Evaluation of genetic variants in association with colorectal cancer risk and survival in Asians

Genome‐wide association studies (GWAS) have identified over 40 genetic loci associated with colorectal cancer (CRC) risk. The association of single nucleotide polymorphisms (SNPs) at these loci with CRC risk and survival has not been adequately evaluated in East Asians. GWAS‐identified CRC risk variants were used to construct weighted genetic risk scores (GRSs). We evaluated these GRSs in association with CRC risk in 3,303 CRC cases and 3,553 controls using logistic regression models. Associations with overall and CRC‐specific survival were assessed in 731 CRC patients using Cox regression models. The association between the GRSs (overall and Asian‐specific) and CRC risk was approximately twofold (highest vs . lowest quintile), and the shape of the dose–response was linear (p _trend = 1.24 × 10^?13 and 3.02 × 10^?14 for overall GRS and Asian‐specific GRS, respectively). The association of the GRS with CRC risk was stronger among those with a family history of CRC (p _interaction = 0.007). Asian‐specific GRS using previously reported survival SNPs increased risk for mortality and the shape of the dose–response was linear for CRC‐specific and all‐cause mortality (p _trend = 0.01 and 0.006, respectively). Furthermore, the minor alleles of rs6983267 and rs1957636 were associated with worse CRC‐specific and overall survival. We show that GRSs constructed using GWAS‐identified common variants are strongly associated with CRC risk in Asians. We confirm previous findings for the possible association between some SNPs with survival, and provide evidence for two additional CRC risk variants that may be related to CRC survival.     

The association of XPC polymorphisms and tea drinking with colorectal cancer risk in a Chinese population

The xeroderma pigmentosum complementation group C (XPC) is responsible for removal of bulky helix-distorting DNA lesions. Several polymorphisms of XPC gene may modulate the colorectal cancer (CRC) susceptibility. We assessed the association of XPC Lys939Gln (A/C), Ala499Val (C/T), and PAT (-/+) polymorphisms with CRC risk in a population-based case-control study which included 421 CRC patients and 845 controls. For Lys939Gln, the CC genotype was associated with a significantly increased risk of CRC (odds ratio (OR)=1.5; 95% confidence interval (CI)=1.0-2.2) compared with the AA genotype. The subjects with PAT +/+ genotype had a significantly increased risk of CRC (OR=1.5; 95% CI=1.0-2.3), compared with those with PAT-/- genotype. Though no significant association between Ala499Val and CRC risk was observed, we found that individuals carrying the CT+TT genotypes showed a significantly decreased risk of rectal cancer (OR=0.7; 95% CI=0.5-1.0). Additionally, the haplotype C+C was associated with a significantly increased CRC risk (OR=1.3; 95% CI=1.0-1.6), compared with the most common haplotype A-T. Further, individuals with four or more risk alleles exhibited a significantly increased risk of CRC (OR=1.4; 95% CI=1.0-2.0), with a significant gene-dosage effect (P for trend=0.038). Besides, never tea drinking was associated with a significantly increased risk of CRC (OR=2.3; 95% CI=1.7-3.3). Our results suggest that the XPC polymorphisms may modulate CRC susceptibility independently or jointly, and tea drinking has a protective effect on CRC.     

Identification of candidate genes carrying polymorphisms associated with the risk of colorectal cancer by analyzing the colorectal mutome and microRNAome

BACKGROUND:

The presence of single‐nucleotide polymorphisms (SNPs) within the 3′‐untranslated regions of genes could affect the binding between a microRNA (miRNA) and its target, with consequences on gene expression regulation. Considering the important role of miRNAs in carcinogenesis, it is hypothesized here that these SNPs could also affect the individual risk of colorectal cancer (CRC).

METHODS:

To test this hypothesis, a list was developed of 140 somatically mutated genes deduced from previous works on the mutome of the CRC. A further selection was conducted of SNPs within target sites for miRNAs that are expressed only in the colorectum (the colorectal microRNAome) and having adequate population frequencies. This yielded 12 SNPs that were genotyped in a case‐control association study on 717 colorectal cases and 1171 controls from the Czech Republic.

