Search tips
Search criteria

Results 1-25 (83)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
author:("Hou, weifang")
1.  Effects of particulate matter exposure on blood 5-hydroxymethylation: results from the Beijing truck driver air pollution study  
Epigenetics  2015;10(7):633-642.
Previous studies have reported epigenetic changes induced by environmental exposures. However, previous investigations did not distinguish 5-methylcytosine (5mC) from a similar oxidative form with opposite functions, 5-hydroxymethylcytosine (5hmC). Here, we measured blood DNA global 5mC and 5hmC by ELISA and used adjusted mixed-effects regression models to evaluate the effects of ambient PM10 and personal PM2.5 and its elemental components—black carbon (BC), aluminum (Al), calcium (Ca), potassium (K), iron (Fe), sulfur (S), silicon (Si), titanium (Ti), and zinc (Zn)—on blood global 5mC and 5hmC levels. The study was conducted in 60 truck drivers and 60 office workers in Beijing, China from The Beijing Truck Driver Air Pollution Study at 2 exams separated by one to 2 weeks. Blood 5hmC level (0.08%) was ∼83-fold lower than 5mC (6.61%). An inter-quartile range (IQR) increase in same-day PM10 was associated with increases in 5hmC of 26.1% in office workers (P = 0.004), 20.2% in truck drivers (P = 0.014), and 21.9% in all participants combined (P < 0.001). PM10 effects on 5hmC were increasingly stronger when averaged over 4, 7, and 14 d preceding assessment (up to 132.6% for the 14-d average in all participants, P < 0.001). PM10 effects were also significant after controlling for multiple testing (family-wise error rate; FWER < 0.05). 5hmC was not correlated with personal measures of PM2.5 and elemental components (FWER > 0.05). 5mC showed no correlations with PM10, PM2.5, and elemental components measures (FWER > 0.05). Our study suggests that exposure to ambient PM10 affects 5hmC over time, but not 5mC. This finding demonstrates the need to differentiate 5hmC and 5mC in environmental studies of DNA methylation.
PMCID: PMC4623004  PMID: 25970091
DNA methylation; Epigenetics; Particulate Matter; 5-hydroxymethylcytosine; 5-methylcytosine
2.  Diabetes, metformin and incidence of and death from invasive cancer in postmenopausal women: Results from the women’s health initiative 
International journal of cancer  2015;138(8):1915-1927.
Findings from studies of metformin use with risk of cancer incidence and outcome provide mixed results; with few studies examined associations by recency of diabetes diagnosis or duration of medication use. Thus, in the Women’s Health Initiative, we examined these associations and further explored whether associations differ by recency of diabetes and duration of metformin use. Cox regression models were used to estimate hazard ratios (HR) and their 95% confidence intervals. Diabetes was associated with higher risk of total invasive cancer (HR, 1.13; p < 0.001) and of several site-specific cancers (HR, 1.2–1.4, and up to over twofold). Diabetes was also associated with higher risk of death from cancer (HR, 1.46; p < 0.001). There was no overall difference in cancer incidence by diabetes therapy (p = 0.66). However, there was a lower risk of death from cancer for metformin users, compared to users of other medications, relative to women without diabetes, overall (HRs, 1.08 vs. 1.45; p = 0.007) and for breast cancer (HRs, 0.50 vs. 1.29; p = 0.05). Results also suggested that lower cancer risk associated with metformin may be evident only for a longer duration of use in certain cancer sites or subgroup populations. We provide further evidence that postmenopausal women with diabetes are at higher risk of invasive cancer and cancer death. Metformin users, particularly long-term users, may be at lower risk of developing certain cancers and dying from cancer, compared to users of other anti-diabetes medications. Future studies are needed to determine the long-term effect of metformin in cancer risk and survival from cancer.
PMCID: PMC4830266  PMID: 26616262
diabetes; metformin; invasive cancer; incidence; mortality
3.  Optimal Cutoffs of Obesity Measures in Relation to Cancer Risk in Postmenopausal Women in the Women's Health Initiative Study 
Journal of Women's Health  2015;24(3):218-227.
Background: Obesity is a risk factor for several cancers in postmenopausal women. We attempted to determine cutoffs of adiposity measures in relation to risk of obesity-related cancers among postmenopausal women and to examine the effects of hormone therapy (HT) use on the cutoffs, neither of which has been broadly studied.
Methods: We used data from the Women's Health Initiative cohort (n=144,701) and applied Cox-proportional hazards regressions to each combination of 17 cancer types and 6 anthropometric measures (weight, body mass index [BMI], weight to height ratio, waist circumference, waist to hip ratio [WHR], and waist to height ratio). Interactions between the anthropometric measures and HT use were also examined. Cutoffs were determined by applying a grid search followed by a two-fold cross validation method. Survival ROC analysis of 5- and 10-year incidence followed.
Results: Breast, colorectal, colon, endometrium, kidney, and all cancers combined were significantly positively associated with all six anthropometric measures, whereas lung cancer among ever smokers was significantly inversely associated with all measures except WHR. The derived cutoffs of each obesity measure varied across cancers (e.g., BMI cutoffs for breast and endometrium cancers were 30 kg/m2 and 34 kg/m2, respectively), and also depended on HT use. The Youden indices of the cutoffs for predicting 5- and 10-year cancer incidence were higher among HT never users.
