Consistent with previous studies demonstrating high COX-2 expression in canine cancers including melanoma23, all canine melanoma cell lines (CMeC, LMeC, CMM-1, and CMM-2) and osteosarcoma cell lines (POS and HMPOS) examined had detectable COX2 mRNA expression (Fig. 3a). Here, PTGS2 is linked to osteosarcoma.