Parathyroid Hormone-Related Protein: A Developmental Regulatory Molecule Necessary for Mammary Gland Development

Parathyroid hormone-related protein (PTHrP) wasoriginally identified as the tumor factor responsiblefor a clinical syndrome known as humoral hypercalcemiaof malignancy. It is now appreciated that PTHrP3 is a developmental regulatory moleculeexpressed during the formation of a wide variety oforgans. Recently, our laboratory has demonstrated thatPTHrP is necessary for mammary gland development. Ourstudies have suggested that this molecule participatesin the regulation of epithelial-mesenchymal interactionsduring embryonic mammary development and perhaps alsoduring adolescent ductal morphogenesis. In addition, it has been suggested that PTHrP plays acritical role in the establishment of bone metastases inbreast cancer. In this article, we will discuss thecurrent knowledge of the mechanisms underlying PTHrPs actions during normal mammary development andin breast cancer.