Lactobacilli-mediated control of vaginal cancer through specific reactive oxygen species interaction

Klebanoff et al. proposed that hydrogen peroxide-producing lactobacilli and peroxidase in the vagina of healthy women might be responsible for the prevention of vaginosis and also might exert an antitumor effect (1). Based on recent evidence on superoxide anion generation by transformed cells (2,3) and on the potential of myeloperoxidase for selective apoptosis induction in transformed cells (4), a model for specific reactive oxygen species interaction during lactobacilli-mediated tumor control in the vagina is presented here. We propose that peroxidase, which converts hydrogen peroxide into hypochlorous acid, is responsible for creating a microbicidal vaginal milieu by maintaining a balanced, non-toxic, steady state level of the microbicides H2O2 and HOCl. In case individual superoxide anion-producing transformed cells eventually appear in the mucosa they will be driven into apoptosis by interaction of HOCl with superoxide anions which leads to the generation of hydroxyl radicals. Hence selective apoptosis induction in transformed cells represents the key element of lactobacilli-mediated antitumor defense. Since papilloma virus infected cells are resistant to this pathway of apoptosis induction, they are plausible candidates for circumvention of lactobacilli-mediated control of oncogenesis. (C) 2001 Harcourt Publishers Ltd.