Shikonin inhibits tumor invasion via down-regulation of NF-κB-mediated MMP-9 expression in human ACC-M cells

Objective: The aim of this study was to examine the anti-invasion effect of Shikonin on human high-metastatic adenoid cystic carcinoma (ACC-M) cells and to explain the possible molecular mechanism involved. Methods: The ACC-M cells were treated with Shikonin (0, 2.5, 5, 10 mu M) for 24 h. The protein levels and gelatinolytic activities of MMP-2 and MMP-9 were analyzed using Western blot and Gelatin zymography test, respectively. Matrigel invasion assays were used to investigate tumor invasive potential and electromobility shift assays were used to determine the activity of NF-kappa B. Results: The invasiveness of ACC-M cells was reduced in a dose dependent manner following 24-h treatment of up to 10 mu M of the Shikonin at which concentration no cytotoxicity occurred. The protein levels and gelatinolytic activities of MMP-9 were significantly suppressed by increasing Shikonin concentrations. The down-regulation of MMP-9 appeared to be via the inactivation of NF-kappa B as the treatment with Shikonin suppressed the protein level of phosphate-IkBa, which was accompanied by a decrease in DNA-binding level of the factor. Conclusions: Shikonin inhibits tumor invasion via downregulation of MMP-9 expression in ACC-M cells. Pharmacologic inhibition of the NF-kappa B-mediated MMP-9 expression by Shikonin might be a powerful treatment option for ACC patients in future.