lncRNA GSEC Promotes the Progression of Triple Negative Breast Cancer (TNBC) by Targeting the miR-202-5p/AXL Axis

BACKGROUND: This study aimed to explore the biological functions of G-quadruplex-forming sequence containing lncRNA (GSEC) in triple negative breast cancer (TNBC). METHODS: The expression of GSEC in TNBC tissues was evaluated by qRT-PCR. Cell viability was evaluated by Cell Counting Kit-8 assay. Cell proliferation was evaluated by 5-ethynyl-20-deoxyuridine (EdU) staining assay. Cell invasion and migration were evaluated by Transwell assay. Gain- and loss-function assays were performed to assess the biological functions of GSEC in TNBC. The interactions between GSEC, miR-202-5p and AXL were determined by luciferase report assay and RNA immunoprecipitation (RIP) assay. In addition, a nude mouse xenograft model was used to confirm the oncogenic role of GSEC in TNBC. RESULTS: GSEC was significantly upregulated in TNBC tissues and cancer cell lines, and high level of GSEC was associated with advanced tumor stage, positive lymph-node metastasis and the poor prognosis of TNBC patients. Knockdown of GSEC effectively inhibited TNBC cell proliferation, invasion and migration in vitro. GSEC regulated the expression of AXL by directly sponging miR-202-5p. Downregulation of miR-202-5p attenuated GSEC knockdown-induced inhibition on TNBC cell proliferation, invasion and migration in vitro. Meanwhile, overexpression of AXL obviously reversed the inhibitory effects of miR-202-5p mimics in TNBC progression in vitro. CONCLUSION: GSEC functioned as a potential oncogene and promoted AXL-mediated TNBC progression by sponging miR-202-5p, which might be a novel diagnostic and therapeutic target for TNBC.