Molecular detection of primary bladder cancer by microsatellite analysis

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.

Chorionic gonadotropin beta-subunit and core fragment in bladder cancer: mRNA and protein expression in urine, serum and tissue

OBJECTIVES

Many transitional cell carcinomas (TCC) of the bladder express the beta-subunit (CGbeta) of chorionic gonadotropin (CG), and elevated serum levels occur especially in advanced disease. We have compared the diagnostic utility of various methods for detecting CG and CGbeta expression at the protein and mRNA level.

METHODS

We used RT-PCR to detect CGbeta mRNA in urinary cells and highly sensitive immunoassays to determine CG and CGbeta in serum and the core fragment of CGbeta (CGbetacf) in urine from patients under follow-up for bladder cancer. Tissue expression was studied by immunohistochemistry.

RESULTS

CGbeta mRNA was detected in urinary cells in 50% (n=84) of the cancer cases and in none of the healthy controls (n=15). Positive staining for CGbeta in tissue samples was observed not only in 30% (n=96) of the TCC cases, but also in 5 of 20 histologically benign samples from TCC patients, and in 10 of 21 samples from benign bladder diseases. Serum and urinary concentrations of CGbeta were elevated in 29% (n=66) and 8% (n=72), respectively, while serum CG was elevated in 18% of the TCC patients. Urinary CGbetacf concentrations were higher in invasive (T1-T4) than superficial (T in situ and Ta) tumors (p=0.037), in cases positive for CGbeta mRNA (p=0.03) and cases with suspicious or malignant urinary cytology (p=0.002). The ratio of urinary to serum concentration of CGbeta showed the strongest correlation with tumor stage (p<0.00001), grade (p<0.00001), and staining for CGbeta (p=0.019).

CONCLUSIONS

Although CGbeta expression may occur in benign bladder epithelium, CGbeta mRNA in urinary cells is a potential marker of bladder cancer. Urinary and serum CGbeta have low sensitivity in early disease, but the urine/serum ratio appears to indicate local release of CGbeta into urine. Further studies are needed to evaluate the clinical usefulness of different forms of CGbeta expression.

Microsatellite alterations in human bladder cancer: detection of tumor cells in urine sediment and tumor tissue

OBJECTIVES

Bladder cancer is the result of clonal expansion of cancer cells in which multiple genetic alterations have occurred. Loss of heterozygosity (LOH) studies have demonstrated that alterations in microsatellite regions are common in bladder cancer. This observation offers the possibility of early tumor detection by examining the DNA of urinary sediment.

METHODS

We investigated alterations of 17 microsatellite loci in urinary bladder carcinomas of different stages and grades. Per locus, 19-30 specimens were evaluated. DNA was isolated from tumor specimens, urinary sediment and peripheral blood lymphocytes. DNA fragments of 17 microsatellite loci were amplified by PCR and analyzed for genomic alterations.

RESULTS

Microsatellite alterations were detected in tumor tissue and urine sediment from 27 out of 31 patients (87%). Urine sediment analysis alone proved positive in 24 out of 31 patients (77%). The type of lesions most frequently detected was LOH (74% of all alterations), followed by length alteration (24%) and additional alleles (2%). On average, the alteration frequency was 22% per locus. The loci at chromosomes 9 and 18 proved most informative. No alterations were found in grade I tumors. The study revealed a correlation between microsatellite alterations and the respective grades and stages of the tumors. Average alteration frequencies per locus were: 27.4% in grade III versus 19.3% in grade II tumors, 26.5% in invasive versus 12.3% in superficial tumors.

CONCLUSIONS

Our results demonstrate that microsatellite alterations are common in bladder cancer and that analysis of genomic instabilities in urine samples should be further evaluated as a method for bladder cancer screening in a high-risk group. Especially, when a set of microsatellites is used that shows a high probability of detecting alterations and allows easy handling, this could be an alternative or a completion to currently available methods.

Prospects for chemoprevention of cancer

The recent progress in molecular biology and pharmacology has increased the likelihood that cancer prevention will rely increasingly on interventions collectively termed 'chemoprevention'. Cancer chemoprevention is the use of agents to inhibit, delay or reverse carcinogenesis. A number of potential targets for chemoprevention have recently been identified. Many classes of agents including antioestrogens, anti-inflammatories, antioxidants and other diet-derived agents have shown a great deal of promise. In this review, we will begin by describing the general classes of chemopreventive agents and the mechanisms by which these agents act. We will then describe the opportunities that presently exist for chemoprevention of specific cancers.

Emerging molecular markers of cancer

Alterations in gene sequences, expression levels and protein structure or function have been associated with every type of cancer. These 'molecular markers' can be useful in detecting cancer, determining prognosis and monitoring disease progression or therapeutic response. But what is the best way to identify molecular markers and can they be easily incorporated into the clinical setting?

Frequent loss of heterozygosity in chromosomal region 9pter-p13 in tumor biopsies and cytological material of uterine cervical cancer

Using polymerase chain reaction-based microsatellite analysis we examined 40 cases, tumor biopsies and cytological material, of early stage cervical cancer and 20 healthy donors. Loss of heterozygosity (LOH) was detected in 35 out of 40 cases (87.5%), located on 9pter-p13 (67.5%), 9q32-34 (17.5%), 13q12 (32.5%), 17p13 (0%) and 17q11-q22 (12.5%). Microsatellite instability (MIN) phenotype was found in three out of 40 cases (7.5%). The accuracy in LOH and MIN detection in cytological material compared to tumor biopsies was 91.5 and 86.0%, respectively. None of the specimens of healthy donors exhibited any genetic alteration. Our data suggest that microsatellite analysis in cytological material could be used for the early detection of cervical cancer.

