Long non-coding RNA LINC00261 promotes progression of gastric cancer by regulating miR-324-3p/EST1.

Objective: To investigate the role of long non-coding RNA LINC00261 in regulating E26 transcription factor 1 (EST1) by interfering with the expression of miR-324-3p in promoting the development of gastric cancer (GC). Methods: Cancer tissues and corresponding adjacent normal tissues of GC patients (n=80) who underwent surgical treatment in 363 Hospital from June 2018 to October 2020 were collected as research samples, and the expression levels of LINC00261 and miR-324-3p were detected by qRT-PCR. The correlation between LINC00261 and clinicopathological parameters were analyzed. siRNA (si-LINC00261), miRNA mimic (miR-324-3p), miRNA inhibitor (miR-324-3p in) and their corresponding controls were transfected into MGC-803 and SGC- 7901 cells. Clonogenesis assay was used to evaluate cell proliferation. The Transwell assay assessed cell migration and invasion. The protein expression levels of E-cadherin, N-cadherin and ETS1 were detected by Western blot. Tumor xenotransplantation assay was used to detect the tumorigenesis of LINC00261 in vivo. Luciferase report and RNA precipitation were used to analyze the interaction between LINC00261, miR-324-3p and EST1. Results: Compared with adjacent tissues, the expression of LINC00261 in GC tissues was significantly up-regulated with statistical significance (P<0.05). The expression of LINC00261 was correlated with TNM stage, tissue differentiation degree, lymph node metastasis and microvascular invasion (P<0.05). The database prediction, firefly luciferase assay and RNA immunoprecipitation results showed that LINC00261 had a targeted relationship with miR-324-3p. The level of miRdoi: 324-3p in GC tissues was significantly lower than that in paracellular normal tissues (P<0.05). There was a negative correlation between miR-324-3p level and LINC00261 expression (P<0.05). Compared with in NC+si-NC group, the cell proliferation, migration and invasion ability and the expression of N-cadherin in in NC+si-LINC00261 group were significantly inhibited (P<0.05), while the expression of E-cadherin was significantly increased (P<0.05). Compared with in NC+si-LINC00261 group, cell proliferation, migration and invasion ability and expression of N-cadherin in si-LINC00261+miR-324-3p in group were significantly increased (P<0.05), while the expression of E-cadherin was significantly decreased (P<0.05). Targetscan prediction and firefly luciferase assay showed that ETS1 was the downstream binding site of miR-324-3p. After transfection with miR-324-3p, ETS1 protein level was significantly down-regulated (P<0.05), but after transfection with miR-324-3p in, ETS1 protein level was significantly up-regulated (P<0.05). The expression of ETS1 in GC tissue was significantly higher than that in adjacent normal tissue (P<0.05). The miR-324-3p level was negatively correlated with ETS1 (P<0.05). The tumor weight of MGC-803 cells transfected with si-LINC00261 was lower than that of MGC-803 cells transfected with si-NC (P<0.05), and the protein level of ETS1 in si-LINC00261-derived tumors was lower than that of si-NC tumors (P<0.05). Conclusion: LINC00261 is highly expressed in GC tissue, which may affect EST1 expression and promote GC progress by regulating miR-324-3p. [ABSTRACT FROM AUTHOR]