Production of hydroxyl radicals by tumor cells varies with cell type as measured by electron spin resonance spectrometry

The hydroxyl radicals produced by two adherent cell lines, a human cancer cell and a mouse fibroblast, and six suspended human leukemia cell lines at different stages of differentiation were measured by electron spin resonance (ESR) spectrometry. The concentration of hydroxyl radicals detected in these tumor cells increased in proportion to temperature and cell number. The addition of the enzymes superoxide dismutase (SOD) and catalase (which do not permeate the cell membrane), reduced the amount of hydroxyl radicals detected. SOD decreased hydroxyl radicals somewhat but catalase eliminated hydroxyl radicals almost completely. These findings suggest that hydroxyl radicals are produced extracellularly consisted primarily of H2O2 but partially from superoxide radicals. Using the human leukemia cell lines at different stages of differentiation we demonstrated that cell differentiation may correlate with hydroxyl radical production. The earlier the stage of leukemic cell differentiation the more the greater the production of hydroxyl radicals. Moreover, the ability of SOD or catalase to eliminate hydroxyl radical activity correlated inversely with leukemic cell differentiation.