miR10a Mediate Tamoxifen Resistance in ER-Positive Breast Cancer Cells Through Down-Regulation of RFPL-3/hTERT

Tamoxifen (TAM) is used as a first-line endocrine treatment for estrogen receptor (ER)-positive breast cancers. However, some patients develop TAM resistance after treatment and the role of miRNAs in TAM resistance still unknown. qPCR assay was performed to assess the expression levels of miR10a and RFPL-3 /hTERT. Western blot analysis was used to determine RFPL-3 /hTERT levels. The direct correlation between miR10a and RFPL-3 was verified by dual-luciferase reporter assay. CCK-8 assay and PicoGreen dsDNA quantification assay were applied to determine cell proliferation ability. In this study, we found that miR10a is downregulated in breast cancer with TAM resistance and that low expression of miR10a is associated with poor prognosis. By studying the regulatory mechanism, we found that miR10a functions as a negative regulator of RFPL-3 mRNA by binding the 3’-UTR region and disrupting the interaction between RFPL-3 and hTERT, which inhibits the proliferation of ER-positive breast cancer cells with TAM resistance. Collectively, our study findings indicate that the downregulation of miR10a activates RFPL-3/hTERT and induces tamoxifen resistance in ER-positive breast cancer cells.