The present 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 indicate a major role of p53-family proteins in conferring a stem-like cell phenotype and radioresistance to NSCLC cells that are associated with ABCG2 overexpression. This evidence concerns the gene ABCG2 and cancer.