Anti-Cancer Activity of Sphaerococcus coronopifolius Algal Extract: Hopes and Fears of a Possible Alternative Treatment for Canine Mast Cell Tumor.

Within the "One Health, One Medicine" and comparative oncology paradigms, algal extracts have attracted attention, containing natural compounds (NCs) with biological activities, including anti-cancer properties. To characterize the biological effects of a Sphaerococcus coronopifolius extract (SCE), two canine mastocytoma and two normal cell lines were used. After a preliminary screening of three algal extracts, SCE cytotoxicity was measured using Alamar Blue, Sulforhodamine B, and Neutral Red Uptake assays. After assessing the selectivity versus tumor cells and its chemical characterization, SCE mechanisms of action were investigated using RNA-seq, quantitative PCR, flow cytometry and immunoblotting approaches. SCE showed an IC50 comprised between 25 and 35 μg/mL in tumor cell lines, but it also affected normal ones (selectivity index < 2.0). RNA-seq and flow cytometry revealed that SCE negatively affected cell cycle and mevalonate pathway in tumor cells. Additional flow cytometry and immunoblotting investigations suggested a concentration- and time-dependent pro-apoptotic effect of SCE and DNA damage events. In conclusion, SCE demonstrated promising anti-cancer activity in mastocytoma cell lines by targeting the mevalonate pathway, arresting the cell cycle, and inducing apoptosis and DNA damage. Furthermore, the results presented here reinforce the idea that NCs may be promising candidates in comparative anti-cancer chemotherapy.