Infrequent loss of heterozygosity of APC/MCC and DCC genes in gastric cancer showing DNA microsatellite instability

H. pylori infection is related to mitochondrial microsatellite instability in gastric carcinogenesis

BACHGROUND

To assess the correlation of H. pylori infection with mitochondrial microsatellite instability (mtMSI) and IL-8 in gastric carcinogenesis.

METHODS

H. pylori infection was evaluated through histology and a urease breath test; mtMSI was measured using PCR-single strand conformation polymorphism (PCR-SSCP); IL-8 was analyzed with ELISA methods.

RESULTS

The detection rate of mtMSI was significantly higher in specimens with H. pylori infection than in those without H. pylori infection (P < 0.05). The levels of IL-8 were significantly higher in specimens with mtMSI than in those without mtMSI (P < 0.01).An association of mtMSI with the intestinal histological type was found (P < 0.05). Increased IL-8 levels induced by H. pylori were related to the invasion, lymphnode spreading and clinical stage of gastric cancer (P < 0.05).

CONCLUSIONS

H. pylori infection is related to mitochondrial microsatellite instability in the early steps of gastric cancer development. IL-8 may play a role in the development of mtMSI induced by H. pylori. Our results support a role for mtMSI in different mechanisms of gastric carcinogenesis.

hsa-miR-29c and hsa-miR-135b differential expression as potential biomarker of gastric carcinogenesis

AIM

To investigate the expression profiles of hsa-miR-29c and hsa-miR-135b in gastric mucosal samples and their values as gastric carcinogenesis biomarkers.

METHODS

The expression levels of hsa-miR-29c and hsa-miR-135b in normal gastric mucosa, non-atrophic chronic gastritis, intestinal metaplasia and intestinal-type gastric adenocarcinoma were analysed using quantitative real-time PCR. The difference between hsa-miR-29c and hsa-miR-135b expression profiles in the grouped samples was evaluated by ANOVA and Student's t-test tests. The results were adjusted for multiple testing by using Bonferroni's correction. P values ≤ 0.05 were considered statistically significant. To evaluate hsa-miR-29c and hsa-miR-135b expressions as potential biomarkers of gastric carcinogenesis, we performed a receiver operating characteristic curve analysis and the derived area under the curve, and a Categorical Principal Components Analysis. In silico identification of the genetic targets of hsa-miR-29c and hsa-miR-135b was performed using different prediction tools, in order to identify possible genes involved in gastric carcinogenesis.

RESULTS

The expression levels of hsa-miR-29c were higher in normal gastric mucosal samples, and decreased progressively in non-atrophic chronic gastritis samples, intestinal metaplasia samples and intestinal-type gastric adenocarcinoma samples. The expression of hsa-miR-29c in the gastric lesions showed that non-atrophic gastritis have an intermediate profile to gastric normal mucosa and intestinal-type gastric adenocarcinoma, and that intestinal metaplasia samples presented an expression pattern similar to that in intestinal-type gastric adenocarcinoma. This microRNA (miRNA) has a good discriminatory accuracy between normal gastric samples and (1) intestinal-type gastric adenocarcinoma; and (2) intestinal metaplasia, and regulates the DMNT3A oncogene. hsa-miR-135b is up-regulated in non-atrophic chronic gastritis and intestinal metaplasia samples and down-regulated in normal gastric mucosa and intestinal-type gastric adenocarcinoma samples. Non-atrophic chronic gastritis and intestinal metaplasia are significantly different from normal gastric mucosa samples. hsa-miR-135b expression presented a greater discriminatory accuracy between normal samples and gastric lesions. This miRNA was associated with Helicobacter pylori presence in non-atrophic chronic gastritis samples and regulates the APC and KLF4 tumour suppressor genes.

CONCLUSION

Our results provide evidence of epigenetic alterations in non-atrophic chronic gastritis and intestinal metaplasia and suggest that hsa-miR-29c and hsa-miR-135b are promising biomarkers of gastric carcinogenesis.

