Nobiletin, a citrus flavonoid, suppresses invasion and migration involving FAK/PI3K/Akt and small GTPase signals in human gastric adenocarcinoma AGS cells

Nobiletin, a compound isolated from citrus fruits, is a polymethoxylated flavone derivative shown to have anti-inflammatory, antitumor, and neuroprotective properties. This study has investigated that nobiletin exerted inhibitory effects on the cell adhesion, invasion, and migration abilities of a highly metastatic AGS cells under non-cytotoxic concentrations. Data also showed nobiletin could inhibit the activation of focal adhesion kinase (FAK) and phosphoinositide-3-kinase/Akt (PI3K/Akt) involved in the downregulation of the enzyme activities, protein expressions, messenger RNA levels of matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-2 (MMP-9). Also, our data revealed that nobiletin inhibited FAK/PI3K/Akt with concurrent reduction in the protein expressions of Ras, c-Raf, Rac-1, Cdc42, and RhoA by western blotting, whereas the protein level of RhoB increased progressively. Otherwise, nobiletin-treated AGS cells showed tremendously decreased in the phosphorylation and degradation of inhibitor of kappaB alpha (I kappa B alpha), the nuclear level of NF-kappa B, and the binding ability of NF-kappa B to NF-kappa B response element. Furthermore, nobiletin significantly decreased the levels of phospho-Akt and MMP-2/9 in Akt1-cDNA-transfected cells concomitantly with a marked reduction in cell invasion and migration. These results suggest that nobiletin can reduce invasion and migration of AGS cells, and such a characteristic may be of great value in the development of a potential cancer therapy.