Monoclonal anti-tyrosine hydroxylase antibodies.

Tyrosine hydroxylase (TH) and cytosol fractions from human mammary carcinoma and malignant melanoma cells bind 17 beta-[3H]estradiol with strong affinity. Sucrose density gradients suggested differences between the binding of 17 beta-[3H]estradiol to TH and melanoma cell cytosol compared with the binding of the estrogen to mammary carcinoma. Monoclonal antibodies secreted by cloned cell hybrids which were formed by the fusion of murine myeloma cells with spleen cells from BALB/c mice immunized with purified TH inhibited the enzymatic activity and the binding of 17 beta-[3H]estradiol to TH or to cytosol fractions of melanotic melanoma cells, but had no effect on 17 beta-[3H]estradiol 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 produced loss of pigmentation, and the cells became amelanotic and nonresponsive to 17 beta-estradiol. The results indicate that tyrosine hydroxylase of melanotic melanoma cells is an estrogen-binding protein.