Conclusion: Using a panel of different anthropometric measures, we derived optimal cut-offs categorizing populations into high- and low-risk groups, which differed by cancer type and HT use. Although the discrimination abilities of these risk categories were generally poor, the results of this study could serve as a starting point from which to determine adiposity cutoffs for inclusion in risk prediction models for specific cancer types.
PMCID: PMC4363798  PMID: 25587642
4.  The Association between Dietary Inflammatory Index and Risk of Colorectal Cancer among Postmenopausal Women: Results from the Women’s Health Initiative 
Cancer causes & control : CCC  2014;26(3):399-408.
Inflammation is a process central to carcinogenesis, and in particular to colorectal cancer (CRC). Previously, we developed a dietary inflammatory index (DII) from extensive literature review to assess the inflammatory potential of diet. In the current study, we utilized this novel index in the Women’s Health Initiative (WHI) to prospectively evaluate its association with risk of CRC in postmenopausal women.
The DII was calculated from baseline food frequency questionnaires administered to 152,536 women aged 50–79 years without CRC at baseline between 1993 and 1998 and followed through September 30, 2010. Incident CRC cases were ascertained through a central physician adjudication process. Multiple covariate-adjusted Cox proportional hazards regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (95%CI) for colorectal, colon (proximal/distal locations), and rectal cancer risk, by DII quintiles(Q).
During an average 11.3 years of follow-up, a total of 1,920 cases of colorectal cancer (1,559 colon and 361 rectal) were identified. Higher DII scores (representing a more pro-inflammatory diet) were associated with an increased incidence of colorectal cancer (HRQ5-Q1, 1.22; 95% CI, 1.05, 1.43; Ptrend=0.02) and colon cancer, specifically proximal colon cancer (HRQ5-Q1, 1.35; 95% CI, 1.05, 1.67; Ptrend=0.01) but not distal colon cancer (HRQ5-Q1, 0.84; 95% CI, 0.61, 1.18; Ptrend=0.63) or rectal cancer (HRQ5-Q1, 1.20; 95% CI, 0.84, 1.72; Ptrend=0.65).
Consumption of pro-inflammatory diets is associated with an increased risk of CRC, especially cancers located in the proximal colon. The absence of a significant association for distal colon cancer and rectal cancer may be due to the small number of incident cases for these sites. Interventions that may reduce the inflammatory potential of the diet are warranted to test our findings, thus provide more information for colon cancer prevention.
PMCID: PMC4334706  PMID: 25549833
dietary inflammatory index; colorectal cancer; Women’s Health Initiative
5.  Particulate Air Pollution Exposure and Expression of Viral and Human MicroRNAs in Blood: The Beijing Truck Driver Air Pollution Study 
Environmental Health Perspectives  2015;124(3):344-350.
MicroRNAs (miRNAs) are post-transcriptional gene suppressors and potential mediators of environmental effects. In addition to human miRNAs, viral miRNAs expressed from latent viral sequences are detectable in human cells.
In a highly exposed population in Beijing, China, we evaluated the associations of particulate air pollution exposure on blood miRNA profiles.
The Beijing Truck Driver Air Pollution Study (BTDAS) included 60 truck drivers and 60 office workers. We investigated associations of short-term air pollution exposure, using measures of personal PM2.5 (particulate matter ≤ 2.5 μm) and elemental carbon (EC), and ambient PM10 (≤ 10 μm), with blood NanoString nCounter miRNA profiles at two exams separated by 1–2 weeks.
No miRNA was significantly associated with personal PM2.5 at a false discovery rate (FDR) of 20%. Short-term ambient PM10 was associated with the expression of 12 miRNAs in office workers only (FDR < 20%). Short-term EC was associated with differential expression of 46 human and 7 viral miRNAs, the latter including 3 and 4 viral miRNAs in office workers and truck drivers, respectively. EC-associated miRNAs differed between office workers and truck drivers with significant effect modification by occupational group. Functional interaction network analysis suggested enriched cellular proliferation/differentiation pathways in truck drivers and proinflammation pathways in office workers.
Short-term EC exposure was associated with the expression of human and viral miRNAs that may influence immune responses and other biological pathways. Associations between EC exposure and viral miRNA expression suggest that latent viral miRNAs are potential mediators of air pollution–associated health effects. PM2.5/PM10 exposures showed no consistent relationships with miRNA expression.
Hou L, Barupal J, Zhang W, Zheng Y, Liu L, Zhang X, Dou C, McCracken JP, Díaz A, Motta V, Sanchez-Guerra M, Wolf KR, Bertazzi PA, Schwartz JD, Wang S, Baccarelli AA. 2016. Particulate air pollution exposure and expression of viral and human microRNAs in blood: the Beijing Truck Driver Air Pollution Study. Environ Health Perspect 124:344–350;
PMCID: PMC4786978  PMID: 26068961
6.  Blood Epigenetic Age may Predict Cancer Incidence and Mortality 
EBioMedicine  2016;5:68-73.
