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1.  Trans-ethnic genome-wide association study of colorectal cancer identifies a new susceptibility locus in VTI1A 
Nature communications  2014;5:4613.
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.
PMCID: PMC4180879  PMID: 25105248
2.  Fine-mapping of genome-wide association study-identified risk loci for colorectal cancer in African Americans 
Human Molecular Genetics  2013;22(24):5048-5055.
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.
PMCID: PMC3836473  PMID: 23851122
3.  A pilot study comparing protein expression in different segments of the normal colon and rectum and in normal colon versus adenoma in patients with Lynch syndrome 
Lynch syndrome (LS) is a common inherited predisposition to colorectal cancer (CRC). In LS patients, CRC is predominantly located in the right colon, as opposed to sporadic CRC, which usually affects the left colon or rectum. Previous studies have demonstrated a clear distinction in gene expression between sporadic CRC and normal colon at different locations in the colorectum. However, little is known about LS gene expression profiles in different areas of the colorectum. Here, we compared the protein expression profiles for normal colorectal samples among different locations as well as between adenomas and matched normal tissue in LS.
Protein from 33 tissue samples (27 normal tissues and 6 adenomas) from 9 patients with LS was extracted for reverse-phase protein array (RPPA) analysis. The antibody panel used for RPPA included 109 key proteins involved in various cancer-related pathways. Cluster 3.0 was used for unsupervised and supervised clustering analysis.
IGF1R and COL6A1 were expressed significantly differently between the normal right and normal left colon (q<0.05); FN1, COL6A1, and IGF1R were expressed significantly differently between the normal right colon and normal rectum (q<0.05). In the adenomas and matched normal tissue, PEA-15 was the only protein with significantly different expression (q<0.05).
We found differences in protein expression between normal tissues from the right colon, left colon, and rectum as well as between adenomas and matched normal tissue. However, those differences should be further confirmed in a larger sample size.
PMCID: PMC3708474  PMID: 23604467
Lynch syndrome; Reverse phase protein array; PEA15; COL6A1; IGF1R; and FN1
4.  Prognostic Value of Single Nucleotide Polymorphisms of Candidate Genes Associated with Inflammation in Early Stage Breast Cancer 
To examine the role of germline genetic variations in inflammatory pathways as modifiers of time to recurrence (TTR) in patients with early stage breast cancer (BC), DNA from 997 early stage BC patients was genotyped for 53 tagging single nucleotide polymorphisms (SNPs) in 12 genes involved in inflammation. SNPs were analyzed separately for Caucasians versus African Americans and Hispanics. Cox proportional hazards models were used to evaluate the association between SNPs in the inflammatory genes and time to recurrence (TTR), adjusted for clinical and pathologic covariates. In univariable analyses of Caucasian women, the homozygous genotype of 12 SNPs, including 6 NFKB1 SNPs, 4 IL4 SNPs, and 2 IL13 SNPs, were significantly associated with a decrease in TTR compared with the heterozygous and/ or corresponding homozygous genotype (P <0.05). The significant NFKB1 and IL4 SNPs were in an area of high linkage disequilibrium (D'>0.8). After adjusting for stage, age, and treatment, carriage of the homozygous genotypes for NFKB1rs230532 and IL13rs1800925 were independently associated with a shorter TTR (P=0.001 and p=0.034, respectively). In African-American and Hispanic patients, expression of NFKB1rs3774932, TNFrs1799964, and IL4rs3024543 SNPs were associated with a shorter TTR in univariable model. Only NFKB1 rs3774932 (P=0.02) and IL4Rrs3024543 (P=0.03) had independent prognostic value in the multivariable model These data support the existence of host genetic susceptibility as a component in recurrence risk mediated by pro-inflammatory and immune factors, and suggest the potential for drugs which modify immune responses and inflammatory genes to improve prognosis in early stage BC.
PMCID: PMC3746974  PMID: 23529385
gene polymorphisms; inflammation; breast cancer
5.  Pleiotropic Associations of Risk Variants Identified for Other Cancers With Lung Cancer Risk: The PAGE and TRICL Consortia 
Genome-wide association studies have identified hundreds of genetic variants associated with specific cancers. A few of these risk regions have been associated with more than one cancer site; however, a systematic evaluation of the associations between risk variants for other cancers and lung cancer risk has yet to be performed.
