title: Metallothionein content correlates with the sensitivity of human small cell lung cancer cell lines to cisplatin.
abstract: We have established cis-diamminedichloroplatinum(II) (cisplatin) resistant human small cell lung cancer cell lines, H69/CDDP0.2 and H69/CDDP, to investigate the mechanism of acquired resistance to cisplatin. H69/CDDP0.2 and H69/CDDP were 6- and 11-fold resistant to cisplatin compared with the H69 parental cell line. H69/CDDP was also resistant to cadmium chloride (2-fold), cis-diammine(glycolato)platinum (4-fold), 4-hydroperoxycyclophosphamide (3-fold) and 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosour ea (4-fold) if the drug concentrations that inhibit cell growth by 50% from growth inhibition assay were compared. There was no significant difference in the cisplatin accumulation among these cell lines. Although DNA interstrand cross-link formations, determined by filter elution assay in H69/CDDP0.2 and H69/CDDP, was decreased to 20 to 30% of that in H69 parental cells, the repair capacity of DNA interstrand cross-links was equivalent in all three cell lines. Intracellular glutathione content was equal in all cell lines. H69/CDDP had the highest glutathione S-transferase activity (H69, 11 nmol/min/mg protein, H69/CDDP0.2, 12 nmol/min/mg protein; H69/CDDP, 74 nmol/min/mg protein, respectively) and an overexpression of glutathione S-transferase pi mRNA. The drug concentrations that inhibit cell growth by 50% for cisplatin in all cell lines were decreased by treatment with ethacrynic acid, an inhibitor of glutathione S-transferase pi, but this did not alter the relative degree of resistance. Intracellular metallothionein content (H69, 14 pmol/mg protein, H69/CDDP0.2, 22 pmol/mg protein; H69/CDDP, 33 pmol/mg protein, respectively) and expression of metallothionein mRNA were correlated with the drug concentrations that inhibit cell growth by 50% of the three cell lines for cisplatin and cadmium chloride. The present study suggested the importance of metallothionein in the mechanisms of cisplatin resistance.
authors.affiliation: Pharmacology Division, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kasahara
authors.forename: Y
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: K
authors.initials: K
authors.lastname: Nishio
authors.forename: T
authors.initials: T
authors.lastname: Ohmori
authors.forename: Y
authors.initials: Y
authors.lastname: Sugimoto
authors.forename: K
authors.initials: K
authors.lastname: Komiya
authors.forename: T
authors.initials: T
authors.lastname: Matsuda
authors.forename: N
authors.initials: N
authors.lastname: Saijo
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D018288:Carcinoma, Small Cell; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000378:metabolism / Q000494:pharmacology*; D004351:Drug Resistance; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms; D008668:Metallothionein / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D008668:Metallothionein; D005982:Glutathione Transferase; D005978:Glutathione; D002945:Cisplatin