Characterization of parathyroid hormone/parathyroid hormone-related protein receptor and signaling in hypercalcemic Walker 256 tumor cells.

Parathyroid hormone (PTH)-related protein (PTHrP) is the main factor responsible for humoral hypercalcemia of malignancy. Both PTH and PTHrP bind to the common type I PTH/PTHrP receptor (PTHR), thereby activating phospholipase C and adenylate cyclase through various G proteins, in bone and renal cells. However, various normal and transformed cell types, including hypercalcemic Walker 256 (W256) tumor cells, do not produce cAMP after PTHrP stimulation.

Effects of transforming growth factor beta1 on cell growth and parathyroid hormone-related protein in Walker 256 tumor cells.

Hypercalcemic strains of the rat Walker 256 (W256) tumor synthesize parathyroid hormone-related protein (PTHrP) and at least one of them produces an ill-defined transforming growth factor activity. We tested the production of transforming growth factor (TGF) beta by a hypercalcemic W256 tumor strain, and assessed its effects on tumor cell growth and PTHrP expression. We found that addition of TGF beta1 for 7 days inhibited cell growth ([3H]thymidine incorporation and cell number) dose dependently, between 0.

Proliferative effect of parathyroid hormone-related protein on the hypercalcemic Walker 256 carcinoma cell line.

The rat Walker 256 carcinoma is an animal model for humoral hypercalcemia of malignancy. This tumor produces and secretes parathyroid hormone (PTH)-related protein (PTHrP), a likely mediator for this syndrome. In this study, we investigated the effect of PTHrP on Walker 256 tumor cell proliferation.