YY1 as a promoter regulating the circ_0001946/miR-671-5p/EGFR axis to promote chemotherapy resistance in breast cancer cells

Objective: To investigate the mechanism of circ_0001946 activated by transcription factor Yin Yang 1 (YY1), targeting miR-671-5p to regulate epidermal growth factor receptor (EGFR) and thereby participating in the chemotherapy resistance of breast Cancer (BC) cells.

Methods: Circ_0001946, which is differentially expressed in BC, was screened using gene expression omnibus. Dual luciferase assay and RNA immunoprecipitation were conducted to verify the relationship among circ_0001946/miR-671-5p/EGFR. A ChIP test confirmed that YY1 can be used as a transcription factor of circ_0001946 to specifically bind to its promoter. The expression of circ_0001946/miR-671-5p/EGFR regulatory axis in BC tissues and cell lines were evaluated using qRT-PCR. As for in vitro experiments, tamoxifen was used to establish a drug-resistant BC cell model. The effects of the regulatory axis on the proliferation, invasion and Apoptosis of BC cells were studied using CCK-8, Transwell invasion assay and Annexin V-FITC/PI staining, so as to evaluate its effect on the sensitivity of BC cells to tamoxifen.

Results: Circ_0001946 showed an abnormally high expression in BC tissues and tamoxifen resistant cells and was up-regulated in an IC₅₀-dependent manner (both P<0.05). Circ_0001946 was activated by YY1 in drug-resistant BC cells. Knockdown of circ_0001946 significantly inhibited the proliferation, invasion and promoted Apoptosis of drug-resistant BC cells (all P<0.05). Overexpression of circ_0001946 promoted the proliferation and invasion of drug-resistant BC cells and hindered their Apoptosis, which could be partially reversed by miR-671-5p mimics (all P<0.05). EGFR has been proven to be a downstream target gene of miR-671-5p. A knockdown of EGFR improved the malignant biological behavior of drug-resistant BC cells, which could be partially eliminated by overexpression of circ_0001946 (all P<0.05).

Conclusion: Circ_0001946 absorbs miR-671-5p to target EGFR to promote the growth and malignant invasion of drug-resistant BC cells, thereby increasing the resistance to tamoxifen. This effect of circ_0001946 may be achieved by transcriptional activation of YY1.