VDR and tumor of parathyroid gland: They showed that methylation of exon1a of the VDR is significantly higher (65% of CpGs is methylated) than normal breast tissue (15% of CpGs is methylated).48 In contrast, in vitro study in colon cancer cell lines did not show any promoter region methylation of the VDR, and treatment with AZA did not increase gene expression.14 Similarly, decreased VDR expression without any alterations in methylation was reported in parathyroid tumors.23, 49