000). Reduced hMLH1 (r(1)) phenotype was not expressed in precancerous or cancerous urothelia. The hMSH6 mRNA was the most changed in UCCs (47.8%), while hMSH2, hMLH1 and hPMS2 showed overexpression (47.8, 35 and 30%, respectively) that was associated with gender and histological tumor grading or staging. Genetic instability was rare in polymorphic regions distal to hMLH1. Our data reveal a previously unrecognized hMSH2 and hMSH6 mRNA combined phenotype (r(2)r(6)) correlated with a precancerous urothelium and show that hMLH1 is transcriptionally activated in precancerous or cancerous urothelium. In the present study, it is demonstrated that reduction of hMSH6 mRNA is a frequent event in bladder tumorigenesis and reflects a common mechanism of suppression with hMSH2, while alterations of hMSH2 or hMLH1 mRNA expression in UCCs does not correlate with the allelic imbalance of polymorphic regions harboring the genes.

G4-DNA formation in the HRAS promoter and rational design of decoy oligonucleotides for cancer therapy

HRAS is a proto-oncogene involved in the tumorigenesis of urinary bladder cancer. In the HRAS promoter we identified two G-rich elements, hras-1 and hras-2, that fold, respectively, into an antiparallel and a parallel quadruplex (qhras-1, qhras-2). When we introduced in sequence hras-1 or hras-2 two point mutations that block quadruplex formation, transcription increased 5-fold, but when we stabilized the G-quadruplexes by guanidinium phthalocyanines, transcription decreased to 20% of control. By ChIP we found that sequence hras-1 is bound only by MAZ, while hras-2 is bound by MAZ and Sp1: two transcription factors recognizing guanine boxes. We also discovered by EMSA that recombinant MAZ-GST binds to both HRAS quadruplexes, while Sp1-GST only binds to qhras-1. The over-expression of MAZ and Sp1 synergistically activates HRAS transcription, while silencing each gene by RNAi results in a strong down-regulation of transcription. All these data indicate that the HRAS G-quadruplexes behave as transcription repressors. Finally, we designed decoy oligonucleotides mimicking the HRAS quadruplexes, bearing (R)-1-O-[4-(1-Pyrenylethynyl) phenylmethyl] glycerol and LNA modifications to increase their stability and nuclease resistance (G4-decoys). The G4-decoys repressed HRAS transcription and caused a strong antiproliferative effect, mediated by apoptosis, in T24 bladder cancer cells where HRAS is mutated.

Ras mutation cooperates with β-catenin activation to drive bladder tumourigenesis

Mutations in the Ras family of proteins (predominantly in H-Ras) occur in approximately 40% of urothelial cell carcinoma (UCC). However, relatively little is known about subsequent mutations/pathway alterations that allow tumour progression. Indeed, expressing mutant H-Ras within the mouse bladder does not lead to tumour formation, unless this is expressed at high levels. The Wnt signalling pathway is deregulated in approximately 25% of UCC, so we examined if this correlated with the activation of MAPK signalling in human UCC and found a significant correlation. To test the functional significance of this association we examined the impact of combining Ras mutation (H-Ras(Q61L) or K-Ras(G12D)) with an activating β-catenin mutation within the mouse bladder using Cre-LoxP technology. Although alone, neither Ras mutation nor β-catenin activation led to UCC (within 12 months), mice carrying both mutations rapidly developed UCC. Mechanistically this was associated with reduced levels of p21 with dependence on the MAPK signalling pathway. Moreover, tumours from these mice were sensitive to MEK inhibition. Importantly, in human UCC there was a negative correlation between levels of p-ERK and p21 suggesting that p21 accumulation may block tumour progression following Ras mutation. Taken together these data definitively show Ras pathway activation strongly cooperates with Wnt signalling to drive UCC in vivo.

Stimulatory effects of the multi-kinase inhibitor sorafenib on human bladder cancer cells

BACKGROUND AND PURPOSE

Sorafenib is an inhibitor of several intracellular signalling kinases with anti-proliferative, anti-angiogenic and pro-apoptotic effects in tumour cells. Sorafenib is used in the therapy of advanced renal cell carcinoma, and several phase II clinical trials are being carried out in patients with urothelial carcinomas.

