Use of chromatofocusing to distinguish estradiol receptor from ovarian-dependent and -independent rat mammary tumors

• Published in: Cancer research (Chicago, Ill.) Vol. 43; no. 11; pp. 5235 - 5239
• Main Authors: Coufalik, A H, Feldman, M, Platica, M, Toth, L, Dreiling, D, Hollander, V P
• Format: Journal Article
• Language: English
• Published: United States 01.11.1983
• Subjects: Animals; Cell Line; Chromatography, Ion Exchange - methods; Cytosol - metabolism; Estradiol - metabolism; Female; Hydrogen-Ion Concentration; Mammary Neoplasms, Experimental - metabolism; Ovary - physiopathology; Rats; Rats, Inbred Strains; Receptors, Estradiol; Receptors, Estrogen - isolation & purification; Receptors, Estrogen - metabolism
• ISSN: 0008-5472

Cytosol estradiol receptor from MTW9-D (ovarian dependent) and MTW9-MtT (ovarian independent) rat mammary tumors were fractionated by chromatofocusing, a procedure which separates proteins on an ion-exchange column as a function of isoelectric point. Receptor from MTW9-D usually fractionated as three peaks with mean pH at peak height of 7.5, 6.8, and 6.0. The intermediate peak at pH 6.8 was present in 90% of MTW9-D tumors examined but in only 20% of MTW9-MtT tumors. Treatment of cytosols with 20 mM sodium molybdate or 50 mM leupeptin did not change the chromatofocusing profiles. The pI 6.8 fraction of receptor bound quantitatively to DNA-cellulose after ammonium sulfate precipitation, while receptor in the other two peaks bound much less. The quantitative binding of a fraction of estradiol receptor characteristic of MTW9-D to DNA is consistent with the greater binding of unfractionated cytosol receptor from MTW9-D to DNA than the binding of receptor from MTW9-MtT. Sucrose gradient analysis of the pI 6.8 receptor showed a sedimentation coefficient slightly less than ovalbumin with a Stokes radius of 26 A as determined by agarose chromatography. The correlation of receptor binding to DNA with response to ovariectomy might make this form of receptor a potential marker of hormonal responsivity in mammary tumors.