We included 18023 patients with lung cancer and 60543 control subjects from two consortia, Population Architecture using Genomics and Epidemiology (PAGE) and Transdisciplinary Research in Cancer of the Lung (TRICL). We examined 165 single-nucleotide polymorphisms (SNPs) that were previously associated with at least one of 16 non–lung cancer sites. Study-specific logistic regression results underwent meta-analysis, and associations were also examined by race/ethnicity, histological cell type, sex, and smoking status. A Bonferroni-corrected P value of 2.5×10–5 was used to assign statistical significance.
The breast cancer SNP LSP1 rs3817198 was associated with an increased risk of lung cancer (odds ratio [OR] = 1.10; 95% confidence interval [CI] = 1.05 to 1.14; P = 2.8×10–6). This association was strongest for women with adenocarcinoma (P = 1.2×10–4) and not statistically significant in men (P = .14) with this cell type (P het by sex = .10). Two glioma risk variants, TERT rs2853676 and CDKN2BAS1 rs4977756, which are located in regions previously associated with lung cancer, were associated with increased risk of adenocarcinoma (OR = 1.16; 95% CI = 1.10 to 1.22; P = 1.1×10–8) and squamous cell carcinoma (OR = 1.13; CI = 1.07 to 1.19; P = 2.5×10–5), respectively.
Our findings demonstrate a novel pleiotropic association between the breast cancer LSP1 risk region marked by variant rs3817198 and lung cancer risk.
PMCID: PMC3982896  PMID: 24681604
6.  Genetic variants in the vitamin D pathway and breast cancer disease-free survival 
Carcinogenesis  2012;34(3):587-594.
Epidemiological studies have investigated the association between vitamin D pathway genes and breast cancer risk; however, little is known about the association between vitamin D pathway genes and breast cancer prognosis. In a retrospective cohort of 1029 patients with early-stage breast cancer, we analyzed the association between 106 tagging single nucleotide polymorphisms (SNPs) in eight vitamin D pathway genes and breast cancer disease-free survival (DFS) using Cox regression analysis adjusted for known prognostic variables. Using a false discovery rate of 10%, six intronic SNPs were significantly associated with poorer DFS: retinoid-X receptor alpha (RXRA) SNPs (rs881658, rs11185659, rs10881583, rs881657 and rs7864987) and plasminogen activator and urokinase receptor (PLAUR) SNP (rs4251864). Treatment received (no systemic therapy, hormone therapy alone or chemotherapy) was an effect modifier of the RXRA SNPs association with DFS (P < 0.05); therefore, we stratified further analysis by treatment group. Among patients who did not receive systemic therapy, RXRA SNP [rs10881583 (P = 0.02)] was associated with poorer DFS, and among patients who received chemotherapy, RXRA SNPs (rs881658, rs11185659, rs10881583, rs881657 and rs7864987) were associated with poorer DFS (P < 0.001 for all SNPs). However, RXRA SNPs: rs10881583 (P < 0.001) and rs881657 (P = 0.02) were associated with improved DFS in patients treated with hormone therapy alone. Our results suggest that SNPs in the RXRA and PLAUR genes in the vitamin D pathway may contribute to breast cancer DFS. In particular, SNPs in RXRA may predict for poorer or improved DFS in patients, according to type of systemic treatment received. If validated, these markers could be used for risk stratification of breast cancer patients.
PMCID: PMC3581599  PMID: 23180655
7.  Cell cycle–related genes as modifiers of age of onset of colorectal cancer in Lynch syndrome: a large-scale study in non-Hispanic white patients 
Carcinogenesis  2012;34(2):299-306.
Heterogeneity in age of onset of colorectal cancer in individuals with mutations in DNA mismatch repair genes (Lynch syndrome) suggests the influence of other lifestyle and genetic modifiers. We hypothesized that genes regulating the cell cycle influence the observed heterogeneity as cell cycle–related genes respond to DNA damage by arresting the cell cycle to provide time for repair and induce transcription of genes that facilitate repair. We examined the association of 1456 single nucleotide polymorphisms (SNPs) in 128 cell cycle–related genes and 31 DNA repair–related genes in 485 non-Hispanic white participants with Lynch syndrome to determine whether there are SNPs associated with age of onset of colorectal cancer. Genotyping was performed on an Illumina GoldenGate platform, and data were analyzed using Kaplan–Meier survival analysis, Cox regression analysis and classification and regression tree (CART) methods. Ten SNPs were independently significant in a multivariable Cox proportional hazards regression model after correcting for multiple comparisons (P < 5×10–4). Furthermore, risk modeling using CART analysis defined combinations of genotypes for these SNPs with which subjects could be classified into low-risk, moderate-risk and high-risk groups that had median ages of colorectal cancer onset of 63, 50 and 42 years, respectively. The age-associated risk of colorectal cancer in the high-risk group was more than four times the risk in the low-risk group (hazard ratio = 4.67, 95% CI = 3.16–6.92). The additional genetic markers identified may help in refining risk groups for more tailored screening and follow-up of non-Hispanic white patients with Lynch syndrome.
