Gene regulation by steroid hormones.

The protective effects of estrogen on the cardiovascular system

The Structural Basis of Estrogen Receptor/Coactivator Recognition and the Antagonism of This Interaction by Tamoxifen

We have cloned and sequenced the complete complementary DNA of the oestrogen receptor (ER) present in the breast cancer cell line MCF-7. The expression of the ER cDNA in HeLa cells produces a protein that has the same relative molecular mass and binds oestradiol with the same affinity as the MCF-7 ER. There is extensive homology between the ER and the erb-A protein of the oncogenic avian erythroblastosis virus.

Human oestrogen receptor cDNA: sequence, expression and homology to v-erb-A

Pathological prognostic factors in breast cancer.

Poly(A)+ RNA isolated from the human breast cancer cell line MCF-7 was fractionated by sucrose gradient centrifugation and fractions enriched in estrogen receptor (ER) mRNA were used to prepare randomly primed cDNA libraries in the lambda gt10 and lambda gt11 vectors. Clones corresponding to ER sequence were isolated from both libraries after screening with either ER monoclonal antibodies (lambda gt11) or synthetic oligonucleotide probes designed from two peptide sequences of purified ER (lambda gt10). Five cDNA clones were isolated by antibody screening and five were isolated after screening with synthetic oligonucleotides. The two largest ER cDNA clones, lambda OR3 (1.3 kilobase pairs) and lambda OR8 (2.1 kilobase pairs), isolated by using antibodies and oligonucleotides, respectively, were able to enrich selectively for ER mRNA by hybrid-selection. Furthermore, lambda OR8 contains the DNA sequence expected from the two ER peptides and crosshybridizes with each of the other ER cDNA clones. These results demonstrate that the clones isolated correspond to the ER mRNA sequence. Use of lambda OR8 as a hybridization probe revealed a single poly(A)+ RNA band of approximately equal to 6.2 kilobase pairs in the ER-containing human breast cancer cell lines MCF-7 and T47D. In contrast, no hybridization was seen in the human ER-negative cell line HeLa. The same probe hybridizes to a chicken gene that is expressed in oviduct tissue as a 7.5-kilobase-pair poly(A)+ RNA.

https://www.pnas.org/content/pnas/82/23/7889.full.pdf

Cloning of the human estrogen receptor cDNA.

Extranuclear estrogen receptor protein (estrophilin) of MCF-7 human breast cancer cells was purified by passage of the cytosol fraction of a cell homogenate through an affinity column of estradiol linked to Sepharose by a substituted di-n-propyl sulfide bridge in the 17 alpha position. Elution with 50 micro M [3H]estradiol in 10% (vol/vol) dimethyl formamide/0.5 M sodium thiocyanate gave 40% recovery of [3H]estradiol-estrophilin showing 14% of the specific radioactivity expected for the pure complex. Serum from a Lewis rat immunized with this partially purified estradiol-receptor complex contained antiestrophilin antibodies that reacted not only with nuclear and extranuclear estradiol-receptor complexes from MCF-7 cells but also with estrophilin from rat, calf, and monkey uterus, hen oviduct, and human breast cancers. Splenic lymphocytes from the immunized rat were fused with cells of two different mouse myeloma lines (P3-X63-Ag8 and Sp2/0-Ag14) to yield hybridoma cultures, 2% of which produced antibodies to estrophilin. After cloning by limiting dilution, three hybridoma lines secreting antiestrophilin were expanded in suspension culture and as ascites tumors in athymic mice to provide substantial quantities of monoclonal antibodies that recognize mammalian but not avian estrophilin and that show different degrees of reactivity with receptor from nonprimate sources. By growing the clone from Sp2/0 in the presence of [35S]methionine, radiolabeled monoclonal IgG has been prepared. These monoclonal antibodies should prove useful in the study of estrogen receptors of human reproductive tissues, in particular for the radioimmunochemical assay and immunocytochemical localization of receptors in breast cancers.

E V Jensen

Papers

Cloning of the human estrogen receptor cDNA.

Monoclonal antibodies to human estrogen receptor.

Immunochemical studies of estrogen receptors.

Cloning of the human oestrogen receptor cDNA.

Estrogen receptors, antibodies and hormone dependent cancer.