The differential NF-kB modulation by S-adenosyl-L-methionine, N-acetylcysteine and quercetin on the promotion stage of chemical hepatocarcinogenesis.

S-adenosylmethionine (SAM), N-acetylcysteine (NAC) and quercetin exhibit a chemoprotective effect. Likely this effect is mediated by counteracting, oxidative stress and NF-kB activation. To test this hypothesis F344 rats were subjected to hepatocarcinogenesis with or without antioxidants. NAC decreased foci in number and area, SAM and quercetin decreased area. Lipid-peroxidation was decreased by antioxidants, but only SAM increased glutathione. SAM, in its regulation from IKK downwards, abolished the NF-kB activation. NAC decreased IKK and IkB-a phosphorylation, and Rel-A/p65 and NF-kB binding, though the last two were affected with less intensity compared to the NF-kB inhibitor. Quercetin decreased Rel-A/p65, without modifying upstream signalling. Although all antioxidants inhibited oxidative stress as shown by reduction of lipid peroxidation, not all exerted the same effect on NF-kB signalling pathway and only SAM increased GSH. The mechanisms exerted by SAM in the reduction of foci makes this compound a potential liver cancer therapeutic agent.