Telomerase: its clinical relevance in the diagnosis of bladder cancer

More than 50 years ago, Papanicolaou recognized the importance of a non-invasive technique for the diagnosis and follow-up of patients with carcinoma of the urinary bladder. Cystoscopy, however, has remained the 'gold standard' since no currently available non-invasive method can compete with cystoscopy's sensitivity and specificity. The detection of the ribonucleoprotein telomerase or the telomerase subunits human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) in urine samples offer new diagnostic perspectives. The present article presents a review of publications in the literature and evaluates their clinical relevance. The experimental studies reported to date are very promising and show that telomerase exactly fulfils the requirements for a good diagnostic marker for carcinoma of the urinary bladder. The diagnostic application remains in an experimental stage and telomerase is still several steps away for routine use as a clinical parameter. The remaining steps leading to its routine clinical application will be discussed.

Molecular abnormalities in lung carcinogenesis and their potential clinical implications

Development of lung cancer is multistep and requires accumulation of multiple genetic and epigenetic alterations. Modern molecular technology has facilitated a rapid and effective identification of these genetic alterations as well as epigenetic alterations. The determination of molecular alterations in the early tumorigenic process of the lung will not only extend our understanding of the underlying biology but also provide molecular markers for cancer risk assessment, early detection, and molecular classification. In this article, I will discuss the common molecular abnormalities in lung cancer and how these abnormalities may be used as biomarkers in clinical practice.

Gene mutation as a target for early detection in cancer diagnosis

The increasing number of genetic aberrations implicated in the development of human cancer has prompted a search to detect them at the earliest possible stage of their formation. Of the many such genetic changes identified thus far, relatively few meet the standard for markers in early diagnosis and prognosis, namely that the genetic modifications occur during the early onset phase of cancer development. Parallel to the increasing number of such genes is the growing availability of technologies using more powerful and cost-efficient methods that enable mass screening for genetic alterations. The purpose of this review is to summarize the currently available genes that can serve as markers for early detection of cancers and methods that allow their detection.

Sensitive detection of transitional cell carcinoma of the bladder by microsatellite analysis of cells exfoliated in urine

Transitional cell carcinoma (TCC) is the most common bladder tumor. Urine cytology can identify most high-grade tumors but sensitivity is lower if one includes lesions of all grades. Microsatellite marker alterations have been found in many tumor types including bladder cancer and have been used to detect cancer cells in body fluids including urine. The aim of our study is to further evaluate feasibility and sensitivity of microsatellite analysis to detect bladder cancer cells in urine. We studied 55 individuals: 21 with symptoms suggestive of bladder cancer, 23 patients with previous history of TCC and 11 healthy subjects. Genomic DNA was extracted from blood lymphocytes, urine sediment, bladder washings and tumor or normal bladder mucosa. Twenty highly informative microsatellite markers were analyzed for loss of heterozigosity (LOH) and microsatellite instability (MIN) by polymerase chain reaction. Microsatellite analysis of urine identified 33 of 34 (97%) patients with either primary or tumor recurrence, whereas urine cytology identified 27 of 34 (79%) patients (p = 0.0001). Detection of microsatellite abnormalities improved the sensitivity of detecting low-grade and/or stage bladder tumor: from 75-95% for grades G1-G2 and from 75-100% for pTis-pTa tumors. Bladder washings from 25 patients were also analyzed, and in all cases results were identical to those obtained from voided urine. None of the 16 patients without evidence of TCC showed LOH and/or MIN in urine samples or bladder washings. Interestingly, in a patient with persistent bladder mucosa abnormalities, microsatellite alterations were demonstrated 8 months before the histopathologic diagnosis of tumor recurrence. These results further indicate that microsatellite marker analysis is more sensitive than conventional urine cytology in detecting bladder cancer cells in urine and represents a potential clinical tool for monitoring patients with low-grade/stage TCC.

Genetic heterogeneity in saliva from patients with oral squamous carcinomas: implications in molecular diagnosis and screening

We performed microsatellite analysis at chromosomal regions frequently altered in head and neck squamous carcinoma on matched saliva and tumor samples from 37 patients who had oral squamous carcinoma. The results were correlated with the cytologic findings and traditional clinicopathologic factors to assess the diagnostic and biological potential of these markers. Our data showed that 18 (49%) of the saliva samples and 32 (86%) of the tumors had loss of heterozygosity (LOH) in at least one of the 25 markers studied. In saliva, the combination of markers D3S1234, D9S156, and D17S799 identified 13 (72.2%) of the 18 patients with LOH in saliva (P < 0.001). For tumors, markers D3S1234, D8S254, and D9S171 together identified 27 (84.3%) of the 32 tumors with LOH at any of the loci tested (P < 0.001). Eleven (55%) of the 20 saliva samples with cytologic atypia and seven (35%) of the 17 specimens without atypia had LOH. Significant correlation between LOH in tumor at certain markers and smoking and alcohol use was found. Our results indicate that: 1) epithelial cells in saliva from patients with head and neck squamous tumorigenesis provide suitable material for genetic analysis; 2) combined application of certain markers improves the detection of genetic alteration in these patients; 3) clonal heterogeneity between saliva and matching tumor supports genetic instability of the mucosal field in some of these patients; and 4) LOH at certain chromosomal loci appears to be associated with smoking and alcohol consumption.

