BACKGROUND:Brain metastasis (BM) is associated with poor prognosis in patients with non-small cell lung cancer (NSCLC). Recent studies demonstrated that microRNA-330-3p (miR-330-3p) was involved in NSCLC brain metastasis (BM). However, the exact parts played by miR-330-3p in BM of NSCLC remain unknown. Discovery and development of biomarkers and elucidation of the mechanism underlying BM in NSCLC is critical for effective prophylactic interventions. Here, we evaluated the expression and biological effects of miR-330-3p in NSCLC cells and explored the underlying mechanism of miR-330-3p in promoting cell migration and invasion in NSCLC. METHODS:Stable over-expression and knockdown of miR-330-3p in NSCLC cells was constructed with lentivirus. Expression levels of miR-330-3p in NSCLC cells were quantified by quantitive real-time PCR (qRT-PCR). The effects of miR-330-3p on NSCLC cells were investigated using assays of cell viability, migration, invasion, cell cycle, apoptosis, western blotting, immunohistochemical, and immunofluorescence staining. A xenograft nude mouse model and in situ brain metastasis model were used to observe tumor growth and brain metastasis. The potential target of miR-330-3p in NSCLC cells was explored using the luciferase reporter assay, qRT-PCR, and western blotting. The miR-330-3p targets were identified using bioinformatics analysis and verified by luciferase reporter assay. The correlation between GRIA3 and DNA methyltransferase (DNMT) 1 and DNMT3A was tested by RT-PCR, western blotting, and co-immunoprecipitation (IP). RESULTS:miR-330-3p was significantly up-regulated in NSCLC cell lines. MTT assay, transwell migration, and invasion assays showed that miR-330-3p promoted the growth, migration, and invasion of NSCLC cells in vitro and induced tumor growth and metastasis in vivo. Luciferase reporter assays showed that GRIA3 was a target of miR-330-3p. qRT-PCR and western blotting exhibited that miR-330-3p promoted the growth, invasion, and migration of NSCLC cells by activating mitogen-activated protein kinase (MAPK)/extracellular-regulated protein kinases (ERK) signaling pathway. Furthermore, miR-330-3p up-regulated the total DNA methylation in NSCLC cells, and co-IP-demonstrated GRIA3 was directly related with DNMT1 and DNMT3A. CONCLUSIONS:miR-330-3p promoted the progression of NSCLC and might be a potential target for the further research of NSCLC brain metastasis.