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SNPs associated with colorectal cancer at 15q13.3 affect risk enhancers that modulate GREM1 gene expression.

ABSTRACT: Several genome wide association studies of colorectal cancer (CRC) have identified single nucleotide polymorphisms (SNPs) on chromosome 15q13.3 associated with CRC risk. To identify functional variant(s) underlying this association, we investigated SNPs in linkage disequilibrium with the risk-associated SNP rs4779584 that overlapped regulatory regions/enhancer elements characterized in colon-related tissues and cells. We identified several SNP-containing regulatory regions that exhibited enhancer activity in vitro, including one SNP (rs1406389) that correlated with allele-specific effects on enhancer activity. Deletion of either this enhancer or another enhancer that had previously been reported in this region correlated with decreased expression of GREM1 following CRISPR/Cas9 genome editing. That GREM1 is one target of these enhancers was further supported by an expression quantitative trait loci correlation between rs1406389 and GREM1 expression in the transverse but not sigmoid colon in the Genotype-Tissue Expression dataset. Taken together, we conclude that the 15q13.3 region contains at least two functional variants that map to distinct enhancers and impact CRC risk through modulation of GREM1 expression.

SUBMITTER: Fortini BK

PROVIDER: S-EPMC7898835 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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SNPs associated with colorectal cancer at 15q13.3 affect risk enhancers that modulate GREM1 gene expression.

Fortini Barbara K BK Tring Stephanie S Devall Matthew A MA Ali Mourad Wagdy MW Plummer Sarah J SJ Casey Graham G

Human mutation 20210202 3

Several genome wide association studies of colorectal cancer (CRC) have identified single nucleotide polymorphisms (SNPs) on chromosome 15q13.3 associated with CRC risk. To identify functional variant(s) underlying this association, we investigated SNPs in linkage disequilibrium with the risk-associated SNP rs4779584 that overlapped regulatory regions/enhancer elements characterized in colon-related tissues and cells. We identified several SNP-containing regulatory regions that exhibited enhance ...[more]

PMID: 33476087

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Project description:Background It is widely accepted that inflammatory cytokine, interleukin 6 (IL-6), was not only elevated in cancer but also important in carcinogenesis. But how did IL-6 be produced in tumor microenvironment remains to be addressed. Methods Both bioinformatics tools and quantitative real time polymerase chain reaction (RT-PCR) were used to examine the expression of IL-6 in cancer cells. To map super-enhancers of IL-6, sgRNAs were constructed. Stable knockout cells were established and subsequently used for cell proliferation and colony formation assay. The correlation between mapped super-enhancers and IL-6 expression was studied by ATAC-seq analysis. Results The expression of IL-6 was high in multiple cancers, including pancreatic cancer (PAAD). The elevated expression of IL-6 in PAAD was further confirmed by transcriptional data and in a panel of pancreatic cancer cell lines (one immortal HPDE6-C7 cell line and four PDAC cell lines: BxPC-3, PANC-1, AsPC-1 and CFPAC-1). When treated with JQ-1 and I-BET-762, two inhibitors of super-enhancers, the expression of IL-6 in multiple cancer cells including CFPAC-1, HeLa and SUM-159 cells was significantly reduced. By analyzing the H3K27Ac profiling, BRD4 binding, Med1 binding and DNA conservation in CFPAC-1, HeLa and SUM-159 cells, we identified a potential super-enhancer (IL6-SE) that might be important for IL-6 expression in cancer. The super-enhancer (IL6-SE) can be further divided into two elements (IL6-SEa and IL6-SEb). Genetic deletion of IL6-SEa in cancer cells greatly reduces the expression of IL-6. IL6-SEa deficient cells also showed low proliferation and colony formation ability. In patients, the epigenetic activation (ATAC signal) of IL6-SEa is correlated with the expression of IL-6. Conclusions In summary, we not only provide convincing experimental evidence to demonstrate that IL-6 expression in cancer is dependent on super-enhancers but also identified IL6-SEa as a critical DNA regulatory element. Our findings provide new insights to understand the epigenetic regulation of IL-6 expression in cancers.

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SNPs associated with colorectal cancer at 15q13.3 affect risk enhancers that modulate GREM1 gene expression.

Publications

SNPs associated with colorectal cancer at 15q13.3 affect risk enhancers that modulate GREM1 gene expression.

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