Epigenetic silencing of the 3p22 tumor suppressor DLEC1 by promoter CpG methylation in non-Hodgkin and Hodgkin lymphomas
- Equal contributors
1 Shenzhen Institutes of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS)-CUHK, Shenzhen, China
2 Cancer Epigenetics Laboratory, Department of Clinical Oncology, State Key Laboratory of Oncology in South China, Sir YK Pao Center for Cancer, The Chinese University of Hong Kong and CUHK Shenzhen Research Institute, Shatin, Hong Kong
3 Department of Pathology, Peking University Health Science Center, Beijing, China
4 Department of Pathology, University of Hong Kong, Shatin, Hong Kong
5 Cancer Research UK Institute for Cancer Studies, University of Birmingham, Birmingham, UK
6 Johns Hopkins Singapore and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, MD, USA
Journal of Translational Medicine 2012, 10:209 doi:10.1186/1479-5876-10-209Published: 11 October 2012
Inactivaion of tumor suppressor genes (TSGs) by promoter CpG methylation frequently occurs in tumorigenesis, even in the early stages, contributing to the initiation and progression of human cancers. Deleted in lung and esophageal cancer 1 (DLEC1), located at the 3p22-21.3 TSG cluster, has been identified frequently silenced by promoter CpG methylation in multiple carcinomas, however, no study has been performed for lymphomas yet.
We examined the expression of DLEC1 by semi-quantitative reverse transcription (RT)-PCR, and evaluated the promoter methylation of DLEC1 by methylation-specific PCR (MSP) and bisulfite genomic sequencing (BGS) in common lymphoma cell lines and tumors.
Here we report that DLEC1 is readily expressed in normal lymphoid tissues including lymph nodes and PBMCs, but reduced or silenced in 70% (16/23) of non-Hodgkin and Hodgkin lymphoma cell lines, including 2/6 diffuse large B-cell (DLBCL), 1/2 peripheral T cell lymphomas, 5/5 Burkitt, 6/7 Hodgkin and 2/3 nasal killer (NK)/T-cell lymphoma cell lines. Promoter CpG methylation was frequently detected in 80% (20/25) of lymphoma cell lines and correlated with DLEC1 downregulation/silencing. Pharmacologic demethylation reversed DLEC1 expression in lymphoma cell lines along with concomitant promoter demethylation. DLEC1 methylation was also frequently detected in 32 out of 58 (55%) different types of lymphoma tissues, but not in normal lymph nodes. Furthermore, DLEC1 was specifically methylated in the sera of 3/13 (23%) Hodgkin lymphoma patients.
Thus, methylation-mediated silencing of DLEC1 plays an important role in multiple lymphomagenesis, and may serve as a non-invasive tumor marker for lymphoma diagnosis.