PRODUCTION OF PARATHYROID-HORMONE AND PARATHYROID-HORMONE-RELATED PROTEIN BY BREAST-CANCER CELLS IN CULTURE

Parathyroid-hormone-related protein (PTHrP) has been implicated in the origin of malignant hypercalcaemia. However, PTHrP production is not restricted to neoplastic cells, it is widespread among a variety of no rmal cell types and tissues. A physiological role for PTHrP has not be en well defined. We describe a case of breast cancer with bone metasta ses and humoral hypercalcaemia of malignancy, with high levels of plas ma C-terminal parathyroid hormone (PTH), mid-molecule PTH and PTHrP. C ells from breast cancer biopsies were cultured and medium samples assa yed for the C-terminal and mid-molecule fragments, intact PTH and PTHr P. The data indicate a progressive increase in both PTH fragments and PTHrP levels, over a period of 30 days. No temporal parallelism exists between PTH fragments and PTHrP concentrations, the former being maxi mum at the 14th day, and the latter at the 30th day from the beginning of the culture. Our results indicate a coproduction of PTH and PTHrP by the breast cancer cells both in vivo and in vitro.