Biological measures of aging are important for understanding the health of an aging population, with epigenetics particularly promising. Previous studies found that tumor tissue is epigenetically older than its donors are chronologically. We examined whether blood Δage (the discrepancy between epigenetic and chronological ages) can predict cancer incidence or mortality, thus assessing its potential as a cancer biomarker. In a prospective cohort, Δage and its rate of change over time were calculated in 834 blood leukocyte samples collected from 442 participants free of cancer at blood draw. About 3–5 years before cancer onset or death, Δage was associated with cancer risks in a dose-responsive manner (P = 0.02) and a one-year increase in Δage was associated with cancer incidence (HR: 1.06, 95% CI: 1.02–1.10) and mortality (HR: 1.17, 95% CI: 1.07–1.28). Participants with smaller Δage and decelerated epigenetic aging over time had the lowest risks of cancer incidence (P = 0.003) and mortality (P = 0.02). Δage was associated with cancer incidence in a ‘J-shaped’ manner for subjects examined pre-2003, and with cancer mortality in a time-varying manner. We conclude that blood epigenetic age may mirror epigenetic abnormalities related to cancer development, potentially serving as a minimally invasive biomarker for cancer early detection.
•We prospectively examined blood Δage and its ability to predict cancer risks.•Epigenetic age older than chronological age elevated cancer risk.•Δage predicted cancer incidence and mortality in a dose-responsive manner.•The Δage–cancer relationship was a nonlinear ‘J-shape’ for subjects measured before 2003.Blood-based epigenetic age is a potential biomarker for cancer early detection.
This study studies a way to calculate your body's age, not based on how old you are, but by measuring a number of markers in your blood — called epigenetic age. This paper also looks at how good epigenetic age over time is at predicting whether you'll get cancer, and whether you'll die from it. The authors found that epigenetic age could be good at predicting both of these things, which means that someday it could be developed into a blood test for diagnosing cancer, and for helping patients figure out how long they'll live.
PMCID: PMC4816845  PMID: 27077113
Epigenetic age; Cancer risk; DNA methylation
7.  Red meat intake, NAT2, and risk of colorectal cancer: A pooled analysis of 11 studies 
Red meat intake has been associated with risk of colorectal cancer (CRC), potentially mediated through heterocyclic amines. The metabolic efficiency of N-acetyltransferase 2 (NAT2) required for the metabolic activation of such amines is influenced by genetic variation. The interaction between red meat intake, NAT2 genotype, and CRC has been inconsistently reported.
We used pooled individual-level data from the Colon Cancer Family Registry (CCFR) and the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO). Red meat intake was collected by each study. We inferred NAT2 phenotype based on polymorphism at rs1495741, highly predictive of enzyme activity. Interaction was assessed using multiplicative interaction terms in multivariate-adjusted models.
From 11 studies, 8,290 CRC cases and 9,115 controls were included. The highest quartile of red meat intake was associated with increased risk of CRC compared to the lowest quartile (OR 1.41, 95%CI 1.29 – 1.55). However, a significant association was observed only for studies with retrospective diet data, not for studies with diet prospectively assessed before cancer diagnosis. Combining all studies, high red meat intake was similarly associated with CRC in those with a rapid/intermediate NAT2 genotype (OR 1.38, 95%CI 1.20 – 1.59) as with a slow genotype (OR 1.43, 95%CI 1.28 – 1.61) (p- interaction=0.9).
We found that high red meat intake was associated with increased risk of CRC only from retrospective case-control studies and not modified by NAT2 enzyme activity.
Our results suggest no interaction between NAT2 genotype and red-meat intake in mediating risk of CRC.
PMCID: PMC4294960  PMID: 25342387
9.  Cancer Incidence and Mortality during the intervention and post intervention periods of the Women’s Health Initiative Dietary Modification Trial 
The Women’s Health Initiative (WHI) low fat (20% kcal) diet modification (DM) trial (1993–2005) demonstrated a non-significant reduction in breast cancer, a nominally significant reduction in ovarian cancer and no effect on other cancers (mean 8.3 years intervention). Consent to non-intervention follow-up was 83% (n=37,858). This analysis was designed to assess post-intervention cancer risk in women randomized to the low-fat diet (40%) versus usual diet comparison (60%).
Randomized, controlled low fat diet intervention for prevention of breast and colorectal cancers conducted in 48,835 postmenopausal U.S. women, aged 50–79 years at 40 U.S. sites. Outcomes included total invasive cancer, breast and colorectal cancer, cancer-specific and overall mortality.
There were no intervention effects on invasive breast 1.08 (0.94, 1.24) or colorectal cancer, other cancers, cancer-specific or overall mortality during the post-intervention period or the combined intervention and follow-up periods. For invasive breast cancer, the HRs were 0.92 (0.84, 1.01) during intervention, during the post-intervention period, and 0.97 (0.89, 1.05) during cumulative follow up. A reduced risk for estrogen receptor positive/progesterone receptor negative tumors was demonstrated during follow-up. Women with higher baseline fat intake (quartile), point estimates of breast cancer risk were HR-0.76; 0.62, 0.92 during intervention versus HR-1.11; 0.84, 1.4 during post-intervention follow-up (p-diff=.03).
Dietary fat intake rose post-intervention in intervention women; no long-term reduction in cancer risk or mortality was shown in the WHI DM trial.
Dietary advisement to reduce fat for cancer prevention after menopause generally was not supported by the WHI DM trial.
