SMAD7 rs12953717 polymorphism contributes to increased risk of colorectal cancer

Drosophila MOV10 regulates the termination of midgut regeneration

The molecular mechanisms by which stem cell proliferation is precisely controlled during the course of regeneration are poorly understood. Namely, how a damaged tissue senses when to terminate the regeneration process, inactivates stem cell mitotic activity, and organizes ECM integrity remain fundamental unanswered questions. The Drosophila midgut intestinal stem cell (ISC) offers an excellent model system to study the molecular basis for stem cell inactivation. Here, we show that a novel gene, CG6967 or dMOV10, is induced at the termination stage of midgut regeneration, and shows an inhibitory effect on ISC proliferation. dMOV10 encodes a putative component of the microRNA (miRNA) gene silencing complex (miRISC). Our data, along with previous studies on the mammalian MOV10, suggest that dMOV10 is not a core member of miRISC, but modulates miRISC activity as an additional component. Further analyses identified direct target mRNAs of dMOV10-containing miRISC, including Daughter against Dpp (Dad), a known inhibitor of BMP/TGF-β signaling. We show that RNAi knockdown of Dad significantly impaired ISC division during regeneration. We also identified six miRNAs that are induced at the termination stage and their potential target transcripts. One of these miRNAs, mir-1, is required for proper termination of ISC division at the end of regeneration. We propose that miRNA-mediated gene regulation contributes to the precise control of Drosophila midgut regeneration.

Evaluating the predictive value of genetic risk score in colorectal cancer among Chinese Han population

Increasing single nucleotide polymorphisms (SNPs) have been identified to be associated with colorectal cancer (CRC). We aimed to investigate whether genetic risk scores (GRS) that aggregate information from multiple genetic variants can predict the risk of CRC in a Chinese population. Fifty candidate SNPs were selected to explore the associations with CRC in a discovery sample with 1002 CRC cases and 999 healthy controls. We modeled the significant SNPs identified by the case-control study as a multilocus weighted GRS and estimated the association of GRS with CRC. Furthermore, 300 pairs of cases and controls were included as a validation sample to confirm the finding. Area under the receiver operating characteristic curve (AUROC) was used to evaluate the predictive power of GRS in CRC. A total of seven SNPs were found to increase the risk of CRC, and two SNPs were found to be negatively associated with CRC in the discovery sample. Relative to participants with the lowest quartile of GRS, those with the highest quartile had a 2.64-fold (95% CI: 1.99-3.51) higher risk for CRC. For every 0.1 point of GRS increase, the risk of CRC increase by 11% (95% CI: 8-14%). AUROC for GRS alone were 0.59 (95% CI: 0.57-0.62) and 0.52 (95% CI: 0.46-0.58) in the discovery and validation sample, respectively. AUROC increased to 0.62 (95% CI: 0.59-0.64) and 0.71 (95% CI: 0.65-0.76) by combining environmental risk factors. Our findings support an association between GRS and risk of CRC, which provides evidence of improved prediction model for CRC in China.

Angiotensin-Converting Enzyme Gene Deletion Polymorphism is Associated with Lymph Node Metastasis in Colorectal Cancer Patients in a Chinese Population

Background

The purpose of this study was to assess the effect of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism on the risk of lymph node metastasis (LNM) in colorectal cancer (CRC) patients.

Material/Methods

We enrolled 146 CRC patients and 106 healthy controls in this study. ACE gene I/D polymorphism was genotyped by polymerase chain reaction (PCR). Hardy-Weinberg equilibrium (HWE) was used to assess the goodness of fit of the genotypes. χ² test was used to calculate the differences of genotype and allele distributions. Odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) were used to analyze the association between ACE I/D polymorphism and LNM in CRC patients.

Results

Insertion/deletion (ID) and deletion/deletion (DD) genotypes were frequently observed in CRC patients, but only DD genotype and D allele were related to the susceptibility of CRC (P=0.038, OR=2.158, 95%CI=1.039–4.480; P=0.026, OR=1.501, 95%CI=1.048–2.150). DD genotype and D allele also increased the risk of LNM in CRC patients (P=0.028, OR=2.844, 95%CI=1.107–7.038; P=0.026, OR=1.692, 95%CI=1.063–2.693).

Conclusions

DD genotype and D allele of ACE gene I/D polymorphism might increase the risk of LNM in CRC patients.

