Infrequent replication errors at microsatellite loci in tumors of patients with multiple primary cancers of the esophagus and various other tissues

Etiologia do Carcinoma Epidermóide de Hipofaringe

A carcinogênese é uma alteração do controle do crescimento celular devido a uma exposição prolongada a algum agente com potencial mutagênico. O tabagismo é um importante determinante do risco de câncer de faringe, e a associação com o etilismo aumenta ainda mais este risco. Fatores nutricionais, como na síndrome de Plummer-Vinson, em que há uma anemia ferropriva, parecem ter também importância. Como apenas uma fração dos indivíduos expostos a tabagismo e etilismo desenvolvem câncer, sugere-se que fatores específicos do hospedeiro estabeleçam suscetibilidade diferente. Assim, o sexo masculino é o mais acometido, bem como a sexta e sétima décadas. Encontrou-se um risco relativo maior com a exposição a certas substâncias. Portadores de um primeiro tumor, exposição a radioterapia prévia e aos vírus da papilomatose humana (HPV) e, menos freqüentemente, EBV, apresentam maior risco de desenvolvimento de um câncer faríngeo. Parece ainda haver uma predisposição familiar, bem como uma correlação com a ativação de oncogens e a inativação de gens supressores de tumores, como o p53.

Loss of heterozygosity and microsatellite instability as predictive markers among Iranian esophageal cancer patients

OBJECTIVES

Variation in microsatellite sequences that are dispersed in the genome has been linked to a deficiency in cellular mismatch repair system and defects in several genes of this system are involved in carcinogenesis. Our aim in this study was to illustrate microsatellite DNA alteration in esophageal cancer.

MATERIALS AND METHODS

DNA was extracted from formalin fixed paraffin embedded (FFPE) tissues from surgical and matched margin-normal samples. Microsatellite instability (MSI) and loss of heterozygosity (LOH) were studied in 50 cases of esophageal squamous cell carcinoma (ESCC) by amplifying six microsatellite markers: D13S260 (13q12.3), D13S267 (13q12.3), D9S171 (9p21), D2S123 (2p), D5S2501 (5q21) and TP53 (17p13.1) analyzed on 6% denaturing polyacrylamide gel electrophoresis.

RESULTS

Statistical analysis indicated a near significant reverse correlation between grade and LOH (P= 0.068, correlation coefficient= -0.272). Specifically, increased LOH in tumor DNA has a significant correlation with increased differentiation from poorly differentiated to well differentiated tumors (P= 0.002 and P= 0.016 respectively). In addition, higher number of chromosomal loci with LOH showed a reverse correlation with lymph node metastasis (P= 0.026, correlation coefficient= -0.485). Furthermore, there was a positive correlation between addiction and MSI (P= 0.026, correlation coefficient= 0.465).

CONCLUSION

Microsatellite DNA alterations may be a prognostic tool for detection and the evolution of prognosis in patients with SCC of esophagus. It can be concluded that regional lymph node metastasis would be less likely with increased heterozygote loci and addiction with any of opium, cigarette, water pipe or alcohol can be a susceptibility factor(s) for MSI.

Microsatellite instability in gastrointestinal tract cancers: a brief update

Microsatellite instability (MSI) was initially reported in colorectal cancer and, particularly, in hereditary nonpolyposis colorectal cancer (HNPCC). Since mutations in the genes functioning in DNA mismatch repair (MMR) were found in HNPCC kindred, this phenotype has been connected to a deficiency in MMR. The MSI(+) phenotype is associated with various human malignancies. As MSI(+) tumors appear to form a unique clinicopathological and molecular entity that is clearly distinct from that of classical colorectal tumors, which are accompanied by chromosomal instability (CIN), an exclusive pathway of tumorigenesis has been proposed in colorectal cancer. However, this scheme, comprising two mutually exclusive pathways, is now being reexamined, in light of a series of evidence accumulating in the literature, which relates to (a) distinction between high-level MSI (MSI-H) and low-level MSI (MSI-L), (b) heterogeneity in MSI-H, particularly in the sporadic and hereditary settings, (c) molecular mechanisms underlying the MSI(+) phenotypes, and (d) relationships between the MSI(+) and CIN phenotypes. Several molecular mechanisms may underlie repeat instability in eukaryotic cells. The relationship between MSI and defective MMR may be more complicated than has been suspected. The role of MMR deficiency in tumorigenesis in the digestive tract appears to be diverse and is not simple, even in the colorectum.

