Sensitivity test for 5-fluorouracil and its analogues, 1-(2-tetrahydrofuryl)-5-fluorouracil, uracil/1-(2-tetrahydrofuryl)-5-fluorouracil (4:1) and 1-hexylcarbamoyl-5-fluorouracil, using the subrenal capsule assay

Chemosensitivity test for carcinoma of digestive organs

For the chemosensitivity for carcinoma of digestive organs, gastric, colorectal, and hepatic cancer tissues were examined using in vitro succinate dehydrogenase inhibition (SDI) test and in vivo subrenal capsule (SRC) assay. The chemosensitivity varied in the tissue. The origin of an organ tumor, histological differentiation, and difference of primary or metastatic lesions are critical for determining chemosensitivity. Biochemical analysis shows that antitumor drugs have an increased susceptibility in tissues with high activity of pyrimidine nucleotide synthesis.

5-Fluorouracil and UFT-sensitive gastric carcinoma has a high level of thymidylate synthase

The authors examined the relationship between the level of thymidylate synthase (TS) and the sensitivity to 5-fluorouracil (5-FU) and UFT, a combined oral preparation of 1-(2-tetrahydrofuryl)-5-fluorouracil (tegafur) and uracil in a molar ratio of 1:4. For the studies we used the subrenal capsule (SRC) assay and 15 human gastric cancer tissues. The TS levels were assayed by the ligand-binding technique, using [6-3H]FdUMP. The relative variation of tumor size (delta TuS/TuS0) was calculated to be as follows: delta TuS/TuS0 = [(TuS6 - TuS0)/TuS0] x 100 (%), where TuS6 was the tumor size on day 6 and TuS0 on day 0. The chemosensitivity was considered to be positive when delta TuS/TuS0 in the treated group decreased to below -10%. Decrease in tumor size was marked in case of exposure to UFT (-19.8 +/- 13.0%) (mean +/- standard deviation), compared with that to 5-FU (-9.0 +/- 7.2%), with a statistically significant difference (P less than 0.001). The TS level varied from 1.7 to 30.8 pmol/g gastric cancer tissue and the mean was 7.1 +/- 7.2 pmol/g tissue. A correlation was noted between the TS level and decrease in size of the tumor exposed to 5-FU (r = -0.671) or UFT (r = -0.758): gastric cancer tissue with higher level of TS is more sensitive to 5-FU and UFT than is that with a lower TS level. These findings show that the sensitivity to 5-FU and UFT of gastric cancer tissue is related to the TS level and that UFT shows promise for the treatment of patients with gastric cancer.