Mutation and methylation of hMLH1 in gastric carcinomas with microsatellite instability

Prevalence of microsatellite instable and Epstein-Barr Virus-driven gastroesophageal cancer in a large Belgian cohort

Introduction

Patients with gastroesophageal adenocarcinoma (GEC) with microsatellite instability-high (MSI-H) or Epstein Barr Virus positivity (EBV+) might be good candidates for immunotherapy. Incidences of about 10% have been reported for both features, but are dependent on geographical region and disease stage.

Aim

The aim is to study the prevalence of MSI-H and EBV+ in a Belgian single center cohort of patients with GEC.

Methods

We retrospectively assessed the files of all patients with a newly diagnosed GEC between August, 1st 2018 and February, 29th 2020 at the University Hospitals Leuven, Belgium. Microsatellite instability (MSI) status was determined using immunohistochemistry (IHC) and polymerase chain reaction (PCR). EBV+ was assessed using in situ hybridization (ISH). A case report is provided to illustrate the importance of testing for MSI in GEC.

Results

247 gastroesophageal adenocarcinomas were included in this analysis. 62 (56% stage IV) of those were tested for EBV, but only 1 turned out to be EBV positive (1.6%). 116 patients (44.0% stage IV) were tested for MSI, of which 11 were MSI-H (9.5%). Half of the MSI-H tumors identified were at the gastroesophageal junction (GEJ). A patient with MSI-H metastatic GEC obtained a complete response with nivolumab, which persisted after discontinuation of treatment.

Conclusion

While we confirm that about 10% of GECs are MSI-H, the incidence of EBV+ in our cohort (1.6%) is clearly lower than expected. Given the important prognostic and predictive implications, every gastroesophageal cancer should be tested for MSI.

TRIM37 contributes to malignant outcomes and CDDP resistance in gastric cancer

Background: TRIM37 (Tripartite Motif Containing 37) is an E3 ubiquitin ligase for histone H2A and inhibits transcription in several genes. However, it is not known whether it plays a role in gastric cancer (GC). In this study, we tested whether TRIM37 acts as a cancer-promoting factor by being overexpressed in GC. Methods: We analyzed GC cell lines and 124 primary tumors, which were curatively resected in our hospital between 2001 and 2003. Results: Overexpression of the TRIM37 protein was detected in almost all GC cell lines and GC samples (76 out of 124 cases) and was significantly correlated with lymphatic and venous invasion, advanced T-Stage, N-Stage, histology and high recurrence rate. Patients with TRIM37 overexpressing tumors had a worse survival rate than those with non-expressing tumors (P=0.0057). Moreover, TRIM37 positivity was identified as an independent factor predicting worse outcomes (P=0.018, Hazard ratio 3.41). The apoptotic cell analysis showed that the knockdown of TRIM37 increased apoptosis in comparison with the control. In TRIM37 overexpressing GC cells, knockdown of TRIM37 suppressed the migration and invasion. Conclusions: TRIM37 plays a crucial role in tumor malignant potential through its overexpression and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

Essential updates 2017/2018: Recent topics in the treatment and research of gastric cancer in Japan

Recent developments in diagnostic technology, accumulated clinical effort and established evidence have boosted early detection and drastically improved early and long-term outcomes of gastric cancer. However, gastric cancer continues to be one of the most aggressive and life-threatening malignancies among all cancers and is a global health problem. Between January 2017 and December 2018, various fascinating reports of managements and research were published, including the new 15th Japanese Classification of Gastric Carcinoma reflecting the 8th American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) tumor, node and metastasis (TNM) classification (October 2017) and the new Gastric Cancer Treatment Guidelines version 5 (January 2018). Moreover, pivotal molecular features of gastric cancer were clarified by the worldwide cancer genome project, and various treatment targets and biomarkers such as circulating DNAs and microRNAs were detected. Novel treatment options using programmed cell death protein 1 immune checkpoint inhibitors have been started. In this review, we summarize the recent topics of classification, guidelines, and clinical and basic research in order to bring new insights to gastric cancer treatment.

Microsatellite Instability and Altered Expressions of MLH1 and MSH2 in Gastric Cancer

Introduction: Microsatellite instability (MSI) is a hallmark of defective DNA mismatch repair (MMR) of genes especially MLH1 and MSH2. It is frequently involved in the carcinogenesis of various tumours including gastric cancer (GC). However, MSI in GCs have not been reported in Malaysia before. Objective: This study was conducted to determine the microsatellite instability (MSI) status in gastric cancer by microsatellite analysis, sequencing, its association with MLH1 and MSH2 protein expression and H.pylori infection by immunohistochemistry. Method: A total of 60 gastric cancer cases were retrieved. DNA was extracted from paired normal and tumour tissues while MLH1 and MSH2 protein expression as well as H. pylori status were determined by IHC staining. For microsatellite analysis, polymerase chain reaction (PCR) was performed for paired tissue samples using a panel of five microsatellite markers. MSI-positive results were subjected for DNA sequencing to assess mutations in the MLH1 and MSH2 genes. Results: Microsatellite analysis identified ten MSI positive cases (16.7%), out of which only six cases (10.3%) showed absence of MLH1 (n=3) or MSH2 (n=3) protein expression by IHC. The most frequent microsatellite marker in MSI positive cases was BAT26 (90%). Nine of ten MSI positive cases were intestinal type with one diffuse and all were located distally. H. pylori infection was detected in 13 of 60 cases (21.7%) including in three MSI positive cases. All these results however were not statistically significant. Our sequencing data displayed novel mutations. However these data were not statistically correlated with expression levels of MLH1 and MSH2 proteins by IHC. This may be due to small sample size to detect small or moderately sized effects. Conclusion: The frequency of MSI in this study was comparable with published results. Determination of affected MMR genes by more than two antibodies may increase the sensitivity of IHC to that of MSI analysis.