RESULTS:

Statistically significant associations were found between the risk of CRC and the variant alleles of KIAA0182 (rs709805) (odds ratio = 1.57; 95% confidence interval = 1.06‐2.78, for the variant homozygotes) and NUP210 genes (rs354476) (odds ratio = 1.36; 95% confidence interval = 1.02‐1.82, for the variant homozygotes).

CONCLUSIONS:

The results support the study hypothesis and highlight the importance of SNPs within miRNA‐dependent regulatory regions. Further studies on the role exerted by NUP210 and KIAA0182 in colorectal carcinogenesis are warranted. Cancer 2012. © 2012 American Cancer Society.     

Adiponectin and adiponectin receptor in relation to colorectal cancer progression

Although obesity is a risk factor for colorectal cancer, the underlying mechanism is not clear. Adiponectin is an adipokine that binds to 2 types of receptors, AdipoR1 and AdipoR2. The plasma concentrations of adiponectin are reduced in obese individuals and adiponectin has been reported to have anticarcinogenic properties. Furthermore, AdipoR1 and AdipoR2 have been reported to be expressed in several malignancies. However, little is known about the expression of AdipoR1 and AdipoR2 in colorectal cancer and its clinicopathological implications. In addition, the relationship between adiponectin and colorectal cancer has not yet been determined. Here, we sought to investigate adiponectin and adiponectin receptors in relation to colorectal cancer. AdipoR1 and AdipoR2 immunostaining was detected in 72 and 68% of human colorectal cancer tissue, respectively. AdipoR1 and AdipoR2 expression levels were inversely related to T stage. The lowest AdipoR1 and AdipoR2 expression were detected in poorly differentiated adenocarcinoma. RT-PCR also showed the expression of AdipoR1 and AdipoR2 in HCT116 and SW620. MTT assay and TUNEL assay demonstrated the tendency of growth inhibition and apoptosis induction in both cell lines after full-length adiponectin treatment although statistically insignificant. Microarray analysis revealed several gene responses to full-length adiponectin, including upregulation of ENDOGL1 and MT1G. In conclusion, AdipoR1 and AdipoR2 may be intimately related to the progression of colorectal cancer. Further studies may be warranted to assess adiponectin and its receptors as a novel target for inhibition of colorectal cancer growth.     

Body mass index and colorectal cancer risk: A Mendelian randomization study

Traditional observational studies have reported a positive association between higher body mass index (BMI) and the risk of colorectal cancer (CRC). However, evidence from other approaches to pursue the causal relationship between BMI and CRC is sparse. A two-sample Mendelian randomization (MR) study was undertaken using 68 single nucleotide polymorphisms (SNPs) from the Japanese genome-wide association study (GWAS) and 654 SNPs from the GWAS catalogue for BMI as sets of instrumental variables. For the analysis of SNP-BMI associations, we undertook a meta-analysis with 36 303 participants in the Japanese Consortium of Genetic Epidemiology studies (J-CGE), comprising normal populations. For the analysis of SNP-CRC associations, we utilized 7636 CRC cases and 37 141 controls from five studies in Japan, and undertook a meta-analysis. Mendelian randomization analysis of inverse-variance weighted method indicated that a one-unit (kg/m²) increase in genetically predicted BMI was associated with an odds ratio of 1.13 (95% confidence interval, 1.06-1.20; P value <.001) for CRC using the set of 68 SNPs, and an odds ratio of 1.07 (1.03-1.11, 0.001) for CRC using the set of 654 SNPs. Sensitivity analyses robustly showed increased odds ratios for CRC for every one-unit increase in genetically predicted BMI. Our MR analyses strongly support the evidence that higher BMI influences the risk of CRC. Although Asians are generally leaner than Europeans and North Americans, avoiding higher BMI seems to be important for the prevention of CRC in Asian populations.     

