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Mapping of ER gene CpG island methylation-specific polymerase chain reaction
R G Lapidus1, S J Nass, K A Butash
1Oncology Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
Abstract:
Southern analysis has shown that DNA from 25% of primary estrogen receptor (ER) alpha-negative breast tumors displays aberrant methylation at one site within the ER gene CpG island. To examine more sites and increase sensitivity, we developed a methylation-specific PCR assay to map methylation of the entire ER CpG island. The island was unmethylated in normal breast tissue and ER-positive breast cancer cell lines, but extensively methylated in all ER-negative cell lines and breast tumors examined. In addition, some of the ER-positive/progesterone receptor-negative and ER-positive/progesterone receptor-positive tumors (about 70% and 35%, respectively) displayed methylation of the ER CpG island, suggesting that this heterogeneity within tumor cell populations could potentially shed light on the etiology of ER-negative recurrent tumors arising from ER-positive tumors.