Microsatellite Instability In Gastric Cancer Research Articles

Microsatellite Instability of Nuclear and Mitochondrial DNAs in Gastric Carcinogenesis

Genetic instability contributes to the development and progression of gastric cancer, one of the leading causes of cancer death worldwide. Microsatellite instability (MSI) has been hypothesized to be involved in carcinogenesis, althgough its mechanisms and exact roles in gastric cancer remain largely unknown. Our aim was to identify associated clinicopathological characteristics and prognostic value of MSI in gastric cancer and precancerous lesions including gastritis, metaplasia, dysplasia, and adenoma. Because mitochondrial DNA has a different genetic system from nuclear DNA, the results of both nuclear MSI and mitochondrial MSI in gastric cancer were reviewed. This review provides evidence that genetic instability of nuclear and mitochondrial DNAs contributes to early stages of gastric carcinogenesis and suggests possible roles in predicting prognosis.

Low-frequency microsatellite instability in genomic di-nucleotide sequences correlates with lymphatic invasion and poor prognosis in gastric cancer.

The clinical significance of low-frequency microsatellite instability (MSI-L) in gastric cancer (GC) has not been well established. The aim of this study was to evaluate the clinicopathological features of MSI-L in GC. We investigated microsatellite instability (MSI) in 5 di-nucleotide repeat sequences in 210 unselected GC patients. High-resolution fluorescent microsatellite analysis assay was utilized to detect MSI. Clinicopathological variables were compared among groups with different microsatellite statuses. The overall survival (OS) was analyzed by Kaplan-Meier method. Multivariable analysis was performed to identify prognostic factors and variables correlated with lymph node metastasis. High-frequency microsatellite instability (MSI-H), MSI-L, and microsatellite stable were identified, respectively, in 10.5, 10.0, and 79.5% of unselected GC cases. Tumors with MSI-H were less invasive, and these patients showed a better OS. MSI-L was correlated with more advanced tumor Node Metastasis stage, and more frequent lymph node metastasis. The unfavorable prognosis predicted by MSI-L was ascribed to its correlation with lymphatic invasion. MSI-L characterized by di-nucleotide markers represents a distinct subcategory of GC with aggressive clinicopathological features, which are particularly affiliated to lymphatic system and correlated with a poor prognosis. MSI-L could be beneficial for predicting the clinical outcome of GC.

Is microsatellite instability a prognostic marker in gastric cancer? A systematic review with meta-analysis.

The relationship between survival in gastric cancer patients and the status of microsatellite instability (MSI) has not yet been established. The purpose of this meta-analysis was to obtain integrated and more precise data for the value of MSI as a prognostic marker in gastric cancer. A comprehensive systematic review and meta-analysis were conducted using major electronic databases (PubMed, EMBASE, and the Cochrane Central) with keywords related to "microsatellite instability," "gastric cancer," and "prognosis." Twenty-four studies with 5,438 participants (712 cases were MSI gastric cancer) were included for pooling risk estimates of MSI in gastric cancer. Seventeen studies reported overall survival. The pooled hazard ratio (HR) for overall survival of MSI vs. non-MSI was 0.72 (95%CI: 0.59-0.88, P = .001) in a random-effects model. In the sensitivity analysis, the result from the most recent study showed the most heterogeneity. MSI gastric cancer was associated with good prognosis but there was heterogeneity in the recent studies. Changed epidemiology and effects of chemotherapy are potential causes of heterogeneity. Establishing a consensus for defining MSI in gastric cancer should be preferred for future studies.

Causes and consequences of microsatellite instability in gastric carcinogenesis.

Loss of DNA mismatch repair (MMR) function, due to somatic or germline epi/genetic alterations of MMR genes leads to the accumulation of numerous mutations across the genome, creating a molecular phenotype known as microsatellite instability (MSI). In gastric cancer (GC), MSI occurs in about 15% to 30% of the cases. This review summarizes the current knowledge on the molecular mechanisms underlying the acquisition of MSI in GC as well as on the clinic, pathologic and molecular consequences of the MSI phenotype. Additionally, current therapeutic strategies for GC and their applicability in the MSI subset are also discussed.

