For instance, the flow cytometry cell sorting (FACS)-enriched CD133+ cells from human NSCLC tissues and lung cancer cell lines exhibited self-renewal, drug- and radiotherapy resistance and co-expressed ABCG2, a multidrug resistance marker and octamer-binding transcription factor 4 (Oct4), a marker for stem cell pluripotency [41]. Here, ABCG2 is linked to lung cancer.