Dihydromyricetin suppresses cell metastasis in human osteosarcoma through SP-1-and NF-κB-modulated urokinase plasminogen activator inhibition

Background: Metastasis caused a decline in the 5-years survival rate of osteosarcoma. Therefore, developing new targeted therapeutics for osteosarcoma treatment is imperative. Dihydromyricetin (DHM) has several physiological functions: it counteracts inflammation, oxidation, and antitumor properties. However, the effects of DHM on osteosarcoma and its underlying mechanisms are still not well understood. Purpose: In this study, we investigated the antimetastatic properties of DHM in human osteosarcoma U-2 OS and HOS cells. Methods: The effects of DHM (0, 25, 50, 75, and 100 mu M) on cell viability, migration, and invasion were examined. Western blotting, RT-PCR, and quantitative real-time PCR (QPCR) were determined urokinase plasminogen activator (uPA) expression. The expression of transcriptional factor SP-1 and NF-kappa B was determined by using immunofluorescence assay, chromatin immunoprecipitation assay, and site-directed mutagenesis luciferase reporter. Results: We observed that DHM suppresses cell migration and invasion in osteosarcoma cell lines. In addition, DHM inhibits metastasis by downregulating urokinase plasminogen activator (uPA) expression. Moreover, realtime polymerase chain reaction and promoter activity assays revealed that DHM decreased uPA expression at transcription levels. Furthermore, the inhibition of uPA expression was associated with the suppression of SP-1 and NF-kappa B, which bind to the uPA promoter. Regardless of blocking or inducing the extracellular signal-regulated kinase (ERK) pathway, we verified that the DHM-related suppression of uPA and cell metastasis occurred through the p-ERK pathway. Conclusion: We are the first study to propose that DHM suppresses osteosarcoma metastasis through the ERK pathway and through the suppression of SP-1 and NF-kappa B to inhibit downstream uPA expression. DHM is a potential therapeutic agent for antimetastatic therapy against osteosarcoma.