Abstract B22: The role of e-cigarette exposure on pulmonary epithelial cell transformation

Despite a strong correlation between cigarette smoking and the onset of lung cancer, the prevalence of smoking still remains high. The electronic cigarette (ECIG) is designed to deliver nicotine without combusting tobacco. Since nicotine is widely considered the addictive component in tobacco with limited ability to initiate cancer, ECIGs have been advertised to be a safer alternative to tobacco cigarettes. However, the potential health risks and 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. In anchorage independent growth assays, the in vitro correlate of malignant transformation, we found enhanced colony growth in the HBEC-P53/KRAS cells following a 12-day treatment with high concentrations of ECIG-conditioned media compared to the untreated and low concentration treatment groups. We next assessed the effect of ECIG and exposure on cell invasion using three-dimensional air-liquid interface (ALI) models. HBEC-P53/KRAS cells exhibited invasion-associated morphological changes following a 12-day treatment with the high conditioned media, including increased proliferation, diminished cell-cell cohesion and the appearance of cells percolating out of and breaching the modified basement membrane. Finally, to identify the biological impact of in vitro ECIG exposure in HBECs, we profiled the gene expression of P53/KRAS cells following a 96-hour exposure to ECIG- or tobacco cigarette (TCIG)-conditioned media. We found that epithelial cells exposed to clinically relevant concentrations of ECIG vapor-conditioned media have a gene expression pattern similar to those exposed to TCIG smoke-conditioned media and whole cigarette smoke. Rank-rank hyper-geometric overlap (RRHO) analysis indicated that differential expression - based ranked genes in TCIG and ECIG exposed groups were consistently overlapped at significant levels. There were 263 differentially expressed genes in the cells treated with high ECIG media versus untreated control. Annotations of the identified genes by the Molecular Signature database revealed several enriched biological pathways involved in malignant transformation and epithelial-mesenchymal transition (EMT). We have compared the resulting list of genes to publicly available microarray datasets and identified several transformation-related gene candidates. We are in the process of evaluating their contribution to ECIG-induced dissemination and carcinogenesis in vitro and in vivo. These studies will determine the impact of ECIG exposure on lung carcinogenicity and provide needed scientific guidance to the FDA regarding the physiologic effects of ECIGs. These studies were supported by funding from the following: NIH/NCI #U01CA152751 (SMD, TCW), NCI #U01CA152751-S1 (SMD, TCW, SJP), NCI #U01CA152751-AS (SMD, KK), NCI #T32-CA009120-36 (SMD, SJP, PCP), NIH/NHLBI #T32HL072752 (SMD, EL), University of California Tobacco-Related Disease Research Program (TRDRP) #18FT-0060 (TCW), TRDRP #20KT-0055 (TCW), Prevent Cancer Foundation (SJP), Lung Cancer SPORE (P50CA70907, JDM, JEL) Citation Format: Stacy J. Park, Tonya C. Walser, Linh M. Tran, Catalina Perdomo, Teresa Wang, Long-Sheng Hong, Paul C. Pagano, Elvira L. Liclican, Jill E. Larsen, Kostyantyn Krysan, Michael C. Fishbein, John D. Minna, Marc E. Lenburg, Spira Avrum, Steven Dubinett. The role of e-cigarette exposure on pulmonary epithelial cell transformation. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr B22.