Tineke E. Buffart

Lack of microRNA-101 causes E-cadherin functional deregulation through EZH2 up-regulation in intestinal gastric cancer

E‐cadherin expression disruption is commonly observed in metastatic epithelial cancers and is a crucial step in gastric cancer (GC) initiation and progression. As aberrant expression of microRNAs often perturb the normal expression/function of pivotal cancer‐related genes, we characterized and dissected a pathway that causes E‐cadherin dysfunction via loss of microRNA‐101 and up‐regulation of EZH2 expression in GC. MicroRNA microarray expression profiling and array‐CGH were used to reinforce miR‐101 involvement in GC. By using quantitative real‐time PCR and quantitative SNaPshot genomic PCR, we confirmed that miR‐101 was significantly down‐regulated in GC (p < 0.0089) in comparison with normal gastric mucosas and, at least in 65% of the GC cases analysed, this down‐regulation was caused by deletions and/or microdeletions at miR‐101 genomic loci. Moreover, around 40% of cases showing miR‐101 down‐regulation displayed concomitant EZH2 over‐expression (at the RNA and protein levels), which, in turn, was associated with loss/aberrant expression of E‐cadherin. Interestingly, this occurred preferentially in intestinal‐type GCs, retaining allele(s) untargeted by classical CDH1‐inactivating mechanisms. We also demonstrated that miR‐101 gain of function or direct inhibition of EZH2 in Kato III GC cells led to a strong depletion of endogenous EZH2 and consequent rescue of E‐cadherin membranous localization, mimicking results obtained in clinical GC samples. In conclusion, we show that deletions and/or microdeletions at both miR‐101 genomic loci cause mature miR‐101 down‐regulation, subsequent EZH2 over‐expression and E‐cadherin dysfunction, specifically in intestinal‐type GC. Copyright

Gastric cancers in young and elderly patients show different genomic profiles.

Although most gastric cancers occur in elderly patients, a substantial number of cases of this common disease occur in young patients. Gastric cancer is a heterogeneous disease at the genomic level and different patterns of DNA copy number alterations are associated with different clinical behaviour. The aim of the present study was to explore differences in DNA copy number alterations in relation to age of onset of gastric cancer. DNA isolated from 46 paraffin‐embedded gastric cancer tissue samples from 17 patients less than 50 years of age [median 43 (21–49) years] and 29 patients greater than or equal to 70 years of age [median 75 (70–83) years] was analysed by genome‐wide microarray comparative genomic hybridization (array CGH) using an array of 5000 BAC clones. Patterns of DNA copy number aberrations were analysed by hierarchical cluster analysis of the mode‐normalized and smoothed log2 ratios of tumour to normal reference fluorescence signal intensities using TMEV software, after which cluster membership was correlated with age group. In addition, supervised analysis was performed using CGH Multi‐array. Hierarchical cluster analysis of the array CGH data revealed three clusters with different genomic profiles that correlated significantly with age (p = 0.006). Cluster 1 mainly contained young patients, while elderly patients were divided over clusters 2 and 3. Chromosome regions 11q23.3 and 19p13.3 contributed most to age‐related differences in tumour profiles. Gastric cancers of young and old patients belong to groups with different genomic profiles, which likely reflect different pathogenic mechanisms of the disease. Copyright

Across array comparative genomic hybridization: a strategy to reduce reference channel hybridizations.

Array comparative genomic hybridization (array CGH) is widely used for studying chromosomal copy number aberrations (CNAs) on a genome‐wide and high‐resolution scale in heritable disorders and cancers. The aim of this study was to test if the separate channels of dual channel arrays can be interchanged (across array) to either make array CGH more sensitive and cost effective and/or to generate profiles of CNAs and copy number variations (CNVs). Therefore the BT474 breast cancer cell line was compared with a mix of normal reference DNAs hybridized on different arrays and days and DNA copy number profiles were evaluated. Quality was assessed, using regular dual channel array CGH as a standard, using four quality measures, i.e., the median absolute deviation value of chromosome 2, the amplitude of the ERBB2 gene amplification, a deletion on chromosome 9, and the deflection on chromosome 8. The quality of the across array CGH profiles matched or even surpassed the quality of regular dual channel array CGH. In addition, this across array approach was tested for genomic DNA derived from formalin‐fixed paraffin‐embedded tumors tissue samples, resulting in high‐quality copy number profiles, comparable to regular dual channel arrays. Finally, we demonstrated this approach to obtain both CNA and CNV profiles. In summary, across array CGH avoids redundant hybridizations of the same reference material in every experiment either allowing hybridization of two test samples on one array or producing both CNA and CNV profiles simultaneously.

