title: The XPF-ERCC1 endonuclease and homologous recombination contribute to the repair of minor groove DNA interstrand crosslinks in mammalian cells produced by the pyrrolo[2,1-c][1,4]benzodiazepine dimer SJG-136.
abstract: SJG-136, a pyrrolo[2,1-c][1,4]benzodiazepine (PBD) dimer, is a highly efficient interstrand crosslinking agent that reacts with guanine bases in a 5'-GATC-3' sequence in the DNA minor groove. SJG-136 crosslinks form rapidly and persist compared to those produced by conventional crosslinking agents such as nitrogen mustard, melphalan or cisplatin which bind in the DNA major groove. A panel of Chinese hamster ovary (CHO) cells with defined defects in specific DNA repair pathways were exposed to the bi-functional agents SJG-136 and melphalan, and to their mono-functional analogues mmy-SJG and mono-functional melphalan. SJG-136 was >100 times more cytotoxic than melphalan, and the bi-functional agents were much more cytotoxic than their respective mono-functional analogues. Cellular sensitivity of both SJG-136 and melphalan was dependent on the XPF-ERCC1 heterodimer, and homologous recombination repair factors XRCC2 and XRCC3. The relative level of sensitivity of these repair mutant cell lines to SJG-136 was, however, significantly less than with major groove crosslinking agents. In contrast to melphalan, there was no clear correlation between sensitivity to SJG-136 and crosslink unhooking capacity measured using a modified comet assay. Furthermore, repair of SJG-136 crosslinks did not involve the formation of DNA double-strand breaks. SJG-136 cytotoxicity is likely to result from the poor recognition of DNA damage by repair proteins resulting in the slow repair of both mono-adducts and more importantly crosslinks in the minor groove.
authors.affiliation: Cancer Research UK Drug-DNA Interactions Research Group, Department of Oncology, Royal Free and University College Medical School, UCL 91 Riding House Street, London, W1W 7BS, UK.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Clingen
authors.forename: Inusha U
authors.initials: IU
authors.lastname: De Silva
authors.forename: Peter J
authors.initials: PJ
authors.lastname: McHugh
authors.forename: Farid J
authors.initials: FJ
authors.lastname: Ghadessy
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tilby
authors.forename: David E
authors.initials: DE
authors.lastname: Thurston
authors.forename: John A
authors.initials: JA
authors.lastname: Hartley
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000633:toxicity*; D001569:Benzodiazepines / Q000737:chemistry / Q000633:toxicity; D001570:Benzodiazepinones / Q000737:chemistry / Q000633:toxicity*; D016466:CHO Cells; D002470:Cell Survival; D006224:Cricetinae; D003412:Cricetulus; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000633:toxicity*; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000502:physiology*; D004720:Endonucleases / Q000502:physiology*; D008558:Melphalan / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D011758:Pyrroles / Q000737:chemistry / Q000633:toxicity*; D011995:Recombination, Genetic
chemical_list: C423343:1,1'-((propane-1,3-diyl)dioxy)bis(7-methoxy-2-methylidene-1,2,3,10,11,11a-hexahydro-5H-pyrrolo(2,1-c)(1,4)benzodiazepin-5,11-dione); D000970:Antineoplastic Agents; D001570:Benzodiazepinones; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D011758:Pyrroles; C501643:mmy-SJG compound; C095888:xeroderma pigmentosum group F protein; D001569:Benzodiazepines; D004720:Endonucleases; C405767:monohydroxymelphalan; D008558:Melphalan