A comparison between microsatellite analysis and cytology of urine for the detection of bladder cancer

We have studied, in a blinded fashion, cytology and microsatellite analysis on urine sediments of 143 Chinese with or without bladder lesions. Microsatellite analysis succeeded in all 143 individuals, while cytology could not be performed on 42 subjects due to insufficient urine samples. Both microsatellite analysis and routine urine cytology succeeded in 81 bladder cancer patients. Seventy-three patients (90%) were identified by microsatellite analysis, while only 41 patients (51%) were identified by cytology. However, four patients were identified by routine cytology but not by microsatellite analysis. Our results proved that microsatellite analysis is more sensitive than routine cytology but the two methods are complementary to each other.

Telomerase activity detected by quantitative assay in bladder carcinoma and exfoliated cells in urine

Early diagnosis is one of the most determining factors for patient survival. The detection of telomerase activity is a potentially promising tool in the diagnosis of bladder and other types of cancer due to the high expression of this enzyme in tumor cells. We carried out a quantitative evaluation of telomerase activity in urine samples in an attempt to determine a cut-off capable of identifying cancer patients. Telomerase activity was quantified by fluorescence TRAP assay in urine from 50 healthy volunteers and in urine and bioptic tumor samples from 56 previously untreated bladder cancer patients and expressed in arbitrary enzymatic units (AEU). Telomerase activity in urine ranged from 0 to 106 AEU (median 0) in healthy donors and from 0 to 282 AEU (median 87) in patients with cancer. A telomerase expression higher than the cut off value determined by receiver operating characteristic (ROC) analysis was observed in 78% of cases, regardless of tumor grade and in 71% (15/21) of cases of nonassessable or negative cytology. The quantitative analysis of telomerase activity in urine enabled us to define cut-off values characterized by different sensitivity and specificity. Cytologic and telomerase determination, used sequentially, enabled us to detect about 90% of tumors.

A possible noninvasive method for the detection of bladder cancer in patients: microsatellite analysis of free DNA in urine and blood

Six microsatellite markers were selected to detect shifts or loss of heterozygosity (LOH) in urine, serum, and plasma samples of 44 bladder cancer patients. After centrifugation at 15,000 g, we used supernatants for DNA analysis only. Tumor specimens were obtained by transurethral resection (TUR). Genetic alterations were detected in 33 of the 44 bladder tumors (75%). After polymerase chain reaction (PCR), DNA was detectable in 96% of all body fluid samples. Twenty-six percent of the detected microsatellite alterations of free DNA were tumor-specific, but 82% of all microsatellite changes of the tumors could be detected in body fluids. The study indicates that the simultaneous and multiple investigations of highly specific microsatellite markers could have a clinical relevance as a noninvasive tool for diagnosis and screening of bladder cancer. However, new ways for the sensitive DNA isolation of body fluids are needed.

Mitochondrial mutations in early stage prostate cancer and bodily fluids

We recently demonstrated the existence of specific patterns of somatic mitochondrial DNA (mtDNA) mutations in several cancers. Here we sought to identify the presence of mtDNA mutations in prostate cancer and their paired PIN lesions. The D-loop region, 16S rRNA, and the NADH subunits of complex I were sequenced to identify mtDNA mutations in 16 matched PIN lesions and primary prostate cancers. Twenty mtDNA mutations were detected in the tumor tissue of three patients. Identical mutations were also identified in the PIN lesion from one patient. This patient with multiple point mutations also harbored a high frequency of microsatellite instability (MSI-H) in nuclear mononucleotide repeat markers. Remarkably, identical mutations were also detected in all (3/3) matched urine and plasma samples obtained from these patients. Although mitochondrial mutations are less common in prostate adenocarcinoma, they occur early in cancer progression and they can be detected in bodily fluids of early stage disease patients. The identification of MtDNA mutations may complement other early detection approaches for prostate cancer.

Genetic mapping and DNA sequence-based analysis of deleted regions on chromosome 16 involved in progression of bladder cancer from occult preneoplastic conditions to invasive disease

