Honokiol induces autophagy and apoptosis of osteosarcoma through PI3K/Akt/mTOR signaling pathway

Honokiol is the main active constituent of Magnolia officinalis. With effective and long-term pharmacological functions of being antibacterial, anti-oxidative, anti-inflammatory, antitumor, anti-spasmic, anti-anxiety and anti-viral, Honokiol is clinically used in the treatment of acute enteritis and chronic gastritis. The aim of the present study was to observe the possible anti-effects of honokiol on autophagy and apoptosis of osteosarcoma, and to investigate the role of the PI3K/Akt/mTOR signaling pathway in its anticancer effects. MTT assay was used to evaluate cell proliferation and Annexin V-fluorescein isothiocyanate/propidium iodide staining flow cytometry was used to analyze the apoptotic rate. The authors identified that honokiol could inhibit cell proliferation and induce the apoptotic rate of osteosarcoma cells. The expression level of Bcl-2-like protein 4, caspase-3 and p53 protein expression were induced and cyclin D1 protein expression was suppressed in osteosarcoma cells by honokiol. Autophagy-associated LC3II protein expression level was promoted, and PI3K, p-Akt and p-mTOR protein expression level was suppressed in osteosarcoma cells by honokiol. The present study demonstrated, to the best of the authors' knowledge, for the first time that honokiol induces autophagy and apoptosis of osteosarcoma cells through the PI3K/Akt/mTOR signaling pathway.