Coexpression of parathyroid hormone-related protein and its receptor in breast carcinoma: a potential autocrine effector system.

Parathyroid hormone-related protein (PTHrP), the pathogenic factor in most cases of humoral hypercalcemia of malignancy, is also expressed by many normal tissues. Its diverse biologic activities in these tissues are mediated by the PTH/PTHrP receptor through autocrine and paracrine mechanisms. Recent data suggest that PTHrP and its receptor might also influence the growth and metastatic spread of some cancers through similar local actions. Accordingly, immunohistochemical studies using murine monoclonal antibodies to detect coexpression of PTHrP and the PTH/PTHrP receptor were performed on 52 invasive breast carcinomas to assess the existence of this potential autocrine effector system. All of the 52 invasive breast carcinomas expressed reactivity for PTHrP, and 50 (96%) of these tumors also expressed reactivity for the receptor. Although additional investigations are necessary for evaluation of the role of PTHrP and PTH/PTHrP receptor in tumor pathogenesis, our current study demonstrates the presence of this potential autocrine effector system in the great majority of invasive breast carcinomas.