Synovial Sarcoma


"A malignant neoplasm arising from tenosynovial tissue of the joints and in synovial cells of tendons and bursae. The legs are the most common site, but the tumor can occur in the abdominal wall and other trunk muscles. There are two recognized types: the monophasic (characterized by sheaths of monotonous spindle cells) and the biphasic (characterized by slit-like spaces or clefts within the tumor, lined by cuboidal or tall columnar epithelial cells). These sarcomas occur most commonly in the second and fourth decades of life. (From Dorland, 27th ed; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1363)" [Source: MeSH, 2014]

A S18-SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is characteristic of nearly all synovial sarcomas. This translocation fuses the SS18T (SYT) gene from chromosome 18 to one of three homologous genes at Xp11, SSX1, SSX2 or SSX4.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Lung Cancer
  • Gene Expression
  • Chromosome Mapping
  • DNA Primers
  • FISH
  • Polymerase Chain Reaction
  • Chromosome Aberrations
  • Survival Rate
  • SS18L1
  • Immunohistochemistry
  • Biomarkers, Tumor
  • SSX1
  • Differential Diagnosis
  • FGFR2
  • Paraffin Embedding
  • Neoplasm Proteins
  • Molecular Sequence Data
  • TLE1
  • Messenger RNA
  • Cancer DNA
  • Soft Tissue Cancers
  • Immunoenzyme Techniques
  • Neoplasm Metastasis
  • Bone Cancer
  • Synovial Sarcoma
  • Repressor Proteins
  • Chromosome X
  • DNA Sequence Analysis
  • EGFR
  • Oncogene Fusion Proteins
  • Proteins
  • Childhood Cancer
  • Base Sequence
  • Cancer RNA
  • Cell Proliferation
  • Amino Acid Sequence
  • Adolescents
  • Translocation
  • Proto-Oncogene Proteins
  • Chromosome 18
  • Gene Expression Profiling
  • Cancer Gene Expression Regulation
  • SS18
  • Karyotyping
Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Mutated Genes and Abnormal Protein Expression (10)

How to use this data tableClicking on the Gene or Topic will take you to a separate more detailed page. Sort this list by clicking on a column heading e.g. 'Gene' or 'Topic'.

TLE1 9q21.32 ESG, ESG1, GRG1 -TLE1 and Synovial Sarcoma
EGFR 7p11.2 ERBB, HER1, mENA, ERBB1, PIG61, NISBD2 Overexpression
-EGFR Overexpression in Synovial Sarcoma
SS18L1 20q13.33 CREST, LP2261 -SS18L1 and Synovial Sarcoma
RNF213 17q25.3 ALO17, MYMY2, MYSTR, NET57, C17orf27, KIAA1618 -RNF213 and Synovial Sarcoma
FGFR2 10q26.13 BEK, JWS, BBDS, CEK3, CFD1, ECT1, KGFR, TK14, TK25, BFR-1, CD332, K-SAM -FGFR2 and Synovial Sarcoma
FOXC1 6p25 ARA, IGDA, IHG1, FKHL7, IRID1, RIEG3, FREAC3, FREAC-3 -FOXC1 and Synovial Sarcoma
SSX2 Xp11.22 SSX, HD21, CT5.2, CT5.2A, HOM-MEL-40 Translocation
-t(X;18)(p11.2;q11.2) SS18-SSX2 in Synovial Sarcoma
SSX4 Xp11.23 CT5.4 Translocation
-t(X;18)(p11.2;q11.2) SS18-SSX4 in Synovial Sarcoma
SS18 18q11.2 SYT, SSXT Translocation
-t(X;18)(p11.2;q11.2) SS18-SSX1 in Synovial Sarcoma
-t(X;18)(p11.2;q11.2) SS18-SSX2 in Synovial Sarcoma
-t(X;18)(p11.2;q11.2) SS18-SSX4 in Synovial Sarcoma
SSX1 Xp11.23 SSRC, CT5.1 Translocation
-t(X;18)(p11.2;q11.2) SS18-SSX1 in Synovial Sarcoma

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Research Publications

Przybyl J, van de Rijn M, Rutkowski P
Detection of SS18-SSX1/2 fusion transcripts in circulating tumor cells of patients with synovial sarcoma.
Diagn Pathol. 2019; 14(1):24 [PubMed] Free Access to Full Article Related Publications
A recent study on 15 patients with synovial sarcoma demonstrated very low prevalence of tumor-specific fusion transcripts in peripheral blood specimens. Our results in an independent cohort of 38 patients with synovial sarcoma support these findings. Synovial sarcoma patients could greatly benefit from a non-invasive monitoring of tumor burden by liquid biopsies. However, given the low detection rate of SS18-SSX1/2 in circulation, we conclude that alternative markers other than the tumor-type specific fusion transcripts should be considered.

Nicola M, Onorati M, Bertola G, et al.
Primary thyroid biphasic synovial sarcoma and synchronous papillary carcinoma: report of a remarkable case.
Pathologica. 2018; 110(2):106-110 [PubMed] Related Publications
Synovial Sarcoma (SS) is the fourth most common soft tissue sarcoma, characterized by translocation t(X;18) (p11.2;q11.2). Although its histological features have been extensively described, this entity is characterized by a wide morphological spectrum so that the recognition can be very challenging at atypical anatomical localization, like the thyroid. We describe a case of a 42-ys-old female patient complaining a cervical swelling due to left intrathyroid nodule, measuring 35 mm in its greatest dimension. A Fine Needle Aspiration Cytology (FNAC) was performed and diagnosis of indeterminate neoplastic lesion, indefinite whether primary or metastatic, was formulated. After complete thyroidectomy, the histological picture of the nodule was characterized by a dual cellular population: several glandular structures composed by columnar cells with clear cytoplasm were embedded in a highly cellular stroma composed of spindle-shaped elements. Immunohistochemistry and molecular biology confirmed the morphological suspicion of SS identifying the fusion transcript SYT-SSX1 and thus ruling out several differential diagnoses which include more common thyroid malignancies. Moreover a synchronous papillary microcarcinoma was detected in the controlateral lobe.
This case is noteworthy since it describes the synchronous presence in the thyroid of two completely different malignancies, the first one belonging to the soft tissue neoplasm category and the other one originating from the thyroid follicular epithelium.