PMCID: PMC4257879  PMID: 25258014
breast cancer; colorectal cancer; mortality; low-fat diet; randomized controlled trial
10.  Organic Pollutants and Telomere Length: A New Facet of Carcinogenesis 
EBioMedicine  2015;2(12):1854-1855.
PMCID: PMC4703728  PMID: 26844257
11.  Association of Cancer Susceptibility Variants with Risk of Multiple Primary Cancers: the Population Architecture using Genomics and Epidemiology Study 
Multiple primary cancers account for ~16% of all incident cancers in the U.S.. While genome-wide association studies (GWAS) have identified many common genetic variants associated with various cancer sites, no study has examined the association of these genetic variants with risk of multiple primary cancers (MPC).
As part of the NHGRI Population Architecture using Genomics and Epidemiology (PAGE) study, we used data from the Multiethnic Cohort and Women’s Health Initiative. Incident MPC (IMPC) cases (n=1,385) were defined as participants diagnosed with >1 incident cancers after cohort entry. Participants diagnosed with only one incident cancer after cohort entry with follow-up equal to or longer than IMPC cases served as controls (single-index cancer controls; n= 9,626). Fixed-effects meta-analyses of unconditional logistic regression analyses were used to evaluate the association between cancer risk variants and IMPC risk. To account for multiple comparisons, we used the false positive report probability (FPRP) to determine statistical significance.
A nicotine dependence-associated and lung cancer variant, CHRNA3 rs578776 (OR=1.16, 95% CI=1.05–1.26; p=0.004) and two breast cancer variants, EMBP1 rs11249433 and TOX3 rs3803662 (OR=1.16, 95% CI=1.04–1.28; p=0.005 and OR=1.13, 95% CI=1.03–1.23; p=0.006) were significantly associated with risk of IMPC. The associations for rs578776 and rs11249433 remained (p<0.05) after removing subjects who had lung or breast cancers, respectively (p-values≤0.046). These associations did not show significant heterogeneity by smoking status (p-heterogeneity≥0.53).
Our study has identified rs578776 and rs11249433 as risk variants for IMPC.
These findings may help to identify genetic regions associated with IMPC risk.
PMCID: PMC4221293  PMID: 25139936
Multiple Primary Cancer; Cancer Genetic Risk Variants
12.  PGS: a tool for association study of high-dimensional microRNA expression data with repeated measures 
Bioinformatics  2014;30(19):2802-2807.
Motivation: MicroRNAs (miRNAs) are short single-stranded non-coding molecules that usually function as negative regulators to silence or suppress gene expression. Owning to the dynamic nature of miRNA and reduced microarray and sequencing costs, a growing number of researchers are now measuring high-dimensional miRNA expression data using repeated or multiple measures in which each individual has more than one sample collected and measured over time. However, the commonly used univariate association testing or the site-by-site (SBS) testing may underutilize the longitudinal feature of the data, leading to underpowered results and less biologically meaningful results.
Results: We propose a penalized regression model incorporating grid search method (PGS), for analyzing associations of high-dimensional miRNA expression data with repeated measures. The development of this analytical framework was motivated by a real-world miRNA dataset. Comparisons between PGS and the SBS testing revealed that PGS provided smaller phenotype prediction errors and higher enrichment of phenotype-related biological pathways than the SBS testing. Our extensive simulations showed that PGS provided more accurate estimates and higher sensitivity than the SBS testing with comparable specificities.
Availability and implementation: R source code for PGS algorithm, implementation example and simulation study are available for download at
Supplementary information: Supplementary data are available at Bioinformatics online.
PMCID: PMC4173025  PMID: 24947752
13.  Birth Weight and Subsequent Risk of Cancer 
Cancer epidemiology  2014;38(5):538-543.
We aimed to determine the association between self-reported birth weight and incident cancer in the Women’s Health Initiative Observational Study cohort, a large multiethnic cohort of postmenopausal women.
65,850 women reported their birth weight by category (<6 lbs., 6 lbs.–7 lbs. 15 oz., 8 lbs.–9 lbs. 15 oz., and ≥10 lbs.). All self-reported, incident cancers were adjudicated by study staff. We used Cox proportional hazards regression to estimate crude and adjusted hazard ratios (aHR) for associations between birth weight and: 1) all cancer sites combined, 2) gynecologic cancers, and 3) several site-specific cancer sites.
After adjustments, birth weight was positively associated with the risk of lung cancer (p=0.01), and colon cancer (p=0.04). An inverse trend was observed between birth weight and risk for leukemia (p=0.04). A significant trend was not observed with breast cancer risk (p=0.67); however, women born weighing ≥10 lbs. were less likely to develop breast cancer compared to women born between 6 lbs.–7 lbs. 15 oz (aHR 0.77, 95% CI 0.63, 0.94).
Birth weight category appears to be significantly associated with the risk of any postmenopausal incident cancer, though the direction of the association varies by cancer type.
PMCID: PMC4188724  PMID: 25096278
birth weight; neoplasms; breast neoplasms; colorectal neoplasms; lung neoplasms; ovarian neoplasms; endometrial neoplasms; leukemia
14.  Characterization of genome-wide H3K27ac profiles reveals a distinct PM2.5-associated histone modification signature 
Environmental Health  2015;14:65.
