Low-dose cisplatin and 5-fluorouracil in combination can repress increased gene expression of cellular resistance determinants to themselves.
The synergistic mechanism of cisplatin (CDDP) and 5-fluorouracil (5-FU) in combination remains unclear, despite its substantial antitumor activity, which has been demonstrated clinically. To clarify the mechanism(s), we determined the sensitivity or resistance factors to either drug in seven gastrointestinal cancer cell lines and then analyzed the altered gene expression after different exposures to CDDP and 5-FU. At the basal gene expression level, glutathione S-transferase pi (GSTpi) expression correlated with the observed resistance to CDDP, whereas dihydropyrimidine dehydrogenase (DPD) and multidrug resistance-associated protein (MRP) expression was related to 5-FU resistance. GSTpi, DPD, and MRP expression increased in response to the respective drug, but they also increased in response to the other drug as well. Additionally, 5-FU revealed a drastically increased thymidylate synthase (TS) gene expression in 5-FU-resistant cells. However, the increasing actions of CDDP and 5-FU on GSTpi, DPD, MRP, and TS expression varied according to the exposure time, concentration, and schedule. A low concentration of CDDP (1 microg/ml, 30 min) followed by 5-FU (0.5 microg/ml, 72 h) was found to cause a less increased expression of DPD, MRP, GSTpi, and TS than either drug alone, thus resulting in synergistic cytotoxicity in 5-FU-resistant COLO201 and CDDP-resistant HCC-48 cells. The sequential combination of CDDP and 5-FU inhibited the growth of human normal renal proximal tubule cells by less than 20%. Low concentrations of CDDP followed by continuous exposure to 5-FU can repress increased gene expression related to both drug resistances, thereby being synergistically cytotoxic in human gastrointestinal cancer cells.
Nishiyama
M
M
Department of Biochemistry and Biophysics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Japan. yamacho@mcai.med.hiroshima-u.ac.jp
Yamamoto
W
W
Park
J S
JS
Okamoto
R
R
Hanaoka
H
H
Takano
H
H
Saito
N
N
Matsukawa
M
M
Shirasaka
T
T
Kurihara
M
M
D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics; D000230:Adenocarcinoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D002945:Cisplatin / Q000008:administration & dosage; D042943:Dihydrouracil Dehydrogenase (NADP); D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D005472:Fluorouracil / Q000008:administration & dosage; D005770:Gastrointestinal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D020014:K562 Cells / Q000187:drug effects; D007680:Kidney Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D010088:Oxidoreductases / Q000096:biosynthesis / Q000235:genetics; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
D018528:ATP-Binding Cassette Transporters; D002945:Cisplatin; D042943:Dihydrouracil Dehydrogenase (NADP); D005472:Fluorouracil; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; D007527:Isoenzymes; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D010088:Oxidoreductases; D013940:Thymidylate Synthase; C496556:GSTP1 protein, human