CpG island methylation status and mutation analysis of the RBI gene essential promoter region and protein-binding pocket domain in nervous system tumours

A series of 136 nervous system tumours were studied to determine the methylation status of the CpG island contained within the promoter region of the RBI gene, as well as mutation analysis of the essential promoter region and exons 20-24 (and surrounding intronic regions) coding for the protein-binding pocket domain. Methylation of the RBI CpG island was detected in 26 samples corresponding to nine glioblastomas, three anaplastic astrocytomas, one mixed oligo-astrocytoma, one ependymoma, two medulloblastomas, two primary central nervous system lymphomas, two neurofibrosarcomas, and six brain metastasis from solid tumours. No inactivating mutations were found within the RBI promoter region, whereas one glioblastoma and one oligodendroglioma displayed similar sequence variations consisting of 12 and 8 base pair deletions at intron 21. These results suggest that RBI CpG island hypermethylation is a common epigenetic event that is associated with the development of malignant nervous system tumours. (C) 2003 Cancer Research UK.