Long noncoding RNA SOX21‐AS1 regulates the progression of triple‐negative breast cancer through regulation of miR‐520a‐5p/ORMDL3 axis

Abstract Recently, long noncoding RNAs (lncRNAs) have been reported as a new kind of controllers about cancer processes in biology. In spite of the dysregulation of lncRNAs in various kinds of cancers, only a little of the information was effective on the expression configuration and inner effects of lncRNAs in triple‐negative breast cancer (TNBC). This study valued the expression of lncRNA SOX21‐AS1 and the biological role it played in TNBC. In our research, SOX21‐AS1 had a high expression in TNBC cell lines. The functional experiments showed that knockdown of SOX21‐AS1 obviously restrained cell proliferation, migration, invasion, and epithelial‐mesenchymal transition process and promoted cell apoptosis. Mechanistically, SOX21‐AS1 was found to bind with miR‐520a‐5p. Besides, ORMDL3 was identified as a downstream target of miR‐520a‐5p, and the suppressed ORMDL3 expression induced by silenced SOX21‐AS1 could be restored by miR‐520a‐5p inhibition. Further, data from rescue assays revealed that SOX21‐AS1 could regulate the malignancy of TNBC via miR‐520a‐5p/ORMDL3 axis. All in all, we identified that SOX21‐AS1 regulated the cellular process of TNBC cells via antagonizing miR‐520a‐5p availability to upregulate ORMDL3 expression.