Expression of cadherins and their undercoat proteins (alpha-, beta-, and gamma-catenins and p120) and accumulation of beta-catenin with no gene mutations in synovial sarcoma

E-cadherin, the major intercellular adhesion molecule of epithelial cells, is important in determining the architecture of sarcomas, especially those showing epithelioid features. In addition to its role in cell adhesion, bet a -catenin, a cadherin undercoat protein, has been shown to function as a d ownstream transcriptional activator of the Wnt/Wingless signaling pathway. In order to evaluate the significance of the cadherin cell adhesion system and the Wnt/Wingless signaling pathway in the morphogenesis and/or tumorige nesis of synovial sarcoma (a major type of sarcoma with epithelioid feature s), immunoreactivity for pan-cadherin, E-cadherin, and their undercoat prot eins (alpha-, beta ,and gamma -catenins and p120) was evaluated in 15 synov ial sarcomas. Immunoreactivity for pan-cadherin, E-cadherin, alpha -catenin , beta -catenin, and p120 was observed in all 15 specimens. Immunoreactivit y for pan-cadherin was stronger than that for E-cadherin. Expression of gam ma -catenin was detected in ten specimens. Although beta -catenin was obser ved only at the cell-cell boundaries in four specimens, it was present in t he nucleus and cytoplasm and at the cell-cell boundaries in the other 11, s uggesting constitutional activation of the Wnt/Wingless signaling pathway i n synovial sarcoma. Direct sequencing for exon 3 of the beta -catenin gene, however, revealed no mutations in any of the 15 specimens. In conclusion, other types of cadherin besides E-cadherin, together with cadherin undercoa t proteins, may play a role in cell adhesion in synovial sarcoma. Further-m ore, mechanisms other than mutation of exon 3 of the beta -catenin gene may activate the Wnt/Wingless signaling pathway in this type of tumor.