Research

Equivalent benefit of mTORC1 blockade and combined PI3K-mTOR blockade in a mouse model of tuberous sclerosis

Kristen Pollizzi¹ , Izabela Malinowska-Kolodziej¹ , Michael Stumm² , Heidi Lane² and David Kwiatkowski¹

¹  Translational Medicine Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA

²  Novartis Institutes For BioMedical Research, Oncology Basel, Novartis Pharma AG, Switzerland

author email corresponding author email

Molecular Cancer 2009, 8:38doi:10.1186/1476-4598-8-38

Published:	15 June 2009

Abstract

Background

Tuberous sclerosis (TSC) is a hamartoma syndrome in which renal and lung tumors cause the greatest morbidity. Loss of either TSC1 or TSC2 in TSC hamartomas leads to activation of mTORC1 and suppression of AKT. Recent studies indicate that inhibition of mTORC1 with RAD001 (everolimus) leads to rebound activation of AKT, which could protect tumors from drug-induced cell death. Here we examine the potential benefit of inhibition of both mTOR and AKT signaling in a mouse model of TSC, using a dual pan class I PI3K/mTOR catalytic small molecule inhibitor NVP-BEZ235.

Results

Using ENU to enhance Tsc2^+- kidney tumor development, both RAD001 (10 mg/kg PO 5 d/week) and NVP-BEZ235 (45 mg/kg PO QD) had equivalent effects in suppressing tumor development during a 4 week treatment period, with a 99% reduction in tumor cell mass. Marked reduction in activation of mTORC1, induction of cell cycle arrest, and absence of apoptotic cell death was seen in mice treated with either drug. However, when either was discontinued, there was prompt recovery of tumor growth, with extensive proliferation.

Conclusion

Both mTORC1 blockade alone and combined PI3K-mTOR blockade lead to suppression of tumor development but not tumor elimination in this TSC model.