In our own work, we have shown that COX-2 expression is elevated 141-fold in the CSC population compared to the non-CSC population of canine osteosarcoma cells, and that COX-2 inhibition induced a dose-dependent decrease in sphere forming ability, indicating that COX-2 plays a major role in tumour initiation [13]. The gene discussed is PTGS2; the disease is neoplasm.