Histologic and genetic mapping with 30 hypervariable markers mapped to chromosome 16 were performed on 234 DNA samples of five cystectomy specimens from patients with invasive bladder cancer. Allelic losses of individual markers were related to microscopically identified precursor conditions in the entire bladder mucosa and invasive cancer. Their significance for the development and progression of neoplasia from in situ preneoplastic conditions to invasive disease was analysed by the nearest neighbor algorithm and binomial maximum likelihood analysis. Using this approach we identified five distinct regions of allelic losses defined by their flanking markers and predicted size as follows. p13.3(D16S418-D16S406, 1.2 cM), p13.1(D16S748-D16S287, 12.9 cM), q12 1(D16S409-D16S514, 24.0 cM), q22.1 (D16S496-D16S515, 5.4 cM), and q24 (D16S507-D16S511, 5.9 cM and D16S402-D16S413, 17.4 cM). The regions mapping to p13.1 and q24 were involved in early intraurothelial phases of bladder neoplasia such as mild to moderate dysplasia. On the other hand the deleted region mapping to p13.3 was involved in progression of severe dysplasia/carcinoma in situ to invasive bladder cancer. Testing of markers that exhibited statistically significant LOH in relation to progression of neoplasia from precursor conditions to invasive cancer on 28 tumors and voided urine samples from 25 patients with bladder cancer revealed that q12.1 showed LOH in 46.4% of tumor and 32.0% of voided urine samples. The LOH of a single marker D16S541 could be detected in approximately 28% of tumors and 20% of voided urine samples of patients with bladder cancer. These data imply that the deleted region centered around marker D16S541 spanning approximately 10 cM and flanked by D16S409 and D16S415 contains a novel putative tumor suppressor gene or genes playing an important role in the development of human bladder cancer. To facilitate more precise positional mapping and identification of pathogenetically relevant genes, we analysed of human genome contig and sequence databases spanning the deleted regions. Multiple known candidate genes and several smaller gene-rich areas mapping to the target regions of chromosome 16 were identified.

Microsatellite analysis--DNA test in urine competes with cystoscopy in follow-up of superficial bladder carcinoma: a phase II trial

BACKGROUND

It has been shown that microsatellite analysis (MA) is able to detect bladder carcinoma in urine. Relatively small groups of patients often with high stage and grade disease were investigated. However, greater than 85% of cystoscopies are performed for follow-up of superficial bladder carcinoma. The authors evaluated this DNA-based method in a group of consecutive patients in follow-up after transurethral resection of superficial disease.

METHODS

Matched blood and urine samples from 109 patients were obtained before cystoscopy and subjected to MA. The BTA stat test (Bard Diagnostic Sciences, Inc., Redmond, WA) and cytology were used for comparison.

RESULTS

Sixteen patients were excluded: the DNA was of insufficient quality for 7 patients and leukocyte abundance rendered the result of MA unreliable for 9 patients. For the remaining 93 patients, MA detected 18 of the 24 recurrent tumors. The six undetected tumors were small pTaG1 lesions for which immediate surgery was not necessary. Conversely, 5 of 9 patients with a positive MA and a negative cystoscopy had a tumor recurrence within 6 months after urine collection. In contrast, a recurrence occurred in only 7 of 60 patients who were negative in both MA and cystoscopy (P = 0.006). The MA (74%) appeared more sensitive than the BTA stat test (56%) or urine cytology (22%).

CONCLUSIONS

Microsatellite analysis is a DNA test in urine that reliably signals the presence of recurrent bladder carcinoma, sometimes even before cystoscopic evidence of the disease. This noninvasive diagnostic tool has the potential to replace cystoscopy in many cases. The authors' results warrant the need for randomized trials.

Molecular detection of cervical intraepithelial neoplasia and cervical carcinoma by microsatellite analysis of Papanicolaou smears

Carcinoma of the uterine cervix is one of the most common malignancies worldwide, yet it is clearly preventable by population screening. The Papanicolaou (Pap) smear has proved to be the most successful test for the detection of precancerous lesions and is largely responsible for the reduction of cervical cancer mortality and morbidity rates. However, the Pap smear is not perfect; false-negative results of various rates are reported. To improve the diagnostic efficacy of cervical cytology, we performed microsatellite analysis on paired Pap smear samples from cervical lesions. Nine microsatellite markers were chosen from chromosomal regions commonly displaying loss of heterozygostity (LOH) in cervical cancer and those displaying microsatellite instability (MI) in other squamous cell cancer. Microsatellite alterations were detected in 16/21 (76%) Pap smear DNA samples including 11 of 13 (85%) smears from invasive squamous cell carcinomas (SCCs) and 5 of 8 (63%) from squamous intraepithelial lesions (SILs). Microsatellite alterations detected in the Pap smear DNA were identical to those identified in seven paired primary tumors available for analysis. Moreover, this molecular approach detected genetic alterations in two cases apparently negative by cytologic examination. None (0/25) of the control patients displayed microsatellite alterations in paired Pap smears. Microsatellite analysis of cervical cytologic samples may provide a complementary method to analyze suspicious but not diagnostic cytologic samples further.

Chemoprevention of superficial bladder cancer

The development, evaluation and approval of promising agents for bladder cancer prevention (chemoprevention)depends upon the rational integration of four key components: a) Agents (pharmaceuticals, biologics and nutrients); b) Biomakers (intermediate endpoints that predict for clinical response and risk reduction; c) Cohorts (well defined high risk target populations d) Designs (efficient trial designs linked to the clinical phase of development). The promise of this overall strategy is the ability to conduct faster, smaller and more cost effective trials which incorporate validated surrogate endpoints rather than conventional clinical endpoints (cancer incidence, recurrence and survival). Current National Cancer Institute (NCI) phase III bladder cancer chemopreventive trials in progress are described. Since most patients with superficial (transitional cell) bladder cancer present with early disease (Ta, T1, Tis lesions) that frequently recurs and is easily accessible by serial cystoscopy and urine cytology, bladder cancer serves as a powerful clinical for conducting prevention trials of new agents for a tobacco related malignancy.

