Evaluation of expression of cancer stem cell markers and fusion gene in synovial sarcoma: Insights into histogenesis and pathogenesis.

Synovial sarcoma (SS) is an aggressive soft tissue tumor, with uncertain histological and cellular origin. SYT-SSX is considered to be responsible for sarcoma initiation and progression. The histogenesis and pathogenesis of this tumor are poorly understood, and prognosis of patients of SS is unsatisfactory. Recent studies have shown an association of cancer stem cells with the initiation and development of tumors. We explored immunohistochemical expression level of stem cell associated markers to determine the possible histogenesis and pathogenesis of SS. Fusion gene SYT-SSX was tested to assess diagnostic value and the molecular pathological features. We obtained the clinicopathological data of 20 SS patients, immunohistochemical staining were used to evaluate stem cell-associated markers included CD133, CD29, CD44, nestin, and ALDH1. Fusion gene SYT-SSX was tested by reverse transcriptase-polymerase chain reaction (RT-PCR). Twenty SS cases were observed and the positive immuno-expression results showed CD133 (17/20), CD29 (11/20), CD44 (11/20), nestin (6/20), and ALDH1 (5/20). Fusion gene SYT-SSX was successfully detected by RT-PCR from 18 available samples. The expression of stem cell-associated markers (CD133, CD29, CD44, Nestin, and ALDH1) and clinical data (age, gender, sites, tumor size, histological type, tumor stage, and distant metastases) did not show statistically significant relationship (P>0.05), whereas, statistically significance between ALDH1 and metastases was observed (P<0.01). The ALDH1 positive synovial sarcoma (ALDH1+ SS) cases had significantly poor prognosis compared to ALDH1 negative synovial sarcoma (ALDH1- SS) cases (P<0.05). Immunohistochemical results indicated different expression levels of the five cancer stem cell markers in SS suggesting that SS may arise from cancer stem cells. Fusion gene SYT-SSX may play a critical role in the molecular pathological of SS.