Anti-metastasis activity of curcumin against breast cancer via the inhibition of stem cell-like properties and EMT

Background: Curcumin is a polyphenolic compound with potent chemopreventive and anti-cancer efficacy. Purpose: To explore the potential anti-metastasis efficacy of curcumin in breast cancer stem-like cells (BCSCs), which are increasingly considered to be the origin of the recurrence and metastasis of breast cancer. Methods: A CCK8 assay was performed to evaluate cell viability, and a colony formation assay was conducted to determine cell proliferation in MCF-7 and MDA-MB-231 adherent cells. Transwell and wound healing assays were used to detect the effect of curcumin on cell migration and invasion in MDA-MB-231 cells. Mammospheres were cultured with serum free medium (SFM) for three generations and the BCSC surface marker CD44 ⁺ CD24 ⁻ / ^low subpopulation was measured by flow cytometry. Mammosphere formation and differentiation abilities were determined after cell treatment with curcumin. Then, a reverse transcription-quantitative polymerase chain reaction assay was conducted to detect the relative mRNA level of epithelial-mesenchymal transition (EMT) marker genes and western blot analysis was performed to determine the protein expression of stem cell genes in mammospheres treated with curcumin. Results: Curcumin exhibited anti-proliferative and colony formation inhibiting activities in both the MCF-7 and MDA-MB-231 cell lines. It also suppressed the migration and invasion of MDA-MB-231 cells. The CD44 ⁺ CD24 ⁻ / ^low subpopulation was larger in mammospheres when MCF-7 and MDA-MB-231 adherent cells were cultured with SFM. Further studies revealed that curcumin inhibited mammosphere formation and differentiation abilities. Moreover, curcumin down-regulated the mRNA expression of Vimentin, Fibronectin, and β-catenin, and up-regulated E-cadherin mRNA expression levels. Western blot analysis demonstrated that curcumin decreased the protein expression of stem cell genes including Oct4, Nanog and Sox2. Conclusion: The results of the present study suggest that the inhibitor effects of curcumin on breast cancer cells may be related to resistance to cancer stem-like characters and the EMT process. These data indicate that curcumin could function as a type of anti-metastasis agent for breast cancer.