Riggi N, Cironi L, Stamenkovic I
Synovial sarcoma: when epigenetic changes dictate tumour development.
Swiss Med Wkly. 2018; 148:w14667 [PubMed] Related Publications
Synovial sarcoma is a highly aggressive soft tissue malignancy that often affects adolescents and young adults. It is associated with a unique chromosomal translocation that results in the formation and expression of the fusion gene SS18-SSX, which underlies its pathogenesis. Although SS18-SSX provides a potentially unique therapeutic target, all attempts to neutralise it have been unsuccessful thus far. When complete surgical removal of the tumour fails, therapy is limited to largely ineffective cytotoxic drug regimens. Nevertheless, recent discoveries about the mechanisms of SS18-SSX protein function have provided insight into potential alternative therapeutic strategies. SS18-SSX displays oncogenic activity through protein-protein interactions and participation in chromatin remodelling complexes. This review summarises our current understanding of the function of SS18-SSX and the mechanisms by which it alters the epigenetic landscape of permissive cells to induce transformation and the subsequent development of synovial sarcoma.

Brien GL, Remillard D, Shi J, et al.
Targeted degradation of BRD9 reverses oncogenic gene expression in synovial sarcoma.
Elife. 2018; 7 [PubMed] Free Access to Full Article Related Publications
Synovial sarcoma tumours contain a characteristic fusion protein, SS18-SSX, which drives disease development. Targeting oncogenic fusion proteins presents an attractive therapeutic opportunity. However, SS18-SSX has proven intractable for therapeutic intervention. Using a domain-focused CRISPR screen we identified the bromodomain of BRD9 as a critical functional dependency in synovial sarcoma. BRD9 is a component of SS18-SSX containing BAF complexes in synovial sarcoma cells; and integration of BRD9 into these complexes is critical for cell growth. Moreover BRD9 and SS18-SSX co-localize extensively on the synovial sarcoma genome. Remarkably, synovial sarcoma cells are highly sensitive to a novel small molecule degrader of BRD9, while other sarcoma subtypes are unaffected. Degradation of BRD9 induces downregulation of oncogenic transcriptional programs and inhibits tumour progression in vivo. We demonstrate that BRD9 supports oncogenic mechanisms underlying the SS18-SSX fusion in synovial sarcoma and highlight targeted degradation of BRD9 as a potential therapeutic opportunity in this disease.

Pazzaglia L, Pollino S, Vitale M, et al.
miR‑494.3p expression in synovial sarcoma: Role of CXCR4 as a potential target gene.
Int J Oncol. 2019; 54(1):361-369 [PubMed] Related Publications
Synovial sarcoma (SS) is a rare tumour, with dismal survival when metastasis occurs. SS contains a characteristic translocation (X;18)(p11;q11) and the fusion genes appear to be mutually exclusive and concordant in primary and metastatic tumours. Novel prognostic and predictive factors are required. The C‑X‑C motif chemokine ligand 12 (CXCL12)/C‑X‑C chemokine receptor 4 (CXCR4) axis is involved in tumour development and metastatic spread in many types of cancer and previous data have demonstrated a pivotal role of CXCR4 in SS cell migration and invasion. Bioinformatics and biological data indicated CXCR4 is a possible candidate target of miR‑494.3p, known to be involved in tumour progression. In this study, we analysed the expression of miR‑494.3p and its potential target, CXCR4, in a series of SS specimens. A significantly lower miR‑494.3p expression was found in the tumour compared to normal tissue associated with higher levels of CXCR4 both at the gene and protein level. The role of CXCR4 as a potential target of miR‑494.3p was assessed in two SS cell lines (SW982 and SYO‑I). Transfection with miR‑494.3p expression plasmid led to a marked decrease in CXCR4 gene and protein expression, concomitant with a transitory decrease in cell proliferation and migration. The SYO‑I cells also responded with an increased apoptotic fraction. The data of this study also demonstrate that the downregulation of miR‑494.3p in SS surgical specimens, concomitant with an increased expression of its potential target, CXCR4, was more evident in the metastatic subset. In vitro experiments confirmed that miR‑494.3p functioned as a tumour suppressor through the involvement of CXCR4 and ongoing studies are directed to better clarify its role in SS therapeutic strategies.

Michel BC, D'Avino AR, Cassel SH, et al.
A non-canonical SWI/SNF complex is a synthetic lethal target in cancers driven by BAF complex perturbation.
Nat Cell Biol. 2018; 20(12):1410-1420 [PubMed] Free Access to Full Article Related Publications
Mammalian SWI/SNF chromatin remodelling complexes exist in three distinct, final-form assemblies: canonical BAF (cBAF), PBAF and a newly characterized non-canonical complex (ncBAF). However, their complex-specific targeting on chromatin, functions and roles in disease remain largely undefined. Here, we comprehensively mapped complex assemblies on chromatin and found that ncBAF complexes uniquely localize to CTCF sites and promoters. We identified ncBAF subunits as synthetic lethal targets specific to synovial sarcoma and malignant rhabdoid tumours, which both exhibit cBAF complex (SMARCB1 subunit) perturbation. Chemical and biological depletion of the ncBAF subunit, BRD9, rapidly attenuates synovial sarcoma and malignant rhabdoid tumour cell proliferation. Importantly, in cBAF-perturbed cancers, ncBAF complexes maintain gene expression at retained CTCF-promoter sites and function in a manner distinct from fusion oncoprotein-bound complexes. Together, these findings unmask the unique targeting and functional roles of ncBAF complexes and present new cancer-specific therapeutic targets.