Genetic variation in the vitamin D related pathway and breast cancer risk in women of African ancestry in the root consortium

The vitamin D related pathway has been evaluated in carcinogenesis but its genetic contribution remains poorly understood. We examined single‐nucleotide polymorphisms (SNPs) in the vitamin D related pathway genes using data from a genome‐wide association study (GWAS) of breast cancer in the African Diaspora that included 3,686 participants (1,657 cases). Pathway‐ and gene‐level analyses were conducted using the adaptive rank truncated product test. Odds ratios (OR) and 95% confidence intervals (CI) were estimated at SNP‐level. After stringent Bonferroni corrections, we observed no significant association between variants in the vitamin D pathway and breast cancer risk at the pathway‐, gene‐, or SNP‐level. In addition, no association was found for either the reported signals from GWASs of vitamin D related traits, or the SNPs within vitamin D receptor (VDR) binding regions. Furthermore, a decrease in genetically predicted 25(OH)D levels by Mendelian randomization was not associated with breast cancer (p = 0.23). However, an association for breast cancer with the pigment synthesis/metabolism pathway almost approached significance (pathway‐level p = 0.08), driven primarily by a nonsense SNP rs41302073 in TYRP1, with an OR of 1.54 (95% CI = 1.24–1.91, p_adj = 0.007). In conclusion, we found no evidence to support an association between vitamin D status and breast cancer risk in women of African ancestry, suggesting that vitamin D is unlikely to have significant effect on breast carcinogenesis. Interestingly, TYRP1 might be related to breast cancer through a non‐vitamin D relevant mechanism but further studies are needed.     

p53 Arg72Pro polymorphism and risk of colorectal adenoma and cancer

A single nucleotide polymorphism (SNP) at codon 72 of the p53 gene (Arg72Pro) alters the p53 protein structure and affects its activity. We investigated this SNP in relation to colorectal adenoma and cancer among men and women from case-control studies nested within the Nurses' Health Study, the Health Professionals Follow-up Study and the Physicians' Health Study. Among 856 colorectal adenoma cases and 1,184 controls, we observed a modest association with p53 Arg72Pro genotype (multivariate odds ratio (OR) = 1.25, 95% confidence interval (CI) = 1.04-1.50 for Arg/Pro and Pro/Pro vs. Arg/Arg). This association did not vary by colorectal site or by sex. Among 442 colorectal cancer cases and 904 controls, we observed no significant overall association between p53 Arg72Pro genotype and colorectal cancer (multivariate OR = 1.14, 95% CI = 0.90-1.45). However, when colorectal site and sex was accounted for, the Pro carrier genotypes compared to Arg/Arg were associated with an increased risk of proximal colon cancers in women (multivariate OR = 2.59, 95% CI = 1.49-4.52) though not with distal colon or rectal cancers, while among men the same genotypes were associated with an increased risk of distal colon cancers (multivariate OR = 2.09, 95% CI = 1.28-3.40) but not proximal colon or rectal cancers. Our results suggest that Arg72Pro may play a role in the early stages of colorectal neoplasia and possibly in progression to invasive disease, depending on site and sex.     

Association of the TP53 codon 72 polymorphism with colorectal cancer in a Chinese population

A TP53 gene polymorphism, resulting in an arginine (R) to proline (P) at codon 72 (TP53 R72P), has been associated with the susceptibility to various cancers. To better understand the role of this polymorphism in colorectal cancer etiology, we examined the association between TP53 R72P and colorectal cancer risk in 345 patients with colorectal cancer and 670 controls in a Chinese population. We observed that subjects with RP and PP genotypes had a 1.60-fold and a 2.37-fold increased risk for colorectal cancer, respectively. The 72P allele conferred a more pronounced increase in colorectal cancer risk among alcohol consumers (heterozygotes: OR = 3.01; homozygotes: OR = 4.71). The TP53 R72P polymorphism was not linked to tumor location, histologic grade, lymph node metastases, Dukes stage, p53 positivity, or age at diagnosis, but to tumor size. We conclude that the TP53 R72P polymorphism may contribute to the etiology of colorectal cancer in the Chinese population, particularly among alcohol consumers.     