Current studies of environmental health suggest a link between air pollution components, such as particulate matter (PM), and various diseases. However, the specific genes and regulatory mechanisms implicated in PM-induced diseases remain largely unknown. Epigenetic systems such as covalent modification of histones in chromatin may mediate environmental factors in gene regulation. Investigating the relationships between PM exposure and histone modification status may help understand the mechanisms underlying environment-associated health conditions.
In this study, we obtained genome-wide profiles of H3K27ac (histone 3 lysine 27 acetylation), known to be an active gene regulatory histone modification marker, in blood samples collected from four Chinese individuals exposed to high or low PM2.5 (particles with diameters up to 2.5 μm).
The genome-wide chromatin immunoprecipitation sequencing (ChIP-Seq) data indicated a comprehensive differential H3K27ac landscape across the individual genomes, which was associated with high PM2.5. Moreover, a substantial number of these PM2.5-associated differential H3K27ac markers were in genes involved in immune cell activation, potentially linking these epigenetic changes with air pollution-induced immune and inflammatory responses.
Our study provides the first genome-wide characterization of H3K27ac profiles in individuals subjected to different exposure levels of PM2.5. Future systematic investigations of the relationships between air pollutants and histone modifications in large population samples are warranted to elucidate the contributions of histone modifications to environment-associated diseases.
Electronic supplementary material
The online version of this article (doi:10.1186/s12940-015-0052-5) contains supplementary material, which is available to authorized users.
PMCID: PMC4537530  PMID: 26276146
Histone modification; H3K27ac; Particulate matter; Epigenetics; Environmental health; Gene regulation
15.  Pesticide Use and Relative Leukocyte Telomere Length in the Agricultural Health Study 
PLoS ONE  2015;10(7):e0133382.
Some studies suggest that telomere length (TL) may be influenced by environmental exposures, including pesticides. We examined associations between occupational pesticide use reported at three time points and relative telomere length (RTL) in the Agricultural Health Study (AHS), a prospective cohort study of pesticide applicators in Iowa and North Carolina. RTL was measured by qPCR using leukocyte DNA from 568 cancer-free male AHS participants aged 31-94 years with blood samples collected between 2006 and 2008. Self-reported information, including pesticide use, was collected at three time points: enrollment (1993-1997) and two follow-up questionnaires (1998-2003, 2005-2008). For each pesticide, we evaluated cumulative use (using data from all three questionnaires), and more recent use (using data from the last follow-up questionnaire). Multivariable linear regression was used to examine the associations between pesticide use (ever, lifetime days, intensity-weighted lifetime days (lifetime days*intensity score)) and RTL, adjusting for age at blood draw and use of other pesticides. Of the 57 pesticides evaluated with cumulative use, increasing lifetime days of 2,4-D (p-trend=0.001), diazinon (p-trend=0.002), and butylate (p-trend=0.01) were significantly associated with shorter RTL, while increasing lifetime days of alachlor was significantly associated with longer RTL (p-trend=0.03). Only the association with 2,4-D was significant after adjustment for multiple comparisons. Of the 40 pesticides evaluated for recent use, malathion was associated with shorter RTL (p=0.03), and alachlor with longer RTL (p=0.03). Our findings suggest that leukocyte TL may be impacted by cumulative use and recent use of certain pesticides.
PMCID: PMC4510132  PMID: 26196902
16.  Genetic determinants of telomere length and risk of common cancers: a Mendelian randomization study 
Human Molecular Genetics  2015;24(18):5356-5366.
Epidemiological studies have reported inconsistent associations between telomere length (TL) and risk for various cancers. These inconsistencies are likely attributable, in part, to biases that arise due to post-diagnostic and post-treatment TL measurement. To avoid such biases, we used a Mendelian randomization approach and estimated associations between nine TL-associated SNPs and risk for five common cancer types (breast, lung, colorectal, ovarian and prostate cancer, including subtypes) using data on 51 725 cases and 62 035 controls. We then used an inverse-variance weighted average of the SNP-specific associations to estimate the association between a genetic score representing long TL and cancer risk. The long TL genetic score was significantly associated with increased risk of lung adenocarcinoma (P = 6.3 × 10−15), even after exclusion of a SNP residing in a known lung cancer susceptibility region (TERT-CLPTM1L) P = 6.6 × 10−6). Under Mendelian randomization assumptions, the association estimate [odds ratio (OR) = 2.78] is interpreted as the OR for lung adenocarcinoma corresponding to a 1000 bp increase in TL. The weighted TL SNP score was not associated with other cancer types or subtypes. Our finding that genetic determinants of long TL increase lung adenocarcinoma risk avoids issues with reverse causality and residual confounding that arise in observational studies of TL and disease risk. Under Mendelian randomization assumptions, our finding suggests that longer TL increases lung adenocarcinoma risk. However, caution regarding this causal interpretation is warranted in light of the potential issue of pleiotropy, and a more general interpretation is that SNPs influencing telomere biology are also implicated in lung adenocarcinoma risk.
PMCID: PMC4550826  PMID: 26138067
17.  GDM Women’s Pre-Pregnancy Overweight/Obesity and Gestational Weight Gain on Offspring Overweight Status 
PLoS ONE  2015;10(6):e0129536.
