We first measured the IC50 and p53 transcriptional function in response to 5-FU exposure in three human breast cancer cell lines with different p53 statuses: MCF-7 (WT-p53), MDA-MB-231 (R280K mut-p53), and MDA-MB-468 (R273H mut-p53) (18). The gene discussed is TP53; the disease is breast carcinoma.