In vivo effects of ftorafur and fluorouracil on mammary tumors and small intestine in mice.

The in vivo effects of Ftorafur (FT) and 5-fluorouracil (FU) were evaluated at several different organizational levels within the same animal model. On a molar basis, FU was found to be two to three times more potent than FT with respect to growth inhibition of murine mammary adenocarcinomas. However, administration of FT produced less host toxicity at a dose level which resulted in similar antitumor activity. Drug-induced perturbations in cell cycle phase distributions were analyzed by the flow cytometer (FCM). Although FCM analysis is limited by lack of information on the extent of dead and dying cells, data obtained with both drugs were consistent with the possibility of S phase cytotoxicity and drug-induce G1/S block or delay. Changes in the age distribution of perturbed tumor cells, is detected by FCM analysis, correlated with 3H-TdR autoradiography and with 32P incorporation into DNA but not with 3H-deoxyuridine incorporation into DNA. Both drugs depressed 3H-deosyuridine incorporation into DNA; however, incorporation in both the tumor and small intestine returned to control levels earlier with FT than with an equimolar dose of FU. However, both drugs produced similar patters of 3H-deoxyuridine incorporation when FT was administered at three times the molar equivalent dose of FU. The results of these studies also suggest that deoxyuridine incorporation primarily reflects drug effects on thymidylate synthetase and not necessarily the overall rate of DNA synthesis. This study also involved the development of techniques for the dispersal of solid tumors and intestinal lining epithelium into single cell suspensions for FCM analysis. Tetraphenylboron (TPB) was utilized as an aid to solid tumor dispersal. TPB-dispersed tumors yield DNA distributions with minimal cell clumping and low levels of cellular debris. Fluorescent enzyme histochemistry with subsequent FCM analysis was utilized to separate dispersed epithelial cells of the small intestine into crypt and villus subpopulations. When fully optimized, the epithelial cell separation should offer a rapid method by which perturbations in the age distribution of crypt cells can easily be evaluated by FCM.