Gallic acid-capped gold nanoparticles inhibit EGF-induced MMP-9 expression through suppression of p300 stabilization and NFκB/c-Jun activation in breast cancer MDA-MB-231 cells

Triple-negative breast cancers (TNBCs) are highly invasive and have a higher rate of distant metastasis. Matrix metalloproteinase-9 (MMP-9) plays a crucial role in EGF/EGFR-mediated malignant progression and metastasis of TNBCs. Various studies have revealed that treatment with gallic acid down-regulates MMP-9 expression in cancer cells, and that conjugation of phytochemical compounds with gold nanoparticles (AuNPs) increases the anti-tumor activity of the phytochemical compounds. Thus, the effect of gallic acid-capped AuNPs (GA-AuNPs) on MMP-9 expression in EGF-treated TNBC MDA-MB-231 cells was analyzed in the present study. The so-called green synthesis of AuNPs by means of gallic acid was performed at pH 10, and the resulting GA-AuNPs had spherical shape with an average diameter of approximately 50 nm. GA-AuNPs notably suppressed migration and invasion of EGF-treated cells, and inhibited EGF-induced MMP-9 up-regulation. GA-AuNPs abrogated EGF-induced Akt/p65 and ERK/c-Jun phosphorylation, leading to down-regulation of MMP-9 mRNA and protein expression in EGF-treated cells. Meanwhile, EGF-induced p300 stabilization was found to be involved in MMP-9 expression, whereas GA-AuNPs inhibited the EGF-promoted stability of the p300 protein. Although GA-AuNPs and gallic acid suppressed EGF-induced MMP-9 up-regulation via the same signaling pathway, the effective concentration of gallic acid was approximately 100-fold higher than that of GA-AuNPs for inhibition of MMP-9 expression in EGF-treated cells to a similar extent. Collectively, our data indicate that, in comparison with gallic acid, GA-AuNPs have a superior ability to inhibit EGF/EGFR-mediated MMP-9 expression in TNBC MDA-MB-231 cells. Our findings also point to a way to improve the anti-tumor activity of gallic acid.