MTHFR基因A1298C多态性与肠癌遗传易感相关性研究

目的：探讨亚甲基四氢还原酶基因（MTHFR）第7外显子区单核苷酸多态（single nucleotide polymo-rphism,SNP）位点A1298C（rs1801131）与中国南方人群肠癌发生的相关性。方法：应用基质辅助激光解吸电离飞行时间（MALDI-TOF）质谱检测224例肠癌和224例对照MTHFR基因多态位点rs1801131的基因型。结果：MTHFR rs1801131多态位点AA、AC、CC三种基因型在肠癌的频率为63.4%、32.6%和4.0%,与对照组（68.8%,29.9%和3%）相比差异不显著（P=0.12）;但男性人群中病例组和正常组的基因型差异接近显著（P=0.05）,携带CC基因型男性个体的肠癌发病风险显著增加（OR=8.38,95%CI：1.01-69.64）;相对于直肠癌,结肠癌与正常对照的基因型频率差别更大,P值分别为0.84和0.08;且男性结肠癌患者基因型分布和对照差异显著（P=0.01）。结论：MTHFR基因第7外显子区rs1801131位点的单核苷酸多态性可能与中国南方人群结肠癌的遗传易感性相关,而与直肠癌无关,特别是在男性人群中rs1801131 CC和CA基因型可能增加个体患结肠癌的风险。     

MTHFR基因A1298C多态性与肠癌遗传易感相关性研究

目的:探讨亚甲基四氢还原酶基因(MTHFR)第7外显子区单核苷酸多态(single nucleotide polymorphism,SNP)位点A1298C(rs1801131)与中国南方人群肠癌发生的相关性.方法:应用基质辅助激光解吸电离飞行时间(MALDI-TOF)质谱检测224例肠癌和224例对照MTHFR基因多态位点rs1801131的基因型.结果:MTHFR rs1801131多态位点AA、AC、CC三种基因型在肠癌的频率为63.4%、32.6%和4.0%,与对照组(68.8%,29.9%和3%)相比差异不显著(P=0.12);但男性人群中病例组和正常组的基因型差异接近显著(P=0.05),携带CC基因型男性个体的肠癌发病风险显著增加(OR=8.38,95%CI:1.01-69.64);相对于直肠癌,结肠癌与正常对照的基因型频率差别更大,P值分别为0.84和0.08;且男性结肠癌患者基因型分布和对照差异显著(P=0.01).结论:MTHFR基因第7外显子区rs1801131位点的单核苷酸多态性可能与中国南方人群结肠癌的遗传易感性相关,而与直肠癌无关,特别是在男性人群中rs1801131 CC和CA基因型可能增加个体患结肠癌的风险.     

Common germline variation in mismatch repair genes and survival after a diagnosis of colorectal cancer

The mismatch repair (MMR) genes are involved in the maintenance of genomic integrity. Recently, we showed that common variants in these genes are unlikely to contribute significantly to colorectal cancer risk. The aim of this study was to investigate the role of common variants in the mismatch repair pathway as prognostic markers in colorectal cancer patients. We genotyped 2,060 patients for 68 SNPs in 7 mismatch repair genes (MLH1, MLH3, MSH2, MSH3, MSH6, PMS1 and PMS2), using a single nucleotide polymorphism (SNP) tagging approach. Genotypes at the tag SNPs and multi‐SNP haplotypes were tested for association with overall survival (OS) and disease specific survival (DSS) using a Cox regression model. Eight SNPs and 10 haplotypes were significant at a nominal p < 0.05 in the univariate analyses. Stepwise analysis showed that haplotype effects were mainly due to associated SNPs carried by these haplotypes. After adjustment for sex, age at diagnosis and stage when using overall survival and stage only when using disease specific survival, prognostic values were unattenuated. The most significant SNP associated with disease specific survival after adjustment was rs863221, located in MSH3 (HR: 0.59, 95% confidence interval (CI) 0.42–0.82, p‐value: 0.001). In conclusion, we find some evidence that common variants in mismatch repair genes may contribute to survival of patients with colorectal cancer. © 2008 Wiley‐Liss, Inc.     

Germline variation in NCF4, an innate immunity gene,is associated with an increased risk of colorectal cancer

Chronic inflammation has been implicated in the etiology of colorectal adenoma and cancer; however, few key inflammatory genes mediating this relationship have been identified. In this study, we investigated the association of germline variation in innate immunity genes in relation to the risk of colorectal neoplasia. Our study was based on the analysis of samples collected from the prostate, lung, colorectal and ovarian (PLCO) Cancer Screening Trial. We investigated the association between 196 tag single nucleotide polymorphisms (SNPs) in 20 key innate immunity genes with risk of advanced colorectal adenoma and cancer in 719 adenoma cases, 481 cancer cases and 719 controls. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CIs). After Bonferroni correction, the AG/GG genotype of rs5995355, which is upstream of NCF4, was associated with an increased risk of colorectal cancer (OR = 2.43, 95% CI = 1.73–3.39; p < 0.0001). NCF4 is part of the NAPDH complex, a key factor in biochemical pathways and the innate immune response. While not definitive, our analyses suggest that the variant allele does not affect expression of NCF4, but rather modulates activity of the NADPH complex. Additional studies on the functional consequences of rs5995355 in NCF4 may help to clarify the mechanistic link between inflammation and colorectal cancer.     