EXPERIMENTAL APPROACH

Using a panel of human bladder cancer cell lines (RT4, T24, J82), we characterized systematically the effects of sorafenib on intracellular signalling, migration, proliferation and apoptosis.

KEY RESULTS

We demonstrated that at low concentrations (<1 microM), sorafenib is capable of significantly stimulating migration and proliferation of the bladder cancer cells. We hypothesize that these stimulatory effects on tumour cell functions might be explained by an activation of the Ras/ERK-1/2 signal transduction pathway. In addition, the comparison of different bladder cancer cell lines not only revealed a different biology (e.g. cell migration), but also a differential susceptibility to the anti-apoptotic effects of sorafenib. Finally, we confirmed in different bladder cancer cell lines the known inhibitory actions of sorafenib in pharmacological concentrations (> or =3 microM) on ERK-1/2 phosphorylation, migration and proliferation, as well as the pro-apoptotic effects of the compound.

CONCLUSIONS AND IMPLICATIONS

Taken together, these findings suggest that although sorafenib has the potential to be used in the treatment of urothelial carcinoma, this compound might also activate bladder cancer cells at low concentrations. This should be relevant for dosing regiments to optimize the treatment with this promising anti-tumour drug.

Inhibitory effect of flavonoids on mutant H-Rasp protein

Mutant form of H-Ras (Harvey-Ras) proteins are found in almost 10%-25% of human tumours. Mutational activation transforms it into an oncogenic form, which results in the loss of intrinsic GTPase function and therefore the protein is constitutively in the active, GTP-bound state and is continuously sending signals for cell growth and proliferation. In the present insilico study, the inhibitory effect of different flavonoid compounds on mutant H Ras protein p21 has been assessed. In addition, inhibitory effect of flavonoids is compared with 3 known anticancer drugs. Upon docking, it was found that flavonoids such as Naringenin, Daidzein, and Hesperetin showed highest affinity (most negative ΔG), while Rutin showed no affinity towards mutant H Ras. The 3 clinical anticancer agents (Erlotinib, Letrozole and Exemestane) showed binding energies in the range of -1.11 to -5.51 kcal/mol which is comparatively lower than the flavonoids indicating efficacy of flavonoids in the treatment of cancer with little or no cytotoxicity. Our study demonstrates that flavonoids (particularly Naringenin, Daidzein, and Hesperetin) are the effective drugs to inhibit function of mutant H-Ras P21 protein, which in turn arrests the process of cell growth and proliferation of the cancer cell.

Bladder cancer: modeling and translation

Transitional cell carcinoma of the bladder is a common malignancy worldwide that is associated with significant morbidity and mortality. Although superficial tumors can often be treated effectively, invasive cancers not only require invasive surgery, but are also refractory to aggressive chemotherapy and radiotherapy. In this issue of Genes & Development, Puzio-Kuter and colleagues (pp. 675-680) describe an elegant genetically engineered murine model of bladder cancer that recapitulates many of the cardinal features of the human disease. The development of such models together with the application of new approaches to enumerate the complement of genetic alterations in bladder will provide new insights into the molecular nature of this disease. Moreover, the anatomy of this urinary malignancy provides a unique opportunity for innovative translational studies.

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.

Gene expression profiling of chemically induced rat bladder tumors

A variety of genetic alterations and gene expression changes are involved in the pathogenesis of bladder tumors. To explore expression changes in 4-hydroxybutyl(butyl)nitrosamine-induced rat bladder tumors, microarray analysis was performed. Analysis yielded 1,138 known genes and 867 expressed sequence tags that were changed when comparing tumors to normal rat epithelia. Altered genes included cell cycle-related genes, EGFR-Ras signaling genes, apoptosis genes, growth factors, and oncogenes. Using the pathway visualization tool GenMAPP, we found that these genes can be grouped along several pathways that control apoptosis, cell cycle, and integrin-mediated cell adhesion. When comparing current data with previous mouse bladder tumor data, we found that > 280 of the same known genes were differentially expressed in both mouse and rat bladder tumors, including cell cycle-related genes, small G proteins, apoptosis genes, oncogenes, tumor-suppressor genes, and growth factors. These results suggest that multiple pathways are involved in rat bladder tumorigenesis, and a common molecular mechanism was found in both rat and mouse bladder tumors.

