Superfund Research Program
Molecular Epidemiology Core
Project Leader: Robert C. Millikan
Grant Number: P42ES005948
Funding Period: 1995 - 2006
Dr. Millikan and his research team built a repository of immortalized lymphocyte cell lines that have been characterized for a number of genotypes and phenotypes of interest. Cell lines and fresh lymphocytes were collected from breast cancer patients and controls in a hospital-based case-control study (LCCC 9830). The total number of Epstein-Barr virus (EBV) immortalized lymphocyte B-cell lines is 559. Fresh lymphocytes and cell lines were used by Dr. Nakamura and other investigators in Project 1, DNA Adducts as Biomarkers of Exposure (J.A. Swenberg, PI), to measure indices of oxidative DNA damage. Lymphocytes and cell lines were assayed for a number of phenotypes related to DNA repair, including apurinic sites and markers chromosomal instability. The EBV-immortalized cell lines represent an important resource for future investigations, and have been used by several investigators to explore the relationship between genetic susceptibility and health outcomes. The researchers found that the XRCC1 codon 280 His allele was associated with higher levels of DNA damage following MMS exposure, as well as higher levels of endogenous AP sites. Several other base excision repair (BER) gene polymorphisms were also related to increased levels of oxidative damage.
The research team also developed a panel of genotyping assays related to several pathways of interest for Projects 1 and 3. The genetic polymorphisms are related to DNA repair (five BER genes, eight NER genes, five DSB genes, two Direct Repair genes); oxidative metabolism (GSTM1, GSTT1, GSTP1, MnSOD, MPO); carcinogen metabolism (CYP1B1, CYP3A4, CYP1A1 and eight other CYP genes, two acetyltransferase genes NAT1 and NAT2, two glucouronyl transferase genes, UGTIA1 and UGT1A7; and NQ01 among others). Cell lines were genotyped for each of the variants of interest. DNA samples collected from epidemiologic studies of breast cancer, colon cancer, and malignant melanoma were genotyped for the same variants. The researchers also consulted with several investigators on the best methods for extracting DNA and conducting genotyping using buccal cell swabs and mouthwash samples.
The researchers examined the genetic polymorphisms in the panel developed using DNA collected from several epidemiologic studies. Increased risk was found for breast cancer among person with two or more variants in these BER genes. Similarly, participants with three or more NER gene polymorphisms, and two or more DSB gene variants were at increased risk of breast cancer and malignant melanoma. Gene-environment interactions were observed between these polymorphisms and radiation exposure as well as smoking. These results provide important proof-of-principle for the importance of exploring genotype-phenotype correlations, and represent empirical evidence for multi-gene models for disease susceptibility. Results were presented at an invited presentation at the American Association for Cancer Research meeting in March, 2004.
The Core researchers also assisted SBRP investigators with power calculations, sample design, and IRB applications. Especially pertinent has been advice on complying with new HIPAA regulations.