Genetic pathways, prevention, and treatment of sporadic colorectal cancer

Epithelial cancer of the colon and rectum, also known as colorectal cancer (CRC), results from a progressive accumulation of genetic and epigenetic alterations that lead to uncontrolled growth of colonocytes, the cells lining the colon and rectum. CRC is the second leading cause of cancer-related deaths and the third most common cancer in men and in women in the U.S. Of all the patients diagnosed with CRC every year, it is estimated that the vast majority of CRCs are non-hereditary “sporadic cancers” with no apparent evidence of an inherited component. Sporadic CRC results from the cumulative effects of multiple genetic and epigenetic alterations caused by somatic mutations, which may themselves be the indirect result of several environmental factors. This review examines our current understanding of the major genetic alterations leading to colon cancer, options for prevention and early detection of CRC, and the currently available treatment approaches that may target these different genetic alterations.

Premalignant lesions in gastric cancer

Despite a plateau in incidence, gastric cancer is one of the most common cancers worldwide and causes considerable morbidity and mortality. Premalignant gastric lesions are well known risk factors for the development of intestinal-type gastric adenocarcinomas. In this multistep model of gastric carcinogenesis, Helicobacter pylori causes chronic active inflammation of the gastric mucosa, which slowly progresses through the premalignant stages of atrophic gastritis, intestinal metaplasia, and adenoma/dysplasia to gastric carcinoma. This progression is paralleled by a stepwise accumulation of multiple genetic and epigenetic abnormalities. Detection, treatment, and molecular analyses of premalignant lesions may thus provide a basis for gastric cancer prevention. This review describes an overview of current knowledge on premalignant gastric lesions. It also reviews the issue of surveillance of patients with premalignant lesions in order to improve the survival of patients with gastric cancer.

Microsatellite instability and loss of heterozygosity of tumor suppressor genes in Bosnian patients with sporadic colorectal cancer

Considering its frequency, high mortality rate as well as many etiological mysteries colorectal cancer is a challenge to contemporary science. In our study we analyzed RER + and RER--phenotypes and their relations with clinical-pathological characteristics of sporadic colorectal cancers. We also analyzed genetic alterations of tumor suppressor genes as well as their relation with microsatellite instability. The study was based on 54 tumor samples and 54 samples of the surrounding healthy tissue of patients with colorectal cancer. According to Amsterdam Criteria and Bethesda Criteria 35/54 or 64,81% belonged in the group of sporadic colorectal cancer. Mononucleotide marker Bat 25 showed instability in 48,57%; Bat 26 in 45,71% and Bat 40 in 29/35 82,86% of tumor samples. Considering dinucleotide markers, TP 53 showed instability in 54,29% and DS123 in 37,14% of tumor samples. Genetic alterations in tumor suppressor genes were found in tumor tissue: NM 23 in 54,29% samples, p53 in 51,43%, APC in 51,43%, DCC2 in 34,29%, RB1 in 22, 86% and DCC 1 in 28,57%. Our studies confirmed that genetic instability had an important role in the development of tumor type. Our results showed that mononucleotide marker Bat 40 might be used for an easy and fast screening procedure in Bosnian population, because it exhibited high percent of microsatellite instability and was in relation with RER+ phenotype. This investigation showed that different genetic alterations may occur during cancer development in each individual patient's tumor. These changes result in MMR inactivation, which causes RER+ phenotype. Our results suggest a connection between alteration in some tumor suppressor genes and MSI phenotype of sporadic colorectal cancer in Bosnian population.

Tumor suppresser gene p53 expression in premalignant lesions and gastric carcinoma - prognostic value

The aim of the study was to verify the presence of mutated tumor suppresser gene p53 in intestinal mucosa with histologically confirmed premalignant lesions and gastric carcinoma, and assess its prognostic value. The paper presents prospective study that included 50 patients with gastric adeno-carcinoma of intestinal type that were treated at Gastroenterohepatology Clinic, and 50 patients with histologically confirmed chronic atrophic H. pylori positive gastritis. In the mucosa biopsy samples, we analyzed presence, frequency and severity of inflammatory-regenerative, metaplastic and dysplastic changes. We typed intestinal metaplasia immunohistochemically and confirmed the presence of p53 onco-protein in antigen positive gastric carcinoma cells, and evaluated its prognostic value. Our results suggest that H. pylori acts as an initiator of inflammatory processes in gastric mucosa, which are followed by emergence of precancerous lesions. p53 is expressed late in carcinogenesis (14%) and as such, may be considered as an indicator of transformation of premalignant into malignant lesion.

