ABSTRACT
<p><b>OBJECTIVE</b>To investigate the correlation between the lack of estrogen receptor (ER) gene expression and hypermethylation of ER gene, and detect whether re-expressed ER protein is activated.</p><p><b>METHODS</b>The methylation status of ER gene promoter in the ER-negative breast cancer cells was evaluated by methylation specific PCR (MSP) and genomic sequencing. The expression of ER and progesterone receptor (PR) mRNA as well as the production of ER protein were detected by RT-PCR and Western blot method, respectively. MTI assay was used to examine the function of re-expressed ER protein.</p><p><b>RESULTS</b>The ER gene promoter was highly methylated, while ER mRNA and ER protein were not expressed in the ER-negative breast cell line MDA-MB-231. The ER-negative breast cells treated with demethylating agent 5 -aza-2'-deoxycytidine (5-AZA-2'-deoxyC) restored the expression of ER mRNA and ER protein. Expression of the endogenous ER-responsive PR gene was activated and the methylation of ER gene was simultaneously decreased. After MDA-MB-231 was treated with 5-AZA-2'-deoxyC, the protein of ER was re-expressed and the growth of cells treated with tamoxifen were inhibited significantly (P < 0.05).</p><p><b>CONCLUSION</b>inactivation of ER gene has a close relationship with the abnormal methylation of ER gene promoter. 5-AZA-2'-deoxyC may effectively cause demethylation and restore functional expression of ER silenced by aberrant hypermethylation. The result may offer a new measure and theory for breast cancer patients with ER-negative expression to receive endocrine therapies.</p>
Subject(s)
Female , Humans , Antimetabolites, Antineoplastic , Pharmacology , Antineoplastic Agents, Hormonal , Pharmacology , Azacitidine , Pharmacology , Base Sequence , Blotting, Western , Breast Neoplasms , Genetics , Metabolism , Pathology , Cell Line, Tumor , Cell Proliferation , DNA Methylation , Estrogen Receptor alpha , Genetics , Gene Expression Regulation, Neoplastic , Genetics , Promoter Regions, Genetic , Genetics , RNA, Messenger , Genetics , Receptors, Progesterone , Genetics , Reverse Transcriptase Polymerase Chain Reaction , Selective Estrogen Receptor Modulators , Pharmacology , Tamoxifen , PharmacologyABSTRACT
<p><b>OBJECTIVE</b>Nan'ao County in Guandong Province is a high-risk area of esophageal cancer in Southern China. Of the suspected etiological factors in the environment, N-nitrosamines and their precursors have received the greatest attention.</p><p><b>METHODS</b>Sixty samples of the diet ingested by the inhabitants were collected and detected for volatile N-nitrosamines and their precursors. Five N-nitrosamines detected by Gas Chromatography-Thermal Energy Analyzer were N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine, N-nitrosopiperidine and N-nitrosomethyl-benzylamine.</p><p><b>RESULTS</b>The average content of 5 volatile N-nitrosamines in the diet was 312.0 micrograms/kg (median). The daily intake of the nitrosamines was 286.5 micrograms/head/day. Only the ability to exogenously synthesize N-nitrosopiperidine was powerful among 5 volatile N-nitrosamines. By a computerized stepwise regression analysis and curve fitting, we studied the correlation among the nitrosamines, the precursors and the major food items in the samples.</p><p><b>CONCLUSION</b>It demonstrated that a relatively high content of volatile N-nitrosamines was present in the diet collected in the area.</p>