Canine
osteosarcoma is an aggressive
cancer, comprising 85% of canine
bone neoplasms. Current treatment practices of surgery and
chemotherapy increase 1-year survival by only 45%. The
curcumin analogue RL71, has demonstrated potent in vitro and in vivo efficacy in several models of human
breast cancer through increased apoptosis and cell cycle arrest. Thus, the present study aimed to investigate efficacy of
curcumin analogues in two canine
osteosarcoma cell lines.
Osteosarcoma cell viability was assessed using the
sulforhodamine B assay and mechanisms of action were determined by analysing the levels of cell cycle and apoptotic regulatory
proteins via Western blotting. Further evidence was obtained using flow cytometry to detect cell cycle distribution and the number of apoptotic cells. RL71 was the most potent
curcumin analogue with EC50 values of 0.64 ± 0.04 and 0.38 ± 0.009 μM (n = 3) in D-17 (commercial) and Gracie canine
osteosarcoma cells, respectively. RL71 significantly increased the ratio of cleaved-
caspase 3 to
pro-caspase 3 and the level of apoptotic cells at the 2× and 5× EC50 concentration (p < 0.001, n = 3). Furthermore, at the same concentration, RL71 significantly increased the number of cells in the G2/M phase. In conclusion, RL71 has potent cytotoxic activity in canine
osteosarcoma cells triggering G2/M arrest and apoptosis at concentrations achievable in vivo. Future research should further investigate molecular mechanisms for these changes in other canine
osteosarcoma cell lines prior to in vivo investigation.