Therefore, the CHOI criteria have been studied using both tumor size and density variations to evaluate GIST lesions treated with imatinib [22]. this website As a result, the preclinical development of new drugs or a combination of drugs and molecular targets should be planned with a modern approach based on tumor dimensions and metabolic activity evaluation [23, 24]. We recently developed a xenograft model of GIST measuring tumor metabolism using small animal PET imaging [23]. The aim of this work is to report a preclinical study on the antitumor activity of drug combinations, TKIs and m-TOR inhibitors, in

a xenograft model of GIST in which the drug effects were assessed by small animal PET imaging evaluating both tumor growth control and tumor glucose metabolism. Materials and methods Experimental model Tumor ACP-196 in vitro xenografts were developed with the GIST882 cell line provided by Dr. Jonathan A. Fletcher, Harvard Medical School, Boston, Massachusetts, USA. All data on the GIST882 cell line, cytofluorometric studies and KIT and PDGFRA mutational analysis of GIST882 cells showing a mutation on KIT

receptor exon 13 (homozygous mutation 4SC-202 ic50 – K642E) were reported in our previous article [23]. Rag2-/-;γc-/- breeders were kindly given by Drs. T. Nomura and M. Ito of the Central Institute for Experimental Animals [25]; mice were then bred in our animal facilities under sterile conditions. The experiment was authorized by the institutional review board of the University of Bologna and done according to Italian and European guidelines. Tumor xenografts were induced into Rag2-/-;γc-/- male mice by subcutaneous (s.c.) injection of 107 viable GIST882 cells in 0.2 ml phosphate-buffered saline (PBS) into the right leg. Tumor incidence and growth were evaluated three times a week. Neoplastic masses were measured with calipers; tumor volume was calculated as π. [√(a. b)]3/6, where a = maximal tumor diameter and b = tumor diameter perpendicular to a. Two months after cell injection

mice were sacrificed by CO2 inhalation and necropsied. Treatments protocols Animals were randomized into 6 groups Cyclic nucleotide phosphodiesterase of 6 animals each one for different treatment regimens which were given for 13 days: * No therapy (control) * Imatinib (150 mg/kg b.i.d.) by oral gavage for 6 days, then once/day for another 7 days * Everolimus (10 mg/kg/d.) by oral gavage * Everolimus (10 mg/kg/d.) + imatinib (150 mg/kg b.i.d.) by oral gavage for 6 days, then once/day for another 7 days * Nilotinib (75 mg/kg/d.) by oral gavage * Nilotinib (75 mg/kg/d.) + imatinib (150 mg/kg b.i.d) by oral gavage for 6 days, then once/day for another 7 days Imaging studies Imaging studies were performed using a small animal PET tomograph (GE, eXplore Vista DR) using fluoro-deoxyglucose (FDG) for glucose metabolism. Animals had PET scans after gas anaesthesia (sevofluorane 3-5% and oxygen 1 l/min). FDG was injected into a tail vein.