The purpose of this proposal is to characterize the levels of superoxide dismutase (SOD) in various normal and malignant in vitro cells. We have found that certain chemical-transformed rodent cells have low MnSOD activities and low amounts of immunoreactive MnSOD protein. In contrast, virally-transformed human cells were found to have low MnSOD activity, but normal amounts of immunoreactive protein. These studies have suggested that the MnSOD activity can be low in tumor cells because (1) the amount of MnSOD protein is low, (2) the MnSOD protein is inactive, or (3) both. The first goal of the proposed research is to determine if the differences noted above between different cells is due to the inducing agent (viral vs. chemical) or due to the different species. To meet this goal, we will characterize the levels of MnSOD activity and immunoreactive protein in a variety of rodent and human malignant and normal tissue culture cells. We will also determine the levels of MnSOD specific mRNA in these cell systems. These studies, when correlated with protein levels, will define the transcriptional activity of the MnSOD gene and the translation of the mRNA message. Our last goal will be to investigate the MnSOD gene in neoplastic cells and their normal cell counterparts. Using Southern transfer and hybridization techniques, we will investigate changes in MnSOD gene copy number in the neoplastic cell and determine if there are any gross rearrangements in the gene. These studies will define the molecular events leading to alterations of SOD activities in neoplastic cells.