TNF and cancer: Current evidences suggest that malignant tumor cells accelerate bone remodeling at metastatic sites via secreting multiple osteolytic factors, such as parathyroid hormone-related protein (PTHrP), interleukin-6 (IL-6) and tumor necrosis factor (TNF), thereby stimulating the proliferation and differentiation of osteoclasts (OC) and potentiating osteolytic processes (3, 4).