Hyperactivation of Ha-ras oncogene, but not Ink4a/Arf deficiency, triggers bladder tumorigenesis

Although ras is a potent mitogenic oncogene, its tumorigenicity depends on cellular context and cooperative events. Here we show that low-level expression of a constitutively active Ha-ras in mouse urothelium induces simple urothelial hyperplasia that is resistant to progression to full-fledged bladder tumors even in the absence of Ink4a/Arf. In stark contrast, doubling of the gene dosage of the activated Ha-ras triggered early-onset, rapidly growing, and 100% penetrant tumors throughout the urinary tract. Tumor initiation required superseding a rate-limiting step between simple and nodular hyperplasia, the latter of which is marked by the emergence of mesenchymal components and the coactivation of AKT and STAT pathways as well as PTEN inactivation. These results indicate that overactivation of Ha-ras is both necessary and sufficient to induce bladder tumors along a low-grade, noninvasive papillary pathway, and they shed light on the recent findings that ras activation, via point mutation, overexpression, or intensified signaling from FGF receptor 3, occurs in 70%-90% of these tumors in humans. Our results highlight the critical importance of the dosage/strength of Ha-ras activation in dictating its tumorigenicity--a mechanism of oncogene activation not fully appreciated to date. Finally, our results have clinical implications, as inhibiting ras and/or its downstream effectors, such as AKT and STAT3/5, could provide alternative means to treat low-grade, superficial papillary bladder tumors, the most common tumor in the urinary system.

The relation between survival and expression of HER1 and HER2 depends on the expression of HER3 and HER4: a study in bladder cancer patients

Increased expression of the epidermal growth factor (EGF) receptors, HER1 and HER2 are related to poor prognosis in most cancers studied. Recently, a high expression of the two remaining receptors of the EGF system, HER3 and HER4 has been related to a favourable prognosis. However, prognostic significance of HER1 and HER2 receptors in bladder cancer is controversial and the effect of the expression of different combinations of these receptors on patient survival is not well understood. Therefore, we examined the mRNA expression of all four EGF receptors with real-time polymerase chain reaction in biopsies from 88 patients with bladder cancer, where the survival was followed for a median of 38.5 months (range 1-117 months). Expression of HER1 and HER2 alone showed no correlation with survival. However, a high expression of HER1 together with high expression of HER3 and HER4 correlated to a better prognosis compared to the high expression of HER1 together with low expression of HER3 and HER4 (P=0.0006). Also, a significantly longer survival was observed in patients expressing high HER2 when coexpressed with high HER3 and HER4, as compared to the survival in patients with tumours expressing high HER2 but low HER3 and HER4 (P=0.0005). Our results suggest that the final outcome of patients with high HER1- and HER2-expressing tumours depends on the expression of HER3 and HER4.

RIG1 inhibits the Ras/mitogen-activated protein kinase pathway by suppressing the activation of Ras

The retinoid-inducible gene 1 (RIG1) protein is a retinoid-inducible growth regulator. Previous studies have shown that the RIG1 protein inhibits the signaling pathways of Ras/mitogen-activated protein kinases. However, neither the mode of action nor the site of inhibition of RIG1 is known. This study investigated the effects of RIG1, and the mechanisms responsible for these effects, on the activation of Ras proteins in HtTA cervical cancer cells. RIG1 reduced the levels of activated Ras (Ras-GTP) and total Ras protein in cells transfected with mutated H-, N-, or K-Ras(G12V), or in cells transfected with the wild type H- or N-Ras followed by stimulation with epidermal growth factor. The half-life of Ras protein decreased from more than 36 h in control cells to 18 h in RIG1-transfected cells. RIG1 immunoprecipitated with the Ras protein in co-transfected cellular lysates. In contrast to the predominant plasma membrane localization in control cells, the H-Ras fusion protein EGFP-H-Ras was localized within a discrete cytoplasmic compartment where it co-localized with RIG1. RIG1 inhibited more than 93% of the Elk- and CHOP-mediated transactivation induced by H- or K-Ras(G12V). However, RIG1 did not inhibit the transactivation induced by MEK1 or MEK3, and failed to suppress the phosphorylation of extracellular signal-regulated kinases 1 and 2 induced by the constitutively activated B-Raf(V599E). The RIG1 with carboxyl terminal truncation (RIG1DeltaC) did not immunoprecipitate with Ras and had no effect on Ras activation or transactivation of the downstream signal pathways. These data indicate that RIG1 exerts its inhibitory effect at the level of Ras activation, which is independent of Ras subtype but dependent on the membrane localization of the RIG1 protein. This inhibition of Ras activation may be mediated through downregulation of Ras levels and alteration of Ras subcellular distribution.

