Parathyroid protein prompts lung cancer metastasis to bone

Work in mice suggests that parathyroid hormone-related protein (PTHrP) is responsible for production of bone metastasis in human small-cell lung cancer (SCLC), Japanese researchers report. PTHrP may therefore be a therapeutic target.

Dr. Seiji Yano and colleagues at the University of Tokushima investigated the role of the protein by means of an osteolytic bone metastasis model involving human SCLC SNC-5 cells in immunodeficient mice. PTHrP is highly expressed by such cells.Repeated injection of anti-PTHrP neutralizing antibody (Ab) inhibited the formation of bone metastasis in a dose-dependent manner, the investigators report in the February 10th issue of the International Journal of Cancer. However, there was no significant effect on metastasis to visceral organs such as the liver and kidney.The treatment also reduced the elevated serum calcium level associated with inhibition of bone metastasis.Thus, Dr. Yano told Reuters Health, “We demonstrated that PTHrP produced by human small-cell lung cancer cells is responsible for the development of bone metastasis. Hypercalcemia may also be caused by PTHrP via the humoral hypercalcemia of malignancy mechanism.””Since bone metastasis and hypercalcemia are frequently observed in SCLC,” he concluded, “novel therapy targeting PTHrP–such as anti-PTHrP Ab–may be an approach to control bone metastasis and hypercalcemia in SCLC overexpressing PTHrP in humans.”(Source: Int J Cancer 2004;108:511-515: Reuters Health: David Douglas: February 17, 2004: Oncolink)