To examine the association of maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) with anthropometry in the offspring of mothers with gestational diabetes mellitus (GDM).
We performed a retrospective cohort study in 1263 GDM mother-child pairs. General linear models and Logistic regression models were used to assess the single and joint associations of maternal pre-pregnancy BMI (normal weight, overweight, and obesity) and GWG (inadequate, adequate and excessive GWG) with anthropometry and overweight status in the offspring from birth to 1-5 years old.
Maternal pre-pregnancy BMI and GWG were positively associated with birth weight for gestational age Z score and birth weight for length for gestational age Z score at birth, and weight for age Z score, length/height for age Z score, and weight for length/height Z score at of 1-5 years old offspring. Maternal pre-pregnancy overweight, obesity, and excessive GWG were associated with increased risks of large for gestational age [ORs 95% CIs = 1.87 (1.37-2.55), 2.98 (1.89-4.69), and 2.93 (2.07-4.13), respectively] and macrosomia [ORs 95% CIs = 2.06 (1.50-2.84), 2.89 (1.78-4.70), and 2.84 (1.98-4.06), respectively] at birth and childhood overweight at 1-5 years old [ORs 95% CIs = 1.26 (0.92-1.73), 1.96 (1.24-3.09), and 1.59 (1.15-2.21), respectively].
Offspring born to GDM mothers with pre-pregnancy overweight/obesity or excessive GWG were associated with increased risks of large for gestational age and macrosomia at birth, and childhood overweight at 1-5 years old, compared with those born to GDM mothers with pre-pregnancy normal weight and adequate GWG.
PMCID: PMC4476720  PMID: 26098307
18.  HIV Viremia and Incidence of Non-Hodgkin Lymphoma in Patients Successfully Treated With Antiretroviral Therapy 
Non-Hodgkin lymphoma incidence is high in HIV-infected patients successfully treated with antiretroviral therapy. HIV replication, even at low levels, may be an important modifiable risk factor for non-Hodgkin lymphoma.
Background. The incidence of non-Hodgkin lymphoma (NHL) in human immunodeficiency virus (HIV)–infected patients remains high despite treatment with antiretroviral therapy (ART).
Methods. We evaluated NHL incidence in HIV-infected patients followed in the Centers for AIDS Research Network of Integrated Clinical Systems who started combination ART and achieved suppression of HIV. We estimated the hazard ratio for NHL by time-varying HIV viremia categories, accounting for time-varying CD4 cell count using marginal structural models.
Results. We observed 37 incident NHL diagnoses during 21 607 person-years of follow-up in 6036 patients (incidence rate, 171 per 100 000 person-years; 95% confidence interval [CI], 124–236). NHL incidence was high even among patients with nadir CD4 cell count >200 cells/µL (140 per 100 000 person-years [95% CI, 80–247]). Compared with ≤50 copies/mL, hazard ratios (HRs) for NHL were higher among those with HIV viremia of 51–500 copies/mL (HR current = 1.66 [95% CI, .70–3.94]; HR 3-month lagged = 2.10 [95% CI, .84–5.22]; and HR 6-month lagged = 1.46 [95% CI, .60–3.60]) and >500 copies/mL (HR current = 2.39 [95% CI, .92–6.21]; HR 3-month lagged = 3.56 [95% CI, 1.21–10.49]; and HR 6-month lagged = 2.50 [95% CI, .91–6.84]). Current HIV RNA as a continuous variable was also associated with NHL (HR = 1.42 per log10 copies/mL [95% CI, 1.05–1.92]).
Conclusions. Our findings demonstrate a high incidence of NHL among HIV-infected patients on ART and suggest a role of HIV viremia in the pathogenesis of NHL. Earlier initiation of potent ART and maximal continuous suppression of HIV viremia may further reduce NHL risk.
PMCID: PMC4017888  PMID: 24523217
non-Hodgkin lymphoma; HIV; antiretroviral therapy; incidence; viremia
19.  Effects of Short-term Exposure to Inhalable Particulate Matter on DNA Methylation of Tandem Repeats 
There is compelling evidence that particulate matter (PM) increases lung cancer risk by triggering systemic inflammation, and leukocyte DNA hypomethylation. However, previous investigations focused on repeated element sequences from LINE-1 and Alu families. Tandem repeats, which display a greater propensity to mutate, and are often hypomethylated in cancer patients, have never been investigated in individuals exposed to PM. We measured methylation of three tandem repeats (SATα, NBL2, D4Z4) by polymerase chain reaction–pyrosequencing on blood samples from truck drivers and office workers (60 per group) in Beijing, China. We used lightweight monitors to measure personal PM2.5 (PM with aerodynamic diameter ≤2.5 µm) and elemental carbon (EC, a tracer of PM from vehicular traffic). Ambient PM10 data were obtained from air quality measuring stations. Overall, an interquartile increase in personal PM2.5 and ambient PM10 levels was associated with a significant covariate-adjusted decrease in SATα methylation (−1.35% 5-methyl cytosine [5mC], P = 0.01; and −1.33%5mC; P = 0.01, respectively). Effects from personal PM2.5 and ambient PM10 on SATα methylation were stronger in truck drivers (−2.34%5mC, P = 0.02; −1.44%5mC, P = 0.06) than office workers (−0.95%5mC, P = 0.26; −1.25%5mC, P = 0.12, respectively). Ambient PM10 was negatively correlated with NBL2 methylation in truck drivers (−1.38%5mC, P = 0.03) but not in office workers (1.04%5mC, P = 0.13). Our result suggests that PM exposure is associated with hypomethylation of selected tandem repeats. Measuring tandem-repeat hypomethylation in easy-to-obtain blood specimens might identify individuals with biological effects and potential cancer risk from PM exposure.
