A new way to build bone

Bone Degeneration Although bone seems inert, it is in fact in constant flux, being continuously deposited by cells called osteoblasts and broken down by osteoclasts. Andrade et al. found that bone degeneration in diseases such as cancer and osteoporosis is caused at least in part by an overexuberant bone-destroying pathway. In this pathway, a signaling molecule, MSP (macrophage-stimulating protein), activates its receptor tyrosine kinase, RON, on host cells. Blocking this signaling by genetic or pharmacological means prevented bone breakdown in mouse models of metastasis and estrogen-depletion osteoporosis. This welcome approach may work in humans too: A RON kinase inhibitor slowed bone turnover in patients with cancer. Sci. Transl. Med. 9 , eaai9338 (2017).