A plasma-borne specific inhibitor of the proliferation of human estrogen-sensitive breast tumor cells (estrocolyone-I).
Charcoal-dextran stripped serum/plasma supplemented media specifically inhibit the proliferation of estrogen-sensitive cells in culture conditions; estrogens cancel this effect. Here, we further characterize this phenomenon using human estrogen-sensitive breast cancer MCF7 cells and human serum/plasma. The serum/plasma-borne inhibitory activity (estrocolyone-I) is a non-dialyzable, heat-stable (60 degrees C x 2 h), protease-sensitive macromolecule and it is not extractable by organic solvents. Estrocolyone-I activity is retained after dialysis against 6 M urea or 10-100 mM dithiothreitol; however, simultaneous treatment with 6 M urea and 10-100 mM dithiothreitol completely abolishes its inhibitory activity. The inhibitory effect of serum is not due to serum albumin, nor to estrogen trapping by albumin or by sex hormone-binding globulin. Substantial purification was achieved by a combination of chromatographic techniques (dye-affinity, ion exchange, hydrophobic interaction chromatography). Estrocolyone-I activity seems to be due to a protein of an apparent native Mw of 70-80 kDa and an isoelectric point of 4.5-4.8.
Soto
A M
AM
Tufts University Health Science Schools, Department of Anatomy and Cellular Biology, Boston, MA 02111.
Silvia
R M
RM
Sonnenschein
C
C
D001798:Blood Proteins / Q000302:isolation & purification*; D001943:Breast Neoplasms / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D002845:Chromatography; D002852:Chromatography, Ion Exchange; D004967:Estrogens / Q000494:pharmacology; D006801:Humans; D008970:Molecular Weight; D014407:Tumor Cells, Cultured
D001798:Blood Proteins; D004967:Estrogens; C079019:estrocolyone-I