A critical analysis of the use of p53 as a marker for management of bladder cancer

TP53 codon 72 polymorphism is associated with FGFR3 and RAS mutation in non-muscle-invasive bladder cancer

Objective

TP53, a well-known tumor-suppressor gene in bladder carcinogenesis, has a functional single-nucleotide polymorphism on codon 72. The aim of this study was to elucidate the association between TP53 codon 72 polymorphism and somatic mutations in bladder cancer.

Material and methods

Germline TP53 codon 72 polymorphism and somatic mutations of 50 cancer-associated genes were analyzed in 103 bladder cancer patients (59 non-muscle-invasive and 44 muscle-invasive), using Taqman genotyping assay and target sequencing, respectively. The expression of FGF-FGFR signaling pathway genes was analyzed by RNA sequencing of frozen tissue.

Results

The allele frequency of TP53 codon 72 in our cohort was 37, 42, and 21% for Arg/Arg, Arg/Pro, and Pro/Pro, respectively. Interestingly, the prevalence of FGFR3 mutation was higher in patients with the Arg allele, whereas that of the RAS mutation was higher in patients without the Arg allele. The same association was seen in non-muscle-invasive bladder cancer (NMIBC) patients and no differences were observed in muscle-invasive bladder cancer patients. In NMIBC, FGFR1 expression was higher in patients without the Arg allele and FGFR3 expression was higher in patients with the Arg allele.

Conclusion

The germline TP53 codon 72 polymorphism was associated with mutations of FGFR3 or RAS and expression of FGFR1 and FGFR3 in NMIBC. These findings provide new insight into the molecular mechanisms underlying the influence of the genetic background on carcinogenesis in bladder cancer.

Epigenetic alterations in bladder cancer and their potential clinical implications

Urothelial carcinoma (UC), the most common type of bladder cancer, is one of the most expensive malignancies to treat due to its high rate of recurrence. The characterization of the genetic alterations associated with UC has revealed the presence of two mutually exclusive molecular pathways along which distinct genetic abnormalities contribute to the formation of invasive and noninvasive tumors. Here, we focus on the epigenetic alterations found in UC, including the presence of an epigenetic field defect throughout bladders with tumors. A distinct hypomethylation pattern was found in noninvasive tumors, whereas widespread hypermethylation was found in invasive tumors, indicating the two pathways given rise to two tumor types also differ epigenetically. Since certain epigenetic alterations precede histopathological changes, they can serve as excellent markers for the development of diagnostic, prognostic, and surveillance tools. In addition, their dynamic nature and reversibility with pharmacological interventions open new and exciting avenues for therapies. The epigenetic abnormalities associated with UC would make it an excellent target for epigenetic therapy, which is currently approved for the treatment of a few hematological malignancies. Future research is needed to address efficacy and potential toxicity issues before it can be implemented as a therapeutic strategy for solid tumors.

Molecular profiling of bladder tumors based on the detection of FGFR3 and TP53 mutations

PURPOSE

On a routine basis we performed systematic molecular screening for FGFR3 and TP53 mutations in 121 bladder tumors. We then specifically analyzed the predictive value of the recurrence of FGFR3 and TP53 genotypes in superficial lesions.

MATERIALS AND METHODS

The FGFR3 gene was analyzed by direct sequencing of exons 7, 10 and 15, whereas TP53 status was determined using the p53 functional assay in yeast.

RESULTS

We identified a missense FGFR3 mutation in 66% of pTa, 26% of pT1 and 12% of pT2 tumors. Of activating FGFR3 mutations 54% and 85% were found in low G1 and intermediate G2 grade tumors, respectively, but in only 20% of high grade G3 tumors. We detected inactivating TP53 mutations in 10% of pTa, 42% of pT1 and 58% of pT2 tumors. Moreover, TP53 mutations were found only in 23% of grade G1 and 3% of grade G2 tumors but in 44% of high grade G3 tumors. When the 2 genotypes were combined, we observed that 58% of pTa tumors had the (mutant FGFR3, WT TP53) genotype, whereas 58% of invasive lesions harbored the inverse genotype (WT FGFR3, mutant TP53). The (mutant FGFR3, WT TP53) genotype and the (WT FGFR3, mutant TP53) genotype were detected in 23% and 38% of pT1G3 tumors, respectively. In the subgroup of 92 patients with superficial pTa-T1 bladder tumors we did not find that the TP53 or FGFR3 genotype alone or combined had a predictive value for tumor recurrence.

CONCLUSIONS

Our data again represent solid proof for the pivotal role of FGFR3 and TP53 mutations in superficial and invasive bladder tumors, respectively. However, other molecular markers should be identified for borderline pT1G3 bladder tumors, which are probably at the crossroads of these 2 distinct molecular pathways.

P53 as a prognostic marker for bladder cancer: a meta-analysis and review

BACKGROUND

P53 is the most widely investigated molecular marker in bladder cancer. We aimed to review comprehensively the evidence for use of changes in P53 to predict bladder-cancer recurrence, progression, and mortality.

METHODS

We reviewed 168 publications from 117 studies. Estimates of significance were extracted from association tests, and hazard ratios with 95% CI from actuarial curves and Cox regression analyses. A meta-analysis was done on the studies that applied Cox models.

