title: Time-dependent cytotoxicity induced by SJG-136 (NSC 694501): influence of the rate of interstrand cross-link formation on DNA damage signaling.
abstract: SJG-136 is a new pyrrolobenzodiazepine dimer inducing time-dependent cytotoxicity. HCT 116 cells were exposed to 50 nmol/L of SJG-136 for 1 hour or 1 nmol/L of SJG-136 for 24 hours to achieve similar levels of interstrand cross-links (ICL). The short exposure led to a rapid formation of ICLs (1 hour), early H2AX foci formation (4 hours), prominent S phase arrest, and greater phosphorylation of Nbs1 (on serine 343) and Chk1 (on serine 317) than a 24-hour exposure. The prolonged exposure at low concentrations of SJG-136 induced a gradual formation of ICLs (up to 24 hours) which was associated with a limited S phase arrest and delayed Nbs1 phosphorylation. Prolonged exposure was also associated with a reduced phosphorylation of p53 on serines 15 and 20, a limited and delayed phosphorylation on serine 392, and a less prominent increase in p21 levels. These data suggest that the 24-hour exposure to a low concentration of SJG-136 led to delayed and reduced DNA damage signaling compared with a higher concentration of SJG-136 for 1 hour, resulting in greater cytotoxicity and contributing to the time-dependent cytotoxic effect of SJG-136.
authors.affiliation: Cancer Research UK Centre, The University of Edinburgh, Crewe Road South, Edinburgh EH4 2XR, United Kingdom.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Arnould
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Spanswick
authors.forename: Janet S
authors.initials: JS
authors.lastname: Macpherson
authors.forename: John A
authors.initials: JA
authors.lastname: Hartley
authors.forename: David E
authors.initials: DE
authors.lastname: Thurston
authors.forename: Duncan I
authors.initials: DI
authors.lastname: Jodrell
authors.forename: Sylvie M
authors.initials: SM
authors.lastname: Guichard
mesh_terms: D001570:Benzodiazepinones / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects*; D000071877:Checkpoint Kinase 1; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects*; D045325:HCT116 Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*; D016196:S Phase / Q000187:drug effects; D015398:Signal Transduction; D013997:Time Factors
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); D001570:Benzodiazepinones; D003432:Cross-Linking Reagents; D011758:Pyrroles; D004247:DNA; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1