Most cited article - PubMed ID 33632709
Genetic architectures of proximal and distal colorectal cancer are partly distinct
BACKGROUND: Recent research has identified a potential protective effect of higher numbers of circulating lymphocytes on colorectal cancer (CRC) development. However, the importance of different lymphocyte subtypes and activation states in CRC development and the biological pathways driving this relationship remain poorly understood and warrant further investigation. Specifically, CD4+ T cells - a highly dynamic lymphocyte subtype - undergo remodelling upon activation to induce the expression of genes critical for their effector function. Previous studies investigating their role in CRC risk have used bulk tissue, limiting our current understanding of the role of these cells to static, non-dynamic relationships only. METHODS: Here, we combined two genetic epidemiological methods - Mendelian randomisation (MR) and genetic colocalisation - to evaluate evidence for causal relationships of gene expression on CRC risk across multiple CD4+ T cell subtypes and activation stage. Genetic proxies were obtained from single-cell transcriptomic data, allowing us to investigate the causal effect of expression of 1,805 genes across five CD4+ T cell activation states on CRC risk (78,473 cases; 107,143 controls). We repeated analyses stratified by CRC anatomical subsites and sex, and performed a sensitivity analysis to evaluate whether the observed effect estimates were likely to be CD4+ T cell-specific. RESULTS: We identified six genes with evidence (FDR-P<0.05 in MR analyses and H4>0.8 in genetic colocalisation analyses) for a causal role of CD4+ T cell expression in CRC development - FADS2, FHL3, HLA-DRB1, HLA-DRB5, RPL28, and TMEM258. We observed differences in causal estimates of gene expression on CRC risk across different CD4+ T cell subtypes and activation timepoints, as well as CRC anatomical subsites and sex. However, our sensitivity analysis revealed that the genetic proxies used to instrument gene expression in CD4+ T cells also act as eQTLs in other tissues, highlighting the challenges of using genetic proxies to instrument tissue-specific expression changes. CONCLUSIONS: Our study demonstrates the importance of capturing the dynamic nature of CD4+ T cells in understanding disease risk, and prioritises genes for further investigation in cancer prevention research.
- Publication type
- Journal Article MeSH
- Preprint MeSH
Alternative polyadenylation (APA) modulates mRNA processing in the 3'-untranslated regions (3' UTR), affecting mRNA stability and translation efficiency. Research into genetically regulated APA has the potential to provide insights into cancer risk. In this study, we conducted large APA-wide association studies to investigate associations between APA levels and cancer risk. Genetic models were built to predict APA levels in multiple tissues using genotype and RNA sequencing data from 1,337 samples from the Genotype-Tissue Expression project. Associations of genetically predicted APA levels with cancer risk were assessed by applying the prediction models to data from large genome-wide association studies of six common cancers among European ancestry populations: breast, ovarian, prostate, colorectal, lung, and pancreatic cancers. A total of 58 risk genes (corresponding to 76 APA sites) were associated with at least one type of cancer, including 25 genes previously not linked to cancer susceptibility. Of the identified risk APAs, 97.4% and 26.3% were supported by 3'-UTR APA quantitative trait loci and colocalization analyses, respectively. Luciferase reporter assays for four selected putative regulatory 3'-UTR variants demonstrated that the risk alleles of 3'-UTR variants, rs324015 (STAT6), rs2280503 (DIP2B), rs1128450 (FBXO38), and rs145220637 (LDHA), significantly increased the posttranscriptional activities of their target genes compared with reference alleles. Furthermore, knockdown of the target genes confirmed their ability to promote proliferation and migration. Overall, this study provides insights into the role of APA in the genetic susceptibility to common cancers. Significance: Systematic evaluation of associations of alternative polyadenylation with cancer risk reveals 58 putative susceptibility genes, highlighting the contribution of genetically regulated alternative polyadenylation of 3'UTRs to genetic susceptibility to cancer.