Circulating tumor-derived DNA may permit the early diagnosis of head and neck squamous cell carcinomas

A series of eight microsatellite loci were assayed for both loss of heterozygosity and new mutated alleles in 91 head and neck squamous cell carcinomas. In 58 cases, alterations were detected and used as markers for assaying the presence of circulating tumor-derived DNA in the patients' plasma. This was unambiguously detected in 17 cases. The probability of detecting circulating DNA was independent of tumor stage and was found to be present even in some individuals with stage I tumors. The presence of such DNA, however, could not be correlated with disease outcome or other significant clinical parameters, suggesting that it has no prognostic significance. The results indicate that circulating tumor-derived DNA could be used as a means of early diagnosis of head and neck tumors.

Biomarkers in monitoring for efficacy of immunotherapy and chemoprevention of bladder cancer with dimethylsulfoxide

This study correlated biomarkers expressed in tumor and epithelial field with clinical response and recurrence. Of 25 bladder cancer patients, 11 received 6 weeks of intravesical Bacille Calmette-Guerin (BCG), and 14 were treated weekly with intravesical dimethylsulfoxide (DMSO) for 4 weeks to further modulate biomarker expression. G-actin, DNA aneuploidy, and p300 tumor antigen were evaluated by quantitative fluorescence image analysis on uroepithelial cells from bladder wash samples prior to and immediately following treatment. Excluding patients who did not respond to BCG (and who had persistently abnormal p300 and DNA markers), recurrence correlated with persistent abnormal G-actin findings. Of patients who were G-actin negative following therapy, only 25% recurred during follow-up in contrast to 67% in patients who were positive (p < 0.03 by Fisher's exact test). The odds ratio for recurrence was 6.00 (95% confidence interval: 1.3-28.6). Cytosolic G-actin levels can be an important intermediate end point marker for chemoprevention.

Molecular tools in the detection of micrometastatic cancer cells--technical aspects and clinical relevance

The frequent failure to reduce the mortality due to epithelial cancers by common medical intervention results primarily from early dissemination of cancer cells, which is missed by conventional diagnostic procedures used for tumor staging. Individual carcinoma cells present in regional lymph nodes, blood or distant organs (e.g., bone marrow) can be detected by sensitive immunologic or molecular methods. Here, we review recently developed molecular assays for the detection of individual micrometastatic cancer cells and their clinical application in patients with epithelial tumors.

Mitochondrial genome instability in human cancers

Malfunction of mismatch repair (MMR) genes produces nuclear genome instability (NGI) and plays an important role in the origin of some hereditary and sporadic human cancers. The appearance of non-inherited microsatellite alleles in tumor cells (microsatellite instability, MSI) is one of the expressions of NGI. We present here data showing mitochondrial genome instability (mtGI) in most of the human cancers analyzed so far. The mtDNA markers used were point mutations, length-tract instability of mono- or dinucleotide repeats, mono- or dinucleotide insertions or deletions, and long deletions. Comparison of normal and tumoral tissues from the same individual reveals that mt-mutations may show as homoplasmic (all tumor cells have the same variant haplotype) or as heteroplasmic (tumor cells are a mosaic of inherited and acquired variant haplotypes). Breast, colorectal, gastric and kidney cancers exhibit mtGI with a pattern of mt-mutations specific for each tumor. No correlation between NGI and mtGI was found in breast, colorectal or kidney cancers, while a positive correlation was found in gastric cancer. Conversely, germ cell testicular cancers lack mtGI. Damage by reactive oxygen species (ROS), slipped-strand mispairing (SSM) and deficient repair are the causes explaining the appearance of mtGI. The replication and repair of mtDNA are controlled by nuclear genes. So far, there is no clear evidence linking MMR gene malfunction with mtGI. Polymerase gamma (POLgamma) carries out the mtDNA synthesis. Since this process is error-prone due to a deficiency in the proofreading activity of POLgamma, this enzyme has been assumed to be involved in the origin of mt-mutations. Somatic cells have hundreds to thousands of mtDNA molecules with a very high rate of spontaneous mutations. Accordingly, most somatic cells probably have a low frequency of randomly mutated mtDNA molecules. Most cancers are of monoclonal origin. Hence, to explain the appearance of mtGI in tumors we have to explain why a given variant mt-haplotype expands and replaces part of (heteroplasmy) or all (homoplasmy) wild mt-haplotypes in cancer cells. Selective and/or replicative advantage of some mutations combined with a severe bottleneck during the mitochondrial segregation accompanying mitosis are the mechanisms probably involved in the origin of mtGI.

Molecular diagnosis of head and neck cancer

Patients with advanced stages of head and neck cancer frequently develop locoregional recurrence as well as distant metastases. These data indicate that traditional diagnostic methods such as histopathology and radiology are not sensitive enough to detect the small numbers of tumor cells which are left behind, defined as minimal residual disease (MRD). Sensitive diagnostic assays based on molecular markers appear to be powerful tools to improve the staging of these patients. At the DNA level, tumor-specific p53 mutations seem to have great potential for the detection of "occult" tumor cells at surgical margins and lymph nodes. At the RNA level HNSCC associated antigens like the E48 antigen, allow the detection of rare HNSCC cells in blood and bone marrow and, it is hoped, also in lymph nodes and lymph node aspirates. However, the molecular assays which are used to detect MRD are subject to certain (technical) problems which affect their sensitivity and specificity. In this paper we will present examples of molecular assays such as the plaque assay using p53 mutations and the E48 RT-PCR, and show their use for MRD detection in cervical lymph nodes. In addition, we will discuss the problems and pitfalls associated with these sensitive techniques.

