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

Two different forms of cDNA for F-TCF were isolated from cDNA library prepared with mRNA from human embryonic lung fibroblast, IMR-90 cells. One of them was completely identical to the cDNA for placenta type hepatocyte growth factor (HGF) and the other one was a variant cDNA for the HGF with a deletion of 15 base pairs in the coding region. The cDNAs were expressed in CHO cells and recombinant proteins were purified and characterized. The deleted form of recombinant F-TCF (rF-TCF) was slightly lower in heparin affinity than the intact form. Both rF-TCFs showed almost same dose-response curves for cytotoxicity on Sarcoma 180 or Meth A sarcoma cells. Dose-response curves for the stimulation of DNA synthesis in rat hepatocytes were also almost same before reaching maximal activity at 12.5 ng/ml but significantly different at higher concentrations. The deleted form of rF-TCF maintained maximal activity in the dose range of 12.5 to 100 ng/ml, although the intact form decreased the activity dose-dependently at more than 25 ng/ml. This suggests that the deletion of five amino acids results in a conformational change which alters heparin binding and hepatocyte growth stimulating activities.