[Evaluation of predictability of in vitro SDI assay in comparison with in vivo nude mouse assay].

Twenty lines of human gastro intestinal and breast cancer xenografts, in which chemosensitivity spectra by the in vivo nude mouse assay had been clarified. were subjected to the in vitro SDI (succinate dehydrogenase inhibition) assay using MTT dye to assess the accuracy of this drug sensitivity test against 4 drugs i.e., mitomycin C (MMC), adriamycin (ADM) 5 fluorouracil (5-FU), and cisplatin (CDDP). After 3 days incubation, the suspension of every tumor cells including small fragments showed a marked decrease of SD activity even when no anticancer drug was added to the assay medium. Among these 4 drugs evaluated MMC exhibited a statistically significant correlation between chemosensitivity values of the in vitro SDI assay and those of the nude mouse assay. However, the other 3 drugs demonstrated no correlation between the values of these two methods. Since the primary cultured fibroblasts revealed, in general, lower sensitivity to these drugs, contamination of fibroblast may decrease the SDI values when materials from solid tumors with rich stroma such as a type of stomach cancer were subjected. It is considered that the prediction of chemosensitivity to every drug will be impossible by a in vitro SDI assay.