Synovial Sarcoma Microvesicles Harbor the SYT-SSX Fusion Gene Transcript: Comparison of Different Methods of Detection and Implications in Biomarker Research.

A Fricke,S U Eisenhardt,A F V Cimniak,S Nestel,B Heimrich,I Nazarenko,D Braig,M Follo,G B Stark,H Bannasch,P V Ullrich

doi:10.1155/2016/6146047

Abstract

Background. Synovial sarcoma is an aggressive soft-tissue malignancy. This study examines the presence of the SYT-SSX fusion transcript in synovial sarcoma microvesicles as well as its potential role as a biomarker for synovial sarcoma. Patients and Methods. Microvesicle release of synovial sarcoma cells was examined by transmission electron microscopy. RNA-content was analyzed by qPCR, nested PCR, nested qPCR, and droplet digital PCR to compare their sensitivity for detection of the SYT-SSX fusion gene transcript. Whole blood RNA, RNA of mononuclear cells, and microvesicle RNA of synovial sarcoma patients were analyzed for the presence of the fusion gene transcripts. Results. Electron microscopic analysis revealed synovial sarcoma cells releasing membrane-enclosed microvesicles. In vitro, the SYT-SSX fusion gene transcript was detected in both synovial sarcoma cells and microvesicles. Nested qPCR proved to be the most sensitive in detecting the SYT-SSX fusion gene mRNA. In contrast, the fusion gene transcript was not detected in peripheral blood cells and microvesicles of synovial sarcoma patients. Conclusion. Synovial sarcoma cells release microvesicles harboring the SYT-SSX fusion transcript. Nested qPCR proved to be the most sensitive in detecting the SYT-SSX fusion gene mRNA; however, more sensitive assays are needed to detect cancer-specific microvesicles in the peripheral blood of cancer patients.

Highlights

Synovial sarcoma is an aggressive soft-tissue malignancy and constitutes one of the largest subgroups of soft-tissue sarcoma, especially in adolescents and young adults [1, 2]
Since it has been shown that tumor cells release small vesicles containing cell-specific proteins, surface markers, and even mRNA variants specific for certain neoplasms such as the EGFRvIII splice variant in glioblastoma [13], the aim of this study is to evaluate whether microvesicles shed by synovial sarcoma cells carry the tumor-specific fusion gene SYT-SSX transcripts
Electron microscopy showed synovial sarcoma cells releasing microvesicles enclosed by a protective membrane (Figures 1(a)–1(d))

Summary

Introduction

Synovial sarcoma is an aggressive soft-tissue malignancy and constitutes one of the largest subgroups of soft-tissue sarcoma, especially in adolescents and young adults [1, 2]. The cytogenetically defined translocation t(X;18)(p11.2;q11.2) found in human synovial sarcoma results in the fusion of the SYT gene on chromosome 18 to SSX1, SSX2, or SSX4 on chromosome X at Xp11.2, leading to the formation of SYTSSX fusion transcript [3,4,5]. The presence of the SYT-SSX fusion transcript enables specific and sensitive molecular diagnosis of synovial sarcoma, being detectable in almost all synovial sarcoma tissues. The fusion gene transcript was not detected in peripheral blood cells and microvesicles of synovial sarcoma patients. Nested qPCR proved to be the most sensitive in detecting the SYT-SSX fusion gene mRNA; more sensitive assays are needed to detect cancer-specific microvesicles in the peripheral blood of cancer patients

Objectives

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Results

Conclusion