Long-Term Adaptation of Lung Tumor Cell Lines with Increasing Concentrations of Nitric Oxide Donor

The free radical nitric oxide (NO) is known to play an important role in the biology of human cancers, including lung cancer. However, it is still not clear how elevated amounts of nitric oxide affect tumor development and propagation. Herein we develop an in vitro model system to study these effects in lung tumor cells. Two cell lines—one human lung adenocarcinoma (A549) and one mouse adenocarcinoma (LP07) cell line—were adaptively grown in increasing concentrations of the NO donor DETA-NONOate over several months. Both cell lines were successfully adapted to high levels of NO (HNO). Experiments validated the adaptation occurred as a result of the exogenous NO produced by the DETA-NONOate, and was not merely a response to the chemical composition of DETA-NONOate. No morphological differences were observed between cells that were adapted to the HNO and cells which did not undergo the adaptation process (i.e., "parent cells"). Parent cells were unable to survive when placed directly in media containing high levels of DETA-NONOate, suggesting that the adapted cells underwent a biological change enabling them to survive and grow in a HNO environment. The adapted cells were found to grow faster than the parent cells under both normal growth conditions and stressful growth conditions (serum-less media, growth on soft agar) even when the DETA-NONOate was removed from the HNO culture media. These adapted cell lines can serve as a novel tool for use in future experiments designed to better understand the role nitric oxide plays in lung cancer.