Overexpression of YEATS4 contributes to malignant outcomes in gastric carcinoma

YEATS domain containing 4 (YEATS4) has functions of chromatin modification and transcriptional regulation and is in a gene-amplified region (12q13) in various human cancers. In this study, we tested whether YEATS4 acts as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC). We analyzed 5 GC cell lines and 135 primary tumor samples of GC, which were curatively resected in our hospital. Overexpression of the YEATS4 protein was frequently detected in GC cell lines (5/5 cell lines, 100%) and primary GC tumor tissues (32/135 cases, 23.7%). Knockdown of YEATS4 inhibited proliferation, migration and invasion of GC cells through NOTCH2 down-regulation in a TP53 mutation-independent manner, and induced apoptosis in wild-type TP53 GC cells. Moreover, knockdown of YEATS4 improved chemosensitivity for CDDP and L-OHP. Overexpression of YEATS4 protein significantly correlated with more aggressive lymphatic invasion, larger tumor size, deeper tumor depth, positive lymph node metastasis and recurrence. Patients with YEATS4-overexpressing tumors had a lower overall survival rate than those with non-expressing tumors. Multivariate analysis demonstrated that YEATS4 was independently associated with poor outcomes. These findings suggest that YEATS4 plays a pivotal role in tumor malignant potential through its overexpression and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

Overexpression of ZRF1 is related to tumor malignant potential and a poor outcome of gastric carcinoma

Zuotin-related factor 1 (ZRF1) is a recently characterized epigenetic factor involved in transcriptional regulation and is highly overexpressed in several malignancies, but it is not known whether it plays a role in gastric cancer (GC). In this study, we investigated whether ZRF1 acts as a cancer-promoting gene through its activation/overexpression in GC. We analyzed five GC cell lines and 133 primary tumors, which had been curatively resected in our hospital between 2001 and 2003. Overexpression of ZRF1 was detected in GC cell lines (four out of five lines, 80.0%) and was detected in primary tumor samples of GC (52 out of 133 cases, 39.1%) and significantly correlated with differentiated histological type, venous invasion, lymphatic invasion, advanced stage and a higher recurrence rate. ZRF1-overexpressing tumors had a worse survival rate than those with non-expressing tumors (P < 0.01, log-rank test). ZRF1 positivity was independently associated with a worse outcome in the multivariate analysis (P < 0.01; hazard ratio 4.92; 95% confidence interval: 1.6-21.1). In ZRF1-overexpressing GC cells, knockdown of ZRF1 using specific siRNAs inhibited the cell proliferation, migration and invasion and induced apoptosis in a p53-dependent manner. These findings suggest that ZRF1 plays a crucial role in tumor malignant potential through its overexpression and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

Association Between hMLH1 Promoter Methylation and Risk of Gastric Cancer: A Meta-Analysis

Background: Human mutL homolog 1 (hMLH1) is located on chromosome 3q21-23. As a classic tumor suppressor gene, many researchers have studied the association between hMLH1 promoter methylation and gastric cancer, but their conclusions were not always consistent. Therefore, we performed a meta-analysis to make a more integrated and precise estimate of the associations.

Method: PubMed, EMBASE, and Cochrane Library were retrieved without language restrictions. Data were analyzed by Review Manager 5.2 and Stata 12.0 software. Odds ratio (OR) with 95% confidence interval (95%CI) was used to assess the statistical associations.

Result: A total of 39 studies published before January 20, 2018 were included in this study. The results indicated that the frequency of hMLH1 promoter methylation in gastric cancers was substantially higher than that in non-cancer controls (OR = 7.94, 95%CI = 4.32–14.58, P < 0.001). Furthermore, hMLH1 promoter methylation had considerable associations with lymph node metastasis, microsatellite instability (MSI), and low expression of hMLH1 protein (OR = 1.53, 95%CI = 1.04–2.26, P = 0.03; OR = 15.33, 95%CI = 9.26–25.36, P < 0.001; OR = 37.86, 95%CI = 18.03–79.50, P < 0.001, respectively). No association was found between hMLH1 promoter methylation and Lauren classification or Helicobacter pylori (HP) infection status.

Conclusion: The present study provides evidence that promoter methylation of hMLH1 is a major causative event in the occurrence and development of human gastric cancer.

Overexpression of denticleless E3 ubiquitin protein ligase homolog (DTL) is related to poor outcome in gastric carcinoma

BACKGROUND

Denticleless E3 ubiquitin protein ligase homolog (DTL) has been identified in amplified region (1q32) of several cancers and has an oncogenic function. In this study, we tested whether DTL acts as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC).

METHODS

We analyzed 7 GC cell lines and 100 primary tumors that were curatively resected in our hospital between 2001 and 2003.

RESULTS

Overexpression of the DTL protein was detected in GC cell lines (4/7 cell lines; 57%) and primary GC tumor samples (42/100 cases; 42%). Knockdown of DTL using several specific siRNAs inhibited the proliferation, migration and invasion in a TP53 mutation-independent manner. Overexpression of the DTL was significantly correlated with lymphatic invasion, deeper tumor depth and higher recurrence rate. Patients with DTL-overexpressing tumors had a worse survival rate than those with non-expressing tumors in overall survival (P = 0.0498, log-rank test) and disease-free survival (P = 0.0324, log-rank test). In a multivariate analysis, DTL positivity was independently associated with a worse overall survival (P = 0.0104, hazard ratio 3.7 [1.36-10.1]) and disease-free survival (P = 0.0070 (hazard ratio, 3.9 (1.45-10.46)) following radical gastrectomy.

