Intertumoral heterogeneity of receptor-tyrosine kinases expression in human melanoma cell lines with different metastatic capabilities

Human melanocytes respond to several growth factors whose receptors have tyrosine kinase activity. Abnormalities in the expression of tyrosine kinase receptors may play an important role in the initiation and progression of melanoma. We therefore determined the steady-state mRNA expression of five tyrosine kinase receptors, epidermal growth factor receptor (EGF-R), c-met, nerve growth factor receptor (NGF-R), colony-stimulating factor receptor (CSF-R) and c-kit, in eleven human melanoma cell lines with different metastatic potentials in nude mice. All cell lines except for one nonmetastatic line established from a primary melanoma lost expression of c-kit. Expression of the other four tyrosine kinase receptors varied among the lines. The expression level of individual tyrosine kinase receptor did not correlate with the metastatic potential of the cells. These results suggest that metastatic human melanoma cell lines are heterogeneous for expression of tyrosine kinase receptors, with each cell type manifesting a distinct repertoire of receptor tyrosine kinases. The different profile of tyrosine kinase activities in different metastatic melanomas complicates its use for prognosis.