The comparative biology of skeletal metastasis.

Bone metastasis, a very common sequelae of cancer, is often associated with great morbidity. Understanding the biology of bone metastases may lead to therapeutic interventions to target the metastases. In addition to replacing bone marrow elements, the presence of tumour cells in bone modulates the normal bone remodelling process. Some tumours result in primarily osteolytic bone lesions, whereas others are associated with osteoblastic bone lesions. In either case, the resulting changes in the bone structure result in weakened bone that induces pain and is predisposed to fracture. The mechanisms through which cancer cells modulate bone remodelling are not clearly defined, but ongoing research using a variety of animal models will hopefully provide clues to prevent or slow the progress of bone metastases.