Loss of heterozygosity at 9q32–33 (DBC1 locus) in primary non-invasive papillary urothelial neoplasm of low malignant potential and low-grade urothelial carcinoma of the bladder and their associated normal urothelium

Description of longitudinal tumor evolution in a case of multiply relapsed clear cell sarcoma of the kidney

Background

Clear cell sarcoma of the kidney (CCSK) is the second most common pediatric renal tumor.

Case

A 2‐year‐old boy was diagnosed with CCSK, which relapsed four times until he yielded to the disease at the age of 7 years. To characterize the longitudinal genetic alterations occurring in the present case, we performed targeted‐capture sequencing by pediatric solid tumors panel (381 genes) for longitudinally sampled tumors, including autopsy samples of metastasis. Internal tandem duplication of BCOR (BCOR‐ITD) was the only truncal mutation, confirming the previously reported role of BCOR‐ITD in CCSK.

Conclusion

Acquisition of additional mutations along tumor relapses and detection of metastasis‐specific mutations were reminiscent of the tumor progression and therapeutic resistance of this case, leading to clonal selection and a dismal fate.

Expression of proteins FGFR3, PI3K, AKT, p21Waf1/Cip1 and cyclins D1 and D3 in patients with T1 bladder tumours: clinical implications and prognostic significance

OBJECTIVE

To determine the differential protein expression of biomarkers FGFR3, PI3K (subunits PI3Kp110α, PI3KClassIII, PI3Kp85), AKT, p21Waf1/Cip1 and cyclins D1 and D3 in T1 bladder cancer versus healthy tissue and to study their potential role as early recurrence markers.

MATERIAL AND METHOD

This is a prospective study that employed a total of 67 tissue samples (55 cases of T1 bladder tumours that underwent transurethral resection and 12 cases of adjacent healthy mucosa). The protein expression levels were assessed using Western blot, and the means and percentages were compared using Student's t-test and the chi-squared test. The survival analysis was conducted using the Kaplan-Meier method and the log-rank test.

RESULTS

Greater protein expression was detected for FGFR3, PI3Kp110α, PI3KClassIII, cyclins D1 and D3 and p21Waf1/Cip1 in the tumour tissue than in the healthy mucosa. However, these differences were not significant for PI3Kp85 and AKT. We observed statistically significant correlations between early recurrence and PI3Kp110α, PI3KClassIII, PI3Kp85 and AKT (P=.003, P=.045, P=.050 and P=.028, respectively), between the tumour type (primary vs. recurrence) and cyclin D3 (P=.001), between the tumour size and FGFR3 (P=.035) and between multifocality and cyclin D1 (P=.039). The survival analysis selected FGFR3 (P=.024), PI3Kp110α (P=.014), PI3KClassIII (P=.042) and AKT (P=.008) as markers of early-recurrence-free survival.

CONCLUSIONS

There is an increase in protein expression levels in bladder tumour tissue. The overexpression of FGFR3, PI3Kp110α, PI3KClassIII and AKT is associated with increased early-recurrence-free survival for patients with T1 bladder tumours.

[Tumorigenesis from a pathological perspective : Tumor spread and epigenetically regulated genes in bladder cancer]

The article describes the tumorigenesis of bladder cancer from a pathological perspective in three dimensions: morphology, genetics and epigenetics. Field cancerization and tumor cell migration/seeding are the two main hypotheses used for explaining synchronous and metachronous tumors in the urinary tract. By detailed histological mapping of completely embedded cystectomy specimens we found a single tumor focus in nearly 2/3 of the bladders accompanied by surrounding preinvasive carcinoma in situ. We substantiated our findings by studies analyzing TP53 mutations and loss of heterozygosity in various tumor sites. Identical TP53 mutations suggested a clonal relationship of the tumor foci. In situ lineage tracing via cytochrome C oxidase and succinate dehydrogenase enzyme histochemistry and subsequent mitochondrial DNA mutation analysis for definitive evidence of a clonal relationship in bladder tumors remained inconclusive. We found indications for both theories but intraurothelial migration/seeding was more prominent.A further mechanism in tumorigenesis is gene inactivation by epigenetic DNA methylation. We analyzed DNA methylation of various genes, which had previously been found by RNA expression analysis to be downregulated in bladder cancer. Most importantly, epigenetically silenced ITIH5 was associated with early relapse in pT1 high grade tumors and functionally showed an enhanced invasive metastatic phenotype in tumor cells, suggesting a putative tumor suppressive role. Thus, epigenetic gene silencing is an additional mechanism of tumorigenesis especially in tumor progression.

Decreased DBC1 Expression Is Associated With Poor Prognosis in Patients With Non-Muscle-Invasive Bladder Cancer

Purpose

The deleted in bladder cancer 1 (DBC1) gene is located within chromosome 9 (9q32-33), a chromosomal region that frequently shows loss of heterozygosity in bladder cancer (BC). It is suspected that it acts as a tumor suppressor gene, but its prognostic value remains unclear. The aim of the present study was to investigate the value of DBC1 as a prognostic marker in BC.

