Detection of bladder cancer recurrence by microsatellite analysis of urine

Quantitation of promoter methylation of multiple genes in urine DNA and bladder cancer detection

BACKGROUND

The noninvasive identification of bladder tumors may improve disease control and prevent disease progression. Aberrant promoter methylation (i.e., hypermethylation) is a major mechanism for silencing tumor suppressor genes and other cancer-associated genes in many human cancers, including bladder cancer.

METHODS

A quantitative fluorogenic real-time polymerase chain reaction (PCR) assay was used to examine primary tumor DNA and urine sediment DNA from 15 patients with bladder cancer and 25 control subjects for promoter hypermethylation of nine genes (APC, ARF, CDH1, GSTP1, MGMT, CDKN2A, RARbeta2, RASSF1A, and TIMP3) to identify potential biomarkers for bladder cancer. We then used these markers to examine urine sediment DNA samples from an additional 160 patients with bladder cancers of various stages and grades and from an additional 69 age-matched control subjects. Data were analyzed on the basis of a prediction model and were internally validated using a jacknife procedure. All statistical tests were two-sided.

RESULTS

For all 15 patients with paired DNA samples, the promoter methylation pattern in urine matched that in the primary tumors. Four genes displayed 100% specificity. Of the 175 bladder cancer patients, 121 (69%, 95% confidence interval [CI] = 62% to 76%) displayed promoter methylation in at least one of these genes (CDKN2A, ARF, MGMT, and GSTP1), whereas all control subjects were negative for such methylation (100% specificity, 95% CI = 96% to 100%). A logistic prediction model using the methylation levels of all remaining five genes was developed and internally validated for subjects who were negative on the four-gene panel. This combined, two-stage predictor produced an internally validated ROC curve with an overall sensitivity of 82% (95% CI = 75 % to 87%) and specificity of 96% (95% CI = 90% to 99%).

CONCLUSION

Testing a small panel of genes with the quantitative methylation-specific PCR assay in urine sediment DNA is a powerful noninvasive approach for the detection of bladder cancer. Larger independent confirmatory cohorts with longitudinal follow-up will be required in future studies to define the impact of this technology on early detection, prognosis, and disease monitoring before clinical application.

High throughput comparative genomic hybridization array analysis of multifocal urothelial cancers

The purpose of this study was to examine genetic alterations occur during synchronous or metachronous multifocal development of urothelial cancers on the whole genome using a comparative genomic hybridization (CGH) array. We used 10 tumor pairs (2 tumors for each patient), in which we had previously defined a clonal relationship by microsatellite analysis. For CGH array analysis, Vysis GenoSensor Array 300 kit was used. An unsupervised hierarchical cluster analysis revealed that the tumors from one patient were clustered together independent of the tumors of all other patients. On the other hand, many genetic divergences among multifocal urothelial cancers were newly found by a CGH array analysis. The concordant genetic alteration patterns of the chromosomal arm in tumor pairs were most frequently observed in 9p, 9q, 8p, 7p, 7q and 11q, while discordant patterns were most frequently found in 15q, 20q, 2q, 10p and 11q. Investigation using a CGH array showed that genetically stable multifocal tumors were less frequent, and that a large percentage of urothelial cancers accumulate genetic alterations during multifocal development by clonal evolution. We might have to consider these genetic accumulations during multifocal development when designing strategies for prevention and detection of recurrent multifocal urothelial cancers. CGH array can be a powerful tool for genetic analysis of multifocal urothelial cancer.

Nichtinvasives und invasives Harnblasenkarzinom

Therapy of superficial bladder tumors is transurethral resection (TUR), and in cases of pT1 or high-grade tumors a re-TUR is indicated. Patients with carcinoma in situ receive intravesical chemotherapy or BCG for at least 3 months. Persistent carcinoma in situ may be treated by radical cystectomy. With the provision of a functionally adequate urinary diversion, cystectomy represents an effective treatment for patients with muscle-invasive bladder cancer without metastatic spread. Regional lymph node metastases can be found in up to 15% of stage T1 disease and are present in 33% of stage T3/4 lesions. Thus, lymphadenectomy gains diagnostic and possibly also therapeutic importance. For selected patients, who cannot be treated by radical cystectomy, multimodal concepts aiming to preserve the bladder are discussed. After or prior to cystectomy systemic chemotherapy may become necessary for some patients to positively affect the course of the disease in cases of locally advanced or metastatic lesions.

Molecular markers in bladder cancer: A critical appraisal

The diagnosis of both primary and recurrent bladder tumors currently relies upon the urine cytology and cystoscopy. Neither of these diagnostic tools is completely accurate. Prognostication of bladder cancer is largely based on pathologic tumor grade and stage. Over the past 2 decades, there is accumulating evidence that like many other cancers, bladder cancer, too, has a distinct molecular signature that separates it from other cancers and normal bladder tissue. Bladder tumors of different grades and stages even possess unique, and specific genotypic and phenotypic characteristics. Although recognition of several of these molecular alterations is possible by analyzing tumor tissue, urine, and serum samples, few if any of these "molecular markers" for bladder cancer are widely used in clinical practice. These markers include some that can be applied during the diagnostic work-up of symptoms (e.g., hematuria), those under surveillance for recurrence of superficial disease and forecasting long-term prognosis, or response to chemotherapy. In this review of molecular markers for bladder cancer, effectiveness of markers in each of these categories that are identifiable in the urine of patients with bladder cancer was examined. Many of the diagnostic markers appear to hold an advantage over urine cytology in terms of sensitivity, especially for the detection of low-grade superficial tumors. However, most markers tend to be less specific than cytology, yielding more false-positives. This result is more commonly observed in patients with concurrent bladder inflammation or other benign bladder conditions. Although there are several candidate markers for assessing prognosis or response to chemotherapy, studies of large patient populations are lacking. Further studies involving larger numbers of patients are required to determine their accuracy and widespread applicability in guiding treatment of bladder cancer.

Transrenal DNA testing: progress and perspectives

Transrenal DNA (Tr-DNA) is a recently discovered class of extracellular urinary DNA that originates from cells dying throughout the body. Postapoptotic DNA is known to appear in the circulating plasma, but it is now recognized that a portion of these fragments cross the kidney barrier and appear in urine in the form of 150-200-bp fragments. Tr-DNA containing fetal sequences has been isolated from the urine of pregnant women, tumor-specific mutations have been detected in Tr-DNA from patients with colon and pancreatic tumors, and donor DNA has been found in Tr-DNA isolated from recipient urine. Furthermore, proviral HIV DNA, bacterial and parasite DNA sequences have been detected in Tr-DNA from infected patients. Potential applications of Tr-DNA-based tests cover a very broad area of molecular diagnostics and genetic testing, including prenatal detection of inherited diseases, tumor diagnostics and therapeutic monitoring and detection of infectious agents. The Tr-DNA test is expected to have utility in treatment monitoring, transplantation monitoring, drug development and broad public health screening, where a noninvasive, common-platform diagnostic technology has particular value. This review describes some of the highlights of Tr-DNA technology applications, advantages over existing technologies and potential problems anticipated in test development.

