Association studies on 11 published colorectal cancer risk loci

Susceptibility genetic variants associated with early-onset colorectal cancer

Colorectal cancer (CRC) is the second most common cancer in Western countries. Hereditary forms only correspond to 5% of CRC burden. Recently, genome-wide association studies have identified common low-penetrant CRC genetic susceptibility loci. Early-onset CRC (CRC<50 years old) is especially suggestive of hereditary predisposition although 85-90% of heritability still remains unidentified. CRC<50 patients (n = 191) were compared with a late-onset CRC group (CRC>65 years old) (n = 1264). CRC susceptibility variants at 8q23.3 (rs16892766), 8q24.21 (rs6983267), 10p14 (rs10795668), 11q23.1 (rs3802842), 15q13.3 (rs4779584), 18q21 (rs4939827), 14q22.2 (rs4444235), 16q22.1 (rs9929218), 19q13.1 (rs10411210) and 20p12.3 (rs961253) were genotyped in all DNA samples. A genotype-phenotype correlation with clinical and pathological characteristics in both groups was performed. Risk allele carriers for rs3802842 [Odds ratio (OR) = 1.5, 95% confidence interval (CI) 1.1-2.05, P = 0.0096, dominant model) and rs4779584 (OR = 1.39, 95% CI 1.02-1.9, P = 0.0396, dominant model) were more frequent in the CRC<50 group, whereas homozygotes for rs10795668 risk allele were also more frequent in the early-onset CRC (P = 0.02, codominant model). Regarding early-onset cases, 14q22 (rs4444235), 11q23 (rs3802842) and 20p12 (rs961253) variants were more associated with family history of CRC or tumors of the Lynch syndrome spectrum excluding CRC. In our entire cohort, sum of risk alleles was significantly higher in patients with a CRC family history (OR = 1.40, 95% CI 1.06-1.85, P = 0.01). In conclusion, variants at 10p14 (rs10795668), 11q23.1 (rs3802842) and 15q13.3 (rs4779584) may have a predominant role in predisposition to early-onset CRC. Association of CRC susceptibility variants with some patient's familiar and personal features could be relevant for screening and surveillance strategies in this high-risk group and it should be explored in further studies.

Comprehensive evaluation of the impact of 14 genetic variants on colorectal cancer phenotype and risk

To comprehensively evaluate the impact of recently identified colorectal cancer (CRC) variants at 1q41, 3q26.2, 8q23.3, 8q24.21, 10p14, 11q23.1, 12q13.13, 14q22.2, 15q13.3, 16q22.1, 18q21.1, 19q13.11, 20p12.3, and 20q13.33 on risk and CRC phenotype, the authors analyzed 8,878 cases and 6,051 controls from the United Kingdom ascertained in 1999-2007. The impact of variants on the familial CRC risk was enumerated from age-, sex-, and calendar-specific CRC rates in the 50,924 first-degree relatives of cases. Each of the 14 susceptibility loci independently influences CRC with the risk increasing with increasing number of risk alleles carried (per allele odds ratio = 1.13; P = 2.99 × 10(-58)) and, for those within the upper quintile, there is a 2.3-fold increased risk. In first-degree relatives of cases with ≤17, 18-21, and ≥22 risk alleles, standardized incidence ratios were 1.76, 2.08, and 2.25, respectively. Although the discriminatory attributes of the 14 CRC susceptibility loci for individual risk prediction are poor (area under the curve = 0.58), they may allow subgroups of the population at different CRC risks to be distinguished.

Bone morphogenetic protein-4 polymorphism and colorectal cancer risk: a meta analysis

