SOD2 and breast cancer: In human breast cancer cells, PN prevented the development of resistance to mitoxantrone and doxorubicin by inhibition of overexpression of proteins involved in the protection against oxidative stress, e.g., manganese superoxide dismutase (MnSOD) and other proteins that support the survival of cancer cells and favor drug resistance, including heat-shock proteins 70 (HSP70), BCL-2 and P-glycoprotein [117].