A ROS/Akt/NF-Kappa B Signaling Cascade Mediates Epidermal Growth Factor-Induced Epithelial-Mesenchymal Transition and Invasion in Human Breast Cancer Cells

Background: As one of the most widely used anti-diabetic drugs for type II diabetes, metformin has been shown to exhibit anti-cancer ac-tivity in recent years. Epidermal growth factor (EGF) and its receptor, EGFR, play important roles in cancer metastasis in various tumors, including breast cancer. Epithelial-mesenchymal transition (EMT) is a critical process for cancer invasion and metastasis. In this study, we use EGF as a metastatic inducer to investigate the effect of metformin on cancer cell migration, invasion and EMT.Methods: Human breast cancer MCF-7 cells were exposed to EGF with or without metformin or N-acetyl cysteine (NAC). The effects of met-formin on breast cancer cell proliferation were analyzed using 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The production of reactive oxygen species (ROS) was tested using 2,7-dichlorodihydrofluorecein diacetate (DCFH-DA). The migratory and invasive abilities of tumor cells were analyzed using wound healing assay and transwell invasion assay, respectively. The expressions of E-cadherin, N-cadherin and Snail were tested using real-time quantitative polymerase chain reaction (qRT-PCR) and western blotting at mRNA and protein levels. The activation of protein kinase B (Akt) and nuclear factor kappa B (NF-Kappa B) were measured by western blotting.Results: Our results showed that metformin inhibited breast cancer cell proliferation in a dose-dependent manner with or without EGF. EGF-induced alterations in cell morphology that are characteristic of EMT were reversed by metformin. Metformin also inhibited the EGF-modulated expression of E-cadherin, N-cadherin and Snail and further suppressed cell invasion and migration. In addition, metform-in suppressed EGF-induced phosphorylation of Akt and NF-Kappa B. ROS is involved in EGF-induced cancer invasion and activation of phos-phatidylinositol 3-kinase (PI3K)/Akt/NF-Kappa B pathway.Conclusion: Taken together, these data indicate that metformin sup-presses EGF-induced breast cancer cell migration, invasion and EMT through the inhibition of the PI3K/Akt/NF-Kappa B pathway. These results provide a novel mechanism to explain the role of metformin as a po-tent anti-metastatic agent in breast cancer cells.