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Keywords:

  • transforming growth factor alpha;
  • EGF receptor;
  • human melanocyte;
  • melanoma;
  • immunochemistry;
  • proliferation

Abstract: The epidermal growth factor receptor (EGFR) and its ligand, transforming growth factor alpha (TGFα), are reportedly involved in autocrine growth of melanoma cells. The signal pathway has also been implicated in early events of transformation, suggesting a function for EGFR in normal cells. This study reports the presence of EGFR in cultured melanocytes and examines some cellular responses to TGFα. Western analysis revealed 170 kDa bands in extracts of cultured neonatal human melanocytes, corresponding to the receptor Mr. Protein expression was more pronounced in cells during active growth. EGFR were less evident in cultures populated predominantly by melanized cells, indicating that receptor expression became reduced in differentiating cells. Immunocytochemistry confirmed these observations and also showed that EGFR reactivity was predominantly localized in the cell body but absent from dendrites. Addition of TGFα to early cultures induced a rapid increase in phosphotyrosine signal of the 170 kDa protein. Longer treatment (24–48 h) increased the intensity of the EGFR signal, suggesting that receptors had been upregulated. However, inclusion of TGFα in cultures did not result in an increase in cell numbers when compared to controls. The observations provide evidence of the existence of a receptor-mediated pathway in melanocytes which has transforming potential in vivo.