Abstract C58: The gene expression and functional impact of E-cigarette exposure on pulmonary epithelial transformation

Abstract

Abstract Lung cancer is the leading cause of cancer deaths in the United States. Despite a strong correlation between cigarette smoking and the onset of lung cancer, the prevalence of smoking still remains high. Significant reduction or elimination of the use of combustible tobacco products would substantially lower tobacco-caused morbidity and mortality. The electronic cigarette (ECIG) is a battery-powered electronic nicotine delivery system (ENDS) designed to deliver nicotine without combusting tobacco. ECIGs are widely believed to be a safer alternative to tobacco cigarettes (TCIG), however, the toxicity and potential carcinogenicity of ECIGs have not previously been evaluated. In this study, we assess the impact of ECIG exposure on the carcinogenic potential of immortalized human bronchial epithelial cells on a background of silenced p53 and activated KRAS (H3mut-P53/KRAS). This model is utilized because p53 and KRAS mutations are often observed in the airway of current and former smokers at risk for lung cancer. The epithelial cells were exposed to a low and high nicotine concentration of ECIG vapor- or TCIG smoke-conditioned media. The lower nicotine concentration was selected to mimic plasma nicotine levels in ENDS users and did not demonstrate toxic or anti-proliferative effects on the cells. The higher concentration was chosen to represent the anticipated nicotine levels to which the epithelial cells of smokers are actually exposed. In anchorage independent growth assays, the in vitro correlate of malignant transformation, we found enhanced colony growth in the H3mut-P53/KRAS cells following a 10-day treatment with the high nicotine concentration of ECIG- and TCIG-conditioned media compared to the untreated and low nicotine treatment groups. We next assessed the effect of ECIG and TCIG exposure on cell invasion using three-dimensional air-liquid interface (ALI) models. While treatment with the low nicotine concentration of ECIG-conditioned media did not induce invasion-associated morphological changes, cells treated with the low nicotine concentration of TCIG-conditioned media exhibited slightly invasive behavior by breaching the modified basement membrane and invading through the field of fibroblasts/collagen. At baseline, H3mut-P53/KRAS cells exhibit invasive behavior in the ALI model, due to the downstream effects of P53 silencing and KRAS activation. Treatment of H3mut-P53/KRAS cells with the low nicotine concentration of ECIG- and TCIG-conditioned media did not further enhance the degree of invasion observed in the untreated group. We will next examine the effect of the high nicotine concentration on cell invasion. In addition, we are currently evaluating gene expression profiles by microarray of H3mut-P53/KRAS cells exposed to high and low nicotine concentrations of ECIG-conditioned media. This will directly evaluate the impact of ECIGs on carcinogenicity-related gene expression signatures established in previous and ongoing clinical investigations. These studies will determine the impact of ECIG exposure on lung carcinogenicity, which will provide needed scientific guidance to the FDA regarding the physiologic effects of ECIGs. These studies were supported by the NIH/NCI #U01CA152751-S1 (SMD, AS, MEL, TCW) and NIH/NHLBI #T32HL072752 (SJP). Citation Format: Stacy J. Park, Tonya C. Walser, Catalina Perdomo, Paul P. Pagano, Daniel Brass, Elvira L. Liclican, Kostyantyn Krysan, Marc E. Lenburg, Avrum Spira, Steven M. Dubinett. The gene expression and functional impact of E-cigarette exposure on pulmonary epithelial transformation. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr C58.