Mihály D, Nagy N, Papp G, et al.
Release of circulating tumor cells and cell-free nucleic acids is an infrequent event in synovial sarcoma: liquid biopsy analysis of 15 patients diagnosed with synovial sarcoma.
Diagn Pathol. 2018; 13(1):81 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Synovial sarcoma is a rare soft tissue tumor which contains the unique SS18-SSX1, SS18-SSX2 - or, rarely, SS18-SSX4 - fusion transcripts. It is well known that some soft tissue tumors, like Ewing sarcomas and myxoid liposarcomas, can spread via the blood with free circulating tumor cells (CTC); this can be detected by several sensitive molecular biology methods. Here we report a study of fifteen synovial sarcoma patients with varied clinical backgrounds.
METHOD: After blood withdrawal and nucleic acid isolation, we attempted to detect the SS18-SSX fusion genes from circulating tumor cells or cell-free nucleic acids with nested PCR and droplet digital PCR.
RESULTS: SS18-SSX2 fusion transcript was identified in a small copy number with droplet digital PCR in one case. Nested PCR could not detect any of the fusion transcripts in the examined 15 synovial sarcoma cases.
CONCLUSIONS: Heretofore two case reports could detect CTCs in synovial sarcoma - in the first paper, the patient was diagnosed with poorly differentiated type while the other had a rare primary gastric synovial sarcoma. However, until now, no other studies have detected CTCs in the peripheral blood of synovial sarcoma patients. Based on our findings, we can conclude that detection of the chimeric SS18-SSX fusion gene after surgical excision and/or chemotherapy/radiotherapy is a rare circumstance and hence in itself is not sufficient for monitoring the tumor recurrence. Therefore, monitoring of other possible biomarkers - for example synovial sarcoma specific miRNAs - is recommended.

Zhu J, Cai Y, Xu K, et al.
Beclin1 overexpression suppresses tumor cell proliferation and survival via an autophagy‑dependent pathway in human synovial sarcoma cells.
Oncol Rep. 2018; 40(4):1927-1936 [PubMed] Free Access to Full Article Related Publications
Beclin1 is an important autophagy‑related prot-ein, which is involved in both autophagy and apoptosis. In recent years, the antitumor effect of Beclin1 has received increased attention. In the present study, we established a stable Beclin1‑overexpressing cell line with SW982 human synovial sarcoma cells. We found that Beclin1 overexpression decreased the cell viability, inhibited proliferation and induced apoptosis in SW982 cells. The expression levels of Bcl‑2 and PCNA were decreased, while the levels of cleaved‑caspase‑3 and cleaved‑PARP were increased. Beclin1 is closely related with autophagy, thus the autophagy‑related markers LC3 and p62 were detected by western blot analysis, and transmission electron microscopy was used to observe autophagosomes. The results showed that the expression level of LC3II was increased and that of p62 was decreased. Moreover, many double membrane‑enclosed autophagosomes were found in cells with Beclin1 overexpression, which indicated that the autophagic activity was enhanced. To explore the effect of autophagy on the viability of SW982 cells, Atg5 was knocked down using siRNA to inhibit the autophagic activity. We found that autophagy contributed to the decrease in cell viability. Knockdown of Atg5 increased the viability and decreased the apoptotic rate of SW982 cells with Beclin1 overexpression. The expression level of Bcl‑2 was increased, while the expression levels of cleaved‑caspase‑3 and cleaved‑PARP were decreased. We also found that the Akt/Bcl‑2/caspase‑9 pathway was involved. The phosphorylation of AKT was positively correlated with cell viability. The cleavage of caspase‑9 was increased by Beclin1 overexpression and decreased by inhibition of autophagy. Altogether, our results suggested that both autophagy and apoptosis contributed to the antitumor effect of Beclin1 in SW982 cells.

Liu M, Qi Y, Zhao L, et al.
Matrix metalloproteinase-14 induces epithelial-to-mesenchymal transition in synovial sarcoma.
Hum Pathol. 2018; 80:201-209 [PubMed] Related Publications
Synovial sarcoma (SS) is a highly aggressive malignant soft tissue sarcoma with typical characteristics of both epithelial and mesenchymal differentiation. Matrix metalloproteinase-14 (MMP-14) is reported to play an important role in some of these tumors. It induces epithelial-to-mesenchymal transition (EMT) in some carcinomas, such as breast and prostate cancers. However, the role of MMP-14 in the pathogenesis of SS remains unclear. Therefore, we investigated the role of MMP-14 and EMT/mesenchymal-to-epithelial transition in SS. The expression of MMP-14 and EMT-related proteins was determined in 37 SS cases and transfected cells by immunohistochemistry staining and Western blotting. The invasion ability of transfected cells was determined by transwell invasion assay. The expression rates of MMP-14, E-cadherin, N-cadherin, and vimentin were 75.7%, 54.1%, 75.7%, and 100%, respectively, in the cases of SS. The expression of MMP-14 correlated negatively with E-cadherin and positively with N-cadherin in monophasic fibrous SS. The MMP-14 protein expression was higher in stage III/IV than in stage I/II. After MMP-14 was transfected into SW982 cells, MMP-14, N-cadherin, and vimentin expression was up-regulated, and E-cadherin expression was down-regulated. High expression of MMP-14 enhanced the invasive ability of SW982 cells. Our findings suggest that MMP-14 enhances the invasive ability of SW982 cells by inducing EMT. By this action, it may play an important role in the occurrence and development of SS.

