DNA Methylation Regulation Of CXCL12 Plays A Critical Role In Mediating Tumor Progression And The Immune Response In Osteosarcoma

Osteosarcoma is one of the most common primary malignant bone tumors.It is more common in children and adolescents,followed by the elderly?bimodal phenomenon?.Osteosarcoma is prone to metastasis and the most common metastatic site is the lung,which is often the cause of treatment failure.Metastatic osteosarcoma is associated with a poor survival and the 5-year overall survival rate was less than 20%.At present,the mechanism of lung metastasis of osteosarcoma remains unknown.In addition,there are still challenges in treating osteosarcoma with novel therapies such as immunotherapy.Chemokine has been a hot area of research in tumor immunotherapy.Chemokines can activate and promote immune cell migration.Moreover,chemokines can promote tumor proliferation,invasion and metastasis.CXCL12 has two sides in the process of tumorigenesis and development.CXCL12 is involved in both tumor metastasis and T cell homing,which are driven by chemokine gradients.In addition,the relationship between the CXCL12-CXCR4 biological axis and the prognosis of patients with osteosarcoma remains controversial.In the first part,we explored the role of CXCL12-CXCR4 biological axis in osteosarcoma.We found that osteosarcoma regulated CXCL12 expression by methylation via DNA methyltransferase 1?DNMT1?,and then affects tumor cell proliferation,migration and metastasis.The CXCL12-CXCR4 axis did affect tumor cell proliferation,migration,and metastasis.In the second part,we explored the effect of abnormal expression of CXCL12 on lymphocytes in osteosarcoma and first combined CXCL12 and CXCR4 to explore the correlation between this biological axis and the prognosis of patients with osteosarcoma.We found that the concentration of CXCL12 in tumors was positively correlated with the number of lymphocytes,highlighting the importance of CXCL12 in the homing of lymphocytes.Patients in the CXCR4^negCXCL12^higroup had the best prognosis,and patients in the CXCR4^posCXCL12^logroup had the worst prognosis,suggesting that this axis,especially CXCL12,can be used as a potential molecular target for clinical treatment.These encouraging results provided new ideas for the subsequent demethylation treatment of osteosarcoma and its role in immune response.In the third part,we further explored the specific role of DNA methylation regulation of CXCL12 in mediating osteosarcoma progression and immune response.We found that inhibition of DNMT can promote the expression of CXCL12 in human osteosarcoma cells.Demethylation treatment with decitabine?DAC,DNMT inhibitor?in normal mouse osteosarcoma models can significantly increase the expression of CXCL12 in tumors,thereby causing a strong immune response and significantly inhibiting tumor growth and lung metastasis.Blocking the CXCL12-CXCR4 axis or deleting CD8⁺T cells can reverse these outcomes.In addition,we found that decitabine treatment in vitro can inhibit osteosarcoma cell proliferation,while decitabine treatment in vivo does not promote tumor growth.In summary,this study proves that CXCL12 plays an important regulatory role in osteosarcoma progression and immune response,providing a basis for CXCL12-targeted treatment of osteosarcoma.