[Demethylation of estrogen receptor gene and its re-expression in estrogen receptor-negative breast].
OBJECTIVE
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Wang
Rui
R
Cancer Center, Department of Oncology, First Affiliated Hospital, Zhengzhou University, Zhengzhou 450052, China.
Li
Lin-Wei
LW
Wang
Rui-Lin
RL
Fan
Qing-Xia
QX
Zhao
Pei-Rong
PR
Wang
Liu-Xing
LX
Lu
Shih-Hsin
SH
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation; D000077209:Decitabine; D047628:Estrogen Receptor alpha / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011980:Receptors, Progesterone / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology; D013629:Tamoxifen / Q000494:pharmacology
D000964:Antimetabolites, Antineoplastic; D018931:Antineoplastic Agents, Hormonal; D047628:Estrogen Receptor alpha; D012333:RNA, Messenger; D011980:Receptors, Progesterone; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; D000077209:Decitabine; D001374:Azacitidine