Long Noncoding RNA FAL1 Promotes Cell Proliferation, Invasion and Epithelial-Mesenchymal Transition Through the PTEN/AKT Signaling Axis in Non-Small Cell Lung Cancer

Background/Aims: Recently, long non-coding RNAs (lncRNAs) have been found to have many biological effects in different cancer stages. Several studies have revealed that focally amplified lncRNA on chromosome 1 (FAL1) regulates cancer progression via p21. However, the expression and mechanism of FAL1 in non-small cell lung cancer (NSCLC) still remain unclear. Methods: We detected the FAL1 level in NSCLC tissues and in established cell lines using quantitative real-time PCR and evaluated the clinical significance. FAL1 was silenced or overexpressed using siRNA or lentivirus to study whether FAL1 affected cell proliferation, invasion and migration. Xenograft growth and pulmonary metastasis were observed using nude mouse models. The mechanisms were explored with western blotting and immunohistochemistry. Results: FAL1 was significantly overexpressed in NSCLC compared with adjacent normal tissues, and a high level of FAL1 correlated with poor histological grade, increased lymph node metastasis and advanced TNM stage. Loss- and gain-of-function experiments in vitro verified that knockdown of FAL1 inhibited cell proliferation, invasion, migration and EMT via the PTEN/AKT pathway. Furthermore, an in vivo assay confirmed that overexpression of FAL1 facilitated tumor growth and metastasis. Conclusion: FAL1 may promote tumorigenesis and progression of NSCLC through the PTEN/AKT axis, which could lead to lncRNA-related diagnostics and therapeutics in NSCLC.