Abstract 2765: Asbestos exposure-related DNA methylation markers: a validation study in non-small cell lung tumors

Abstract

Abstract Introduction. We have earlier explored the epigenome-wide DNA methylation in lung tumors. The study subjects, mostly smokers, consisted of lung cancer patients highly exposed to asbestos and those without exposure. We found methylation markers that associated either with sample type or exposure (asbestos or tobacco smoke) (Kettunen et al submitted). In this validation study, we focused on estimating the prevalence of the distinct methylation markers in a larger material of lung tumor patients with detailed exposure data available. Study design, subjects, and methods. We investigated the DNA methylation of selected markers in a validation set of 69 non-small cell lung cancer cases, tumor (T) and normal lung (N) from each. The patients, given a written informed consent, had been interviewed for detailed data on work and smoking history (as tobacco smoking pack-years, PY), and the pulmonary asbestos fiber counts quantified. Smoking-related methylation was studied in lung cancer groups of heavy-smokers (PYs higher than 36) vs lighter-smokers (PYs 36 or less) whereas methylation in asbestos-exposed lung tumor patients were compared with that in non-exposed lung tumor patients. DNA methylation was studied in tumor (T) and matched peripheral normal (N) lung tissue using pyrosequencing. Results. Numerous CpG positions in T vs N and eleven sites in asbestos-exposed tumors had indicated significant methylation variation (MVPs). Twenty-six differentially methylated positions (DMPs) having mean delta beta of at least 10% had been revealed in T vs N. Tobacco smoking- and asbestos exposure-related methylation sites were distinct, involving different CpG sites. We chose to validate five MVPs and four DMPs, both hypo- and hypermethylated CpG sites that were investigated using two instrumentation PSQ96MA and Pyromark Q24. The validation study set indicated good performance in pyrosequencing and we could demonstrate methylation of selected sites in relation to malignancy and exposure in this larger material. Conclusions. The central observations of the methylation showing distinct changes in relation to sample types and patients’ exposure status could be validated in a larger material. Significant methylation variation was observed in lung tumors. Citation Format: Eeva Kettunen, Kristina Stuopelytė, Hector Hernandez-Vargas, Henrik Wolff, Sisko L. Anttila, Zdenko Herceg, Sonata Jarmalaite, Kirsti Husgafvel-Pursiainen. Asbestos exposure-related DNA methylation markers: a validation study in non-small cell lung tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2765.