Down-regulation of miR-146b-5p promotes malignant transformation of fusion cells after co-culture of macrophages with glioma stem cells in vitro

Abstract

Objective: To observe mutual interactions between macrophages(Mφ) and glioma stem cells (GSCs)in dual-color tracing model in vitro, to identify the biological characteristics of fusion cells in multiple levels, and to analysis the relevant molecular mechanisms. Methods: Red fluorescent protein(RFP) gene was stably transfected into human GSCs cell line SU4. Mφ cells were obtained from Balb/c nude mice with enhanced green fluorescent protein (EGFP) expression. Then two cells were co-cultured in dual-color tracing platform. RFP/EGFP double positive cells with high proliferation ability were mono-cloned. The fusion cells were verified by Western blot, fluorescence in situ hybridization, immunocytochemistry and chromosome karyotype analysis.The biological characteristics of fusion cells were further analyzed, together with relevant molecular changes. Results: RFP / EGFP double positive cells were obtained through in vitro co-culture. RFP and EGFP coexpression were proved at transcriptional and translational levels in the fusion cells. They also co-expressed GSCs marker Nestin and Mφ marker CD68, and karyotype analysis showed two types of characteristic chromosomes, which confirmed that the fusion cells originated from spontaneous fusion between SU4-RFP and Mφ.Fusion cell proliferation rate and invasion ability were higher than SU4-RFP, which were relevant with down-regulation of miR-146b-5p and activation of STAT3. Fusion cells transfected with miR-146b-5p showed a higher apoptosis rate(18.83%) and lower tumor formation(4/5). Conclusion: Mφ could fuse with GSCs spontaneously in local tumor micro-environment. The proliferation and invasion abilities of fusion cells were higher than their parent cells, which were relevant with down-regulation of miR-146b-5p and activation of STAT3. It revealed the possible mechanisms of malignant progression of gliomas.