[Cytokines as markers of osteolysis in the diagnostics of patients with bone metastases].

In normal bone there are two essential processes of bone turnover, resorption and formation, which are disrupted by bone metastases. Two types of bone metastases are known, i.e. osteolytic lesions with dominant bone resorption and osteosclerotic tumors with enhanced osteoblastic bone formation. Numerous cytokines and growth factors regulate the activity of osteoclasts and/or osteoblasts in endo- or paracrine ways, playing crucial roles in the processes of bone turnover. Bone metastases are often the consequences of certain malignant tumors, such as breast, prostate, lung, and renal cancer. The diagnosis of bone metastasis is essential for a determination of the clinical stage of cancer and appropriate treatment. Tumor markers are useful in diagnosis, prognosis, staging, and, especially, monitoring treatment. Tumor markers are also useful in detecting bone metastases. There is growing evidence that various cytokines, especially M-CSF, TGFbeta, TNFalpha, and IL-6 and IL-7, may be new tumor markers useful in the diagnosis of neoplastic disease. The processes of bone turnover in normal bone and metastatic tumors as well as the significance of the most important cytokines in the development of osteolytic metastases and the possibility of their use in the diagnosis of the most frequent cancers presenting bone metastases are described in this article.