A multinomial Phase II study of lonafarnib (SCH 66336) in patients with refractory urothelial cancer☆

PURPOSE

Protein farnesylation by farnesyltransferase (FTase) is required for membrane localization and effective signal transduction by G-proteins, including Ras. Lonafarnib inhibits FTase and has shown antitumor activity in both preclinical and clinical settings. As disturbances in Ras signaling pathways have been implicated in the pathogenesis of transitional cell carcinoma (TCC), the antitumor activity of lonafarnib was studied in a National Cancer Institute of Canada Clinical Trials Group Phase II trial in patients with previously treated TCC.

PATIENTS AND METHODS

Patients had at least 1 prior chemotherapy regimen for advanced unresectable or metastatic TCC, or recurrence less than 1 year after adjuvant or neoadjuvant chemotherapy. Lonafarnib was given at a dose of 200 mg PO twice daily continuously, with cycles repeated every 4 weeks.

RESULTS

Between December 1999 and December 2000, 19 eligible patients were enrolled at 8 National Cancer Institute of Canada Clinical Trials Group centers. Median time on treatment was 7.1 weeks (range, 0.6-23.9). Drug-related Grade 3 toxicities included fatigue, anorexia, nausea, confusion, dehydration, muscle weakness, depression, headache, and dyspnea. Five patients discontinued the study protocol due to toxicity. No responses were observed in 10 patients who were evaluable. Of 9 patients not evaluable for response, 5 had symptomatic progression, fulfilling multinomial criteria to stop the study after the first stage.

CONCLUSION

No single-agent activity of lonafarnib was observed in this study of patients with aggressive TCC failing prior chemotherapy.

Altered gene expression profile in mouse bladder cancers induced by hydroxybutyl(butyl)nitrosamine

A variety of genetic alterations and gene expression changes are involved in the pathogenesis of bladder tumor. To explore these changes, oligonucleotide array analysis was performed on RNA obtained from carcinogen-induced mouse bladder tumors and normal mouse bladder epithelia using Affymetrix (Santa Clara, CA) MGU74Av2 GeneChips. Analysis yielded 1164 known genes that were changed in the tumors. Certain of the upregulated genes included EGFR-Ras signaling genes, transcription factors, cell cycle-related genes, and intracellular signaling cascade genes. However, downregulated genes include mitogen-activated protein kinases, cell cycle checkpoint genes, Rab subfamily genes, Rho subfamily genes, and SH2 and SH3 domains-related genes. These genes are involved in a broad range of different pathways including control of cell proliferation, differentiation, cell cycle, signal transduction, and apoptosis. Using the pathway visualization tool GenMAPP, we found that several genes, including TbR-I, STAT1, Smad1, Smad2, Jun, NFkappaB, and so on, in the TGF-beta signaling pathway and p115 RhoGEF, RhoGDI3, MEKK4A/MEKK4B, PI3KA, and JNK in the G13 signaling pathway were differentially expressed in the tumors. In summary, we have determined the expression profiles of genes differentially expressed during mouse bladder tumorigenesis. Our results suggest that activation of the EGFR-Ras pathway, uncontrolled cell cycle, aberrant transcription factors, and G13 and TGF-beta pathways are involved, and the cross-talk between these pathways seems to play important roles in mouse bladder tumorigenesis.

