Regulation of parathyroid hormone-related protein expression in MCF-7 breast carcinoma cells by estrogen and antiestrogens.
Expression of parathyroid hormone-related protein (PTHrP) in breast carcinoma is a frequent cause of the paraneoplastic syndrome of hypercalcemia. In response to treatment with estrogen or tamoxifen, some breast cancer patients also develop a transient hypercalcemia. Therefore, the effect of 17beta-estradiol (E2), tamoxifen, or its more potent metabolite, 4-hydroxytamoxifen (OH-tamoxifen), on PTHrP expression in an estrogen receptor (ER)-positive breast carcinoma cell line (MCF-7) was evaluated. E2 increased PTHrP mRNA levels in MCF-7 cells and stimulated PTHrP(1-86) release in a dose-dependent fashion (10(-10)-10(-6) M). Tamoxifen and OH-tamoxifen also stimulated PTHrP release in a concentration-dependent fashion that paralleled their relative ER binding affinities (10(-6) or 10(-8)-10(-6) M, respectively). Combined treatment with the partial estrogen agonist, OH-tamoxifen, and E2 decreased E2-stimulated PTHrP secretion in MCF-7 cells to the levels seen with OH-tamoxifen treatment alone. These results suggest that transient estrogen- or tamoxifen-induced hypercalcemia in patients with breast carcinoma may be a PTHrP-mediated effect that is a marker of ER positivity.
Funk
J L
JL
Department of Medicine, University of Arizona, Tucson, Arizona, 85724, USA.
Wei
H
H
D001943:Breast Neoplasms / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000209:etiology; D044162:Parathyroid Hormone-Related Protein; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004965:Estrogen Antagonists; C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D012333:RNA, Messenger; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol