L-Carnosine Inhibits Metastasis of SK-Hep-1 Cells by Inhibition of Matrix Metaoproteinase-9 Expression and Induction of an Antimetastatic Gene, nm23-H1

Abstract

Antioxidants have been suggested to inhibit the expression of matrix metalloproteinases (MMPs), especially MMP-9, which plays a critical role in tumor metastasis. Because of its antioxidant activity and the ability to chelate divalent cations, L-carnosine (LC) was tested for inhibition of MMP-9 in a highly invasive hepatocarcinoma, SK-Hep-1 cells. We found that LC (50–1,000 μ M) did not directly inhibit the activity of MMP-9 in a cell-free system. However, LC significantly inhibited the expression and activity of MMP-9 protein in SK-Hep-1 cells [inhibitory concentration of 50% (IC 50 )| = 105 and 63 μ M, respectively). Whereas LC did not inhibit the viability of SK-Hep-1 cells at concentrations up to 1,000 μ M within 3 days of incubation, this dipeptide significantly inhibited cell migration (IC 50 = 82 μ M) and invasion (IC 50 = 113 μM). LC significantly (P < 0.05) and dose dependently enhanced the expression of an antimetastatic gene, nonmetastatic cells 1, protein (nm23)-H1, at both protein and messenger ribonucleic acid (mRNA) levels. MMP-9 activity inversely correlated significantly with the expression of protein (r 2 = 0.77, P < 0.001) and mRNA (r 2 = 0.65, P < 0.001) of nm23-H1 in LC-treated cells. Thus, LC can inhibit the migration and invasion of SK-Hep-1 cells, and the effect is likely associated with upregulation of nm23-H1 and downregulation of MMP-9 expression.