Stegmaier, KimberlyWong, Jenny SRoss, Kenneth NChow, Kwan TPeck, DavidWright, Renee DLessnick, Stephen LKung, AndrewGolub, Todd2011-05-022007Stegmaier, Kimberly, Jenny S. Wong, Kenneth N. Ross, Kwan T. Chow, David Peck, Renee D. Wright, Stephen L. Lessnick, Andrew L. Kung, and Todd R. Golub. 2007. Signature-based small molecule screening identifies cytosine arabinoside as an EWS/FLI modulator in ewing sarcoma. PLoS Medicine 4(4): e122.1549-1277http://nrs.harvard.edu/urn-3:HUL.InstRepos:4879997Background: The presence of tumor-specific mutations in the cancer genome represents a potential opportunity for pharmacologic intervention to therapeutic benefit. Unfortunately, many classes of oncoproteins (e.g., transcription factors) are not amenable to conventional small-molecule screening. Despite the identification of tumor-specific somatic mutations, most cancer therapy still utilizes nonspecific, cytotoxic drugs. One illustrative example is the treatment of Ewing sarcoma. Although the EWS/FLI oncoprotein, present in the vast majority of Ewing tumors, was characterized over ten years ago, it has never been exploited as a target of therapy. Previously, this target has been intractable to modulation with traditional small-molecule library screening approaches. Here we describe a gene expression–based approach to identify compounds that induce a signature of EWS/FLI attenuation. We hypothesize that screening small-molecule libraries highly enriched for FDA-approved drugs will provide a more rapid path to clinical application. Methods and Findings: A gene expression signature for the EWS/FLI off state was determined with microarray expression profiling of Ewing sarcoma cell lines with EWS/FLI-directed RNA interference. A small-molecule library enriched for FDA-approved drugs was screened with a high-throughput, ligation-mediated amplification assay with a fluorescent, bead-based detection. Screening identified cytosine arabinoside (ARA-C) as a modulator of EWS/FLI. ARA-C reduced EWS/FLI protein abundance and accordingly diminished cell viability and transformation and abrogated tumor growth in a xenograft model. Given the poor outcomes of many patients with Ewing sarcoma and the well-established ARA-C safety profile, clinical trials testing ARA-C are warranted. Conclusions: We demonstrate that a gene expression–based approach to small-molecule library screening can identify, for rapid clinical testing, candidate drugs that modulate previously intractable targets. Furthermore, this is a generic approach that can, in principle, be applied to the identification of modulators of any tumor-associated oncoprotein in the rare pediatric malignancies, but also in the more common adult cancers.en-USbiochemistrygenetics and genomicsoncologypediatrics and child healthgeneticsdrugs and adverse drug reactionspharamcology and toxicologychemotherapyJournal Article2011-05-0210.1371/journal.pmed.0040122