The mechanism by which osteosarcomas metastasize is elusive, and challenges remain regarding its treatment with modalities including immunotherapy. CXCL12 is deeply involved in the process of tumor metastasis and T-cell homing, which is driven by a chemokine gradient, but healthy bones are supposed to preferentially express CXCL12. Here, we show for the first time that osteosarcomas epigenetically downregulate CXCL12 expression via DNA methyltransferase 1 (DNMT1) and consequently acquire the ability to metastasize and to impair cytotoxic T-cell homing to the tumor site. Analysis of human osteosarcoma cases further revealed that CXCL12 expression strongly correlated with overall survival. Evaluations on fresh human chemotherapy-free osteosarcoma samples also showed a positive correlation between CXCL12 concentration and the number of intratumoral lymphocytes. Critically, treatment targeting DNMT1 in immunocompetent mouse models significantly elevated expression of CXCL12 in tumors, resulting in a robust immune response and consequently eradicating early lung metastases in addition to suppressing subcutaneous tumor growth. These antitumor effects were abrogated by CXCL12-CXCR4 blockade or CD8+ T-cell depletion. Collectively, our data show that CXCL12 regulation plays a significant role in both tumor progression and immune response, and targeting CXCL12 is promising for therapeutics against osteosarcoma.Significance: Epigenetic regulation of CXCL12 controls metastasis and immune response in osteosarcoma, suggesting epigenetic therapies or therapies targeting CXCL12 have potential for therapeutic intervention in osteosarcoma. Cancer Res; 78(14); 3938-53. ©2018 AACR.
©2018 American Association for Cancer Research.