Involvement of oxidative stress in tumor cytotoxic activity of hepatocyte growth factor scatter factor

In this study, we show that N-acetylcysteine (NAC), a precursor of glutathi one and an intracellular free radical scavenger, almost completely prevente d hepatocyte growth factor (HGF)-suppressed growth of Sarcoma 180 and Meth A cells, and HGF-induced apoptosis, assessed by DNA fragmentation, and incr ease in caspase-3 activity, in Sarcoma 180 cells. The reduced form of gluta thione also prevented HGF-suppressed growth of the cells as effective as NA G. Ascorbic acid partially prevented the effect of HGF, but other antioxida nts such as superoxide dismutase, catalase, and vitamin E, and the free rad ical spin traps N-t-butyl-alpha-phenylnitrone and 3,3,5,5-tetramethyl-1-pyr roline-1-oxide did not have protective effects. HGF caused morphological ch anges of the cells, many cells showing condensation and rounding, and enhan ced the generation of intracellular reactive oxygen species (ROS) as judged by flow cytometric analysis using 2',7'-dichlorofluorescein diacetate. NAC completely prevented both HGF-induced morphological changes and the enhanc ement of ROS generation in the cells. However, NAC did not prevent the HGF- induced scattering of Madin-Darby canine kidney cells. To our knowledge, th is is the first report that HGF stimulates the production of ROS, and our r esults suggest the involvement of oxidative stress in the mechanism by whic h HGF induces growth suppression of tumor cells.