Panigrahi MK, Pradhan G, Sahoo N, et al.
Primary pulmonary synovial sarcoma: A reappraisal.
J Cancer Res Ther. 2018 Apr-Jun; 14(3):481-489 [PubMed] Related Publications
Synovial sarcoma (SS) is a malignant mesenchymal tumor with variable epithelial differentiation that affects mostly young adults and can arise at any anatomic site. Primary intrathoracic SS is very rare accounting for <0.5% of all lung tumors. Most commonly, it arises from the lung followed by pleura and mediastinum. Primary pulmonary SS (PPSS) affects both sexes equally with no preference for any hemithorax. The morphology, immunostaining properties, cytogenetic features, and management strategy of PPSS are similar to that of soft tissue SS. Histologically, there are two main types of SS - monophasic and biphasic with a feature of poor differentiation seen in both types. Most patients present with large intrathoracic masses with or without ipsilateral pleural effusion. Bone invasion or mediastinal adenopathy is very rare. SS is characterized by a specific chromosomal translocation producing SS18-SSX fusion gene in more than 90% of cases. Identification of this fusion gene remains the gold standard for the diagnosis in the presence of consistent histology and immunophenotype. Multimodality treatment including wide excision, chemotherapy, and radiotherapy is the mainstay of therapy. SS is relatively chemosensitive, and ifosfamide-based regimen showed improved survival in metastatic disease. Generally, SS is considered as high-grade tumors with a poor prognosis. Novel therapies targeted at fusion oncogene, SS18-SSX-derived peptide vaccine, epidermal growth factor receptor, and vascular endothelial growth factor are the future hope in SS. We describe a prototype case and present an elaborate review on primary SS of lung.

McBride MJ, Pulice JL, Beird HC, et al.
The SS18-SSX Fusion Oncoprotein Hijacks BAF Complex Targeting and Function to Drive Synovial Sarcoma.
Cancer Cell. 2018; 33(6):1128-1141.e7 [PubMed] Related Publications
Synovial sarcoma (SS) is defined by the hallmark SS18-SSX fusion oncoprotein, which renders BAF complexes aberrant in two manners: gain of SSX to the SS18 subunit and concomitant loss of BAF47 subunit assembly. Here we demonstrate that SS18-SSX globally hijacks BAF complexes on chromatin to activate an SS transcriptional signature that we define using primary tumors and cell lines. Specifically, SS18-SSX retargets BAF complexes from enhancers to broad polycomb domains to oppose PRC2-mediated repression and activate bivalent genes. Upon suppression of SS18-SSX, reassembly of BAF47 restores enhancer activation, but is not required for proliferative arrest. These results establish a global hijacking mechanism for SS18-SSX on chromatin, and define the distinct contributions of two concurrent BAF complex perturbations.

Zayed H, Petersen I
Stem cell transcription factor SOX2 in synovial sarcoma and other soft tissue tumors.
Pathol Res Pract. 2018; 214(7):1000-1007 [PubMed] Related Publications
BACKGROUND: SOX2 has gained considerable interest as a pluripotency inducing gene. Co-transfection of SOX2 together with NANOG, KLF4 and c-MYC into adult fibroblasts was able to generate pluripotent stem cells. SOX2 has been reported to be expressed in synovial sarcoma, a tumor being characterized by the SS18-SSX gene fusion forming part of the SWI/SNF chromatin remodeling complex that affects histone methylation. The role of SOX2 in this tumor type as well as other soft tissue tumor entities however is still poorly characterized. We analyzed SOX2 protein expression in soft tissue tumors. Alongside we tested Histone H3 expression (H3K27me3) in SOX2 positive cases to investigate this epigenetic mark and its correlation with the SOX2 status and clinicopathological parameters.
METHODOLOGY: In total, 60 samples of synovial sarcomas from the reference center for soft tissue tumors at the institute of pathology of the Jena University hospital were included into the study along with 343 other tissue tumors. Protein analysis was done by immunohistochemistry of tissue microarrays. All synovial sarcoma cases were confirmed by molecular testing using SS18 FISH break apart probes.
RESULTS: SOX2 reactivity was detectable in 35 synovial sarcoma cases (58.3%) while 25 (41.7%) were negative. Only 13 cases of the other 343 soft tissue tumors, varying from nodular fasciitis to undifferentiated pleomorphic sarcoma, revealed a SOX2 expression, 12 out of these were undifferentiated high grade sarcoma. There was no obvious correlation with the clinicopathological data. H3K27me3 immunohistochemistry of the synovial sarcoma cases revealed a high statistically significant correlation between SOX2 and H3K27me3 expression (p < 0,0005, Chi square test). Similar to SOX2, there was no correlation between H3K27me3 expression and tumor grade. Six SOX2 positive synovial sarcoma cases were analyzed by FISH using a SOX2/CEN3 dual color FISH probe. None of these cases revealed an amplification of the SOX2 gene.
CONCLUSION: The data confirms previous studies reporting SOX2 and H3K27me3 expression in synovial sarcoma and reveals that both biomarkers are related to each other. It strengthens the notion that the tumor type is driven by epigenetic processes similar to those that are operating in pluripotent stem cells. The relevance of these parameters in the pathway pathology of synovial sarcoma, i.e. the timing and dosing of SOX2 and H3K27me3 expression initiated by the SS18-SSX driver mutation together with the interplay of these events with other signaling pathways, cellular mechanisms and additional mutations in tumor progression, will require further studies.

