Non-small cell lung cancer (NSCLC) is a malignant lung cancer and accounts for 80% of lung cancer-related deaths. Long non-coding RNA maternally expressed gene 3 (MEG3) has been identified as a tumor suppressor in multiple cancers. However, the regulatory mechanism of MEG3 in NSCLC development is still largely unknown. The expression levels of MEG3, microRNA-31-5p (miR-31-5p) and tissue inhibitor of metalloproteinase 3 (TIMP3) in NSCLC tumors and cells were measured by quantitative real time polymerase chain reaction (qRT-PCR). Cell viability, apoptosis, migration and invasion were detected by cell counting kit-8 (CCK-8), flow cytometry, western blotting and transwell assays, respectively. Xenograft mouse models were established by subcutaneously injecting NSCLC cells stably transfected with Lenti-pcDNA or Lenti-MEG3. The interaction between miR-31-5p and MEG3 or TIMP3 was validated by luciferase reporter and RNA immunoprecipitation (RIP) assays. MEG3 and TIMP3 levels were up-regulated, whereas miR-31-5p expression was down-regulated in NSCLC tumors and cells compared with normal tissues and cells. Overexpression of MEG3 repressed cell proliferation, migration and invasion, but induced apoptosis in NSCLC cells. More importantly, MEG3 effectively hindered tumor growth in vivo. Next, luciferase reporter and RIP assays confirmed the interaction between miR-31-5p and MEG3 or TIMP3. Pearson's correlation coefficient revealed that miR-31-5p was inversely correlated with MEG3 or TIMP3. Rescue experiments indicated that MEG3 regulated TIMP3 expression by sponging miR-31-5p in NSCLC cells. Thus, MEG3 inhibited cell proliferation, migration and invasion, but enhanced apoptosis in NSCLC cells through up-regulating TIMP3 expression by regulating miR-31-5p, indicating novel biomarkers for the therapy of NSCLC.
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