PMCID: PMC4426495  PMID: 24436168
Air pollution; epigenetics; epidemiology
20.  Pleiotropic effects of genetic risk variants for other cancers on colorectal cancer risk: PAGE, GECCO, and CCFR Consortia 
Gut  2013;63(5):800-807.
Genome-wide association studies (GWAS) have identified a large number of single nucleotide polymorphisms (SNPs) associated with a wide array of cancer sites. Several of these variants demonstrate associations with multiple cancers, suggesting pleiotropic effects and shared biological mechanisms across some cancers. We hypothesized that SNPs previously associated with other cancers may additionally be associated with colorectal cancer. In a large-scale study, we examined 171 SNPs previously associated with 18 different cancers for their associations with colorectal cancer.
We examined 13,338 colorectal cancer cases and 40,967 controls from three consortia: Population Architecture using Genetics and Epidemiology (PAGE), Genetic Epidemiology of Colorectal Cancer (GECCO), and the Colon Cancer Family Registry (CCFR). Study-specific logistic regression results, adjusted for age, sex, principal components of genetic ancestry, and/or study specific factors (as relevant) were combined using fixed-effect meta-analyses to evaluate the association between each SNP and colorectal cancer risk. A Bonferroni-corrected p-value of 2.92×10−4 was used to determine statistical significance of the associations.
Two correlated SNPs— rs10090154 and rs4242382—in Region 1 of chromosome 8q24, a prostate cancer susceptibility region, demonstrated statistically significant associations with colorectal cancer risk. The most significant association was observed with rs4242382 (meta-analysis OR=1.12; 95% CI: 1.07–1.18; P=1.74×10−5), which also demonstrated similar associations across racial/ethnic populations and anatomical sub-sites.
This is the first study to clearly demonstrate Region 1 of chromosome 8q24 as a susceptibility locus for colorectal cancer, thus adding colorectal cancer to the list of cancer sites linked to this particular multi-cancer risk region at 8q24.
PMCID: PMC3918490  PMID: 23935004
colorectal cancer; pleiotropy; genome-wide association study; single nucleotide polymorphism
21.  Genome-Wide Association Study of Breast Cancer in Latinas Identifies Novel Protective Variants on 6q25 
Nature communications  2014;5:5260.
The genetic contributions to breast cancer development among Latinas are not well understood. Here, we carry out a genome-wide association study of breast cancer in Latinas and identify a genome-wide significant risk variant, located 5’ of the Estrogen Receptor 1 gene (ESR1) (6q25 region). The minor allele for this variant is strongly protective (rs140068132: OR 0.60, 95%CI 0.53-0.67, P=9×10−18), originates from Indigenous Americans, and is uncorrelated with previously reported risk variants at 6q25. The association is stronger for estrogen receptor negative disease (OR 0.34 95% CI 0.21-0.54) than estrogen receptor positive disease (OR 0.63 95% CI 0.49-0.80) (P heterogeneity=0.01) and is also associated with mammographic breast density, a strong risk factor for breast cancer (P=0.001). rs140068132 is located within several transcription factor binding sites and electrophoretic mobility shift assays with MCF-7 nuclear protein demonstrate differential binding of the G/A alleles at this locus. These results highlight the importance of conducting research in diverse populations.
PMCID: PMC4204111  PMID: 25327703
22.  Blood Telomere Length Attrition and Cancer Development in the Normative Aging Study Cohort 
EBioMedicine  2015;2(6):591-596.
Accelerated telomere shortening may cause cancer via chromosomal instability, making it a potentially useful biomarker. However, publications on blood telomere length (BTL) and cancer are inconsistent. We prospectively examined BTL measures over time and cancer incidence.
We included 792 Normative Aging Study participants with 1–4 BTL measurements from 1999 to 2012. We used linear mixed-effects models to examine BTL attrition by cancer status (relative to increasing age and decreasing years pre-diagnosis), Cox models for time-dependent associations, and logistic regression for cancer incidence stratified by years between BTL measurement and diagnosis.
Age-related BTL attrition was faster in cancer cases pre-diagnosis than in cancer-free participants (pdifference = 0.017); all participants had similar age-adjusted BTL 8–14 years pre-diagnosis, followed by decelerated attrition in cancer cases resulting in longer BTL three (p = 0.003) and four (p = 0.012) years pre-diagnosis. Longer time-dependent BTL was associated with prostate cancer (HR = 1.79, p = 0.03), and longer BTL measured ≤ 4 years pre-diagnosis with any (OR = 3.27, p < 0.001) and prostate cancers (OR = 6.87, p < 0.001).
Age-related BTL attrition was faster in cancer cases but their age-adjusted BTL attrition began decelerating as diagnosis approached. This may explain prior inconsistencies and help develop BTL as a cancer detection biomarker.