High resolution analysis of DNA copy-number aberrations of chromosomes 8, 13, and 20 in gastric cancers

DNA copy-number gains of chromosomes 8q, 13q, and 20q are frequently observed in gastric cancers. Moreover gain of chromosome 20q has been associated with lymph node metastasis. The aim of this study was to correlate DNA copy-number changes of individual genes on chromosomes 8q, 13q, and 20q in gastric adenocarcinomas to clinicopathological data. DNA isolated from 63 formalin-fixed and paraffin-embedded gastric adenocarcinoma tissue samples was analyzed by whole-genome microarray comparative genomic hybridization and by multiplex ligation-dependent probe amplification (MLPA), targeting 58 individual genes on chromosomes 8, 13, and 20. Using array comparative genomic hybridization, gains on 8q, 13q, and 20q were observed in 49 (77.8%), 25 (39.7%), and 49 (77.8%) gastric adenocarcinomas, respectively. Gain of chromosome 20q was significantly correlated with lymph node metastases (pu2009=u20090.05) and histological type (pu2009=u20090.02). MLPA revealed several genes to be frequently gained in DNA copy number. The oncogene c-myc on 8q was gained in 73% of the cancers, while FOXO1A and ATP7B on 13q were both gained in 28.6% of the cases. Multiple genes on chromosome 20q showed gains in more than 60% of the cancers. DNA copy-number gains of TNFRSF6B (20q13.3) and ZNF217 (20q13.2) were significantly associated with lymph node metastasis (pu2009=u20090.02) and histological type (pu2009=u20090.02), respectively. In summary, gains of chromosomes 8q, 13q, and 20q in gastric adenocarcinomas harbor DNA copy-number gains of known and putative oncogenes. ZNF217 and TNFRSF6B are associated with important clinicopathological variables, including lymph node status.

KRAS and BRAF mutations are rare and related to DNA mismatch repair deficiency in gastric cancer from the East and the West: results from a large international multicentre study.

Background:Inhibitors of the epidermal growth factor (EGFR) signaling pathway have a major role in the treatment of KRAS wild-type colorectal cancer patients. The EGFR pathway has been shown to be activated in gastric cancer (GC). However, published data on KRAS and BRAF mutation status is limited in GC and has not been compared between GC from different geographic regions.Methods:The prevalence of KRAS and BRAF mutations was established in 712 GC: 278 GC from the United Kingdom, 230 GC from Japan and 204 GC from Singapore. The relationship between KRAS/BRAF mutation status, DNA mismatch repair (MMR) status, clinicopathological variables and overall survival was analysed.Results:Overall, 30 (4.2%) GC carried a KRAS mutation. In total, 5.8% of the UK GC, 4% of Japan GC and 1.5% of Singapore GC were KRAS mutant. KRAS mutant GC had fewer lymph node metastases in the UK cohort (P=0.005) and were more frequent in elderly patients in the Japan cohort (P=0.034). KRAS mutations were more frequent in MMR-deficient GC in the UK and the Japanese cohort (P<0.05). A BRAF mutation was only detected in a single Japanese GC.Conclusions:This large multicentre study demonstrated that KRAS mutations and DNA MMR deficiency have a role in a small subgroup of GC irrespective of country of origin, suggesting that this subgroup of GC may have developed along a common pathway. Further studies need to establish whether concomitant mutations or amplifications of other EGFR signalling pathway genes may contribute to the activation of this pathway in GC.

