OBJECTIVETo study the effect of chemotherapy with drugs selected according to drug sensitivity test and drug- resistance gene assessment in mice bearing tumors derived from high-passage gastric cancer cells.

METHODSChemosensitivity of the mouse gastric cancer cells to 6 chemotherapeutic drugs was investigated using MTT assay before the 6 drugs were applied in mice with implanted tumors. The implanted tumor volume and tumor inhibition rate were observed, and the expression of the multidrug resistance-1 (MDR1) gene was detected.

RESULTS5-FU, the most sensitive among the 6 drugs, resulted in significantly higher tumor inhibition rates in comparison with the control group, but did not significant affect MDR1 expression. Adriamycin (ADM) had the lowest sensitivity with low tumor inhibition rates and no significant effect on MDR1 expression. Cisplatin (DDP) was identified as the most sensitive drug for mouse gastric cancer with previous 5-FU exposure, and Mitomycin (MMC) was the most insensitive drug for mouse gastric cancer with previous ADM treatment. In mice bearing tumors of the second-passage cells, DDP showed high tumor inhibition rate but scarcely affected MDR1 expression; MMC resulted in low tumor inhibition rate and high MDR1 expression. Application of 5-FU and ADM in these tumor-bearing mice of the second-passage cancer cells resulted in rather low tumor inhibition rates without significant alterations in MDR1 expression as compared with the control group.

CONCLUSIONAppropriate individualized chemotherapy should be implemented in full consideration of the results of drug sensitivity test and drug-resistance gene assessment.