Mechanisms underlying losses of heterozygosity in human colorectal cancers

Losses of heterozygosity are the most common molecular genetic alteration observed in human cancers. However, there have been few systematic studies to understand the mechanism(s) responsible for losses of heterozygosity in such tumors. Here we report a detailed investigation of the five chromosomes lost most frequently in human colorectal cancers. A total of 10,216 determinations were made with 88 microsatellite markers, revealing 245 chromosomal loss events. The mechanisms of loss were remarkably chromosome-specific. Some chromosomes displayed complete loss such as that predicted to result from mitotic nondisjunction. However, more than half of the losses were associated with losses of only part of a chromosome rather than a whole chromosome. Surprisingly, these losses were due largely to structural alterations rather than to mitotic recombination, break-induced replication, or gene conversion, suggesting novel mechanisms for the generation of much of the aneuploidy in this common tumor type.

Urine based markers of urological malignancy

PURPOSE

A number of urine based markers have been and are being investigated for the diagnosis and prognostication of urological conditions. A majority of these markers have been evaluated in urological neoplasms, particularly bladder cancer. The diagnosis of bladder cancer currently relies on identifying malignant cells in the urine and subsequently visualizing the tumor on cystoscopy. This diagnosis is further confirmed by transurethral resection or biopsy. While urine cytology is specific, it is not sensitive, especially for detecting low grade disease. This characteristic has prompted the search for more accurate markers of bladder cancer. In this review we critically examine the results of studies evaluating various markers for bladder cancer.

MATERIALS AND METHODS

The published literature on urine based markers for all urological diseases, particularly bladder cancer, was identified using a MEDLINE search and critically analyzed. The sensitivity, specificity, positive and negative predictive values of the various markers were compared. The benefit of using combined markers rather than a single marker was also analyzed from published reports.

RESULTS

Most published literature on urine based markers for urological malignancies involve such markers for diagnosing and prognosticating bladder cancer. Hence, we focused mainly on urine based markers in bladder cancer. Most markers appear to have an advantage over urine cytology in terms of sensitivity, especially for detecting low grade, superficial tumors. However, most markers tend to be less specific than cytology, yielding more false-positive results. This scenario is more common in patients with concurrent bladder inflammation or other benign bladder conditions. However, there is reason to be optimistic about several new markers that appear to provide better specificity. Few urine based markers have been identified and investigated in other urological tumors.

CONCLUSIONS

Detecting bladder cancer using diagnostic markers still presents a challenge. A number of new markers are currently available that appear to be significantly more accurate than cytology. However, further studies involving a larger number of patients are required to determine their accuracy and widespread applicability for diagnosing bladder cancer. Urine based markers do not appear to have a significant role in the diagnosis or prognosis of other urological malignancies, such as prostate, kidney or testicular cancer.

Immunohistochemical analysis of expression and allelotype of mismatch repair genes (hMLH1 and hMSH2) in bladder cancer

Mutation of human homologues of DNA mismatch repair (MMR) genes in tumours has been shown to be associated with the phenomenon of microsatellite instability (MSI). Several studies have reported the occurrence of MSI in bladder cancer, but evidence of involvement of MMR genes in the pathogenesis of this cancer is still unclear. We therefore utilized quantitative immunohistochemical (IHC) image analysis and PCR-based allelotype analysis to determine hMLH1 and hMSH2 genes alteration in a cohort of Egyptian bladder cancer samples. IHC analysis of 24 TCC and 12 SCC revealed marked- intra and intertumour heterogeneity in the levels of expression of the two MMR proteins. One TCC lost MLH1 expression and one lost MSH2, (1/24, 4%), and one SCC lost MSH2 (1/12, 8%). A large proportion of analysed tumours revealed a percentage positivity of less than 50% for MLH1 and MSH2 expression (44% and 69%, respectively). Complete loss of heterozygosity in three dinucleotide repeats lying within, or in close proximity to, hMLH1 and hMSH2 was rare (2/57, (4%) for MLH1; and 1/55, (2%) for MSH2), however allelic imbalance was detected in 11/57 (hMLH1) and 10/55 (hMSH2) at any of the informative microsatellite loci. These alterations in structure and expression of DNA MMR genes suggest their possible involvement in the tumorigenesis and/or progression of bladder cancer.

Detecting bladder cancer in the Chinese by microsatellite analysis: ethnic and etiologic considerations

BACKGROUND

Microsatellite analysis of urine sediments has shown promise as a highly sensitive and specific technique for the detection of bladder cancer. However, most studies have been conducted in Western countries with Caucasian subjects. We explored the potential of microsatellite analysis for detecting bladder cancer in Chinese people.

METHODS

We performed microsatellite analysis of surgical specimens and urine sediment cells collected from Chinese patients with bladder tumors. Those microsatellite markers giving clearly readable patterns and showing susceptibility to alterations were used as a panel to detect primary tumors. A blinded study of additional patients with bladder cancer was performed to investigate the practical value of this panel for detecting bladder cancer. All statistical tests were two-sided.