CONCLUSIONS

These findings suggest that DTL overexpression plays a crucial role in tumor cell proliferation and highlights its usefulness as a prognosticator and potential therapeutic target in gastric cancer.

Overexpression of PBK/TOPK relates to tumour malignant potential and poor outcome of gastric carcinoma

Background:

PDZ-binding kinase/T-LAK cell-originated protein kinase (PBK/TOPK) is a serine–threonine kinase and overexpressed in various types of cancer by inhibiting the transactivation activities of p53 and PTEN. We tested whether PBK/TOPK acts as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC).

Methods:

We analysed five GC cell lines and 144 primary tumours, which were curatively resected in our hospital between 2001 and 2003.

Results:

Overexpression of the PBK/TOPK protein was frequently detected in GC cell lines (4 out of 5 lines, 80.0%) was detected in primary tumour samples of GC (24 out of 144 cases, 16.6%) and was significantly correlated with venous invasion, tumour depth and recurrence rate. PDZ-binding kinase/T-LAK cell-originated protein kinase-overexpressing tumours had a worse survival rate than those with non-expressing tumours (P=0.0009, log-rank test). PDZ-binding kinase/T-LAK cell-originated protein kinase positivity was independently associated with a worse outcome in multivariate analysis (P<0.0001, hazard ratio 6.40 (2.71–14.49)). In PBK/TOPK-overexpressing GC cells, knockdown of PBK/TOPK inhibited the cell proliferation through the p53 activation in a TP53 mutation-dependent manner and inhibited the migration/invasion through the PTEN upregulation in a TP53 mutation-independent manner.

Conclusions:

These findings suggest PBK/TOPK plays a crucial role in tumour malignant potential through its overexpression and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

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.

GFRA3 promoter methylation may be associated with decreased postoperative survival in gastric cancer

Background

A large number of epigenetic alterations has been found to be implicated in the etiology of gastric cancer. We have studied the DNA methylation status of 27 500 gene promoter regions in 24 gastric adenocarcinomas from a Norwegian cohort, and aimed at identifying the hypermethylated regions. We have compared our findings to the gene expression in the same tissue, and linked our results to prognosis and survival.

Methods

Biopsies from gastric adenocarcinomas and adjacent normal gastric mucosa were obtained from 24 patients following surgical resection of the tumor. Genome-wide DNA methylation profiling of the tumor and matched non-cancerous mucosa was performed. The results were compared to whole transcriptome cDNA microarray analysis of the same material.

Results

Most of the gene promoter regions in both types of tissue showed a low degree of methylation, however there was a small, but significant hypermethylation of the tumors. Hierarchical clustering showed separate grouping of the tumor and normal tissue. Hypermethylation of the promoter region of the GFRA3 gene showed a strong correlation to post-operative survival and several of the clinicopathological parameters, however no difference was found between the two main histological types of gastric cancer. There was only a modest correlation between the DNA methylation status and gene expression.

Conclusions

The different DNA methylation clusters of the tumors and normal tissue indicate that aberrant DNA methylation is a distinct feature of gastric cancer, although there is little difference in the overall, and low, methylation levels between the two tissue types. The GFRA3 promoter region showed marked hypermethylation in almost all tumors, and its correlation with survival and other clinicopathological parameters may have important prognostic significance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2247-8) contains supplementary material, which is available to authorized users.

Overexpression of SMYD2 contributes to malignant outcome in gastric cancer

BACKGROUND

SET and MYND domain-containing protein 2 (SMYD2) is a lysine methyltransferase for histone H3, p53 and Rb and inhibits their transactivation activities. In this study, we tested whether SMYD2 (1q42) acts as a cancer-promoting factor by being overexpressed in gastric cancer.

METHODS

We analysed 7 gastric cancer cell lines and 147 primary tumor samples of gastric cancer, which were curatively resected in our hospital.

RESULTS

SET and MYND domain-containing protein 2 was detected in these cell lines (five out of seven cell lines; 71.4%) and primary tumor samples (fifty-six out of one hundred and forty-seven cases; 38.1%). Knockdown of SMYD2 using specific small interfering RNA inhibited proliferation, migration and invasion of SMYD2-overexpressing cells in a TP53 mutation-independent manner. Overexpression of SMYD2 protein correlated with larger tumor size, more aggressive lymphatic invasion, deeper tumor invasion and higher rates of lymph node metastasis and recurrence. Patients with SMYD2-overexpressing tumours had a worse overall rate of survival than those with non-expressing tumours (P=0.0073, log-rank test) in an intensity and proportion score-dependent manner. Moreover, multivariate analysis demonstrated that SMYD2 was independently associated with worse outcome (P=0.0021, hazard ratio 4.25 (1.69-10.7)).

CONCLUSIONS

These findings suggest that SMYD2 has a crucial role in tumor cell proliferation by its overexpression and highlight its usefulness as a prognostic factor and potential therapeutic target in gastric cancer.

Overexpression of YWHAZ relates to tumor cell proliferation and malignant outcome of gastric carcinoma

BACKGROUND

Several studies have demonstrated that YWHAZ (14-3-3ζ), included in the 14-3-3 family of proteins, has been implicated in the initiation and progression of cancers. We tested whether YWHAZ acted as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC).

METHODS

We analysed 7 GC cell lines and 141 primary tumours, which were curatively resected in our hospital between 2001 and 2003.

