Molecular Markers of Lung Cancer in MAYAK Workers

Steven A. Belinsky, PhD

Lovelace Biomedical & Environmental Research Institute

关键词: Death;    Methylation;    Promoters;    Neoplasms;    Lungs;   

DOI  :  10.2172/899630
RP-ID  :  Project 2.6
RP-ID  :  FC02-98EH98028
RP-ID  :  899630

美国|英语

来源: UNT Digital Library

【 摘 要 】

The molecular mechanisms that result in the elevated risk for lung cancer associated with exposure to radiation have not been well characterized. Workers from the MAYAK nuclear enterprise are an ideal cohort in which to study the molecular epidemiology of cancer associated with radiation exposure and to identify the genes targeted for inactivation that in turn affect individual risk for radiation-induced lung cancer. Epidemiology studies of the MAYAK cohort indicate a significantly higher frequency for adenocarcinoma and squamous cell carcinoma (SCC) in workers than in a control population and a strong correlation between these tumor types and plutonium exposure. Two hypotheses will be evaluated through the proposed studies. First, radiation exposure targets specific genes for inactivation by promoter methylation. This hypothesis is supported by our recent studies with the MAYAK population that demonstrated the targeting of the p16 gene for inactivation by promoter methylation in adenocarcinomas from workers (1). Second, genes inactivated in tumors can serve as biomarkers for lung cancer risk in a cancer-free population of workers exposed to plutonium. Support for this hypothesis is based on exciting preliminary results of our nested, case-control study of persons from the Colorado cohort. In that study, a panel of methylation markers for predicting lung cancer risk is being evaluated in sputum samples from incident lung cancer cases and controls. The first hypothesis will be tested by determining the prevalence for promoter hypermethylation of a panel of genes shown to play a critical role in the development of either adenocarcinoma and/or SCC associated with tobacco. Our initial studies on adenocarcinoma in MAYAK workers will be extended to evaluate methylation of the PAX5 {alpha}, PAX5 {beta}, H-cadherin, GATA5, and bone morphogenesis 3B (BMP3B) genes in the original sample set described under Preliminary studies. In addition, studies will be initiated in SCC from workers and controls to identify genes targeted for inactivation by plutonium in this other common histologic form of lung cancer. We will examine methylation of the p16, O{sup 6}-methylguanine-DNA methyl-transferase (MGMT), and death associated protein kinase genes ([DAP-K], evaluated previously in adenocarcinomas) as well as the new genes being assessed in the adenocarcinomas. The second hypothesis will be tested in a cross-sectional study of cancer-free workers exposed to plutonium and an unexposed population. A cohort of 700 cancer-free workers and 700 unexposed persons is being assembled, exposures are being defined, and induced sputum collected at initial entry into the study and approximately 1-year later. Exposed and unexposed persons will be matched by 5-year age intervals and smoking status (current and former). The frequency for methylation of four genes that show the greatest difference in prevalence in tumors from workers and controls will be determined in exfoliated cells within sputum. These studies will extend those in primary tumors to determine whether difference in prevalence for individual or multiple genes are detected in sputum samples from high-risk subjects exposed to plutonium. Follow-up of this cohort offers the opportunity to validate these endpoints and future biomarkers as true markers for lung cancer risk.