Mutation at Intronic Repeats of the Ataxia-Telangiectasia Mutated (ATM) Gene and ATM Protein Loss in Primary Gastric Cancer with Microsatellite Instability

Ataxia-telangiectasia mutated (ATM) is a Ser/Thr protein kinase that plays a critical role in DNA damage-induced signaling and initiation of cell cycle checkpoint signaling in response to DNA-damaging agents such as ionizing radiation. We have previously reported the ATM protein loss by immunohistochemistry (IHC) in 16% of human gastric cancer (GC) tissue. We hypothesized that ATM gene intron mutations targeted by microsatellite instability (MSI) cause ATM protein loss in a subset of GC. We studied mononucleotide mutations at the intron of ATM gene, ATM IHC and MSI in GC. Ten human gastric cancer cell lines were studied for the ATM gene mutation at introns, RT-PCR, direct sequencing, and immunohistochemistry. GC tissues of 839 patients were analyzed for MSI and ATM IHC. Among them, 604 cases were analyzed for the ATM mutations at introns preceding exon 6, exon 10 and exon 20. Two human GC cell lines (SNU-1 and -638) showed ATM intron mutations, deletion in RT-PCR and direct sequencing, and ATM protein loss by IHC. The frequencies of ATM mutation, MSI, and ATM protein loss were 12.9% (78/604), 9.2% (81/882) and 15.2% (134/839), respectively. Analysis of associations among MSI, ATM gene mutation, and ATM protein loss revealed highly co-existing ATM gene alterations and MSI. ATM intron mutation and ATM protein loss were detected in 69.3% (52/75) and 53.3% (40/75) of MSI positive GC. MSI positivity and ATM protein loss were present in 68.4% (52/76) and 48.7% (37/76) of GC with ATM intron mutation. ATM mutation and ATM protein loss had characteristics of old age, distal location of tumor, large tumor size, and histologic intestinal type. Our study might be interpreted as that ATM gene mutation at intron might be targeted by MSI and lead to ATM protein loss in a selected group of GC.

Ataxia‐telangiectasia‐mutated protein expression with microsatellite instability in gastric cancer as prognostic marker

The prognostic significance of ataxia-telangiectasia-mutated (ATM) expression in gastric cancer remains unclear. The functional loss of ATM gene exhibits a biologic correlation with microsatellite instability (MSI). In this study, we investigated the significance of ATM expression with MSI by evaluating gastric cancer patients who had underwent curative resection. ATM expression was classified into low ATM expression (-, ±, +) and high ATM expression (++, +++) using immunohistochemistry analysis. MSI status was classified as MSI-negative (MSS, MSI-low) and MSI-positive (MSI-high). Of 321 patients, 205 (63.9%) exhibited low ATM expression and 116 (36.1%) exhibited high ATM expression. Low ATM expression was more frequently identified in patients of older age, more advanced stage and with MSI-positive tumor (p = 0.025, p = 0.001 and p = 0.014, respectively). The probability of 5-year disease-free survival (DFS) and overall survival (OS) was lower in low ATM expression group compared with the high ATM expression group (DFS: 62.5%, 76.4%, p = 0.017, OS: 65.9%, 78.5%, p = 0.027, respectively). According to MSI status, a subgroup of MSI-negative and low ATM expression cases exhibited the worst prognosis for DFS and OS; this subgroup also exhibited poorer DFS according to multivariable analysis (hazard radio = 1.8, 95% confidence interval, 1.2-2.8, p = 0.010), although prognostic value of ATM expression alone did not remain in the multivariable analysis. Taken together, these findings indicate that ATM expression with MSI status is an independent factor for gastric cancer prognosis in gastric cancer patients who received curative surgery.

