The correlation between morphology and the expression of TGF-β signaling pathway proteins and epithelial-mesenchymal transition-related proteins in synovial sarcomas

Synovial sarcoma (SS) is a malignant tumor of soft tissue and is noted for late local recurrence and metastasis. Aberrant epithelial-mesenchymal transition (EMT) has been implicated in the pathogenesis of diverse human malignancies. Immunohistochemical techniques were used to assess EMT-related proteins (E-cadherin, N-cadherin, β-catenin, Snail, and Slug) and the TGF-β1 pathway (TGF-β1 and Smad2/3) proteins expression in different histological subtypes and epithelial mesenchymal compositions of SS. The expression of cell-surface (E-cadherin) and cytoskeletal proteins (β-catenin) were higher significantly in biphasic SSs (BSSs) (70.4%, 51.9%) than MFSSs (both for 10%). Among monophasic fibrous SSs (MFSSs) samples, E-cadherin protein expression was negatively correlated with expression Snail, Slug, TGF-β1, and Smad2/3. The expression levels of Snail and Smad2/3 were correlated with the pTNM stage (I-II vs. III-IV; P=0.047, P=0.021) and TGF-β1 exhibited a tendency toward a positive correlation with pTNM stage (I-II vs. III-IV; P=0.052), but did not correlate with the histological grade (p>0.05). Interestingly, our data showed that expression of E-cadherin protein correlated with greater survival in SS patients. Overexpression of Snail, and TGF-β1 is associated with suppressed expression of E-cadherin in MFSSs, which supports the hypothesis that the MFSS subtype may have developed via neoplastic EMT.