EFFECT OF ZEB1 OVEREXPRESSION AND SILENCING ON AN ER-Α PROMOTER OF METHYLATION OF BREAST CANCER CELLS AND THE MECHANISM OF ITS TRANSCRIPTIONAL INHIBITION

Yongfeng Li^{1, 2, #}, Xinmiao Rui^{3, #}, Daobao Chen^{1, 2}, Dehong Zou^{1, 2}, Xuli Meng^{4, *} 

¹Department of Breast Surgery, Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital), Hangzhou 310022, PR China - ²Institute of Cancer and Basic Medicine (IBMC), Chinese Academy of Sciences, Hangzhou 310022, PR China - ³2nd Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou 310022, PR China - ⁴Department of Breast Surgery, Zhejiang province people’s hospital, Hangzhou 310022, PR China

Objective: To investigate the effect of zinc finger E-box binding homeobox 1 (ZEB1) overexpression and silencing on the estrogen receptor-α (ER-α) promoter methylation of breast cancer cells and the mechanism of its transcription inhibition.

Methods: MDA-MB-231 cell lines were randomly divided into a Ctrl group, an AZA group, a VPA group and an AZA+VPA group. MCF-7 cell lines were selected and randomly divided into a Ctrl group, ZEB1 group, AZA group, VPA group, and AZA+VPA group. The mRNA and protein expression levels of ZEB1 and ER-α in breast cancer cell lines were compared. The expression of DNMT3B and HDAC1 in each group was compared. 

Results: The expression levels of ZEB1 decreased and the expression levels of ER-α increased. The expression levels of mRNA and ZEB1 proteins in the cells were significantly lower, but the expression levels of ER-α mRNA and proteins in the cells were significantly higher in the h-ZEB1-MDA-MAB-231 group than those in the SC-MDA-MAB-231 group (P<0.05). Moreover, ZEB1 could simultaneously precipitate DNMT3B and HDAC1 proteins, and DNMT3B and HDAC1 antibodies could also correspondingly precipitate ZEB1 protein expression, suggesting that the combination of ZEB1, DNMT3B, and HDAC1 can produce a protein complex. DNMT3B and HDAC1 can also be enriched in the sequence region of E2box elements. 

Conclusions: ZEB1 can induce the hypermethylation of an ER-α promoter in breast cancer cells and its mechanism may be achieved by recruiting DNMT3B and HDAC1 to the ER-α promoter region.