Secretion of α-MSH-Like Molecules in a Human Melanoma Cell Line
Receptors for exogenous 125I-α-MSH were detected, at passage 54, on the human melanoma 809 cell line, using a specific hormone receptor assay. Thereafter (at pass. 80–90], receptors were consistently absent. To test the hypothetic blockade by MSH-like molecules, secreted by the non receptive cells themselves, a protein A immunoassay was devised to detect the presence of cross-reacting polypeptides on the cell surface. When receptivity for the hormone disappeared, α-MSH immunoreactivity was present at the cell surface. No re over, hormone receptive cells (at pass. <60) were able to interrant with serum-free conditioned medium obtained from non receptive cells (at pass. 94). These results suggest that 809 melanoma cells bear on their surface α-MSH-like peptides, which are recognized by highly specific α-MSH antibodies, and release into supernatant medium α-MSH-like molecules, able to interact with specific α-MSH receptors.
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