Correlation Between CASC8, SMAD7 Polymorphisms and the Susceptibility to Colorectal Cancer: An Updated Meta-Analysis Based on GWAS Results

Genome-wide association studies (GWASs) and a number of case-control studies have suggested that several single nucleotide polymorphisms (SNPs), rs7837328, rs7014346, rs6983267, rs10505477 on CASC8 gene and rs4939827, rs4464148, rs12953717 on SMAD7 gene are significantly correlated with the susceptibility to colorectal cancer (CRC). For the sake of clarifying the association, a meta-analysis was conducted and population heterogeneity was considered in the study.A total of 34 articles including 90 studies (168,471 cases and 163,223 controls) that evaluated the relationship between the CASC8, SMAD7 genes and the risk of CRC under the allelic model were reviewed. Also subgroup analysis was performed by ethnicity (Caucasian, Asian, and African) and all of the analyses were implemented in R 3.2.1 software.Pooled data from the meta-analysis revealed that the A allele of rs7837328, the A allele of rs7014346, the G allele of rs6983267, the A allele of rs10505477, the T allele of rs4939827, the T of rs4464148, and the T of rs12953717 were significantly associated with an increased risk of CRC under the allelic model. Additionally, subgroup analyses of 6 SNPs by ethnicity (rs4464148 excepted) witnessed that the A allele of rs7837328, the G allele of rs6983267, and the T of rs12953717 were notably associated with an increased risk of CRC among Caucasian and Asian. Furthermore, the A allele of rs7014346, the A allele of rs10505477, and the T allele of rs4939827 were significantly related with an elevated risk of CRC only among Caucasian.Our study suggested that for CASC8 gene, SNP of rs7837328 and rs6983267 are risk factors for CRC among both Caucasian and Asian whereas rs7014346 and rs10505477 are risky gene polymorphisms only among Caucasian. For SMAD7 gene, rs4939827 and rs4464148 are risk factors for CRC among Caucasian whereas rs12953717 could elevate the susceptibility to CRC in both Caucasian and Asian.

IL-27 rs153109 polymorphism increases the risk of colorectal cancer in Chinese Han population

IL-27, a new member of the IL-12 family, has been found to have antitumor effects in colorectal cancer (CRC); therefore, polymorphisms of this protein may modulate CRC carcinogenesis. So, we studied the association of single nucleotide polymorphisms of the IL-27 gene with the risk of CRC occurrence using a case–control using 600 CRC patients and matched healthy controls. The IL-27 rs153109 polymorphism was analyzed with polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing methods. Data indicate that GG, GA, and combined A-variant genotypes (GG + GA) conferred significantly greater risk of CRC (P=0.034, 0.002, and 0.001, respectively), and that G alleles were associated with higher susceptibility to CRC (P=0.001). However, no correlation was found between the IL-27 rs153109 polymorphism and particular clinical features. In conclusion, our data demonstrated a clear association of IL-27 rs153109 polymorphism and the risk of CRC development.

Esophageal cancer in a family with hamartomatous tumors and germline PTEN frameshift and SMAD7 missense mutations

Germline mutations in the PTEN tumor-suppressor gene cause autosomal-dominant conditions such as Cowden and Bannayan-Riley-Ruvalcaba syndromes with variable presentations, including hamartomatous gastrointestinal tumors, dermatologic abnormalities, neurologic symptoms, and elevated cancer risk. We describe a father and son with extensive hamartomatous gastrointestinal polyposis who both developed early-onset esophageal cancer. Exome sequencing identified a novel germline PTEN frameshift mutation (c.568_569insC, p.V191Sfs*11). In addition, a missense mutation of SMAD7 (c.115G>A, p.G39R) with an allele frequency of 0.3% in the Exome Variant Server was detected in both affected individuals. Fluorescence in situ hybridization for PTEN in the resected esophageal cancer specimen demonstrated no PTEN copy loss in malignant cells; however, results of an immunohistochemical analysis demonstrated a loss of PTEN protein expression. While the risks of many cancers are elevated in the PTEN hamartoma tumor syndromes, association between esophageal adenocarcinoma and these syndromes has not been previously reported. Esophageal adenocarcinoma and extensive polyposis/ganglioneuromatosis could represent less common features of these syndromes, potentially correlating with this novel PTEN frameshift and early protein termination genotype. Alternatively, because simultaneous disruption of both the PTEN and TGF-β/SMAD4 pathways is associated with development of esophageal cancer in a mouse model and because SMAD4 mutations cause gastrointestinal hamartomas in juvenile polyposis syndrome, the SMAD7 mutation may represent an additional modifier of these individuals' PTEN-mutant phenotype.

Functional annotation of colon cancer risk SNPs

Colorectal cancer (CRC) is a leading cause of cancer-related deaths in the United States. Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with increased risk for CRC. A molecular understanding of the functional consequences of this genetic variation has been complicated because each GWAS SNP is a surrogate for hundreds of other SNPs, most of which are located in non-coding regions. Here we use genomic and epigenomic information to test the hypothesis that the GWAS SNPs and/or correlated SNPs are in elements that regulate gene expression, and identify 23 promoters and 28 enhancers. Using gene expression data from normal and tumour cells, we identify 66 putative target genes of the risk-associated enhancers (10 of which were also identified by promoter SNPs). Employing CRISPR nucleases, we delete one risk-associated enhancer and identify genes showing altered expression. We suggest that similar studies be performed to characterize all CRC risk-associated enhancers.

Previous studies identified genetic variants associated with colorectal cancer (CRC), but the functional consequences of these genetic risk factors remain poorly understood. Here, the authors report that CRC risk variants reside in promoters and enhancers and could increase colon cancer risk through gene expression regulation.