Advances on immunotherapy for osteosarcoma.

Osteosarcoma is the most common primary bone cancer in children and young adults. Limited progress has been made in improving the survival outcomes in patients with osteosarcoma over the past four decades. Especially in metastatic or recurrent osteosarcoma, the survival rate is extremely unsatisfactory. The treatment of osteosarcoma urgently needs breakthroughs. In recent years, immunotherapy has achieved good therapeutic effects in various solid tumors. Due to the low immunogenicity and immunosuppressive microenvironment of osteosarcoma, immunotherapy has not yet been approved in osteosarcoma patients. However, immune-based therapies, including immune checkpoint inhibitors, chimeric antigen receptor T cells, and bispecfic antibodies are in active clinical development. In addition, other immunotherapy strategies including modified-NK cells/macrophages, DC vaccines, and cytokines are still in the early stages of research, but they will be hot topics for future study. In this review, we showed the functions of cell components including tumor-promoting and tumor-suppressing cells in the tumor microenvironment of osteosarcoma, and summarized the preclinical and clinical research results of various immunotherapy strategies in osteosarcoma, hoping to provide new ideas for future research in this field.