Tamoxifen aziridine binding to cytosolic proteins from human breast specimens is negatively associated with estrogen receptors, progesterone receptors, pS2, and cathepsin-D.
[3H]Tamoxifen Aziridine ([3H]TAZ) is a derivative of the antiestrogen tamoxifen that covalently labels the Estrogen Receptor (ER), and perhaps other uncharacterized proteins. In a previous article we described that [3H]TAZ binds to a cytosolic protein from human uterine tissues that shares some, but not all, the ER properties. Here we have extended these studies to [3H]TAZ binding to cytosol proteins from human breast cancer specimens, and studied its quantitative association with other molecular markers and clinico-pathological variables. Cytosols were obtained in hypotonic buffer containing 20 mM molybdate and protease inhibitors, incubated with [3H]TAZ, and subjected to Sucrose Gradient Analysis (SGA). A [3H]TAZ labeled peak that consistently migrated with the 4S fractions was found in most of the assayed cytosols (range of 0 to 1278 fmol/ mg p.). The 4S peak of [3H]TAZ was partially inhibited by both estrogens and antiestrogens. When [3H]E2 was used instead of [3H]TAZ, only an 8S peak was detected. [3H]TAZ was covalently bound to a protein with an apparent MW of 65 kDa, as determined by SDS-PAGE and fluorography. The mean of [3H]TAZ binding was significantly higher in the subgroups of samples classified as ER-, PR-, pS2- or cathepsin D-, than in the respective positive subgroups (P < 0.01 in all the cases). [3H]TAZ binding was not associated with clinico-pathological variables, except that its mean was significantly larger in tumors larger than 5 cm than in smaller tumors. These results, and those previously reported, suggest that: 1) [3H]TAZ labels a cytosolic protein present in human breast cancers and uterine tissues that does not share all the ER properties, and 2) the [3H]TAZ binding by breast cancer cytosols is negatively associated with markers of estrogenic dependency, and its quantification may provide valuable information on antiestrogen responsiveness of a given tumor.
Navarro
D
D
Dept. Endocrinología Celular y Molecular, Centro de Ciencias de la Salud, Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain.
Doreste
H
H
Cabrera
J J
JJ
Morales
M
M
Díaz-Chico
J C
JC
Díaz-Chico
B N
BN
D014408:Biomarkers, Tumor; D001943:Breast Neoplasms / Q000378:metabolism*; D002402:Cathepsin D / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009376:Neoplasms, Hormone-Dependent / Q000378:metabolism*; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects*; D011960:Receptors, Estrogen / Q000187:drug effects; D011980:Receptors, Progesterone / Q000187:drug effects; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins
D014408:Biomarkers, Tumor; D004965:Estrogen Antagonists; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D013629:Tamoxifen; C031859:tamoxifen aziridine; D002402:Cathepsin D