[Bone in malignant disorders: introduction].

Patients harboring cancer and other tumors frequently exhibit such bone morbidity as metabolic bone diseases and bone metastases. Cancers produce and secrete cytokines and growth factors for their growth and survival. Cytokines are also produced by reacting immune systems. Those humoral factors, when produced in a sizable quantity, enter into the general circulation and become a causative principle for paraneoplastic syndrome. An example is parathyroid hormone-related protein (PTHrP) for humoral hypercalcemia of malignancy, and fibroblast growth factor 23 (FGF23) for oncogenic osteomalacia. In animal models, PTHrP appear to produce cancer-associated cachexia as well. Some particular cancers such as those of lung, prostate, breast and thyroid are prone to metastasize into bone resulting in metastatic bone disease. Interactions between these cancers and inhabitant bone cells and bone matrices constitute a favorable condition where particular cancer cells deposit and survive. A variety of principle factors, mostly signal materials, were identified that are responsible for these interactions and these principle factors can be a target for the development of new chemotherapeutic agents.