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1.  A Pooled Analysis of Alcohol Consumption and Risk of Multiple Myeloma in the International Multiple Myeloma Consortium 
Recent findings suggest that alcohol consumption may reduce risk of multiple myeloma (MM).
To better understand this relationship, we conducted an analysis of six case-control studies participating in the International Multiple Myeloma Consortium (1,567 cases, 7,296 controls). Summary odds ratios (ORs) and 95% confidence intervals (CI) relating different measures of alcohol consumption and MM risk were computed by unconditional logistic regression with adjustment for age, race, and study center.
Cases were significantly less likely than controls to report ever drinking alcohol (men: OR 0.72, 95% CI 0.59-0.89, women: OR 0.81, 0.68-0.95). The inverse association with MM was stronger when comparing current to never drinkers (men: OR=0.57, 95% CI 0.45-0.72, women: OR=0.55, 95% CI 0.45-0.68), but null among former drinkers. We did not observe an exposure-response relationship with increasing alcohol frequency, duration or cumulative lifetime consumption. Additional adjustment for body mass index, education, or smoking did not affect our results; and the patterns of association were similar for each type of alcohol beverage examined.
Our study is, to our knowledge, the largest of its kind to date, and our findings suggest that alcohol consumption may be associated with reduced risk of MM.
Prospective studies, especially those conducted as pooled analyses with large sample sizes, are needed to confirm our findings and further explore whether alcohol consumption provides true biologic protection against this rare, highly fatal malignancy.
PMCID: PMC3769449  PMID: 23964064
2.  Mapping of the IRF8 gene identifies a 3’ UTR variant associated with risk of chronic lymphocytic leukemia but not other common non-Hodgkin lymphoma subtypes 
Our genome-wide association study (GWAS) of chronic lymphocytic leukemia (CLL) identified 4 highly-correlated intronic variants within the IRF8 gene that were associated with CLL. These results were further supported by a recent meta-analysis of our GWAS with two other GWAS of CLL, supporting the IRF8 gene as a strong candidate for CLL risk.
To refine the genetic association of CLL risk, we performed Sanger sequencing of IRF8 in 94 CLL cases and 96 controls. We then performed fine-mapping by genotyping 39 variants (of which 10 were identified from sequencing) in 745 CLL cases and 1521 controls. We also assessed these associations with risk of other non-Hodgkin lymphoma (NHL) subtypes.
The strongest association with CLL risk was observed with a common SNP located within the 3’ UTR of IRF8 (rs1044873, log additive odds ratio = 0.7, P=1.81×10−6). This SNP was not associated with the other NHL subtypes (all P>0.05).
We provide evidence that rs1044873 in the IRF8 gene accounts for the initial GWAS signal for CLL risk. This association appears to be unique to CLL with little support for association with other common NHL subtypes. Future work is needed to assess functional role of IRF8 in CLL etiology.
These data provide support that a functional variant within the 3’ UTR of IRF8 may be driving the GWAS signal seen on 16q24.1 for CLL risk.
PMCID: PMC3596428  PMID: 23307532
CLL; NHL; SNPs; IRF8; risk locus
3.  A role for XRCC2 gene polymorphisms in breast cancer risk and survival 
Journal of medical genetics  2011;48(7):477-484.
The XRCC2 gene is a key mediator in the homologous recombination repair of DNA double strand breaks. We hypothesised that inherited variants in the XRCC2 gene might also affect susceptibility to, and survival from, breast cancer.
We genotyped 12 XRCC2 tagging SNPs in 1,131 breast cancer cases and 1,148 controls from the Sheffield Breast Cancer Study (SBCS), and examined their associations with breast cancer risk and survival by estimating odds ratios (ORs) and hazard ratios (HRs), and their corresponding 95% confidence intervals (CIs). Positive findings were further investigated in 860 cases and 869 controls from the Utah Breast Cancer Study (UBCS) and jointly analysed together with available published data for breast cancer risk. The survival findings were further confirmed in studies (8,074 cases) from the Breast Cancer Association Consortium (BCAC).
The most significant association with breast cancer risk in the SBCS dataset was the XRCC2 rs3218408 SNP (recessive model p=2.3×10−4, MAF=0.23). This SNP yielded an ORrec (95% CI) of 1.64 (1.25–2.16) in a two-site analysis of SBCS and UBCS, and a meta-ORrec (95% CI) of 1.33 (1.12–1.57) when all published data were included. This SNP may mark a rare risk haplotype carried by 2 in 1000 of the control population. Furthermore, the XRCC2 coding R188H SNP (rs3218536, MAF=0.08) was significantly associated with poor survival, with an increased per-allele HR (95% CI) of 1.58 (1.01–2.49) in a multivariate analysis. This effect was still evident in a pooled meta-analysis of 8,781 breast cancer patients from the BCAC [HR (95% CI) of 1.19 (1.05–1.36), p=0.01].
Our findings suggest that XRCC2 SNPs may influence breast cancer risk and survival.
