Sirolimus inhibits (a) T-lymphocyte activation and proliferation in response to antigenic and cytokine stimulation and (b) antibody production by inhibiting the mammalian target of rapamycin (mTOR), a key regulatory kinase that interferes with cell cycle progression from the G1 to S phase, via the formation of an immunosuppressive complex with FK binding protein-12 (FKBP-12) [162-163]. This agent is used to prevent rejection in solid organ transplantation and treat Kaposi sarcoma in renal transplant patients. This evidence concerns the gene MTOR and Kaposi's sarcoma.