SOD2 and ovarian cancer: Figure 7A shows that a combination treatment of MnSOD siRNA with DOX and PTX induced 2.2 and 6.5% apoptosis respectively in OSE, which is almost the same as that by DOX or PTX alone. OSE showed only little, if any, increase of O2•− in response to DOX and PTX treatment (Figure 7B) than did ovarian cancer cells (Figure 6B). Taken together, the above results suggest that the active generation of O2•− in ovarian cancer cells by MnSOD inhibition renders these cells more susceptible to apoptosis induced by chemotherapeutic drugs.