Mechanism Of Apigenin On Inhibition Of Migration, Invasion And Metastasis Of Human Colon Cancer Cell SW480 In Vitro And In Vivo

Objective: Apigenin, a widely distributed flavonoid in vegetables and fruits, has low toxicity, is non-mutagenic and reported to have many targets. Evidence indicates that apigenin can inhibit migration, invasion, and metastasis of some tumor cells but the mechanism behind this effect, specifically in colon cancer, is unclear. β-catenin is a crucial oncogene for the development of colon cancer and essential for migration and invasion of colon cancer cells. This study is designed to investigate: 1. The effects of apigenin on migration and invasion in SW480 cells. 2. The effects of apigenin on the expression and activation of β-catenin in SW480 cells. 3. The regulation of apigenin on migration and invasion by targeting Wnt/β-catenin signaling pathway. 4. The influence of apigenin on related proteins and downstream target proteins. 5. The impacts of oral adminstration of apigenin on the growth of xenograft tumors in nude mice. 6. The relationship between the effects of apigenin on migration, invasion, metastasis and the regulation of Wnt/β-catenin signaling pathway in SW480 cells.Methods: 1. MTT assay and colony formation assay are used to confirm the optimal concentration and acting time of apigenin. 2. Western blot, RT-PCR and immunofluorescent assays are performed to detect the expression of β-catenin,p-β-catenin and nucleus β-catenin. And the effect of apigenin on TCF/LEF transcriptional factor is detected via luciferase reporter assay. 3. Overexpression or knockdown β-catenin are applied to analyze the expression of Wnt/β-catenin signaling pathway related proteins and downstream target proteins after apigenin treatment. 4. Evaluation the effects of apigenin on migration and invasion by transwell assay. 5. Establishment of a xenograft model in nude mice to test the effects of oral administration of apigenin on the growth of xenograft tumors. 6. Establishment of experimental metastasis model in nude mice to test the effects of oral administration of apigenin on the distant lung and liver metastasis of SW480 cells in nude mice.Results: 1. Apigenin inhibited cell growth of SW480 in a dose- and time-dependent manner. 2. Apigenin inhibited migration and invasion of SW480 cells. 3. Apigenin decreased β-catenin protein and mRNA expression and induced phosphorylation of β-catenin and subsequent degradation, thereby preventedits nuclear translocation and activationin a dose- and time-dependent manner. 4. Migration and invasion of SW480 were significantly decreased after silencing β-catenin, indicating that apigenin can suppress migration and invasion of colon cancer cells via modulating the Wnt/β-catenin signaling pathway. 5. Apigenin inhibited β-catenin downstream protein expression that may be related to metastasis. Thus, apigenin suppresses activation of β-catenin signaling, decreases migration and invasion in colon cancer cells. 6. Apigenin inhibited the growth of tumor and distant lung metastasis of SW480 cells in nude mice.Conclusions: Our results suggest that by targeting β-catenin signaling, apigenin induces phosphorylation of β-catenin and subsequent degradation, prevents its nuclear translocation and activation of TCF/LEF transcription factor, therefore inhibits the expression of downstream target protein, finally, inhibits migration and invasion of human colon cancer cells. Apigenin also can inhibit the growth of xenograft tumor and the distant lung metastasis in nude mice. These findings help to address the question with common interests to the public of whether oral administration of apigenin is effective in prevention and therapy of colon cancers.