Prognostic significance of HLA class I expression in osteosarcoma defined by anti‐pan HLA class I monoclonal antibody, EMR8‐5

With the goal of establishing efficacious peptide‐based immunotherapy for patients with bone and soft tissue sarcomas, we previously identified the cytotoxic T lymphocyte‐defined osteosarcoma antigenic gene Papillomavirus binding factor . The present study was designed to determine the status of HLA class I expression in osteosarcoma and other bone and soft tissue sarcomas. Seventy‐four formalin‐fixed paraffin‐embedded specimens of various bone and soft tissue sarcomas, including 33 osteosarcomas, were stained with the anti‐HLA class I monoclonal antibody EMR8‐5, which we recently generated. The expression of HLA class I was lost or downregulated in 46 of these specimens (62%). With respect to osteosarcoma, loss or downregulation of HLA class I expression was seen in 13 (52%) of 25 primary tumors and seven (88%) of eight metastatic tumors. In six of 11 HLA class I‐negative osteosarcoma specimens, the expression of β‐2 microglobulin was also lost. Subsequently the prognostic significance of HLA class I expression was analyzed in 21 patients with osteosarcoma who had completed multidrug neoadjuvant chemotherapy and undergone adequate surgery. Patients with osteosarcoma highly expressing HLA class I showed significantly better overall and event‐free survival than those with HLA class I‐negative osteosarcoma. In contrast, such prognostic significance of HLA class I expression was not found in 15 patients with malignant fibrous histiocytoma of soft tissue. These findings suggest that the class I‐restricted cytotoxic T lymphocyte pathway plays a major role in immune surveillance of patients with osteosarcoma. ( Cancer Sci 2006; 97: 1374–1380)