Frequent microsatellite instability in primary esophageal carcinoma associated with extraesophageal primary carcinoma

Patients with esophageal squamous cell carcinoma (ESCC) frequently develop other primary cancers, such as gastric cancer and head and neck cancer. Details of carcinogenesis in patients with multiple primaries that include esophageal carcinoma with other primary carcinoma (ECOPC) remain uncertain. We examined microsatellite instability (MSI) status, frameshift mutation in target genes of MSI, mismatch repair protein expression and hypermethylation of the hMLH1 promoter region in ECOPC patients to better understand the underlying carcinogenic processes. High frequency MSI (MSI-H) was found in 15 (44.1%) of 34 patients with ECOPC, but in only 6 (14.3%) of 42 patients with esophageal cancer alone (p < 0.01). Frameshift mutations in TGFbetaRII, BAX, MSH3 and MSH6 genes respectively were present in 4, 1, 2 and 2 of 34 ECOPC patients. Immunohistochemical study showed that 12 (80.0%) of 15 MSI-H tumors showed loss of expression of either hMLH1 or hMSH2. In addition, 6 of 9 tumors (66.7%) that showed reduced hMLH1 expression also had hypermethylation of the hMLH1 promoter region. Our findings suggested that carcinogenesis in ECOPC was closely associated with the MSI pathway because of mismatch repair protein deficiency.

Frequent Loss of Heterozygosity but Rare Microsatellite Instability in Oesophageal Cancer in Japanese and Chinese Patients

Reported frequencies for microsatellite instability (MSI) in oesophageal cancer differ widely in the literature, perhaps due to the high incidence of loss of heterozygosity (LOH) in this cancer. Using high-resolution fluorescent microsatellite analysis (HRFMA), we analysed microsatellite alterations in detail in 50 Japanese and 50 Chinese patients with squamous cell carcinoma in the oesophagus. In HRFMA, several devices have been developed to improve the detection characteristics, reproducibility of polymerase chain reaction and the migration accuracy of electrophoresis. All the alterations observed were separable into MSI, LOH and alterations ambiguous for both. MSI was rare in these panels of oesophageal carcinomas. The frequencies of MSI in the Japanese and Chinese subjects were 8 and 4%, respectively. All the alterations were mild (within 2 base pairs) and were observed in a limited number of markers. More drastic types of MSI, such as those typical in colorectal cancer, were not observed. On the other hand, the incidence of LOH was high, reaching 50% for the Japanese and 70% for the Chinese subjects. In many of these cases, LOH was observed in multiple microsatellite markers. The frequency of LOH in each marker was not apparently biased. Although in many cases MSI and LOH were clearly distinguished with use of the sensitive and quantitative fluorescent assay, theoretically indistinguishable patterns were noted in some cases. In conclusion, MSI is rare and LOH predominates in squamous cell carcinoma in the oesophagus.

Allelic loss of 14q32 in the pathogenesis of gastrointestinal and ampullary malignancies: mapping of the target region to a 17�cM interval

PURPOSE

The genetic basis for gastrointestinal and ampullary carcinomas remains uncertain. This study was performed to pinpoint novel chromosomal region involved in the tumorigenesis of gastrointestinal tract.

METHODS

We screened the allelic status on 16 chromosomal arms in a patient with synchronous ampullary carcinoma and gastric cancer, but who had no family history of familial cancer syndrome. The significance of the shared 14q deletion was examined on clinical cohorts of sporadic gastric (n=12) and ampullary (n=10) carcinoma, respectively. Then, high-density allelotype mapping was performed on 14q32 by using 23 microsatellite markers for the synchronous tumors.

RESULTS

The synchronous gastric and ampullary carcinomas had no frameshift mutations in the APC, MSH2, MSH3, and MSH6 genes. Among the microsatellite markers screened, only D14S267 showed identical loss in the synchronous tumors. The same allelic loss was also detected in one of ampullary carcinomas (10%) and two of gastric cancers (16.7%). Fine mapping of 14q determined a minimally deleted region between D14S65 and D14S1010 (17 centiMorgans) for the synchronous tumors.

CONCLUSIONS

This study illustrates a paradigm using molecular genetic approach in identifying chromosome 14q32 that may harbor a tumor suppressor gene involved in the pathogenesis of a subset of gastrointestinal and ampullary malignancies.