Pathology and molecular biology of gastric cancer

Several attempts to classify gastric cancer (GCA) have been made over the past decades. Most successful, and widely used, is the classification by Laurén, which distinguishes, by microscopical morphology alone, two main cancer pathogeneses, diffuse (DGCA) and intestinal (IGCA) subtypes, which appear clearly as dissimilar clinical and epidemiological entities. Here we review the main differences in epidemiology, histopathology, and molecular pathology of the two main subtypes of gastric carcinomas based on Laurén classification. In clinical practice, however, clinical staging, particularly in predicting the survival, still remains superior to all classifications of gastric cancer independent of cancer type. The existence of local precursor lesions or conditions of IGCA tumours, i.e. Helicobacter pylori gastritis, atrophic gastritis (AG), intestinal metaplasia (IM), adenoma, dysplasia, and intramucosal neoplasia, is firmly established. The links of DGCA with intestinal-type epithelium, AG or IM are poor, or do not exist. So far, H. pylori gastritis is the only universal precursor condition for DGCA. It implies that AG and achlorhydria are of minor significance and infrequent in the development of DGCA but are important steps in that of IGCA. Despite an increasing body of data, the overall view on molecular pathology of GCA remains fragmentary. No consistent differences in the molecular pathology of GCA subtypes to meet the Laurén classification have been established. With the exception of TP53, no gene mutation occurring regularly in both histological types of GCA has been reported. Chromosomal aberrations and loss of heterozygosity seem to be non-specific and do not follow any consistent route in the progression of GCA. Microsatellite instability is more commonly found in IGCA than in DGCA. The present epigenetic data suggest that most of the decrease (or loss) of gene expression may be explained by promoter hypermethylation which is more often found in IGCA. In DGCA specific genes such as CDH1 are more often hypermethylated. Compared with GCA, in premalignant condition lesions gene mutations and chromosomal aberrations are infrequent. Epigenetic dysregulation might also represent a major mechanism for altered gene expression in premalignant stages in gastric carcinogenesis.

Microsatellite instability in gastric cancer and pre-cancerous lesions

AIM: To investigate the microsatellite instability (MSI) in cancer and pre-cancerous lesions of the stomach and its mechanisms underlying the development of gastric cancer.

METHODS: Thirty-six gastric cancer samples were obtained from patients undergoing surgery. Forty-one gastric mucosa samples with dysplasia and 51 with intestinal metaplasia (IM) were obtained from patients with chronic gastritis undergoing gastro-endoscopy. Genomic DNA was extracted from the samples. Silver staining single strand conformation polymorphis-polymerize chain reaction (SSCP-PCR) was used to screen MSI markers at 5 loci (Bat-25, Bat-26, D5S346, D17S250, and D2S123) in fresh tissues and formalin-fixed, paraffin-embedded samples and their corresponding normal gastric mucosa.

RESULTS: The abnormal shifting of the single-strand DNA (MSI) was identified in 21 out of 36 (58.3%) gastric cancers. Seven cases showed high-level MSI (two or more loci altered) and 14 showed low-level MSI (one locus altered). Gastric cancer with MSI had a tendency to be located in the distal stomach. MSI was also detected in 11 out of 41 (26.8%) dysplasia samples and in 9 of 51 (17.6%) IM samples respectively. Three cases of dysplasia and one case of IM showed high-level MSI. Eight cases of dysplasia and 8 cases of IM displayed low-level MSI. MIS in IM was found only in moderate or severe-grade IM. No association was detected between MSI and dysplasia grade.

