Osteosarcoma is the most common primary bone tumour, and despite having conventional treatment, the survival rate has not changed in decades.

Flavonoids are polyphenolic compounds with antioxidant, anti-inflammatory, and anticancer properties.

Here we evaluated the effect of flavonoids on cell death in the human osteosarcoma cell lines MG-63 and Saos-2 (p53 deficient and null). The SRB (sulforhodamine B) assay was performed to evaluate cytotoxicity: cells were exposed to different concentrations of 10 flavonoids during 48h, and then fixed and stained with SRB for quantitative microplate analysis. Gossypetin, among the most bioactive compounds, was further selected for apoptosis analysis: cells were incubated with gossypetin for 48h and annexin V was added together with propidium iodide to determine cell death percentage by flow cytometry. Gossypetin, at higher concentrations, induced apoptosis in the p53-deficient cell lines.

Acknowledgements

The authors acknowledge funding from Fundação para a Ciência e a Tecnologia (FCT) and Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds and “Programa Operacional Competitividade e Internacionalização” (COMPETE), grant number PTDC/MED-QUI/29243/2017-POCI-01-0145-FEDER-029243 and from PT national funds (FCT/MCTES) through grant UIDB/50006/2020. J.M.P.F.O. thanks FCT for funding through program DL 57/2016-Norma transitória (Ref. SFRH/BPD/74868/2010). Marisa Freitas further acknowledges the contract 647 under the Scientific Employment Stimulus - Individual Call (CEEC Individual) 2020.04126.CEEC- 648IND/CP1596/CT0006.