BMP4 rs4444235 is a candidate susceptibility allele that has been associated with an increased risk of colorectal cancer. This study was conducted to examine the association between BMP4 rs4444235 polymorphism and colorectal cancer risk. Odds ratio (ORs) with 95% CIs was pooled as effect indicator. A comprehensive search of related publications was conducted and those which met the inclusion criteria were included. Test of heterogeneity, meta-regression, subgroup analysis, cumulative meta-analysis, assessment of publication bias, and sensitivity test were performed using Stata 11.0. 8 articles on rs4444235 including 19,893 cases and 22,106 controls were included. There was slight heterogeneity which may come from ethnicity and source of control. Pooled results for all five genetic models were statistically significant. ORs were 1.063 (95% CI = (1.034, 1.092)), 1.081 (95% CI = (1.028, 1.136)), and 1.166(95% CI = (1.081, 1.258)) for C versus T, TC versus TT, and CC versus TT comparisons respectively. In Caucasian population, carriers of C allele, CC genotype and TC genotype were at an increased risk of developing CRC, with an OR of 1.079 (95% CI = (1.044, 1.114)), 1.095 (95% CI = (1.034, 1.159)), and 1.199 (95% CI = (1.117,1.287)) respectively. Cumulative meta-analysis indicated that pooled ORs were approximating 1.1 with publication year passing. No significant publication bias was suggested. Sensitivity test indicated stable results. In conclusion, BMP4-rs4444235 polymorphism is probably associated with CRC risk, and C allele is a possible risk factor in overall population. The same conclusion was drawn in Caucasians, but no significant results were obtained in other ethnic populations probably due to limited sample sizes.

Risk prediction models for colorectal cancer: a review

Risk prediction models are important to identify individuals at high risk of developing the disease who can then be offered individually tailored clinical management, targeted screening and interventions to reduce the burden of disease. They are also useful for research purposes when attempting to identify new risk factors for the disease. In this article, we review the risk prediction models that have been developed for colorectal cancer and appraise their applicability, strengths, and weaknesses. We also discuss the factors to be considered for future development and improvement of models for colorectal cancer risk prediction. We conclude that there is no model that sufficiently covers the known risk factors for colorectal cancer that is suitable for assessment of people from across the full range of risk and that a new comprehensive model is needed.

Review: Single nucleotide polymorphisms associated with the oncogenesis of colorectal cancer

Colorectal cancer (CRC) is provoked by interactions between genetic and environmental factors. We herein review the incidence and the mechanisms of action of the reported single nucleotide polymorphisms (SNPs) in the oncogenesis of CRC. More than 15 reports have studied the SNPs at 8q24, which are associated with the incidence of CRC as well as prostate cancer. We have also reported a SNP at the 10p14 locus, and the risks of other loci for CRC oncogenesis. With regard to the underlying mechanism for CRC, 8q24 is a locus of the long-enhancer site for MYC, which could determine the efficacy of MYC transcription. We suggest that 8q24 SNPs might be associated with the progression of CRC cases mediated by MYC expression. In this report, we summarize the published studies of the genetic background SNPs in the oncogenesis of CRC. The level of risk (most studies indicated less than a twofold increase) for CRC was lower than anticipated. Therefore, it is necessary to identify bona fide SNPs that precisely predict the risk for CRC. Alternatively, it is important to consider other factors, such as environmental or lifestyle-related factors, for the future prevention of CRC.

Association of 8q24.21 loci with the risk of colorectal cancer: a systematic review and meta-analysis

BACKGROUND AND AIM

Recent genome-wide association studies of colorectal cancer (CRC) have identified rs6983267 and trs10505477 polymorphisms as key loci in the 8q24 region to be associated with CRC. In the present study, we performed a meta-analysis to determine whether these loci are risk factors for susceptibility to CRC.

METHODS

We meta-analyzed the 22 included studies (47 003 cases and 45 754 controls) that evaluated the association of rs6983267 and trs10505477 with CRC under alternative genetic models.

RESULTS

A meta-analysis of the pooled data showed allelic and genotypic association of the rs6983267 polymorphism with CRC risk in Asians, Europeans, and European-Americans. A subanalysis of the US studies showed negative results in the studies with non-identified ethnicity of the patients. A meta-analysis of included studies of rs10505477 polymorphisms identified allelic and genotypic associations with CRC risk in the US patients. A further meta-analysis of the US studies demonstrated positive results in the studies with non-identified ethnicity of the samples.

CONCLUSION

Our data suggested that the rs6983267 G > T polymorphism is a risk factor for CRC in Asians, Europeans, and Americans with European ancestry.

Association between polymorphism rs6983267 and gastric cancer risk in Chinese population

AIM: To explore the association between single nucleotide polymorphisms (SNPs) at 8q24 and gastric cancer risk.

METHODS: A case-control investigation including 212 gastric cancer patients and 377 healthy controls was conducted. The genotypes of SNPs (rs6983267, rs7008482 and rs10808555) were examined and established through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Multivariate logistic regression models were used to evaluate the association between SNPs and gastric cancer.

