It was reported
that the formation of reactive oxygen species (ROS), such
as hydrogen peroxide (H2O2) and superoxide anion radicals,
by human polymorphonuclear leucocytes (PMNs) stimulated
by 12-O-tetradecanoylphorbol-13-acetate (TPA) induces
oxidative DNA damage in vitro and in vivo (31, 32).
TPA is a potent tumor promoter. The inhibition of H2O2 formation
is a characteristic of many chemopreventive agents
including tamoxifen, sarcophytols and epigallocatechin gallate
(33–35). Some of these compounds are antioxidants and
inhibitors of tumor promotion (33, 34).