The effects of selection by oxygen levels on prostate cancer cells.

摘要

Prostate cancer is both the second most frequently diagnosed cancer among men as well as the second leading cause of cancer related death in men. The lack of therapeutic options currently available for this disease prompted the development of a new in vitro model system for the study of prostate cancer. In this dissertation, different O2 levels were used as a selective agent during growth of the DU145 prostate cancer cell line to develop three cell lines that grow in normoxic (4%), hyperoxic (21%), or hypoxic (1%) O2 conditions. After long-term selection by O 2 level, these cell lines had differences in growth characteristics, O2 consumption capacities, and mitochondrial morphology unaccompanied by changes in antioxidant enzymes (AEs) directly involved in O2 metabolism. However, transient increases in O2 tension revealed differential regulation of both superoxide and peroxide detoxifying AEs. We found cells grown in 4% O2 demonstrated a more invasive phenotype correlating with an overall shift in redox potential towards reduction as well as unique patterns of mitochondrial coupling and functionality, respiration, and ROS production in each cell line. Our results demonstrated the presence of a complex network linking O2 niche, ROS production, pH i, glycolysis, and mitochondrial coupling that may impact the cellular response to oxidative stress. Our results demonstrated that hyperoxic cells regulate both O2·- and H2O 2 while hypoxic cells solely regulate O2·- . In contrast, resistance to oxidative stress in cells selected by tissue normoxia occurs through regulation of H2O2 levels via uncoupling of the dismutase reactions of MnSOD and H2O 2 consumption pathways. This model system not only explains the array of responses to oxidative stress observed in many studies, it also provides valuable hypotheses relating to the reactive oxygen species (ROS) resistant phenotype of hypoxic tumor cells, the biology of invasive/malignant tumor cells, and the detrimental affects of increased MnSOD activity in oxidative stress.