- MeSH
- 3' Untranslated Regions * genetics MeSH
- Genome-Wide Association Study * MeSH
- Genetic Predisposition to Disease * MeSH
- Polymorphism, Single Nucleotide MeSH
- Humans MeSH
- Quantitative Trait Loci MeSH
- RNA, Messenger genetics metabolism MeSH
- Cell Line, Tumor MeSH
- Neoplasms * genetics MeSH
- Polyadenylation * MeSH
- Gene Expression Regulation, Neoplastic MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- 3' Untranslated Regions * MeSH
- RNA, Messenger MeSH
BACKGROUND: Transcriptome-wide association studies have been successful in identifying candidate susceptibility genes for colorectal cancer (CRC). To strengthen susceptibility gene discovery, we conducted a large transcriptome-wide association study and an alternative splicing transcriptome-wide association study in CRC using improved genetic prediction models and performed in-depth functional investigations. METHODS: We analyzed RNA-sequencing data from normal colon tissues and genotype data from 423 European descendants to build genetic prediction models of gene expression and alternative splicing and evaluated model performance using independent RNA-sequencing data from normal colon tissues of the Genotype-Tissue Expression Project. We applied the verified models to genome-wide association studies (GWAS) summary statistics among 58 131 CRC cases and 67 347 controls of European ancestry to evaluate associations of genetically predicted gene expression and alternative splicing with CRC risk. We performed in vitro functional assays for 3 selected genes in multiple CRC cell lines. RESULTS: We identified 57 putative CRC susceptibility genes, which included the 48 genes from transcriptome-wide association studies and 15 genes from splicing transcriptome-wide association studies, at a Bonferroni-corrected P value less than .05. Of these, 16 genes were not previously implicated in CRC susceptibility, including a gene PDE7B (6q23.3) at locus previously not reported by CRC GWAS. Gene knockdown experiments confirmed the oncogenic roles for 2 unreported genes, TRPS1 and METRNL, and a recently reported gene, C14orf166. CONCLUSION: This study discovered new putative susceptibility genes of CRC and provided novel insights into the biological mechanisms underlying CRC development.
- MeSH
- Genome-Wide Association Study MeSH
- Genetic Predisposition to Disease MeSH
- Polymorphism, Single Nucleotide MeSH
- Colorectal Neoplasms * genetics MeSH
- Humans MeSH
- Repressor Proteins genetics MeSH
- RNA MeSH
- Transcriptome * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, N.I.H., Extramural MeSH
- Names of Substances
- Repressor Proteins MeSH
- RNA MeSH
- TRPS1 protein, human MeSH Browser
Telomeric sequences, the structures comprised of hexanucleotide repeats and associated proteins, play a pivotal role in chromosome end protection and preservation of genomic stability. Herein we address telomere length (TL) dynamics in primary colorectal cancer (CRC) tumour tissues and corresponding liver metastases. TL was measured by multiplex monochrome real-time qPCR in paired samples of primary tumours and liver metastases along with non-cancerous reference tissues obtained from 51 patients diagnosed with metastatic CRC. Telomere shortening was observed in the majority of primary tumour tissues compared to non-cancerous mucosa (84.1%, p < 0.0001). Tumours located within the proximal colon had shorter TL than those in the rectum (p < 0.05). TL in liver metastases was not significantly different from that in primary tumours (p = 0.41). TL in metastatic tissue was shorter in the patients diagnosed with metachronous liver metastases than in those diagnosed with synchronous liver metastases (p = 0.03). The metastatic liver lesions size correlated with the TL in metastases (p < 0.05). Following the neoadjuvant treatment, the patients with rectal cancer had shortened telomeres in tumour tissue than prior to the therapy (p = 0.01). Patients with a TL ratio between tumour tissue and the adjacent non-cancerous mucosa of ≥ 0.387 were associated with increased overall survival (p = 0.01). This study provides insights into TL dynamics during progression of the disease. The results show TL differences in metastatic lesions and may help in clinical practice to predict the patient's prognosis.