High-Resolution Array Comparative Genomic Hybridization in Sporadic and Celiac Disease–Related Small Bowel Adenocarcinomas

Purpose: The molecular pathogenesis of small intestinal adenocarcinomas is not well understood. Understanding the molecular characteristics of small bowel adenocarcinoma may lead to more effective patient treatment. Experimental Design: Forty-eight small bowel adenocarcinomas (33 non–celiac disease related and 15 celiac disease related) were characterized for chromosomal aberrations by high-resolution array comparative hybridization, microsatellite instability, and APC promoter methylation and mutation status. Findings were compared with clinicopathologic and survival data. Furthermore, molecular alterations were compared between celiac disease–related and non–celiac disease–related small bowel adenocarcinomas. Results: DNA copy number changes were observed in 77% small bowel adenocarcinomas. The most frequent DNA copy number changes found were gains on 5p15.33-5p12, 7p22.3-7q11.21, 7q21.2-7q21.3, 7q22.1-7q34, 7q36.1, 7q36.3, 8q11.21-8q24.3, 9q34.11-9q34.3, 13q11-13q34, 16p13.3, 16p11.2, 19q13.2, and 20p13-20q13.33, and losses on 4p13-4q35.2, 5q15-5q21.1, and 21p11.2-21q22.11. Seven highly amplified regions were identified on 6p21.1, 7q21.1, 8p23.1, 11p13, 16p11.2, 17q12-q21.1, and 19q13.2. Celiac disease–related and non–celiac disease–related small bowel adenocarcinomas displayed similar chromosomal aberrations. Promoter hypermethylation of the APC gene was found in 48% non–celiac disease–related and 73% celiac disease–related small bowel adenocarcinomas. No nonsense mutations were found. Thirty-three percent of non–celiac disease–related small bowel adenocarcinomas showed microsatellite instability, whereas 67% of celiac disease–related small bowel adenocarcinomas were microsatellite unstable. Conclusions: Our study characterized chromosomal aberrations and amplifications involved in small bowel adenocarcinoma. At the chromosomal level, celiac disease–related and non–celiac disease–related small bowel adenocarcinomas did not differ. A defect in the mismatch repair pathways seems to be more common in celiac disease–related than in non–celiac disease–related small bowel adenocarcinomas. In contrast to colon and gastric cancers, no APC nonsense mutations were found in small bowel adenocarcinoma. However, APC promoter methylation seems to be a common event in celiac disease–related small bowel adenocarcinoma. Clin Cancer Res; 16(5); 1391–401

MAL promoter hypermethylation as a novel prognostic marker in gastric cancer

T-lymphocyte maturation associated protein, MAL, has been described as a tumour-suppressor gene with diagnostic value in colorectal and oesophageal cancers, and can be inactivated by promoter hypermethylation. The aim of this study was to analyse the prevalence of MAL promoter hypermethylation and the association with mRNA expression in gastric cancers and to correlate methylation status to clinicopathological data. Bisulphite-treated DNA isolated from formalin-fixed and paraffin-embedded samples of 202 gastric adenocarcinomas and 22 normal gastric mucosae was subjected to real-time methylation-specific PCR (Q-MSP). Two regions within the MAL promoter (M1 and M2) were analysed. In addition, 17 frozen gastric carcinomas and two gastric cancer cell lines were analysed both by Q-MSP and real-time RT–PCR. Methylation of M1 and M2 occurred in 71 and 80% of the gastric cancers, respectively, but not in normal gastric mucosa tissue. Hypermethylation of M2, but not M1, correlated with significantly better disease-free survival in a univariate (P=0.03) and multivariate analysis (P=0.03) and with downregulation of expression (P=0.01). These results indicate that MAL has a putative tumour-suppressor gene function in gastric cancer, and detection of promoter hypermethylation may be useful as a prognostic marker.