Materials and Methods

The expression of DBC1 was determined by real-time polymerase chain reaction analysis in 344 patients with BC (220 non-muscle-invasive BC [NMIBC] and 124 muscle-invasive BC [MIBC]) and in 34 patients with normal bladder mucosa. The results were compared with clinicopathologic parameters, and the prognostic value of DBC1 was evaluated by Kaplan-Meier analysis and a multivariate Cox regression model.

Results

DBC1 expression was significantly decreased in patients with MIBC compared with those diagnosed with NMIBC (p=0.010). Patients with aggressive tumor characteristics had lower DBC1 expression levels in NMIBC (each, p<0.05). By multivariate Cox regression analysis, low DBC1 expression was a predictor of progression to MIBC (hazard ratio, 7.104; p=0.013). Kaplan-Meier estimates revealed a significant difference in tumor recurrence, progression to MIBC, and cancer-specific survival depending on the level of DBC1 expression in NMIBC (log-rank test, each, p<0.05).

Conclusions

The expression of DBC1 was associated with tumor aggressiveness, progression to MIBC, and survival in NMIBC. Our results suggest that DBC1 expression can be a useful prognostic marker for patients with NMIBC.

Bladder cancer: translating molecular genetic insights into clinical practice

Transitional cell (urothelial) carcinoma of the bladder is the second most common urologic malignancy and is one of the best understood neoplasms, with relatively well-defined pathogenetic pathways, natural history, and tumor biology. Conventional clinical and pathologic parameters are widely used to grade and stage tumors and to predict clinical outcome of transitional cell carcinoma; but the predictive ability of these parameters is limited, and there is a lack of indices that could allow prospective assessment of risk for individual patients. In the last decade, a wide range of candidate biomarkers representing key pathways in carcinogenesis have been reported to be clinically relevant and potentially useful as diagnostic and prognostic molecular markers, and as potential therapeutic targets. The use of molecular markers has facilitated the development of novel and more accurate diagnostic, prognostic, and therapeutic strategies. FGFR3 and TP53 mutations have been recognized as key genetic pathways in the carcinogenesis of transitional cell carcinoma. FGFR3 appears to be the most frequently mutated oncogene in transitional cell carcinoma; its mutation is strongly associated with low tumor grade, early stage, and low recurrence rate, which confer a better overall prognosis. In contrast, TP53 mutations are associated with higher tumor grade, more advanced stage, and more frequent tumor recurrences. These molecular markers offer the potential to characterize individual urothelial neoplasms more completely than is possible by histologic evaluation alone. Areas in which molecular markers may prove valuable include prediction of tumor recurrence, molecular staging of transitional cell carcinoma, detection of lymph node metastasis and circulating cancer cells, identification of therapeutic targets, and prediction of response to therapy. With accumulating molecular knowledge of transitional cell carcinoma, we are closer to the goal of bridging the gap between molecular findings and clinical outcomes. Assessment of key genetic pathways and expression profiles could ultimately establish a set of molecular markers to predict the biological nature of tumors and to establish new standards for molecular tumor grading, classification, and prognostication. The main focus of this review is to discuss clinically relevant biomarkers that might be useful in the management of transitional cell carcinoma and to provide approaches in the analysis of molecular pathways that influence the clinical course of bladder cancer.

Molecular pathways of urothelial development and bladder tumorigenesis

Bladder cancer is the fifth most common human malignancy and the second most frequently diagnosed genitourinary tumor after prostate cancer. The majority of malignant tumors arising in the urinary bladder are urothelial carcinomas. Clinically, superficial bladder tumors (stages Ta and Tis) account for 75% to 85% of neoplasms, while the remaining 15% to 25% are invasive (T1, T2-T4) or metastatic lesions at the time of initial presentation. Several studies have revealed that distinct genotypic and phenotypic patterns are associated with early vs. late stages of bladder cancer. Early superficial disease appears to segregate into 2 main pathways: (1) superficial papillary bladder tumors, which are characterized by gain-of-function mutations affecting oncogenes such as H-RAS, FGFR3, and PI3K, and deletions of the long arm of chromosome 9 (9q); (2) Carcinoma in situ, a "flat" high grade lesion considered to be a precursor of invasive cancer, is characterized by loss-of-function mutations affecting tumor suppressor genes, such as p53, RB, and PTEN. Based on these data, a model for bladder tumor progression has been proposed in which 2 separate genetic pathways characterize the evolution of early bladder neoplasms. Several molecular markers have been correlated with tumor stage, but the rationale for these 2 well-defined genetic pathways still remains unclear. Normal urothelium is a pseudo-stratified epithelium that coats the bladder, composed of 3 cell types: basal, intermediate, and superficial ("umbrella") cells. We have identified a series of markers that are differently expressed in these distinct cells types, and postulated a novel model for urothelium development and configuration. Briefly, it is our working hypothesis that 2 distinct progenitor cells are responsible for basal/intermediate cells and "umbrella" cells, respectively. Basal and intermediate cells are characterized by a p63 positive phenotype, as well as expression of high molecular weight cytokeratins (CKs), such as CK5, CK10, and CK14. On the contrary, "umbrella" cells display a p63 negative phenotype and are characterized by expression of 2 specific low molecular weight CKs: CK18 and CK20. Neither urothelial stem cells nor bladder cancer stem cells have been identified to date. In this review, we will further expand on the issues discussed above.