CONCLUSION: Accumulation of MSI in dysplasia and intestinal metaplasia of gastric mucosa may be an early molecular event during gastric carcinogenesis and may contribute to the acquisition of transformed cell phenotype and the development of gastric cancer.

Molecular markers in Helicobacter pylori-associated gastric carcinogenesis

Helicobacter pylori infection is a known risk factor of gastric carcino-genesis. This article presents early molecular alterations associated with H. pylori chronic gastritis and advances in the molecular characterization of preneoplastic intestinal metaplasia (IM) and premalignant gastric mucosal lesions. H. pylori infection induces changes in gene expression, genomic instability and accumulation of gene mutations in the stomach epithelium. Mutations, including LOH and microsatellite instability, and gene hypermethylation are seen not only in gastric cancer, but are already detectable in IM and gastric dysplasia/adenoma. Recent reports using microarray expression analysis identified several gastric epithelial genes that are regulated by H. pylori. Among the many genes showing altered epithelial expression in response to H. pylori, some might be useful as markers to assess gastric cancer risk. Profiles of mutagenesis and gene expression in IM and dysplasia/adenoma have been characterized and represent potential markers of preneoplastic and premalignant lesions during gastric carcinogenesis.

Clinicopathologic Behavior of Gastric Adenocarcinoma in Hispanic Patients: Analysis of a Single Institution's Experience Over 15 Years

Purpose

To determine the clinicopathologic behavior of gastric adenocarcinoma in Hispanics by comparing Hispanic and non-Hispanic patients treated at a single cancer center.

Patients and Methods

Medical records of patients with invasive gastric cancer treated from 1985 to 1999 were reviewed. Diagnoses were pathologically confirmed. Differences in categorical variables were assessed using the χ2 test. Logistic regression was used for multivariate analyses. Median survival was estimated using the Kaplan-Meier method. Cox proportional hazards modeling was used to assess the impact of covariates.

Results

Of 1,897 patients, 301 (15.9%) were Hispanic. Hispanics were significantly younger at diagnosis than non-Hispanic whites (53.1 ± 14.4 years v 59.4 ± 12.7 years, respectively; P < .005) or African Americans (57.6 ± 15.3 years, P < .005). Hispanics were less likely to have proximal gastric cancers compared with whites (38.9% v 59.5%, respectively; P < .005). Hispanics were more likely to have mucinous/signet-ring type histology (42.5%) than whites (27.4%) and African Americans (32.5%; P < .005). Hispanics were more likely to require total gastrectomy (51%) compared with whites (38%), African Americans (38%), and Asians (36%; P = .039). Among patients with metastases at diagnosis, Hispanics were less likely to have liver metastasis than whites (30% v 44%, respectively; P = .009) but more likely to have peritoneal metastasis than whites and African Americans (54% v 41% and 47%, respectively; P = .002). In Cox analyses, Asian race, earlier stage, papillary/tubular histology, distal location, and younger age were favorable predictors of survival.

Conclusion

Hispanic ethnicity does not impact survival in gastric adenocarcinoma. However, histology, metastasis pattern, tumor localization, and other clinical parameters differ sufficiently to warrant further investigation into the epidemiology, pathogenesis, and molecular biology of gastric cancer in this population.

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Mitochondrial microsatellite instability in gastric cancer and its precancerous lesions

AIM: To evaluate the role of mitochondrial microsatellite instability (mtMSI) in gastric carcinogenesis.

METHODS: MtMSI was measured with PCR-single strand conformation polymophism (PCR-SSCP) in 68 cases of advanced gastric cancer, 40 cases of chronic gastritis, 30 cases of intestinal metaplasia and 20 cases of dysplasia.

RESULTS: MtMSI was observed in 12.5% (5 of 40) of chronic gastritis, 20.0% (6 of 30) of intestinal metaplasia, 25.0% (5 of 20) of dysplasia and 38.2% (26 of 68) of gastric cancer. These findings showed a sequential accumulation of mtMSI in the histological progression from chonic gastritis to gastric cancer. An association of mtMSI with intestinal histological type and distal location was found (P = 0.001 and P = 0.002), whereas no significant correlation was found between mtMSI and age at diagnosis, sex, tumor size, depth of invasion, lymph node spread and clinical stages (P > 0.05).

CONCLUSION: MtMSI may play an early and important role in the gastric carcinogenesis pathway, especially in the intestinal type and distal gastric cancer.

Expression of pituitary tumor transforming gene in human gastric carcinoma

AIM: Pituitary tumor transforming gene (PTTG1) is overexpressed in a variety of tumors, including carcinomas of the lung, breast, colon, as well as in leukemia, lymphoma and pituitary adenomas. However, there is little information on its expression in gastric carcinoma. We sought to investigate the expression of PTTG1 in gastric carcinoma and to explore the relationship between its expression and clinicopathological factors.

METHODS: We studied 75 primary human gastric adenocarcinomas, including 17 mucosal carcinomas, 21 submucosal infiltrative carcinomas, 12 carcinomas invading proprial muscle layers, 6 carcinomas reaching the subserosa, and 19 carcinomas penetrating the serosal surface. Immunohistochemical analysis was performed using paraffin-embedded sections of gastric adenocarcinomas.

RESULTS: PTTG1 was expressed heterogeneously in carcinomas. Positive PTTG1 staining was observed in 65.3% of the carcinomas (49 of 75). Its expression did not correlate significantly with either the histological type or the depth of infiltration of the gastric carcinomas. However, a statistical analysis showed significant differences between the primary adenocarcinomas and the associated metastatic lymph nodes.

CONCLUSION: The results of this study demonstrate that PTTG1 expression is enhanced in metastatic lymph nodes in comparison to that in primary carcinomas. We suggest that PTTG1 may contribute to lymph node metastases in gastric carcinoma.

Gene expression profiling in intestinal-type gastric carcinoma by cDNA microarray

AIM: To identify a set of genes involved in the development of intestinal-type gastric carcinoma.

METHODS: Pure mRNAs from 6 cases of intestinal-type gastric carcinoma and corresponding noncancerous mucosae were reversely transcribed into cDNAs labeled with Cy5 and Cy3 dyes for probes, then mixed and hybridized with the cDNA microarray consisting of 4 096 genes, and the fluorescent signals were scanned.

RESULTS: Among total genes, 333 were up-regulated and 333 down-regulated in intestinal-type gastric cancer tissues. Within altered expression of those genes, cell-cycle regulators and growth factors were up-regulated, and the promoter genes of apoptosis were down-regulated; Oncogenes and cell-adhesion molecules were more up-regulated; The cancer progression genes were up-regulated, while the anti-cancer progression genes were down-regulated.

CONCLUSION: The quick and high-throughout method of gene expression profile by cDNA array provides us with an overview of gene changes that may involved in intestinal-type gastric cancer development, and will open up new possibilities to identify novel molecular targets for diagnosis and therapy. Several genes are altered in intestinal-type gastric cancer, which need to be further investigated.

Prognostic significance of the deleted in colorectal cancer gene protein expression in high-risk resected gastric carcinoma

The deleted in colorectal cancer (DCC) gene is a candidate tumor suppressor gene that may be associated with differentiation and proliferation of normal cells. Loss of heterozygosity (LOH) of 18q, where the gene is located, and absence of DCC protein expression have been associated with worse prognosis in certain subgroups of patients with colorectal adenocarcinoma. We studied the prognostic significance of loss-of-protein expression in 66 patients with resected gastric cancer with a high probability of relapse (T3, T4, N+). The DCC protein was detected with immunohistochemistry using an anti-DCC monoclonal antibody on paraffin-embedded sections. The DCC protein expression was present in 51 cases (77.3%) and absent in 15 cases (22.7%). Poorly differentiated and signet ring carcinomas had significantly lower expression than more differentiated tumors (p < 0.05) as did diffuse-type tumors compared to intestinal and mixed (p < 0.01). There was no correlation with proliferation rate, estimated immunohistochemically using an anti-proliferating cell nuclear antigen (PCNA) monoclonal antibody. Absence of DCC protein was an independent favorable prognostic factor (median survival 57 months vs. 18 months, p = 0.0176). The DCC protein expression was correlated with relapse site: all patients with distant metastases were positive for DCC staining, while one-third of patients with local/peritoneal relapse were negative (p < 0.01). In conclusion, DCC protein expression seems to be a significant prognostic factor in high-risk resected gastric cancer. Our results support previous data associating the DCC gene with differentiation and indicate that this gene may play a role in the metastatic potential of these tumors. These findings need to be confirmed by future larger studies.

