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Genotype-environment interactions in microsatellite stable/microsatellite instability-low colorectal cancer: results from a genome-wide association study.

ABSTRACT: Genome-wide association studies (GWAS) have led to the identification of a number of common susceptibility loci for colorectal cancer (CRC); however, none of these GWAS have considered gene-environment (G × E) interactions. Therefore, it is unclear whether current hits are modified by environmental exposures or whether there are additional hits whose effects are dependent on environmental exposures.We conducted a systematic search for G × E interactions using genome wide data from the Colon Cancer Family Registry that included 1,191 cases of microsatellite stable (MSS) or microsatellite instability-low (MSI-L) CRC and 999 controls genotyped using either the Illumina Human1M or Human1M-Duo BeadChip. We tested for interactions between genotypes and 14 environmental factors using 3 methods: a traditional case-control test, a case-only test, and the recently proposed 2-step method by Murcray and colleagues. All potentially significant findings were replicated in the ARCTIC Study.No G × E interactions were identified that reached genome-wide significance by any of the 3 methods. When analyzing previously reported susceptibility loci, 7 significant G × E interactions were found at a 5% significance level. We investigated these 7 interactions in an independent sample and none of the interactions were replicated.Identifying G × E interactions will present challenges in a GWAS setting. Our power calculations illustrate the need for larger sample sizes; however, as CRC is a heterogeneous disease, a tradeoff between increasing sample size and heterogeneity needs to be considered.The results from this first genome-wide analysis of G × E in CRC identify several challenges, which may be addressed by large consortium efforts.

SUBMITTER: Figueiredo JC

PROVIDER: S-EPMC3089660 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Genotype-environment interactions in microsatellite stable/microsatellite instability-low colorectal cancer: results from a genome-wide association study.

Figueiredo Jane C JC Lewinger Juan Pablo JP Song Chi C Campbell Peter T PT Conti David V DV Edlund Christopher K CK Duggan Dave J DJ Rangrej Jagadish J Lemire Mathieu M Hudson Thomas T Zanke Brent B Cotterchio Michelle M Gallinger Steven S Jenkins Mark M Hopper John J Haile Robert R Newcomb Polly P Potter John J Baron John A JA Le Marchand Loic L Casey Graham G

Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 20110225 5

<h4>Background</h4>Genome-wide association studies (GWAS) have led to the identification of a number of common susceptibility loci for colorectal cancer (CRC); however, none of these GWAS have considered gene-environment (G × E) interactions. Therefore, it is unclear whether current hits are modified by environmental exposures or whether there are additional hits whose effects are dependent on environmental exposures.<h4>Methods</h4>We conducted a systematic search for G × E interactions using g ...[more]

PMID: 21357381

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Project description:BackgroundMicrosatellite instability-high (MSI-H) is a form of genomic instability present in 15% of colorectal cancer (CRC) cases. Several differential gene analyses have been conducted on CRC; however, none have specifically explored the differentially expressed genes in MSI-H CRC. Research on the different gene expressions between MSI-H CRC and microsatellite stable (MSS) CRC, and their different patterns of metastasis will provide invaluable insights for diagnosis, prognosis, and treatment.MethodsIn this study, the differential expression of 46,602 genes were analyzed across 613 different tissue samples from The Cancer Genome Atlas (TCGA)-colon adenocarcinoma (COAD) and TCGA-rectum adenocarcinoma (READ) as part of a gene association analysis. R package TCGAbiolinks (version 2.18.0) was used to download the data set, and DESeq2 (version 1.30.1) was used for the differential gene analysis. The resulting genes were then analyzed for shared pathways with R package clusterProfiler (version 3.0.4).ResultsA total of 237 significantly differentially expressed genes (Padj<0.05) were found between MSI-H and MSS CRC. Differentially expressed genes include insulin like growth factor 2 (IGF2) and fibroblast growth factor 3 (FGF3), and the enriched pathways mostly involve hearing, digestive regulation, and neurogenesis.463 differentially expressed genes were found between metastatic and non-metastatic CRC. Notably differentially expressed genes in metastatic CRC include DEAD-box helicase 53 (DDX53) and adiponectin, C1Q and collagen domain containing (ADIPOQ), and enriched pathways include the immune system, cell adhesion, and cell signaling. For MSI-H CRC, a total of 34 genes were significantly differently expressed between metastatic and non-metastatic CRC. These include notum, palmitoleoyl-protein carboxylesterase (NOTUM), serpin family B member 2 (SERPINB2), and several keratin (KRT) genes, and the pathway analysis showed the major enrichment of the hormonal and secretion and regulation pathways. Of the differentially expressed genes in metastatic CRC, 25 were immunity related and include fatty acid binding protein 4 (FABP4), and the pathway analysis showed the enrichment of humoral immunity and lymphocyte regulation.ConclusionsOf the biologically plausible differentially expressed genes, the most notable were NOTUM, KRT6A, KRT14, SERPINB2, and serum amyloid A1 (SAA1). NOTUM, KRT6A, and KRT14 are active in the Wnt pathway. All five are also involved in various inflammation pathways.

Project description:The BRAF (V600E) mutation in colorectal cancers that are microsatellite stable (MSS) confers a poor patient prognosis, whereas BRAF mutant microsatellite-unstable (MSI) colorectal cancers have an excellent prognosis. BRAF wild type cancers are typically MSS and display chromosomal instability (CIN). CIN has not been extensively studied on a genome-wide basis in relation to BRAF mutational status in colorectal cancer. BRAF mutant/MSS (BRAFmut/MSS) cancers (n = 33) and BRAF mutant/MSI (BRAFmut/MSI) cancers (n = 30) were compared for presence of copy number aberrations (CNAs) indicative of CIN, with BRAF wild type/MSS (BRAFwt/MSS) cancers (n = 18) using Illumina CytoSNP-12 arrays. BRAFmut/MSS and BRAFwt/MSS cancers showed comparable numbers of CNAs/cancer at 32.8 and 29.8 respectively. However, there were differences in patterns of CNA length between MSS cohorts, with BRAFmut/MSS cancers having significantly greater proportions of focal CNAs compared to BRAFwt/MSS cancers (p<0.0001); whereas whole chromosomal arm CNAs were more common in BRAFwt/MSS cancers (p<0.0001). This related to a reduced average CNA length in BRAFmut/MSS compared to BRAFwt/MSS cancers (20.7 Mb vs 33.4 Mb;p<0.0001); and a smaller average percent of CIN affected genomes in BRAFmut/MSS compared to BRAFwt/MSS cancers (23.9% vs 34.9% respectively). BRAFmut/MSI cancers were confirmed to have low CNA rates (5.4/cancer) and minimal CIN-affected genomes (average of 4.5%) compared to MSS cohorts (p<0.0001). BRAFmut/MSS cancers had more frequent deletion CNAs compared to BRAFwt/MSS cancers on 6p and 17q at loci not typically correlated with colorectal cancer, and greater amplification CNAs on 8q and 18q compared to BRAFwt/MSS cancers. These results indicate that comparable rates of CIN occur between MSS subgroups, however significant differences in their patterns of instability exist, with BRAFmut/MSS cancers showing a 'focal pattern' and BRAFwt/MSS cancers having a 'whole arm pattern' of CIN. This and the genomic loci more frequently affected in BRAFmut/MSS cancers provides further evidence of the biological distinctions of this important cancer subgroup.

Dataset Information

Genotype-environment interactions in microsatellite stable/microsatellite instability-low colorectal cancer: results from a genome-wide association study.

Publications

Genotype-environment interactions in microsatellite stable/microsatellite instability-low colorectal cancer: results from a genome-wide association study.

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