Abstract
We have recently established three esophageal squamous cell carcinoma (SCC) cell lines, YES-1, YES-2, and YES-3, which can grow in a protein-free medium. A-431 cells have been maintained in the same medium. The growth of YES-3 and A-431 cells seemed to be independent of various factors in serum. The amount of EGF receptors on these cells was measured by binding as say of membrane preparation using 125I-EGF. Of three SCC cell lines, YES-3 cells showed almost the same level of EGF receptors as A-431 cells, which contain a large amount of EGF receptors. But there was no relationship between the amount of EGF receptors and cell growth in the protein-free medium. Exogenous EGF inhibited the growth of A-431, YES-3 and YES-2 cells, but did not have any effect on YES-1 cells in that medium. Conditioned medium (CM) was obtained from the supernatants of culture at the subconfluent stage. EGF and TGFa were not detected in CM, and the growth of these cells was notaffected by CM. These observations suggest that the malignant potential of SCC with overexpression of EGFR did not result from tumor growth and EGF does not seem to act as an autocrine growth factor by means of extracellular secretion in these cells.
