In vivo gene expression changes in EW5 Ewing sarcoma xenografts after IGF-1R or mTOR blockade. Homo sapiens

Ewing Sarcoma is caused by a pathognomonic genomic translocation that places an N-terminal EWSR1 gene in approximation with one of several ETS genes (typically FLI1). This aberration, in turn, alters the transcriptional regulation of more than five hundred genes and perturbs a number of critical pathways that promote oncogenesis, cell growth, invasion, and metastasis. Among them, translocation-mediated up-regulation of the insulin-like growth factor receptor 1 (IGF-1R) and mammalian target of rapamycin (mTOR) are of particular importance since they work in concert to facilitate IGF-1R expression and ligand-induced activation, respectively, of proven importance in ES transformation. When used as a single agent in Ewing sarcoma therapy, IGF-1R or mTOR inhibition leads to rapid counter-regulatory effects that blunt the intended therapeutic purpose. Therefore, identify new mechanisms of resistance that are used by Ewing sarcoma to evade cell death to single-agent IGF-1R or mTOR inhibition might suggest a number of therapeutic combinations that could improve their clinical activity. Overall design: Male non-obese diabetic (NOD)-SCID-IL-2Rgnull mice were used to generate EW5 explants (2 mm). Mice bearing subcutaneous tumors were randomized into treatment and control groups when their tumors reached a diameter of 6 mm and received MK-8669 (mTOR inhibitor, 5mg/kg per dose, once weekly), MK-0646 (IGF-1R inhibitor monoclonal antibody, 0.5mg IP twice weekly), or a placebo control (sterile buffer). Animals were treated either until their tumors reached 1500 mm3 in volume. Affymetrix Geneship profiling of EW5 xenografts treated in vivo either with MK-0646, MK-8669, and control and compared each other using extracted RNA and hybridized on Affymetrix microrrays ( Affymetrix Human Genome U133A 2.0 cartridge arrays).