Mutation and methylation of hMLH1 in gastric carcinomas with microsatellite instability

AIM: To appraise the correlation of mutation and methylation of hMSH1 with microsatellite instability (MSI) in gastric cancers.

METHODS: Mutation of hMLH1 was detected by Two-dimensional electrophoresis (Two-D) and DNA sequencing; Methylation of hMLH1 promoter was measured with methylation-specific PCR; MSI was analyzed by PCR-based methods.

RESULTS: Sixty-eight cases of sporadic gastric carcinoma were studied for mutation and methylation of hMLH1 promoter and MSI. Three mutations were found, two of them were caused by a single bp substitution and one was caused by a 2 bp substitution, which displayed similar Two-D band pattern. Methylation of hMLH1 promoter was detected in 11 (16.2%) gastric cancer. By using five MSI markers, MSI in at least one locus was detected in 17/68 (25%) of the tumors analyzed. Three hMLH1 mutations were all detected in MSI-H (≥ 2 loci, n = 8), but no mutation was found in MSI-L (only one locus, n = 9) or MSS (tumor lacking MSI or stable, n = 51). Methylation frequency of hMLH1 in MSI-H (87.5%, 7/8) was significantly higher than that in MSI-L (11.1%, 1/9) or MSS (5.9%, 3/51) (P < 0.01-0.001), but no difference was found between MSI-L and MSS (P > 0.05).

CONCLUSION: Both mutation and methylation of hMLH1 are involved in the MSI pathway but not related to the LOH pathway in gastric carcinogenesis.

Methylation of hMLH1 and hMSH2 promoter in colorectal cancer with microsatellite instability

AIM: To explore methylation of hMLH1 and hMSH2 promoter with microsatellite instability (MSI) in colorectal carcinomas.

METHODS: Methylation of hMLH1 and hMSH2 promoter was measured with methylation-specific PCR; MSI was analyzed by PCR-based methods.

RESULTS: No methylation of hMLH1 and hMSH2 promoter was found in 10 normal colorectal mucosas. Seventy-six cases of sporadic colorectal carcinoma were studied for methylation of hMLH1 and hMSH2 promoter and MSI. Methylation of hMLH1 promoter was detected in 8 (10.5%)colorectal carcinomas and none in hMSH2. Frequence of hMLH1 methylation on right-sided colorectal cancer (23.1%)was significantly higher than that on left one (4.0%, P < 0.05). MSI was detected in at least one locus in 26.3%(20/76) of the tumors analyzed with five microsatellite markers. Frequence of hMLH1 methylation in gastric cancer with MSI-H (80.0%)was significantly higher than that in gastric cancer with MSI-L (20.0%, P < 0.01) and with MSS (10.7%, P < 0.001).

CONCLUSION: Methylation of hMLH1 promoter is related to right-sided colorectal cancer and involved in the MSI pathway.

Loss of heterozygosity on chromosome 18 in microdissected gastric cancer cells

AIM: To detect loss of heterozygosity (LOH) on chromosome 18 in primary gastric carcinomas.

METHODS: Short insertion deletion polymorphism (SIDP) markers on chromosome 18 were analyzed using high fidelity-whole genome amplification (HF-WGA) and denatured high pressure liquid chromotography (DHPLC) to detect LOH in gastric cancer cells purified by laser capture microdissection (LCM).

