Autocrine motility factor enhances hepatoma cell invasion across the basement membrane through activation of beta 1 integrins

Autocrine motility factor/phosphohexose isomerase (AMF/PHI) is a cytokine t hat is linked to tumor invasion and metastasis. In hepatocellular carcinoma (HCC) tissues, hepatoma cells produce AMF/PHI and its receptor, Mr 78,000 glycoprotein (gp78), is strongly detected in hepatoma cells invading into t he stroma and tumor thrombi in the portal vein. Here, we investigated the m echanism of hepatoma cell invasion through Matrigel induced by AMF/PHI usin g 3 hepatoma cell lines. Production of AMF/PHI, phosphorylation of MEK1/2, and Rho activity were investigated by immunoblotting. Expression of AMF/PHI and gp78 was observed by confocal fluorescence microscopy. The influence o f AMF/PHI on activated integrin pi subunit expression was evaluated by flow cytometry. Changes in invasion, adhesion, and motility induced by AMF/PHI were evaluated using chemoinvasion, adhesion, and phagokinetic track motili ty assays. The effect of AMF/PHI on matrix metalloproteinase (MMP) secretio n was evaluated by gelatin zymography, Hepatoma cells produced AMF/PHI and expressed gp78. Although AMF/PHI was ubiquitously detected, gp78 was strong ly expressed in migrating cells. AMF/PHI induced up-regulation of activated integrin pi subunit expression. AMF/PHI stimulated hepatoma cell invasion through Matrigel, and stimulated the adhesion, motility, and MMP-2 secretio n of hepatoma cells. The latter effects were suppressed by the function-blo cking antibody for integrin pi subunit. AMF/PHI also enhanced Rho activity and the phosphorylation of MEK1 and MEK 2. Our results indicate that AMF/PH I enhances hepatoma cell invasion through Matrigel in an autocrine manner b y stimulating the adhesion, motility, and MMP-2, secretion of these cells t hrough activation of beta1 integrins.