Research ArticleCancer

Structure-based design of small-molecule inhibitors of EBNA1 DNA binding blocks Epstein-Barr virus latent infection and tumor growth

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Science Translational Medicine  06 Mar 2019:
Vol. 11, Issue 482, eaau5612
DOI: 10.1126/scitranslmed.aau5612

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No holds Barr-ed for cancer treatment

Persistent latent infection with Epstein-Barr virus contributes to tumorigenesis in a variety of cancer types. The only viral protein that is consistently expressed in these tumors is Epstein-Barr nuclear antigen 1, which performs a variety of biological functions. To target this antigen, Messick et al. designed a series of chemical inhibitors and then tested them in vitro and in multiple mouse models of Epstein-Barr virus–associated cancer. The authors characterized the inhibitors using a variety of assays, examined the mechanism by which they work, and demonstrated preclinical effectiveness and suitable pharmacological properties, paving the way for further therapeutic development.

Abstract

Epstein-Barr virus (EBV) is a DNA tumor virus responsible for 1 to 2% of human cancers including subtypes of Burkitt’s lymphoma, Hodgkin’s lymphoma, gastric carcinoma, and nasopharyngeal carcinoma (NPC). Persistent latent infection drives EBV-associated tumorigenesis. Epstein-Barr nuclear antigen 1 (EBNA1) is the only viral protein consistently expressed in all EBV-associated tumors and is therefore an attractive target for therapeutic intervention. It is a multifunctional DNA binding protein critical for viral replication, genome maintenance, viral gene expression, and host cell survival. Using a fragment-based approach and x-ray crystallography, we identify a 2,3-disubstituted benzoic acid series that selectively inhibits the DNA binding activity of EBNA1. We characterize these inhibitors biochemically and in cell-based assays, including chromatin immunoprecipitation and DNA replication assays. In addition, we demonstrate the potency of EBNA1 inhibitors to suppress tumor growth in several EBV-dependent xenograft models, including patient-derived xenografts for NPC. These inhibitors selectively block EBV gene transcription and alter the cellular transforming growth factor–β (TGF-β) signaling pathway in NPC tumor xenografts. These EBNA1-specific inhibitors show favorable pharmacological properties and have the potential to be further developed for the treatment of EBV-associated malignancies.

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