E-cigarettes (electronic cigarettes that use a battery-powered system to deliver nicotine without producing smoke) are advertised as a safer alternative to tobacco cigarettes. However, very few studies have investigated how e-cigarettes affect lung function and lung cancer risk. Researchers examined human airway cells with mutations in the TP53 and KRAS genes, which are often mutated in the airways of current or former smokers at high risk of lung cancer. When the cells were exposed to e-cigarette vapor, they developed cancer-cell-like behaviors and gene expression changes very similar to what was seen when these cells were exposed to tobacco smoke. E-cigarettes may increase the risk of developing lung cancer in high-risk people, including current and former tobacco smokers.