title: Co-purification of transforming growth factor beta-like activity with PTH-like and bone-resorbing activities from a tumor associated with humoral hypercalcemia of malignancy.
abstract: Humoral hypercalcemia of malignancy (HHM) is caused by a circulating bone-resorbing factor or factors. Suggestions as to the nature of this factor include PTH-like proteins, transforming growth factors, and bone-resorbing factors distinct from either of the first two classes of polypeptides. We investigated the occurrence of these three activities in a highly purified extract of the H-500 Leydig cell tumor which causes HHM when implanted into Fisher rats. PTH-like adenylate cyclase-stimulating activity (ACSA) was extracted from tumor tissue by sequential treatment with urea/HCl and ethanol/NaCl. Tumor extract was further purified by hydrophobic-interaction, gel-filtration, and reverse-phase HPLC steps to a specific activity of 1038 ng eq bPTH(1-34)/mg protein. Only the fraction pool containing ACSA demonstrated significant bone-resorbing (1.78-fold over basal) and transforming growth factor activity (epidermal growth factor (EGF)-dependent colony formation in soft agar suspension by NRK-49F indicator cells). A subsequent reverse-phase HPLC step produced material which contained both ACSA and transforming growth factor beta (TGF beta)-like activity in a single fraction. Whether the responsible mediator in this animal model has TGF beta-like properties as well as PTH-like and bone-resorbing activity remains to be determined.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000032:analysis; D001862:Bone Resorption; D002851:Chromatography, High Pressure Liquid; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006934:Hypercalcemia / Q000209:etiology / Q000378:metabolism*; D007984:Leydig Cell Tumor / Q000032:analysis / Q000150:complications*; D008297:Male; D010281:Parathyroid Hormone / Q000302:isolation & purification*; D010455:Peptides / Q000302:isolation & purification*; D051381:Rats; D015291:Transforming Growth Factors
chemical_list: D010281:Parathyroid Hormone; D010455:Peptides; D004815:Epidermal Growth Factor; D015291:Transforming Growth Factors; D000262:Adenylyl Cyclases