Multiplex Polymerase Chain Reaction for Microsatellite Analysis of Urine Sediment Cells: A Rapid and Inexpensive Method for Diagnosing and Monitoring Superficial Transitional Bladder Cell Carcinoma

PURPOSE

Several urinary markers have been recently introduced in clinical practice for improving the noninvasive diagnosis of transitional cell carcinoma. Although microsatellite analysis must be considered the best method in terms of results, its cost and method time are unacceptable for daily use. We validated a more rapid and inexpensive method of determination using rapid DNA extraction and automatic multiplex polymerase chain reaction amplification.

MATERIALS AND METHODS

A total of 120 patients who presented consecutively to a urological office, including 73 with transitional cell carcinoma and 43 who served as controls, were selected for study. Microsatellite analysis was performed in the blood/urine pair using 3 multiplex polymerase chain reactions per patient. Urine sediment inflammatory cells were assessed by urine dipstick test. Ten microsatellite loci were investigated. Numerical data collected during electrophoresis of the amplified segment in an ABI Prism 310 Genetic Analyzer were used to calculate the cutoff for allelic imbalance. Method sensitivity, specificity, and positive and negative predictive values were calculated.

RESULTS

A total of 66 patients had microsatellite analysis alterations in urine sediment, of whom 59 had transitional cell carcinoma, while 7 had other urological diseases. Test sensitivity and specificity were 80.8% and 85.1%, respectively. Statistical analysis did not indicate any significant influence of inflammatory status on microsatellite analysis diagnostic performance. In the control group the allelic imbalance on chromosome 9 was significantly lower than on other chromosomes (p = 0.0143). This could confirm that chromosome 9 has a specific role in transitional cell carcinoma. The multiplex microsatellite analysis method was low cost and not time-consuming.

CONCLUSIONS

Multiplex microsatellite analysis is a noninvasive, rapid, inexpensive and reproducible method for screening for and monitoring superficial transitional cell carcinoma. It should be considered an alternative method to urinary cytology and it should also be considered in the presence of urine sediment inflammatory cells.

Methylational urinalysis: a prospective study of bladder cancer patients and age stratified benign controls

Tumour suppressor gene (TSG) methylation has been proposed as a diagnostic marker for urothelial cancer (UC). Here, we compare the frequency of urinary TSG methylation in young and elderly patients, with and without UC. Urine samples were obtained prospectively from 35 UC patients, 35 benign controls over the age of 70 years and 34 healthy volunteers under the age of 40 years. Methylation analysis was performed for eight gene promoters using quantitative methylation-specific PCR. Methylation was detected in urine DNA from all three patient groups. The highest frequencies were seen in UC patients. Significantly less methylation was present in control samples than UC cases for RASSF1a and APC (P < 0.034). The 'methylation index' and level of methylation was highest in the UC group and lowest in the young control group. A marker panel of RASSF1a, E-cad and APC generated a sensitivity of 69%, a specificity of 60% and a diagnostic accuracy of 86%. TSG methylation is detectable in urine DNA from patients with and without bladder cancer. The frequency and extent of methylation appears to increase with age and malignancy. The lack of tumour specificity suggests that further investigation is required before this test is introduced into clinical practice.

The detection of oesophageal adenocarcinoma by serum microsatellite analysis

BACKGROUND AND AIMS

Organ-confined oesophageal cancer in an early stage can be cured in many patients, whereas more extensive lesions have a poor prognosis. We sought to develop a non-invasive test for cancer detection and evaluation of the prognosis of the patients by using a novel molecular approach.

MATERIAL AND METHODS

Matched normal-, tumour- and serum-samples were obtained from 32 patients with adenocarcinoma of the oesophagus. DNA was extracted and the samples were subjected to microsatellite analysis using 12 markers. Serum and normal samples from 10 healthy individuals served as controls.

RESULTS

Twenty-seven of the 32 patients (84.4%) with malignant tumours were found to have one or more microsatellite DNA alterations in their primary tumour. Twenty-six of the 32 patients (81.3%) had alterations in the serum by microsatellite analysis. Interestingly, all patients without lymphatic metastasis and three early carcinomas (pT1pN0) already displayed LOH alteration in the serum, while all serum DNA of samples from normal control subjects were negative. Survival was not significantly correlated with either LOH in the tumour or LOH in the serum.

CONCLUSION

These data suggest that microsatellite DNA analysis in serum specimens might provide a potentially valuable tool for early detection of oesophageal cancer. The evidence of circulating tumour DNA reflects the propensity of these tumours to spread to distant sites. Up to now the follow-up is still too short to draw further conclusions on the prognostic impact of this finding.

Bladder tumor markers beyond cytology: International Consensus Panel on bladder tumor markers

This is the first of 2 articles that summarize the findings of the International Consensus Panel on cytology and bladder tumor markers. The objectives of our panel were to reach a consensus on the areas where markers are needed, to define the attributes of an ideal tumor marker, and to identify which marker(s) would be suitable for diagnosis and/or surveillance of bladder cancer. Our panel consisted of urologists and researchers from Europe, Asia, and the United States who reviewed original articles, reviews, and book chapters on individual bladder tumor markers published in the English language mainly using the PubMed search engine. Panel members also met during 3 international meetings to write recommendations regarding bladder tumor markers. The panel found that the most practical use of noninvasive tests is to monitor bladder cancer recurrence, thereby reducing the number of surveillance cystoscopies performed each year. Markers also may be useful in the screening of high-risk individuals for early detection of bladder cancer. However, more prospective studies are needed to strengthen this argument. Case-control and cohort studies show that several markers have a higher sensitivity to detect bladder cancer. However, cytology is the superior marker in terms of specificity, although some markers in limited numbers of studies have shown specificity equivalent to that of cytology. Our panel believes that several bladder tumor markers are more accurate in detecting bladder cancer than prostate-specific antigen (PSA) is in detecting prostate cancer. However, bladder tumor markers are held to a higher standard than PSA. Therefore, use of bladder tumor markers in the management of patients with bladder cancer will require the willingness of both urologists and clinicians to accept them.