Deletion of chromosome 4q predicts outcome in Stage II colon cancer patients

BackgroundAround 30% of all stage II colon cancer patients will relapse and die of their disease. At present no objective parameters to identify high-risk stage II colon cancer patients, who will benefit from adjuvant chemotherapy, have been established. With traditional histopathological features definition of high-risk stage II colon cancer patients is inaccurate. Therefore more objective and robust markers for prediction of relapse are needed. DNA copy number aberrations have proven to be robust prognostic markers, but have not yet been investigated for this specific group of patients. The aim of the present study was to identify chromosomal aberrations that can predict relapse of tumor in patients with stage II colon cancer.Materials and methodsDNA was isolated from 40 formaldehyde fixed paraffin embedded stage II colon cancer samples with extensive clinicopathological data. Samples were hybridized using Comparative Genomic Hybridization (CGH) arrays to determine DNA copy number changes and microsatellite stability was determined by PCR. To analyze differences between stage II colon cancer patients with and without relapse of tumor a Wilcoxon rank-sum test was implemented with multiple testing correction.ResultsStage II colon cancers of patients who had relapse of disease showed significantly more losses on chromosomes 4, 5, 15q, 17q and 18q. In the microsatellite stable (MSS) subgroup (nu2009=u200928), only loss of chromosome 4q22.1-4q35.2 was significantly associated with disease relapse (Pu2009<u20090.05, FDRu2009<u20090.15). No differences in clinicopathological characteristics between patients with and without relapse were observed.ConclusionIn the present series of MSS stage II colon cancer patients losses on 4q22.1-4q35.2 were associated with worse outcome and these genomic alterations may aid in selecting patients for adjuvant therapy.

DNA copy number profiles of gastric cancer precursor lesions

BackgroundChromosomal instability (CIN) is the most prevalent type of genomic instability in gastric tumours, but its role in malignant transformation of the gastric mucosa is still obscure. In the present study, we set out to study whether two morphologically distinct categories of gastric cancer precursor lesions, i.e. intestinal-type and pyloric gland adenomas, would carry different patterns of DNA copy number changes, possibly reflecting distinct genetic pathways of gastric carcinogenesis in these two adenoma types.ResultsUsing a 5K BAC array CGH platform, we showed that the most common aberrations shared by the 11 intestinal-type and 10 pyloric gland adenomas were gains of chromosomes 9 (29%), 11q (29%) and 20 (33%), and losses of chromosomes 13q (48%), 6(48%), 5(43%) and 10 (33%). The most frequent aberrations in intestinal-type gastric adenoma were gains on 11q, 9q and 8, and losses on chromosomes 5q, 6, 10 and 13, whereas in pyloric gland gastric adenomas these were gains on chromosome 20 and losses on 5q and 6. However, no significant differences were observed between the two adenoma types.ConclusionThe results suggest that gains on chromosomes 8, 9q, 11q and 20, and losses on chromosomes 5q, 6, 10 and 13, likely represent early events in gastric carcinogenesis. The phenotypical entities, intestinal-type and pyloric gland adenomas, however, do not differ significantly (P = 0.8) at the level of DNA copy number changes.

Gastric cancers of Western European and African patients show different patterns of genomic instability

BackgroundInfection with H. pylori is important in the etiology of gastric cancer. Gastric cancer is infrequent in Africa, despite high frequencies of H. pylori infection, referred to as the African enigma. Variation in environmental and host factors influencing gastric cancer risk between different populations have been reported but little is known about the biological differences between gastric cancers from different geographic locations. We aim to study genomic instability patterns of gastric cancers obtained from patients from United Kingdom (UK) and South Africa (SA), in an attempt to support the African enigma hypothesis at the biological level.MethodsDNA was isolated from 67 gastric adenocarcinomas, 33 UK patients, 9 Caucasian SA patients and 25 native SA patients. Microsatellite instability and chromosomal instability were analyzed by PCR and microarray comparative genomic hybridization, respectively. Data was analyzed by supervised univariate and multivariate analyses as well as unsupervised hierarchical cluster analysis.ResultsTumors from Caucasian and native SA patients showed significantly more microsatellite instable tumors (p < 0.05). For the microsatellite stable tumors, geographical origin of the patients correlated with cluster membership, derived from unsupervised hierarchical cluster analysis (p = 0.001). Several chromosomal alterations showed significantly different frequencies in tumors from UK patients and native SA patients, but not between UK and Caucasian SA patients and between native and Caucasian SA patients.ConclusionsGastric cancers from SA and UK patients show differences in genetic instability patterns, indicating possible different biological mechanisms in patients from different geographical origin. This is of future clinical relevance for stratification of gastric cancer therapy.