Hepatocyte growth factor induces colonic cancer cell invasiveness via enhanced motility and protease overproduction. Evidence for PI3 kinase and PKC involvement

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Abstract
Tumour progression to the metastatic phenotype is mainly dependent on tumour cell invasiveness. Cell migration is a crucial step in this process. Here we investigate the effect of hepatocyte growth factor (HGF) on the induction of in vitro invasiveness of poorly aggressive Caco-2 colonic cancer epithelial cells. Invasion assays through a Matrigel barrier were performed. Proteases were assessed by zymography, reverse transcription–polymerase chain reaction and immunoblotting. Caco-2 cells were found to express HGF receptor but not HGF and to secrete several proteases, namely matrix metalloproteinase-1 (MMP-1), MMP-2, possibly MMP-9 and urokinase plasminogen activator (uPA). Exogenous HGF promoted invasiveness of Caco-2 cells through an artificial basement membrane matrix and enhanced their production of proteases. In addition, analyses of media at the end of invasion assays indicated that anti-HGF antibody inhibited protease production in parallel with cell invasion. The involvement of proteases in the HGF-induced invasion process was further investigated using either a synthetic general MMP inhibitor or neutralizing antibodies against MMPs or uPA. All components significantly inhibited HGF-promoted cell invasion. Moreover, specific inhibitors of PKCα/β1 and PI3 kinase also decreased both HGF-promoted cell invasion and protease expression in invasion assay media. Thus, our findings provide evidence that the process of HGF-activated invasiveness of Caco-2 cells involves PI3 kinase and PKC and results from close association of two events, stimulation of cell motile activity and concomitant overproduction of proteases, which permits cell migration through a degraded extracellular matrix.