H-Ras oncogene counteracts the growth-inhibitory effect of genistein in T24 bladder carcinoma cells

Among eight human bladder cancer cell lines we examined, only T24 cells were resistant to the growth inhibition effect of genistein, an isoflavone and potent anticancer drug. Since the T24 cell line was the only cell line known to overexpress oncogenic H-Ras(val 12), we investigated the role of H-Ras(val 12) in mediating drug resistance. Herein, we demonstrate that the phenotype of T24 cells could be dramatically reversed and became relatively susceptible to growth inhibition by genistein if the synthesis of H-Ras(val 12) or its downstream effector c-Fos had been suppressed. The inhibition of Ras-mediated signalling with protein kinase inhibitors, such as PD58059 and U0126 which inhibited MEK and ERK, in T24 cells also rendered the identical phenotypic reversion. However, this reversion was not observed when an inhibitor was used to suppress the protein phosphorylation function of PI3 K or PKC. These results suggest that the signal mediated by H-Ras(val 12) is predominantly responsible for the resistance of the cells to the anticancer drug genistein.

Expression of HER3, HER4 and their ligand heregulin-4 is associated with better survival in bladder cancer patients

The epidermal growth factor system has been associated to prognosis in patients with bladder cancer based mainly on the expression of the epidermal growth factor (EGF) receptor 1 (EGFR) and HER2 and their activating ligands. Since limited information exists concerning the expression of other parts of the EGF system, we examined the expression of the receptors HER3 and HER4 and their activating ligands, the heregulins (HRGs), in bladder cancer patients. Biopsies from bladder cancer tumours were obtained from 88 patients followed for a median of 23 months (range, 1-97 months). The mRNA content of four ligands and their isoforms (HRG1alpha, HRG1beta, HRG2alpha, HRG2beta, HRG3 and HRG4) and two receptors (HER3 and HER4) was quantified by real-time PCR. A significantly lower mRNA expression level of HER3 (P=0.0003), HRG2alpha (P=0.0159), HRG2beta (P=0.0007) and HRG4 (P<0.0001) was observed in muscle-invasive (T2-T4) tumours as compared to superficial (Ta) tumours. The expression of HER3 mRNA correlated strongly to overall survival (P=0.0042); increased expression of HER4 (P=0.0261) and HRG4 (P=0.0245) was also associated with better prognosis. Interestingly, patients with coexpression of HER3 (P=0.0034) or HER4 (P=0.0080) together with their stimulating ligand HRG4 showed even better survival than for HER3 or HER4 alone. Our results together with previous data suggest a dual face for the EGF system. While it is well established that an increased signalling through HER1 and HER2 is related to a poor prognosis, our data suggest that signalling through HER3 and HER4 is related to a favourable outcome in bladder cancer patients.

Down-Regulation of S100C Is Associated with Bladder Cancer Progression and Poor Survival

Purpose: The goal of this study was to identify proteins down-regulated during bladder cancer progression.

Experimental design: By using comparative proteome analysis and measurement of mRNA, we found a significant down-regulation of S100C, a member of the S100 family of proteins, in T24 (grade 3) as compared with RT4 (grade 1) bladder cancer cell lines. Moreover, quantification of the mRNA level revealed that decreased expression of the protein reflects a low level of transcription of the S100C gene. Based on this observation, we quantified the S100C mRNA expression level with real-time PCR in bladder cancer biopsy samples obtained from 88 patients followed for a median of 23 months (range, 1-97 months).

Results: We found a significantly lower mRNA expression of S100C in connective tissue invasive tumors (T1, P = 0.0030) and muscle invasive tumors [(T2-T4), P &lt; 0.0001] compared with superficial tumors (Ta). A negative correlation between S100C and histopathologic grade (P = 0.0003) was also observed. Furthermore, the papillary type showed higher expression of S100C than did the solid type of the tumor (P &lt; 0.0001). Importantly, we found that loss of S100C was associated with survival in bladder cancer patients (P = 0.0006).

Conclusions: Our results show that low expression of S100C is associated with poor survival in patients with bladder cancer. Furthermore, loss of S100C in T1 as compared with Ta stage tumors emphasize that S100C expression is suppressed early during bladder cancer development.