Evidence for alternative candidate genes near RB1 involved in clonal expansion of in situ urothelial neoplasia

In this paper, we present whole-organ histologic and genetic mapping studies using hypervariable DNA markers on chromosome 13 and then integrate the recombination- and single-nucleotide polymorphic sites (SNPs)-based deletion maps with the annotated genome sequence. Using bladders resected from patients with invasive urothelial carcinoma, we studied allelic patterns of 40 microsatellite markers mapping to all regions of chromosome 13 and 79 SNPs located within the 13q14 region containing the RB1 gene. A whole-organ histologic and genetic mapping strategy was used to identify the evolution of allelic losses on chromosome 13 during the progression of bladder neoplasia. Markers mapping to chromosomal regions involved in clonal expansion of preneoplastic intraurothelial lesions were subsequently tested in 25 tumors and 21 voided urine samples of patients with bladder cancer. Four clusters of allelic losses mapping to distinct regions of chromosome 13 were identified. Markers mapping to the 13q14 region that is flanked by D13S263 and D13S276, which contains the RB1 gene, showed allelic losses associated with early clonal expansion of intraurothelial neoplasia. Such losses could be identified in approximately 32% bladder tumor tissue samples and 38% of voided urines from patients with bladder cancer. The integration of distribution patterns of clonal allelic losses revealed by the microsatellite markers with those obtained by genotyping of SNPs disclosed that the loss within an approximately 4-Mb segment centered around RB1 may represent an incipient event in bladder neoplasia. However, the inactivation of RB1 occurred later and was associated with the onset of severe dysplasia/carcinoma in situ. Our studies provide evidence for the presence of critical alternative candidate genes mapping to the 13q14 region that are involved in clonal expansion of neoplasia within the bladder antecedent to the inactivation of the RB1 gene.

Origin of multifocal carcinomas of the bladder and upper urinary tract: molecular analysis and clinical implications

The simultaneous or metachronous development of multifocal tumors with identical or variable histological features in the urothelial tract in a single patient is a well-known characteristic of urothelial cancer. To explain this phenomenon, two distinct concepts have been proposed: the 'field defect' hypothesis according to which urothelial cells in patients are primed to undergo transformation by previous carcinogenic insults and the 'single progenitor cell' hypothesis, which asserts that the multifocal development is caused by the seeding or intraepithelial spread of transformed cells. Results of recent molecular genetic studies support the 'single progenitor cell' hypothesis, and indicate that the genetic and phenotypic diversity observed in multifocal urothelial tumors is a consequence of clonal evolution from a single transformed cell. An understanding of the mechanism of the heterotopic recurrence of urothelial cancer may provide new prospects for early molecular detection and prevention of heterotopic recurrence of urothelial cancer.

Molecular evidence supporting field effect in urothelial carcinogenesis

PURPOSE

Human urothelial carcinoma is thought to arise from a field change that affects the entire urothelium. Multifocality of urothelial carcinoma is a common finding at endoscopy and surgery. Whether these coexisting tumors arise independently or are derived from the same tumor clone is uncertain. Molecular analysis of microsatellite alterations and X-chromosome inactivation status in the cells from each coexisting tumor may further our understanding of urothelial carcinogenesis.

EXPERIMENTAL DESIGN

We examined 58 tumors from 21 patients who underwent surgical excision for urothelial carcinoma. All patients had multiple separate foci of urothelial carcinoma (two to four) within the urinary tract. Genomic DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-capture microdissection. Loss of heterozygosity (LOH) assays for three microsatellite polymorphic markers on chromosome 9p21 (IFNA and D9S171), regions of putative tumor suppressor gene p16, and on chromosome 17p13 (TP53), the p53 tumor suppressor gene locus, were done. X-chromosome inactivation analysis was done on the urothelial tumors from 11 female patients.

RESULTS

Seventeen of 21 (81%) cases showed allelic loss in one or more of the urothelial tumors in at least one of the three polymorphic markers analyzed. Concordant allelic loss patterns between each coexisting urothelial tumor were seen in only 3 of 21 (14%) cases. A concordant pattern of nonrandom X-chromosome inactivation in the multiple coexisting urothelial tumors was seen in only 3 of 11 female patients; of these 3 cases, only one displayed an identical allelic loss pattern in all of the tumors on LOH analysis.

CONCLUSION

LOH and X-chromosome inactivation assays show that the coexisting tumors in many cases of multifocal urothelial carcinoma have a unique clonal origin and arise from independently transformed progenitor urothelial cells, supporting the "field effect" theory for urothelial carcinogenesis.

Use of polymerase chain reaction analysis of urinary DNA to detect bladder carcinoma

A cohort of 113 patients underwent prospective evaluation with a panel of seven microsatellites, on chromosomes 9, 13 and 17. Thirty-seven patients had histologically confirmed bladder tumors, 53 patients had a history of previous transitional cell carcinoma of the bladder (TCC) but normal cystoscopies (control Group 1), and 23 patients had no previous history of TCC and normal cystoscopies (control Group 2). Urinary DNA was considered to show a deletion if an allele was reduced by more than 50%, and this was considered diagnostic of bladder carcinoma. The sensitivity of the method was 50%, positive predictive value was 80%, and specificity was 93%. Reducing the threshold for defining allelic loss increases sensitivity, but reduces specificity. The concentration of urinary DNA in the sample did not influence detection rate. The grade and stage of the bladder tumor did not influence the likelihood of detection. This method detects bladder carcinoma with high specificity, and increasing the number of microsatellites used should increase sensitivity.

Detection of bladder cancer in urine by a tumor suppressor gene hypermethylation panel

PURPOSE

Bladder cancer is potentially curable in the majority of cases; however, the prognosis for patients with advanced disease at presentation remains poor. Current noninvasive tests such as cytology lack sufficient sensitivity to detect low-grade, low-stage tumors. Silencing of tumor suppressor genes, such as p16(INK4a), VHL, and the mismatch repair gene hMLH1, has established promoter hypermethylation as a common mechanism for tumor suppressor inactivation in human cancers. It is also a promising new target for molecular detection in bodily fluids including urine, a readily accessible fluid known to contain bladder cancer cells. Methylation-specific PCR (MSP) can determine the presence or absence of methylation of a gene locus at a sensitivity level of up to 1 methylated allele in 1000 unmethylated alleles, appropriate for identifying cancer cell DNA in a bodily fluid.

EXPERIMENTAL DESIGN

We first determined the frequency of hypermethylation of the Rb tumor suppressor gene by bisulfite sequencing and of the p16(INK4a), p14(ARF), APC, and RASSF1A tumor suppressor genes by MSP in 45 bladder cancers. We then designed a panel optimal for diagnostic coverage composed of the APC, RASSF1A, and p14(ARF) tumor suppressor genes. This panel was tested for detection of hypermethylation in matched sediment DNA from urine specimens obtained before surgery from the same 45 bladder cancer patients (2 Tis, 16 Ta, 10 T1, and 17 T2-4) as well as normal and benign control DNAs.

RESULTS

Hypermethylation of at least one of three suppressor genes (APC, RASSF1A, and p14(ARF)) was found in all 45 tumor DNAs (100% diagnostic coverage). We detected gene hypermethylation in the matched urine DNA from 39 of 45 patients (87% sensitivity), including 16 cases that had negative cytology. No hypermethylation of APC, RASSF1A, or p14(ARF) was observed in normal transitional cell DNAs or in urine DNAs from normal healthy individuals and patients with inflammatory urinary disease (cystitis). Furthermore, an unmethylated gene in the tumor DNA was always found to be unmethylated in the matched urine DNA (100% specificity).