PMCID: PMC3932658  PMID: 21632523
Single nucleotide polymorphism; XRCC2; breast cancer risk; breast cancer survival
4.  Genome-wide Association Study Identifies Multiple Risk Loci for Chronic Lymphocytic Leukemia 
Berndt, Sonja I. | Skibola, Christine F. | Joseph, Vijai | Camp, Nicola J. | Nieters, Alexandra | Wang, Zhaoming | Cozen, Wendy | Monnereau, Alain | Wang, Sophia S. | Kelly, Rachel S. | Lan, Qing | Teras, Lauren R. | Chatterjee, Nilanjan | Chung, Charles C. | Yeager, Meredith | Brooks-Wilson, Angela R. | Hartge, Patricia | Purdue, Mark P. | Birmann, Brenda M. | Armstrong, Bruce K. | Cocco, Pierluigi | Zhang, Yawei | Severi, Gianluca | Zeleniuch-Jacquotte, Anne | Lawrence, Charles | Burdette, Laurie | Yuenger, Jeffrey | Hutchinson, Amy | Jacobs, Kevin B. | Call, Timothy G. | Shanafelt, Tait D. | Novak, Anne J. | Kay, Neil E. | Liebow, Mark | Wang, Alice H. | Smedby, Karin E | Adami, Hans-Olov | Melbye, Mads | Glimelius, Bengt | Chang, Ellen T. | Glenn, Martha | Curtin, Karen | Cannon-Albright, Lisa A. | Jones, Brandt | Diver, W. Ryan | Link, Brian K. | Weiner, George J. | Conde, Lucia | Bracci, Paige M. | Riby, Jacques | Holly, Elizabeth A. | Smith, Martyn T. | Jackson, Rebecca D. | Tinker, Lesley F. | Benavente, Yolanda | Becker, Nikolaus | Boffetta, Paolo | Brennan, Paul | Foretova, Lenka | Maynadie, Marc | McKay, James | Staines, Anthony | Rabe, Kari G. | Achenbach, Sara J. | Vachon, Celine M. | Goldin, Lynn R | Strom, Sara S. | Lanasa, Mark C. | Spector, Logan G. | Leis, Jose F. | Cunningham, Julie M. | Weinberg, J. Brice | Morrison, Vicki A. | Caporaso, Neil E. | Norman, Aaron D. | Linet, Martha S. | De Roos, Anneclaire J. | Morton, Lindsay M. | Severson, Richard K. | Riboli, Elio | Vineis, Paolo | Kaaks, Rudolph | Trichopoulos, Dimitrios | Masala, Giovanna | Weiderpass, Elisabete | Chirlaque, María-Dolores | Vermeulen, Roel C H | Travis, Ruth C. | Giles, Graham G. | Albanes, Demetrius | Virtamo, Jarmo | Weinstein, Stephanie | Clavel, Jacqueline | Zheng, Tongzhang | Holford, Theodore R | Offit, Kenneth | Zelenetz, Andrew | Klein, Robert J. | Spinelli, John J. | Bertrand, Kimberly A. | Laden, Francine | Giovannucci, Edward | Kraft, Peter | Kricker, Anne | Turner, Jenny | Vajdic, Claire M. | Ennas, Maria Grazia | Ferri, Giovanni M. | Miligi, Lucia | Liang, Liming | Sampson, Joshua | Crouch, Simon | Park, Ju-hyun | North, Kari E. | Cox, Angela | Snowden, John A. | Wright, Josh | Carracedo, Angel | Lopez-Otin, Carlos | Bea, Silvia | Salaverria, Itziar | Martin, David | Campo, Elias | Fraumeni, Joseph F. | de Sanjose, Silvia | Hjalgrim, Henrik | Cerhan, James R. | Chanock, Stephen J. | Rothman, Nathaniel | Slager, Susan L.
Nature genetics  2013;45(8):868-876.
PMCID: PMC3729927  PMID: 23770605
5.  Shared Genomic Segment Analysis: The Power to Find Rare Disease Variants 
Annals of human genetics  2012;76(6):10.1111/j.1469-1809.2012.00728.x.
Shared genomic segment (SGS) analysis is a method that uses dense SNP genotyping in high-risk pedigrees to identify regions of sharing between cases. Here, we illustrate the power of SGS to identify dominant rare risk variants. Using simulated pedigrees, we consider 12 disease models based on disease prevalence, minor allele frequency, and penetrance to represent disease loci that explain 0.2% to 99.8% of total disease risk. Pedigrees were required to contain ≥15 meioses between all cases and to be high-risk based on significant excess of disease (p<0.001 or p<0.00001). Across these scenarios the power for a single pedigree ranged widely. Nonetheless, fewer than 10 pedigrees was sufficient for excellent power in the majority of the models. Power increased with the risk attributable to the disease locus, penetrance, and the excess of disease in the pedigree. Sharing allowing for one sporadic case was uniformly more powerful than sharing using all cases. Further, we do a SGS analysis using a large Attenuated Familial Adenomatous Polyposis pedigree and identified a 1.96 Mb region containing the known causal APC gene with genome-wide significance (p<5×10−7). SGS is a powerful method for detecting rare variants and offers a valuable complement to GWAS and linkage analysis.
