Molecular Genetic and Epigenetic analysis of NCX2/SLC8A2 at 19q13.3 in Human Gliomas

Aim Loss of heterozygosity (LOH) at 19q13.3 is a common genetic change in human gliomas, indicating yet unknown glial-specific tumour suppressor genes in this chromosome region. NCX2/SLC8A2 located on chromosome 19q13.32 encodes a Na(+)/Ca(2+)exchanger, which contributes to intracellular Ca(2+)homeostasis. Its expression is restricted to brain, and it is neither present in other normal tissues nor in gliomas at any significant level. The aim of this study was to investigate if NCX2 might be a tumour suppressor gene involved in glioma. Methods We performed a systematic analysis of NCX2 in 42 human gliomas using microsatellite analysis for evaluation of LOH at 19q, DNA sequencing and DNA methylation analysis. Results Except for three known intragenic SNPs, rs12459087, rs7259674, and rs8104926, no NCX2 sequence variations were detected in any of the tumour samples. Furthermore, a CpG island in the 5' promoter region of NCX2 was unmethylated. Interestingly, the CpG sites of three gene-body CpG islands located in exon 2, intron 2-3 and exon 3 and of a 5' CpG rich area relevant to so called CpG island shore of NCX2 were methylated in all 8 glioma samples and in 3 established glioma cell lines tested. Surprisingly, NCX2 could be activated by addition of the DNA methylation inhibitor 5-aza-2'-deoxycytidine to glioma cell lines in which NCX2 was completely silent. Conclusion Results indicate that DNA methylation may play a key role in the transcriptional silencing of NCX2.