CONCLUSIONS

Promoter hypermethylation of tumor suppressor genes is common in bladder cancer and was found in all grades and stages of tumors examined. Hypermethylation was detected in the urine DNA from 39 of 45 (87%) patients, including cases of early-stage disease amenable to cure. MSP may enhance early detection of bladder cancer using a noninvasive urine test.

Alternatives to cytology in the management of non-muscle invasive bladder cancer

The natural history of non-muscle invasive bladder cancer is characterized by a high probability of recurrence and in the case of high-grade tumors, progression to muscle invasive cancer. This mandates a follow-up strategy designed to identify recurrences in the bladder early in their evolution in order to facilitate early intervention and ablation. Urine cytology is considered the gold standard urine biomarker. Although specificity exceeds 90% to 95%, its overall sensitivity ranges from 40% to 60% in expert hands and is both tumor grade and operator dependent. While cytology is an excellent test for detection of high-grade disease, the sensitivity is particularly weak for the detection of low grade tumors. This has spawned an entire field of research of in vitro diagnostic tests and cell-based assays in order to improve the diagnostic accuracy for detection of incident or recurrent disease. To date, the US Food and Drug Administration approved dipstick and immunoassays marketed as point-of-care tests. The point-of-care tests are intended for use as an adjunct to cystoscopy and cytology, and may have a role in the office evaluation of hematuria patients. Monoclonal antibody-based tests combined with cytology may improve the diagnostic accuracy and are superior to cytology alone. A recently approved cell-based assay, utilizing fluorescent in situ hybridization technology, may help resolve suspicious cytologies, and provide early and additional information about the biology of the bladder urothelium beyond that provided by cytology, a marker of disease relatively late in evolution. Novel promising markers are in various stages of clinical testing, and a panel of biomarkers may serve in the future as a feasible alternative to urine cytology and cystoscopy for the screening, detection, and follow-up of non-muscle invasive bladder cancer.

Advances in the clinical laboratory assessment of urinary sediment

Urinalysis has been used extensively in clinical practice to aid in the diagnosis of various renal and urologic diseases. The innovation of urinalysis is marching on right along with the rapid developments in biotechnology and astride from the solo urine cytology to sophisticated studies of individual component in the urinary sediment. In this review article, we focus on the use of flow cytometry and other technical advances in the examination of urinary sediment, the detection of urologic malignancies by the presence of microsatellite alteration in the urinary sediment, as well as the quantification of cytokine messenger RNA (mRNA) expression in urinary sediment by reverse transcription and real-time quantitative polymerase chain reaction (RT-QPCR). Notably, the study of cytokine mRNA expression in urinary sediment by RT-QPCR has recently been reported to provide important diagnostic information in kidney allograft recipients and patients with lupus nephritis. This simple and non-invasive method requires further study to determine its role in risk stratification and monitoring of therapeutic response in patients with other kidney diseases.

p53 and FHIT mutations and microsatellite alterations in malignancy-associated pleural effusion

Cancer is a genetic disease and thus is influenced by oncogenes and tumor suppressor genes. To determine whether the genetic analysis of pleural fluid can be used to diagnose malignant effusion, we investigated p53 and FHIT mutations and microsatellite alterations (MA) in the pleural fluid of 40 patients with pleural effusion associated with malignancy (ME) and in the pleural fluid of 17 patients with tuberculous pleurisy (TB) as a control group. p53 mutations were detected in five ME patients (13%) and in no TB patient, and FHIT mutations were detected in seven ME patients (18%) and two TB patients (12%). For four microsatellite markers, D3S1234, D3S1285, D9S171, and TP53, in ME patients, loss of heterozygosity (LOH) was seen in 10 (25%), 5 (13%), 10 (25%), and 6 patients (15%), respectively, and microsatellite instability (MI) in 6 (15%), 0 (0%), 1 (3%), and 3 patients (8%), respectively. Using the same markers, in TB patients, LOH was seen in three (18%), one (6%), three (18%), and one (6%), respectively, and MI in one (6%), zero (0%), zero (0%), and zero (0%), respectively. Twenty-five ME cases (63%) exhibited MA (LOH or MI) in at least one marker. Moreover, in four (80%) of five ME cases with negative cytology and no carcinoembryonic antigen increase in pleural fluid, MAs were identified. In ME, positive cytology was found in 42.5%, and positive MA, using four markers, in 63%. Although still limited in terms of sensitivity and specificity, this study shows that molecular diagnostic strategies could enhance the diagnostic yield in cases of malignant effusion.

Detection of bladder tumours: role of cytology, morphology-based assays, biochemical and molecular markers

PURPOSE OF REVIEW

Cystoscopy is currently considered the gold standard for the detection of bladder tumours. The role of urine cytology in the initial detection and follow-up of patients is under discussion. Many efforts have been made to increase the detection rates and to predict the outcome of bladder cancer. In this subject review, a series of morphology-based, biochemical and molecular markers were compared with urine cytology for the detection of bladder cancer.

RECENT FINDINGS

Among the various markers reviewed, the average published sensitivity and specificity for the Bard tumour antigen test was 60 and 77%; for the nuclear matrix protein 22 test it was 67 and 72%; for the hyaluronic acid and hyaluronidase test it was 91 and 84%; for the ImmunoCyt it was 90 and 75%; for fluorescence in-situ hybridization it was 85 and 95%; for the telomerase assay it was 77 and 85%; and for the microsatellite assay it was 89 and 100%. DNA ploidy measurements, recent molecular markers and immunoassays designed to detect keratins, proteins, cell adhesion molecules, fibrinogen degradation products, and fibrinolysis markers were also included.

SUMMARY

As is clear from the brief summary of available assays, the optimal method of application is not yet clear. The integration of an assay into clinical practice takes more than just the documentation of its sensitivity and specificity. However, several of the procedures have received considerable support from urologists as assisting them in the management of their patients.

Genetic instability and transitional cell carcinoma of the bladder

The development of cancer occurs in a stepwise fashion, with each step representing the mutation in one of several key genes. However, the mutation rate of somatic cells is too low to account for the number of mutations required for a cell to undergo carcinogenesis. Thus, the development of genetic instability is a vital early step towards carcinogenesis. We review the evidence for genetic instability, with particular reference to transitional cell carcinoma of the bladder. Both microsatellite instability and chromosomal instability are present in this tumour, and we discuss their incidence and clinical implications.

Construction of a global score quantifying allelic imbalance among biallelic SIDP markers in bladder cancer

The purpose of this paper is the construction of an adapted statistical test for urinary detection of bladder cancer based on the assessment of allelic imbalance using biallelic Short Insertion/Deletion Polymorphism DNA markers. This test is based on the comparison of several of these markers, analysed from urinary DNA, to the distribution of their analogues in blood, which is taken as reference. A reproductibility study is first performed in blood in order to make a selection among the 23 available markers and 18 are retained. A global score based on the chi2 distribution is then built to test for allelic imbalance among all informative markers for each patient. It avoids the count of DNA abnormalities marker by marker and allows to take into account the degree of abnormality of each marker. That method is preliminarily evaluated on a sample of 53 patients and 27 controls. The estimated specificity (96.3%) on that reduced sample is satisfactory, whereas sensitivity (60.4%) could be improved by an augmentation of the number of tested markers. Several issues regarding the validity of the method are discussed.

