SOD1 and neoplasm: Conversely, overexpression of the antioxidant enzymes copper/zinc superoxide dismutase (SOD1) and manganese superoxide dismutase (SOD2) in human breast cancer cell lines suppresses xenograft tumor growth ( Weydert et al., 2006), and transgenic overexpression of catalase in PyMT mice diminishes tumor invasiveness and metastasis ( Goh et al., 2011).