Geraniol, a component of plant essential oils, sensitizes human colonic cancer cells to 5-fluorouracil treatment

Differentiation of human colonic cancer cells at confluency has been correlated to their increased resistance to chemotherapeutic agents. The aim of this study was to determine whether blocking Caco-2 cell differentiation could sensitize the cells to 5-fluorouracil (5-FU) treatment. We show that in cells at confluency, geraniol (400 muM) prevented the formation of brush-border membranes and inhibited the expression of intestinal hydrolases (sucrase, lactase, alkaline phosphatase). The anti-proliferative effect of geraniol (400 muM) together with 5-FU (5 muM) was twice that of 5-FU alone. The cytotoxicity induced by 5-FU was enhanced in the presence of geraniol, as shown by a 50% increase of lactate dehydrogenase release in the culture medium. These effects are related to enhanced intracellular accumulation of 5-FU in the presence of geraniol as shown by a 2-fold increase in intracellular 5-[6-H-3]FU (1.5 muCi/ml). It is concluded that geraniol sensitizes colonic cancer cells to 5- FU treatment, by increasing the cytotoxicity of the drug, and that this results from the facilitated transport of 5-FU and the blockade of the morphological and functional differentiation of the cancer cells.