Long non-coding RNA MEG3 regulates migration and invasion of lung cancer stem cells via miR-650/SLC34A2 axis

Long non-coding RNA maternally expressed gene 3 (MEG3) is related to the occurrence and development of non-small cell lung cancer (NSCLC). However, the function and underlying molecular mechanisms of MEG3 in lung cancer stem cells (LCSCs) are still unclear. LCSCs were determined in lung cancer cells using fluorescence-activated cell sorting (FACS). qRT-PCR and western blot were performed to examine the expressions of MEG3, miR-650, solute carrier family 34 member 2 (SLC34A2), octamer-binding transcription factor 4 (Oct4), and CD133. Sphere assay was employed to evaluate sphere-forming ability. Cell migration and invasion were analyzed by Transwell assay. The relationships among MEG3, miR-650, and SLC34A2 were validated by luciferase reporter, RIP, and RNA pulldown assays. We found MEG3 was downregulated in LCSCs. MEG3 depletion strengthened stem cell-like characteristics and sphere-forming ability in LCCs. Upregulation of MEG3 suppressed migration and invasion in LCCs and LCSCs. miR-650 was bound to MEG3 and upregulated in LCSCs. miR-650 inhibitor alleviated si-MEG3-induced promotion of stem cell-like characteristics in lung cancer cells (LCCs) H1299. Furthermore, miR-650 mimic attenuated the MEG3 upregulation-mediated inhibition of migration and invasion. In addition, SLC34A2 was a target of miR-650 and downregulated in LCSCs. miR-650 mimic induced stem cell-like characteristics in LCCs, which was weakened by overexpression of SLC34A2. In contrast, the repression of SLC34A2 mitigated the miR-650 silencing-induced inhibition of migration and invasion in LCCs and LCSCs. Besides, MEG3 regulated SLC34A2 expression by sponging miR-650. Importantly, SLC34A2 weakened MEG3-mediated stem cell-like state and cell metastasis. Our data suggested MEG3 was involved in stem cell-like state of LCCs and curbed migration and invasion through miR-650/SLC34A2 axis in NSCLC.