KRAS and cancer: Lung adenocarcinoma (LUAD), the leading cancer killer worldwide, is mainly caused by chemical carcinogens of tobacco smoke that induce mutations of the Kirsten rat sarcoma viral oncogene homologue (KRAS) in yet unidentified pulmonary cells (Torre et al., 2015; Forbes et al., 2011; Hecht, 1999; Campbell et al., 2016; Cancer Genome Atlas Research Network, 2014).