INCREASED EXPRESSION OF GLUTATHIONE S-TRANSFERASE GENE IN CIS-DIAMMINEDICHLORO-PLATINUM(II)-RESISTANT VARIANTS OF A CHINESE-HAMSTER OVARY CELL-LINE

  • 15 December 1989
    • journal article
    • research article
    • Vol. 49  (24) , 7020-7025
Abstract
We have isolated cis-diamminedichloroplatinum(II) (CDDP)-resistant variants, C/CDP-1 and C/CDP-2, from a Chinese hamster ovary (CHO) cell line after a stepwise exposure to increasing concentrations of CDDP, and a CDDP-sensitive revertant, R-1, from C/CDP-2 after continuous incubation for 5 months in the absence of CDDP. C/CDP-1 and C/CDP-2 showed 7- and 10-fold higher resistance to CDDP, respectively, compared to CHO cells. C/CDP-2 was cross-resistant to carboplatin, L-phenylalanine mustard (melphalan), and CdSO4, but not to other anticancer agents. Alkaline elution of DNA showed an increased amount of DNA interstrand cross-linking formation in CHO cells, but not in C/CDP-2 cells, when CHO and C/CDP-2 cells were cultured with CDDP. By contrast, alkaline elution of DNA showed increased formation of DNA cross-links when nuclei of C/CDP-2 cells were treated with CDDP. The activity of glutathione S-transferase (GST) of C/CDP-1 and C/CDP-2 was 4- and 6-fold higher than that of CHO cells, respectively. The cellular level of GST activity of R-1 was almost similar to that of CHO cells. Northern blotting analysis revealed that GST-.pi. mRNA in both C/CDP-1 and C/CDP-2 cell lines was increased more than 5-fold over that of CHO and R-1 cells. There is no apparent gene amplification of GST-.pi. gene in CDDP-resistant cell lines. Immunoblot assays showed a specific increase of GST-.pi. in C/CDP-1 and C/CDP-2, but no increase in GST-.mu. and GST-.alpha.. We also compared CDDP-resistant properties of resistant variant, P/CDP-5, derived from human prostate cancer PC-3 cell line, with those of C/CDP-1 and C/CDP-2 cells and found no increased GST activity in P/CDP-5 cells. Multiple mechanisms might be considered for acquisition of CDDP resistance in various cell lines in culture.

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