Establishment and characterization of 5-fluorouracil-resistant gastric cancer cells

Two 5-fluorouracil (5-FU)-resistant cell lines from a Korean gastric cancer cell line were established by incubation of the cells with increasing conc entration of 5-FU. and the resultant cell lines showed an over 800-fold inc reased resistance to 5-FU. To identify the mechanism of 5-FU resistance, th e expressions of genes involved in 5-FU metabolism were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). Expressions of orotate p hosphoribosyltransferase (OPRT), thymidine phosphorylase (TP), and uridine phosphorylase (UP) were significantly downregulated in these cell lines, re sulting in low incorporation of 5-FU into nucleic acids. In contrast, an in creased expression of thymidine kinase (TK) was observed in 5-FU resistant cells. These results strongly indicate that blocking of 5-FU incorporation into nucleic acids and TK overexpression may play a major role in 5-FU resi stance in these cells. Interestingly, these cell lines showed cross-resista nce to paclitaxel, cisplatin, and doxorubicin. suggesting that other factor s such as HSP27 and Mn-SOD could be also involved in the mechanism of multi drug resistance in these cell lines. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.