PMCID: PMC3879794  PMID: 22989048
6.  A Family-Based Paradigm to Identify Candidate Chromosomal Regions for Isolated Congenital Diaphragmatic Hernia 
Congenital diaphragmatic hernia (CDH) is a developmental defect of the diaphragm that causes high newborn mortality. Isolated or non-syndromic CDH is considered a multifactorial disease, with strong evidence implicating genetic factors. As low heritability has been reported in isolated CDH, family-based genetic methods have yet to identify the genetic factors associated with the defect. Using the Utah Population Database, we identified distantly related patients from several extended families with a high incidence of isolated CDH. Using high-density genotyping, seven patients were analyzed by homozygosity exclusion rare allele mapping (HERAM) and phased haplotype sharing (HapShare), two methods we developed to map shared chromosome regions. Our patient cohort shared three regions not previously associated with CDH, i.e. 2q11.2-q12.1, 4p13 and 7q11.2, and two regions previously involved in CDH, i.e. 8p23.1 and 15q26.2. The latter regions contain GATA4 and NR2F2, two genes implicated in diaphragm formation in mice. Interestingly, three patients shared the 8p23.1 locus and one of them also harbored the 15q26.2 segment. No coding variants were identified in GATA4 or NR2F2, but a rare shared variant was found in intron 1 of GATA4. This work shows the role of heritability in isolated CDH. Our family-based strategy uncovers new chromosomal regions possibly associated with disease, and suggests that non-coding variants of GATA4 and NR2F2 may contribute to the development of isolated CDH. This approach could speed up the discovery of the genes and regulatory elements causing multifactorial diseases, such as isolated CDH.
PMCID: PMC3507422  PMID: 23165927
congenital diaphragmatic hernia; Utah population database; shared segment analysis; GATA4; NR2F2
7.  Common variants within 6p21.31 locus are associated with chronic lymphocytic leukaemia and potentially other non-Hodgkin lymphoma subtypes 
British journal of haematology  2012;159(5):572-576.
A recent meta-analysis of three genome-wide association studies of chronic lymphocytic leukaemia (CLL) identified two common variants at the 6p21.31 locus that are associated with CLL risk. To verify and further explore the association of these variants with other non-Hodgkin lymphoma (NHL) subtypes, we genotyped 1196 CLL cases, 1699 NHL cases, and 2410 controls. We found significant associations between the 6p21.31 variants and CLL risk (rs210134: P=0.01; rs210142: P=6.8×10−3). These variants also showed a trend towards association with some of the other NHL subtypes. Our results validate the prior work and support specific genetic pathways for risk among NHL subtypes.
PMCID: PMC3614403  PMID: 23025533
CLL; NHL; SNPs; BAK1; risk locus
8.  Compelling Evidence for a Prostate Cancer Gene at 22q12.3 by the International Consortium for Prostate Cancer Genetics 
Human molecular genetics  2007;16(11):1271-1278.
Previously, an analysis of 14 extended, high-risk Utah pedigrees localized the chromosome 22q linkage region to 3.2 Mb at 22q12.3-13.1 (flanked on each side by three recombinants), which contained 31 annotated genes. In this large, multi-centered, collaborative study, we performed statistical recombinant mapping in fifty-four pedigrees selected to be informative for recombinant mapping from nine member groups of the International Consortium for Prostate Cancer Genetics (ICPCG). These 54 pedigrees included the 14 extended pedigrees from Utah and 40 pedigrees from eight other ICPCG member groups. The additional 40 pedigrees were selected from a total pool of 1,213 such that each pedigree was required to both contain at least four prostate cancer (PRCA) cases and exhibit evidence for linkage to the chromosome 22q region. The recombinant events in these 40 independent pedigrees confirmed the previously proposed region. Further, when all 54 pedigrees were considered, the three-recombinant consensus region was narrowed by more than a megabase to 2.2 Mb at chromosome 22q12.3 flanked by D22S281 and D22S683. This narrower region eliminated 20 annotated genes from that previously proposed, leaving only eleven genes. This region at 22q12.3 is the most consistently identified and smallest linkage region for PRCA. This collaborative study by the ICPCG illustrates the value of consortium efforts and the continued utility of linkage analysis using informative pedigrees to localize genes for complex diseases.
PMCID: PMC2653215  PMID: 17478474
9.  A comprehensive study of polymorphisms in the ABCB1, ABCC2, ABCG2, NR1I2 genes and lymphoma risk 
Owing to their role in controlling the efflux of toxic compounds, transporters are central players in the process of detoxification and elimination of xenobiotics, which in turn is related to cancer risk. Among these transporters, ATP-binding cassette B1/multidrug resistance 1 (ABCB1/MDR1), ABCC2/multidrug resistance protein 2 (MRP2), and ABCG2/breast cancer resistance protein (BCRP) affect susceptibility to many hematopoietic malignancies. The maintenance of regulated expression of these transporters is governed through the activation of intracellular “xenosensors” like the nuclear receptor 1I2/pregnane X receptor (NR1I2/PXR). SNPs in genes encoding these regulators have also been implicated in the risk of several cancers. Using a tagging approach, we tested the hypothesis that common polymorphisms in the transporter genes ABCB1, ABCC2, ABCG2, and the regulator gene NR1I2 could be implicated in lymphoma risk. We selected 68 SNPs in the 4 genes, and we genotyped them in 1,481 lymphoma cases and 1,491 controls of the European cases-control study (EpiLymph) using the Illumina™ GoldenGate assay technology.Carriers of the SNP rs6857600 minor allele in ABCG2, was associated with a decrease in risk of B-cell lymphoma (B-NHL) overall (p<0.001). Furthermore, a decreased risk of chronic lymphocytic leukemia (CLL) was associated with the ABCG2 rs2231142 variant (p=0.0004), which could be replicated in an independent population. These results suggest a role for this gene in B-NHL susceptibility, especially for CLL.
