title: Enhanced repair of a cisplatin-damaged reporter chloramphenicol-O-acetyltransferase gene and altered activities of DNA polymerases alpha and beta, and DNA ligase in cells of a human malignant glioma following in vivo cisplatin therapy.
abstract: Current evidence suggest an important role for increased repair of drug-induced DNA damage as one of the major mechanisms involved in tumor cell resistance to cis-DDP. In this study, we examined the DNA repair capacity and the activities of three DNA repair related proteins, namely, DNA polymerases alpha and beta, and total DNA ligase in cells of a malignant oligodendroglioma obtained from a patient before therapy and compared it with those of a specimen of the tumor acquired after the patient had failed cis-DDP therapy. DNA repair capacity was quantitated as the extent of reactivation of the chloramphenicol-O-acetyltransferase (CAT) gene in a eukaryotic expression vector that had been damaged and inactivated by prior treatment with cis-DDP and then transfected into the tumor cells. The extent of DNA-platinum adduct formation in the expression vector was determined by flameless atomic absorption spectrometry. The level of cis-DDP resistance of cells of the two tumors was determined with the capillary tumor stem cell assay. We observed a 2.8-fold increased capacity to repair Pt-DNA adducts and reactivate the CAT gene in cells of the tumor obtained after cis-DDP therapy, compared to cells of the untreated tumor. This was associated with increases of 9.4-fold and a 2.3-fold, respectively, in DNA polymerase beta and total DNA ligase activities in cells of the treated tumor. At 5 microM cis-DDP, there was a 5.9-fold increase in the in vitro cis-DDP resistance of post-therapy tumor cells relative to cells of the untreated tumor.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Experimental Pediatrics, University of Texas M.D. Anderson Cancer Center, Houston 77030.
authors.forename: F
authors.initials: F
authors.lastname: Ali-Osman
authors.forename: M S
authors.initials: MS
authors.lastname: Berger
authors.forename: A
authors.initials: A
authors.lastname: Rairkar
authors.forename: D E
authors.initials: DE
authors.lastname: Stein
mesh_terms: D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics*; D002945:Cisplatin / Q000494:pharmacology* / Q000627:therapeutic use; D004249:DNA Damage / Q000187:drug effects; D011088:DNA Ligases / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism; D004257:DNA Polymerase II / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004351:Drug Resistance; D005910:Glioma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D014162:Transfection
chemical_list: D015500:Chloramphenicol O-Acetyltransferase; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D004259:DNA-Directed DNA Polymerase; D011088:DNA Ligases; D002945:Cisplatin