Molecular Epidemiological Study on Passive Smoking and Estrogen Receptor Expression in Never-smokers with Non-small Cell Lung Cancer.

Background: Although sex hormones are thought to play an important role in the carcinogenesis of non-small cell lung cancer (NSCLC) in never-smokers, the causative mechanism remains unknown. Passive smoking (PS) is common among East Asian women and has been suggested to be a potential cause of the disease.

Methods: We systematically evaluated the expression of estrogen receptor (ER), the prevalence of PS, and genetic mutations using tumor samples from a prospectively registered cohort of never-smokers with lung cancer. The study enrolled 92 never-smokers with NSCLC. Expression of ERa, ERP, and progesterone receptor (PR) was examined via immunohistochemical staining (IHC). Detailed PS information was obtained through a standardized questionnaire. The cumulative dose of PS (CPS) was evaluated as a sum of the number of exposure years at home and/or in the work place.

Results: Nuclear expression of ERa, ERP, and PR was detected in 0, 14, and 3 cases, respectively. ERP was more frequently overexpressed in earlier stage cancer (p=0.043). Ninety patients (97.9%) had a PS history, and the median CPS was 47.5 years (range, 0-103 years). There was no significant correlation between the amount of PS -and ERP expression (p=0.101). Twelve patients (85.7%) had Epidermal growth factor receptor ,EGFR) mutations in 14 .tumors expressing ERP, and a trend towards an association between ERP expression and EGFR mutations (p =0.067) was -observed.

Conclusions: Nuclear expression of ERP was more frequently observed in early stage NSCLC in never-smokers.