Human RAS superfamily proteins and related GTPases

The tumor oncoproteins HRAS, KRAS, and NRAS are the founding members of a larger family of at least 35 related human proteins. Using a somewhat broader definition of sequence similarity reveals a more extended superfamily of more than 170 RAS-related proteins. The RAS superfamily of GTP (guanosine triphosphate) hydrolysis-coupled signal transduction relay proteins can be subclassified into RAS, RHO, RAB, and ARF families, as well as the closely related Galpha family. The members of each family can, in turn, be arranged into evolutionarily conserved branches. These groupings reflect structural, biochemical, and functional conservation. Recent findings have provided insights into the signaling characteristics of representative members of most RAS superfamily branches. The analysis presented here may serve as a guide for predicting the function of numerous uncharacterized superfamily members. Also described are guanosine triphosphatases (GTPases) distinct from members of the RAS superfamily. These related proteins employ GTP binding and GTPase domains in diverse structural contexts, expanding the scope of their function in humans.

p53 deficiency provokes urothelial proliferation and synergizes with activated Ha-ras in promoting urothelial tumorigenesis

Mutation and deletion of the p53 tumor suppressor gene are arguably the most prevalent among the multiple genetic alterations found in human bladder cancer, but these p53 defects are primarily associated with the advanced diseases, and their roles in bladder tumor initiation and in synergizing with oncogenes in tumor progression have yet to be defined. Using the mouse uroplakin II gene promoter, we have targeted into urothelium of transgenic mice a dominant-negative mutant of p53 that lacks the DNA-binding domain but retains the tetramerization domain. Urothelium-expressed p53 mutant binds to and stabilizes the endogenous wild-type p53, induces nuclear abnormality, hyperplasia and occasionally dysplasia, without eliciting frank carcinomas. Concurrent expression of the p53 mutant with an activated Ha-ras, the latter of which alone induces urothelial hyperplasia, fails to accelerate tumor formation. In contrast, the expression of the activated Ha-ras in the absence of p53, as accomplished by crossing the activated Ha-ras transgenic mice with the p53 knockout mice, results in early-onset bladder tumors that are either low-grade superficial papillary or high grade in nature. These results provide the first in vivo experimental evidence that p53 deficiency predisposes the urothelium to hyperproliferation, but is insufficient for bladder tumorigenesis; that the mere reduction of p53 dosage, as produced in transgenic mice expressing the dominant-negative p53 or in heterozygous p53 knockouts, is incapable of synergizing with Ha-ras to induce bladder tumors; and that the complete loss of p53 is a prerequisite for collaborating with activated Ha-ras to promote bladder tumorigenesis.

The role of Ras superfamily proteins in bladder cancer progression

PURPOSE

The prognosis of patients with bladder cancer is strongly dependent on whether the lesion is superficial or invasive at initial presentation. In addition, a significant fraction of patients presenting with superficial disease have invasive tumor during followup. Understanding how superficial bladder cancer progresses to invasive forms of the disease is of paramount importance for early diagnosis and successful treatment. Molecular mechanisms underlying bladder cancer progression are being elucidated. We reviewed the roles that members of the Ras superfamily of monomeric G proteins, an important class of cellular regulator, have in bladder cancer and its progression.

MATERIALS AND METHODS

We performed MEDLINE searches focusing on members of the Ras superfamily of monomeric G proteins and their involvement in transitional cell carcinoma, which is the most common form of bladder cancer. General involvement in cancer of key superfamily members, focusing on mechanisms and downstream pathways, was also reviewed through MEDLINE and manual bibliographic searches.

RESULTS

With more than 100 members in humans the Ras superfamily is a diverse group of monomeric G proteins. These proteins regulate many cellular processes, such as cell cycle progression, actin cytoskeletal dynamics and membrane traffic. Members of the Ras and Rho family are also known to be involved in human cancer through mutation, over expression and dysregulation. In this review we focus on bladder cancer. In particular we focus on how H-Ras, RalA/B and RhoGDI2, a regulator of Rho family members, participate in bladder cancer progression and how their participation may be related to other molecules associated with bladder cancer progression, such as epidermal growth factor receptor, p53 and PTEN (phosphatase and tensin homologue deleted on chromosome 10).

