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Although anticancer chemotherapy is getting effective even against gastric cancer, there are still non-responders whose cancer volume can not be reduced by chemotherapy. Early detection and elimination of non-responders in anticancer chemotherapy is clinically useful to avoid useless medical cost and maintain patients’ QOL. We previously reported the molecular based chemosensitivity test (MCT) in 2003 AACR annual meeting, and demonstrated MCT had a potent possibility to predict chemotherapeutic outcome in early phase after initial chemotherapy, in vitro. In the study, we added in vivo experiment using nude mouse system as well as in vitro study, in order to perform further evaluation for the correlation between the gene expression and antitumor effect. Material and Methods: We examined gadd153, p21 and c-jun as candidate genes, of which expression have been already reported to be up-regulated by DNA damage in malignant cells. (in vitro) We utilized human gastric cancer cell lines, TMK-1, MKN-45, and MKN-74, inhibited by 5-fluorouracil (5FU) and cisplatin (CDDP). (in vivo) The human gastric cancer, TMK-1, nude mouse system was used in this study. 5-FU or CDDP were administrated intraperitoneally (i.p.) at a dose of 30, 90, 180mg/kg in 5-FU or 2, 6, 18mg/kg in CDDP by an injection. Each tumor was collected at 48 hour after drug administration, and examined for each gene expression. On the other hand, each tumor size was evaluated at 3 weeks after drug administration as tumor growth inhibition. Quantification of m-RNA expression was performed with real-time PCR method using ABI 7700. This method can distinguish at least 2 times change in each gene. Results: (in vitro) High concentration of CDDP or 5-FU resulted in strong induction of each gene in all cells. Dose and time dependency were confirmed in each gene expression. We could set up the cut-off value of each gene such as, gadd153; 1, p21; 2 and c-jun; 0.8. When gene expression is more than the cut-off value at 48h after the chemotherapy, the chemotherapy will be expected to be effective. (in vivo) High dose of either 5-FU (180mg/kg, i.p.) or CDDP (90mg/kg, i.p.) treatment induced high level of the gene expression and resulted in significant inhibition for tumor growth. High CDDP (90mg/kg, i.p.) demonstrated strong induction of each gene such as 8.6 times in gadd153, 5.2 times in p21, or 5.4 times in c-jun, compared with those of the control. Dose and time dependency was confirmed in each gene expression. These results suggested that detection for increased expression of the three genes at m-RNA level in earlier phase predicts cell damages at later phase in vivo nude mouse system as well as in vitro.

[Proc Amer Assoc Cancer Res, Volume 45, 2004]