Grantee Research Project Results
2011 Progress Report: Exposure Assessment for Childhood Leukemia
EPA Grant Number: R834511C002Subproject: this is subproject number 002 , established and managed by the Center Director under grant R834511
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for Integrative Research on Childhood Leukemia and the Environment - 2015
Center Director: Metayer, Catherine
Title: Exposure Assessment for Childhood Leukemia
Investigators: Buffler, Patricia , Rappaport, Stephen M.
Institution: University of California - Berkeley
EPA Project Officer: Hahn, Intaek
Project Period: September 25, 2009 through September 24, 2015
Project Period Covered by this Report: September 25, 2010 through September 24,2011
RFA: Children's Environmental Health and Disease Prevention Research Centers (with NIEHS) (2009) RFA Text | Recipients Lists
Research Category: Children's Health , Human Health
Objective:
The proposed new Children's Environmental Health Center based at the University of California, Berkeley is designed to examine the effects of in utero and early life exposure to potentially carcinogenic chemicals present in homes (i.e., pesticides, tobacco-related contaminants, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs)), and genetic and epigenetic factors and their interplay in the development of childhood leukemia. The proposed Center, referred to as Center for Interdisciplinary Research on Childhood Leukemia and the Environment (CIRCLE), includes three Research Projects and two Cores.
Project 2: Exposure Assessment for Childhood Leukemia will assess carcinogen exposures, based upon analysis of house dust and blood specimens, with special interest in tobacco-related contaminants, PCBs, and PBDEs.
Progress Summary:
Specific Aim 1: Measure cotinine, polychlorinated biphnyls (PCBs), and polybrominated diphenylethers (PBDEs) in serum samples obtained from 250 childhood leukemia cases at diagnosis. Estimate correlations in analyte levels between serum and house dust samples.
No activities were conducted on this aim in Year 2.
Specific Aim 2: Investigate effects of time and seasonality on house dust levels of PBDEs.
- Measure levels of PBDEs in the 500 household-dust samples (original and repeat dust samples from each of 250 households). Repeat dust sampling and measurements of nicotine, PAHs and, PCBs will be conducted under NIEHS grant 1R01-ES015899-01A2.
- Use mixed-effects models of levels of PBDEs in house dust to evaluate trends, seasonality, and within-household variability.
During Year 2, we made progress on Aims 2a and 2b. Repeat dust samples have been collected in 204 households (leaving a total of 408 original and repeat samples available for proposed analyses). Using the analytical method developed in Year 1, we extracted PBDEs from 357 residential-dust samples and purified the extracts with silica gel and gel permeation chromatography in preparation for mass spectrometry. We have thus far measured 22 PBDE congeners in 143 (out of a total of 357) residential-dust samples via gas chromatography-high resolution mass spectrometry. We also developed mixed models for statistical analysis of PBDE levels in house dust and applied them to a training set obtained from another investigation of residential dust in Fresno, CA.
Specific Aim 3: Develop and apply methods for detecting and profiling human serum albumin (HAS) adducts in samples of dried blood spots (DBS) and serum.
- Develop methods for measuring HSA adducts in DBS.
- Measure profiles of HSA adducts in DBS from leukemia cases and matched controls. Compare profiles between childhood leukemia cases and controls.
- Measure profiles of HSA adducts in serum from leukemia cases at diagnosis. Compare profiles of HSA adducts from leukemia cases measured in DBS and serum.
Specific Aim 4: Identify HSA adducts observed in profiles, paying particular attention to adducts associated with leukemia status and changes from birth to diagnosis.
Specific Aim 5: Develop and apply quantitative assays for HSA adducts identified in Aim 4.
- Develop assays for isotope-dilution mass spectrometry of identified adducts.
- Investigate the stability of these adducts in DBS from control children of smoking and nonsmoking mothers.