RESULTS: LOH in 3 (MID148, MID150 and MID352) of 9 SIDP loci was found. Three of 10 samples of gastric cancer showed LOH at the same SIDP locus (MID150) (30%) and one of them also demonstrated LOH at the other 2 SIDP loci (MID148, MID352). No LOH was detected in 6 of 9 SIDP loci.

CONCLUSION: Detection of LOH in cancer cells can be achieved by the combination of LCM, HF-WGA and the analysis of SIDP marker by DHPLC. This study provides an alternative new way to map tumor suppressor genes on chromosome 18.

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Chromosome 2p, 3p, 5q and 18q status in sporadic gastric cancer

AIM

The genetic make-up of gastric cancers in low-risk population groups from South Africa is largely unknown. The purpose of this study was to ascertain the incidence of microsatellite instability and loss of heterozygosity in this population.

METHODS

Thirty-seven gastrectomy specimens for sporadic gastric cancer were analysed for the following clinicopathological parameters: age, gender, race, histopathological type, size of tumour, lymph node status and the presence/absence of Helicobacter pylori. DNA was then extracted from paraffin-embedded tissue and seven microsatellite markers in 2p, 3p, 5q and 18q loci were examined using automated DNA fluorescent technology.

RESULTS

Only eight cases showed microsatellite instability (MSI) for one marker and were thus categorised as MSI-low. In the 3p region, loss of heterozygosity (LOH) was detected in 21.7-38.3% of informative cases, whilst in the 18q region CLOH ranged from 25 to 38.4%. LOH was not seen in the 2p locus and only one case showed LOH in the 5q region. When the molecular changes were compared with clinicopathological parameters, a statistically significant relationship did not emerge with any single parameter.

CONCLUSIONS

This study shows that sporadic gastric cancer from a low-risk population in South Africa is MSI-low or MSI-stable, and that LOH in the 3p and 18q regions is similar to that seen in other low-risk populations from different geographical regions.

The relationship between gastric cancer cells circulating in the blood and microsatellite instability positive gastric carcinomas

BACKGROUND

Cancers characterized by microsatellite instability may be biologically different from their counterparts with stable microsatellite sequences. Circulating cancers cell present in blood prior to surgery may constitute an adverse prognostic finding.

AIM

To correlate these two phenomena with morphological features and survival in advanced gastric cancer.

METHODS

We examined 76 cases of resected sporadic, advanced gastric cancer by means of routine morphology and a panel of microsatellite markers. Sixty-six cases were screened for presence of cancer cells circulating in blood prior to the surgery using combined morphological and immunocytochemical approach.

RESULTS

Twenty-one (27.6%) cases demonstrated microsatellite instability in at least one locus. Among them 11 (14.5%) showed microsatellite instability in more than 30% (4/12) examined loci, and they were therefore designated as replication error positive (RER+). Circulating cancer cells were detected in 2/19 microsatellite instability and in 11/47 remaining cases (difference not significant). The survival of the microsatellite instability cases was significantly better. The presence of circulating cancer cells did not correlate with survival.

CONCLUSION

It is possible that the microsatellite instability status, but not circulating cancer cells, constitutes a prognostic predictive factor in advanced gastric carcinoma. Confirmation of this hypothesis requires continuation of patient follow-up.

Atrophy-metaplasia-dysplasia-carcinoma sequence in the stomach: a reality or merely an hypothesis?