RESULTS

Overexpression of the YWHAZ protein was frequently detected in GC cell lines (six out of seven lines, 85.7%) and primary tumour samples of GC (72 out of 141 cases, 51%), and significantly correlated with larger tumour size, venous and lymphatic invasion, deeper tumour depth, and higher pathological stage and recurrence rate. Patients with YWHAZ-overexpressing tumours had worse overall survival rates than those with non-expressing tumours in both intensity and proportion expression-dependent manner. YWHAZ positivity was independently associated with a worse outcome in multivariate analysis (P=0.0491, hazard ratio 2.3 (1.003-5.304)). Knockdown of YWHAZ expression using several specific siRNAs inhibited the proliferation, migration, and invasion of YWHAZ-overexpressing GC cells. Higher expression of the YWHAZ protein was significantly associated with the lower expression of miR-375 in primary GC tissues (P=0.0047).

CONCLUSION

These findings suggest that YWHAZ has a pivotal role in tumour cell proliferation through its overexpression, and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

Frequent GNAS and KRAS mutations in pyloric gland adenoma of the stomach and duodenum

Gastric and duodenal adenomas exhibit a significant morphological and phenotypical diversity and are classified into intestinal-type, foveolar-type and pyloric gland adenomas. We analysed the mutations in GNAS, KRAS, BRAF and CTNNB1 and the expressions of mismatch repair (MMR) proteins in 80 gastric and 32 duodenal adenomas with histologically distinct subtypes, as well as in 71 gastric adenocarcinomas. Activating GNAS mutations were found in 22 of the 35 pyloric gland adenomas (PGAs; 63%) but in none of the foveolar-type or intestinal-type adenomas or the adenocarcinomas. Fourteen PGAs (41%), two foveolar-type adenomas (9%), five intestinal-type adenomas (9%) and one adenocarcinoma (1%) had KRAS mutations. BRAF mutations were absent in all the adenomas and adenocarcinomas that were examined. CTNNB1 mutations were only found in two intestinal-type adenomas (4%). Notably, 13 of the 14 KRAS-mutated gastric and duodenal PGAs had concurrent GNAS mutations. The loss of the MMR proteins, which is indicative of microsatellite instability, was observed in one PGA (3%), 12 foveolar-type adenomas (52%), one intestinal-type adenoma (2%) and five adenocarcinomas (7%). These observations indicate that each histological subtype of gastric and duodenal adenomas has a distinct genetic background. In particular, the present study identified the frequent presence of activating GNAS mutations, which are often associated with KRAS mutations, as a characteristic genetic feature of PGAs of the stomach and duodenum.

Comprehensive DNA methylation and extensive mutation analyses reveal an association between the CpG island methylator phenotype and oncogenic mutations in gastric cancers

Recent development of personal sequencers for extensive mutation analysis and bead array technology for comprehensive DNA methylation analysis have made it possible to obtain integrated pictures of genetic and epigenetic alterations on the same set of cancer samples. Here, we aimed to establish such pictures of gastric cancers (GCs). Comprehensive methylation analysis of 30 GCs revealed that the number of aberrantly methylated genes was highly variable among individual GCs. Extensive mutation analysis of 55 known cancer-related genes revealed that 19 of the 30 GCs had 24 somatic mutations of eight different genes (CDH1, CTNNB1, ERBB2, KRAS, MLH1, PIK3CA, SMARCB1, and TP53). Integration of information on the genetic and epigenetic alterations revealed that the GCs with the CpG island methylator phenotype (CIMP) tended to have mutations of oncogenes, CTNNB1, ERBB2, KRAS, and PIK3CA. This is one of the first studies in which both genetic and epigenetic alterations were extensively analyzed in the same set of samples. It was also demonstrated for the first time in GCs that the CIMP was associated with oncogene mutations.

Overexpression of TRIM44 contributes to malignant outcome in gastric carcinoma

Recent studies have shown that some members of the tripartite motif-containing protein (TRIM) family, which is characterized by a conserved RING finger, B-box, and coiled-coil domains, function as important regulators for carcinogenesis. In this study, we tested whether TRIM44 (11p13) acts as a cancer-promoting gene through overexpression in gastric cancer. We analyzed seven gastric cancer cell lines and 112 primary tumors, which were curatively resected in our hospital between 2001 and 2003. Expression of the TRIM44 protein was detected in gastric cancer cell lines (2/7 cell lines; 29%) and primary tumor samples of gastric cancer (29/112 cases; 25%). Knockdown of TRIM44 expression using several specific siRNAs inhibited the proliferation, migration, and invasion of TRIM44-overexpressing cells. Overexpression of the TRIM44 protein was significantly correlated with an advanced type of macroscopic appearance, lymphatic invasion, and higher recurrence rate. TRIM44-overexpressing tumors had a worse overall rate of survival than those with non-expressing tumors (P = 0.0038, log-rank test) in both intensity and proportion expression-dependent manner. TRIM44 positivity was independently associated with worse outcome in multivariate analysis (P = 0.0233, hazard ratio 3.37 [1.18-9.64]). These findings suggest that TRIM44 plays a crucial role in tumor cell proliferation through its overexpression, and highlight its usefulness as a predictor and potential therapeutic target in gastric cancer.