FINDINGS

The methods used to assess significance varied widely between studies. 27% (nine of 34) of studies that assessed the prognostic value of P53 overexpression in recurrence by use of multivariate tests showed a significant association. The corresponding values for progression and mortality were 50% (12 of 24) and 29% (ten of 35), respectively. In the studies that used Cox models, the overall risk of recurrence was 1.6 (95% CI 1.2-2.1), of progression was 3.1 (1.9-4.9), and of mortality was 1.4 (1.2-1.7). These findings could be overestimates because of publication and reporting bias.

INTERPRETATION

After 10 years of research, evidence is not sufficient to conclude whether changes in P53 act as markers of outcome in patients with bladder cancer.

p53 immunodetection of liquid-based processed urinary samples helps to identify bladder tumours with a higher risk of progression

p53 could help identify bladder tumour cases with a risk of progression from superficial to invasive disease. Semiautomatic, liquid-based cytology (LBC) techniques offer an opportunity to standardise molecular techniques. The aim of our study was to investigate whether LBC could improve p53 immunolabelling, and to assess whether urinary p53 could have a prognostic value. Immunoreactivity for p53 was studied in 198 urine samples after treatment with the Cytyc Thinprep® processor. After antigen retrieval, cells were labelled with a monoclonal antibody that recognises both wild-type and mutant form of the p53 protein (Clone DO-7, Dako), 1/1000. Positivity for p53 was assessed in 17.2% of the cases. High-grade (G3) tumours were positive in 74.1% of the cases. Comparatively, low-grade (G1–2) urothelial carcinomas were positive in 23.5% of the cases. During a median follow-up period of 26 months, recurrence was observed in 52.9% of the cases with p53 overexpression, and in only 10.9% of negative cases (P<0.001). The progression rate was 35.3% of p53-positive cases vs 5.5% of p53-negative cases (P<0.001). Progression-free survival was significantly shorter in patients with p53 accumulation (P=0.007). In a multivariate analysis stratified on grade and stage, p53 was an independent predictor of overall survival (P=0.042). The results show that using Thinprep® LBC, p53 immunolabelling of voided urothelial cells allows most high-grade tumours to be detected and may help identify cases with a higher risk of recurrence and progression.

Apoptosis and chemotherapy for bladder cancer

PURPOSE

We discuss the role of apoptosis, that is gene directed self-destruction of a cell, in the response of bladder transitional cell carcinoma cells to chemotherapy.

MATERIALS AND METHODS

A directed MEDLINE literature search of apoptosis, bladder cancer and chemotherapy was performed to extract relevant information for review. The characteristics of apoptotic cells were defined and the methods in common use to detect these traits is described. The role of the key mediators of the apoptotic process in bladder cancer is discussed in the context of chemosensitivity and disease stage. The importance of the apoptosis induction after chemotherapy is highlighted.

RESULTS

On stimulus by appropriate external or internal signals a cell may alter the expression of genes encoding for proteins associated with the apoptotic process. The development of apoptosis depends on the balance between pro-apoptotic and anti-apoptotic proteins. Key alterations in genes and proteins related to apoptosis within bladder cancer result in a shift away from the default state of apoptosis toward a cell with increased survival properties that is chemoresistant.

CONCLUSIONS

Much current research in bladder cancer is aimed at restoring chemosensitivity by shifting the cell toward a pro-apoptotic phenotype. Successful translation of this work into clinical practice may improve survival in patients in whom prognosis is currently poor.

Expression of p53 and mdm2 and their significance in recurrence of superficial bladder cancer

The purpose of this study is to evaluate the expression of p53 and mdm2 and to determine whether they may be used as additional predictors of recurrence in superficial transitional cell carcinoma of the bladder. Paraffin sections of 80 patients with superficial transitional cell carcinoma of the bladder, who were treated with transurethral resection, were stained with p53 and mdm2 antibodies using the standard avidin biotin immunoperoxidase method. Nuclear staining for both p53 and mdm2 was calculated as the percentage of labeled nuclei out of a total number of tumor cells counted. The percentage of p53- and mdm2-positive cells showed a significant relationship with tumor grade and recurrence (p = 0.002 and p = 0.016; p = 0.01 and p = 0.003, respectively). In addition, a weak inverse relationship was found between p53 and mdm2 values (r = -0.184). p53 and mdm2 reactivities are valuable parameters in predicting recurrence in superficial bladder cancer. Thus, mdm2 expression appears to play a role in predicting biologic behavior in superficial transitional carcinoma of the bladder.

