GS-424044 and GS-343074 induce apoptosis in canine tumour cells. A representative cell line, Abrams, was treated with increasing concentrations of GS-424044 and GS-343074 for 48 h. (A) The percentage of apoptotic cells was detected by flow cytometry using annexin V/PI double staining. (B) Apoptosis was assessed by counting the percentage of annexin V-positive cells. Early apoptosis, annexin-V(+), PI(−); late apoptosis, annexin-V(+), PI(+); total apoptosis, early apoptosis + late apoptosis. Similar were seen in all cell lines used in this study.