PMCID: PMC3432449  PMID: 21918980
Lymphoma; multidrug resistance 1 (MDR1); multidrug resistance protein 2 (MRP2); breast cancer resistance protein (BCRP); pregnane X receptor (PXR)
10.  Associations of ATR and CHEK1 Single Nucleotide Polymorphisms with Breast Cancer 
PLoS ONE  2013;8(7):e68578.
DNA damage and replication checkpoints mediated by the ATR-CHEK1 pathway are key to the maintenance of genome stability, and both ATR and CHEK1 have been proposed as potential breast cancer susceptibility genes. Many novel variants recently identified by the large resequencing projects have not yet been thoroughly tested in genome-wide association studies for breast cancer susceptibility. We therefore used a tagging SNP (tagSNP) approach based on recent SNP data available from the 1000 genomes projects, to investigate the roles of ATR and CHEK1 in breast cancer risk and survival. ATR and CHEK1 tagSNPs were genotyped in the Sheffield Breast Cancer Study (SBCS; 1011 cases and 1024 controls) using Illumina GoldenGate assays. Untyped SNPs were imputed using IMPUTE2, and associations between genotype and breast cancer risk and survival were evaluated using logistic and Cox proportional hazard regression models respectively on a per allele basis. Significant associations were further examined in a meta-analysis of published data or confirmed in the Utah Breast Cancer Study (UBCS). The most significant associations for breast cancer risk in SBCS came from rs6805118 in ATR (p=7.6x10-5) and rs2155388 in CHEK1 (p=3.1x10-6), but neither remained significant after meta-analysis with other studies. However, meta-analysis of published data revealed a weak association between the ATR SNP rs1802904 (minor allele frequency is 12%) and breast cancer risk, with a summary odds ratio (confidence interval) of 0.90 (0.83-0.98) [p=0.0185] for the minor allele. Further replication of this SNP in larger studies is warranted since it is located in the target region of 2 microRNAs. No evidence of any survival effects of ATR or CHEK1 SNPs were identified. We conclude that common alleles of ATR and CHEK1 are not implicated in breast cancer risk or survival, but we cannot exclude effects of rare alleles and of common alleles with very small effect sizes.
PMCID: PMC3700940  PMID: 23844225
11.  Chromosomes 4 and 8 Implicated in a Genome Wide SNP Linkage Scan of 762 Prostate Cancer Families Collected by the ICPCG 
The Prostate  2011;72(4):410-426.
In spite of intensive efforts, understanding of the genetic aspects of familial prostate cancer remains largely incomplete. In a previous microsatellite-based linkage scan of 1233 prostate cancer (PC) families, we identified suggestive evidence for linkage (i.e. LOD≥1.86) at 5q12, 15q11, 17q21, 22q12, and two loci on 8p, with additional regions implicated in subsets of families defined by age at diagnosis, disease aggressiveness, or number of affected members.
In an attempt to replicate these findings and increase linkage resolution, we used the Illumina 6000 SNP linkage panel to perform a genome-wide linkage scan of an independent set of 762 multiplex PC families, collected by 11 ICPCG groups.
Of the regions identified previously, modest evidence of replication was observed only on the short arm of chromosome 8, where HLOD scores of 1.63 and 3.60 were observed in the complete set of families and families with young average age at diagnosis, respectively. The most significant linkage signals found in the complete set of families were observed across a broad, 37 cM interval on 4q13-25, with LOD scores ranging from 2.02 to 2.62, increasing to 4.50 in families with older average age at diagnosis. In families with multiple cases presenting with more aggressive disease, LOD scores over 3.0 were observed at 8q24 in the vicinity of previously identified common PC risk variants, as well as MYC, an important gene in PC biology.
These results will be useful in prioritizing future susceptibility gene discovery efforts in this common cancer.
PMCID: PMC3568777  PMID: 21748754
12.  Validation of prostate cancer risk-related loci identified from genome-wide association studies using family-based association analysis: evidence from the International Consortium for Prostate Cancer Genetics (ICPCG) 
Human genetics  2011;131(7):1095-1103.
