TP53 and breast cancer: Since we had previously determined Bax and Bcl-2 protein levels, we also decided to evaluate p53 protein expression following a 24 h incubation with the selenoesters in this study (EDAG-1 and EDAG-8) and cisplatin, using concentrations of 0.5 and 1 μM, in breast cancer cells (MCF-7 and MDA-MB-231).