Wistar Institute of Anatomy and Biology , Philadelphia , Pennsylvania .
J Invest Dermatol 97 : 20-6 ( 1991)
Abstract
In a panel of metastatic melanoma cell lines we found steady-state mRNA transcripts for multiple growth factors including basic fibroblast growth factor ( bFGF ) , platelet-derived growth factor ( PDGF)-A , PDGF-B , transforming growth factor ( TGF)- beta 1 , TGF- alpha , melanoma growth-stimulating activity ( MGSA ) , interleukin ( IL)-1 alpha , and IL-1 beta but not insulin-like growth factor ( IGF)-1 or IGF-2 .
Expression of growth factor genes was constitutive because prior to RNA extraction melanoma cells were maintained in a chemically defined culture medium free of exogenous growth factors .
Each of four cell lines had an individual pattern of expression of either two , four , five , or seven growth factors ; however , all cell lines shared expression of the bFGF gene .
Two strains of normal melanocytes expressed TGF- beta 1 but not bFGF , PDGF , TGF- alpha , or MGSA mRNA at detectable levels .
We tested growth-modulatory effects of the growth factors most frequently expressed by melanoma cells ( bFGF , TGF- alpha , TGF- beta , PDGF ) .
None of these stimulated melanoma cell growth consistently , whereas exogenous , acid-activated TGF- beta inhibited melanoma growth at concentrations greater than 10 ng/ml , suggesting that bioactive TGF- beta may represent a physiologic growth inhibitor .
Neither neutralizing antisera to PDGF or TGF- alpha nor a monoclonal antibody to the epidermal growth factor ( EGF)-receptor inhibited melanoma cell growth .
Our results indicate that multiple growth factors are expressed simultaneously and constitutively by melanoma cells but not normal melanocytes in culture .
Expression of bFGF is a common feature underscoring the significance of bFGF as an autocrine factor for melanoma cells as described earlier .
Secreted PDGF and TGF- alpha are apparently not involved in or not essential for autocrine growth stimulation of melanoma cells .