Multiple prostate cancer (PCa) risk-related loci have been discovered by genome-wide association studies (GWAS) based on case–control designs. However, GWAS findings may be confounded by population stratification if cases and controls are inadvertently drawn from different genetic backgrounds. In addition, since these loci were identified in cases with predominantly sporadic disease, little is known about their relationships with hereditary prostate cancer (HPC). The association between seventeen reported PCa susceptibility loci was evaluated with a family-based association test using 1,979 hereditary PCa families of European descent collected by members of the International Consortium for Prostate Cancer Genetics, with a total of 5,730 affected men. The risk alleles for 8 of the 17 loci were significantly over-transmitted from parents to affected offspring, including SNPs residing in 8q24 (regions 1, 2 and 3), 10q11, 11q13, 17q12 (region 1), 17q24 and Xp11. In subgroup analyses, three loci, at 8q24 (regions 1 and 2) plus 17q12, were significantly over-transmitted in hereditary PCa families with five or more affected members, while loci at 3p12, 8q24 (region 2), 11q13, 17q12 (region 1), 17q24 and Xp11 were significantly over-transmitted in HPC families with an average age of diagnosis at 65 years or less. Our results indicate that at least a subset of PCa risk-related loci identified by case–control GWAS are also associated with disease risk in HPC families.
PMCID: PMC3535428  PMID: 22198737
13.  Pairwise shared genomic segment analysis in three Utah high-risk breast cancer pedigrees 
BMC Genomics  2012;13:676.
We applied a new weighted pairwise shared genomic segment (pSGS) analysis for susceptibility gene localization to high-density genomewide SNP data in three extended high-risk breast cancer pedigrees.
Using this method, four genomewide suggestive regions were identified on chromosomes 2, 4, 7 and 8, and a borderline suggestive region on chromosome 14. Seven additional regions with at least nominal evidence were observed. Of particular note among these total twelve regions were three regions that were identified in two pedigrees each; chromosomes 4, 7 and 14. Follow-up two-pedigree pSGS analyses further indicated excessive genomic sharing across the pedigrees in all three regions, suggesting that the underlying susceptibility alleles in those regions may be shared in common. In general, the pSGS regions identified were quite large (average 32.2 Mb), however, the range was wide (0.3 – 88.2 Mb). Several of the regions identified overlapped with loci and genes that have been previously implicated in breast cancer risk, including NBS1, BRCA1 and RAD51L1.
Our analyses have provided several loci of interest to pursue in these high-risk pedigrees and illustrate the utility of the weighted pSGS method and extended pedigrees for gene mapping in complex diseases. A focused sequencing effort across these loci in the sharing individuals is the natural next step to further map the critical underlying susceptibility variants in these regions.
PMCID: PMC3561143  PMID: 23190577
Breast cancer; High-risk pedigrees; Susceptibility; Germline; Genomic sharing
14.  HOXB13 is a susceptibility gene for prostate cancer: results from the International Consortium for Prostate Cancer Genetics (ICPCG) 
Human Genetics  2012;132(1):5-14.
Prostate cancer has a strong familial component but uncovering the molecular basis for inherited susceptibility for this disease has been challenging. Recently, a rare, recurrent mutation (G84E) in HOXB13 was reported to be associated with prostate cancer risk. Confirmation and characterization of this finding is necessary to potentially translate this information to the clinic. To examine this finding in a large international sample of prostate cancer families, we genotyped this mutation and 14 other SNPs in or flanking HOXB13 in 2,443 prostate cancer families recruited by the International Consortium for Prostate Cancer Genetics (ICPCG). At least one mutation carrier was found in 112 prostate cancer families (4.6 %), all of European descent. Within carrier families, the G84E mutation was more common in men with a diagnosis of prostate cancer (194 of 382, 51 %) than those without (42 of 137, 30 %), P = 9.9 × 10−8 [odds ratio 4.42 (95 % confidence interval 2.56–7.64)]. A family-based association test found G84E to be significantly over-transmitted from parents to affected offspring (P = 6.5 × 10−6). Analysis of markers flanking the G84E mutation indicates that it resides in the same haplotype in 95 % of carriers, consistent with a founder effect. Clinical characteristics of cancers in mutation carriers included features of high-risk disease. These findings demonstrate that the HOXB13 G84E mutation is present in ~5 % of prostate cancer families, predominantly of European descent, and confirm its association with prostate cancer risk. While future studies are needed to more fully define the clinical utility of this observation, this allele and others like it could form the basis for early, targeted screening of men at elevated risk for this common, clinically heterogeneous cancer.
Electronic supplementary material
The online version of this article (doi:10.1007/s00439-012-1229-4) contains supplementary material, which is available to authorized users.
PMCID: PMC3535370  PMID: 23064873
15.  Genome-wide linkage analysis of 1233 prostate cancer pedigrees from the International Consortium for Prostate Cancer Genetics using novel sumLINK and sumLOD analyses 
The Prostate  2010;70(7):735-744.
Prostate cancer is generally believed to have a strong inherited component, but the search for susceptibility genes has been hindered by the effects of genetic heterogeneity. The recently developed sumLINK and sumLOD statistics are powerful tools for linkage analysis in the presence of heterogeneity.
We performed a secondary analysis of 1233 prostate cancer pedigrees from the International Consortium for Prostate Cancer Genetics (ICPCG) using two novel statistics, the sumLINK and sumLOD. For both statistics, dominant and recessive genetic models were considered. False discovery rate (FDR) analysis was conducted to assess the effects of multiple testing.
