Coexpression of the human Met receptor and its ligand, hepatocyte grow
th factor/scatter factor (HGF/SF), in NIH 3T3 fibroblasts causes the c
ells to become tumorigenic in nude mice. The resultant tumors display
lumen-like morphology, contain carcinoma-like focal areas with interce
llular junctions resembling desmosomes, and coexpress epithelial (cyto
keratin) and mesenchymal (vimentin) cytoskeletal markers. The tumor ce
lls also display enhanced expression of desmosomal and tight-junction
proteins. The apparent mesenchymal to epithelial conversion of the tum
or cells mimics the conversion that occurs during embryonic kidney dev
elopment, suggesting that Met-HGF/SF signaling plays a role in this pr
ocess as well as in tumors that express both epithelial and mesenchyma
l markers.