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Enhancer profiling identifies critical cancer genes and characterizes cell identity in adult T-cell leukemia. (Blood, Oct 2017)

Wong RWJ1, Ngoc PCT1, Leong WZ1, Yam AWY1, Zhang T2, Asamitsu K3, Iida S4, Okamoto T3, Ueda R5, Gray NS6, Ishida T4, Sanda T7.

Author information
1 Cancer Science Institute of Singapore, National University of Singapore, Singapore.
2 Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, United States.
3 Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
4 Department of Hematology and Oncology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
5 Department of Tumor Immunology, Aichi Medical University School of Medicine, Aichi, Japan.
6 Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, United States.
7 Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore takaomi_sanda@nus.edu.sg.

Abstract
A number of studies have recently demonstrated that “super-enhancers”, which are large cluster of enhancers typically marked by a high level of acetylation of histone H3 lysine 27 and mediator bindings, are frequently associated with genes that control and define cell identity during normal development. Super-enhancers are also often enriched at cancer genes in various malignancies. Identification of such enhancers would pinpoint critical factors that directly contribute to pathogenesis. Here, we performed enhancer profiling using primary leukemia samples from adult T-cell leukemia/lymphoma (ATL), which is a genetically heterogeneous intractable cancer. Super-enhancers were enriched at genes involved in the T-cell activation pathway including IL2RA/CD25, CD30 and FYN, in both ATL and normal mature T-cells, which reflected the origin of the leukemic cells. Super-enhancers were found at several known cancer gene loci, including CCR4, PIK3R1 and TP73, in multiple ATL samples but not in normal mature T-cells, which implicated those genes in ATL pathogenesis. A small-molecule CDK7 inhibitor THZ1 efficiently inhibited cell growth, induced apoptosis and downregulated the expression of super-enhancer-associated genes in ATL cells. Furthermore, enhancer profiling combined with gene expression analysis identified a previously uncharacterized gene, TIAM2 that was associated with super-enhancers in all ATL samples but not in normal T-cells. Knockdown of TIAM2 induced apoptosis in ATL cell lines, whereas overexpression of this gene promoted cell growth. Our study provides a novel strategy for identifying critical cancer genes.

PMID: 28978570