BACKGROUND: Tobacco smoking is an established risk factor for colorectal cancer. However, genetically defined population subgroups may have increased susceptibility to smoking-related effects on colorectal cancer. METHODS: A genome-wide interaction scan was performed including 33,756 colorectal cancer cases and 44,346 controls from three genetic consortia. RESULTS: Evidence of an interaction was observed between smoking status (ever vs. never smokers) and a locus on 3p12.1 (rs9880919, P = 4.58 × 10-8), with higher associated risk in subjects carrying the GG genotype [OR, 1.25; 95% confidence interval (CI), 1.20-1.30] compared with the other genotypes (OR <1.17 for GA and AA). Among ever smokers, we observed interactions between smoking intensity (increase in 10 cigarettes smoked per day) and two loci on 6p21.33 (rs4151657, P = 1.72 × 10-8) and 8q24.23 (rs7005722, P = 2.88 × 10-8). Subjects carrying the rs4151657 TT genotype showed higher risk (OR, 1.12; 95% CI, 1.09-1.16) compared with the other genotypes (OR <1.06 for TC and CC). Similarly, higher risk was observed among subjects carrying the rs7005722 AA genotype (OR, 1.17; 95% CI, 1.07-1.28) compared with the other genotypes (OR <1.13 for AC and CC). Functional annotation revealed that SNPs in 3p12.1 and 6p21.33 loci were located in regulatory regions, and were associated with expression levels of nearby genes. Genetic models predicting gene expression revealed that smoking parameters were associated with lower colorectal cancer risk with higher expression levels of CADM2 (3p12.1) and ATF6B (6p21.33). CONCLUSIONS: Our study identified novel genetic loci that may modulate the risk for colorectal cancer of smoking status and intensity, linked to tumor suppression and immune response. IMPACT: These findings can guide potential prevention treatments.
- MeSH
- Genetic Predisposition to Disease * MeSH
- Genetic Loci MeSH
- Genotype MeSH
- Polymorphism, Single Nucleotide MeSH
- Colorectal Neoplasms * epidemiology MeSH
- Tobacco Smoking MeSH
- Smoking genetics MeSH
- Humans MeSH
- Risk Factors MeSH
- Case-Control Studies MeSH
- Inflammation MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, N.I.H., Extramural MeSH
BACKGROUND: Glycemic traits-such as hyperinsulinemia, hyperglycemia, and type 2 diabetes-have been associated with higher colorectal cancer risk in observational studies; however, causality of these associations is uncertain. We used Mendelian randomization (MR) to estimate the causal effects of fasting insulin, 2-hour glucose, fasting glucose, glycated hemoglobin (HbA1c), and type 2 diabetes with colorectal cancer. METHODS: Genome-wide association study summary data were used to identify genetic variants associated with circulating levels of fasting insulin (n = 34), 2-hour glucose (n = 13), fasting glucose (n = 70), HbA1c (n = 221), and type 2 diabetes (n = 268). Using 2-sample MR, we examined these variants in relation to colorectal cancer risk (48 214 case patient and 64 159 control patients). RESULTS: In inverse-variance models, higher fasting insulin levels increased colorectal cancer risk (odds ratio [OR] per 1-SD = 1.65, 95% confidence interval [CI] = 1.15 to 2.36). We found no evidence of any effect of 2-hour glucose (OR per 1-SD = 1.02, 95% CI = 0.86 to 1.21) or fasting glucose (OR per 1-SD = 1.04, 95% CI = 0.88 to 1.23) concentrations on colorectal cancer risk. Genetic liability to type 2 diabetes (OR per 1-unit increase in log odds = 1.04, 95% CI = 1.01 to 1.07) and higher HbA1c levels (OR per 1-SD = 1.09, 95% CI = 1.00 to 1.19) increased colorectal cancer risk, although these findings may have been biased by pleiotropy. Higher HbA1c concentrations increased rectal cancer risk in men (OR per 1-SD = 1.21, 95% CI = 1.05 to 1.40), but not in women. CONCLUSIONS: Our results support a causal effect of higher fasting insulin, but not glucose traits or type 2 diabetes, on increased colorectal cancer risk. This suggests that pharmacological or lifestyle interventions that lower circulating insulin levels may be beneficial in preventing colorectal tumorigenesis.
- MeSH
- Genome-Wide Association Study MeSH
- Diabetes Mellitus, Type 2 * complications epidemiology genetics MeSH
- Glycated Hemoglobin analysis MeSH
- Hyperinsulinism * complications genetics MeSH
- Insulin MeSH
- Polymorphism, Single Nucleotide MeSH
- Colorectal Neoplasms * complications epidemiology genetics MeSH
- Blood Glucose analysis genetics MeSH
- Humans MeSH
- Mendelian Randomization Analysis MeSH
- Risk Factors MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Glycated Hemoglobin A MeSH
- Insulin MeSH
- Blood Glucose MeSH