Our analysis identified significant linkage evidence at chromosome 22q12, confirming previous findings by the initial conventional analyses of the same ICPCG data. Twelve other regions were identified with genomewide suggestive evidence for linkage. Seven regions (1q23, 5q11, 5q35, 6p21, 8q12, 11q13, 20p11-q11) are near loci previously identified in the initial ICPCG pooled data analysis or the subset of aggressive prostate cancer (PC) pedigrees. Three other regions (1p12, 8p23, 19q13) confirm loci reported by others, and two (2p24, 6q27) are novel susceptibility loci. FDR testing indicates that over 70% of these results are likely true positive findings. Statistical recombinant mapping narrowed regions to an average of 9 cM.
Our results represent genomic regions with the greatest consistency of positive linkage evidence across a very large collection of high-risk prostate cancer pedigrees using new statistical tests that deal powerfully with heterogeneity. These regions are excellent candidates for further study to identify prostate cancer predisposition genes.
PMCID: PMC3428045  PMID: 20333727
16.  Fine-mapping CASP8 risk variants in Breast Cancer 
Multiple genome-wide and candidate gene association studies have been performed in search of common risk variants for breast cancer. Recent large meta analyses, consolidating evidence from these studies, have been consistent in highlighting the caspase-8 (CASP8) gene as important in this regard. In order to define a risk haplotype and map the CASP8 gene region with respect to underlying susceptibility variant/s, we screened four genes in the CASP8 region on 2q33-q34 for breast cancer risk.
Two independent data sets from the United Kingdom and the United States, including 3,888 breast cancer cases and controls, were genotyped for 45 tagging single nucleotide polymorphisms (tSNP) in the expanded CASP8 region. SNP and haplotype association tests were carried out using Monte Carlo based methods.
We identified a three-SNP haplotype across rs3834129, rs6723097 and rs3817578 that was significantly associated with breast cancer (p<5×10−6), with a dominant risk ratio and 95% confidence interval of 1.28 (1.21–1.35) and frequency of 0.29 in controls. Evidence for this risk haplotype was extremely consistent across the two study sites and also consistent with previous data.
This three-SNP risk haplotype represents the best characterization so far of the chromosome upon which the susceptibility variant resides.
Characterization of the risk haplotype provides a strong foundation for re-sequencing efforts to identify the underlying risk variant, which may prove useful for individual-level risk prediction, and provide novel insights into breast carcinogenesis.
PMCID: PMC3253962  PMID: 22056502
Single nucleotide polymorphisms; risk haplotype; breast cancer; CASP8; apoptosis pathway
17.  Analysis of Xq27-28 linkage in the international consortium for prostate cancer genetics (ICPCG) families 
BMC Medical Genetics  2012;13:46.
Genetic variants are likely to contribute to a portion of prostate cancer risk. Full elucidation of the genetic etiology of prostate cancer is difficult because of incomplete penetrance and genetic and phenotypic heterogeneity. Current evidence suggests that genetic linkage to prostate cancer has been found on several chromosomes including the X; however, identification of causative genes has been elusive.
Parametric and non-parametric linkage analyses were performed using 26 microsatellite markers in each of 11 groups of multiple-case prostate cancer families from the International Consortium for Prostate Cancer Genetics (ICPCG). Meta-analyses of the resultant family-specific linkage statistics across the entire 1,323 families and in several predefined subsets were then performed.
Meta-analyses of linkage statistics resulted in a maximum parametric heterogeneity lod score (HLOD) of 1.28, and an allele-sharing lod score (LOD) of 2.0 in favor of linkage to Xq27-q28 at 138 cM. In subset analyses, families with average age at onset less than 65 years exhibited a maximum HLOD of 1.8 (at 138 cM) versus a maximum regional HLOD of only 0.32 in families with average age at onset of 65 years or older. Surprisingly, the subset of families with only 2–3 affected men and some evidence of male-to-male transmission of prostate cancer gave the strongest evidence of linkage to the region (HLOD = 3.24, 134 cM). For this subset, the HLOD was slightly increased (HLOD = 3.47 at 134 cM) when families used in the original published report of linkage to Xq27-28 were excluded.
Although there was not strong support for linkage to the Xq27-28 region in the complete set of families, the subset of families with earlier age at onset exhibited more evidence of linkage than families with later onset of disease. A subset of families with 2–3 affected individuals and with some evidence of male to male disease transmission showed stronger linkage signals. Our results suggest that the genetic basis for prostate cancer in our families is much more complex than a single susceptibility locus on the X chromosome, and that future explorations of the Xq27-28 region should focus on the subset of families identified here with the strongest evidence of linkage to this region.
PMCID: PMC3495053  PMID: 22712434
18.  Identification of regions of positive selection using Shared Genomic Segment analysis 
We applied a shared genomic segment (SGS) analysis, incorporating an error model, to identify complete, or near complete, selective sweeps in the HapMap phase II data sets. This method is based on detecting heterozygous sharing across all individuals within a population, to identify regions of sharing with at least one allele in common. We identified multiple interesting regions, many of which are concordant with positive selection regions detected by previous population genetic tests. Others are suggested to be novel regions. Our finding illustrates the utility of SGS as a method for identifying regions of selection, and some of these regions have been proposed to be candidate regions for harboring disease genes.
