ALDH1A1 and lung cancer: RT-qPCR and IHC staining assays here demonstrated that the expression levels of lung cancer markers and cancer stem cell features of lung cells, including Kras, c-Myc, ABCG2, OCT4, SOX2 and Aldh1a1 [18, 36–38], were markedly increased in lung tissues of PM2.5-challenged mice.