The clinical importance and prognostic implications of microsatellite instability in sporadic cancer

AIMS

The genetic abnormality known as microsatellite instability (MSI), first identified in colorectal cancer in 1993, has subsequently been recognised in other malignancies. These cancers are caused by a defect in the nuclear mismatch repair system, allowing mutations to accumulate with every cellular division. Hereditary Non Polyposis Colon Cancers (HNPCC) and associated malignancies demonstrating MSI have a unique histological appearance, improved prognosis and altered response to chemotherapy and radiotherapy. This review examines the incidence of MSI and its clinical significance in commonly occurring solid malignancies.

METHOD

A medline based literature search was performed using the key words 'Microsatellite Instability' and the name of the specific malignancy being investigated. Additional original papers were obtained from citations in those articles identified in the original medline search.

RESULTS

MSI has been detected in many solid malignancies although the definition of instability applied has been variable. It is most commonly found in sporadic malignancies that also occur in the HNPCC syndrome such as colorectal, stomach, endometrial and ovarian cancer. MSI may impart a favorable prognosis in colorectal, gastric, pancreatic and probably oesophageal cancers but a poor prognosis in non small cell lung cancer. In clinical studies colorectal cancers demonstrating MSI respond better to chemotherapy while in vitro studies using MSI positive cell lines show resistance to radiotherapy and chemotherapy.

CONCLUSION

MSI may be a useful genetic marker in prognosis and could be an influential factor in deciding treatment options. However, in many cancers its significance remains unclear and more evaluation is required.

Association of aldehyde dehydrogenase 2 gene polymorphism with multiple oesophageal dysplasia in head and neck cancer patients

BACKGROUND

Multiple occurrences of oesophageal dysplasia are frequently observed in head and neck cancer patients, and closely associated with alcohol consumption. Acetaldehyde, the first metabolite of ethanol, is thought to play an important role in the carcinogenesis of the upper aerodigestive tract.

AIM

To investigate if genetic polymorphism in alcohol metabolising enzymes (ADH3, alcohol dehydrogenase 3; ALDH2, aldehyde dehydrogenase 2) is associated with oesophageal multiple dysplasia in head and neck cancer patients.

METHODS

Thirty one consecutive patients with head and neck cancer were included in the study. Multiple oesophageal dysplasia was detected endoscopically as multiple Lugol voiding lesions (multiple LVL) using the Lugol dye staining method. The ADH3 and ALDH2 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Among the 31 patients with head and neck cancer, 17 had multiple LVL. Multiple LVL were closely associated with a second primary oesophageal carcinoma in head and neck cancer patients (odds ratio 60.7, 95% CI 5.6-659). Furthermore, the mutant ALDH2 allele was significantly more prevalent in patients with multiple LVL (65% v 29%; p<0.05) whereas no difference was observed in ADH3 polymorphism.

CONCLUSIONS

The mutant ALDH2 allele appears to be a risk indicator for multiple LVL in head and neck cancer patients. Accumulation of acetaldehyde due to low ALDH2 activity may play a critical role in cancerous changes throughout the mucosa in the upper aerodigestive tract.

Mutational analysis of the hMLH1 gene using an automated two-dimensional DNA typing system

Searching for mutations in DNA mismatch repair genes is important not only for presymptomatic diagnosis, but also for documenting the spectrum of mutations among families carrying predispositions to hereditary nonpolyposis colorectal cancer (HNPCC). We utilized an automated two-dimensional DNA typing system for mutational analysis of the hMLH1 gene and established optimal conditions for application of the technique to analysis of hMLH1. This approach enabled us to visualize 21 spots covering all 19 coding exons on a single gel and to envisage whether and where any mutations existed. All mutations that we had detected previously by other means in a panel of HNPCC patients and in one patient with sporadic endometrial cancer were also detectable by this method. Furthermore, using the 2-D system, we screened the entire coding regions of the hMLH1 gene in DNAs isolated from affected individuals belonging to two large HNPCC kindreds and four HNPCC-like kindreds, and from four patients with multiple primary cancers as well as eight sporadic colorectal cancers with replication error (RER)-positive phenotypes. We detected novel germline mutations in one HNPCC proband and one sporadic colorectal cancer with the RER-positive phenotype and one polymorphism in two HNPCC-like kindreds. This new diagnostic method is applicable to mutational analysis of any disease-causing gene, and it offers a major improvement over current approaches.