PMCID: PMC3110045  PMID: 21304558
identity by state; identity by descent; positive selection
19.  National Cancer Institute Prostate Cancer Genetics Workshop 
Cancer research  2011;71(10):3442-3446.
Compelling evidence supports a genetic component to prostate cancer (PC) susceptibility and aggressiveness. Recent genome-wide association studies (GWAS) have identified >30 single nucleotide polymorphisms associated with PC susceptibility. It remains unclear, however, whether such genetic variants are associated with disease aggressiveness—one of the most important questions in PC research today. To help clarify this and substantially expand research in the genetic determinants of PC aggressiveness, the first National Cancer Institute Prostate Cancer Genetics Workshop assembled researchers to develop plans for a large new research consortium and patient cohort. The workshop reviewed the prior work in this area and addressed the practical issues in planning future studies. With new DNA sequencing technology, the potential application of sequencing information to patient care is emerging. The workshop, therefore, included state-of-the-art presentations by experts on new genotyping technologies, including sequencing and associated bioinformatics issues, which are just beginning to be applied to cancer genetics.
PMCID: PMC3096727  PMID: 21558387
20.  Immnuophenotypic and Gene Expression Analysis of Monoclonal B Cell Lymphocytosis Shows Biologic Characteristics Associated With Good Prognosis CLL 
Monoclonal B cell lymphocytosis (MBL) is a hematologic condition wherein small B cell clones can be detected in the blood of asymptomatic individuals. Most MBL have an immunophenotype similar to chronic lymphocytic leukemia (CLL), and “CLL-like” MBL is a precursor to CLL. We used flow cytometry to identify MBL from unaffected members of CLL kindreds. We identified 101 MBL cases from 622 study subjects; of these, 82 individuals with MBL were further characterized. Ninety-one unique MBL clones were detected: 73 CLL-like MBL (CD5+CD20dimsIgdim), 11 atypical MBL (CD5+CD20+sIg+), and 7 CD5neg MBL (CD5negCD20+sIgneg). Extended immunophenotypic characterization of these MBL subtypes was performed, and significant differences in cell surface expression of CD23, CD49d, CD79b, and FMC-7 were observed among the groups. Markers of risk in CLL such as CD38, ZAP70, and CD49d were infrequently expressed in CLL-like MBL, but were expressed in the majority of atypical MBL. Interphase cytogenetics was performed in 35 MBL cases, and del 13q14 was most common (22/30 CLL-like MBL cases). Gene expression analysis using oligonucleotide arrays was performed on 7 CLL-like MBL, and showed activation of B cell receptor associated pathways. Our findings underscore the diversity of MBL subtypes and further clarify the relationship between MBL and other lymphoproliferative disorders.
PMCID: PMC3164475  PMID: 21617698
21.  Common Variants in 6 Lipid-Related Genes Discovered by High-Resolution DNA Melting Analysis and Their Association with Plasma Lipids 
Journal of clinical & experimental cardiology  2011;2(138):2155-9880-2-138.
Total cholesterol was among the earliest identified risk factors for coronary heart disease (CHD). We sought to identify genetic variants in six genes associated with lipid metabolism and estimate their respective contribution to risk for CHD.
For 6 lipid-associated genes (LCAT, CETP, LIPC, LPL, SCARB1, and ApoF) we scanned exons, 5′ and 3′ untranslated regions, and donor and acceptor splice sites for variants using Hi-Res Melting® curve analysis (HRMCA) with confirmation by cycle sequencing. Healthy subjects were used for SNP discovery (n=64), haplotype determination/tagging SNP discovery (n=339), and lipid association testing (n=786).
In 17,840 bases of interrogated sequence, 90 variant SNPs were identified; 19 (21.1%) previously unreported. Thirty-four variants (37.8%) were exonic(16 non-synonymous), 28 (31.1%) in intron-exon boundaries, and 28 (31.1%) in the 5′ and 3′ untranslated regions. Compared to cycle sequencing, HRMCA had sensitivity of 99.4% and specificity of 97.7%. Tagging SNPs (n=38) explained >90% of the variation in the 6 genes and identified linkage disequilibrium (LD) groups. Significant beneficial lipid profiles were observed for CETP LD group 2, LIPC LD groups 1 and 7, and SCARB1 LD groups 1, 3 and 4. Risk profiles worsened for CETP LD group 3, LPL LD group 4.
These findings demonstrate the feasibility, sensitivity, and specificity of HRMCA for SNP discovery. Variants identified in these genes may be used to predict lipid-associated risk and reclassification of clinical CHD risk.
PMCID: PMC3251308  PMID: 22229114
Lipids; Genetic variants; Coronary heart disease; High resolution melting curve analysis
22.  Pairwise shared genomic segment analysis in high-risk pedigrees: application to Genetic Analysis Workshop 17 exome-sequencing SNP data 
BMC Proceedings  2011;5(Suppl 9):S9.
