The anti-tumor effect of taxifolin on lung cancer via suppressing stemness and epithelial-mesenchymal transition in vitro and oncogenesis in nude mice

BACKGROUND: Taxifolin is a natural flavonoid with anti-oxidant and anti-proliferative properties. In this study, we investigated the stemness-related inhibitory effects of taxifolin in two lung cancer cell lines, A549 and H1975, as well as in A549 xenografts. METHODS: A549 and H1975 cells, as well as A549 xenograft BALB/c mice were treated with taxifolin. Cell viability, stemness, mobility and protein expression were tested with Cell counting kit-8 (CCK-8), Colony formation assay, Flow cytometry, Transwell, Western blot and Immunohistochemistry, respectively. RESULTS: CCK-8 exhibited an obvious toxicity of taxifolin to both cell lines at higher dose. Then taxifolin of 0, 25, 50, and 100 µM/L were subsequently used. Taxifolin exhibited inhibitory effects on stemness and sphere formation, reduced protein expression of SOX2 and OCT4, and reduced CD133-positive cells. Furthermore, taxifolin decreased invasive cells, reduced N-cadherin and vimentin while increased E-cadherin expression, indicating that epithelial-mesenchymal transition (EMT) was inhibited. All of the effects observed were exhibited in a dose-dependent manner, and A549 cells proved to be more sensitive to taxifolin than H1975 cells. Taxifolin inactivated PI3K and TCF4 protein phosphorylation; however, taxifolin was not observed to have an effect on NF-κB P65 or STAT3. Taxifolin also suppressed tumor growth in A549 xenograft BALB/c mice, with decreased SOX2 and OCT4 expression and inhibited PI3K and TCF4. CONCLUSIONS: In summary, taxifolin inhibited stemness and EMT in lung cancer cells possibly via the inactivation of PI3K and OCT4. Taxifolin could be a potential prodrug or serve as an adjuvant in lung cancer treatment.