A. Average MnSOD protein levels by genotype. Each point represents the average MnSOD expression for each cell line (n=3) and the bar is the average of all three cell lines. The ala/ala cell lines analyzed as a group had significantly more MnSOD protein expression that the val/val cell lines (p<0.05). B. MnSOD protein expression in individual cell lines (*MCF7 and T47D are significantly different from ZR75-1, p<0.01). C. MnSOD protein adjusted for mitochondrial density represented by porin protein levels (*p<0.05 versus MCF-7 and T47D). D. MnSOD enzymatic activity (*p<0.05 versus MCF-7, T47D, ZR-75-30, and MDA-MB-231, **p<0.05 versus ZR-75-30). E. MnSOD protein corrected for MnSOD mRNA expression (p=0.08). All experiments were completed in triplicate (n=3 ± SD)