SOD2 and cancer: There was no significant differences of G2/M phase progression and cyclin B1 expression in the NIH3T3 cells (Additional file 3: Figures S3B-S3D), suggesting that induction of G2/M arrest by BTG2 overexpression might be limited to cancer cells which usually contain a defect in G1/S checkpoint, BTG2-mediated MnSOD induction was preceded to p21WAF1 expression (Figure 6D) and the expression of p21WAF1 was evident both in the RNA and protein levels (Figure 6E and Additional file 4: Figure S4) after transduction and transfection of BTG2 gene in HeLa cells.