Metastasis to the liver is a frequent event in clinical oncology, the molecular mechanisms of which are not fully understood, We have recently reported a consistent overexpression of c-met in B16 melanoma cells selected in vivo for enhanced liver metastatic ability. Ln this study we address the question as to whether constitutive activation of c-met is a necessary and sufficient condition for enhanced Liver colonization by B16 melanoma cells, Different levels of c-met expression and/or activation in B16 cells were achieved by subcloning, or by c-DNA transfection with either HGF/SF or the oncogenic form of c-met (tpr-met), Metastatic ability of the different populations was then evaluated in vivo by the lung colonization (experimental metastasis) assay. Results indicate that c-met (but not tpr-met) activation in B16 melanoma cells may increase their liver colonizing potential, probably by enhancing motility and invasion in response to paracrine interactions with its ligand, C-met expression per se, however, is not able to change the organ specificity of the cells. C-met activation appears instead to be required at later stages of liver colonization by B16 melanoma cells, in order to enhance their site-specific metastatic ability. (C) 1998 Lippincott-Raven Publishers.
