In this regard, our data add value to the debated p53–MDR relationship in cancer by indicating that p53 status affects ABCG2 expression in cells surviving after MFR and point to a major role of p53 in conferring a stem-like cell phenotype and radioresistance to NSCLC cells that is associated with ABCG2 overexpression. The gene discussed is ABCG2; the disease is cancer.