CONCLUSIONS

The findings discussed offer the hopeful possibility that signaling pathways mediated by Ras superfamily members may offer new opportunities for diagnostic and therapeutic interventions in bladder cancer.

Genetic instability in superficial bladder cancer and adjacent mucosa: an interphase cytogenetic study

A systematic analysis of both tumors and the surrounding urothelium to help identify what lies behind the mechanism of multifocal tumor development has not yet been performed. In this study we investigated chromosome 1, 7, 9, and 17 aneusomy in 25 superficial papillary carcinomas and in 51 tissue samples taken from sites of macroscopically uninvolved urothelium surrounding the tumors, using the fluorescence in situ hybridization method. Our data demonstrated a close genetic relationship between all examined tumors and normal-appearing mucosa. Numeric aberrations of chromosomes 1, 7, 9, and 17 were found to exhibit similar patterns in all analyzed specimens, although with different frequencies.

Role of Ha-ras activation in superficial papillary pathway of urothelial tumor formation

Urothelial tumors develop along two distinctive phenotypic pathways (superficial papillary non-invasive tumors versus flat carcinoma in situ lesions), with markedly different biological behavior and prognosis. Although multiple genetic alterations have been identified in human bladder cancer, their cause-effect relationship with the two pathways has not been firmly established. Using a urothelium-specific promoter of the uroplakin II gene, we showed earlier in transgenic mice that the urothelial expression of SV40T antigen, which inactivates p53 and pRb, induced carcinoma in situ and invasive and metastatic bladder cancer. In striking contrast, we demonstrate here that the urothelial expression of an activated Ha-ras in transgenic mice caused urothelial hyperplasia and superficial papillary non-invasive bladder tumors. These results provide strong, direct experimental evidence that the two phenotypical pathways of bladder tumorigenesis are caused by distinctive genetic defects. Our results indicate that Ha-ras activation can induce urothelial proliferation in vivo; and that urothelial hyperplasia is a precursor of low-grade, superficial papillary bladder tumors. Our transgenic models provide unique opportunities to study the detailed molecular events underlying different types of bladder neoplasms, and can serve as useful preclinical models for evaluating the in vivo efficacy of preventive and therapeutic agents that act on various signaling pathways in bladder cancer.

Interphase cytogenetics of bladder cancer progression: relationship between aneusomy, DNA ploidy pattern, histopathology, and clinical outcome

In the present study, different stages of transitional cell carcinoma of the bladder were analyzed by fluorescent in situ hybridization, using probes specific for pericentromeric classical satellite. Seventy primary tumors were evaluated for chromosomes 1, 7, 9, 17, and ploidy by flow cytometry. The results were correlated, after a mean follow-up period, with ploidy, histopathological characteristics, recurrence, and progression. Firstly, our data demonstrated that the sensitivity of fluorescence in situ hybridization in detecting quantitative DNA aberrations exceeds that of flow cytometry. The frequency of chromosome 1 and 9 aberrations was not significantly different in diploid and aneuploid tumors of different stage and grade. In contrast, the chromosome 7 and 17 aneusomy showed greater differences between pT1 and pT2-3 tumors (P<0.032 and P<0.0006, respectively) than between stage pTa and pT1. An increasing number of aberrations was observed in all chromosomes examined from tumors of patients that afterwards underwent cystectomy and/or had recurrent tumors. This study indicates that fluorescence in situ hybridization could be used to detect genetic changes relevant to patient outcome. These genetic changes could identify patients at high risk of recurrence and possible progression.

