Evidence for Altered Regulation of γ-Glutamylcysteine Synthetase Gene Expression among Cisplatin-sensitive and Cisplatin-resistant Human Ovarian Cancer Cell Lines

摘要: We have shown previously that tumor cell resistance to cisplatin is associated with elevated intracellular levels of glutathione, which accomplished at least in part by increased expression the heavy subunit gamma-glutamylcysteine synthetase (gamma-GCS). To investigate mechanism gamma-GCS elevated, we examined four related human ovarian cancer lines increasing resistance. Relative amounts steady-state mRNA CP70, C30, and C200 were 4.8, 6.0, 10.6, respectively, compared parental A2780 line, a proportional increase transcriptional rate but not RNA stability was demonstrated. In contrast, no for light found. determine upregulation this mRNA, cloned promoter gene encodes gamma-GCS. This region contains AP-1, NF-kappa B, XRE, AP-2, EpRE, CAAT, TATA box elements upstream transcription initiation site two MREs between start codon protein. Using gel mobility shift assays, found nuclear extract binding activity AP-1 response element be closely level expression. A supershift assay showed DNA-binding complexes are predominantly formed dimers JUN family members. Consistent finding, c-JUN resistant cells. contrast binding, AP-2 B inversely Furthermore, partial revertant C200-resistant cells, shows lower glutathione levels, decreased activity.