title: Osteolytic activity of Walker carcinosarcoma 256 is due to parathyroid hormone-related protein (PTHrP).
abstract: The hypercalcemic Walker carcinosarcoma 256 of the rat is an animal model for humoral hypercalcemia of malignancy. Previous in vivo studies suggested the production of a parathyroid hormone-related protein (PTHrP) by the Walker tumor. Therefore, we have measured immunoreactive PTHrP in serum-free conditioned medium from cells derived from this tumor using an antibody raised against human PTHrP(1-34). Walker tumor cell conditioned medium (WCM) displaced 125I-hPTHrP(1-34) from the antibody in a dose dependent manner, whereas control medium contained no immunoreactive PTHrP. In contrast, we detected no secretion of immunoreactive rat parathyroid hormone (rat PTH) by the Walker tumor cells using a midregional radioimmunoassay for rat PTH. WCM stimulated adenylate cyclase in osteoblast like cells, the dose-response curve paralleling that of hPTHrP(1-34). This effect could be inhibited by the PTH antagonist (8Nle, 18Nle, 34Tyr)bPTH(3-34) and by the addition of anti-hPTHrP(1-34) antibody. Bone resorbing activity of WCM in organ culture (calvaria of fetal rats) was not inhibited by indomethacin and glucocorticoids, suggesting a prostaglandin independent mechanism of osteoclast activation in this model.
authors.affiliation: Abteilung Innere Medizin I, Endokrinologie und Stoffwechsel, Klinikum der Universität Heidelberg, Germany.
authors.forename: S H
authors.initials: SH
authors.lastname: Scharla
authors.forename: H W
authors.initials: HW
authors.lastname: Minne
authors.forename: U G
authors.initials: UG
authors.lastname: Lempert
authors.forename: P
authors.initials: P
authors.lastname: Krieg
authors.forename: S
authors.initials: S
authors.lastname: Rappel
authors.forename: E
authors.initials: E
authors.lastname: Maurer
authors.forename: U
authors.initials: U
authors.lastname: Grohe
authors.forename: R
authors.initials: R
authors.lastname: Ziegler
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002279:Carcinoma 256, Walker / Q000201:enzymology / Q000503:physiopathology*; D003470:Culture Media; D000242:Cyclic AMP / Q000096:biosynthesis; D003907:Dexamethasone / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007457:Iodine Radioisotopes; D009363:Neoplasm Proteins / Q000032:analysis / Q000502:physiology*; D010014:Osteolysis / Q000503:physiopathology*; D010281:Parathyroid Hormone / Q000032:analysis / Q000502:physiology*; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000032:analysis / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D014407:Tumor Cells, Cultured
chemical_list: D003470:Culture Media; D007457:Iodine Radioisotopes; D009363:Neoplasm Proteins; C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D003907:Dexamethasone; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D007213:Indomethacin