Generation of cell lines with altered SOD2 expression and enzymatic activity results in changes of proliferation rates. (A) Western blot showing SOD2 expression in cell lines with SOD2 overexpression (LP-1, KMS-11, and OPM-2) and in OPM-2 infected with an shRNA directed against SOD2. Actin serves as the loading control. (B) Measurement of SOD enzymatic activity in the engineered cell lines. The experiment was preformed in triplicate with standard error shown. *P < .05; **P < .005 as determined by Student t test. (C) Proliferation rates of the myeloma cell lines were measured by tritiated thymidine incorporation. There is an inverse correlation with proliferation rates and SOD2 expression. The experiment was preformed in triplicate and standard error is shown. (D) Proliferation rates in the altered cell lines were determined by thymidine incorporation. The experiment was preformed in triplicate and standard error is shown. *P < .005.