Diagnosis and management of superficial bladder cancer

Bladder cancer is the fourth leading cause of cancer in American men, accounting for more than 12,000 deaths annually. It was one of the first malignancies in which carcinogens were recognized as an important factor in its cause. Currently, cigarette smoking is by far the most common cause of bladder cancer, although occupational exposure to arylamines has been implicated in the past. Gross or microscopic hematuria is the most common sign at presentation. Initial radiologic evaluation usually includes the excretory urography (intravenous pyelography), although further evaluation of the renal parenchyma with ultrasound or computed tomography scanning has been advocated by some. These radiologic studies are unable to provide adequate bladder imaging, and thus cystoscopy is required for the diagnosis of bladder cancer. Most bladder cancers present as "superficial" disease, confined to the bladder mucosa or submucosal layer, without muscle invasion. Superficial tumors consist of papillary tumors that are mucosally confined (Ta), papillary or sessile tumors extending into the lamina propria (T1), and carcinoma in situ, which occurs as "flat" mucosal dysplasia, which can be focal, diffuse, or associated with a papillary or sessile tumor. The natural history of these pathologic subtypes differ significantly. Most superficial tumors (60% to 70%) have a propensity for recurrence after transurethral resection. Some (15% to 25%) are at high risk for progression to muscle invasion. Most superficial tumors can be stratified into high- or low-risk groups depending on tumor stage, grade, size, number, and recurrence pattern. It is important to identify those tumors at risk for recurrence or progression so that adjuvant intravesical therapies can be instituted. Many intravesical chemotherapeutic agents have been shown to reduce tumor recurrence when used in conjunction with transurethral tumor resection. Unfortunately, however, none of these agents have proved to be of benefit in preventing disease progression. Most are given intravesically on a weekly basis, although many studies suggest that a single instillation immediately after transurethral resection may be as good as a longer course of therapy. Although all of these drugs have toxicity, they usually are well tolerated. Intravesical bacille Calmette-Guérin (BCG) is an immunotherapeutic agent that when given intravesically is very effective in the treatment of superficial transitional cell carcinoma. Compared with controls, BCG has a 43% advantage in preventing tumor recurrence, a significantly better rate than the 16% to 21% advantage of intravesical chemotherapy. In addition, BCG is particularly effective in the treatment of carcinoma in situ, eradicating it in more than 80% of cases. In contrast to intravesical chemotherapy, BCG has also been shown to decrease the risk of tumor progression. The optimal course of BCG appears to be a 6-week course of weekly instillations, followed by a 3-week course at 3 months in those tumors that do not respond. In high-risk cancers, maintenance BCG administered for 3 weeks every 6 months may be optimal in limiting recurrence and preventing progression. Unfortunately, adverse effects associated with this prolonged therapy may limit its widespread applicability. In those patients at high risk in whom BCG therapy fails, intravesical interferon-alpha with or without BCG may be beneficial in some. Photodynamic therapy has also been used but is limited by its toxicity. In patients who progress or do not respond to intravesical therapies, cystectomy should be considered. With the development of orthotopic lower urinary tract reconstruction to the native urethra, the quality of life impact of radical cystectomy has been lessened.

Clinical sensitivity of p53 mutation detection in matched bladder tumor, bladder wash, and voided urine specimens

BACKGROUND

Mutations in the p53 tumor suppressor gene may correlate with an increased risk of recurrence and disease progression in patients with bladder carcinoma. The ability to accurately and sensitively detect p53 mutations in cytology specimens may be of benefit in the treatment of bladder carcinoma patients with superficial, minimally invasive disease.

METHODS

Genomic DNA was isolated from 49 cases, each of which was comprised of matched bladder tumor tissue, bladder wash, and voided urine specimens obtained concurrently at a single institution. The genomic DNA was analyzed for mutations in the p53 tumor suppressor gene using a p53 mutation detection assay. Automated dideoxy sequencing of mutant specimens also was performed.

RESULTS

Of the 49 cases, 29 (59%) showed no evidence of p53 mutations in the tumor, bladder wash, or voided urine specimens. Of the remaining 20 cases, 19 showed evidence of mutations in the tumor. Of these 19 p53 mutant bladder tumors, 16 (84%) were detected in the matched bladder wash and 16 (84%) were detected in the matched voided urine specimens. One case resulted in the detection of mutant p53 in the voided urine and the bladder wash, but not in the tumor. Analysis of the results between tumor tissue and bladder wash or tumor and voided urine showed 84.2% sensitivity, 96.8% specificity, and 91.8% accuracy. Sequence analysis of the mutant cases showed that the mutations detected in the tumor tissue were the same mutations detected in the bladder wash and the voided urine specimens.

CONCLUSIONS

Both voided urine and bladder wash specimens from patients with bladder carcinoma were found to provide a high rate of clinical accuracy for the determination of the p53 gene status in patients with bladder tumors.

Biomarkers for the detection of bladder cancer

In this subject review, a series of morphology-based and molecular markers were compared with urinary cytology for the detection of recurrent urothelial neoplasia. Among the various biomarkers reviewed, the average published sensitivity and specificity for the Bard BTA test was 60% and 77%; the NMP22 Test was 67% and 72%; the telomerase assay was 77% and 85%; and the microsatellite assay was 89% and 100%. DNA ploidy measurements and immunoassays designed to detect keratins, proteins, hyaluronidase, growth factors, cell adhesion molecules, fibrinogen degradation products, cell cycle regulators, and molecular markers were also included. Although the performance features of these biomarkers have varied and the cytologic methods to which they have been compared have not been standardized, several of the procedures have received considerable support from urologists as assisting them in the management of their patients.