title: Arabinosyl-2-fluoroadenine augments cisplatin cytotoxicity and inhibits cisplatin-DNA cross-link repair.
abstract: Cytotoxicity was increased significantly when arabinosyl-2-fluoroadenine (F-ara-A) was administered in simultaneous combination with cisplatin (CDDP) to human colon tumor cell lines relatively sensitive (LoVo) or resistant (CP2.0) to CDDP. Because the mechanism of action of F-ara-A indicates that it may be an effective inhibitor of DNA repair, we hypothesized that F-ara-A induces cytotoxic augmentation by suppressing cellular repair in CDDP-damaged DNA lesions. To test this, we compared the repair of CDDP-induced DNA interstrand cross-links in the total genome and in ERCC1 gene-specific sequences of LoVo and CP2.0 cells for treatments with CDDP and CDDP plus F-ara-A. We determined the DNA repair by measuring the rate of removal of the cross-links, using two methods, i.e., an ethidium bromide fluorescence binding assay, which detects the DNA lesion in the total genome, and a method combining denaturation/renaturation neutral agarose gel electrophoresis and Southern hybridization to detect gene-specific lesions. When F-ara-A (15 microM) was coadministered with CDDP (15 micrograms/ml for LoVo cells and 30 micrograms/ml for CP2.0 cells) for 4 hr, the initial cross-link index for the total genome was increased 67% (4.5 versus 2.7 with CDDP alone) in LoVo cells and 93% (2.9 versus 1.5 with CDDP alone) in resistant CP2.0 cells. At 10 hr after the treatment, only 5% of the cross-links had been removed in combination-treated LoVo cells, compared with 40% in CDDP-treated LoVo cells; in CP2.0 cells, F-ara-A inhibited the removal of cross-links from 95% to 45%. Similar results were obtained for ERCC1 gene-specific DNA sequences. These data suggest that F-ara-A enhances the accumulation of CDDP-induced cross-links in LoVo and CP2.0 cells by suppressing the repair of such lesions, thereby enhancing the cytotoxicity of CDDP in combination treatment.
authors.affiliation: Division of Laboratory Medicine, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: L Y
authors.initials: LY
authors.lastname: Yang
authors.forename: L
authors.initials: L
authors.lastname: Li
authors.forename: M J
authors.initials: MJ
authors.lastname: Keating
authors.forename: W
authors.initials: W
authors.lastname: Plunkett
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage*; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000008:administration & dosage*; D003432:Cross-Linking Reagents; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects* / Q000235:genetics; D004273:DNA, Neoplasm / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D004351:Drug Resistance; D004357:Drug Synergism; D015894:Genome, Human; D006801:Humans; D013890:Thiourea / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014740:Vidarabine / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D004273:DNA, Neoplasm; D014740:Vidarabine; D013890:Thiourea; C024352:fludarabine; D002945:Cisplatin