PMCID: PMC3564440  PMID: 23125224
8.  Cancer spectrum in DNA mismatch repair gene mutation carriers: results from a hospital based Lynch syndrome registry 
Familial cancer  2012;11(3):441-447.
The spectrum of cancers seen in a hospital based Lynch syndrome registry of mismatch repair gene mutation carriers was examined to determine the distribution of cancers and examine excess cancer risk. Overall there were 504 cancers recorded in 368 mutation carriers from 176 families. These included 236 (46.8 %) colorectal and 268 (53.2 %) extracolonic cancers. MLH1 mutation carriers had a higher frequency of colorectal cancers whereas MSH2, MSH6 and PMS2 mutation carriers had more extracolonic cancers although these differences were not statistically significant. Men had fewer extracolonic cancers than colorectal (45.3 vs. 54.7 %), whereas women had more extracolonic than colorectal cancers (59.0 vs. 41.0 %). The mean age at diagnosis overall for extracolonic cancers was older than for colorectal, 49.1 versus 44.8 years (P ≤ 0.001). As expected, the index cancer was colorectal in 58.1 % of patients and among the extracolonic index cancers, endometrial was the most common (13.8 %). A significant number of non-Lynch syndrome index cancers were recorded including breast (n = 5) prostate (n = 3), thyroid (n = 3), cervix (n = 3), melanoma (n = 3), and 1 case each of thymoma, sinus cavity, and adenocarcinoma of the lung. However, standardized incidence ratios calculated to assess excess cancer risk showed that only those cancers known to be associated with Lynch syndrome were significant in our sample. We found that Lynch syndrome patients can often present with cancers that are not considered part of Lynch syndrome. This has clinical relevance both for diagnosis of Lynch syndrome and surveillance for cancers of different sites during follow-up of these patients.
PMCID: PMC3475767  PMID: 22714864
Lynch syndrome cancers; Colorectal; Extracolonic; Index cancer
9.  Novel genetic variants in the chromosome 5p15.33 region associate with lung cancer risk 
Carcinogenesis  2011;32(10):1493-1499.
Chromosome 5p15.33 has been identified by genome-wide association studies as one of the regions that associate with lung cancer risk. A few single-nucleotide polymorphisms (SNPs) in the telomerase reverse transcriptase (TERT) and cleft lip and palate transmembrane 1-like (CLPTM1L) genes located in this region have shown consistent associations. We performed dense genotyping of SNPs in this region to refine the previously reported association signals for lung cancer risk. Two hundred and fifteen SNPs were genotyped on an Illumina iSelect panel, in a hospital-based case–control study of 1681 lung cancer cases and 1235 unaffected controls. Association was tested using unconditional logistic regression, while adjusting for age, sex and pack-years smoked. Furthermore, since many of the SNPs were in linkage disequilibrium (LD), haplotype blocks were constructed, from which tagging SNPs at an r2 threshold of ≥0.95 were included in a stepwise forward selection logistic regression model. Of the 215 SNPs, 69 were significant at P < 0.05 in univariate analysis; of these, 35 SNPs meeting the r2 threshold were included in the multiple logistic regression model. Two SNPs, rs370348 (odds ratio = 0.76, P = 1.6 × 10−6) and rs4975538 (odds ratio = 1.18, P = 0.005), significantly associated with risk in the overall sample. Among ever smokers, rs4975615 (odds ratio = 0.75, P = 1.2 × 10−4) and rs4975538 (odds ratio = 1.26, P = 0.002) were significant, whereas among never-smokers, rs451360 (odds ratio = 0.62, P = 7.6 × 10−5) was significant. We refined the consistent association signal in this region, allowing for the considerable LD between SNPs and identified four novel SNPs that were independently and significantly associated with lung cancer risk. Results of these analyses strongly suggest effects on risk from several loci in the TERT/CLPTM1L region.
