Utility of the second-generation curcumin analogue RL71 in canine histiocytic sarcoma

Canine histiocytic sarcoma is an aggressive cancer, with a high rate of metastasis. Thus, novel therapeutic approaches are needed. Synthetic analogues of curcumin have elicited potent anti-cancer activity in multiple in vitro and in vivo models of human cancer. Furthermore, the compound 3,5-bis(3,4,5-trimethoxybenzylidene)-1-methylpiperidine-4-one (RL71) has recently exhibited potent cell cycle arrest and apoptotic induction in a canine osteosarcoma cell line. To determine its potency in canine histiocytic sarcoma cells, cell viability of DH82 and Nike cells was measured using the sulforhodamine B assay. Flow cytometry was then used to analyse both cell cycle distribution and apoptosis. Of the five curcumin analogues examined, RL71, had the highest potency with EC₅₀ values of 0.66 ± 0.057 µM and 0.79 ± 0.13 µM in the DH82 and Nike cell lines, respectively. Furthermore, RL71 at the 1x EC₅₀ concentration increased G2/M cell cycle arrest 2-fold, and at the 2x EC₅₀ concentration increased the number of apoptotic cells 4-fold. These findings are consistent with previous work using RL71 in both canine and human cancer cell lines. Future research should be directed on time-dependent changes, and mechanistic investigation in greater detail to elucidate RL71 mechanisms of action.