The Role Of MFG-E8 In Osteosarcoma And Its Potential Mechanisms In The Mediation Of Cellular Functions

Background:Osteosarcoma is a highly malignant tumor that occurs in children and young adults.It is currently treated with surgery and chemotherapy(cisplatin,adriamycin,etc.)and has a high recurrence rate and often a poor 5-year prognosis.According to related reports,the incidence of osteosarcoma in China is about 3-4/1 million/year,while the high incidence in adolescents around 17 years old reaches 9-11/1 million/year,accounting for more than 20% of solid tumors.Amputation caused by osteosarcoma not only causes great pain to the patients themselves but also brings a great burden to their families and society,thus the treatment of osteosarcoma has become one of the hot issues in global medical care.Although the long-term survival rate of patients with osteosarcoma has improved somewhat with the continuous improvement of surgical techniques and the generation of new chemotherapeutic drugs,which can reach about65% after the standardized treatment developed by clinical doctors,this result has lasted for about 40 years.In recent years,gene microarray and sequencing technologies have been rapidly developed to find malignancy-related genes using bioinformatics methods,thus allowing a deeper understanding of osteosarcoma pathogenesis and a more precise search for new molecular therapeutic targets,which can provide new therapeutic avenues to improve patient survival rates and to improve patient quality of life.Researchers have demonstrated that MFG-E8 plays an immunosuppressive or pro-cancer role in many malignancies(melanoma,breast cancer,colon cancer,bladder cancer,etc.)and is associated with poor prognosis,but what role it plays in osteosarcoma is less studied.Objective:The aim of this project was to explore the role and potential mechanisms of MFG-E8 in OS.In addition,the effect of MFG-E8 on the polarization of tumor-associated macrophages(TAM)in OS cell exosomes was also investigated.Methods:We analyzed the expression and related functional enrichment of MFG-E8 using bioinformatics.The expression of MFG-E8 and its relationship with clinicopathology were verified using Western blot and immunohistochemistry(IHC).the effect of MFG-E8 on OS cell proliferation,invasion,migration,and angiogenic capacity was assessed by EDU,CCK-8,and cloning,scratch,migration,invasion,and angiogenesis assays.A xenograft tumor model was constructed to explore the effects of MFG-E8 on OS tumors in vivo.Exosomes were extracted from OS cell supernatants and identified by WB,nanoparticle size(NTA),transmission electron microscopy,and PKH67 assays were performed to assess macrophage uptake of exosomes.RT-PCR,EDU,and transwell assays were performed to assess the effect of exosomes on macrophage polarization,proliferation,and invasion.Results:MFG-E8 is highly expressed in both OS tissues and cells and is associated with poor prognosis in OS patients.Knockdown of MFG-E8 may inhibit the ability of OS cells to proliferate,migrate,invade,and form blood vessels by inhibiting the phosphorylation of the STAT3 signaling pathway.Knockdown of MFG-E8 inhibits tumor growth in vitro.The deletion of MFG-E8 in exosomes inhibited the M2 polarization of TAMs and ultimately affected the value-added and invasion of OS cells.Conclusion:In conclusion,this study highlights the important role of MFG-E8 in the development of osteosarcoma.