PMCID: PMC3179422  PMID: 21771723
10.  Influence of common genetic variation on lung cancer risk: meta-analysis of 14 900 cases and 29 485 controls 
Human Molecular Genetics  2012;21(22):4980-4995.
Recent genome-wide association studies (GWASs) have identified common genetic variants at 5p15.33, 6p21–6p22 and 15q25.1 associated with lung cancer risk. Several other genetic regions including variants of CHEK2 (22q12), TP53BP1 (15q15) and RAD52 (12p13) have been demonstrated to influence lung cancer risk in candidate- or pathway-based analyses. To identify novel risk variants for lung cancer, we performed a meta-analysis of 16 GWASs, totaling 14 900 cases and 29 485 controls of European descent. Our data provided increased support for previously identified risk loci at 5p15 (P = 7.2 × 10−16), 6p21 (P = 2.3 × 10−14) and 15q25 (P = 2.2 × 10−63). Furthermore, we demonstrated histology-specific effects for 5p15, 6p21 and 12p13 loci but not for the 15q25 region. Subgroup analysis also identified a novel disease locus for squamous cell carcinoma at 9p21 (CDKN2A/p16INK4A/p14ARF/CDKN2B/p15INK4B/ANRIL; rs1333040, P = 3.0 × 10−7) which was replicated in a series of 5415 Han Chinese (P = 0.03; combined analysis, P = 2.3 × 10−8). This large analysis provides additional evidence for the role of inherited genetic susceptibility to lung cancer and insight into biological differences in the development of the different histological types of lung cancer.
PMCID: PMC3607485  PMID: 22899653
11.  Susceptibility locus for lung cancer at 15q25.1 is not associated with risk of pancreatic cancer 
Pancreas  2011;40(6):872-875.
Four genome-wide association (GWA) studies have found that variation in a region of strong linkage disequilibrium on the long arm of chromosome 15 (15q24-25.1), containing nicotinic acetylcholine receptor genes, contributes to lung cancer risk. Since cigarette smoking is a major risk factor for developing both lung cancer and pancreatic cancer, we hypothesized that variation in this region may also modify individual susceptibility to pancreatic cancer.
We conducted a case-control study of 532 patients with pathologically confirmed pancreatic adenocarcinoma and 1046 age-, sex-, ethnicity-, and smoking behavior-matched cancer-free controls.
We found that the two risk single nucleotide polymorphisms (SNPs) reported in the lung cancer GWA studies, rs8034191: A>G and rs1051730: G>A, located in this 15q24-25.1 region, were not associated with risk of pancreatic cancer.
The results of our study suggest that the two SNPs at 15q25.1 do not modify pancreatic cancer risk.
PMCID: PMC3138891  PMID: 21697764
nicotinic acetylcholine receptor; single nucleotide polymorphisms; pancreatic cancer; case-control study and chromosome 15
12.  Interactions between cigarette smoking and selected polymorphisms in xenobiotic metabolizing enzymes in risk for colorectal cancer: a case-only analysis 
Molecular carcinogenesis  2010;49(11):974-980.
The metabolism of xenobiotics is complex and involves multiple steps and multiple enzymes. Genetic variation in the genes encoding these enzymes as well as the level of exposure to the substrates of these enzymes could alter metabolism and clearance of potential carcinogens and thus alter cancer susceptibility. This study examined interaction effect between smoking and two single nucleotide polymorphisms (SNPs)—CYP1A1 c.1384A>G (p.Ile462Val) and EPHX1 c.337T>C (p.Tyr113His)—in modulating colorectal cancer (CRC) risk. The SNPs were selected a priori based on functional significance.
In a case-only analysis, unconditional logistic regression was used to examine the associations between smoking and each SNP and between the two SNPs in 786 patients with nonfamilial CRC.
There was significant multiplicative interaction for CRC risk between smoking and EPHX1 c.337T>C (odds ratio [OR] = 1.37, 95% confidence interval [CI] = 1.03–1.81, P = 0.03), particularly among smokers with a history of greater than 20 pack-years of smoking (OR = 1.52, 95% CI = 1.07–2.16, P = 0.02). In addition, there was gene-gene interaction between EPHX1 c.337T>C and CYP1A1 c.1384A>G (OR = 1.61, 95% CI = 1.02–2.55, P = 0.04).
