Monophasic and biphasic synovial sarcomas abundantly express cancer/testisantigen NY-ESO-1 but not MAGE-A1 or CT7

Synovial sarcomas are high-grade malignant mesenchymal tumors with biphasic (BSS) and monophasic (MSS) variants that carry a pathognomonic cytogenetic alteration, t(X;18), involving the SYT gene on chromosome 18 and one of se veral SSX genes on chromosome X, usually SSX1 or SSX2. Cancer/testis (CT) a ntigens are expressed in a variety of malignant neoplasms but, in normal ti ssues, are restricted to male germ cells. Previous analysis revealed a high incidence and homogeneous expression of MAGE CT antigen in synovial sarcom as. The present study was performed to analyze the expression of 3 CT antig ens, NY-ESO-1, MAGE-A1 and CT7, by immunohistochemistry with 3 monoclonal a ntibodies (MAbs), ES121 (anti-NY-ESO-1), MA454 (anti-MAGE-A1) and CT7-33 (a nti-CT7), in 25 synovial sarcomas (12 MSS 13 BSS) typed for the t(X;18)-der ived fusion transcript by RT-PCR (19 SYT-SSX1, 6 SYT-SSX2). NY-ESO-1 immuno reactivity was found in 20/25 (80%) cases, and antigen expression was homog eneous in 14/20 NY-ESO-1-positive cases. Both morphologic variants and both translocation types were NYESO-1-positive, whereas 5 SYT-SSX 1 tumors (I M SS, 4 BSS) were NY-ESO-1-negative. MAb MA454 was immunoreactive with 4/25 c ases (2 MSS, 2 BSS; 3 SYT-SSX 1, 1 SYT-SSX2), and MAb CT7-33 was immunoreac tive with only 2/25 cases (both BSS, SYT-SSX1). Expression of MAGE-A1 and C T7 was heterogeneous in all positive cases. Our study shows that NY-ESO-1 i s highly expressed in a homogeneous pattern in synovial sarcomas of both mo rphologic variants and both translocation types, making these tumors an att ractive target for NY-ESO-1 antigen-based immunotherapy. (C) 2001 Wiley-Lis s, Inc.