Allelic imbalance of 17p13.1 (TP53), 1p36.1 (RUNX3), and 16p22 (CDH1) loci and microsatellite instability in gastric cancer

Allelic imbalance and microsatellite instability in operating materials from 78 patients with gastric cancer was studied. Microsatellite polymorphism for 17p13.1 (TP53), 1p36.1 (RUNX3), 16p22 (CDH1), and MH (BAT26) was determined in tumor and adjacent (morphologically normal) tissues of gastric mucosa. The allelic imbalance of 17p13.3 (p = 0.0176) and 16p22 (p = 0.023) loci by two and more loci in a single sample (p = 0.0176), as well as microsatellite instability (p = 0.047), is observed significantly more frequently in intestinal types of tumors than in tumors of a diffuse type. During the comparison of clinical groups with different degrees of tumor-cell differentiation, it was demonstrated that allelic imbalance by 16p22 locus (p = 0.041) and by two and more loci in a single sample (p = 0.0057) is observed more frequently in highly differentiated or moderately differentiated tumors. We did not detect significant differences in the groups of patients with metastases (or without them) in regional lymphatic nodes with different localizations and at different stages of the tumor process.

Gastric cancers with microsatellite instability sharing clinical features, chemoresistance and germline MSH6 variants.

Recent studies suggest that colorectal cancer with microsatellite instability (MSI) might be resistant to fluorouracil-based chemotherapy; however, little is known about the clinical significance of MSI analysis for gastric cancer. We therefore conducted a prospective single center study analyzing MSI in gastric cancer. Of 123 consecutive gastric cancers analyzed, 12 (9.8%) were MSI-positive and two patients with MSI-positive gastric cancer underwent systemic chemotherapy because of unresectable disease. Neither cases had concurrent nor past history of other malignancies but one had cancer family history meeting the revised Bethesda criteria. These two MSI-positive gastric cancers shared multiple clinical features, such as direct invasion to adjacent organs, extensive nodal metastasis but no distant metastasis, resistance to fluorouracil and death of tumor bleeding. The two cases had unmethylated MLH1 promoter, suggestive of Lynch syndrome. Germline mutation analysis demonstrated MSH6 alterations of unknown significance in both cases.

Gastric cancers with microsatellite instability exhibit high fluorodeoxyglucose uptake on positron emission tomography

Gastric cancers exhibit various degrees of (18)F-fluorodeoxyglucose (FDG) uptakes on positron emission tomography/computed tomography (PET/CT) imaging. The aim of this study was to evaluate whether FDG uptake in gastric cancer varies according to the microsatellite instability (MSI) status. Consecutive gastric cancer patients who underwent PET/CT imaging and MSI analysis were included in the study. The maximum standardized uptake value (SUVmax) of gastric cancer was assessed using PET/CT imaging. Of 131 gastric cancers, 16 exhibited a high incidence of MSI (MSI-H) and 3 exhibited a low incidence of MSI (MSI-L). In 29 subjects who showed no uptake on PET/CT imaging the gastric cancers were all microsatellite stable (MSS). Gastric cancers with MSI were related to age older than 60 years (p = 0.002), cancer volume larger than 10 cm(3) (p = 0.015), and the presence of FDG uptake on PET/CT imaging (p = 0.001). A higher SUVmax of gastric cancer was linked to the presence of MSI (p < 0.001). The presence of MSI is related to FDG uptake in gastric cancer. Care should be taken with MSS gastric cancers, because they show lower SUVmax on PET/CT imaging than MSI gastric cancers.