Distinct patterns of microsatellite instability are seen in tumours of the urinary tract

To date, two forms of microsatellite instability (MSI) have been described in human cancer. MSI typical of hereditary nonpolyposis colon cancer (HNPCC), is due to deficient DNA mismatch repair (MMR) and is defined with mono- and dinucleotide repeat microsatellites. A second variety of instability is best seen at selective tetranucleotide repeats (EMAST; elevated microsatellite alterations at select tetranucleotides). While MSI occurs infrequently in bladder cancers, EMAST is common. Sporadic tumours with the largest proportion showing MSI are those found most frequently in HNPCC kindreds. While bladder cancer is not frequently seen in HNPCC, upper urinary tract tumours (UTTs) are. Having previously found a low frequency of MSI in bladder cancer, we sought to determine the relative levels of MSI and EMAST in transitional cell carcinoma (TCC) of the upper and lower urinary tracts. Microsatellite analysis was performed at 10 mono- and dinucleotide and eight tetranucleotide loci, in 89 bladder and 71 UTT TCC. Contrasting patterns of instability were seen in urinary tumours. In bladder cancer, MSI was rare and EMAST was common. The presence of EMAST was not related to tumour grade, stage, subsequent outcome or immunohistochemical expression of the MMR proteins. In UTT, while MSI occurred frequently, EMAST was seen less frequently than in bladder cancer. When TCC of the upper and lower urinary tracts are compared, MSI-H is more frequent in UTT and EMAST more frequent in bladder cancer. Our findings show that, as for colorectal cancer, the pattern of MSI varies with location in the urinary tract. In addition, we have confirmed that MSI and EMAST are discrete forms of MSI, and that the presence of EMAST does not affect tumour phenotype.

[Microsatellite analysis in exfoliated cells from urinary sediment. Its utility for the detection of bladder cancer. Comparison with urinary cytology]

INTRODUCTION

Taking into account the precocity of the genetic alterations in the carcinogenesis of the bladder tumors, the valuation of these changes at a level of 9p 21-22 by means of microsatellite markers could be useful for the diagnostic and follow-up.

PURPOSE

To evaluate the use of microsatellite markers and the utility of loss of heterozigosity (LOH) and microsatellite instability (MSI) in exfoliated cells from urine sediment. This observation offers the possibility of tumor detection by examining the DNA of urinary sediment.

MATERIALS AND METHODS

We amplified with PCR the DNA of urine and blood samples from 160 patients with bladder cancer. We analysed LOH/MSI in cells from urinary sediment using four microsatellite markers of 9p 21-22 (D9S747-D9S171-D9S162-IFNA) and one from chromosome 4 (D4S243). The urinary cytology was used as comparative method and histological examination of tissue obtained by transurethral resection (TUR) as reference diagnostic. We calculated the sensitivity and specificity of this method and if there was some correlation between stage and grade tumoral.

RESULTS

We could use 150 samples correctly. In 111 samples we found LOH/MSI (sensitivity 74%). The cytology was positive only in 60 patients (sensitivity 40%). We found a bigger number of microsatellite alterations (AM) in superficial tumors (sensibility 77.3% vs. 28.8% for the cytology) and these were significant when comparing tumors GI-II vs. GIII (MSI p < 0.001--LOH p < 0.004). The marker with more sensibility was D4S243 with 40%. One patient with prostate carcinoma and another one with chronic cystitis gave false positive results.

CONCLUSIONS

The study of LOH/MSI in bladder tumors with 5 microsatellites markers, according to our results showed a sensibility of 74%. The biggest number in LOH/MSI was found in superficial tumors and GI-GII tumors. Although we cannot discard the cystoscopy study in the diagnostic and follow-up, the sensitivity of the urine cytology is better and could be one alternative diagnostic as a non-invasive procedure.

Diagnostic potential of circulating nucleic acids for oncology

Approximately a decade ago, the PCR-based detection of extracellular, tumor-derived circulating nucleic acids in the plasma and serum of cancer patients was introduced as a noninvasive tool for cancer detection. Although the test criteria, sensitivity and specificity, compare favorably with conventional diagnostic measures, until now the methodical ponderousness of circulating nucleic acids in plasma and serum analysis prevented it from becoming a clinical routine application. However, with rapid technical improvement towards automated high-throughput platforms, it is expected that the next 5 years will see circulating nucleic acids in plasma and serum analysis integrated into the initial diagnosis and follow-up monitoring of cancer patients. The hope is that the use of circulating nucleic acids in plasma and serum as a molecular tumor marker and potential profiling tool will finally translate into a longer survival and better quality of life for cancer patients.

Molecular analysis of peritoneal fluid in ovarian cancer patients

To determine whether genetic abnormalities present in primary ovarian tumors can be used to detect cancer cells in peritoneal fluid, we tested 14 ovarian cancers and 1 benign tumor of the ovary for loss of heterozygosity (LOH) at chromosomal arms 13q, 17p, 17q, and 22q and for mutations in the p53 and K-ras genes. In each case, matched primary tumor, normal tissue, and peritoneal fluid were analyzed. The highest frequency of LOH was found on chromosomal arm 17p (42%), followed by chromosomal arm 17q (36%), 22q (30%), and 13q (21%). Identical alterations were detected in matched peritoneal fluid (either peritoneal wash or ascitic fluid) in 3 of the 8 patients with LOH in the tumor (38%). Direct sequence analysis detected p53 mutations in 3 of the 14 malignant tumors (21%) and no (0) K-ras mutations. Identical mutations were detected in matched peritoneal fluid from all 3 patients with p53 mutations. All 8 of the 14 (57%) malignant tumors that showed at least one genetic abnormality were serous adenocarcinoma and identical alterations were detected in 5 of the 8 (62%) matched peritoneal fluid samples. Our findings indicate that molecular abnormalities can be detected in peritoneal fluid from patients with ovarian cancer and may be used to complement current conventional diagnostic procedures for detection of primary ovarian cancer.

Vysis UroVysion for the detection of urothelial carcinoma

For decades, cystoscopy and urine cytology have been the mainstay for monitoring superficial urothelial carcinoma patients for tumor recurrence. However, urine cytology has poor sensitivity for urothelial carcinoma and, consequently, numerous investigators have been endeavoring to develop more sensitive assays for the detection of urothelial carcinoma. This article presents an overview of the types of new assays that have been developed for urothelial carcinoma detection but focuses primarily on the features and performance of a new fluorescence in situ hybridization assay for urothelial carcinoma detection known as Vysis UroVysion.

