Correlation between tyrosine hydroxylase activity, melanogenesis, and estradiol binding in human melanoma cells

Cytosols fractions from human mammary carcinoma, or malignant melanoma cells, and tyrosine hydroxylase (TH) bind 3H-estradiol (3H.E) with strong affinity. Monoclonal antibodies secreted by cloned cell hybrids which were formed by the fusion of murine myeloma cells with spleen cells from BALB/c mice pre-immunized with purified TH were used to differentiate between 3H.E-binding protein in the cytosols of various neoplastic cells. These monoclonal TH-antibodies inhibited the enzymic activity and the binding of 3H.e to TH or to cytosol fractions of melanotic melanoma cells, but had no effect on 3H.E binding to cytosol fractions from various mammary epithelial or carcinoma cell lines. Cultivation of estradiol-responsive melanotic melanoma cells in media supplemented with the TH-antibodies, caused loss of pigmentation, the cells became amelanotic and non-responsive to 17 beta-estradiol. The results indicate that the estrogen does not bind to melanoma cells via a receptor as for mammary carcinoma cells but to tyrosine hydroxylase.