Oncogenic mutations in gastric cancer with microsatellite instability

AimMitogen-activated protein kinase (MAPK) cascade and phosphatidylinositol 3-kinase (PI3K) survival pathways are frequently activated in the progression of gastrointestinal malignancies. In this study, we aimed to determine the frequency of gene mutations in members of these pathways – Epithelial Growth Factor Receptor (EGFR), KRAS, BRAF, PIK3CA and MLK3 in a series of 63 gastric carcinomas with high levels of microsatellite instability (MSI). MethodsGene mutation analysis was performed by PCR amplification followed by direct sequencing. In selected tumour cases, EGFR expression was evaluated by immunohistochemistry. Association studies between molecular data and clinicopathologic characteristics were performed. ResultsMutations in EGFR (3′-untranslated region [UTR] polyA repeat), KRAS, PIK3CA and MLK3 genes occurred in 30 (47.6%), 11 (17.5%), 9 (14.3%) and 2 (3.2%) of the MSI gastric cancer (GC) cases, respectively. No BRAF or EGFR hotspot mutations were identified. Overall, mutations in at least one of these genes were found in 55.6% (35/63) of gastric carcinomas. From those mutant cases 40.0% (14/35) of them had concomitant gene mutations, always involving EGFR polyA deletions. Interestingly, we observed significant associations between oncogenic mutations and female gender (p=0.046) old age of diagnosis (p=0.001) and intestinal subtype (p=0.043). ConclusionOur results show that MSI gastric carcinoma frequently shows activation of EGFR-MAPK and PI3K pathways. Within all alterations found, deletions of the A13 repeats of EGFR were common, suggesting this molecular event as an important biomarker for stratification of GC patients for treatment with EGFR inhibitors.

788 Investigation of the differentially expressed C-FABP & FABP-pm in human prostate tissues and cell lines: histopathological and molecular biology study

Gastric cancer (GC) remains a leading cause of cancer mortality worldwide. Genetic factors are implicated, including DNA mismatch repair (MMR) deficiency manifested as tumor microsatellite instability (MSI). However, a standardized panel of markers and a definition of low-versus-high level MSI in GC are lacking. We examined a population-based cohort of early onset (≤50 yrs) gastric cancer. We identified 211 cases of early onset gastric cancer in Central-East Ontario from 1989 to 1993, with archival material available for 139 cases. Testing included a six-mononucleotide marker panel and a three-MMR immunohistochemical panel. Overall, 30% (41 of 139) of GC were MSI+, with allelic shifts at one to eight markers. An unexpected discordance between the BAT-25, BAT-26, and BAT-40 markers was observed in the MSI+ cases. Six cases showing multiple loci instability (≥3 markers MSI+/MSI-high) demonstrated MMR protein deficiency. Three novel hMLH1 mutations (two germline frameshift and one somatic nonsense) were also found. The only significant clinicopathological associations were increased tumor size in MSI+ cases (P = 0.04) and Lauren histotype (P = 0.006) and tumor grade (P = 0.007) in MSI-high cases. Tumor size, location, depth, nodal status, and Ming subtype were significant prognostic variables. Therefore, we propose a new definition of high-level MSI based on unifying characteristics of instability of more than or equal to three of six mononucleotide markers and loss of MMR protein expression.

Mitochondrial microsatellite instability in gastric cancer and gastric epithelial dysplasia as a precancerous lesion

Background: Genetic instability in gastric cancer represents a key molecular step that occurs early in the carcinogenesis process. To clarify the role of genetic instability in the progression from gastric dysplasia to gastric cancer, mitochondrial microsatellite instability (mtMSI) was studied in gastric cancer and gastric dysplasia. Methods: DNA was isolated from paired normal and tumoral tissues in 24 patients with gastric dysplasia (low grade) and 49 patients with gastric cancer. mtMSI was analyzed using eight microsatellite markers. mtMSI in gastric dysplasia was studied prospectively to elucidate the relation between mtMSI and gastric carcinogenesis. Results: mtMSI was found in 5 (10.2%) of 49 gastric cancer patients. The mtMSI phenotype was not associated with age, gender, and Helicobacter pylori infection. However, all of the mtMSI was found in intestinal-type gastric cancer (20.8%, p = 0.02). In gastric dysplasia, mtMSI was detected in 3 (12.5%) of 24 patients with gastric dysplasia. mtMSI-positive gastric dysplasia showed a poor prognosis statistically compared to mtMSI negative through progression to high-grade dysplasia or gastric cancer. Conclusions: These data suggest that mtMSI may be an early and important event in the progression of gastric carcinogenesis, especially in intestinal-type gastric cancer.