•Normal, age-related telomere attrition is faster in subjects who later developed cancer.•Telomere attrition began decelerating before cancer diagnosis, resulting in longer telomeres 3–4 years pre-diagnosis.•Longer telomeres measured within four years of diagnosis were associated with all-cancer incidence.
PMCID: PMC4535161  PMID: 26288820
Telomere; Longitudinal study; Cancer incidence
23.  Genome-wide association study of breast cancer in Latinas identifies novel protective variants on 6q25 
Nature Communications  2014;5:5260.
The genetic contributions to breast cancer development among Latinas are not well understood. Here we carry out a genome-wide association study of breast cancer in Latinas and identify a genome-wide significant risk variant, located 5′ of the Estrogen Receptor 1 gene (ESR1; 6q25 region). The minor allele for this variant is strongly protective (rs140068132: odds ratio (OR) 0.60, 95% confidence interval (CI) 0.53–0.67, P=9 × 10−18), originates from Indigenous Americans and is uncorrelated with previously reported risk variants at 6q25. The association is stronger for oestrogen receptor-negative disease (OR 0.34, 95% CI 0.21–0.54) than oestrogen receptor-positive disease (OR 0.63, 95% CI 0.49–0.80; P heterogeneity=0.01) and is also associated with mammographic breast density, a strong risk factor for breast cancer (P=0.001). rs140068132 is located within several transcription factor-binding sites and electrophoretic mobility shift assays with MCF-7 nuclear protein demonstrate differential binding of the G/A alleles at this locus. These results highlight the importance of conducting research in diverse populations.
Genome-wide association studies (GWAS) have revealed gene variants associated with breast cancer, but their association with breast cancer development in Latinas is not clear. Here, the authors carry out a GWAS of breast cancer in Latinas and identify a significant protective variant of Indigenous American origin in the 6q25 region.
PMCID: PMC4204111  PMID: 25327703
24.  Impact of folic acid fortification on global DNA methylation and one-carbon biomarkers in the Women's Health Initiative Observational Study cohort 
Epigenetics  2013;9(3):396-403.
DNA methylation is an epigenetic mechanism that regulates gene expression and can be modified by one-carbon nutrients. The objective of this study was to investigate the impact of folic acid (FA) fortification of the US food supply on leukocyte global DNA methylation and the relationship between DNA methylation, red blood cell (RBC) folate, and other one-carbon biomarkers among postmenopausal women enrolled in the Women's Health Initiative Observational Study. We selected 408 women from the highest and lowest tertiles of RBC folate distribution matching on age and timing of the baseline blood draw, which spanned the pre- (1994–1995), peri- (1996–1997), or post-fortification (1998) periods. Global DNA methylation was assessed by liquid chromatography-tandem mass spectrometry and expressed as a percentage of total cytosine. We observed an interaction (P = 0.02) between fortification period and RBC folate in relation to DNA methylation. Women with higher (vs. lower) RBC folate had higher mean DNA methylation (5.12 vs. 4.99%; P = 0.05) in the pre-fortification period, but lower (4.95 vs. 5.16%; P = 0.03) DNA methylation in the post-fortification period. We also observed significant correlations between one-carbon biomarkers and DNA methylation in the pre-fortification period, but not in the peri- or post-fortification period. The correlation between plasma homocysteine and DNA methylation was reversed from an inverse relationship during the pre-fortification period to a positive relationship during the post-fortification period. Our data suggest that (1) during FA fortification, higher RBC folate status is associated with a reduction in leukocyte global DNA methylation among postmenopausal women and; (2) the relationship between one-carbon biomarkers and global DNA methylation is dependent on folate availability.
PMCID: PMC4053458  PMID: 24300587
DNA methylation; folate; folic acid fortification; RBC folate; one-carbon biomarkers; choline; vitamin B12; homocysteine; postmenopausal women; Women's Health Initiative
25.  Maternal Glucose during Pregnancy and after Delivery in Women with Gestational Diabetes Mellitus on Overweight Status of Their Children 
BioMed Research International  2015;2015:543038.
Objective. To examine the association of maternal glycemia during pregnancy and after delivery with anthropometry in the offspring of mothers with gestational diabetes mellitus (GDM). Methods. A total of 1,263 GDM mothers and their children finished the health survey at 1–5 years after delivery. Results. Offspring of GDM mothers who were diagnosed with diabetes during pregnancy had higher prevalence of overweight, higher mean weight for height Z scores, and higher mean BMI for age Z scores at 1–5 years old than the offspring of GDM mothers who were diagnosed with impaired glucose tolerance (IGT) during pregnancy. Offspring of GDM mothers who developed diabetes 1–5 years after delivery had higher mean values of Z scores for weight for height and BMI for age at 1–5 years old than the offspring of GDM mothers who had normal glucose or prediabetes after delivery. Conclusions. Offspring of GDM mothers who were diagnosed with diabetes during pregnancy or after delivery had an increased risk of childhood overweight or weight gain at 1–5 years old compared with children of GDM mothers with IGT during pregnancy or with normal glucose or prediabetes after delivery.
PMCID: PMC4352735  PMID: 25802854

Results 1-25 (83)