Human tumor cells generate reactive oxygen species: electron paramagnetic resonance spectrometric and histochemical electron microscopic investigations
Recently we demonstrated that constitutive production of hydroxyl radicals could be shown by measuring the radical spin adducts using a spin trap and electron paramagnetic resonance spectrometer. Using this method, we show that various cancer cell lines in culture generate hydroxyl radicals and that such generation is markedly decreased when desferoxamine, a specific chelator of iron, is added to the test system. This suggested that the hydroxyl radicals came from hydrogen peroxide. Using a diaminobenzidine/horseradish peroxidase histochemical system at the electron microscopic level, the hydrogen-peroxide-dependent formation of electron-dense materials was localized to mitochondrial membranes. It is suggested that cancer cells are the result of an evolutionary process resulting in adaptation to oxidative stress and that they also constitutively generate active oxygen species, some of which may function as important growth promoting agents.