Mechanism of tumor-induced osteolysis

Osteolysis, the most common expression of bone tumor, can cause pain, patho logical fracture, epidural spinal cord compression and hypercalcemia. Multi nucleated osteoclast-like cells, the main agents in bone resorption, are nu merous in benign giant cell tumor of bone and can be recruited and activate d by various carcinoma cell lines in vitro in animal models. Polykarion mac rophages are also able to resorb bone matrix in a favourable tumoral enviro nment. Direct bone resorption by tumor cells has recently been described in vitro and in vivo in animals. The presence of diffusible substances such a s hormones, cytokines and growth factors creates a favourable microenvironm ent for stimulation of osteoclast-like cells and polykarion macrophages fun ctional ability to resorb bone matrix. These mediators act within a complex but still unelucidated network involving high cell production (tumor cells , normal and reactional stroma as well as hematopoietic cells) and many tar gets (tumor production (tumor cells, normal and reactional stroma as well a s hematopoietic cells) and many targets (tumor cells, monocyte/macrophage l ineage cells, and osteoclast-like cells). The presence in the same environm ent of all these stimulating factors for tumor cell growth and resorbing ab ility could explain the vicious circle of tumoral and osteolytic progressio n. A better understanding of the complex mechanism of tumor induced osteoly sis is essential for improving the conventional surgical approach to this p athology.