Differential expression of hMLH1 and hMSH2 is related to bladder cancer grade, stage and prognosis but not microsatellite instability

Defects in the DNA mismatch repair proteins result in microsatellite instability and malignancy in hereditary non-polyposis colorectal carcinoma (HNPCC). However, the role of mismatch repair (MMR) proteins and microsatellite instability (MSI) in transitional cell carcinoma of the bladder is less clear. In our study, the expression of 2 MMR proteins and the frequency of MSI in Transitional cell carcinoma of the bladder (TCC) were investigated. One hundred eleven patients with TCC of the bladder were studied, with complete clinicopathological data (median follow up of 5 years, range 5-16 years). Immunohistochemistry was used to detect the expression levels of hMLH1 and hMSH2. Microsatellite analysis for 14 loci (10 loci from the Bethesda consensus panel and the repeats in the TGFbetaR2, BAX, hMSH3 and hMSH6 genes) was performed on 84 tumors. Reduced expression of either MMR protein was seen in 26 of 111 tumors (23%). Reduced expression was seen more commonly in muscle invasive (p<0.03) and high grade TCC (p<0.03) than in superficial, low grade tumors. By 5 years, reduced expression of either MMR protein was associated with fewer recurrences of superficial tumors (p=0.015) and fewer relapses in all tumors (p=0.03), compared to tumors with normal expression. Nine tumors had reduced expression of both MMR proteins, analysis which suggests a synergistic reduction in expression (p=0.001). MMR expression was related to patient age, younger patients being more likely to have reduced MMR expression than older patients (p<0.01). MSI was seen at multiple loci in 1 tumor (1%) and at a single locus in 6 tumors (7%). MSI was not associated with MMR expression. Our findings indicate that reduced expression of the MMR proteins may have an important contribution in the development of a subset of TCCs and suggest a potential role for MMR expression as prognostic indicators.

[Polymerase chain reaction in the urinary diagnosis of bladder cancer]

The polymerase chain reaction (PCR) is a highly sensitive and specific method for the detection of genetic material. Over the last few years, this method has been used increasingly for the molecular detection of disease. This report demonstrates the use of PCR in the diagnosis of bladder cancer. The principles of the method are shown by describing the detection of p53, CD44 and telomerase, as well as in microsatellite analysis.

[Non-invasive urinary diagnosis of bladder cancer. What do we know?]

Although the current system of classifying bladder cancer by stage and histological grade is very useful, it is still difficult to predict the natural progression of the disease either with or without therapy. Cystoscopy and urine cytology are currently the gold standards in the monitoring and diagnosis of bladder cancer. Classical urine cytology is, however, at least in the diagnosis of G1-tumors, characterized by a relatively low sensitivity. In the last few years, the molecular biological investigation of the basic mechanisms involved in carcinogenesis has provided a host of markers which are of potential diagnostic value for bladder cancer. We provide a current, comprehensive review of the literature on bladder tumor markers and summarize their diagnostic and prognostic potential. At present, no diagnostic marker with a comparable sensitivity and specificity to cystoscopy exists, given that cystoscopy has never been evaluated. The combined analysis of several tumor markers seems to be the most promising approach as an adjunct to cystoscopy. Moreover, the increasing simplification of test systems will increase their acceptance by clinicians.

DNA cytometric features in biopsies of TaT1 urothelial cell cancer predict recurrence and stage progression more accurately than stage, grade, or treatment modality

OBJECTIVES

To compare retrospectively the predictive value for recurrence and stage progression of DNA ploidy and S-phase fraction by flow cytometry and highly automated ultrafast image cytometry (ICM) in biopsies of TaT1 urothelial cell carcinomas (UCCs) of the urinary bladder with stage, grade, other pathologic features, and treatment.

METHODS

Three experienced pathologists reviewed the stage and grade of 228 UCCs; 193 (85%) consensus cases were analyzed further. We had enough material for single-cell suspensions for both flow cytometry and ICM in 183 cases (94.8%). The 2001 European Society for Analytical Cellular Pathology standards for DNA ICM were followed. The predictive value of DNA features, classic prognosticators (stage, grade, carcinoma in situ, multicentricity), and treatment modality for recurrence and stage progression were analyzed with univariate (Kaplan-Meier) survival and multivariate (Cox model) regression analysis. Ta and T1 cases were analyzed separately.

RESULTS

Of the 228 cases, 88 (51.5%) recurred and 13 (7.6%) progressed. On univariate analysis, most of the DNA features studied were statistically significant. Treatment modality and grade were only prognostic for progression (not for recurrence) and only in Ta cases. On multivariate analysis, DNA ICM features performed best; the strongest recurrence predictor for Ta UCC was a DNA index (DI) of 1.0 versus all others, and for T1 UCC, a DI of less than 1.3 versus 1.3 or greater. The best stage progression predictor for Ta UCCs was a DI of 1.0 plus an S-phase fraction of less than 10%, and for T1 UCCs, a DI of less than 1.3 versus 1.3 or greater. With multivariate analysis, sex, age, grade, carcinoma in situ, multicentricity, and treatment modality were excluded once the DNA ICM features were selected.

CONCLUSIONS

DNA image cytometric features predict recurrence and stage progression in TaT1 UCC biopsies more accurately than classic prognostic factors, independent of treatment modality.

Mutations of the D310 mitochondrial mononucleotide repeat in primary tumors and cytological specimens

A mononucleotide repeat (D310) in mitochondrial DNA has been recently identified as a mutational hot spot in primary tumors. We analyzed 56 tumors for insertion/deletion mutations in the D310 repeat. A total of 13 mutations were detected. The highest frequency of mutations was found for cervical cancer, followed by bladder tumors, breast cancer and endometrial neoplasia. No alterations were observed in four patients suspected of malignancy but without evidence of malignant tumor. We detected identical changes in four of four urine sediments from patients with bladder cancer and in three of three fine needle aspirates of patients with breast cancer. Our results indicate that D310 abnormalities are detectable in cytology specimens from patients with cancer and support the notion that D310 analysis may represent a new molecular tool for cancer detection.

Sensitivity and specificity of commonly available bladder tumor markers versus cytology: results of a comprehensive literature review and meta-analyses

OBJECTIVES

To determine the clinical utility of urine-based bladder tumor markers (UBBTMs) and cytology in the treatment of patients with transitional cell carcinoma on the basis of their statistical performance.

METHODS

A comprehensive literature review was performed using Medline (1966 to current) and other search engines. Data regarding the statistical performance of UBBTMs were double extracted and rectified. Studies addressing comparable patient populations were combined and hierarchical Bayesian meta-analyses performed to calculate the sensitivity and specificity of commonly used UBBTMs, as well as urinary cytology. Patient populations were stratified by tumor stage and grade when data were presented in an extractable fashion.

