ABCG2 and cancer: Then, the lung cancer markers and cancer stem cell features of lung cells (Kras, c-Myc, ABCG2, OCT4, SOX2 and Aldh1a1) [18, 36–38], and the tumor suppressor genes (p53 and PTEN) [39] were calculated using RT-qPCR and/or immunohistochemistry (IHC) staining.