Gene silencing of SOD2 or catalase by artificial SOD2- or catalase-specific miRNA represses growth of the transformed cells. A, artificial SOD2 miRNA reduces SOD2 expression as determined by Western blotting. B, artificial catalase miRNA reduces catalase expression as determined by Western blotting. C, cell proliferation of the transformed cells was determined following transfection of the cells with SOD2 miRNA, catalase miRNA, or the combination for the indicated times. D, colony formation of the transformed cells was determined for cells transfected with the indicated miRNA by soft agar assay.