title: The estrogen-regulated 52 K protein adn plasminogen activators released by MCF7 cells are different.
abstract: In the MCF7 human breast cancer cell line, estradiol stimulates the synthesis of a 52 K secretory glycoprotein and has been reported to increase the plasminogen activator (PA) activity in the culture medium. Since one PA isozyme has a molecular weight close to 52 000 daltons under denaturing conditions, we asked whether the 52 K protein was a PA. The PA activity released in serum-free conditioned medium was evaluated by the increase in [125I]casein digestion observed in the presence of plasminogen. The 52 K protein was estimated by analysing the released proteins on SDS-polyacrylamide gel electrophoresis. When the conditioned medium was chromatographed on concanavalin A-Sepharose, the 52 K protein was retained on the gel, but not the PA. The two proteins also appeared different on the basis of their competing efficiency in a radioimmunoassay developed to quantify the 52 K protein. An antiserum against human urokinase failed to immunoprecipitate the 52 K protein. Under our culture conditions estradiol increased 52 K, but not PA, production. These results clearly indicate that the estradiol-regulated 52 K protein is not a plasminogen activator.
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D002460:Cell Line; D002846:Chromatography, Affinity; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000276:immunology; D010960:Plasminogen Activators / Q000378:metabolism*; D011863:Radioimmunoassay; D014568:Urokinase-Type Plasminogen Activator / Q000276:immunology
chemical_list: D009363:Neoplasm Proteins; C038865:estrogen regulated protein; D004958:Estradiol; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator