Ougan (Citrus reticulata cv. Suavissima) flavedo extract suppresses cancer motility by interfering with epithelial-to-mesenchymal transition in SKOV3 cells

BACKGROUND: Ougan (Citrus reticulata cv. Suavissima) flavedo extract (OFE) exhibited potential anti-tumor effects with unclear underlying mechanisms. This study aims to evaluate the potential anti-metastatic activities of OFE on human ovarian cancer cells, and investigate its inhibitory effect on epithelial-to-mesenchymal transition (EMT). METHODS: Ougan fruits were harvested. Flavedo tissues were separated and made into freeze-dried powder. Then OFE were extracted from the powder. The components of OFE were identified by the high performance liquid chromatography system with a detection wavelength of 280 nm for flavanones and 330 nm for polymethoxylated flavones. Cell viability was assessed by Sulforhodamine B assay. The effects on cancer cell migration and motility were evaluated by wound-healing and transwell assays. The mechanisms of action were investigated by examining the modulation by OFE on EMT-related signaling pathways at the concentrations of 4 μg/mL and 20 μg/mL, using qRT-PCR and western blot analyses. RESULTS: Non-cytotoxic concentrations of OFE significantly suppressed the cellular migration (4 μg/mL, P = 0.005 vs. control group; 20 μg/mL, P = 0.003 vs. control group) and motility (4 μg/mL, P < 0.001 vs. control group; 20 μg/mL, P < 0.001 vs. control group) of SKOV3 cells, and inhibited transforming growth factor-β1 (TGF-β1)-induced E-cadherin loss (4 μg/mL, P = 0.002 vs. control group; 20 μg/mL, P = 0.001 vs. control group) and mesenchymal marker upregulation, e.g., N-cadherin (4 μg/mL, P = 0.027 vs. control group; 20 μg/mL, P = 0.013 vs. control group), vimentin (4 μg/mL, P = 0.036 vs. control group; 20 μg/mL, P = 0.015 vs. control group) and fibronectin (4 μg/mL, P < 0.001 vs. control group; 20 μg/mL, P < 0.001 vs. control group). CONCLUSIONS: The anti-metastatic ability of OFE inhibited EMT by interfering with the canonical TGF-β1-SMAD-Snail/Slug axis.