RESULTS

Thirty-eight bladder tumors and corresponding urine sediment specimens were initially screened for 60 microsatellite markers from 18 chromosomes. Nine markers, most of which were different from those that had been used for Western patients, with frequent alterations in the initial patients were selected for further analysis. In the subsequent blinded experiment, microsatellite alterations were observed in urine sediments from 22 (96%) of 23 patients with bladder cancer and from all three patients with inverted papilloma. None of the urine sediments from the one patient with bladder lipoma, from the one patient with neurofibroma, or from the 12 individuals without evidence of bladder tumor showed any microsatellite alterations.

CONCLUSIONS

Microsatellite analysis of urine sediments could be a practical method for detecting bladder cancer in the Chinese. Our identification of different microsatellite markers highlights possible ethnic and etiologic disparities between the Chinese and Western bladder cancer patients.

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.

Genetic detection of bladder cancer by microsatellite analysis of p16, RB1 and p53 tumor suppressor genes

PURPOSE

We investigated the incidence of genetic alterations in urine specimens from patients with bladder cancer.

MATERIALS AND METHODS

A total of 28 cytological urine specimens were assessed for microsatellite alternations, and 15 microsatellite markers were located on p53, RB1 and p16 regions. In 15 patients DNA from tumor specimens was also available.

RESULTS

Loss of heterozygosity was detected in 26 of 28 patients (93%) in at least 1 microsatellite marker. Allelic losses were found in 18 patients (64%) for the p16 locus, in 8 (29%) for the RB1 locus and in 17 (61%) for the p53 region. In contrast, no microsatellite alterations were found in the normal group without evidence of bladder cancer. In 11 cases genetic alterations in the cytological urine specimens were not detectable in the corresponding tumor specimen, suggesting heterogeneity of bladder cancer.

CONCLUSIONS

The detection of loss of heterozygosity in cytological urine specimens may be a prognostic indicator of early detection of bladder cancer. Our results suggest that microsatellite analysis of urine specimens represents a novel, potentially useful, noninvasive clinical tool to detect bladder cancer.

Detection of oral and oropharyngeal cancer by microsatellite analysis in mouth washes and lesion brushings

Microsatellite allele losses are characteristic features of head and neck squamous cell carcinoma and can be used as molecular markers for malignancy. We have investigated the detection of microsatellite allele loss in mouth washes and lesions brushings from 19 patients with squamous cell carcinoma of the oral cavity and oropharynx as a means of tumour detection. In 84% of the analysed cases, allele loss previously identified in the tumour of these patients, was detected in these easily obtained specimens. No alterations were found in material derived from 10 healthy individuals. Success of detection was independent of tumour stage, suggesting that this approach may be useful for early diagnosis as well as for follow-up.

Identification of microsatellite length polymorphism by a polymerase chain reaction-based assay at IL-1beta gene locus in cancer cells

It has long been considered that genetic instability is an integral component of human neoplasia, however the frequency of microsatellite instability in human melanoma and non-melanoma skin cancer was less evidenced. We report here an alteration at the complex dinucleotide repeat (TC)n sequence in the interleukin 1-beta gene locus by polymerase chain reaction (PCR)-based assay in mouse melanoma as well as in various cancer cells, which may provide a simple, rapid, non-radioactive screening assay for cancer detection.

Application of the p53 and K-ras gene mutation patterns for cytologic diagnosis of recurrent lung carcinomas

BACKGROUND

Cytologic specimens are one of the most important materials for lung carcinoma diagnosis, because they can be used in mass screening for lung carcinoma and early detection of cancer recurrence by examination of sputum and pleural fluid.

METHODS

To prove the potentiality of the cytologic specimens to be subjected to molecular detection of recurrent lung carcinomas, the authors enrolled 16 patients who had undergone surgical treatment for lung carcinoma with recurrence detected by malignant pleural fluid. First, they examined K-ras gene and p53 tumor suppressor gene abnormalities in resected tumors by polymerase chain reaction-based single-strand conformation polymorphism (PCR-SSCP) analysis. Next, using a microdissection method, they investigated the use of cytologic specimens such as pleural fluid for the detection of recurrence by finding the same mutations observed in the initially resected tumor.

RESULTS

Seven abnormally shifted bands were detected among six patients by PCR-SSCP analysis of surgical materials. Five of 7 abnormally shifted bands (71.4%) also were detected from microdissected malignant cells in cytologic smears. In two cases, they detected mutations by using single malignant cells in pleural fluid.

CONCLUSIONS

The authors successfully detected the same mutations in recurrent cytologic specimens as those in the initially resected tumors by PCR-SSCP analysis. These findings suggest that the p53 and K-ras gene mutation patterns are effective markers for the detection of recurrent lung carcinoma in cytologic specimens. Cancer (Cancer Cytopathol)

Loss of heterozygosity assay for molecular detection of cancer using energy-transfer primers and capillary array electrophoresis

Microsatellite DNA loci are useful markers for the detection of loss of heterozygosity (LOH) and microsatellite instability (MI) associated with primary cancers. To carry out large-scale studies of LOH and MI in cancer progression, high-throughput instrumentation and assays with high accuracy and sensitivity need to be validated. DNA was extracted from 26 renal tumor and paired lymphocyte samples and amplified with two-color energy-transfer (ET) fluorescent primers specific for loci associated with cancer-induced chromosomal changes. PCR amplicons were separated on the MegaBACE-1000 96 capillary array electrophoresis (CAE) instrument and analyzed with MegaBACE Genetic Profiler v.1.0 software. Ninety-six separations were achieved in parallel in 75 minutes. Loss of heterozygosity was easily detected in tumor samples as was the gain/loss of microsatellite core repeats. Allelic ratios were determined with a precision of +/- 10% or better. Prior analysis of these samples with slab gel electrophoresis and radioisotope labeling had not detected these changes with as much sensitivity or precision. This study establishes the validity of this assay and the MegaBACE instrument for large-scale, high-throughput studies of the molecular genetic changes associated with cancer.

