Transcriptional reactivation of telomerase catalytic subunit (TERT) is a frequent hallmark of cancer, occurring in 90% of human malignancies. However, specific mechanisms driving TERT reactivation remain obscure for many tumor types and in particular gastric cancer (GC), a leading cause of global cancer mortality. Here, through comprehensive genomic and epigenomic analysis of primary GCs and GC cell lines, we identified the transcription factor early B cell factor 1 (EBF1) as a TERT transcriptional repressor and inactivation of EBF1 function as a major cause of TERT upregulation. Abolishment of EBF1 function occurs through 3 distinct (epi)genomic mechanisms. First, EBF1 is epigenetically silenced via DNA methyltransferase, polycomb-repressive complex 2 (PRC2), and histone deacetylase activity in GCs. Second, recurrent, somatic, and heterozygous EBF1 DNA–binding domain mutations result in the production of dominant-negative EBF1 isoforms. Third, more rarely, genomic deletions and rearrangements proximal to the TERT promoter remobilize or abolish EBF1-binding sites, derepressing TERT and leading to high TERT expression. EBF1 is also functionally required for various malignant phenotypes in vitro and in vivo, highlighting its importance for GC development. These results indicate that multimodal genomic and epigenomic alterations underpin TERT reactivation in GC, converging on transcriptional repressors such as EBF1.
Manjie Xing, Wen Fong Ooi, Jing Tan, Aditi Qamra, Po-Hsien Lee, Zhimei Li, Chang Xu, Nisha Padmanabhan, Jing Quan Lim, Yu Amanda Guo, Xiaosai Yao, Mandoli Amit, Ley Moy Ng, Taotao Sheng, Jing Wang, Kie Kyon Huang, Chukwuemeka George Anene-Nzelu, Shamaine Wei Ting Ho, Mohana Ray, Lijia Ma, Gregorio Fazzi, Kevin Junliang Lim, Giovani Claresta Wijaya, Shenli Zhang, Tannistha Nandi, Tingdong Yan, Mei Mei Chang, Kakoli Das, Zul Fazreen Adam Isa, Jeanie Wu, Polly Suk Yean Poon, Yue Ning Lam, Joyce Suling Lin, Su Ting Tay, Ming Hui Lee, Angie Lay Keng Tan, Xuewen Ong, Kevin White, Steven George Rozen, Michael Beer, Roger Sik Yin Foo, Heike Irmgard Grabsch, Anders Jacobsen Skanderup, Shang Li, Bin Tean Teh, Patrick Tan