Suzuki T, Muraki Y, Hatano N, et al.
PIEZO1 Channel Is a Potential Regulator of Synovial Sarcoma Cell-Viability.
Int J Mol Sci. 2018; 19(5) [PubMed] Free Access to Full Article Related Publications
Detection of mechanical stress is essential for diverse biological functions including touch, audition, and maintenance of vascular myogenic tone. PIEZO1, a mechano-sensing cation channel, is widely expressed in neuronal and non-neuronal cells and is expected to be involved in important biological functions. Here, we examined the possibility that PIEZO1 is involved in the regulation of synovial sarcoma cell-viability. Application of a PIEZO1 agonist Yoda1 effectively induced Ca

Alegría-Landa V, Nájera L, Massa DS, et al.
Primary Subcutaneous Synovial Sarcoma: First Reported Subcutaneous Case Showing TLE1 Immunoreactivity.
Am J Dermatopathol. 2018; 40(10):772-777 [PubMed] Related Publications
Synovial sarcoma (SS) accounts for 5%-10% of all soft tissue sarcomas. It is a well-defined soft tissue neoplasm with biphasic and monophasic histologic subtypes and unknown histogenesis. It usually occurs in the extremities, especially the thigh-knee region of young adults. Recurrences are frequent and distant metastasis developed in approximately half of the patients. SSs are characterized by a recurrent nonrandom chromosomal translocation, t(X; 18) (p11; q11), which is considered the primary genetic event in more than 90% of cases. Only 4 cases of cutaneous and subcutaneous SSs have been published in the literature so far. We report a case of primary subcutaneous SS in the forearm of a young woman and discuss the histopathologic differential diagnosis with other similar neoplasms. This is the first reported case of primary cutaneous SS showing immunoreactivity for TLE1 in the nuclei of neoplastic cells, supporting the use of this marker for diagnosis of this rare cutaneous neoplasm.

Oyama R, Kito F, Sakumoto M, et al.
Establishment and proteomic characterization of a novel synovial sarcoma cell line, NCC-SS2-C1.
In Vitro Cell Dev Biol Anim. 2018; 54(5):392-399 [PubMed] Related Publications
Synovial sarcoma is an aggressive mesenchymal tumor, characterized by the presence of unique transfusion gene, SS18-SSX. Cell lines enable researchers to investigate the molecular backgrounds of disease and the significance of SS18-SSX in relevant cellular contexts. We report the establishment and proteomic characterization of a novel synovial sarcoma cell line. Primary tissue culture was performed using tumor tissue of synovial sarcoma. The established cell line was authenticated by assessing its DNA microsatellite short tandem repeat analysis and characterized by in vitro assay. Proteomic study was achieved by mass spectrometry, and the results were analyzed by treemap. The cell line NCC-SS2-C1 was established from a primary tumor tissue of a synovial sarcoma patient. The cell line has grown well for 11 mo and has been subcultured more than 15 times. The established cells were authenticated by assessing their short tandem repeat pattern comparing with that of original tumor tissue. The cells showed polygonal in shape and formed spheroid when seeded on the low-attachment dish. Proteomic analysis revealed the molecular pathways which are unique to the original tumor tissue or the established cell line. In conclusion, a novel synovial sarcoma cell line NCC-SS2-C1 was successfully established from the primary tumor tissue. The cell line has characteristic transfusion SS18-SSX and poses aggressive in vitro growth and capability of spheroid formation. Thus, NCC-SS2-C1 cell line will be a useful tool for investigation of the mechanisms of disease and the biological role of fusion gene.

Terra SBSP, Aesif SW, Maleszewski JJ, et al.
Mediastinal Synovial Sarcoma: Clinicopathologic Analysis of 21 Cases With Molecular Confirmation.
Am J Surg Pathol. 2018; 42(6):761-766 [PubMed] Related Publications
Synovial sarcoma (SS), a translocation-associated sarcoma characterized by SS18-SSX1/2 fusion, presents most often in the extremities of young adults. While SS regularly occurs in the pleuropulmonary parenchyma, the mediastinum is an exceedingly rare primary site; the literature on this subject is predominantly composed of case reports and small series, mostly without molecular confirmation. Cases of mediastinal SS were selected from our institutional and consultation archives. Diagnoses were confirmed by either SS18 fluorescence in situ hybridization (n=6) or reverse transcription polymerase chain reaction for SS18-SSX1/2 (n=15). Mediastinal SSs occurred in 21 patients (15 men; mean age, 38 y; range, 21 to 75). Only 1 patient was older than 50 years. Average tumor size was 13.5 cm (range: 6.4 to 23 cm). One tumor was biphasic and the rest were monophasic, 11 of which were poorly differentiated (52%). Of 10 cases with known fusion transcripts, 6 had SS18-SSX2 and 4 had SS18-SSX1. Follow-up was known for 16 patients (mean: 18.9 mo; range: 5 to 45): 14 had local disease progression or recurrence, and 6 had metastasis. Death from disease occurred in 11 of 16 patients (69%) at 5 to 32 months, and 5 (36%) were alive with disease at last follow-up (6 to 45 mo). Mediastinal SS is a rare and aggressive malignancy most common in patients younger than 50 years. Most are monophasic and reach large size before detection. Poorly differentiated morphology is common. SS should be included in the differential diagnosis of spindle cell, biphasic and poorly differentiated mediastinal tumors. Because of the rarity of SS at this site, molecular testing is recommended to confirm the diagnosis.

Orbach D, Mosseri V, Pissaloux D, et al.
Genomic complexity in pediatric synovial sarcomas (Synobio study): the European pediatric soft tissue sarcoma group (EpSSG) experience.
Cancer Med. 2018; 7(4):1384-1393 [PubMed] Free Access to Full Article Related Publications
A genomic index (GI) tool using array comparative genomic hybridization (aCGH) on tumor cells has emerged as independent prognostic factor associated with the risk of metastatic relapse in synovial sarcoma (SS). The aim was to assess GI in pediatric patients with SS, to determine its value as a prognostic factor. All pediatric/adolescent/young adults' (<25 years) with localized SS prospectively included in the European EpSSG-NRSTS05 protocol with a contributive aCGH were selected. Definition of GI was A

