1. Academic Validation
  2. Activity of the DNA minor groove cross-linking agent SG2000 (SJG-136) against canine tumours

Activity of the DNA minor groove cross-linking agent SG2000 (SJG-136) against canine tumours

  • BMC Vet Res. 2015 Aug 19;11:215. doi: 10.1186/s12917-015-0534-2.
Maria Mellinas-Gomez 1 2 Victoria J Spanswick 3 Solange R Paredes-Moscosso 4 Matthew Robson 5 R Barbara Pedley 6 David E Thurston 7 8 Stephen J Baines 9 10 Anneliese Stell 11 John A Hartley 12
Affiliations

Affiliations

  • 1 CR-UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street, London, WC1E 6BT, UK. Maria.Mellinas-Gomez@spirogen.com.
  • 2 Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA, UK. Maria.Mellinas-Gomez@spirogen.com.
  • 3 CR-UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street, London, WC1E 6BT, UK. v.spanswick@ucl.ac.uk.
  • 4 CR-UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street, London, WC1E 6BT, UK. solange.moscosso.10@ucl.ac.uk.
  • 5 UCL Cancer Institute, Paul O'Gorman Building, 72 Huntley Street, London, WC1E 6BT, UK. mathew.robson@ucl.ac.uk.
  • 6 UCL Cancer Institute, Paul O'Gorman Building, 72 Huntley Street, London, WC1E 6BT, UK. r.b.pedley@ucl.ac.uk.
  • 7 The School of Pharmacy, University College London, Brunswick Square, London, WC1E 6BT, UK. david.thurston@kcl.ac.uk.
  • 8 Present address: Institute of Pharmaceutical Science, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK. david.thurston@kcl.ac.uk.
  • 9 Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA, UK. stephenbaines@gmail.com.
  • 10 Present address: Willows Referral Service, Highlands Road, Shirley, Solihull, West Midlands, B90 4NH, UK. stephenbaines@gmail.com.
  • 11 Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA, UK. astell@RVC.AC.UK.
  • 12 CR-UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street, London, WC1E 6BT, UK. john.hartley@ucl.ac.uk.
Abstract

Background: Cancer is the leading cause of death in older dogs and its prevalence is increasing. There is clearly a need to develop more effective anti-cancer drugs in dogs. SG2000 (SJG-136) is a sequence selective DNA minor groove cross-linking agent. Based on its in vitro potency, the spectrum of in vivo and clinical activity against human tumours, and its tolerability in human patients, SG2000 has potential as a novel therapeutic against spontaneously occurring canine malignancies.

Results: In vitro cytotoxicity was assessed using SRB and MTT assays, and in vivo activity was assessed using canine tumour xenografts. DNA interstrand cross-linking (ICL) was determined using a modification of the single cell gel electrophoresis (comet) assay. Effects on cell cycle distribution were assessed by flow cytometry and measurement of γ-H2AX by immunofluorescence and immunohistochemistry. SG2000 had a multi-log differential cytotoxic profile against a panel of 12 canine tumour cell lines representing a range of common tumour types in dogs. In the CMeC-1 melanoma cell line, DNA ICLs increased linearly with dose following a 1 h treatment. Peak ICL was achieved within 1 h and no removal was observed over 48 h. A relationship between DNA ICL formation and cytotoxicity was observed across cell lines. The formation of γ-H2AX foci was slow, becoming evident after 4 h and reaching a peak at 24 h. SG2000 exhibited significant anti-tumour activity against two canine melanoma tumour models in vivo. Anti-tumour activity was observed at 0.15 and 0.3 mg/kg given i.v. either once, or weekly x 3. Dose-dependent DNA ICL was observed in tumours (and to a lower level in peripheral blood mononuclear cells) at 2 h and persisted at 24 h. ICL increased following the second and third doses in a repeated dose schedule. At 24 h, dose dependent γ-H2AX foci were more numerous than at 2 h, and greater in tumours than in peripheral blood mononuclear cells. SG2000-induced H2AX phosphorylation measured by immunohistochemistry showed good correspondence, but less sensitivity, than measurement of foci.

Conclusions: SG2000 displayed potent activity in vitro against canine Cancer cell lines as a result of the formation and persistence of DNA ICLs. SG2000 also had significant in vivo antitumour activity against canine melanoma xenografts, and the comet and γ-H2AX foci methods were relevant pharmacodynamic assays. The clinical testing of SG2000 against spontaneous canine Cancer is warranted.

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