Methylation Status of the CpG Islands in Vitamin D and Calcium-Sensing Receptor Gene Promoters Does Not Explain the Reduced Gene Expressions in Parathyroid Adenomas

Aim: The exact mechanism causing decreased expression of the vitamin D receptor (VDR) and calcium-sensing receptor (CASR) genes in parathyroid adenoma is not known, but methylation of promoter regions is often detected during epigenetic downregulation of gene expression. We investigated whether epigenetic silencing is involved in the decreased expression of VDR and CASR. Experimental Design: Real-time PCR and immunohistochemistry confirmed the downregulation of the VDR and CASR genes at transcriptional and translational levels. Bisulfite-converted DNA samples from parathyroid adenomas with control samples were analyzed for methylation in the promoter region of VDR and CASR genes. Results: There was no significant methylation in the promoter regions of VDR and CASR genes in parathyroid adenomatous tissues. Conclusions: Methylation-mediated silencing of VDR and CASR promoter does not appear to be associated with reduced expression, indicating the involvement of other factors in specific suppression of VDR and CASR in parathyroid adenomas.