De-regulation of the C-MYC oncogene is among the most frequent molecular abnormalities in human cancer. c-Myc is a bHLH-ZIP transcription factor whose dimerization with another bHLH-ZIP protein, Max, is necessary for transformation and all other biological activities. That c-Myc is indispensable for cell proliferation, that most normal cells are non-cycling and thus non-c-Myc-expressing, and that transient inhibition of c-Myc may be sufficient to achieve permanent tumor regression, makes therapeutic targeting of the oncoprotein highly appealing. We have previously identified 7 low molecular weight compounds that abrogate/prevent bHLH-ZIP-mediated c-Myc-Max heterodimerization ("Myc compounds"). Non structure- guided (i.e. "unbiased") modifications of one of these has resulted in the generation of "2nd generation" analogs with up to 8-fold enhanced potencies, thus demonstrating that significant improvements in compound efficacy can be obtained even in the absence of a model of the compound in association with its target site. In order to identify even better analogs in a more rational and meaningful way, we have demonstrated that 3 of our original Myc compounds bind to distinct sites on the intrinsically disordered c- Myc bHLH-ZIP monomer, alter its secondary structure, and prevent its association with Max. The remaining 4 compounds are redundant and bind to one of these sites. Using NMR spectroscopy, we have generated structural models of the first three compounds in association with synthetic peptides comprising their cognate binding sites. Thus, in Specific Aim 1, we will utilize computational methods and high throughput in silico screens to identify new and more potent "3rd generation" analogs whose structures are rationally predicated on those of the original 3 founding members.
In Specific Aim 2, we will compare the abilities of these new compounds to inhibit c-Myc-Max association and c-Myc-mediated neoplastic growth.
In Specific Aim 3, we will conduct in vivo pharmacologic testing of the most promising analogs prioritized by their "ADMET" profiles. Finally, in Specific Aim 4, selected analogs identified in Specific Aims 2 and 3 will be chemically linked in order to generate "4th generation" compounds capable of simultaneous binding to two distinct sites on the c-Myc bHLH-ZIP domain. This proposal is highly interdisciplinary and interactive in that it utilizes the expertise of a pediatric oncologist/molecular biologist (Prochownik), an organic chemist (Metallo), computational biologists (Behar and Mustata), and pharmacologists (Lazo, Eiseman and Egorin). Together, this diverse, complementary, and synergistic group of investigators, from two institutions, proposes studies that promise new insights regarding the rational design of Myc compounds and the mechanisms by which they disable this critical oncoprotein.

Public Health Relevance

This highly focused application is a multidisciplinary translational effort by seven investigators from two institutions to develop rationally designed small molecules that target the c-Myc oncoprotein. We have already determined the 3D NMR structures of three compounds that bind directly to different sites on the c-Myc monomer and inhibit its activity. Using these as a starting point, we propose to design and characterize a series of more potent analogs, some of which will be chemically linked to provide synergistic binding and biological activities.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Drug Discovery and Molecular Pharmacology Study Section (DMP)
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Misra, Raj N
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University of Pittsburgh
Schools of Medicine
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Fletcher, Steven; Prochownik, Edward V (2015) Small-molecule inhibitors of the Myc oncoprotein. Biochim Biophys Acta 1849:525-43
Chauhan, Jay; Wang, Huabo; Yap, Jeremy L et al. (2014) Discovery of methyl 4'-methyl-5-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)-[1,1'-biphenyl]-3-carboxylate, an improved small-molecule inhibitor of c-Myc-max dimerization. ChemMedChem 9:2274-85
Edmunds, Lia R; Sharma, Lokendra; Kang, Audry et al. (2014) c-Myc programs fatty acid metabolism and dictates acetyl-CoA abundance and fate. J Biol Chem 289:25382-92
Yap, Jeremy L; Wang, Huabo; Hu, Angela et al. (2013) Pharmacophore identification of c-Myc inhibitor 10074-G5. Bioorg Med Chem Lett 23:370-4
Wang, Huabo; Chauhan, Jay; Hu, Angela et al. (2013) Disruption of Myc-Max heterodimerization with improved cell-penetrating analogs of the small molecule 10074-G5. Oncotarget 4:936-47
Sarin, M; Wang, Y; Zhang, F et al. (2013) Alterations in c-Myc phenotypes resulting from dynamin-related protein 1 (Drp1)-mediated mitochondrial fission. Cell Death Dis 4:e670
Elster, Jennifer D; McGuire, Terence F; Lu, Jie et al. (2013) Rapid in vitro derivation of endothelium directly from human cancer cells. PLoS One 8:e77675
Metallo, Steven J (2010) Intrinsically disordered proteins are potential drug targets. Curr Opin Chem Biol 14:481-8
Prochownik, Edward V; Vogt, Peter K (2010) Therapeutic Targeting of Myc. Genes Cancer 1:650-659
Clausen, Dana M; Guo, Jianxia; Parise, Robert A et al. (2010) In vitro cytotoxicity and in vivo efficacy, pharmacokinetics, and metabolism of 10074-G5, a novel small-molecule inhibitor of c-Myc/Max dimerization. J Pharmacol Exp Ther 335:715-27

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