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

Abstract

Aim: As one of the most widely used anti-diabetic drug for type II diabetes, metformin has been shown to exhibit anti-cancer activity 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 NAC. The effects of metformin on breast cancer cell proliferation were analyzed using MTT assay. The production of ROS was tested using 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 qRT-PCR and western blotting at mRNA and protein levels. The activation of Akt and NF-kB 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, metformin suppressed EGF-induced phosphorylation of Akt and NF-kB. ROS is involved in EGF-induced cancer invasion and activation of PI3K/Akt/NF-kB pathway.

Conclusion: Taken together, these data indicate that metformin suppresses EGF-induced breast cancer cell migration, invasion and EMT through the inhibition of the PI3K/Akt/NF-kB pathway. These results provide a novel mechanism to explain the role of metformin as a potent anti-metastatic agent in breast cancer cells.