Microsatellite instability in double cancers of the esophagus and head and neck

It is generally accepted that patients with squamous cancers of the esophagus are known to have a high risk of concomitant head and neck cancer. However, there have been only a few reports describing microsatellite instability (MSI) in patients with both esophageal squamous cell carcinoma and head and neck cancers. To evaluate the role of genetic instability in carcinogenesis in such patients, we analyzed six microsatellite loci in 21 tumors from 10 patients who had developed primary cancers of both the esophagus and the head and neck. MSI was detected in 6 out of 10 patients. In five patients with double cancer, MSI was observed at the same microsatellite loci in both the esophageal and the head and neck tumors obtained from the same individuals. These data suggest that such patients may have the same underlying defect in the mismatch repair system, providing insight into possible mechanisms for field carcinogenesis.

Infrequent frameshift mutations of polynucleotide repeats in multiple primary cancers affecting the esophagus and other organs

Frequent frameshift mutations of simple nucleotide repeats in the protein-encoding regions, as well as replication errors (RERs) at microsatellite loci, have recently been demonstrated in gastrointestinal tumors. These genetic instabilities have been considered indicative of an increased risk of accumulating mutations in cancer-associated genes and of developing multiple cancers. We studied frameshift (or insertion/deletion) mutations of simple nucleotide repeats in five genes (TGFbeta type II receptor [TGFbetaRII], E2F4, MSH2, MSH3, and MSH6) in 23 tumors from 12 patients who had synchronous cancers of the esophagus and other organs. Genetic instability at four microsatellite loci, as well as mutations in the TP53, APC, and KRAS2 genes, were also studied. No frameshift mutations were observed in the TGFbetaRII, MSH3, and MSH6 genes. RER and a deletion mutation of BAT26 in MSH2 were present in one (1/23; 4%) gastric cancer. This tumor also carried a deletion mutation in the serine (AGC) repeat of the E2F4 gene. Mutation screening of the TP53, APC, and KRAS2 genes revealed that the synchronous cancers did not carry the same mutations. Our results suggested that genetic instability, such as insertion/deletion mutations in simple nucleotide repeats, is not significantly associated with the development of multiple primary cancers of the esophagus and other organs, and that these synchronous cancers developed independently according to their different environmental factors.

Microsatellite instability in squamous cell carcinomas of the head and neck related to field cancerization phenomena

Patients affected by squamous cell carcinoma of the head and neck (HNSCC) show frequent occurrence of multiple cancers and widespread precancerous lesions in the mucosa of the upper respiratory tract, a phenomenon known as field cancerization. In this study, we investigated the role of genetic instability in the development of HNSCC and in particular in tumour multiplicity phenomena of the upper respiratory tract. For this purpose, we analysed microsatellite instability (MI) and loss of heterozygosity (LOH) at 20 loci mapping on five chromosomal arms in 67 HNSCC patients, 45 of whom had a single cancer and 22 had multiple primary tumours. The possible involvement of the hMLH1 gene in genetic instability and as a potential target of 3p21 deletion phenomena in head and neck cancers was also investigated. Our data indicate that mismatch repair-related genetic instability plays a minor role in the carcinogenesis of HNSCC and in tumour multiplicity of the head and neck region. Moreover, our results exclude a role for the hMLH1 gene as a determinant of MI and as a specific gene target of deletion at 3p21 in HNSCC. We conclude that presumably other genetic mechanisms, such as those hypothesized for MI-negative hereditary non-polyposis colorectal cancer patients, may play a major role in the carcinogenesis of the mucosa of the upper respiratory tract.

Analysis of the p53 gene mutations in patients with multiple primary cancers of the oesophagus

We investigated genetic alterations of the p53 gene in two patients with multiple primary oesophageal squamous cell carcinomas (ESCs). We found that each primary tumour could be distinguished by mutation of p53. Moreover, mutations detected in the p53 gene in metastatic lymph nodes were the same as those detected in at least one of the primary tumours. Our results presented the possibility of: (1) discrimination of primary and metastatic legions in patients with multiple primary ESCs; (2) determination of metastatic pathway to regional lymph nodes; and (3) application for the development of a better clinical management of patients with multiple primary ESCs.

Genetic alterations in patients with esophageal cancer with short- and long-term survival rates after curative esophagectomy

OBJECTIVE

The objective of this study was to ascertain the exact relation between specific oncogenes and long- and short-term survival rates in patients with esophageal cancer.

SUMMARY BACKGROUND DATA

Recent developments in molecular biology have shown that several oncogenes and suppressor genes are involved in the development of esophageal cancer. However, the role of these genes still is unknown.

