Tumor cytotoxic factor/hepatocyte growth factor from human fibroblasts: cloning of its cDNA, purification and characterization of recombinant protein

Hepatocyte growth factor/scatter factor, liver regeneration and cancer metastasis

Hepatocyte growth factor (HGF) is the most potent stimulator of hepatocyte growth and DNA synthesis identified; it is now known to be the same molecule as scatter factor, which increases the motility of a variety of cell types. HGF is becoming recognized as one of the most important factors in the regulation of liver regeneration after surgical resection or chemical damage. HGF is produced by several tissues, including neoplasms; it can therefore provide a stimulus for increased motility of malignant cells by both a paracrine and autocrine mechanism. The receptor for HGF has been identified as the product of the oncogene c-met, raising the possibility that this gene plays a key role in facilitating cellular invasion. HGF may therefore be important not only for liver cell growth but also in metastasis. This article summarizes the current position of research on HGF, and presents both clinical and scientific evidence that strongly implicates this factor in liver regeneration and cancer invasion and metastasis.

Internalization and degradation of hepatocyte growth factor in hepatocytes with down-regulation of the receptor/c-Met

Hepatocyte growth factor (HGF) promotes proliferation of cultured hepatocytes by its interaction with cell surface receptors. In this paper, we examined the metabolic fate of HGF using hepatocytes. Kinetic analysis using [125I]HGF showed that 40% of surface-bound HGF was rapidly internalized in hepatocytes within 30 min at 37 degrees C. Under these conditions, the amount of HGF-bound c-Met, the high-affinity receptor, decreased from the cell surface. Furthermore, the internalized HGF was degraded and released from the cells. These results indicate that cell surface-bound HGF is internalized and degraded by the receptors, including c-Met, on hepatocytes.

Characterization of the promoter region of the rat hepatocyte-growth-factor/scatter-factor gene

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent mitogen for hepatocytes in primary culture. In response to liver damage, the levels of HGF/SF mRNA change in various tissues. In this study, we isolated a genomic DNA fragment containing the promoter region of the rat HGF/SF gene and analyzed transcription-initiation sites and their utilization in response to acute liver injury. Rat HGF/SF-mRNA synthesis starts from at least three sites in the liver, spleen and kidney. One of these sites is preferentially utilized in the liver and spleen in response to acute liver injury. In the 5' flanking region, several cytokine-related sequence elements that might be involved in the regulation of HGF/SF-gene expression are located near the transcription-initiation sites. The effects of cytokines related to these sequence elements on the production of HGF/SF mRNA were examined using a cell culture system. Transforming growth factor-beta 1 (TGF-beta 1) inhibits the production of HGF/SF mRNA by Shay granulocytic sarcoma-derived cells. The TGF-beta 1-inhibitory element, one of the sequence elements present in the promoter sequence, may mediate the inhibition of HGF/SF-gene expression by TGF-beta 1.

The presence of scatter factor in patients with metastatic spread to the pleura

Pleural effusion fluid obtained from eleven patients with metastatic spread to the pleura was screened for the ability to cause the dispersal--'scattering'--of MDCK colonies in vitro. Four of these samples proved to be positive using this assay. Of these two had titres high enough to warrant further purification on a cation exchange Mono S column. Active material from both lung samples, eluted at the same positions as factor from cultured human lung fibroblasts (MRC-5) and human placenta but in a slightly different position to murine scatter factor. In both cases the semi-purified active agent was identified as hepatocyte growth factor/scatter factor (HGF/SF) using an ELISA detection system specific for human HGF/SF. This is the first report identifying the presence of significant amounts of HGF/SF in the pleura of patients where malignant spread has occurred.

Effects of protein kinase inhibitors on the mitogenic activity of human hepatocyte growth factor on rat hepatocytes in primary culture

To evaluate the role of protein phosphorylation reactions in signal transduction of human hepatocyte growth factor (hHGF), now known to be the same protein as the scatter factor and tumor cytotoxic factor, we examined the effects of various inhibitors of protein kinases on the mitogenic activity of hHGF on rat hepatocytes in primary culture. Genistein, a specific inhibitor of tyrosine kinase, dose-dependently inhibited the effect of hHGF in stimulating DNA synthesis of hepatocytes. By contrast, 1-(5-isoquinolinesulfonyl)-2- methylpiperazine (H7), a specific inhibitor of protein kinase C, potentiated the stimulatory effect of hHGF on DNA synthesis of hepatocytes. H7 was effective at over 2 micrograms/ml and potentiated the effect of hHGF over 2-fold at 20 micrograms/ml. On the other hand, an inhibitor of Ca++/calmodulin-dependent protein kinase inhibited both the basal and hHGF-stimulated DNA synthesis in the cells, whereas an inhibitor of cyclic nucleotide-dependent protein kinases had little effect on the action of hHGF. These results suggest that tyrosine phosphorylation is required for stimulation of hepatocyte DNA synthesis by hHGF and that the action of hHGF is negatively regulated by protein kinase C activation.