mTOR may modulate osteoclastogenesis and reduce bone metastases in tumor-bearing mice by regulating the relationship between macrophages and T cells and the expression several of cytokines and costimulatory membrane receptors such as cytotoxic T-lymphocyte protein 4 (CTLA-4), programmed death 1 (PD-1) and so on (68). Here, CTLA4 is linked to neoplasm.