METHODS

The clinical outcome of 84 cases of R0-resected esophageal carcinomas (from 1986-1993) and the molecular and biologic characteristics of these tumors were studied. The patients studied were divided into three groups, which were designated as follows: shortest term survivors (up to 6 months), short-term survivors (7-12 months), and long-term survivors (>5 years). These groups included 23, 17, and 44 subjects, respectively. For the genomic analysis, CyclinD1, int-2, murine double minute 2 (MDM2), retinoblastoma, p53, adenomatous polyposis coli (APC), deleted in colorectal carcinoma (DCC), and human papillomavirus were studied in these patients. The regrowth capability of primary cultures and the clinicopathologic characteristics of these patients also were analyzed.

RESULTS

The CyclinD1 and int-2 genes, which are located in the 11q13 chromosome, and the MDM2 gene were related to short survival. However, the p53 mutation and human papillomavirus infection were not related to short-term survival. The average ratio of genomic abnormalities to genes examined was higher in the shortest and short-term survival groups than in the long-term survival group. Regrowth capability in primary cultures also was related to short-term survival. Among the long-term survival patients, 7 (16%) of 44 cases suffered further cancer after esophagectomy.

CONCLUSIONS

These results suggest that the 11q13 amplicon and MDM2 may play an important role in the progression of esophageal cancer, and an accumulation of genomic abnormalities may result in poor prognosis. Careful follow-up testing for double cancer is needed in long-term survivors of esophageal cancer.

Loss of heterozygosity and microsatellite alterations in p53 and RB genes in adenoid cystic carcinoma of the salivary glands

Adenoid cystic carcinomas (ACC) constitute approximately 20% of malignant salivary gland tumors. Several histological types of ACC are recognized and may coexist in a single tumor. The authors divided ACC into lower grade (tubular and cribriform subtypes) and higher grade (trabecular and solid) subtypes. A preliminary analysis of 10 ACCs showed a relatively high incidence of loss of heterozygosity (LOH) at the p53 and RB genes and low or absent K-ras mutations and LOH at chromosomal loci 3p, 5q, 8p, and 9p. From 21 tumors, the authors carefully microdissected and analyzed 36 subtype foci. Three interrelated pieces of evidence indicate that the relatively poor prognosis higher grade subtype arises from one or more of the lower grade subtypes via progression events associated with mutations in the p53 or RB genes. First, the number of mutations (both LOH and microsatellite alterations) at either gene is greater in higher grade foci than in lower grade foci; second, multiple mutations (two and occasionally three) are present in only higher grade foci; and third, when lower and higher grade foci are present in the same tumors, identical mutations plus other mutations are present in the corresponding higher grade foci. These findings suggest that molecular analyses of ACCs may provide information of prognostic importance.

Clonal heterogeneity in human esophageal squamous cell carcinomas on DNA analysis

Cancers are thought to arise through multistep accumulation of somatic mutations in the progeny of a single cell. Multiple mutations may induce molecular intratumor heterogeneity. Therefore, we examined molecular clonal heterogeneity in esophageal squamous cell carcinomas. Twenty-four esophageal squamous cell carcinomas and associated lymph node metastases were examined for microsatellite alterations, and abnormalities of the p53 and transforming growth factor-beta type II receptor (TGF-beta RII) genes. There were eight cases (33%) showing different patterns of loss of heterozygosity in primary tumors and metastatic lymph nodes with microsatellite markers. On the other hand, the abnormalities of p53 were identical in all these cases. No mutation was detected in the simple repeated sequences of the TGF-beta RII gene. These results indicate that molecular clonal heterogeneity exists in esophageal squamous cell carcinomas. Therefore, care is necessary in preoperative genetic diagnosis using biopsy samples.

Genetic alterations in esophageal cancer and their relevance to etiology and pathogenesis: a review

Cancer of the esophagus exists in 2 main forms with different etiological and pathological characteristics-squamous cell carcinoma (SCC) and adenocarcinoma (ADC). This review focuses on the occurrence of genetic alterations in SSC and ADC of the esophagus and on their possible implications for the elucidation of the etiology and pathogenesis of these cancers. The most common alterations found in esophageal cancers include allelic losses at chromosomes 3p, 5q, 9p, 9q, 13q, 17p, 17q and 18q, as well as mutations of p53 (mostly missense), Rb (deletions), cyclin DI (amplifications) and c-myc (amplifications). The sequence of occurrence of these alterations with respect to histopathological tumor progression is discussed. Our findings underscore the different etiology and pathogenesis of SCC vs. ADC and suggest that the genetic alterations observed may represent molecular fingerprints of critical risk involved in the development of these 2 cancers.