The association between MLH1 -93 G>A polymorphism of DNA mismatch repair and cancer susceptibility: a meta-analysis

DNA mismatch repair, known as a fundamentally biological pathway, plays key roles in maintaining genomic stability, eliminating mismatch bases and preventing both mutagenesis in the short term and cancerogenesis in the long term. Polymorphisms of MLH1 in individuals may have an effect on the DNA repair capacity and therefore on cancer risk. Recently, emerging studies have been done to evaluate the association between MLH1 -93 G/A polymorphism and cancer risk in diverse populations. However, the results remain conflicting rather than conclusive. In this meta-analysis, we assessed reported studies of association between the MLH1 -93 G/A polymorphism and cancer risk including 13 691 cancer cases and 14 068 controls from 17 published studies. A borderline significant association between the MLH1 -93 G/A polymorphism and cancer risk was observed in overall analysis [heterozygote: odds ratio (OR) = 1.15; 95% confidence interval (CI) 1.05-1.26; homozygote: OR = 1.21; 95% CI, 1.04-1.40; dominant model: OR = 1.13; 95% CI 1.01-1.26; recessive model: OR = 1.21; 95% CI 1.07-1.35, respectively]. In subgroup analysis by ethnicity, significantly increased risks were found in Asian population and mixed population but not in Caucasian population. After stratified analysis according to the quality of literature, increased cancer risks were observed in the studies of lower quality but not in the studies of higher quality. Similarly, elevated cancer risks were observed in hospital-based studies but not in population-based studies. These findings showed no persuasive evidence that MLH1 -93 G/A polymorphism was associated with an increased risk of cancer. On the conservative standpoint, well-designed population-based studies with larger sample size in different ethnic groups should be performed to further confirm these results.

Comparative features of colorectal and gastric cancers with microsatellite instability in Chinese patients

OBJECTIVE

The purpose of this study was to determine the unique and universal features of microsatellite instability-high (MSI-H) colorectal cancer (CRC) and MSI-H gastric cancer (GC) in the Chinese population.

METHODS

A new panel of mononucleotide MSI markers, BAT25, BAT26, NR21, NR24, and MONO-27, was used to define MSI status in 303 CRC and 288 GC subjects. Clinicopathological features of both types of MSI-H tumors were analyzed. Methylation analysis in the hMLH1 promoter region by methylation specific polymerase chain reaction (PCR) and mutation detection of hMSH2/hMLH1 genes by denaturing high-performance liquid chromatography (DHPLC) were carried out simultaneously.

RESULTS

MSI-H CRCs and MSI-H GCs account for 11.9% and 8.0% of unselected sporadic CRCs and GCs, respectively. MSI-H CRCs are strongly characterized by early onset, right-side location, low differentiation, mucinous tumor, less infiltration, less lymphatic metastasis, and more often familial tumor. MSI-H GCs only showed site preference for the antrum and less lymphatic metastasis. Genetic and epigenetic analyses were positive in 6/36 MSI-H CRCs and 0/23 MSI-H GCs with pathological mutation in major mismatch repair genes, and in 7/36 MSI-H CRCs and 18/23 MSI-H GCs with methylated hMLH1 promoter (P<0.01), respectively.

CONCLUSIONS

Although there are many differences in the genetic basis and clinicopathological features between MSI-H CRC and MSI-H GC, when compared with their microsatellite stable (MSS) counterparts, site preference and lymphatic metastasis are features common to both types of MSI-H tumors.

Claudin-1 has tumor suppressive activity and is a direct target of RUNX3 in gastric epithelial cells

BACKGROUND & AIMS

The transcription factor RUNX3 is a gastric tumor suppressor. Tumorigenic Runx3(-/-) gastric epithelial cells attach weakly to each other, compared with nontumorigenic Runx3(+/+) cells. We aimed to identify RUNX3 target genes that promote cell-cell contact to improve our understanding of RUNX3's role in suppressing gastric carcinogenesis.

METHODS

We compared gene expression profiles of Runx3(+/+) and Runx3(-/-) cells and observed down-regulation of genes associated with cell-cell adhesion in Runx3(-/-) cells. Reporter, mobility shift, and chromatin immunoprecipitation assays were used to examine the regulation of these genes by RUNX3. Tumorigenesis assays and immunohistological analyses of human gastric tumors were performed to confirm the role of the candidate genes in gastric tumor development.

RESULTS

Mobility shift and chromatin immunoprecipitation assays revealed that the promoter activity of the gene that encodes the tight junction protein claudin-1 was up-regulated via the binding of RUNX3 to the RUNX consensus sites. The tumorigenicity of gastric epithelial cells from Runx3(-/-) mice was significantly reduced by restoration of claudin-1 expression, whereas knockdown of claudin-1 increased the tumorigenicity of human gastric cancer cells. Concomitant expression of RUNX3 and claudin-1 was observed in human normal gastric epithelium and cancers.

CONCLUSIONS

The tight junction protein claudin-1 has gastric tumor suppressive activity and is a direct transcriptional target of RUNX3. Claudin-1 is down-regulated during the epithelial-mesenchymal transition; RUNX3 might therefore act as a tumor suppressor to antagonize the epithelial-mesenchymal transition.

Clinicopathologic characteristics and outcomes of gastric cancers with the MSI-H phenotype

OBJECTIVES

We examined the correlation between microsatellite instability (MSI) status and the clinicopathological features and prognostic value in gastric cancer and compared the efficacy of immunohistochemical staining for hMLH1 and hMSH2 with a polymerase chain reaction (PCR)-based test.

METHODS

MSI status was examined in 328 consecutive gastric adenocarcinomas using tissue preserved in paraffin blocks. DNA extracted from tumor sections and the corresponding normal tissue was analyzed using PCR at the five microsatellite loci recommended by the National Cancer Institute (NCI). Immunohistochemical staining for hMLH1 and hMSH2 was performed and the results were compared with the MSI status measured using PCR. The relationship of the clinicopathologic variables to MSI status was analyzed.

RESULTS

Of the gastric cancers, 8.2% (n = 27) contained MSI-H and this was associated with older age (>70 years), distal tumor location, tumor size, and intestinal subtype. Lymphatic and vascular invasion were associated with the disease-free survival. On immunohistochemical staining, the loss of expression of hMLH1 or hMSH2 was observed in 11% (n = 36). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of immunohistochemical staining were 63.0%, 93.7%, 47.2%, 96.6%, and 91.2%, respectively.

