Kattan et al. (39) has demonstrated the MnSOD up-regulated tumour cell growth and invasive properties of oestrogen-independent metastatic breast cancer cells; however, the present study showed that the MnSOD expression level in BCSCs was higher than that of both MCF-7 and MDA-MD-231 cell lines, although its ERα1 expression was similar to MCF-7 cells. This evidence concerns the gene SOD2 and breast carcinoma.