While H2S appears to favor cancer cell survival and proliferation by stimulating cell bioenergetics and neo-angiogenesis, among other effects, sulfane sulfur species could potentiate the cell antioxidant defense system, by both scavenging free radicals and enhancing the activity of antioxidant enzymes such as glutathione peroxidase, glutathione reductase and superoxide dismutase [79,80]. Here, GSR is linked to cancer.