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Differential genetic influences over colorectal cancer risk and gene expression in large bowel mucosa

ABSTRACT: Site-specific variation in colorectal cancer (CRC) incidence, biology and prognosis are poorly understood. We sought to determine whether common genetic variants influencing CRC risk might exhibit topographical differences on CRC risk through regional differences in effects on gene expression in the large bowel mucosa. We conducted a site-specific genetic association study (10,630 cases, 31,331 controls) to identify whether established risk variants exert differential effects on risk of proximal, compared to distal CRC. We collected normal colorectal mucosa and blood from 481 subjects and assessed mucosal gene expression using Illumina HumanHT-12v4 arrays in relation to germline genotype. Expression quantitative trait loci (eQTLs) were explored by anatomical location of sampling. Normal colorectal mucosa was analyzed from both CRC patients and healthy controls.

ORGANISM(S): Homo sapiens

PROVIDER: GSE161023 | GEO | 2021/04/29

REPOSITORIES: GEO

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Project description:Colorectal cancer (CRC) is a genetically heterogeneous disease with several distinct morphological growth patterns. This study was aimed to investigate genes differentially expressed between ulcerative and polypoid colorectal CRC. cDNA microarray was first employed to compare the gene expression profiling of ulcerative and polypoid CRC with paired normal mucosa. Potential candidates identified by data filtering were further validated using quantitative real-time polymerase chain reaction, western blot and immunohistochemistry. Epigenetic regulation of gene expression was investigated using methylation-specific PCR (MSP). cDNA microarray identified 11 up-regulated and 14 down-regulated genes differentially expressed in both types of tumor compared to matched normal mucosa. Among them, S100P was the only upregulated gene preferentially associated with polypoid CRC (p = 0.032), whereas no genes demonstrated significantly differential association with ulcerative CRC. S100P protein and mRNA expression level of polypoid CRC was significantly higher than that of ulcerative CRC (p < 0.05, respectively). Immunoreactivity of S100P protein was localized predominantly in the nuclei and to a less extent in the cytoplasm. Overexpression of S100P occurred early in the adenoma stage. 80% (24/30) and 20% (6/30) polypoid CRC showed diffusely strong and moderate overexpression, respectively. In contrast, S100P was diffusely and strongly expressed in 15% (6/40) ulcerative CRC, with 52.5% (21/40) and 32.5% (13/40) tumors having moderate and weak overexpression, respectively. S100P overexpression was preferentially associated with polypoid CRC (p < 0.001). The relative methylation level determined by MSP was not statistically different between polypoid and ulcerative CRC (43.36% vs. 49.10%, p = 0.168), indicating that promoter hypomethylation was directly related to upregulation of S100P mRNA. The gene expression profiling of ulcerative and polypoid CRC with paired normal mucosa were compared. Dye swapping experiments with ulcerative CRC vs normal mucosa or polypoid CRC vs normal mucosa were performed and we averaged the log ratios of the duplicated spots on each slide.

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Differential genetic influences over colorectal cancer risk and gene expression in large bowel mucosa

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