title: Variation in the binding of 125I-labeled interferon-beta ser to cellular receptors during growth of human renal and bladder carcinoma cells in vitro.
abstract: Studies of various established human bladder and renal carcinoma cell lines cultured in vitro demonstrated the presence of specific, saturable, high affinity binding sites for 125I-labeled human interferon Beta ser IFN-beta ser). This recombinant produced interferon labeled with approximately one atom of 125I/molecule of IFN expressed minimal or no loss of antiviral activity. A single class of binding sites (1000-2000/cell) with an affinity constant of 10(10)-10(11) L/M was measured at 4 degrees C for cells exhibiting widely different sensitivity to the antiproliferative effect of IFN-beta ser. Major fluctuations in the binding of 125I-labeled IFN-beta ser to cellular receptors were observed during in vitro proliferation of four of five cell lines examined. A significant decrease (P less than 0.001) in specific binding was observed 48 h after cultures were established. Cell cycle analysis suggested that within the first 24 h and in the very late log and stationary phase of growth of ACHN (human renal carcinoma) cells, variations in the binding of 125I-labeled IFN-beta ser were partially attributable to binding fluctuations during the mitotic cycle. The 2- to 3-fold decline 24 h following plating of ACHN cells corresponded to a 70% decrease in the number of cells in G0-G1. T24 (human transitional cell carcinoma) and ACHN cells, synchronized by serum starvation, demonstrated increased binding of 125I-labeled IFN-beta ser 4-16 h following serum replenishment. This increase in receptor binding occurred prior to the onset of DNA and protein synthesis and was followed by a decline immediately prior to cell division. Binding site analysis indicated that the increased binding prior to DNA synthesis was due to a 5- to 6-fold increase in receptor affinity for the radiolabeled ligand. After an initial 40% decline in receptors per cell following serum stimulation, receptor concentration remained essentially unchanged. Induction of 2',5'-oligoadenylate synthetase in ACHN cells and antiproliferative activity in RT112, RT4, T24 (human transitional cell carcinoma), and ACHN cells by IFN-beta ser decreased significantly 48 h following plating. These changes in the biological activity of this interferon corresponded to growth related fluctuations in the IFN-beta ser binding.
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase / Q000096:biosynthesis; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology; D002453:Cell Cycle; D002478:Cells, Cultured; D006801:Humans; D007370:Interferon Type I / Q000378:metabolism* / Q000494:pharmacology; D000068556:Interferon beta-1a; D000068576:Interferon beta-1b; D016899:Interferon-beta; D007457:Iodine Radioisotopes; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000473:pathology; D011971:Receptors, Immunologic / Q000032:analysis / Q000378:metabolism*; D017471:Receptors, Interferon; D011994:Recombinant Proteins / Q000378:metabolism* / Q000494:pharmacology; D013696:Temperature; D001749:Urinary Bladder Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D007370:Interferon Type I; D007457:Iodine Radioisotopes; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D000068576:Interferon beta-1b; D016899:Interferon-beta; D015088:2',5'-Oligoadenylate Synthetase; D000068556:Interferon beta-1a