SOD1 and breast cancer: These expressed high SOD1 mRNA and protein levels (Figure 3A,B and Figure S5), and showed rescued superoxide levels compared to mock transfected cells, as determined by staining with the cell-permeating probe DHE after exposition with the conditioned medium from N202.1A breast cancer cells, used as a prototypic tumor cell line able to induce oxidative stress in the endothelium (Figure 3C).