We applied our method of pairwise shared genomic segment (pSGS) analysis to high-risk pedigrees identified from the Genetic Analysis Workshop 17 (GAW17) mini-exome sequencing data set. The original shared genomic segment method focused on identifying regions shared by all case subjects in a pedigree; thus it can be sensitive to sporadic cases. Our new method examines sharing among all pairs of case subjects in a high-risk pedigree and then uses the mean sharing as the test statistic; in addition, the significance is assessed empirically based on the pedigree structure and linkage disequilibrium pattern of the single-nucleotide polymorphisms. Using all GAW17 replicates, we identified 18 unilineal high-risk pedigrees that contained excess disease (p < 0.01) and at least 15 meioses between case subjects. Eighteen rare causal variants were polymorphic in this set of pedigrees. Based on a significance threshold of 0.001, 72.2% (13/18) of these pedigrees were successfully identified with at least one region that contains a true causal variant. The regions identified included 4 of the possible 18 polymorphic causal variants. On average, 1.1 true positives and 1.7 false positives were identified per pedigree. In conclusion, we have demonstrated the potential of our new pSGS method for localizing rare disease causal variants in common disease using high-risk pedigrees and exome sequence data.
PMCID: PMC3287931  PMID: 22373081
23.  National Cancer Institute Prostate Cancer Genetics Workshop 
Cancer research  2011;71(10):3442-3446.
Compelling evidence supports a genetic component to prostate cancer (PC) susceptibility and aggressiveness. Recent genome-wide association studies (GWAS) have identified >30 single nucleotide polymorphisms associated with PC susceptibility. It remains unclear, however, whether such genetic variants are associated with disease aggressiveness—one of the most important questions in PC research today. To help clarify this and substantially expand research in the genetic determinants of PC aggressiveness, the first National Cancer Institute Prostate Cancer Genetics Workshop assembled researchers to develop plans for a large new research consortium and patient cohort. The workshop reviewed the prior work in this area and addressed the practical issues in planning future studies. With new DNA sequencing technology, the potential application of sequencing information to patient care is emerging. The workshop, therefore, included state-of-the-art presentations by experts on new genotyping technologies, including sequencing and associated bioinformatics issues, which are just beginning to be applied to cancer genetics.
PMCID: PMC3096727  PMID: 21558387
24.  Common Occurrence of Monoclonal B-cell Lymphocytosis Among Members of High-Risk CLL Families 
British journal of haematology  2010;151(2):152-158.
Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic haematological condition characterized by low absolute levels of B-cell clones with a surface immunophenotype similar to that of chronic lymphocytic leukaemia (CLL). In the general population, MBL increases with age with a prevalence of 5–9% in individuals over age 60 years. It has been reported to be higher among first-degree relatives from CLL families. We report results of multi-parameter flow cytometry among 505 first-degree relatives with no personal history of lymphoproliferative disease from 140 families having at least two cases of CLL. Seventeen percent of relatives had MBL. Age was the most important determinant where the probability for developing MBL by age 90 years was 61%. MBL clustered in certain families but clustering was independent of the number of known CLL cases in a family. As is the case with CLL, males had a significantly higher risk for MBL than did females (p=0.04). MBL patients had significantly higher mean absolute lymphocyte counts (2.4 × 109/l) and B-cell counts (0.53 × 109/l) than those with a normal B-cell immunophenotype. Our findings show that MBL occurs at a very high rate in high risk CLL families. Both the age and gender distribution of MBL are parallel to CLL, implying a shared inherited risk.
PMCID: PMC2966536  PMID: 20738309
chronic lymphocytic leukaemia; high risk families; monoclonal B-cell lymphocytosis; flow cytometry
25.  Joint Effects of Common Genetic Variants from Multiple Genes and Pathways On the Risk of Premature Coronary Artery Disease 
American heart journal  2010;160(2):250-256.e3.
To discover common variants in 6 lipid metabolic genes and construct and validate a genetic risk score (GRS) based on the joint effects of genetic variants in multiple genes from lipid and other pathobiologic pathways.
Explaining the genetic basis of coronary artery disease (CAD) is incomplete. Discovery and aggregation of genetic variants from multiple pathways may advance this objective.
Premature CAD cases (N=1,918) and CAD-free controls (N=1,032) were selected from our angiographic registry. In a discovery phase, single nucleotide polymorphisms (SNPs) at 56 loci from internal discovery and external reports were tested for associations with biomarkers and CAD: 28 promising SNPs were then tested jointly for CAD associations, and a genetic risk score (GRS) consisting of SNPs contributing independently was constructed and validated in a replication set of familial cases and population-based controls (N=1,320).
Five variants contributed jointly to CAD prediction in a multigenic GRS model: odds ratio (OR) =1.24 (95% CI 1.16–1.33) per risk allele, p=8.2×10−11, adjusted OR=2.03 (1.53–2.70), 4th vs. 1st quartile. GRS5 had minor impact on area under the receiver-operating characteristic curve (p>0.05) but resulted in substantial net reclassification improvement: 0.16 overall, 0.28 in intermediate risk patients (both p<0.0001). GRS5 predicted familial CAD with similar magnitude in the validation set.
CorGen demonstrates the ability of a multigenic, multipathway GRS to improve discrimination of angiographic CAD. Genetic risk scores promise to increase understanding of the genetic basis of CAD and improve identification of individuals at increased CAD risk.
PMCID: PMC2919893  PMID: 20691829
Coronary artery disease; genetics; risk; risk score

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