Genome‐wide association study and meta‐analysis in Northern European populations replicate multiple colorectal cancer risk loci

Genome‐wide association studies have been successful in elucidating the genetic basis of colorectal cancer (CRC), but there remains unexplained variability in genetic risk. To identify new risk variants and to confirm reported associations, we conducted a genome‐wide association study in 1,701 CRC cases and 14,082 cancer‐free controls from the Finnish population. A total of 9,068,015 genetic variants were imputed and tested, and 30 promising variants were studied in additional 11,647 cases and 12,356 controls of European ancestry. The previously reported association between the single‐nucleotide polymorphism (SNP) rs992157 (2q35) and CRC was independently replicated (p = 2.08 × 10⁻⁴; OR, 1.14; 95% CI, 1.06–1.23), and it was genome‐wide significant in combined analysis (p = 1.50 × 10⁻⁹; OR, 1.12; 95% CI, 1.08–1.16). Variants at 2q35, 6p21.2, 8q23.3, 8q24.21, 10q22.3, 10q24.2, 11q13.4, 11q23.1, 14q22.2, 15q13.3, 18q21.1, 20p12.3 and 20q13.33 were associated with CRC in the Finnish population (false discovery rate < 0.1), but new risk loci were not found. These results replicate the effects of multiple loci on the risk of CRC and identify shared risk alleles between the Finnish population isolate and outbred populations.     

Association of matrix metalloproteinase-2 and -9 promoter polymorphisms with colorectal cancer in Chinese

Matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) play an important role in cancer initiation, invasion, and metastasis. The aim of this study was to investigate whether common genetic variants in these two key MMPs are associated with the development and progression of colorectal cancer in a Chinese population. We detected the MMP-2-790T/G, -955A/C, -1575G/A, and MMP-9-1562 C/T polymorphisms in 126 colorectal cancer patients and matched normal controls by PCR-denaturing high-performance liquid chromatography (DHPLC) or PCR-restriction fragment length polymorphism (RFLP), respectively. We found that the G/G genotype in the MMP-2-1575G/A polymorphism was significantly increased in colorectal cancer patients than in the controls (odds ratio (OR), 1.96; 95% CI, 1.06-3.64). Colorectal cancers with G/G genotype were more common with serosa/adventitia layer involvement than those with G/A+A/A genotypes (P<0.05). However, no significant differences were observed in distribution of the MMP-2-790T/G, -955A/C, and MMP-9-1562 C/T polymorphisms or haplotype of MMP-2 SNPs between patients and controls. Our results suggest that the presence of -1575G allele in the MMP-2 promoter region may be of significance in the assessment of colorectal cancer risk and invasive potential.     

B7-H1基因rs4143815位点多态性与结直肠癌发病风险的关联研究

目的：B7-H1是肿瘤免疫治疗的一个靶点,位于其3'-非翻译区的rs4143815位点C/G多态性可影响其与miR-570的结合,进而影响B7-H1的表达。本研究旨在探讨B7-H1基因rs4143815位点多态性与结直肠癌发病风险的相关性。方法：采集215例结直肠癌患者和236例年龄性别匹配的健康对照人群外周静脉血,并收集手术切除结直肠癌和癌旁正常组织样本65例,直接测序法检测B7-H1基因rs4143815多态性,运用卡方检验分析B7-H1基因rs4143815多态性与结直肠癌发病风险的相关性;定量PCR检测B7-H1 mRNA表达。结果：结直肠癌和对照组中均检测到B7-H1基因rs4143815多态性的3种基因型,即CC、CG和GG基因型。结直肠癌和癌旁正常组织中均检测到B7-H1 mRNA的表达。与CC基因型相比,GG和CG/GG基因型显著增加了结直肠癌的发病风险[GG与CC相比：OR_调整=1.99,95% CI （1.19,3.34）,P=0.008;CG/GG与CC相比：OR_调整=1.58,95% CI （1.06,2.36） P=0.02]。与C等位基因相比,G等位基因显著增加了结直肠癌的发病风险[OR_调整=1.48,95% CI （1.14,1.93）,P=0.004]。B7-H1 mRNA在结直肠癌组织中的表达明显高于癌旁组织（P=0.02）,并且B7-H1基因rs4143815位点GG基因型携带者B7-H1 mRNA水平明显高于CC基因型携带者（P=0.03）。结论：B7-H1基因rs4143815位点GG基因型可能通过增加B7-H1 mRNA表达,进而增加了结直肠癌的发病风险。     