RESULTS

The literature review yielded 54 publications, 338 distinct patient groups (controls, screening population, patients with cancer, strata based on grade and stage) and more than 10,000 patients. The number of groups varied from 1 to 18, and the number of patients ranged from less than 100 to more than 1500 for the various markers. All UBBTMs have better sensitivity compared with cytology, especially for low-grade/stage disease, but do not match cytology regarding specificity. In patients with grade 1 and 2 tumors, several UBBTMs are significantly superior statistically in terms of sensitivity compared with cytology. The sensitivity for transitional cell carcinoma in situ (Tis) is surprisingly poor for all UBBTMs.

CONCLUSIONS

UBBTMs can be used for follow-up of low-grade/stage tumors but should not replace cystoscopy. All UBBTMs have better sensitivity than cytology and could potentially replace routine cytology during patient follow-up.

Molecular detection approaches for smoking associated tumors

Smoking is directly responsible for approximately 90% of lung cancers and is also strongly associated with cancers of the head and neck, esophagus and urinary bladder. Our growing understanding of the molecular changes that underlie cancer progression has contributed to the development of novel molecular approaches for the detection of cancer. In this study, we review a number of recent studies that have used molecular techniques to detect neoplastic DNA from lung, head and neck, esophagus and bladder cancer. The majority of these approaches are based on polymerase chain reaction (PCR) based assays. These PCR-based techniques can detect a few clonal cancer cells containing a specific DNA mutation, microsatellite alteration, or CpG island methylation among an excess background of normal cells. The ability to accurately detect a small number of malignant cells in a wide range of clinical specimens including sputum, saliva, bronchoalveolar lavage fluid, urine, serum, plasma, or tissue has significant implications for screening high-risk individuals (such as cigarette smokers) for cancer.

Evaluation of breast cancer metastases in pleural effusions by molecular biology techniques

The aim of this study was to evaluate the presence of allelic loss in chromosomal regions previously described as exhibiting loss of heterozygosity (LOH) during breast carcinogenesis, in pleural effusions of breast cancer patients. LOH was analyzed in three loci (1p32, 7q31, and 17q21). We studied 41 samples of pleural effusions from breast cancer patients (24 positive for neoplastic cells, 14 suspected, and 3 negative cases) and breast tissues from the patients (primary tumors and nonneoplastic adjacent tissue). DNA was extracted from pleural effusions, primary tumor, and adjacent normal tissue. LOH was evaluated by polymerase chain reaction assay and was observed in 38% of pleural effusions positive for neoplastic cells, and in 36% of suspected cases where morphology only did not allow the diagnosis of malignancy. We conclude that LOH analysis in pleural effusions of breast cancer patients is able to identify metastases in cases where morphologic analysis becomes difficult.

Non-invasive molecular detection of bladder cancer recurrence

Transitional cell carcinoma (TCC) is the most common bladder tumor and approximately 90% of bladder TCC are superficial at initial diagnosis. High recurrence rate and possible progression to muscle invasive disease that is eventually indicated for radical cystectomy are established features of these tumors. Therefore, reliable predictors of tumor recurrence are of critical importance for management of superficial bladder TCC. Successful molecular diagnosis of bladder cancer by detecting genetic lesions: loss of heterozygosity (LOH) or microsatellite instability (MSI) in cells exfoliated in urine has been reported by several groups including ours. The aim of our study was to evaluate the predictive potential of microsatellite analysis of cells exfoliated in urine in the detection of superficial bladder TCC recurrence. We studied 47 Caucasian patients with confirmed superficial bladder TCC (37 pTa, 10 pT1) at initial diagnosis. Blood samples were obtained once from every patient whereas urine samples were collected before each cystoscopy (initial and follow-up). Matched DNAs from blood and urine were subjected to microsatellite analysis in a blinded fashion. The follow-up period ranged 12-48 months after tumor resection. Microsatellite analysis correctly identified 94% (44/47) of primary tumors and 92% (12/13) of tumor recurrences. Interestingly enough, 75% (9/12) of tumor recurrences were molecularly detected 1-9 months before cystoscopic evidence of recurrent disease. This study demonstrated clearly that not only urine microsatellite analysis reliably detected superficial bladder tumors, but also was a reliable test for detecting and predicting tumor recurrence in Caucasian patients. These results warrant multicenter randomized trials.

Clonality of multifocal urothelial carcinomas: 10 years of molecular genetic studies

Multifocal occurrence and frequent recurrence are characteristic features of urothelial carcinomas of both the urinary bladder and the upper urinary tract. To describe the clonal nature of these tumors, 2 theories have been proposed. The monoclonality hypothesis describes the multiple tumors as descendants of a single genetically transformed cell spreading throughout the urothelium. In contrast, field cancerization caused by carcinogen exposure of the urothelium may lead to independent development of synchronous or metachronous nonrelated tumors at different sites of the urothelial tract. In the last 10 years, a multitude of molecular genetic studies have investigated the clonality of multifocal urothelial carcinomas. The majority of studies revealed a monoclonal origin of the multiple tumors. However, most of these studies investigated advanced invasive carcinomas. A small but significant proportion of multifocal urothelial carcinomas appear to arise from different clones, supporting the field-cancerization hypothesis. Oligoclonal tumors might be more common in precursor lesions and early tumor stages. The frequent monoclonality found in patients with advanced tumors could be due to outgrowth of 1 tumor cell clone with specific genetic alterations. Two important mechanisms appear to be important for the spread of malignant cells: intraluminal seeding and intraepithelial migration. Investigation of the entire urothelial lining in patients with urothelial tumors should provide further insight into the development of multifocal urothelial carcinomas.

Plasma Nucleic Acids in the Diagnosis and Management of Malignant Disease

Background: There is a need for development of molecular markers of cancer that can be used clinically for the detection, prognostication, and monitoring of cancer. Recently, there has been much interest in the potential use of nucleic acid markers in plasma and serum for this purpose.

Approach: We reviewed published literature up to 2002 on the topic, with a particular emphasis on reports published between 1996 and 2002.

Content: The nucleic acid markers described in plasma and serum include oncogene mutations/amplifications, microsatellite alterations, and gene rearrangements. Such markers have been described in many cancer types, including lung, colon, and breast. Epigenetic alterations, such as aberrant promoter methylation, have been identified in plasma and serum. Viral nucleic acid markers, such as Epstein–Barr virus DNA in plasma and serum, are reviewed in detail with regard to their application to virus-associated cancers such as nasopharyngeal carcinoma and various lymphomas. More recently, mitochondrial DNA and tumor-related mRNAs have been identified in plasma and serum from patients with several types of tumors.

Conclusions: Circulating nucleic acids are an emerging class of molecular tumor markers. Their wide applicability and clinical relationship with the malignant state will likely grant them increasing clinical importance in the near future.

