A High Degree of LINE-1 Hypomethylation Is a Unique Feature of Early-Onset Colorectal Cancer Marina Antelo 1 , Francesc Balaguer 2,3 *, Jinru Shia 4 , Yan Shen 2 , Keun Hur 2 , Leticia Moreira 3 , Miriam Cuatrecasas 3 , Luis Bujanda 5 , Maria Dolores Giraldez 3 , Masanobu Takahashi 2 , Ana Cabanne 1 , Mario Edmundo Barugel 1 , Mildred Arnold 2 , Enrique Luis Roca 1 , Montserrat Andreu 6 , Sergi Castellvi- Bel 3 , Xavier Llor 7 , Rodrigo Jover 8 , Antoni Castells 3 , C. Richard Boland 2 , Ajay Goel 2 * 1 Oncology and Pathology Sections, Hospital of Gastroenterology ‘‘Dr. C. B. Udaondo’’, Buenos Aires, Argentina, 2 Department of Internal Medicine, Division of Gastroenterology, Charles A. Sammons Cancer Center and Baylor Research Institute, Baylor University Medical Center, Dallas, Texas, United States of America, 3 Department of Gastroenterology, Hospital Clı ´nic, Centro de Investigacio ´ n Biome ´dica en Red de Enfermedades Hepa ´ticas y Digestivas (CIBERehd), Institut d’Investigacions Biomediques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain, 4 Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America, 5 Department of Gastroenterology, CIBERehd, University of Country Basque, Donostia Hospital, San Sebastia ´n, Spain, 6 Deparment of Gastroenterology, Hospital del Mar, Barcelona, Spain, 7 Department of Medicine and Cancer Center, University of Illinois at Chicago, Chicago, Illinois, United States of America, 8 Gastroenterology Unit, Hospital General Universitario, Alicante, Spain Abstract Objective: Early-onset colorectal cancer (CRC) represents a clinically distinct form of CRC that is often associated with a poor prognosis. Methylation levels of genomic repeats such as LINE-1 elements have been recognized as independent factors for increased cancer-related mortality. The methylation status of LINE-1 elements in early-onset CRC has not been analyzed previously. Design: We analyzed 343 CRC tissues and 32 normal colonic mucosa samples, including 2 independent cohorts of CRC diagnosed #50 years old (n = 188), a group of sporadic CRC .50 years (MSS n = 89; MSI n = 46), and a group of Lynch syndrome CRCs (n = 20). Tumor mismatch repair protein expression, microsatellite instability status, LINE-1 and MLH1 methylation, somatic BRAF V600E mutation, and germline MUTYH mutations were evaluated. Results: Mean LINE-1 methylation levels (6SD) in the five study groups were early-onset CRC, 56.6% (8.6); sporadic MSI, 67.1% (5.5); sporadic MSS, 65.1% (6.3); Lynch syndrome, 66.3% (4.5) and normal mucosa, 76.5% (1.5). Early-onset CRC had significantly lower LINE-1 methylation than any other group (p,0.0001). Compared to patients with ,65% LINE-1 methylation in tumors, those with $65% LINE-1 methylation had significantly better overall survival (p = 0.026, log rank test). Conclusions: LINE-1 hypomethylation constitutes a potentially important feature of early-onset CRC, and suggests a distinct molecular subtype. Further studies are needed to assess the potential of LINE-1 methylation status as a prognostic biomarker for young people with CRC. Citation: Antelo M, Balaguer F, Shia J, Shen Y, Hur K, et al. (2012) A High Degree of LINE-1 Hypomethylation Is a Unique Feature of Early-Onset Colorectal Cancer. PLoS ONE 7(9): e45357. doi:10.1371/journal.pone.0045357 Editor: Anthony W.I. Lo, The Chinese University of Hong Kong, Hong Kong Received July 2, 2012; Accepted August 15, 2012; Published September 25, 2012 Copyright: ß 2012 Antelo et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The present work was supported by grants R01 CA72851 and CA129286 from the National Cancer Institute, National Institutes of Health; and funds from the Baylor Research Institute to CRB and AG. FB was supported by a grant from Fundacio ´ n Alfonso Martı ´n Escudero and from Instituto de Salud Carlos III (PI10/00384). MA was supported by a ‘‘Type I Postgraduate Scholarship’’ given by the CONICET (National Council of Scientific and Technical Investigations) dependent on the Argentine Ministry of Science and Technology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: ajay.goel@baylorhealth.edu (AG); fprunes@clinic.ub.es (FB) Introduction Colorectal cancer (CRC) is an important public health problem and represents the second most frequent cancer and the second greatest cause cancer-related mortality in most of the developed world. Each year, one million people develop CRC, and 40–50% of them will die within 5 years of diagnosis [1]. CRCs are highly heterogeneous both histopathologically, and at the molecular and genetic level. It appears that the biology and response to therapies is equally diverse. Understanding the molecular mechanisms of colorectal carcinogenesis is essential for the development of new strategies for prevention, diagnosis, treatment and prognosis. Although CRC has been a major focus of attention for basic and clinical research during the last 25 years, we still lack robust biomarkers that can be used for diagnosis and treatment of CRC. The peak incidence of CRC is between 60–70 years old; however up to 10% of all cases occur before age 50. Moreover, recent epidemiological studies suggest that the incidence of early- onset CRC is increasing, representing an important clinical challenge [2]. Early-onset CRC often presents with advanced PLOS ONE | www.plosone.org 1 September 2012 | Volume 7 | Issue 9 | e45357