Sirolimus is one of the intensively investigated drugs with pluripotent 
activities. It binds to its intracellular receptor FKBP12 (FK506-binding protein 
12), a member of the family of FK506-binding proteins, and inhibits the activity 
of mTOR, a serine/threonine kinase involved in numerous cell processes linked to 
cell growth control. The drug is currently registered for the prophylaxis of 
organ rejection and for use in coronary stents. However, unique characteristics 
of sirolimus make it a good candidate for anti-cancer therapy. Indeed, phase II 
and III clinical studies in humans with several types of neoplasms are already 
under way. The review describes molecular activity of sirolimus and its analogs, 
characteristic for specific applications, in view of very recent advances 
involving tuberous sclerosis complex (TSC)-mediated signaling pathways. Current 
studies with sirolimus performed in tuberous sclerosis animal models are 
presented. Possible application of sirolimus for treating tuberous sclerosis, 
disease caused by mutations of TSC proteins, is discussed.