Detecting rare mutations associated with cancer risk

For more than a decade, investigators have been searching for a means of determining the risk of individuals developing cancer by detecting rare oncogenic mutations. The accumulation of mutations and the clonal evolvement of tumors provide opportunities for monitoring disease development and intervening prior to the presentation of clinical symptoms, or determining the risk of disease relapse during remission. A number of techniques, mostly polymerase chain reaction (PCR)-based, have been developed that enable the detection of rare oncogenic mutations within the range of 10(-2) to 10(-4) wild-type cells. Only a handful of procedures enable the detection of intragenic single base mutations at one mutant in 10-6 or better. These ultra-sensitive mutation detection techniques have produced some interesting results regarding single base mutation spectra and frequencies in p53, Harvey-ras, N-ras, and other reporter genes and DNA sequences in human tissues. Although there is evidence that some individuals may harbor cells or clones expressing genomic instability, the connection with the processes of carcinogenesis is still tenuous. There remains a need for rigorous epidemiological studies employing these ultra-sensitive mutation detection procedures. Since genomic instability is considered key to tumor development, the relevance of the detection of hypermutable clones in individuals is discussed in the context of cancer risk.

Deficiency of a novel mismatch repair activity in a bladder tumor cell line

We demonstrate here that a cell line derived from a bladder cancer is defective in strand-specific mismatch repair. The mismatch repair deficiency in this cell line is associated with microsatellite instability and blocks an early step in the repair pathway. Since the addition of a known mismatch repair component hMutSalpha, hMutSbeta, hMutLalpha, replication protein A or proliferating cellular nuclear antigen could not restore mismatch repair to the mutant extract, the bladder tumor cell line is likely to be defective in an uncharacterized repair component. However, the repair in the mutant extract could be complemented by a partially purified activity derived from HeLa nuclear extracts. Therefore, in addition to revealing that a loss of mismatch repair function is associated with bladder cancer, this study provides information implicating a new mismatch repair activity.

Mutation rate and specificity analysis of tetranucleotide microsatellite DNA alleles in somatic human cells

We have systematically varied microsatellite sequence composition to determine the effects of repeat unit size, G+C content, and DNA secondary structure on microsatellite stability in human cells. The microsatellites were inserted in frame within the 5' region of the herpes simplex virus thymidine kinase (HSV-tk) gene. The polypyrimidine/polypurine microsatellites displayed enhanced S1 nuclease sensitivity in vitro, consistent with the formation of non-B-form DNA structures. Microsatellite mutagenesis studies were performed with a shuttle vector system in which inactivating HSV-tk mutations are measured after replication in a nontumorigenic cell line. A significant increase in the HSV-tk mutation frequency per cell generation was observed after insertion of [TTCC/AAGG]9, [TTTC/AAAG]9, or [TCTA/AGAT]9 sequences (P <or= 0.0002), relative to the HSV-tk gene control. We observed that the G + C content of the microsatellite may affect mutagenesis, as the mean microsatellite mutation rates of the [TTTC/AAAG]9 and [TCTA/AGAT]9 alleles were sevenfold and 11-fold higher, respectively, than the [TTCC/AAGG]9 allele. A bias toward expansion mutations was noted for the majority of clones bearing the [TTCC/AAGG]9 allele as well as a [TC/AG]17 microsatellite of similar allele length. The mean microsatellite mutation rate of the [TTCC/AAGG]9 allele did not differ significantly from that for a [TC/AG]11 allele, demonstrating that these tetranucleotide and dinucleotide alleles are of equivalent stability. It is known that microsatellite mutagenesis is affected by the number of repeat units within an allele. Our data suggest that additional biochemical factors may regulate both the rate and specificity of somatic cell microsatellite mutagenesis.

Impact of the Human Genome Project on the clinical management of sporadic cancers

The publication of the human genome sequence has provided a new basis for cancer research. Molecular analysis of single cancer genes in isolation may lead to an underestimation of the impact of networks of intertwined genes in molecular cancer pathology. However, new technologies such as DNA microarrays or microchips will enable the detection of global gene-expression profiles--already described for lymphomas, acute leukaemias, and various solid tumours--and may help to overcome some of the limitations of gene function analysis. In addition, DNA microchip data banks may uncover new genes that are relevant to the molecular pathology of specific cancers and trigger detailed analysis of their function. Clinically, microchips will enable us to identify new molecular cancer markers or marker profiles of prognostic and predictive value, since global gene-expression patterns can highlight molecular tumour characteristics that relate to clinically distinct entities within heterogeneous cancers, such as non-Hodgkin lymphomas or breast cancer. However, before its promise can be realised, all molecular information stemming from the Human Genome Project will need to be tested for its clinical relevance in appropriate cancer trials; this presents a formidable but important challenge.

DNA alterations in body fluids as molecular tumor markers for urological malignancies

OBJECTIVES

DNA-based tumor markers are characterized by unique specificity rendering them an attractive target for molecular diagnosis of cancer in body fluids like blood serum/plasma and urine. Both cell-free tumor DNA circulating in plasma/serum and cellular tumor DNA are detectable by minimally invasive measures.

METHODS

Three main detection methods, microsatellite analysis, mutation analysis in genomic or mitochondrial DNA and gene promoter hypermethylation analysis are applied. Detection of gene promoter hypermethylation by methylation-specific PCR enables the best methodical sensitivity requiring a ratio of tumor DNA within normal DNA of less than 1:1000.

RESULTS/CONCLUSIONS

Tumor DNA derived from renal cell carcinoma, bladder cancer or prostate cancer is detectable in considerably more than 50% of plasma/serum samples and more than 70% of urine samples from these patients. Because the targeted DNA alterations are absent or very rare in controls, the specificity of DNA-based tumor detection methods reaches almost 100%. Although the methodology currently is experimental, automatization will make it easier and less expensive. This review is focused on the potential clinical value of DNA-based analysis of body fluids for the initial diagnosis and the follow-up of urologic cancer patients.

Microsatellite instability and its relevance to cutaneous tumorigenesis

Increasing evidence suggests that human tumors sequentially accumulate multiple mutations that cannot be explained by the low rates of spontaneous mutations in normal cells (2-3 mutations/cell). The mathematical models estimate that for the solid tumors to develop, as many as 6-12 mutations are required in each tumor cell. Therefore, to account for such high mutation rates, it is proposed that tumor cells are genetically unstable, i.e. they have genome-wide mutations at short repetitive DNA sequences called microsatellites. Microsatellite repeats are scattered throughout the human genome, primarily in the non-coding regions, and can give rise to variants with increased or reduced lengths, i.e. microsatellite instability (MSI). This instability has been reported in an increasing number of cutaneous tumors including: melanocytic tumors, basal cell carcinomas and primary cutaneous T-cell lymphomas. Moreover, MSI has been observed in skin tumors arising in the context of some hereditary disorders such as Muir-Torre syndrome, Von Recklinghausen's disease and disseminated superficial porokeratosis. While MSI in some of these disorders reflects underlying DNA replication errors, the mechanism of instability in others is still unknown. Thus far, MSI is considered to be a distinct tumorigenic pathway that reveals surprising versatility. The ramifications for cutaneous neoplasms warrant further investigation.