The results of recent investigations have suggested that the old hypothesis of an atrophy-metaplasia-dysplasia-carcinoma sequence in the stomach needs to be qualified. The most common cause of intestinal metaplasia is Helicobacter pylori gastritis. The consequence of this intestinal metaplasia is focal atrophy. Helicobacter pylori infection may also trigger an autoimmune gastritis of the corpus mucosa, with atrophy and intestinal metaplasia. Most intestinal metaplasias are only 'paracancerous' but not 'precancerous' lesions. Diffuse gastric carcinomas, such as the signet ring cell carcinoma, arise independently of intestinal metaplasia. Histogenetically, numerous carcinomas of the stomach are primarily of the gastric type, and may secondarily change into the intestinal type.High-grade intra-epithelial neoplasias (dysplasias) detected during the biopsy-based diagnostic work-up appear to be a marker for carcinoma and must, therefore, be removed endoscopically. The detection of intestinal metaplasia in routinely obtained biopsy material is subject to sampling error and is, therefore, not a suitable marker for an increased risk of a gastric carcinoma developing. As an alternative, the concept of gastritis of the carcinoma phenotype, which is more frequently found in early gastric carcinomas and in the relatives of gastric carcinoma patients, has been developed. In this concept, the diffuse parameters of grade and activity of the gastritis in the antrum and corpus, which are independent of sampling error, are subjected to a comparative analysis. A risk gastritis of the carcinoma phenotype is diagnosed when the grade and activity of the gastritis in the corpus are at least equally as pronounced as in the antrum. Currently, this concept is being tested in a prospective ongoing study. Future studies must show whether, and if so which, immunohistochemical or molecular-genetically detectable changes can be applied as risk markers in the diagnostic work-up. Helicobacter pylori eradication probably does not lead to complete regression of the intestinal metaplasia and ensuing focal atrophy. However, eradication of H. pylori does lead to the normalization of changes that can lead to mutations of the stem cells of the gastric mucosa (free radicals, nitric oxide, cell proliferation and vitamin C secretion).

Telomere erosion is independent of microsatellite instability but related to loss of heterozygosity in gastric cancer

AIM: To correlate the length of the telomere to microsatellite instability (MSI) and loss of heterozygosity (LOH) of APC, MCC and DCC genes in gastric carcinomas.

METHODS: Telomeric restriction fragment (TRF) length of gastric cancer was measured with Southern blot. LOH of APC, MCC and DCC genes, microsatellite instability (MSI) and frameshift mutation of hMSH6, TGF-βRII and BAX genes were analyzed by PCR-based methods.

RESULTS: Sixty-eight cases of sporadic gastric carcinoma were studied for MSI using five microsatellite markers. MSI in at least one locus was detected in 17 (25%) of 68 tumors analyzed. Frameshift mutations of hMSH6, TGF-βRII and BAX were detected in 2, 6 and 3 of gastric carcinomas respectively showing high MSI (≥ 2 loci, n = 8), but none was found in those showing low MSI (only one locus, n = 9) or MSS (tumor lacking MSI or stable, n = 51). Thirty-five cases, including all high MSI and low MSI, were studied for TRF. The mean TRF length was not correlated with clinicopathological parameters. No association was observed between TRF length and MSI or frameshift mutation. On the contrary, LOH at the DCC locus was related to telomere shortening (P < 0.01). This tendency was also observed in APC and MCC genes, although there was no statistical significance.

CONCLUSION: The development of gastric cancer can arise through two different genetic pathways. In high MSI gastric cancers, defective mismatch repair allows mutations to accumulate and generate the high MSI phenotype. In gastric cancers showing either low MSI or MSS, multiple deletions may represent the LOH pathway. Telomere erosion is independent of high MSI phenotype but related to the LOH pathway in gastric cancer.

Altered mucin expression in the gastrointestinal tract: a review

Early studies of changes in mucin expression in disorders of the gastrointestinal tract focused on alterations in the carbohydrate chain. This review briefly considers the various mechanisms by which such alterations may come about: (a) normal variation, (b) sialic acid alterations, (c) defective assembly of carbohydrate side-chains, (d) changed expression of core proteins and (e) epithelial metaplasia. The availability of monoclonal antibodies to mucin core proteins adds a new dimension to mucin histochemistry. It is now possible to offer explanations for traditional mucin histochemical findings on the basis of lineage-specific patterns of mucin core protein expression. Changes in core protein expression are described in inflammatory, metaplastic and neoplastic disorders of the gastrointestinal tract. The possibility that mucin change could be important in the aetiology of some diseases such as ulcerative colitis and H. pylori gastritis is considered. It is more probable, however, that changes in mucin expression are secondary to reprogramming of cellular differentiation and altered cell turnover. As such they may serve as markers to explain pathogenesis and provide novel diagnostic and prognostic information.