RESULTS: The genotype frequencies of rs6983267 in gastric cancer patients were obviously different from those in the control (P = 0.005). GT genotype of rs6983267 was associated with an increased risk of gastric cancer compared with GG genotype (adjusted odds ratio = 2.01, 95% confidence interval: 1.28-3.14). Further stratified analysis indicated that rs6983267 GT genotype facilitated the risk of gastric cancer of non-cardiac and intestinal type (OR: 2.638, 95% CI: 1.464-4.753; OR: 1.916, 95% CI: 1.166-3.150, respectively).

CONCLUSION: This study demonstrates for the first time that rs6983267 is involved in susceptibility to gastric cancer, although further large-sample investigations are still needed.

Genetic variants on chromosome 8q24 and colorectal neoplasia risk: a case-control study in China and a meta-analysis of the published literature

Previous studies have found that common genetic variants on chromosome 8q24 are associated with the risk of developing colorectal neoplasia. We conducted a hospital-based case-control study, including 435 cases and 788 unrelated controls to investigate the associations between common variants on 8q24 and the risk of colorectal cancer in a Chinese population. We also evaluated the association of rs6983267 with colorectal neoplasia in the published literature via a meta-analysis study. We found that rs6983267 was significantly associated with the risk of colorectal cancer in the Chinese population, with an adjusted odds-ratio (OR) for the GT heterozygotes and GG homozygotes of 1.30 (95% CI  = 0.98–1.71, P = 0.069) and 1.66 (95% CI  = 1.18–2.34, P = 0.004), respectively, compared to the TT homozygotes, with a P-trend value of 0.003. No association was found for the other three loci (rs16901979, rs1447295 and rs7837688). In the meta-analysis of the published genetic association studies, the rs6983267 variant was found to be associated with an increased risk of colorectal neoplasia. The heterozygous GT carriers showed a 20% increased risk of colorectal neoplasia (OR  = 1.20, 95% CI  = 1.16–1.25; random effects model) with a summary OR for homozygous GG carriers of 1.39 (95% CI  = 1.32–1.48; random effects model) compared to the TT genotype carriers. We found no significant differences between the association of rs6983267 and colorectal cancer and colorectal adenomas. In summary, our study confirms that the variant rs6983267 is a risk factor for colorectal neoplasia in various populations, including the Chinese population.

Generalizability and epidemiologic characterization of eleven colorectal cancer GWAS hits in multiple populations

BACKGROUND

Genome-wide association studies (GWAS) in populations of European ancestry have identified several loci that confer an increased risk of colorectal cancer (CRC).

METHODS

We studied the generalizability of the associations with 11 risk variants for CRC on 8q23 (rs16892766), 8q24 (rs6983267), 9p24 (rs719725), 10p14 (rs10795668), 11q23 (rs3802842), 14q22 (rs4444235), 15q13 (rs4779584), 16q22 (rs9929218), 18q21 (rs4939827), 19q13 (rs10411210), and 20p12 (rs961253) in a multiethnic sample of 2,472 CRC cases, 839 adenoma cases and 4,466 controls comprised of European American, African American, Native Hawaiian, Japanese American, and Latino men and women. Because findings for CRC and adenoma were similar, we combined both groups in the analyses.

RESULTS

We confirmed the associations with an increased risk of CRC/adenoma for the 8q24, 11q23 and 15q13 loci in European Americans, and observed significant associations between the 8q24 and 20p12 loci with CRC/adenoma risk in African Americans. Moreover, we found statistically significant cumulative effects of risk alleles on CRC/adenoma risk in all populations (odds ratio [OR] per allele = 1.07-1.09, P ≤ 0.039) except in Japanese Americans (OR = 1.01, P = 0.52). We found heterogeneity in the associations by tumor subsite, age of CRC/adenoma onset, sex, body mass index (BMI), and smoking status for some of the variants.

CONCLUSIONS

These results provide evidence that the known variants are in aggregate significantly associated with CRC/adenoma risk in multiple populations except Japanese Americans, and the influences may differ across groups defined by clinicopathological characteristics for some variants.

IMPACT

These results underline the importance of studying the epidemiologic architecture of these genetic effects in large and diverse populations.