THOR is a targetable epigenetic biomarker with clinical implications in breast cancer

Clinical Epigenetics

Research

Mónica Teotónio Fernandes¹  Ana-Teresa Maia²  Pedro Castelo-Branco³  Joana Dias Apolónio⁴  Luis Vicioso⁵  Ricardo Leão⁶  Nuno Miguel Nunes⁷  Donghyun Lee⁷  Cindy H. Zhang⁷  Tatiana Lipman⁷  Martin Komosa⁷  Uri Tabori⁸  João S. Dias⁹  José L. Morera⁹ 

[1] Algarve Biomedical Center Research Institute (ABC-RI), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Algarve Biomedical Center (ABC), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Escola Superior de Saúde (ESSUAlg), Universidade Do Algarve, Faro, Portugal;Faculty of Medicine and Biomedical Sciences (FMCB), University of Algarve, Gambelas Campus, Bld. 2, 8005-139, Faro, Portugal;Algarve Biomedical Center (ABC), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Center for Research in Health Technologies and Information Systems (CINTESIS@RISE), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Faculty of Medicine and Biomedical Sciences (FMCB), University of Algarve, Gambelas Campus, Bld. 2, 8005-139, Faro, Portugal;Algarve Biomedical Center Research Institute (ABC-RI), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Algarve Biomedical Center (ABC), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Champalimaud Research Program, Champalimaud Centre for the Unknown, Lisbon, Portugal;Faculty of Medicine and Biomedical Sciences (FMCB), University of Algarve, Gambelas Campus, Bld. 2, 8005-139, Faro, Portugal;Algarve Biomedical Center Research Institute (ABC-RI), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Algarve Biomedical Center (ABC), University of Algarve, Gambelas Campus, 8005-139, Faro, Portugal;Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada;Faculty of Medicine, Department of Histology and Pathological Anatomy, University of Malaga, Malaga, Spain;Faculty of Medicine, University of Coimbra, Coimbra, Portugal;Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada;Arthur and Sonia Labatt Brain Tumor Research Center, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada;Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada;Arthur and Sonia Labatt Brain Tumor Research Center, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada;Division of Hematology/Oncology, The Hospital for Sick Children, Toronto, ON, Canada;University Hospital Center of Algarve, Faro, Portugal;

关键词: Breast cancer;    TERT;    THOR;    DNA methylation;    Biomarkers;    CRISPR-dCas9;   

DOI  :  10.1186/s13148-022-01396-3

 received in 2022-04-23, accepted in 2022-12-02,  发布年份 2022

来源: Springer

【 摘 要 】

BackgroundBreast cancer (BC) is the most frequently diagnosed cancer and a leading cause of death among women worldwide. Early BC is potentially curable, but the mortality rates still observed among BC patients demonstrate the urgent need of novel and more effective diagnostic and therapeutic options. Limitless self-renewal is a hallmark of cancer, governed by telomere maintenance. In around 95% of BC cases, this process is achieved by telomerase reactivation through upregulation of the human telomerase reverse transcriptase (hTERT). The hypermethylation of a specific region within the hTERT promoter, termed TERT hypermethylated oncological region (THOR) has been associated with increased hTERT expression in cancer. However, its biological role and clinical potential in BC have never been studied to the best of our knowledge. Therefore, we aimed to investigate the role of THOR as a biomarker and explore the functional impact of THOR methylation status in hTERT upregulation in BC.ResultsTHOR methylation status in BC was assessed by pyrosequencing on discovery and validation cohorts. We found that THOR is significantly hypermethylated in malignant breast tissue when compared to benign tissue (40.23% vs. 12.81%, P < 0.0001), differentiating malignant tumor from normal tissue from the earliest stage of disease. Using a reporter assay, the addition of unmethylated THOR significantly reduced luciferase activity by an average 1.8-fold when compared to the hTERT core promoter alone (P < 0.01). To further investigate its biological impact on hTERT transcription, targeted THOR demethylation was performed using novel technology based on CRISPR-dCas9 system and significant THOR demethylation was achieved. Cells previously demethylated on THOR region did not develop a histologic cancer phenotype in in vivo assays. Additional studies are required to validate these observations and to unravel the causality between THOR hypermethylation and hTERT upregulation in BC.ConclusionsTHOR hypermethylation is an important epigenetic mark in breast tumorigenesis, representing a promising biomarker and therapeutic target in BC. We revealed that THOR acts as a repressive regulatory element of hTERT and that its hypermethylation is a relevant mechanism for hTERT upregulation in BC.

【 授权许可】

CC BY   
© The Author(s) 2022

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