Banito A, Li X, Laporte AN, et al.
The SS18-SSX Oncoprotein Hijacks KDM2B-PRC1.1 to Drive Synovial Sarcoma.
Cancer Cell. 2018; 33(3):527-541.e8 [PubMed] Free Access to Full Article Related Publications
Synovial sarcoma is an aggressive cancer invariably associated with a chromosomal translocation involving genes encoding the SWI-SNF complex component SS18 and an SSX (SSX1 or SSX2) transcriptional repressor. Using functional genomics, we identify KDM2B, a histone demethylase and component of a non-canonical polycomb repressive complex 1 (PRC1.1), as selectively required for sustaining synovial sarcoma cell transformation. SS18-SSX1 physically interacts with PRC1.1 and co-associates with SWI/SNF and KDM2B complexes on unmethylated CpG islands. Via KDM2B, SS18-SSX1 binds and aberrantly activates expression of developmentally regulated genes otherwise targets of polycomb-mediated repression, which is restored upon KDM2B depletion, leading to irreversible mesenchymal differentiation. Thus, SS18-SSX1 deregulates developmental programs to drive transformation by hijacking a transcriptional repressive complex to aberrantly activate gene expression.

Ogino S, Konishi H, Ichikawa D, et al.
Detection of fusion gene in cell-free DNA of a gastric synovial sarcoma.
World J Gastroenterol. 2018; 24(8):949-956 [PubMed] Free Access to Full Article Related Publications
Synovial sarcoma (SS) is genetically characterized by chromosomal translocation, which generates

Kito F, Oyama R, Takai Y, et al.
Establishment and characterization of the NCC-SS1-C1 synovial sarcoma cell line.
Hum Cell. 2018; 31(2):167-174 [PubMed] Related Publications
Synovial sarcoma is an aggressive mesenchymal malignancy characterized by unique gene fusions. Tissue culture cells are essential tools for further understanding tumorigenesis and anti-cancer drug development; however, only a limited number of well-characterized synovial sarcoma cell lines exist. Thus, the objective of this study was to establish a patient-derived synovial sarcoma cell line. We established a synovial sarcoma cell line from tumor tissue isolated from a 72-year-old female patient. Prepared cells were analyzed for the presence of gene fusions by fluorescence in situ hybridization, RT-PCR, and karyotyping. In addition, the resulting cell line was characterized by viability, short tandem repeat, colony and spheroid formation, and invasion analyses. Differences in gene enrichment between the primary tumor and cell line were examined by mass spectrometric protein expression profiling and KEGG pathway analysis. Our analyses revealed that the primary tumor and NCC-SS1-C1 cell line harbored the SS18-SSX1 fusion gene typical of synovial sarcoma and similar proteomics profiles. In vitro analyses also confirmed that the established cell line harbored invasive, colony-forming, and spheroid-forming potentials. Moreover, drug screening with chemotherapeutic agents and tyrosine kinase inhibitors revealed that doxorubicin, a subset of tyrosine kinase inhibitors, and several molecular targeting drugs markedly decreased NCC-SS1-C1 cell viability. Results from the present study support that the NCC-SS1-C1 cell line will be an effective tool for sarcoma research.

Herrera-Goepfert R
Postradiation Synovial Sarcoma of the Common Bile Duct: A Previously Unreported Anatomic Site.
Int J Surg Pathol. 2018; 26(5):469-474 [PubMed] Related Publications
Synovial sarcoma is a ubiquitous neoplasm predominantly affecting soft tissues of young adults of any gender; few cases have been described in the digestive system, mostly in the stomach. The (X;18)(p11.2; q11.2) translocation yields unique SS18-SSX fusion genes. Synovial sarcoma has been related to radiotherapy, but no synovial sarcoma has been associated with the digestive system. This article describes the case of a synovial sarcoma arising along the extrahepatic biliary tree, 10 years after the application of an abdominal radiotherapy schedule due to a retroperitoneal metastatic seminoma in a male who developed progressive obstructive jaundice. Ninety percent of the analyzed cells carried the SS18 gene with separation of sequences, thus denoting a translocation. There are only 8 post-radiotherapy synovial sarcomas that have been reported previously, and this is the first report of a radiotherapy-related synovial sarcoma arising from the extrahepatic biliary tree, and the second case described in this anatomic region.

Stacchiotti S, Van Tine BA
Synovial Sarcoma: Current Concepts and Future Perspectives.
J Clin Oncol. 2018; 36(2):180-187 [PubMed] Related Publications
Synovial sarcoma (SS) is a rare sarcoma driven by a translocation between SS18 and SSX 1, 2, or 4. With approximately 800 to 1,000 cases a year in the United States, it most commonly affects young adults between the ages of 15 and 30 years. The resultant tumors are either monophasic (pure sarcomas), biphasic (a combination or epithelioid and sarcomatous components), or poorly differentiated. The hybrid transcription factor SS18:SSX alters SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling and global methylation patterns that may allow for future therapeutic opportunities. In this review, we focus on the pharmacologic management of SS, both in the curative setting, where the standard approach is wide surgical excision combined with radiotherapy and/or (neo)adjuvant chemotherapy as appropriate, and in the palliative setting. In advanced disease, chemotherapy with anthracyclines and/or ifosfamide, trabectedin, or pazopanib has been demonstrated to be more active compared with other soft tissue sarcomas. In addition, a better understanding of the molecular and immunologic characteristics of SS has allowed for the identification of new potential targets and the development of novel biology-driven therapies that are all at different stages of testing. There include targeted agents, immunotherapy, and metabolic therapies. Because the impact of these strategies for improving SS outcome is still limited, current and future research is strongly needed to better understand the tumor biology, to identify predictive biomarkers, and to improve the outcomes for patients with SS.