Molecular mechanisms and pathways in bladder cancer development and progression

BACKGROUND

The basis for bladder cancer development and progression is complex and involves genetic abnormalities. These abnormalities yield phenotypic changes that allow normal transitional cells to become cancerous and finally acquire the "malignant phenotype."

METHODS

The authors review the most common genetic alterations in bladder cancer and the molecular mechanisms and pathways involved in the conversion of normal transitional cell into malignant transitional cancer cells.

RESULTS

There are several potential genetic changes of the urothelium that eventually cause bladder cancer initiation and tumor progression. Some of these alterations are also found in other malignancies suggesting that key common pathways exist in the development of cancer.

CONCLUSIONS

As the roles of certain genes or proteins are further elucidated, a better understanding of cancer development can aid in the prevention, diagnosis, and treatment of bladder cancer.

Urinary markers of malignancy

Transitional cell carcinoma (TCC) is the second most common malignancy in the genitourinary tract. The majority of urothelial tumors are superficial when the patient first presents, but despite adequate resection of the primary lesion the recurrence rate is particularly high. In a small but significant group of patients the tumor is primary invasive or subsequently can progress and leads to death. Voided urine can be easily obtained and therefore diagnostic urine tests would be ideal for screening or follow up of TCC. Although many urinary markers have been described, none of them is used routinely in clinical practice. Promising tumor markers still need to be evaluated in multi-center clinical studies. Larger prospective trials are necessary in order to identify prognostic indicators that would help to predict disease progression or response to different treatment modalities (BCG, chemo-, radiotherapy, etc.). Hopefully, new diagnostic urine tests will allow to identify patients who will most benefit from early cystectomy with or without adjuvant treatment, bladder sparing protocols or systemic treatment. In this paper we have reviewed the literature and discuss, from the clinician's point of view, the current status of various diagnostic tests for urinary markers. [Lee SJ, Lee WE, Chang SG, Lee CH, Kim JI. A comparative study of telomerase, Lewis X, BTA, NMP22 and urinary cytology in bladder tumor. J Urol 1999;161(suppl):152.]

Genetic changes in solid tumors

Although most solid tumors are treated surgically, determining the genetic changes present in the tumor of an individual patient is becoming increasingly important for managing the oncology patient. Our knowledge of the genetic alterations that characterize and predispose to solid tumors continues to expand. Concurrently, the advent of newer technologies such as DNA chips has the potential to enable a more rapid and comprehensive assessment of these changes. The ultimate goal of this new information and technology is to provide sensitive and specific tests that reduce unnecessary procedures and optimize therapy. This review addresses the utility of molecular testing in evaluating cancer. A review of the current technology and hereditary cancer syndromes is also presented.

Clonality and genetic divergence in multifocal low-grade superficial urothelial carcinoma as determined by chromosome 9 and p53 deletion analysis

Multifocality and recurrence are clinically important features of urothelial carcinomas of the urinary bladder. Recent molecular genetic studies have suggested that multifocal urothelial carcinomas are monoclonally derived from an identical transformed progenitor cell. However, most of these studies investigated advanced and poorly differentiated tumors. The study presented focuses on early papillary tumors, including 52 superficial well-differentiated multifocal and recurrent bladder carcinomas from 10 patients. Microdissection separating urothelium from stromal cells was considered essential to obtain pure tumor cell populations. Genetic analysis was carried out by applying two different methods. Dual color fluorescence in situ hybridization (FISH) with centromeric probes for chromosomes 9 and 17 and gene-specific probes for chromosome loci 9q22, 9p21, and 17p13 was carried out in parallel to loss of heterozygosity (LOH) analyses applying 5 microsatellite markers on these chromosomes. Overall, deletions on chromosome 9p were found in 47 tumors (90%), at chromosome 9q in 36 tumors (69%) and at chromosome 17p in 3 tumors (6%). There was a very high correlation of the results between FISH and LOH analysis. Ten early superficial papillary tumors showed deletion of chromosome 9p without deletion of 9q, suggesting 9p deletions as a very early event in the development of papillary urothelial carcinoma. Although in four patients, all investigated tumors showed identical genetic alterations and one patient showed no genetic alterations at the loci investigated, in five patients, two or more clones with different deletions were found. In four of these patients, the results are compatible with clonal divergence and selection of different cell subpopulations derived from a common progenitor cell. However, in one patient different alleles in two markers at chromosome 9 were deleted, favoring an independent evolution of two recurring tumor cell clones. In summary, we could show that there is considerable genetic heterogeneity in early multifocal and recurring urothelial carcinoma and demonstrated the occurrence of two independent clones in at least one patient as an indicator of possible initial oligoclonality of bladder cancer.