Evidence of tumor microsatellite instability in gastric cancer with familial aggregation

About 90% of gastric cancer (GC) cases appear in a sporadic setting. Nonetheless, in high incidence areas high familial aggregation rates have been recently described. Microsatellite instability (MSI) is thought to be an important molecular phenotype both in sporadic GC and in tumors of the HNPCC spectrum. The aim of this study was to assess the frequency of MSI in GC with familial aggregation. Five quasimonomorphic mononucleotide repeats (BAT-26, BAT-25, NR-24, NR-21 and NR-27) were analyzed in 250 GC patients. Seventy-five patients (30%) had at least one-first-degree family member affected by GC and 63 patients (25.2%) showed MSI. The frequency of MSI was significantly higher in patients with a positive family history of GC (38.7%) compared to patients with other tumor types within the family (15.7%) or with a negative oncological familial history (21.9%, P = 0.004). Within cases with a positive familial oncological history, the MSI frequency in families with GC only was similar to the one observed in families with GC and colon cancer (P = 0.96). Nonetheless, in families with GC and lung cancer, the frequency of MSI was significantly lower (5.6%, P = 0.007). MSI occurs in GCs with familial aggregation. Similar MSI rates have been observed in GC patients with other family members affected by GC or colon cancer. The same does not occur in families with other members affected by lung cancer. Our data seem to suggest that familial aggregation for either GC alone or gastric and colon cancer share common etiological factors in contrast to families with gastric and lung cancers.

Checkpoint with forkhead-associated and ring finger promoter hypermethylation correlates with microsatellite instability in gastric cancer

To examine the methylation status of the promoter region of the checkpoint with forkhead-associated and ring finger (CHFR) and microsatellite mutator status in 59 primary gastric cancers. We investigated the promoter methylation of CHFR in 59 cases of gastric cancer using methylation-specific PCR. Five microsatellite loci were analyzed using high-intensity microsatellite analysis reported previously, and p53 gene mutations were investigated by direct sequencing. Twenty cases (33.9%) showed promoter methylation and no relation was observed with the clinicopathological factors. We found that the promoter methylation of CHFR was frequently accompanied with microsatellite instability (MIN). Seven of 20 (35.0%) cases showed MIN in hypermethylation of the CHFR tumor, while three of 39 (7.7%) cases showed MIN in the non-methylated CHFR tumor (P < 0.01). However, we failed to find any relationship between CHFR methylation and p53 mutation status. The coordinated loss of both the mitotic check point function and mismatch repair system suggests the potential to overcome the cell cycle check point, which may lead to an accumulation of mutations. However, the p53 mutation was not related to hypermethylation of the CHFR promoter and MIN, which indicates that an abnormality in p53 occurs as an independent process from the mismatch repair deficiency in carcinogenesis.

Detection of microsatellite instability in gastric cancer and dysplasia tissue in Lanzhou province of China

Detection of microsatellite instability in gastric cancer and dysplasia tissue in Lanzhou province of China

Changes in microsatellite instability in gastric cancer and precancerous lesions

Changes in microsatellite instability in gastric cancer and precancerous lesions

Changes of tumor suppressor gene PTEN and microsatellite instability in gastric cancer and precancerous lesion and their correlations

Changes of tumor suppressor gene PTEN and microsatellite instability in gastric cancer and precancerous lesion and their correlations

High-resolution fluorescent analysis of microsatellite instability in gastric cancer