Barrott JJ, Illum BE, Jin H, et al.
Paracrine osteoprotegerin and β-catenin stabilization support synovial sarcomagenesis in periosteal cells.
J Clin Invest. 2018; 128(1):207-218 [PubMed] Free Access to Full Article Related Publications
Synovial sarcoma (SS) is an aggressive soft-tissue sarcoma that is often discovered during adolescence and young adulthood. Despite the name, synovial sarcoma does not typically arise from a synoviocyte but instead arises in close proximity to bones. Previous work demonstrated that mice expressing the characteristic SS18-SSX fusion oncogene in myogenic factor 5-expressing (Myf5-expressing) cells develop fully penetrant sarcomagenesis, suggesting skeletal muscle progenitor cell origin. However, Myf5 is not restricted to committed myoblasts in embryos but is also expressed in multipotent mesenchymal progenitors. Here, we demonstrated that human SS and mouse tumors arising from SS18-SSX expression in the embryonic, but not postnatal, Myf5 lineage share an anatomic location that is frequently adjacent to bone. Additionally, we showed that SS can originate from periosteal cells expressing SS18-SSX alone and from preosteoblasts expressing the fusion oncogene accompanied by the added stabilization of β-catenin, which is a common secondary change in SS. Expression and secretion of the osteoclastogenesis inhibitory factor osteoprotegerin enabled early growth of SS18-SSX2-transformed cells, indicating a paracrine link between the bone and synovial sarcomagenesis. These findings explain the skeletal contact frequently observed in human SS and may provide alternate means of enabling SS18-SSX-driven oncogenesis in cells as differentiated as preosteoblasts.

Uotani K, Fujiwara T, Yoshida A, et al.
Circulating MicroRNA-92b-3p as a Novel Biomarker for Monitoring of Synovial Sarcoma.
Sci Rep. 2017; 7(1):14634 [PubMed] Free Access to Full Article Related Publications
The lack of useful biomarkers is a crucial problem for patients with soft tissue sarcomas (STSs). Emerging evidence has suggested that circulating microRNAs (miRNAs) in body fluids have novel impact as biomarkers for patients with malignant diseases, but their significance in synovial sarcoma (SS) patients remains unknown. Initial global miRNA screening using SS patient serum and SS cell culture media identified a signature of four upregulated miRNAs. Among these candidates, miR-92b-3p secretion from SS cells was confirmed, which was embedded within tumour-derived exosomes rather than argonaute-2. Animal experiments revealed a close correlation between serum miR-92b-3p levels and tumour dynamics. Clinical relevance was validated in two independent clinical cohorts, and we subsequently identified that serum miR-92b-3p levels were significantly higher in SS patients in comparison to that in healthy individuals. Moreover, serum miR-92b-3p was robust in discriminating patients with SS from the other STS patients and reflected tumour burden in SS patients. Overall, liquid biopsy using serum miR-92b-3p expression levels may represent a novel approach for monitoring tumour dynamics of SS.

Zhang W, Xue X, Fu T
Construction of a Bcl-2-shRNA expression vector and its effect on the mitochondrial apoptosis pathway in SW982 cells.
Int J Mol Med. 2017; 40(6):1914-1920 [PubMed] Related Publications
Apoptosis is considered to serve an important role in the pathogenesis of rheumatoid arthritis. The aim of the present study was to construct Bcl-2-short hairpin (sh)RNA expression vectors and transfect them into human synovial sarcoma SW982 cells, in order to screen for an effective interference sequence and analyze the effects of this interference on the expression levels of Bcl-2 and other molecules associated with the mitochondrial apoptosis pathway. Three different shRNAs (Bcl-2-sh1, 2 and 3) were designed according to the human Bcl-2 mRNA target sequence and were transformed into competent DH5α Escherichia coli cells following the construction of an expression vector, which was then transfected into SW982 cells. SW982 cells were grouped into a control group (transfected with a negative control shRNA), and Bcl-2-sh1, Bcl-2-sh2 and Bcl-2-sh3 groups (transfected with Bcl-2-sh1, 2 and 3, respectively). The expression levels of Bcl-2 mRNA were detected using reverse transcription-quantitative PCR (RT-qPCR). Bcl-2-sh1 was identified as the most effective shRNA sequence for interference, and was used for subsequent experiments. The mRNA and protein expression levels of Bcl-2, Bax, CytC and Caspase-3 were detected in SW982 cells by RT-qPCR and western blotting at various time-points (48 and 72 h) following transfection with Bcl-2-sh1, in order to observe the effectiveness of this interference. Compared with the control group, the expression levels of Bcl-2 were decreased, while those of Bax, CytC and Caspase-3 were increased in Bcl-2-sh1-transfected cells (P<0.01). The interference effect was greater at 48 h than at 72 h. In summary, an effective shRNA sequence (Bcl-2-sh1) targeting the Bcl-2 gene was identified from three candidates, and was demonstrated to significantly interfere with the expression of Bcl-2, Bax, CytC and Caspase-3 when transfected into SW982 cells. The interference effect of Bcl-2-sh1 was more pronounced at 48 h than at 72 h post-transfection.

Jones SE, Fleuren EDG, Frankum J, et al.
ATR Is a Therapeutic Target in Synovial Sarcoma.
Cancer Res. 2017; 77(24):7014-7026 [PubMed] Free Access to Full Article Related Publications
Synovial sarcoma (SS) is an aggressive soft-tissue malignancy characterized by expression of SS18-SSX fusions, where treatment options are limited. To identify therapeutically actionable genetic dependencies in SS, we performed a series of parallel, high-throughput small interfering RNA (siRNA) screens and compared genetic dependencies in SS tumor cells with those in >130 non-SS tumor cell lines. This approach revealed a reliance of SS tumor cells upon the DNA damage response serine/threonine protein kinase ATR. Clinical ATR inhibitors (ATRi) elicited a synthetic lethal effect in SS tumor cells and impaired growth of SS patient-derived xenografts. Oncogenic SS18-SSX family fusion genes are known to alter the composition of the BAF chromatin-remodeling complex, causing ejection and degradation of wild-type SS18 and the tumor suppressor SMARCB1. Expression of oncogenic SS18-SSX fusion proteins caused profound ATRi sensitivity and a reduction in SS18 and SMARCB1 protein levels, but an SSX18-SSX1 Δ71-78 fusion containing a C-terminal deletion did not. ATRi sensitivity in SS was characterized by an increase in biomarkers of replication fork stress (increased γH2AX, decreased replication fork speed, and increased R-loops), an apoptotic response, and a dependence upon cyclin E expression. Combinations of cisplatin or PARP inhibitors enhanced the antitumor cell effect of ATRi, suggesting that either single-agent ATRi or combination therapy involving ATRi might be further assessed as candidate approaches for SS treatment.

