Genetic Variation in the Inflammation and Innate Immunity Pathways and Colorectal Cancer Risk

It is widely accepted that chronic inflammation plays a role in the etiology of colorectal cancer. Using a two-stage design, we examined the associations between colorectal cancer and common variation in 37 key genes in the inflammation and innate immunity pathways

Risk of extracolonic cancers for people with biallelic and monoallelic mutations in MUTYH: Extracolonic cancer risks for people with biallelic and monoallelicMUTYHmutations

Germline mutations in the DNA base excision repair gene MUTYH are known to increase a carrier’s risk of colorectal cancer. However, the risks of other (extracolonic) cancers for MUTYH mutation carriers are not well defined. We identified 266 probands (91% Caucasians) with a MUTYH mutation (41 biallelic and 225 monoallelic) from the Colon Cancer Family Registry. Mutation status, sex, age, and histories of cancer from their 1,903 first- and 3,255 second-degree relatives, were analysed using modified segregation analysis conditioned on the ascertainment criteria. Compared with incidences for the general population, hazard ratios (HRs) (95% confidence intervals [CIs]) for biallelic MUTYH mutation carriers were: urinary bladder cancer, 19(3.7–97); and ovarian cancer, 17(2.4–115). The HRs (95%CI) for monoallelic MUTYH mutation carriers were: gastric cancer, 9.3(6.7–13); hepatobiliary cancer, 4.5(2.7–7.5); endometrial cancer, 2.1(1.1–3.9); and breast cancer, 1.4(1.0–2.0). There was no evidence for an increased risk of cancers at the other sites examined (brain, pancreas, kidney or prostate). Based on the USA population incidences, the estimated cumulative risks (95%CI) to age 70 years for biallelic mutation carriers were: bladder cancer, 25%(5%–77%) for males and 8%(2%–33%) for females; and ovarian cancer, 14%(2%–65%). The cumulative risks (95%CI) for monoallelic mutation carriers were: gastric cancer, 5%(4%–7%) for males and 2.3%(1.7%–3.3%) for females; hepatobiliary cancer, 3%(2%–5%) for males and 1.4%(0.8%–2.3%) for females; endometrial cancer, 3%(2%–6%); and breast cancer 11%(8%–16%). These unbiased estimates of both relative and absolute risks of extracolonic cancers for people, mostly Caucasians, with MUTYH mutations will be important for their clinical management

Genetic Variation in the Inflammation and Innate Immunity Pathways and Colorectal Cancer Risk

BACKGROUND: It is widely accepted that chronic inflammation plays a role in the etiology of colorectal cancer. Using a two-stage design, we examined the associations between colorectal cancer and common variation in 37 key genes in the inflammation and innate immunity pathways. METHODS: In the discovery stage, 2,322 discordant sibships (2,535 cases, 3,915 sibling controls) from the Colorectal Cancer Family Registry were genotyped for over 600 tagSNPs and 99 SNPs were selected for further examination based on strength of association. In the second stage, 351 SNPs tagging gene regions covered by the 99 SNPs were tested in 4,783 Multiethnic Cohort subjects (2,153 cases, 2,630 controls). RESULTS: The association between rs9858822 in the PPARG gene and colorectal cancer was statistically significant at the end of the second stage (odds ratio per allele = 1.36, Bonferroni-adjusted P = 0.045), based on the “effective” number of markers in Stage 2 (n = 306). The risk allele C was common (frequency 0.3) in African Americans but rare (frequency < 0.03) in whites, Japanese Americans, Latinos and Native Hawaiians. No statistically significant heterogeneity of effects across race/ethnicity, BMI levels, regular aspirin use or pack-years of smoking was detected for this SNP. Suggestive associations were also observed for several SNPs in close vicinity to rs9858822. CONCLUSIONS: Our results provide new evidence of association between PPARG variants and colorectal cancer risk. IMPACT: Further replication in independent samples is warranted

Fine-mapping of genome-wide association study-identified risk loci for colorectal cancer in African Americans

Genome-wide association studies of colorectal cancer (CRC) in Europeans and Asians have identified 21 risk susceptibility regions [29 index single-nucleotide polymorphisms (SNPs)]. Characterizing these risk regions in diverse racial groups with different linkage disequilibrium (LD) structure can help localize causal variants. We examined associations between CRC and all 29 index SNPs in 6597 African Americans (1894 cases and 4703 controls). Nine SNPs in eight regions (5q31.1, 6q26-q27, 8q23.3, 8q24.21, 11q13.4, 15q13.3, 18q21.1 and 20p12.3) formally replicated in our data with one-sided P-values <0.05 and the same risk directions as reported previously. We performed fine-mapping of the 21 risk regions (including 250 kb on both sides of the index SNPs) using genotyped and imputed markers at the density of the 1000 Genomes Project to search for additional or more predictive risk markers. Among the SNPs correlated with the index variants, two markers, rs12759486 (or rs7547751, a putative functional variant in perfect LD with it) in 1q41 and rs7252505 in 19q13.1, were more strongly and statistically significantly associated with CRC (P < 0.0006). The average per allele risk was improved using the replicated index variants and the two new markers (odds ratio = 1.14, P = 6.5 × 10(−16)) in African Americans, compared with using all index SNPs (odds ratio = 1.07, P = 3.4 × 10(−10)). The contribution of the two new risk SNPs to CRC heritability was estimated to be 1.5% in African Americans. This study highlights the importance of fine-mapping in diverse populations

Trans-ethnic genome-wide association study of colorectal cancer identifies a new susceptibility locus in VTI1A

The genetic basis of sporadic colorectal cancer (CRC) is not well explained by known risk polymorphisms. Here we perform a meta-analysis of two genome-wide association studies in 2,627 cases and 3,797 controls of Japanese ancestry and 1,894 cases and 4,703 controls of African ancestry, to identify genetic variants that contribute to CRC susceptibility. We replicate genome-wide statistically significant associations (P < 5×10−8) in 16,823 cases and 18,211 controls of European ancestry. This study reveals a new pan-ethnic CRC risk locus at 10q25 (rs12241008, intronic to VTI1A; P=1.4×10−9), providing additional insight into the etiology of CRC and highlighting the value of association mapping in diverse populations

Trans-ethnic genome-wide association study of colorectal cancer identifies a new susceptibility locus in VTI1A

The genetic basis of sporadic colorectal cancer (CRC) is not well explained by known risk polymorphisms. Here we perform a meta-analysis of two genome-wide association studies in 2,627 cases and 3,797 controls of Japanese ancestry and 1,894 cases and 4,703 controls of African ancestry, to identify genetic variants that contribute to CRC susceptibility. We replicate genome-wide statistically significant associations (P<5 x 10^-8) in 16,823 cases and 18,211 controls of European ancestry. This study reveals a new pan-ethnic CRC risk locus at 10q25 (rs12241008, intronic to VTI1A; P = 1.4 x 10^-9), providing additional insight into the aetiology of CRC and highlighting the value of association mapping in diverse populations