Genetic variants in the liver kinase B1‐AMP‐activated protein kinase pathway genes and pancreatic cancer risk

The liver kinase B1‐AMP‐activated protein kinase (LKB1‐AMPK) pathway has been identified as a new target for cancer therapy, because it controls the glucose and lipid metabolism in response to alterations in nutrients and intracellular energy levels. In the present study, we aimed to identify genetic variants of the LKB1‐AMPK pathway genes and their associations with pancreatic cancer (PanC) risk using 15 418 participants of European ancestry from two previously published PanC genome‐wide association studies. We found that six novel tagging single‐nucleotide polymorphisms (SNPs) (i.e, MAP2 rs35075084 T > deletion, PRKAG2 rs2727572 C > T and rs34852782 A > deletion, TP53 rs9895829 A > G, and RPTOR rs62068300 G > A and rs3751936 G > C) were significantly associated with an increased PanC risk. The multivariate logistic regression model incorporating the number of unfavorable genotypes (NUGs) with adjustment for age and sex showed that carriers with five to six NUGs had an increased PanC risk (odds ratio = 1.24, 95% confidence interval = 1.16‐1.32 and P < 0.0001), compared to those with zero to four NUGs. Subsequent expression quantitative trait loci (eQTL) analysis further revealed that these SNPs were associated with significantly altered mRNA expression levels either in 373 normal lymphoblastoid cell lines (TP53 SNP rs9895829, P < 0.05) or in whole blood cells of 369 normal donors from the genotype‐tissue expression project (GTEx) database [RPTOR SNP rs60268947 and rs28434589, both in high linkage disequilibrium (r² > 0.9) withRPTOR rs62068300, P < 0.001]. Collectively, our findings suggest that these novel SNPs in the LKB1‐AMPK pathway genes may modify susceptibility to PanC, possibly by influencing gene expression.     

Prospective study of colorectal cancer risk and physical activity, diabetes, blood glucose and BMI: exploring the hyperinsulinaemia hypothesis

A sedentary lifestyle, obesity, and a Westernized diet have been implicated in the aetiology of both colorectal cancer and non-insulin dependent diabetes mellitus, leading to the hypothesis that hyperinsulinaemia may promote colorectal cancer. We prospectively examined the association between colorectal cancer risk and factors related to insulin resistance and hyperinsulinaemia, including BMI, physical activity, diabetes mellitus, and blood glucose, in a cohort of 75 219 Norwegian men and women. Information on incident cases of colorectal cancer was made available from the Norwegian Cancer Registry. Reported P values are two-sided. During 12 years of follow up, 730 cases of colorectal cancer were registered. In men, but not in women, we found a negative association with leisure-time physical activity (P for trend = 0.002), with an age-adjusted RR for the highest versus the lowest category of activity of 0.54 (95% CI = 0.37-0.79). Women, but not men, with a history of diabetes were at increased risk of colorectal cancer (age-adjusted RR = 1.55; 95% CI = 1.04-2.31), as were women with non-fasting blood glucose > or = 8.0 mmol l(-1)(age-adjusted RR = 1.98; 95% CI = 1.31-2.98) compared with glucose <8.0 mmol l(-1). Overall, we found no association between BMI and risk of colorectal cancer. Additional adjustment including each of the main variables, marital status, and educational attainment did not materially change the results. We conclude that the inverse association between leisure-time physical activity and colorectal cancer in men, and the positive association between diabetes, blood glucose, and colorectal cancer in women, at least in part, support the hypothesis that insulin may act as a tumour promoter in colorectal carcinogenesis.