title: Overexpression of DNA replication and repair enzymes in cisplatin-resistant human colon carcinoma HCT8 cells and circumvention by azidothymidine.
abstract: Biochemical differences were demonstrated between two cell lines derived from a human colon carcinoma (HCT8), one sensitive (HCT8S), and one 4.3-fold resistant to cisplatin (HCT8DDP). The cisplatin-resistant cell line overexpressed five enzymes (dihydrofolate reductase, thymidine 5'-monophosphate synthase, thymidine kinase, and DNA polymerase alpha and beta) believed to be important for DNA replicative and repair synthesis. In addition, the c-fos and c-H-ras oncogenes were also overexpressed in the HCT8DDP cells. This apparent overexpression was not associated with increases in gene copy number, it was related, however, to increased mRNA content. Expression of these key enzymes may be a significant factor in the development of clinical resistance to cisplatin. Further, these specific changes in cellular metabolism associated with cisplatin resistance may be exploited by the use of nucleoside analogues.
authors.affiliation: Department of Medical Oncology, City of Hope National Medical Center, Duarte, CA 91010.
authors.forename: K J
authors.initials: KJ
authors.lastname: Scanlon
authors.forename: M
authors.initials: M
authors.lastname: Kashani-Sabet
authors.forename: L C
authors.initials: LC
authors.lastname: Sowers
mesh_terms: D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology*; D003110:Colonic Neoplasms; D004256:DNA Polymerase I / Q000378:metabolism; D004257:DNA Polymerase II / Q000378:metabolism; D004260:DNA Repair; D004261:DNA Replication; D004351:Drug Resistance; D005047:Etoposide / Q000494:pharmacology; D005467:Floxuridine / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology; D006801:Humans; D008727:Methotrexate / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism; D013940:Thymidylate Synthase / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D015215:Zidovudine / Q000494:pharmacology*
chemical_list: D005467:Floxuridine; D015215:Zidovudine; D005047:Etoposide; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; D013937:Thymidine Kinase; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D002945:Cisplatin; D005472:Fluorouracil; D008727:Methotrexate