Leading cancer researchers update and review the mechanisms of action and the therapeutic selectivity and efficacy of 5-FU with and without leucovorin and its prodrugs in the treatment of colorectal cancer. Among the combination agents considered are UFT/LV, 5-FU/EU, capecitabine (Xeloda), S-1, and a variety of thymidylate synthase inhibitors. The authors discuss the potential advantages and disadvantages of these varied drugs and their mode of administration. Based on historical results with these agents when used alone, they also present a rationale for their results when used in combination with other agents.Leading cancer researchers update and review the mechanisms of action and the therapeutic selectivity and efficacy of 5-FU with and without leucovorin and its prodrugs in the treatment of colorectal cancer. Among the combination agents considered are UFT/LV, 5-FU/EU, capecitabine (Xeloda), S-1, and a variety of thymidylate synthase inhibitors. The authors discuss the potential advantages and disadvantages of these varied drugs and their mode of administration. Based on historical results with these agents when used alone, they also present a rationale for their results when used in combination with other agents.Relative Role of 5-Fluorouracil Activation and Inactivation Pathways on its Cytotoxic Effects: Preclinical and Clinical ModulationG. J. PetersDihydropyrimidine Dehydrogenase and Treatment by Fluoropyrimidines: Past and Future DirectionsG?rard MilanoBiochemical Bases of the 5-Fluorouracil-Folinic Acid Interaction and of its Limitations: A Retrospective AnalysisRichard G. MoranMolecular Mechanisms Regulating the Expression of Thymidylate SynthaseJohn C. Schmitz, Ashwin Gollerkeri, Xiukun Lin, Jun Liu, and Edward ChuRegulation of Thymidylate Synthase Gene Expression and Drug Response: Posttranscriptional Regulation and Cell Population DensityBruce J. DolnickDeath Receptor Signaling in the Mechanism of 5-Fluorouracil ActionJanet A. HoughtonCircadian Rhythml3#