The endocrine background of human renal cell carcinoma. I. Binding of the highly potent progestin R 5020 by tumour cytosol.

Based on the potential sensitivity of the growth of human renal cell carcinoma, tumour tissue from 88 patients was analysed for progestin receptors. With the dextran-coated charcoal assay, cytoplasmic components which bound the potent progestin R 5020 specifically and with high affinity could be detected in 42% of the carcinomas. The apparent dissociation constant of the R-5020-binder complex amounted to 3.1 +/- 1.2 X 10(-8) mol/l. Sedimentation in sucrose gradients revealed the bulk of these components to be in the 4-S region. The ligand specificity for binding to these sites indicated a requirement for progestins. Despite the enormous case material investigated, we were unable to confirm the presence of the high receptor concentrations reported in the literature.