Microsatellite instability (MSI) is associated with various human malignancies and regarded as reflecting cellular deficiency in DNA mismatch repair (MMR). Analysis of MSI has been prevalent in the field of oncology, and numerous data have accumulated in the literature. It has been reported that the MSI+ phenotype is relatively frequent in gastric cancer. The reported frequencies of MSI+ gastric tumors, however, are diverse. To determine the frequencies of the MSI+ phenotype and defective MMR in gastric cancer, we examined tumors derived from 167 patients with sporadic gastric cancer, using our unique fluorescent technique, 'high-resolution fluorescent microsatellite analysis'. High-resolution fluorescent microsatellite analysis allowed us the unequivocal designation of MSI. The frequencies of MSI-H and MSI-L were 11 and 9.6%, respectively. In addition to the distinction based on the frequency of microsatellite changes, MSI was classifiable into two distinct categories, type A and type B, according to the mode of length changes in the dinucleotide microsatellites. Type A and type B MSI were observed in 14 and 6.6%, respectively. The overall frequency of MSI was 21%. Intriguingly, MSI did not correlate with any of commonly used clinicopathological variables. In addition, neither MSI-H nor MSI-L correlated with family history of malignancies or patient history of multiple cancers. Instead, type B MSI was significantly more frequent in patients with family history of gastric cancer. Type A MSI appeared to occur more frequently in tumors of patients with a history of double cancer, which, however, was not statistically significant. In gastric cancer, contribution of defective MMR to the risk of multiple cancer or familial predisposition appears more limited than has been expected. The relationship between MSI and high risk of cancer may have been oversimplified, at least in gastric cancer.

Birt-Hogg-Dubé (BHD) gene mutations in human gastric cancer with high frequency microsatellite instability

Birt–Hogg–Dubé (BHD) syndrome is a rare inherited genodermatosis characterized by benign hamartomatous skin lesions and an increased risk of pneumothorax and renal tumors. Many of the patients harbor insertion/deletion mutations in the hypermutable poly(C) 8 tract in exon 11 of the BHD gene. This mutational hot spot is also reported to be a target of mutation in microsatellite instability (MSI) sporadic colorectal tumors. To test if the BHD gene is a potential mutational target in gastric cancer, we screened for mutations in all of the coding exons of the BHD gene in 30 cases of MSI gastric cancer as well as 50 cases of microsatellite stable (MSS) gastric cancer. Mutations in the poly(C) 8 tract of BHD were detected in 3 of 19 MSI-high cases (15.8%), and none of 11 MSI-low cases. All BHD mutated cases also showed mutations of both BAX and TGFβRII. No mutations were detected in the other exons of the BHD gene. No BHD mutations were found in MSS gastric cancer cases. Taken together, these findings show that the BHD gene is a rare target in MSI-high gastric cancer, and BHD mutation tends to occur downstream in the mutational events of other major MSI-high target genes.

High EPHB2 mutation rate in gastric but not endometrial tumors with microsatellite instability

The EPH/EFN family of receptor tyrosine kinases regulates cell adhesion and migration and has an important role in controlling cell positioning in the normal intestinal epithelium. Inactivation of EPHB2 has recently been shown to accelerate tumorigenesis in the colon and rectum, and we have previously demonstrated frequent frameshift mutations (41%) in an A9 coding microsatellite repeat in exon 17 of EPHB2 in colorectal tumors with microsatellite instability (MSI). In this study, we extended these analyses to extracolonic MSI cancers, and found frameshift EPHB2 mutations in 39% (25/64) of gastric tumors and 14% (8/56) of endometrial tumors. Regression analysis of these EPHB2 mutation data on the basis of our previously proposed statistical model identified EPHB2 as a selective target of frameshift mutations in MSI gastric cancers but not in MSI endometrial carcinomas. These results suggest a functional role for EPHB2 in gastric tumor progression, and emphasize the differences between the tumorigenic processes in MSI gastrointestinal and endometrial cancer.