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.

Molecular determinants of tumor recurrence in the urinary bladder

Tumor recurrence is a major clinical concern for patients with urothelial carcinoma of the urinary bladder. Traditional morphological analysis is of limited utility for identifying cases in which recurrence will occur. However, molecular and genetic analyses offer new perspectives on the prediction of bladder tumor recurrence. Recent studies have suggested that urothelial carcinogenesis occurs as a 'field effect' that can involve any number of sites in the bladder mucosa. Accumulating evidence supports the notion that resident urothelial stem cells in the affected field are transformed into cancer stem cells by acquiring genetic alterations that lead to tumor formation through clonal expansion. Both initial and recurrent tumors are derived from cancer stem cells in the affected field via two distinct molecular pathways. These provide a genetic framework for understanding urothelial carcinogenesis, tumor recurrence and progression: the FGFR3-associated pathway and the TP53-associated pathway. These two pathways are characterized by different genomic, epigenetic and gene-expression alterations. Their outcomes correlate with the markedly different clinical and pathologic features of both relatively indolent low-grade cancers and the aggressive high-grade cancers. As such, these molecular findings are potentially useful for counseling patients and for assessing risk of recurrence or biological aggressiveness of the patient's tumor. The molecular changes may additionally prove useful for developing preventive and therapeutic strategies for urothelial bladder cancer. A unifying model of urothelial carcinogenesis, tumor recurrence and progression is proposed in this review.

Environmental factors and genetic susceptibility promote urinary bladder cancer

Cancer of the urinary bladder is the second most common malignancy of the genitourinary tract, currently accounting for up to 5% of all newly diagnosed tumours in the western world. Urinary bladder carcinogenesis seems to develop from the interaction of environmental exposure and genetic susceptibility. Smoking, specific industrial chemicals, dietary nitrates and arsenic represent the most important exogenous risk factors. Chromosomal abnormalities, silencing of certain genes by abnormal methylation of their promoter region, alterations in tumour suppressor genes and proto-oncogenes that induce uncontrolled cell proliferation and reduced apoptosis, are molecular mechanisms that have been reported in bladder carcinogenesis. In this article, we discuss the environmental risk factors of bladder cancer and we review the genetic and epigenetic alterations, including aberrant DNA methylation and deregulation of microRNAs expression. We also discuss the role of p53 and retinoblastoma suppressor genes in disease progression. Finally, we present recent reports on the use of molecular profiling to predict disease stage and grade and direct targeted therapy.

Expression of basic fibroblast growth factor, its receptors and syndecans in bladder cancer

Basic fibroblast growth factor (bFGF) is a heparin-binding cationic protein involved in a variety of pathological conditions including angiogenesis and solid tumour growth. The basic fibroblast growth factor receptor (FGFR) family comprises at least 4 high affinity tyrosine kinase receptors that require syndecans for their function. Mounting evidence indicates that syndecans, that bind both bFGF and their FGFRs, will act as stimulators, whereas syndecans that only bind bFGF will act as inhibitors of signaling by sequestering the growth factor. Recent findings have highlighted the importance of syndecans in urological cancers. The aim of this study is to investigate the expression of bFGF, its receptors (R1 and R2) and syndecans (1-4) in invasive urothelial carcinoma and normal-looking urothelium by Western blotting, RT-PCR, and immunohistochemistry analyses. Interestingly, bFGF, FGFR1 and FGFR2 protein levels statistically increased in bladder cancer tissues. mRNA of FGFR1 and syndecans (1-4), showed a statistically significant increase while an mRNA increase in the other molecules analysed was not significant. bFGF, its receptors and syndecan immunostaining were mainly present in the urothelium both in normal-looking tissues and urothelial neoplastic cells. In conclusion, our data report that the bFGF, FGFR and syndecan expressions are altered in bladder tumours.

FGFR3 and TP53 gene mutations define two distinct pathways in urothelial cell carcinoma of the bladder

FGFR3 and TP53 mutations are frequent in superficial papillary and invasive disease, respectively. We used denaturing high-performance liquid chromatography and sequencing to screen for FGFR3 and TP53 mutations in 81 newly diagnosed urothelial cell carcinomas. Tumors were classified as follows: 31 pTa, 1 carcinoma in situ, 30 pT1, and 19 pT2-T4. Tumor grades were as follows: 10 G1, 29 G2, and 42 G3. FGFR3 mutations were associated with low-stage (P < 0.0001), low-grade (P < 0.008) tumors, whereas TP53 mutations were associated with high-stage (P < 0.003), high-grade (P < 0.02) tumors. Mutations in these two genes were almost mutually exclusive. Our results suggest that FGFR3 and TP53 mutations define separate pathways at initial diagnosis of urothelial cell carcinoma.