Grantee Research Project Results
2006 Progress Report: Analysis of Genotoxic Biomarkers in Children Associated with a Pediatric Cancer Cluster and Exposure to Two Superfund Sites
EPA Grant Number: CR830757Title: Analysis of Genotoxic Biomarkers in Children Associated with a Pediatric Cancer Cluster and Exposure to Two Superfund Sites
Investigators: Finette, Barry A. , O'Neill, J. Patrick , Vacek, Pamela
Current Investigators: Finette, Barry A.
Institution: University of Vermont
EPA Project Officer: Aja, Hayley
Project Period: March 1, 2003 through February 28, 2006 (Extended to December 31, 2007)
Project Period Covered by this Report: March 1, 2006 through February 28, 2007
Project Amount: $775,141
RFA: Children's Vulnerability to Toxic Substances in the Environment (2002) RFA Text | Recipients Lists
Research Category: Children's Health , Human Health
Objective:
The objective of this study is to evaluate the utility of specific biomarkers of effect and susceptibility for studying cancer risk in children following genotoxic exposures. We are determining if children from an exposed population with elevated cancer incidence have an increase in chromosome aberrations or changes in the HPRT mutational spectrum, such as: (1) an increase in frameshift mutations, reflective of exposure to anthraquinone-based dyes and styrene-acrylonitrile trimers; (2) an increase in point mutations, reflective of exposure to benzidine-based dyes, epichlorohydrin, and trichloropropane; and (3) an increase in V(D)J recombinase-mediated deletions, reflective of exposure to aromatic hydrocarbons. We are also determining if specific DNA polymorphisms in 13 carcinogen metabolizing and DNA repair enzymes are associated with increased mutagenic susceptibility to genotoxic exposure.
Approach: We are analyzing biomarkers of effect and susceptibility in exposed siblings of children in a Centers for Disease Control and Prevention (CDC)-defined pediatric cancer cluster that has been linked to transplacental and childhood exposure to contaminated groundwater from two U.S. Environmental Protection Agency (EPA)-designated Superfund sites in Dover Township, NJ. Exposure studies are focusing on the siblings of children with cancer, rather than the children with cancer, because of the genotoxic effects of cancer treatment. However, biomarkers of susceptibility are being measured in children with cancer. Biomarkers of effect (chromosomal aberrations and HPRT mutations) in the exposed siblings are being compared to measurements in unexposed children from neighboring communities. Biomarkers of susceptibility (DNA polymorphisms for carcinogen metabolizing enzymes) in the exposed siblings and unexposed children are being compared to children with cancer to determine if the latter have a different prevalence of specific metabolic genotypes. In addition, the relationships between biomarkers of effect and susceptibility in exposed siblings and unexposed children are being examined to see if the effects of exposure are modified by any of these metabolic polymorphisms. Exposures in all subjects will be evaluated from their residential and personal histories using a computer model developed by the Agency for Toxic Substances and Disease Registry (ATSDR) to estimate exposure to different water sources over time.
Progress Summary:
We have completed and published our HPRT cloning assay analysis that measured the frequency of somatic mutations (MFs) in 49 exposed siblings and 43 age/gender-matched unexposed children (Vacek, et al., 2005). These studies demonstrated that the MFs in peripheral T cells from these children were not significantly different regardless of whether results were adjusted or unadjusted for age and cloning efficiency (CE) (Residual lnMF). The observation that HPRT lnMF and residual lnMF were not significantly different does not preclude that significant genotoxic differences exist at the genomic level that would be reflected in a change in the mutational spectrum. We have just completed the mutational analysis of 376 mutant T cell isolates from 89 of the 91 individuals. Since this analysis is blinded, we are now breaking the identification numbers in order to decode these samples and proceed to our comparative spectra statistical analysis between our test groups. In addition, we have also just completed data acquisition for our chromosomal aberration studies in exposed and unexposed children as a determinant of widespread genomic damage following genotoxic exposure and cancer risk. We have competed metaphase spread fluorescence in situ hybridization (FISH) analysis on 88/91 (97%) of our projected subjects. We analyzed an average of 1,500 metaphase spreads per subject, which is greater than our initial goal of 1,000 per subject. We are currently completing our secondary independent analysis of these samples prior to breaking the identification numbers in order to decode these samples and proceed to our comparative chromosomal aberration analysis. We completed the recruitment of peripheral blood samples from affected siblings with cancer in order to complete the polymorphism studies of 26 polymorphisms in 13 metabolic genes, as outlined in specific aims 1–3. To date, we have completed the analysis of 37 polymorphisms in 121 out of 172 subjects, specifically, 29 exposed cancer cases, 49 exposed siblings, and 43 unexposed healthy controls. Analysis at the EPHX1 (T612C; Tyr113His) locus revealed a statistically significant association (p = 0.04) with the number of copies of the C allele in the exposed Toms River cancer cases, when compared to the unexposed healthy controls (Mentel-Haenszel test for linear association). EPHX1 is an epoxide hydrolase, which catalyzes the hydrolysis of epoxides from polycyclic aromatic hydrocarbons (PAHs) and aromatic amines. This enzyme is involved in both styrene and epoxy resin metabolism, contaminants from both Superfund sites in Toms River, NJ. In vitro studies have shown that this polymorphism change reduces protein concentration, and hence activity, by 40–50%. The exposed cancer cases with the C/C genotype may have less EPHX1 activity and thus may not have been able to metabolize and breakdown the epoxy and styrene compounds in the contaminated water. We also observed a borderline significant difference for the ABCB1 C3435T polymorphism (p = 0.054) between genotype prevalence among the cancer cases, compared to exposed siblings and controls. Specifically, 31.0% of the exposed cancer cases had the C/C genotype, compared to only 18.4% in the exposed siblings, while 13.8% of the cancer cases had the T/T genotype, less than half that of the siblings at 30.6%. ABCB1 is an ATP-dependent apical membrane glycoprotein, also known as P-glycoprotein, that transports a variety of drugs and toxins out of cells and is expressed in a variety of tissues, including the blood brain barrier, placenta, liver, kidneys, and intestines. This finding is quite intriguing, since this gene is expressed at the blood brain barrier and may have contributed to the elevation in central nervous system (CNS) tumors observed in the exposed group. In addition, this gene is known to protect the fetus from toxins by pumping them back out into the maternal circulation in addition to being expressed in the placenta, and thus may also play a key role in carcinogen exposure during in utero development. We will be completing the remainder of our polymorphism studies over the next few months. Continued analysis will determine the utility of metabolic polymorphisms as biomarkers for pediatric cancer risk following genotoxic exposure.
Future Activities:
During our funded extension, we will complete the remainder of our polymorphism determination and statistical analysis on the remainder of our samples from our cancer subjects. We will also complete the statistical analysis for both our mutational spectra and chromosomal aberration studies. In addition, we will perform our analysis with the ATSDR Historical Reconstruction of the Water-Distribution System Serving the Dover Township Area, New Jersey, to determine exposures to differing water sources based on subjects’ residential histories and to utilize these findings in our comparative mutational spectra and chromosome analysis. We will also prepare and submit our findings for publication. We are anticipating a minimum of three manuscripts will be submitted on these findings.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 12 publications | 1 publications in selected types | All 1 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Vacek PM, Messier T, Rivers J, Sullivan L, O'Neill JP, Finette BA. Somatic mutant frequency at the HPRT locus in children associated with a pediatric cancer cluster linked to exposure to two Superfund sites. Environmental and Molecular Mutagenesis 2005;45(4):339-345. |
CR830757 (2004) CR830757 (2005) CR830757 (2006) CR830757 (Final) |
|
Supplemental Keywords:
biomarkers, drinking water, risk assessment, human health, infants, children, genetic predisposition, hydrogeology, northeast, industry, vulnerability, sensitive population, genetics,, RFA, Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Health Risk Assessment, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Children's Health, genetic susceptability, Risk Assessment, developmental neurotoxicology, neurotoxic, sensitive populations, pediactric cancer, childhood cancer, biomarkers, computer models, developmental effects, genotoxic biomarkers, Human Health Risk Assessment, children, assessment of exposure, children's vulnerablity, residential populations, neurodevelopmental toxicity, human exposure, neurobehavioral effects, contaminated groundwater, biological markers, toxicsProgress and Final Reports:
Original AbstractThe 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.