Epidemiological studies suggested that trans-resveratrol, a wine grape component, could prevent malignant tumor development. This compound also demonstrated cytostatic and cytotoxic effects on tumor cells in vitro. To obtain trans-resveratrol derivatives with a better cellular uptake and enhanced antiproliferative effects, we synthesized a triacetate derivative as well as an oligomer, e-viniferin and its acetylated form, e-viniferin penta-acetate. We also obtained vineatrol, a wine grape shoot extract that associates several polyphenols that may act synergistically, including trans-resveratrol and e-viniferin. We show here that resveratrol triacetate and vineatrol are as efficient as trans-resveratrol in inducing the accumulation of human colon cancer cells in early S phase of the cell cycle. This effect is associated with a nuclear redistribution of cyclin A and the formation of a cyclin A/cyclindependent kinase 2 complex whose kinase activity is increased. In contrast, e-viniferin and its acetylated form do not demonstrate any significant activity on these cells when tested alone. Interestingly, resveratrol triacetate and vineatrol dramatically enhance 5-Fluoro-Uracil-mediated inhibition of colon cancer cell proliferation. Thus, acetylated derivatives of resveratrol have retained the cytostatic and cytotoxic activities of the parental molecule and thus deserve to be tested as chemosensitizers in animal models. '
UICCKey words: colon cancer; cell cycle; polyphenols; resveratrol; vineatrol; chemosensitization Epidemiological studies suggested that the polyphenol resveratrol (trans-3,4 0 ,5-trihydroxystilbene) was one of the main wine grape components that protect from vascular diseases, neurodegenerative processes and cancers. 1 The ability of resveratrol to prevent the occurrence of carcinomas was related to the inhibition of tumor cell cycle 2,3 and induction of tumor cell death. 4,5 In addition, there is compelling in vitro evidence that trans-resveratrol behaves as a chemosensitizer when combined with cytotoxic drugs, 6 cytokines 7 and other polyphenols such as quercetin, apigenin and genistein. 8,9 Resveratrol is probably not the only bioactive compound present in the grape wine. Oligomers of resveratrol such as viniferins, were suggested to block the proliferation of several tumoral cell lines 10-12 and a vineatrol preparation containing both trans-resveratrol and e-viniferin exhibited a greater antiproliferative effect on malignant cell lines than each compound tested separately. 13,14 Lipophilic derivatives were obtained through esterification of the hydroxyl functions with aliphatic molecules, which improved their intestinal absorption and cell penetration. 15,16 Acetylation of the phenolic compounds could also favor their absorption, as demonstrated for catechins. 17 Acetylated derivatives of polyphenols can be found in natural sources such as plants. [18][19][20][21] The ability of acetylated polyphenols to promote tumor cell cycle arrest, death and to sensitize them to other anticancer agents remai...