Estrogen-ER? signaling and DNA hypomethylation co-regulate expression of stem cell protein PIWIL1 in ER?-positive endometrial cancer cells.

ABSTRACT:

Background

We previously identified PIWIL1 as an oncogene involved in endometrial carcinogenesis. However, the mechanism of Piwil1 mediated regulation of tumorigenesis remains poorly understood.

Methods

The expression levels of target genes in endometrial cancer cells were detected by quantitative reverse transcription-PCR (RT-qPCR) and western blotting. Up- or down-regulation of ER? or PIWIL1 was achieved by transient transfection with expressing plasmids or short hairpin RNA (shRNA). Dual-luciferase reporter assays and chromatin immunoprecipitation (ChIP) were used to demonstrate the ER? bound to the half estrogen response element (half-ERE) located in PIWIL1 promoter. The expression of PIWIL1 and ER? in endometrial carcinoma tissues were investigated using immunohistochemistry and RT-qPCR. The proliferation ability of cancer cells were evaluated by MTT. Methylation status of the PIWIL1 promoter was detected by bisulfite sequencing PCR (BSP).

Results

In the present study, we found that PIWIL1 mediated E₂-stimulated cancer cell proliferation. In ER?-positive endometrial cancer cells, we demonstrated that estrogen-ER? signaling significantly up-regulated the expression of PIWIL1, which was mediated by binding of the ER? onto the PIWIL1 promoter. Furthermore, we found that a half-ERE in the PIWIL1 promoter was essential for ER? binding. The PIWIL1 promoter was hypomethylated in ER?-positive endometrial cancer cells. Treatment with 5-aza-deoxycytidine (5-aza-dC) could up-regulate PIWIL1 expression.

Conclusions

These findings uncover a novel molecular mechanism by which estrogen-ER? signaling and DNA hypomethylation co-regulate PIWIL1 expression. These findings provide novel insights into the hormonal regulation of PIWIL1 in endometrial cancer and the PIWIL1's role in estrogen-stimulated endometrial carcinogenesis. Video Abstract. (MP4 41319 kb).

SUBMITTER: Chen Z 

PROVIDER: S-EPMC7275358 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature