1. ¹Department of Neuropathology, University of Bonn, Germany
2. ²Montreal Children's Hospital Research Institute, McGill University, Montreal, Canada
3. ³Department of Pediatric Neurosurgery, University of Würzburg, Germany
4. ⁴Department of Biochemistry and Molecular Biology, Louisiana State University, Medical Center, New Orleans, LA, USA
5. ⁵German Cancer Research Center (DKFZ), Heidelberg, Germany

Correspondence: Dr A Waha, Department of Neuropathology, University of Bonn Medical Center, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany. E-mail:awaha1@uni-bonn.de

Received 11 September 2006; Revised 15 January 2007; Accepted 17 January 2007; Published online 5 March 2007.

Abstract

In a genome-wide screen using differential methylation hybridization (DMH), we have identified a CpG island within the 5' region and untranslated first exon of the secretory granule neuroendocrine protein 1 gene (SGNE1/7B2) that showed hypermethylation in medulloblastomas compared to fetal cerebellum. Bisulfite sequencing and combined bisulfite restriction assay were performed to confirm the methylation status of this CpG island in primary medulloblastomas and medulloblastoma cell lines. Hypermethylation was detected in 16/23 (70%) biopsies and 7/8 (87%) medulloblastoma cell lines, but not in non-neoplastic fetal (n=8) cerebellum. Expression of SGNE1 was investigated by semi-quantitative competitive reverse transcription–polymerase chain reaction and found to be significantly downregulated or absent in all, but one primary medulloblastomas and all cell lines compared to fetal cerebellum. After treatment of medulloblastoma cell lines with 5-aza-2'-deoxycytidine, transcription of SGNE1 was restored. No mutation was found in the coding region of SGNE1 by single-strand conformation polymorphism analysis. Reintroduction of SGNE1 into the medulloblastoma cell line D283Med led to a significant growth suppression and reduced colony formation. In summary, we have identified SGNE1 as a novel epigenetically silenced gene in medulloblastomas. Its frequent inactivation, as well as its inhibitory effect on tumor cell proliferation and focus formation strongly argues for a significant role in medulloblastoma development.