Barrott JJ, Zhu JF, Smith-Fry K, et al.
The Influential Role of BCL2 Family Members in Synovial Sarcomagenesis.
Mol Cancer Res. 2017; 15(12):1733-1740 [PubMed] Free Access to Full Article Related Publications
Synovial sarcomas are deadly soft tissue malignancies associated with t(X;18) balanced chromosomal translocations. Expression of the apoptotic regulator BCL2 is prominent in synovial sarcomas and has prompted the hypothesis that synovial sarcomagenesis may depend on it. Herein, it is demonstrated that

Tapia Rico G, Klevansky M, Townsend A, Price T
Synovial metastasis of the knee in a
BMJ Case Rep. 2017; 2017 [PubMed] Free Access to Full Article Related Publications
Synovial metastasis is an unusual entity in solid tumours and only a few cases have been reported in the literature. We report a case of synovial metastasis of the knee in a young patient with progressive rectal adenocarcinoma and review previously published case reports of synovial involvement in advanced colorectal carcinomas. Synovial metastasis is just one of the multiple possibilities of differential diagnosis in patients with cancer suffering from monarthritis. Radiological tests (plain radiographs, bone scans, MRI of the joint and so forth) can be unspecific and cytological examination of the synovial fluid and/or histology of synovial biopsies is essential for a definitive diagnosis so as to tailor the best treatment for patients. Given the poor prognosis associated with these intra-articular secondaries, treatment is often limited to palliation.

Jiang D, Peng R, Yan X, et al.
Synovial sarcoma showing loss of a green signal in SS18 fluorescence in situ hybridization: a clinicopathological and molecular study of 12 cases.
Virchows Arch. 2017; 471(6):799-807 [PubMed] Related Publications
The phenomenon of losing a green signal in synovial sarcoma (SS) using the SS18 break-apart probe by fluorescence in situ hybridization (FISH) has been poorly described. In this study, 12 SS with missing a green signal were identified. This series included 7 males and 5 females, aged 17 to 69 years (median, 38.5 years). The tumors involved the extremities (50%), mediastinum (16.7%), hypopharynx (8.3%), neck (8.3%), thyroid (8.3%), and retroperitoneum (8.3%). The tumors were classified as monophasic SS (58.3%) and poorly differentiated SS (41.7%). An anaplastic SS showing features of pleomorphic sarcoma was observed. Immunostaining for TLE1, BCL2, CD99, epithelial membrane antigen, cytokeratin (AE1/AE3), cytokeratin 7, S-100 protein, and CD34 was consistent with typical SS. In FISH, all the tumors showed the pattern of 1 to 3 fused signal(s) with 1 to 3 red signal(s), without corresponding a green signal. The fusion transcripts included SS18-SSX1 (8/10, 80%) and SS18-SSX2 (2/10, 20%) fusions. Median and 5-year overall survival were 19.1 months and 43.6%, respectively. In conclusion, we reported a series of SS losing a green signal in the SS18 FISH assay. We propose that this variant FISH pattern should be interpreted as a peculiar unbalanced rearrangement of the SS18 gene and subsequent SS18-SSX fusion test should be recommended. The cases in this study seem to show some unusual clinicopathological features, including unusual locations, higher proportions of poorly differentiated SS, and aggressive clinical course. However, whether this variant FISH pattern is associated with peculiar clinicopathologic features awaits larger series.

Yalçınkaya U, Uğraş N, Özgün G, et al.
Enhancer of zeste homologue 2 (EZH2) expression in synovial sarcomas as a promising indicator of prognosis.
Bosn J Basic Med Sci. 2017; 17(4):302-308 [PubMed] Free Access to Full Article Related Publications
Synovial sarcoma (SS) is a type of soft-tissue sarcoma, often linked to poor survival. Although overexpression of enhancer of zeste homologue 2 (EZH2) has been associated with poor prognosis in different tumors, a few studies investigated this link in SS. Here, we analyzed the relationship between EZH2 expression and prognostic factors in SS. We included 29 patients with SS. Immunostaining of EZH2 was performed with (D2C9) XPTM Rabbit mAb antibody, and the results were classified as low EZH2 expression (negative or weak expression) and high EZH2 expression category (moderate or strong expression). Analysis of survival in relation to prognostic factors was performed with Kaplan-Meier survival curves and Cox proportional hazard regression analysis. Our sample included 19/29 female and 10/29 male patients, with age range 16-63 years. The tumor diameter ranged from 2 to 15 cm. Necrosis was observed in 15/29 cases. Sixteen cases had >10 mitoses per 50 high-power fields (HPFs). Out of 29 cases, 14 showed low and 15 had high EZH2 expression. Statistically significant results were obtained for the association between the presence of metastasis and necrosis (p = 0.042), high EZH2 expression and distant metastasis (p = 0.018), high EZH2 expression and necrosis (p = 0.016), and high EZH2 expression and the tumor size >5 cm versus tumor size ≤5 cm (p = 0.014). Patients with all of the following: the tumor size ≤5 cm, low EZH2 expression, and without necrosis and distant metastasis had significantly longer survival time. Our results are consistent with previous studies, suggesting that EZH2 overexpression is an indicator of poor prognosis in SS.

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