TYMS and neoplasm: Since TYMS transcription occurs during both G1 and S phases [24], [47] and 5-FU increases the cell amount in the S phase, we decided to evaluate and compare the anti-tumor responses generated by different combinations of 5-FU and others agents which have shown the ability to compromise the cell cycle such as cDDP and the polyamine analog N1,N11-diethylnorspermine (DENSpm).