X-inactivation-specific transcript (XIST) is a long noncoding RNA (lncRNA) that functions as an indicator of various human tumors, including those of breast cancer. This study was conducted to characterize a novel regulatory network involving XIST in breast cancer cells. The mRNAs of XIST, miR-125b-5p, and NOD-like receptor family CARD domain containing 5 (NLRC5) in breast cancer cells and tissues were analyzed using quantitative real-time polymerase chain reaction. Cell proliferation, apoptosis, migration, and invasion were separately detected via cell counting kit-8, flow cytometry, and Transwell assays. The relationships between XIST, miR-125b-5p, and NLRC5 were predicted and then confirmed using the dual-luciferase reporter assay. NLRC5 protein expression was quantitated using western blot assays. XIST was found to be overexpressed in breast cancer tissues and cells, which was accompanied by miR-125b-5p downregulation and NLRC5 upregulation. XIST knockdown significantly repressed cell proliferation, anti-apoptosis, migration, and invasion activities in breast cancer cells, and the loss of miR-125b-5p had a similar effect. XIST was shown to sponge miR-125b-5p, which in turn targeted NLRC5. NLRC5, a breast cancer promotor, is negatively regulated by miR-125b-5p. Moreover, the downregulation of NLRC5 induced by the loss of XIST was significantly reversed by miR-125b-5p knockdown. In conclusion, the lncRNA XIST promotes the malignancy of breast cancer cells partly by competitively binding to miR-125b-5p, which then led to increased NLRC5 expression. Our study suggests that targeting XIST may be a possible treatment for breast cancer.
Keywords: LncRNA XIST; NLRC5; breast cancer cell carcinoma; miR-125b-5p.
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