Smokers with any variant allele of EPHX1 were at increased risk for CRC, as were individuals with any variant allele of CYP1A1 together with any variant allele of EPHX1. Thus, the study of gene-environment and gene-gene interactions may help to identify high-risk subgroups that can be targeted for intensive smoking cessation and CRC screening interventions.
PMCID: PMC3034292  PMID: 20886582
Genetic epistasis; Microsomal Epoxide Hydrolase; Cytochrome P-450 CYP1A1; gene-environment interaction
14.  Smoking and colorectal cancer in Lynch syndrome: Results from the Colon Cancer Family Registry and The University of Texas M. D. Anderson Cancer Center 
Lynch syndrome family members with inherited germline mutations in DNA mismatch repair (MMR) genes have a high risk of colorectal cancer (CRC) and cases typically have tumors that exhibit a high level of microsatellite instability (MSI). There is some evidence that smoking is a risk factor for CRCs with high MSI, but the association of smoking with CRC among those with Lynch syndrome is unknown.
Experimental Design
A multicentered retrospective cohort of 752 carriers of pathogenic MMR gene mutations was analyzed, using a weighted Cox regression analysis, adjusting for sex, ascertainment source, the specific mutated gene, year of birth, and familial clustering.
Compared with never smokers, current smokers had a significantly increased CRC risk (adjusted hazard ratio [HR] = 1.62; 95% CI, 1.01 – 2.57) and former smokers who had quit smoking for 2 or more years were at decreased risk (HR = 0.53; 95% CI, 0.35 – 0.82). CRC risk did not vary according to age at starting. However, light smoking (<10 cigarettes per day) and shorter duration of smoking (<10 years) were associated with decreased CRC risk (HR = 0.51; 95% CI, 0.29 – 0.91 and HR = 0.52; 95% CI, 0.30 - 0.89 respectively). For former smokers, CRC risk decreased with years since quitting (P trend <0.01).
People with Lynch syndrome may be at increased risk of CRC if they smoke regularly. Although our data suggest that former smokers, short-term and light smokers are at decreased CRC risk, these findings need further confirmation, preferably using prospective designs.
PMCID: PMC2822883  PMID: 20145170
15.  Genetic variation in genes for the xenobiotic-metabolizing enzymes CYP1A1, EPHX1, GSTM1, GSTT1 and GSTP1 and susceptibility to colorectal cancer in Lynch syndrome 
Individuals with Lynch syndrome are predisposed to cancer due to an inherited DNA mismatch repair gene mutation. However, there is significant variability observed in disease expression, likely due to the influence of other environmental, lifestyle, or genetic factors. Polymorphisms in genes encoding xenobiotic-metabolizing enzymes may modify cancer risk by influencing the metabolism and clearance of potential carcinogens from the body. In this retrospective analysis, we examined key candidate gene polymorphisms in CYP1A1, EPHX1, GSTT1, GSTM1, and GSTP1 as modifiers of age at onset of colorectal cancer among 257 individuals with Lynch syndrome. We found that subjects heterozygous for CYP1A1 I462V (c.1384A>G) developed colorectal cancer 4 years earlier than those with the homozygous wild-type genotype (median ages 39 and 43 years, respectively; log-rank test P = 0.018). Furthermore, being heterozygous for the CYP1A1 polymorphisms, I462V and Msp1 (g.6235T>C), was associated with an increased risk for developing colorectal cancer [adjusted hazard ratio for AG relative to AA = 1.78, 95% CI = 1.16–2.74, P = 0.008; and hazard ratio for TC relative to TT = 1.53, 95% CI = 1.06–2.22, P = 0.02]. Since homozygous variants for both CYP1A1 polymorphisms were rare, risk estimates were imprecise. None of the other gene polymorphisms examined were associated with an earlier onset age for colorectal cancer. Our results suggest that the I462V and Msp1 polymorphisms in CYP1A1 may be an additional susceptibility factor for disease expression in Lynch syndrome since they modify the age of colorectal cancer onset by up to 4 years.
PMCID: PMC3028532  PMID: 18768509
xenobiotic metabolism; polymorphisms; Lynch syndrome; colorectal cancer; age at onset

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