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 b y many normal tissues. Its diverse biologic activities in these tissue s are mediated by the PTH/PTHrP receptor through autocrine and paracri ne mechanisms. Recent data suggest that PTHrP and its receptor might a lso 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, a nd 50 (96%) of these tumors also expressed reactivity for the receptor . Although additional investigations are necessary for evaluation of t he role of PTHrP and PTH/PTHrP receptor in tumor pathogenesis, our cur rent study demonstrates the presence of this potential autocrine effec tor system in the great majority of invasive breast carcinomas.