ROLE OF MANGANESE SUPEROXIDE-DISMUTASE IN RADIOPROTECTION USING GENE-TRANSFER STUDIES

Overexpression of manganese superoxide dismutase (MnSOD) has been post ulated as one possible mechanism of radioprotection for hematopoietic cells. in this study retroviral constructs having the human MnSOD gene in both the sense and antisense orientations and the Neo(-R) gene as a selectable marker were transfected into the human erythroleukemic ce ll line K562 and the human melanoma cell line A375 by electroporation. Stably transfected K562 and A375 cells selected in G418 for 3 weeks w ere subjected to various doses of irradiation, and cell viability was assayed using a colony assay system in semisolid medium. Results demon strated that K562 cells transfected with MnSOD in the antisense orient ation displayed increased sensitivity to irradiation compared to paren tal or vector-transfected K562 cells. In contrast, A375 cells transfec ted with the sense MnSOD gene demonstrated increased resistance to irr adiation compared to parental or vector-transfected A375 cells. The ex pression of the MnSOD gene in these transfected cell lines correlates with the up- or down-modulation of radiosensitivity. Thus, increased M nSOD protein was seen in the A375 cells containing the sense MnSOD, wh ereas decreased MnSOD protein was seen in the K562 cells containing th e antisense MnSOD. These data provide evidence for the direct role of MnSOD in radioprotection using antisense gene transfer/inhibition stud ies.