Identification of a Novel 17,000-Dalton Parathyroid Hormone-like Adenylate Cyclase-stimulating Protein from a Tumor Associated with Humoral Hypercalcemia

Humoral hypercalcemia of malignancy is a common paraneoplastic syndrome which is characterized by hypercalcemia resulting from secretion by tumors of a circulating bone-resorbing factor. Evidence suggests that in many instances this factor is an adenylate cyclase-stimulating protein which shares features with, but is distinct from, parathyroid hormone (PTH). The current report describes the purification to homogeneity from a humoral hypercalcemia of malignancyassociated tumor of a novel, basic, highly potent PTHlike adenylate cyclase-stimulating protein. This factor differs from previously described PTH-like factors with respect to size, amino acid composition, and specific activity.