Selective inhibition of TNF-α-induced activation of mitogen-activated protein kinases and metastatic activities by gefitinib

We have reported that the selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib (‘Iressa’, ZD1839), suppressed intrahepatic metastasis of hepatocellular carcinoma CBO140C12 cells. In this study, we focused on the tumour necrosis factor-α (TNF-α) signalling pathways. Real-time reverse transcription–polymerase chain reaction showed that TNF-α mRNA was expressed in large quantities in the implanted tumour. Gefitinib inhibited EGF- but not hepatocyte growth factor (HGF)-induced activation of mitogen-activated protein kinase (MAPK) cascades, suggesting selectivity of the inhibitor. However, gefitinib inhibited the TNF-α-induced activation of MAPKs and Akt. In addition, TNF-α-induced metastatic properties including adhesion to fibronectin, mRNA expression of integrin αv, production of matrix metalloproteinase-9 and invasion were inhibited by gefitinib without affecting cell proliferation. Furthermore, the TNF-α-induced responses except for NF-κB activation were blocked by metalloprotease inhibitors, suggesting that gefitinib inhibited the transactivation of EGFR induced by TNF-α. These results suggest that the TNF-α signalling pathway is a possible target of gefitinib in suppressing the intrahepatic metastasis of hepatocellular carcinoma.