H2AX and neoplasm: The current study was therefore undertaken to investigate the activity and cellular pharmacology of SG2000 in canine cancers in vitro, to assess the in vivo antitumour activity of SG2000 against canine tumour xenografts and to evaluate the potential of the comet and γ-H2AX foci methods as pharmacodynamic assays for use in the further clinical development of the drug.