Topical rapamycin inhibits tuberous sclerosis tumor growth in a nude mouse model.

BACKGROUND: Skin manifestations of Tuberous Sclerosis Complex (TSC) cause significant morbidity. The molecular mechanism underlying TSC is understood and there is evidence that systemic treatment with rapamycin or other mTOR inhibitors may be a useful approach to targeted therapy for the kidney and brain manifestations. Here we investigate topical rapamycin in a mouse model for TSC-related tumors. METHODS: 0.4% and 0.8% rapamycin ointments were applied to nude mice bearing subcutaneous, TSC-related tumors. Topical treatments were compared with injected rapamycin and topical vehicle. Rapamycin levels in blood and tumors were measured to assess systemic drug levels in all cohorts. RESULTS: Treatment with topical rapamycin improved survival and reduced tumor growth. Topical rapamycin treatment resulted in systemic drug levels within the known therapeutic range and was not as effective as injected rapamycin. CONCLUSION: Topical rapamycin inhibits TSC-related tumor growth. These findings could lead to a novel treatment approach for facial angiofibromas and other TSC skin lesions.

Tuberous sclerosis preclinical studies: timing of treatment, combination of a rapamycin analog (CCI-779) and interferon-gamma, and comparison of rapamycin to CCI-779.

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. CONCLUSION: 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.

Combination of a rapamycin analog (CCI-779) and interferon-gamma is more effective than single agents in treating a mouse model of tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is a familial tumor syndrome characterized by the development of hamartomas in the brain, heart, kidney, and skin. Disease-causing mutations in the TSC1 or TSC2 gene result in constitutive activation of the highly conserved mTOR signal transduction pathway, which regulates cell growth, proliferation, and metabolism. The mTOR inhibitor, rapamycin (sirolimus), reduces disease severity in rodent models of TSC, and is currently in phase II clinical trials. The cytokine interferon-gamma (IFN-gamma) is another potential therapeutic agent for TSC. A high-expressing IFN-gamma allele is associated with a lower frequency of kidney tumors in TSC patients, and treatment with exogenous IFN-gamma reduces the severity of TSC-related disease in mouse models. Here, we examine the effects of treating tumor-bearing nude mice with a combination of a rapamycin analog (CCI-779) and IFN-gamma. We observed that combination therapy was more effective than single agent therapy in reducing tumor growth and improving survival in this mouse model of TSC. Immunoblot and immunohistochemical analyses showed that tumors treated with CCI-779 plus IFN-gamma had decreased cell proliferation and increased cell death in comparison with untreated tumors or tumors treated with either agent alone. We also observed that CCI-779 resistance could develop with prolonged treatment. Taken together, our results show that targeting multiple cellular pathways is an effective strategy for treating TSC-related tumors, and underscore the importance of investigating combination therapy in future clinical trials for patients with TSC.

Efficacy of a rapamycin analog (CCI-779) and IFN-gamma in tuberous sclerosis mouse models.

Tuberous sclerosis complex (TSC) is a familial tumor disorder for which there is no effective medical therapy. Disease-causing mutations in the TSC1 or TSC2 gene lead to increased mammalian target of rapamycin (mTOR) kinase activity in the conserved mTOR signaling pathway, which regulates nutrient uptake, cell growth, and protein translation. The normal function of TSC1 and TSC2 gene products is to form a complex that reduces mTOR kinase activity. Thus, mTOR kinase inhibition may be a useful targeted therapeutic approach. Elevated interferon-gamma (IFN-gamma) expression is associated with decreased severity of kidney tumors in TSC patients and mouse models; therefore, IFN-gamma also has therapeutic potential. We studied cohorts of Tsc2+/- mice and a novel mouse model of Tsc2-null tumors in order to evaluate the efficacy of targeted therapy for TSC. We found that treatment with either an mTOR kinase inhibitor (CCI-779, a rapamycin analog) or with IFN-gamma reduced the severity of TSC-related disease without significant toxicity. These results constitute definitive preclinical data that justify proceeding with clinical trials using these agents in selected patients with TSC and related disorders.