Abstract
Oleuropein and 3-hydroxytyrosol (3-HT) are natural polyphenols present in olive oil that are known to exhibit potent anti-oxidant activities and exert protective effects against a number of human diseases. In the liver, olive oil polyphenols have been demonstrated to prevent hepatocellular carcinoma (HCC) cell growth. However, little is known about their effects against HCC cell migration. Therefore, the present study investigated whether or not oleuropein and 3-HT were involved in the suppression of transforming growth factor-α (TGF-α)-induced migration of human HCC cells using human HCC-derived HuH7 cells. The TGF-α-induced migration of HuH7 cells was significantly and dose-dependently suppressed by oleuropein and 3-HT. This study group demonstrated previously that the TGF-α-induced activation of AKT and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) were involved in HuH7 cell migration. In addition to these protein kinases, the present study examined the involvement of TGF-α-induced activation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK) and Rho kinase in HuH7 cell migration. TGF-α-induced HuH7 cell migration was decreased by SB203580, a p38 MAPK inhibitor, and Y27632, a Rho kinase inhibitor. However, PD98059, an inhibitor of the upstream kinase activating ERK, did not suppress the TGF-α-induced migration of HuH7 cells. Although AKT, SAPK/JNK, p38 MAPK and Rho kinase pathways were suggested to be involved in the TGF-α-induced migration of HuH7 cells, 10-30 µM 3-HT did not exhibit any suppressive effect on the TGF-α-stimulated activities of these kinases. The results of the present study suggest that olive oil polyphenols suppressed the TGF-α-induced migration of HCC cells.