LncRNA-XIST From BMSCs-derived Exosomes Regulates MiR-655/ACLY Signal Axis To Promote The Progression Of Osteosarcoma

Background:Long non-coding RNA X-inactive specific transcript（LncRNA-XIST）regulates the progression of various tumors,including osteosarcoma.Bone marrow mesenchymal stem cells（BMSCs）can be recruited to osteosarcoma tissues and can affect osteosarcoma progression by secreting exosomes.However,whether BMSCs-derived exosomes transmit LncRNA-XIST to regulate the growth and metastasis of osteosarcoma and the mechanism thereof are still unclear.Methods:In this study,we used BMSCs-derived exosomes to treat human osteosarcoma cell lines MG63 and 143B.Based on si RNA intervention on the level of LncRNA-XIST in BMSCs,we analyzed the changes in cell proliferation,migration and invasion capabilities by CCK-8,EdU labeling and transwell chambers.Bioinformatics,RNA pulldown and dual luciferase reporter gene experiments were used to study the binding of LncRNA-XIST to miR-655,and the interaction between miR-655 and ACLY.The 143B/LUC cell line was used to establish an orthotopic osteosarcoma animal model to verify the effect on growth and metastasis of osteosarcoma by the LncRNA-XIST from BMSCs exosomes through miR-655.Lipid deposition and protein expression changes were detected by Oil Red O staining,western blot and commercial kits.Results:First,through characterization of biological characteristics,it was confirmed that BMSCs were in good state,good purity,and had osteogenic and adipogenic differentiation potential;it was found that BMSCs^exo could be absorbed by osteosarcoma cell lines MG63 and 143B,and contributed to the upregulation of LncRNA-XIST in osteosarcoma cell lines MG63 and 143B;further construction of si XIST confirmed that BMSCs-derived exosomes promoted the proliferation,migration and invasion of osteosarcoma cell lines MG63 and 143B by delivering LncRNA-XIST.Secondly,based on starbase 3.0,it was predicted that LncRNA-XIST had an interaction relationship with miR-655,and miR-655 mediated the effect of BMSCs-derived exosome promoted the proliferation,migration and invasion of osteosarcoma cells through LncRNA-XIST binding to miR-655.The results of in vivo experiments confirm that BMSCs-derived exosomes can bind osteosarcoma miR-655through LncRNA-XIST to promote tumor growth and metastasis.Finally,the starbase 3.0 online database was used to predict that the downstream target genes of miR-655,which were ARPP19,TOB1 and ACLY;BMSCs-derived exosomes could promote the expression of ACLY in osteosarcoma cells,inhibit LncRNA-XIST,and decrease the expression level of ACLY.On this basis,the expression of miR-655 was down-regulated,and the expression of ACLY was restored,while the protein levels of ARPP19 and TOB1 did not change among the treatment groups,and the in vivo levels were consistent with the in vitro results;BMSCs-derived exosomal LncRNA-XIST can promote the expression of ACLY in osteosarcoma cells by binding to miR-655,which leads to lipid deposition in osteosarcoma.Further detection of cell viability,proliferation,migration and invasion ability showed that BMSCs-derived exosomal LncRNA-XIST increased the proliferation,migration and invasion ability of osteosarcoma cells through miR-655/ACLY signaling.Conclusions:1.Treatment of osteosarcoma cells with BMSCs-derived exosomes can increase the level of LncRNA-XIST in cells,and promote cell proliferation,migration and invasion.2.After BMSCs-derived exosome LncRNA-XIST enters osteosarcoma cells,it can bind and down-regulate the level of miR-655 in osteosarcoma cells through the ce RNA mechanism so as to promotes osteosarcoma cells proliferation,migration and invasion in vitro,as well as in vivo osteosarcoma growth and lung metastasis.3.After BMSCs-derived exosome LncRNA-XIST binds and down-regulates the level of miR-655,it promotes the expression of ACLY in osteosarcoma cells,and further increases the lipid level andβ-catenin signaling activity in the cells.And through this effect,it promotes the process of osteosarcoma cell proliferation,migration and invasion.