Efficacy of a Rapamycin Analog (CCI-779) and IFN- in Tuberous Sclerosis Mouse Models Laifong Lee, 1 Paul Sudentas, 1 Brian Donohue, 1 Kirsten Asrican, 1 Aelaf Worku, 1 Victoria Walker, 1 Yanping Sun, 2 Karl Schmidt, 2 Mitchell S. Albert, 2 Nisreen El-Hashemite, 1 Alan S. Lader, 1 Hiroaki Onda, 1 Hongbing Zhang, 1 David J. Kwiatkowski, 1 and Sandra L. Dabora 1* 1 Division of Hematology, Brigham and Women’s Hospital, Boston, MA 2 Department of Radiology, Brigham and Women’s Hospital, Boston, MA 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-) expression is associated with decreased severity of kidney tumors in TSC patients and mouse models; therefore, IFN- 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- 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. © 2004 Wiley-Liss, Inc. INTRODUCTION Tuberous sclerosis complex (TSC) is an autoso- mal-dominant tumor disorder that can affect mul- tiple organs, including the kidneys, brain, heart, and lungs (Gomez et al., 1999; Online Mendelian Inheritance in Man, 2003b). The incidence of TSC is 1:6,000, and an estimated 1–2 million individuals are affected worldwide (National Tuberous Sclero- sis Association, 1994). Sporadic pulmonary lym- phangioleiomyomatosis (LAM; Sullivan, 1998; On- line Mendelian Inheritance in Man, 2003a) is a progressive pulmonary disorder that is genetically related to TSC because somatic mutations in TSC1 or TSC2 have been identified in abnormal lung tissue from LAM patients (Carsillo et al., 2000). Renal manifestations in TSC and LAM patients are significant because 60%– 80% of TSC patients and 40%–50% of LAM patients develop kidney angiomyolipomas (tumors consisting of abnormal blood vessels, smooth-muscle cells, and fat cells; Sullivan, 1998; Gomez et al., 1999). TSC patients also can have a number of other medical problems, including epilepsy, cognitive impairment, behav- ioral problems, brain lesions (tubers and/or sub- ependymal nodules), skin tumors (facial angiofi- bromas), cardiac tumors (rhabdomyomas), kidney cysts, renal cell cancer, and pulmonary abnormali- ties including LAM (Gomez et al., 1999; Dabora et al., 2001; Franz et al., 2001). It is known that the TSC1 and TSC2 gene prod- ucts, hamartin and tuberin, form a complex that inhibits mammalian target of rapamycin (mTOR) kinase activity in a conserved cellular signaling pathway (the mTOR pathway) that regulates nu- trient uptake, cell growth, and protein translation (Consortium, 1993; van Slegtenhorst et al., 1997; Gao and Pan, 2001; Potter et al., 2001). A schematic diagram of the mTOR pathway is shown in Fig- ure 1a. Key proteins in this pathway include PI3kinase, Akt, TSC1/TSC2, Rheb, mTOR, p70S6kinase (S6K), S6 ribosomal subunit (S6), and 4E-BP1. TSC2 is negatively regulated by Akt via phosphorylation (Manning et al., 2002; Potter et al., 2002). More recently, it has been shown that under low-energy conditions, TSC2 is activated by LKB1 (a serine/threonine kinase tumor suppressor that is mutated in Peutz–Jeghers syndrome) through AMP-dependent protein kinase (Inoki et al., Supported by: TS Alliance (to S.D. and L.L.); LAM Foundation (to N.E. and D.K.); NIH (NHLBI); Grant number: HL007680 (to T.S. and L.L.); NIH (NINDS); Grant number: NS31535 (to D.K.); NIH (NCI); Grant number: CA086248 (to S.D.); NIH (NIDDK); Grant number: DK066366 (to S.D.). *Correspondence to: Sandra L. Dabora, Division of Hematology, Brigham and Women’s Hospital, 75 Francis Street, CHNRB 6th Floor, Boston, MA 02115. E-mail: sdabora@partners.org Received 16 April 2004; Accepted 2 September 2004 DOI 10.1002/gcc.20118 Published online 1 December 2004 in Wiley InterScience (www.interscience.wiley.com). GENES, CHROMOSOMES & CANCER 42:213–227 (2005) RESEARCH ARTICLE © 2004 Wiley-Liss, Inc.