title: Tuberous sclerosis preclinical studies: timing of treatment, combination of a rapamycin analog (CCI-779) and interferon-gamma, and comparison of rapamycin to CCI-779.
abstract: BACKGROUND
  Tuberous Sclerosis Complex (TSC) is an autosomal dominant hamartoma disorder with variable expression for which treatment options are limited. TSC is caused by a mutation in either the TSC1 or TSC2 genes, whose products, hamartin and tuberin, function as negative regulators in the highly-conserved mammalian target of rapamycin (mTOR) signaling pathway. Rapamycin (also known as sirolimus), an mTOR inhibitor, has been shown to reduce disease severity in rodent models of TSC and is currently being evaluated in clinical trials in human populations. The cytokine interferon-gamma (IFN-gamma) is also a potential therapeutic agent for TSC. A high-expressing IFN-gamma allele has been associated with reduced disease severity in human TSC patients and it has been shown in mouse models that treatment with exogenous IFN-gamma reduces disease severity.
  
  
  RESULTS
  Here, we examine the effects of treating Tsc2+/- mice at different time points with a rapamycin analog (CCI-779) as a single agent or with a combination of CCI-779 and IFN-gamma. We observed that administering a short course of CCI-779 or CCI-779 plus IFN-gamma reduced the severity of kidney lesions if administered after such lesions develop. As long as treatment is given after lesions arise, altering the time period during which treatment was given did not significantly impact the effect of the treatment on disease severity. We did not observe a significant benefit of combination therapy relative to treatment with a rapamycin analog alone in Tsc2+/- mice. We also compared timing of treatment and two mTOR inhibitors (rapamycin and CCI-779) in nude mice bearing Tsc2-/- tumors.
  
  
  CONCLUSIONS
  Preventing the genesis of TSC-related kidney lesions in Tsc2+/- mice is not an effective treatment strategy; rather, the presence of growing tumors appears to be the most important factor when determining an appropriate treatment schedule. Treatment with rapamycin was more effective in reducing tumor growth and improving survival in nude mice bearing Tsc2-/- tumors and also resulted in higher rapamycin levels in blood, brain, and kidney tissue than treatment with an equal milligram dose of CCI-779. We anticipate these results will influence future preclinical and clinical trials for TSC.
authors.affiliation: Translational Medicine Division, Department of Medicine, Brigham & Women's Hospital, Karp Family Research Laboratories, Boston, MA, USA. michael_p_messina@hotmail.com
authors.forename: Michael P
authors.initials: MP
authors.lastname: Messina
authors.forename: Aubrey
authors.initials: A
authors.lastname: Rauktys
authors.forename: Laifong
authors.initials: L
authors.lastname: Lee
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Dabora
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000998:Antiviral Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D005260:Female; D007371:Interferon-gamma / Q000008:administration & dosage / Q000627:therapeutic use*; D007674:Kidney Diseases / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D020123:Sirolimus / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014018:Tissue Distribution; D014402:Tuberous Sclerosis / Q000188:drug therapy* / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D000998:Antiviral Agents; C401859:temsirolimus; D007371:Interferon-gamma; D020123:Sirolimus