Differential estrogenic responsiveness of MCF-7 cells. Relationship to the presence of two different estrogen receptors.
Estradiol stimulation of thymidine incorporation and progesterone receptor synthesis is at a maximum in exponentially growing cells. These activities are found to disappear in confluent MCF-7 cells. Since no significant differences in the binding of estradiol to its receptor site (Kd = 10(-10) M, Bmax = 150 fm/mg protein) are observed in these two conditions, receptor structure was analyzed in both cell populations. Various methods demonstrated that receptor size is related to the state of confluence. The hydrodynamic properties of estradiol receptors complexed with 3H-estradiol from cells in the two different growth phases are similar in low ionic strength but different in high ionic strength media. Moreover, when the cell extracts are analyzed in denaturing conditions, cells which are sensitive to estradiol are found to contain a monomeric binding entity of 62 kD, whereas the unresponsive cells have a 47 kD binding entity.
INSERM U 168, Department of Endocrinology, CHU RANGUEIL, Toulouse, France.
J C
JC
Faye
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C
Toulas
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F
Bayard
D001943:Breast Neoplasms / Q000378:metabolism*; D002452:Cell Count; D004958:Estradiol / Q000502:physiology*; D005260:Female; D006801:Humans; D008970:Molecular Weight; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000096:biosynthesis; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured
D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D004958:Estradiol; D013936:Thymidine