Transforming Growth Factor-β1-mediated Regulation of circ_DISP3 and ATF3 in Human Triple-negative Breast Cancer Cells

Abstract

Background and objectives: Transforming growth factor-beta 1 (TGF-β1) stimulates activating transcription factor 3 (ATF3), and it is required for the expression of cell proliferation, invasion, and bone metastasis genes in human breast cancer cells. Noncoding RNAs have a crucial role in both physiological and pathological circumstances in the expression of genes. We previously determined the direct targeting of ATF3 by miR-4638-3p, downregulated by TGF-β1 in human triple-negative breast cancer cells (MDA-MB231). This study identified the molecular mechanism of downregulating ATF3 targeting miR-4638-3p via circRNA in MDA-MB231 cells. Methods:In-silico analyses were used to identify the list of circRNAs targeting miR-4638-3p. RT-qPCR was performed to determine the expression of shortlisted circRNAs in MDA-MB231 cells. Transient transfection and western blot analyses were carried out to identify the functional role of circ_DISP3 in MDA-MB231 cells. A dual-luciferase reporter assay was used to identify the direct binding of circ_DISP3 and miR-4638-3p. Results:There was an inverse correlation between the expression of circ_DISP3 and miR-4638-3p in these cells. Antisense oligosmediated silencing of circ_DISP3 restored the function of miR-4638-3p, resulting in the downregulation of ATF3 in MDA-MB231 cells. Furthermore, a luciferase reporter assay identified the direct binding of circ_DISP3 toward miR-4638-3p in these cells.Conclusions: TGF-β1 influenced circ_DISP3 to sponge miR-4638-3p, promoting ATF3 expression in MDA-MB231 cells. Silencing this circRNA caused the restoration of miR-4638-3p activity toward targeting ATF3 in these cells. Hence, we suggest that the