CONCLUSIONS

Gastric cancers with MSI-H have specific clinicopathologic characteristics, such as older age at diagnosis, distal tumor location, increased tumor size, and intestinal histologic type. However, immunohistochemical staining for hMLH1 and hMSH2 is not as accurate as the PCR-based MSI test.

Epigenetic DNA hypermethylation in cholangiocarcinoma: potential roles in pathogenesis, diagnosis and identification of treatment targets

Cholangiocarcinomas (CCs) are highly lethal malignant tumours arising from the biliary tract epithelium. The disease is notoriously difficult to diagnose and is usually fatal because of its typically late clinical presentation and the lack of effective non-surgical therapeutic modalities. The overall survival rate, including resected patients is poor, with less than 5% of patients surviving 5 years, a rate which has not changed significantly over the past 30 years. Although CC is a relatively uncommon tumor, interest in this disease is rising as incidence and mortality rates for intrahepatic cholangiocarcinoma are increasing markedly worldwide. A variety of risk factors, including primary sclerosing cholangitis, liver fluke infestation, and hepatolithiasis have been described. However, for most CCs the cause is unknown, and affected individuals have no history of exposure to, or association with, known risk factors. Recent advances in molecular pathogenesis have highlighted the importance of epigenetic alterations in the form of promoter region hypermethylation and histone deacetylation in addition to genetic changes in the process of cholangiocarcinogenesis. This review provides a comprehensive overview of the genes reported to be methylated in CC to date and their putative roles in cholangiocarcinogenesis. Future directions in the study of methylated genes and their potential roles as diagnostic and prognostic markers are also discussed.

Stage IV early gastric cancer: two cases with microsatellite instability

BACKGROUND

We experienced two rare cases of stage IV early gastric carcinoma with extensive lymph node metastasis (pT1N3) and microsatellite instability caused by methylation of the MLH1 gene.

MATERIALS AND METHODS

The clinicopathological features of patients with stage IV EGC were examined. Microsatellite instability (MSI) was analyzed using five microsatellite markers and MLH1 gene promoter methylation patterns were determined by methylation specific polymerase chain reaction (PCR) from paraffin-embedded tissue samples. Loss of hMLH1 was identified by immunohistochemical study.

RESULTS

In both cases, the carcinomas were located in the antrum of the stomach, confined within the submucosa (SM3) and accompanied by endolymphatic tumor emboli. Immunohistochemical analysis for hMLH1 showed negative nuclear staining in the carcinoma cells. The tumor demonstrated methylation of the MLH1 gene and MSI-H because they manifested instability in three and two of the five markers tested. One patient is alive without any clinical, radiological, or pathological evidence of recurrence or metastasis at 37 months, while the other patient died after a cerebrovascular accident 5 months after surgery.

CONCLUSION

Our rare cases support that MSI caused by MLH1 promoter methylation and the loss of hMLH1 protein play an important role in stage IV EGC development.

Delta mtDNA4977 is more common in non-tumoral cells from gastric cancer sample

BACKGROUND

The aim of this study was to determine the frequency of delta mtDNA4977 in tumoral cells as compared with adjacent normal cells in gastric cancer.

METHODS

In order to investigate whether a high incidence of mutation exists in mitochondrial DNA of gastric cancer tissues, we screened one of common region of the mitochondrial genome by PCR amplification and Southern blot followed by DNA sequence analysis. DNA isolated from these cells was used to amplify hypervariable regions ATPase8/6, COXIII, ND3, ND4 and ND5 of delta mtDNA4977.

RESULTS

In 107 cancer patients, delta mtDNA4977 was detected in 6 cases (5.60%) of the tumoral tissues and 18 cases (16.82%) of the non-tumoral tissues that were adjacent to the tumors. Levels of delta mtDNA4977 deletions were found to be more in non-tumoral tissues than in adjacent tumoral tissues. There was no correlation of patients with certain clinical parameters like age, sex, tumor location and tumor size; however, there was an obvious relationship with intestinal-type of gastric cancer.

CONCLUSIONS

Unknown genetic aspects, ambiguous environmental factors and reactive oxygen species (ROS) can cause the delta mtDNA4977 mutation rate to be increased in gastric cancer. The results suggest that percentage level of delta mtDNA4977 is less common and intolerable in tumoral tissue, probably because of high metabolism and ROS generation. We supposed that the cells initially had delta mtDNA4977 transform to tumoral cells and the existed deletion conferred metabolic disadvantage; thus, cells containing such a mtDNA deletion would be overgrown by other cancer cells without this mtDNA deletion. As a result, the presence of delta mtDNA4977 will be low in tumoral cells.

Tumoral Cell mtDNA ∼8.9 kb Deletion Is More Common than Other Deletions in Gastric Cancer

BACKGROUND

The aim of the study was to clarify the role of deletion of mitochondrial DNA (mtDNA) in gastric carcinogenesis and to determine prevalence of mitochondrial deletions in different regions of tumoral tissue in comparison with adjacent non-tumoral tissue in gastric cancer.

METHODS

In order to investigate whether a high incidence of mutations exists in mtDNA of gastric cancer tissues, we screened five regions of the mitochondrial genome by PCR amplification, Southern blot and DNA sequence analysis.

RESULTS

Of 71 cancer patients, the approximately 8.9 kb deletion was detected among different deletions in 9 cases (12.67%) of the tumoral tissues and 1 case (1.40%) in non-tumoral tissues that were adjacent to the tumors. Level of the 8.9 kb deletion has been found to be more than other deletions in tumoral tissues.

CONCLUSIONS

The approximately 8.9 kb deletion has an obvious correlation with age and histological type. These data suggest that the approximately 8.9 kb deletion in mtDNA may play an important role in gastric carcinogenesis.

Microsatellite instability and methylation of the DNA mismatch repair genes in head and neck cancer

BACKGROUND

Methylation in the promoter region of the DNA mismatch repair genes hMLH1 and hMSH2 and microsatellite instability at three loci were analyzed in the tumor tissue from patients with head and neck cancer.

METHODS

Microsatellite instability and promoter methylation were investigated by PCR, denaturing-polyacrylamide gel electrophoresis and digestion with methylation-specific restriction enzymes.

RESULTS

Microsatellite instability was observed in 41% of the patients. hMLH1 and hMSH2 genes were methylated in 47% and 30% of the patients, respectively. BAT25 and BAT26 instability were associated with age and histopathology, respectively. Methylation frequency of the hMLH1 gene promoter was significantly higher in patients displaying a high level of microsatellite instability. Instability at the BAT 26 and D2S123 loci were associated with the MSI-high status.

CONCLUSIONS

Our results indicate that microsatellite instability and modifications in the hMLH1 and hMSH2 genes are implicated in a significant proportion of the patients with head and neck cancer.

Tumor microsatellite instability in early onset gastric cancer

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 (or=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.

Microsatellite instability and gastric non-invasive neoplasia in a high risk population in Cesena, Italy

BACKGROUND/AIMS

In the natural history of gastric cancer, non-invasive neoplasia (NiN) precedes invasive carcinoma. A histological classification of gastric NiN has recently been proposed by a World Health Organisation international panel of experts. Genetic instability is known to be among the molecular pathways involved in gastric oncogenesis. In this retrospective cross sectional study, microsatellite instability (MSI) was analysed in a consecutive series of NiN and NiN related histological alterations from a northern Italian region at high risk for gastric cancer.

PATIENTS/METHODS

Fifty five consecutive cases (indefinite for NiN, 29 cases; low grade NiN, 17 cases; high grade NiN, nine cases) were analysed by radioactive polymerase chain reaction and electrophoresis for microsatellite alterations at six loci (BAT25, BAT26, D2S123, D5S346, D17S250, and D3S1317). MSI was defined according to the Bethesda criteria distinguishing: (1) no instability in the analysed loci; (2) low frequency MSI (MSI-L); and (3) high frequency MSI (MSI-H). Immunohistochemical expression of MLH1 and MSH2 proteins was also analysed in all cases.

RESULTS

Overall, MSI was found in 11 of 55 cases (indefinite for NiN, five of 29 (MSI-L, four; MSI-H, one); low grade NiN, three of 17 (MSI-L, one; MSI-H, two); high grade NiN, three of nine (MSI-L, one; MSI-H, two).

CONCLUSIONS

In an Italian high risk area for gastric cancer, MSI is part of the spectrum of genetic alterations in gastric non-invasive neoplasia. In European populations at high risk of gastric cancer, DNA repair system alterations are thought to be among the early molecular events in gastric carcinogenesis.

Gene deregulation in gastric cancer

Despite its decreasing frequency in the Western world during recent decades, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Due to the oligosymptomatic course of early gastric cancer, most cases are diagnosed in the advanced stages of the disease. The curative potential of current standard treatment continues to be unsatisfactory, despite multimodal approaches involving surgery, chemotherapy and radiotherapy. Novel therapeutics including small molecules and monoclonal antibodies are being developed and have been partially introduced into clinical use in connection with neoplastic diseases such as chronic myeloid leukemia, non-Hodgkin's lymphoma and colorectal cancer. Thorough understanding of the changes in gene expression occurring during gastric carcinogenesis may help to develop targeted therapies and improve the treatment of this disease. Novel molecular biology techniques have generated a wealth of data on up- and down-regulation, activation and inhibition of specific pathways in gastric cancer. Here, we provide an overview of the different aspects of aberrant gene expression patterns in gastric cancer.

Promoter hypermethylation is a major event of hMLH1 gene inactivation in liver fluke related cholangiocarcinoma

Cholangiocarcinoma is a crucial health problem in Northeast Thailand where liver fluke infection is endemic. However, molecular genetic and epigenetic mechanisms involved in carcinogenesis of this cancer remain unclear. We attempted to study genetic and epigenetic alterations of hMLH1 gene in 65 intrahepatic cholangiocarcinoma using polymerase chain reaction (PCR) based microsatellite marker D3S1611 and methylation-specific PCR, respectively. Of 65 cases, 29 (44.6%) showed hypermethylation of hMLH1 promoter. Loss of heterozygosity (LOH) of hMLH1 was detected in 12 of 51 informative cases (23.5%). Five out of 29 (17.2%) methylated cases demonstrated LOH. Aberrant methylation of hMLH1 promoter was significantly associated with poorly differentiated type (P=0.013). Our study suggests that both genetic and epigenetic mechanisms cause the inactivation of hMLH1 where epigenetic is a major event resulting in mismatch repair deficiency and contributing to carcinogenesis of liver fluke related cholangiocarcinoma. Since, gene silencing by methylation is an early event in carcinogenesis, promoter hypermethylation of hMLH1 may be a molecular targeted therapy and prevention of liver fluke related cholangiocarcinoma.