Inhibition of human bladder cancer cell motility by genistein is dependent on epidermal growth factor receptor but not p21ras gene expression

A significant portion of patients who present with non-muscle invasive "superficial" bladder cancer develop the muscle "invasive" life-threatening form of the disease during subsequent follow-up. In clinical studies, overexpression of the epidermal growth factor receptor (EGFR) and the p21 ras oncogene have been strongly associated with this phenotypic tumor transition. The marked difference in incidence of invasive bladder cancer in Asia compared to the United States has made us hypothesize that, among other factors, dietary influences have an impact on such tumor progression. A significantly higher dietary consumption of soy products exists in Asia and has led to the notion that the isoflavones present in this diet may contribute to a reduction in the number of invasive transitional cell bladder cancers. In this regard, we sought to determine the effect of genistein, a naturally occurring dietary protein tyrosine kinase (PTK) inhibitor, on the growth and motility of human bladder cancer cell lines with diverse EGFR and p21ras expression phenotypes and corresponding invasive behaviors. These effects were compared with those of tyrphostin, a pure synthetic EGFR inhibitor. Our results indicate that both genistein and tyrphostin are effective inhibitors of bladder cancer motility and growth, key factors in the development of muscle invasive disease. In addition, the growth and motility inhibitory effects of genistein and tyrphostin are observed preferentially in cells that overexpress the EGFR. Cells that have a mutated p21ras but do not overexpress the EGFR are less inhibited by these 2 compounds, suggesting that their effect is primarily directed at the EGFR signal transduction pathways proximal to the p21ras gene. Our results would seem to corroborate the notion that a high dietary intake of isoflavones is a likely explanation for the decreased incidence of invasive bladder cancer.

Differential expression and mutation of the ras family genes in human breast cancer

The expression of ras mRNA levels in 27 human sporadic breast cancer specimens was examined, and compared to the corresponding adjacent normal tissue using the RT-PCR technique. Eighteen out of the 27 specimens (67%) exhibited two- to four-fold increased expression of ras mRNA levels, compared to corresponding normal tissue. The rates of augmented mRNA expression were similar among the three ras genes. A statistically significant correlation of overexpression of ras genes in specimens classified as Stage I disease was observed, compared to tumors in a more advanced stage (II or III). The incidence of codon 12 point mutations of the K-ras gene in fresh tissue samples was also assessed in 61 human sporadic breast cancer cases. Point mutations were detected in four (6.5%) out of the 61 cases examined; no correlation was found with any clinicopathological parameter. This is the first report to our knowledge of the differential expression of the ras family genes in breast carcinoma. Our findings indicate that the aberrant expression of ras genes may be an initial event in breast cancer oncogenesis and that K-ras point mutations are rarely involved in the development of mammary neoplasias.

Alterations of TP53 in microdissected transitional cell carcinoma of the human urinary bladder: high frequency of TP53 accumulation in the absence of detected mutations is associated with poor prognosis

We have used microdissection of paraffin-embedded histological sections and polymerase chain reaction (PCR)-based direct DNA sequencing for 54 transitional cell carcinoma (TCC) of the bladder, to examine critically the association between TP53 nuclear accumulation determined by immunohistochemistry and the presence of TP53 mutations, and to examine their relationship to tumour stage and grade, as well as patient survival. There was a significant association between the presence of TP53-positive nuclei (> 10%) and a higher histological stage and grade (P = 0.0115, P = 0.0151 respectively; Fisher's exact). A significant association between TP53 gene mutations and TP53 nuclear reactivity in more than 10% of tumour cell nuclei was also observed (P = 0.0003; Fisher's exact). Mutations were detected in 18/54 (33%) cases together with the wild-type sequence when analysed from bulk frozen samples, with significant clustering of mutations in exons 7 and 8. The microdissection method distinguished more clearly between heterozygous and/or homozygous alterations of the TP53 tumour-suppressor gene, and clearly showed frequent accumulation of TP53 in the absence of mutations. When microdissecting immunonegative regions from the same paraffin sections, three out of ten samples showed the identical mutations detected in the immunopositive regions. There was a significant association between TP53 immunoreactivity in more than 50% of tumour cell nuclei and decreased survival among all patients (P = 0.0325; log-rank test). The patients with TP53 mutations showed a trend for a shorter survival period; however, the association was not statistically significant at the 95% confidence level (P = 0.132; log-rank test). In conclusion, our observations show that accumulation of TP53 occurs frequently in the absence of mutations, and that such accumulation is nevertheless associated with poor survival when it occurs in a high proportion (> 50%) of tumour cell nuclei.