M2-type tumor-associated macrophages depend on the upregulation of LncRNA FGD5-AS1 to facilitate the invasive phenotype of non-small cell lung cancer cells.
BACKGROUND In non-small cell lung cancer (NSCLC), M2-type tumor-associated macrophages (M2-TAMs) promote malignancy development, and long non-coding RNA FGD5 antisense RNA 1 (FGD5-AS1) is upregulated. However, it remains unclear whether M2-TAMs exert their effects by regulating FGD5-AS1. METHODS THP-1 cells differentiation into M2-type macrophages was induced, before 48 h of NSCLC cell co-culture to simulate M2-TAMs. The functions of M2-TAMs in NSCLC cell biological behavior following FGD5-AS1 silencing were assessed through loss-of-function experiments, such as CCK-8, scratch, Transwell, and nude mouse tumorigenesis assays. Epithelial-mesenchymal transition (EMT)-related protein levels were measured by Western blotting, whereas FGD5-AS1 levels within cells were determined through qRT-PCR assay. The subcellular localization of FGD5-AS1 in NSCLC cells was determined using fluorescence in situ hybridization and subcellular fractionation assays. Finally, bioinformatics analysis was conducted to predict miRNAs that potentially bind to FGD5-AS1, followed by experimental validation using a dual-luciferase assay. RESULTS Under co-culture conditions with M2-TAMs, the viability, migratory capacity, invasive potential, and EMT of NSCLC cells were significantly enhanced, accompanied by an upregulation in the expression level of FGD5-AS1. However, silencing of FGD5-AS1 in NSCLC cells led to inhibition of proliferation, migration, invasion, and EMT in cells co-cultured with M2-TAMs, along with a reduction in tumorigenic potential. In NSCLC cells, FGD5-AS1 interacted with miR-22-3p by acting as a sponge, thereby modulating the expression level of miR-22-3p. CONCLUSION M2-TAMs promote the invasive phenotype of NSCLC cells via upregulating the expression of FGD5-AS1 in NSCLC cells.