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Frequent epigenetic inactivation of RIZ1 by promoter hypermethylation in human gastric carcinoma

The retinoblastoma protein-interacting zinc finger gene, RIZ1 (GenBank accession number U17838), is involved in chromatin-mediated gene expression and is also a target for frameshift mutation in microsatellite-unstable cancers. Methylation of the RIZ1 promoter CpG island has been shown to be a common mechanism in inactivating the RIZ1 gene in human liver and breast cancers. We investigated levels of RIZ1 mRNA in 45 gastric carcinoma tissues by quantitative RT-PCR and in gastric carcinoma cell lines by RT-PCR. In addition, we examined CpG island methylator phenotype (CIMP) status, p53 mutation status, and the correlation between promoter methylation status and RIZ1 mRNA expression. CIMP status was investigated by examining the methylation status of MINT1, MINT2, MINT12, MINT25 and MINT31. p53 mutation status was examined by PCR-single strand conformation polymorphism and promoter methylation status was examined by methylation-specific PCR. Promoter hypermethylation of the RIZ1 gene was found in 31 (69%) of 45 gastric carcinoma tissues and in 3 (21%) of 14 corresponding non-neoplastic mucosae, the incidence being significantly different (p = 0.002). None of the 12 normal gastric tissues from young non-cancer individuals showed hypermethylation. Promoter hypermethylation was associated with reduced RIZ1 expression in gastric carcinoma tissues (p = 0.029). Promoter hypermethylation of the RIZ1 gene was significantly associated with CIMP (p = 0.002). Mutation status of the p53 gene was not associated with methylation status or RIZ1 expression in gastric carcinoma. In gastric carcinoma cell lines MKN-28 and KATO-III, the RIZ1 promoter was hypermethylated and RIZ1 transcription was inactive. Treatment of these cells with demethylating agent 5-aza-2'-deoxycytidine restored RIZ1 transcription. Our results suggest that transcriptional inactivation of the RIZ1 gene by promoter hypermethylation may participate in stomach carcinogenesis.

Mutation of mismatch repair gene hMLH3 in familial gastric cancer

AIM: To detect the mutations of mismatch repair gene hMLH3 and to investigate its possible role in familial gastric cancer.

METHODS: A total of 84 members from 16 suggestive hereditary gastric cancer families were investigated with PCR, denaturing high-performance liquid chromatography (DHPLC) and direct sequencing. The diagnostic criteria for familial gastric cancer are as follows: (1) at least two successive generations, (2) at least two patients with gastric cancer, (3) one of them should be first-degree relative of the other, and (4) at least one patient was diagnosed before 50 years old.

RESULTS: Five missence mutations were identified in five gastric cancer families, four mutations within exon 1 and one mutation within exon 12. Carcinogenesis was obviously associated with hMLH3 mutations in family 6, but not in other families. No mutations were found in sporadic gastric cancer and normal controls.

CONCLUSION: hMLH3 probably acts as a low risk gene in familial gastric cancer. The mutations of hMLH3 may work together with other genes and result in an elevated risk of gastric cancer in the family.

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Alterations of mtDNA copy number in gastric carcinoma

AIM: To explore the relationship between mitochondrial DNA (mtDNA) and gastric cancer by comparing the difference of mtDNA copy number in gastric cancers and paracancerous tissues.

METHODS: Hypervariable reigon (HV)₁ and HV₂ of mitochondrial D-loop region from 20 cases of gastric cancer and 20 paracancerous tissues were amplified by PCR; meantime b-actin was served as a quantitative standard marker, followed by polyacrylamide gel electrophoresis (PAGE) and silver staining, in which the difference of mtDNA copy number was compared between gastric cancers and paracancerous tissues.

RESULTS: There existed significantly quantitative difference in HV₁, HV₂ (standardized with b-actin) between gastric cancers and paracancerous tissues (P < 0.01). mtDNA copy number was associated with important enzymes in nucleus such as AKP, cAMP-PDE and cGMP-PDE (P < 0.05), although not with tumor histological type and invasive depth (P > 0.05).

CONCLUSION: The occurrence of gastric cancer is closely associated with decreased mtDNA copy number, which may be a new tumor marker.

Differentially expressed proteins of gamma-ray irradiated mouse intestinal epithelial cells by two-dimensional electrophoresis and MALDI-TOF mass spectrometry

AIM: To identify the differentially expressed proteins involved in ionizing radiation in mice and to explore new ways for studying radiation-related proteins.

METHODS: Bal B/c mice grouped as sham-irradiation, 3 h and 72 h irradiation were exposed to 9.0Gy single dose of γ-irradiation. Intestinal epithelia were isolated from mice, and total proteins were extracted with urea containing solution. A series of methods were used, including two-dimensional electrophoresis, PDQuest 2-DE software analysis, peptide mass fingerprinting based on matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) and SWISS-PROT database searching, to separate and identify the differential proteins. Western blotting and RT-PCR were used to validate the differentially expressed proteins.

RESULTS: Mouse intestine was severely damaged by 9.0 Gy γ-irradiation. Image analysis of two-dimensional gels revealed that averages of 638 ± 39, 566 ± 32 and 591 ± 29 protein spots were detected in 3 groups, respectively, and the majority of these protein spots were matched. About 360 protein spots were matched between normal group and 3 h irradiation group, and the correlation coefficient was 0.78 by correlation analysis of gels. Also 312 protein spots matched between normal group and 72 h irradiation group, and 282 protein spots between 3 h and 72 h irradiation groups. Twenty-eight differential protein spots were isolated from gels, digested with trypsin, and measured with MALDI-TOF-MS. A total of 25 spots yielded good spectra, and 19 spots matched known proteins after database searching. These proteins were mainly involved in anti-oxidation, metabolism, signal transduction, and protein post-translational processes. Western-blotting confirmed that enolase was up-regulated by γ-irradiation. Up-regulation of peroxiredoxin I was verified by applying RT-PCR technique, but no change occurred in Q8VC72.

CONCLUSION: These differentially expressed proteins might play important roles when mouse intestine was severely injured by γ-irradiation. It is suggested that differential proteomic analysis may be a useful tool to study the proteins involved in radiation damage of mouse intestinal epithelia.