The purpose of this study was to screen 24 anti-cancer drugs, either in use or in clinical study, using four cell lines, all of which originated from poorly-differentiated gastric cancers. The MTT assay was used at 1, 6, 24 or 72 h exposure times as the chemosensitivity test. We also examined P-glycoprotein expression, mdr-1 gene amplification and the modifier effect of verapamil. All four cell lines generally showed the same chemosensitivity pattern, while GCIY cells showed mdr-1 gene amplification and P-glycoprotein expression, and KATOIII cells showed the multidrug resistant pattern without P-glycoprotein expression. Both cell lines acquired higher chemosensitivity after verapamil addition. All IC50 data (with or without verapamil) were multiplied by exposure time (Delta IC50) and compared with the clinical 'area under the concentration curve (AUG)'. SN-38 with/without verapamil, cisplatin with verapamil and pirarubicin with/without verapamil seemed to be the best candidates for poorly-differentiated gastric cancer chemotherapy. Plant alkaloids could also be candidates. With further experiments, we may be able to deduce commonly effective chemotherapy for poorly-differentiated gastric cancer from these drugs.