- Quantify levels of these adducts in archived profiling samples from Aim 3 and investigate possible associations with self-reported parental smoking and house dust levels of nicotine, polycyclic aromatic hydrocarbons (PAHs), PCBs, and PBDEs.
During Year 2, we made progress on Aims 3a, 4, and 5a. With the goal of optimizing the DBS sample preparation prior to profiling HSA adducts, we developed a pressure-cycling method, which combined DBS protein extraction and trypsin digestion in one step lasting only 30 min. This resulted in comparable results to those obtained with our conventional method applied to HSA from serum, which requires overnight protein extraction followed by 6 hours of trypsin digestion. After extraction and digestion of 3-mm punches from DBS, samples were purified by off-line high-performance liquid chromatography (HPLC) and the (T3) fraction containing HSA-Cys34 adducts was collected using a reverse phase C8 column. The gradient was chosen to minimize the volume of the collected fraction and thereby to maximize the concentrations of adducts in the sample. Then, liquid chromatography-selected reaction monitoring (LC-SRM) experiments were performed on the HPLC samples to detect T3-quinone adducts of selected quinones that were anticipated to be present in DBS samples. By comparing the selected reaction monitoring (SRM) extracted ion chromatograms from DBS digests with those of synthetic T3-quinone standards, the following putative identifications were assigned to analytes in the DBS samples: diol and oxidized forms of benzoquinone, naphthoquinone and phenanthrene quinone.
Significance
Leukemia is the most common type of childhood cancer. About 2,400 cases of childhood leukemia (ages 0-14 years) are diagnosed annually in the United States. The etiology of childhood leukemia is complex; confirmed clinical and epidemiologic associations explain less than 10% of childhood leukemia incidence. The results of this study are providing extremely important information regarding the contribution of various environmental, infectious, immune, and genetic factors to the risk of childhood leukemia. This Center proposes to conduct multi- and inter-disciplinary research to examine the interplay of environmental, genetic, and epigenetic factors of childhood leukemia, with a focus on children's exposure to common chemicals with strong biologic plausibility, i.e., benzene, cotinine, PAHs, PCBs, and PBDEs. Work in Year 2 tentatively identified several quinone adducts of benzene and PAHs (benzoquinone, naphthoquinone, and phenanthrene quinone) in DBS.
PBDEs are the most common brominated flame retardants in the United States; they are persistent and ubiquitous environmental contaminants. The U.S. National Toxicology Program showed that high doses of one PBDE mixture were carcinogenic in rodents. Human studies have found a suggestive relationship between another PBDE mixture in adipose tissue and the risk of non-Hodgkins lymphoma. Contact with house dust is thought to account for 80-90% of the total PBDE exposure, in large part because PBDEs originate entirely from indoor consumer products. California residents may be at particular risk to the effects of PBDEs due to the state's flammability standards that motivated increased use of PBDEs in furniture sold in California. This project will improve chemical exposure assessment using direct measures of chemicals in home dust samples and biomarkers.
Future Activities:
Specific Aim 1: Adapt and validate methods to measure cotinine, PCBs, and PBDEs in serum samples. Identify samples from 250 childhood leukemia subjects for analysis.
Specific Aim 2: Continue to analyze PBDEs in archived and repeated dust samples.
Specific Aim 3: Optimize methods for profiling HSA adducts from DBS samples. Profile HSA adducts in 3-mm punches from DBS from control children divided equally between smoking and nonsmoking mothers during pregnancy.
Specific Aim 4: Continue with identification of adducts detected in DBS samples.
Specific Aim 5: Continue with quantification of putative adducts in DBS samples from control children of smoking and nonsmoking mothers.
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R834511 Center for Integrative Research on Childhood Leukemia and the Environment - 2015 Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R834511C001 Childhood Leukemia International Consortium Studies
R834511C002 Exposure Assessment for Childhood Leukemia
R834511C003 Prenatal Exposures, DNA Methylation & Childhood Leukemia
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.