title: Quantitative comparison of PTH1R in breast cancer MCF7 and osteosarcoma SaOS-2 cell lines.
abstract: The aim of the present study was to compare the classical parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) receptors in MCF7 breast cancer cells with SaOS-2 osteosarcoma cell line. Quantitative binding showed that (125)I-PTHrP-1-34(Tyr) binds with a single binding site in both cells. However (125)I-PTHrP-1-34(Tyr) has higher affinity binding in MCF7 (K(D) = 1.88 +/- 0.08 nM) than in SaOS-2 cells (K(D) = 4.4 +/- 0.185 nM). The competitive binding using 3.3 nM (125)I-PTHrP-1-34(Tyr) with increasing amounts (0.33-33 nM) of unlabelled human PTHrP-1-34, PTHrP-7-34, PTHrP-1-86 His(5)-PTHrP-1-36, His(5)-Phe(23)-PTHrP-1-36 or PTH-1-34 revealed different displacements. In SaOS-2 the PTHrP-7-34 and PTHrP-1-86 caused similar displacement compared with 73% by PTH-1-34 and 70% by PTHrP-1-34. However, in MCF7, PTHrP-7-34, PTHrP-1-86 and PTH-1-34 displaced by 54%, 72% and 67%, respectively, compared to 87% by PTHrP-1-34. The His(5)-Phe(23)-PTHrP-1-36 caused an increase in the K(D) from 2.0 +/- 0.03 nM to 2.75 +/- 0.045 nM in MCF7 cells, but had no significant effect in SaOS-2 cells. The PTH/PTHrP receptor in both cell lines revealed a single 85 KDa band with different intensity. Our results suggest that the PTH/PTHrP receptor in MCF7 cells has higher binding affinity for PTHrP than PTH compared to the receptor in SaOS-2 cells.
authors.affiliation: Department of Biochemistry, College of Science #5, King Saud University, Riyadh, Saudi Arabia. msalokail@yahoo.com
authors.forename: Majed S
authors.initials: MS
authors.lastname: Alokail
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Peddie
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D008024:Ligands; D012516:Osteosarcoma / Q000378:metabolism*; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000378:metabolism*
chemical_list: D008024:Ligands; C473449:PTH1R protein, human; D044168:Receptor, Parathyroid Hormone, Type 1