Gene Summary

Gene:SSX2; SSX family member 2
Aliases: SSX, HD21, CT5.2, CT5.2A, HOM-MEL-40
Summary:The product of this gene belongs to the family of highly homologous synovial sarcoma X (SSX) breakpoint proteins. These proteins may function as transcriptional repressors. They are also capable of eliciting spontaneous humoral and cellular immune responses in cancer patients, and are potentially useful targets in cancer vaccine-based immunotherapy. This gene, and also the SSX1 and SSX4 family members, have been involved in t(X;18)(p11.2;q11.2) translocations that are characteristically found in all synovial sarcomas. This translocation results in the fusion of the synovial sarcoma translocation gene on chromosome 18 to one of the SSX genes on chromosome X. The encoded hybrid proteins are likely responsible for transforming activity. Alternative splicing of this gene results in multiple transcript variants. This gene also has an identical duplicate, GeneID: 727837, located about 45 kb downstream in the opposite orientation on chromosome X. [provided by RefSeq, Jul 2013]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:protein SSX2
Source:NCBIAccessed: 29 August, 2019


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 29 August 2019 using data from PubMed using criteria.

Literature Analysis

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

  • Biomarkers, Tumor
  • Vimentin
  • X Chromosome
  • Stromal Cells
  • Gene Expression Profiling
  • Young Adult
  • Cancer Gene Expression Regulation
  • Repressor Proteins
  • Lung Cancer
  • Testis
  • Transcription Factors
  • Chromosome X
  • Serologic Tests
  • Paraffin Embedding
  • Immunohistochemistry
  • Proteins
  • Tumor Antigens
  • Messenger RNA
  • FISH
  • Cell Differentiation
  • DNA Primers
  • BCL2 protein
  • Molecular Sequence Data
  • Base Sequence
  • Cell Nucleus
  • Proto-Oncogene Proteins
  • Oncogene Fusion Proteins
  • Differential Diagnosis
  • Two-Hybrid System Techniques
  • Cancer RNA
  • Adolescents
  • Neoplasm Proteins
  • Chromosome 18
  • SS18
  • Kidney Cancer
  • Polymerase Chain Reaction
  • Synovial Sarcoma
  • Gene Expression
  • Childhood Cancer
  • Amino Acid Sequence
Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (1)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Entity Topic PubMed Papers
Synovial Sarcomat(X;18)(p11.2;q11.2) SS18-SSX2 in Synovial Sarcoma
A SYT-SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is characteristic nearly all synovial sarcomas. This translocation fuses the SS18 (SYT) gene from chromosome 18 to one of three homologous genes at Xp11: SSX1, SSX2 or SSX4.

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

Latest Publications: SSX2 (cancer-related)

Pei J, Zhao X, Patchefsky AS, et al.
Clinical application of RNA sequencing in sarcoma diagnosis: An institutional experience.
Medicine (Baltimore). 2019; 98(25):e16031 [PubMed] Free Access to Full Article Related Publications
Accurate diagnoses of sarcoma are sometimes challenging on conventional histomorphology and immunophenotype. Many specific genetic aberrations including chromosomal translocations have been identified in various sarcomas, which can be detected by fluorescence in situ hybridization and polymerase chain reaction analysis. Next-generation sequencing-based RNA sequencing can screen multiple sarcoma-specific chromosome translocations/fusion genes in 1 test, which is especially useful for sarcoma without obvious differentiation. In this report, we utilized RNA sequencing on formalin-fixed paraffin-embedded (FFPE) specimens to investigate the possibility of diagnosing sarcomas by identifying disease-specific fusion genes. Targeted RNA sequencing was performed on 6 sarcoma cases. The expected genetic alterations (clear cell sarcoma/EWSR1-ATF1, Ewing sarcoma/EWSR1-FLI1, myxoid liposarcoma/DDIT3-FUS) in four cases were detected and confirmed by secondary tests. Interestingly, three SS18 fusion genes (SS18-SSX2B, SS18-SSX2, and SS18-SSX4) were identified in a synovial sarcoma case. A rare fusion gene (EWSR1-PATZ1) was identified in a morphologically challenging case; which enabled us to establish the diagnosis of low grade glioneural tumor. In conclusion, RNA sequencing on FFPE specimen is a reliable method in establishing the diagnosis of sarcoma in daily practice.

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.

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.

Natarajan V, Ramanathan P, Gopisetty G, et al.
In silico and in vitro screening of small molecule Inhibitors against SYT-SSX1 fusion protein in synovial sarcoma.
Comput Biol Chem. 2018; 77:36-43 [PubMed] Related Publications
Synovial sarcoma (SS) is characterized by a tumour specific chromosomal translocation t(X;18) (p11;q11) which results in the formation of SYT-SSX1 fusion protein. This fusion protein represents a clear therapeutic target and molecules specifically targeting SYT-SSX1 fusion protein are currently not available. In this study, SYT-SSX1 fusion protein sequence was retrieved from Uniprot and 3D structure was generated using I-TASSER modeling program. A structure based computational screening approach has been employed using Glide docking software to identify potential SYT-SSX1 small molecule inhibitors that bind to the junction region of the fusion protein. The obtained inhibitors were further filtered based on the docking score and ADME/T properties. Ten best fit compounds were chosen for in vitro studies. The anti-proliferative activities of these 10 compounds were screened in Yamato, ASKA (carries SYT-SSX1 fusion protein) and other sarcoma cell lines such as A673, 143B to understand the specificity of inhibition of the chosen compounds. The in vitro activity was compared against HEK293 cell lines. The compound 5-fluoro-3-(1-phenyl-1H-tetraazol-5-yl)-1H-indole (FPTI) was found to be selectively cytotoxic in synovial sarcoma cell lines (Yamato and ASKA) and this compound also showed insignificant anti proliferative activity on other cell lines. Further, target gene expression study confirmed that FPTI treatment down-regulated SYT-SSX1 and modulated its downstream target genes. Cell cycle analysis revealed the involvement of an apoptotic mechanism of cell death. Further experimental validations may elucidate the therapeutic potentials of FPTI against SYT-SSX1 fusion protein.

Vodolazhsky DI, Kutilin DS, Mogushkova KA, Kit OI
Specific Features of Transcription Activity of Cancer-Testis Antigens in Patients with Metastatic and Non-Metastatic Breast Cancer.
Bull Exp Biol Med. 2018; 165(3):382-385 [PubMed] Related Publications
Cancer-testis antigens, effective markers of tissue malignant transformation, are characterized by heterogonous transcription depending on the pathological features of breast cancer. We performed screening of transcription profile of cancer-testis antigens specific for breast tumor tissues in female patients with and without regional metastasis. The relative expression of 16 genes (MAGEA1, MAGEA2, MAGEA3, MAGEA4, MAGEB1, MAGEB2, GAGE1, GAGE3, GAGE4, MAGEC1, BAGE, XAGE3, NY-ESO1, SSX2, SYCP1, and PRAME1) was analyzed by RT-qPCR method in biopsy specimens of the mammary gland tissues obtained during surgery from 25 patients. Differential transcription activity of cancer-testis antigens genes was observed in patients with metastatic (enhanced expression of MAGEA2, MAGEB1, and XAGE3 genes) and non-metastatic (enhanced expression of GAGE3 and PRAME1 genes) breast cancer.

Morgan MA, Shilatifard A
Epigenetic ConFUSION: SS18-SSX Fusion Rewires BAF Complex to Activate Bivalent Genes in Synovial Sarcoma.
Cancer Cell. 2018; 33(6):951-953 [PubMed] Related Publications
In this issue of Cancer Cell, McBride and colleagues report that the synovial sarcoma SS18-SSX fusion drives BAF complex recruitment to bivalent domains repressed by PRC2 complex to orchestrate aberrant transcriptional activation. Redistribution of BAF localization is a major driver of synovial sarcoma proliferation and presents a promising therapeutic target.

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.

Fan PW, Huang L, Chang XM, et al.
Human Leukocyte Antigen-A Allele Distribution in Nasopharyngeal Carcinoma Patients Showing Anti-Melanoma-Associated Antigen A or Synovial Sarcoma X-2 T Cell Response in Blood.
Chin Med J (Engl). 2018; 131(11):1289-1295 [PubMed] Free Access to Full Article Related Publications
Background: Development of innovative immunotherapy is imperative to improve the poor survival of the nasopharyngeal carcinoma (NPC) patients. In this study, we evaluated the T cell response to melanoma-associated antigen (MAGE)-A1, MAGE-A3, or synovial sarcoma X-2 (SSX-2) in the peripheral blood of treatment-naive NPC patients. The relationship of responses among the three proteins and the human leukocyte antigen (HLA)-A types were analyzed to provide evidence of designing novel therapy.
Methods: Sixty-one NPC patients admitted into the Tumor Hospital affiliated to the Xinjiang Medical University between March 2015 and July 2016 were enrolled. Mononuclear cells were isolated from the peripheral blood before any treatment. HLA-A alleles were typed with Sanger sequence-based typing technique. The T cell response to the MAGE-A1, MAGE-A3, or SSX-2 was evaluated with the Enzyme-Linked ImmunoSpot assay. Mann-Whitney U-test was used to compare the T cell responses from different groups. Spearman's rank correlation was used to analyze the relationship of T cell responses.
Results: HLA-A*02:01, A*02:07, and A*24:02 were the three most frequent alleles (18.9%, 12.3%, and 11.5%, respectively) among the 22 detected alleles. 31.1%, 19.7%, and 16.4% of the patients displayed MAGE-A1, MAGE-A3, or SSX-2-specific T cell response, respectively. The magnitudes of response to the three proteins were 32.5, 38.0, and 28.7 SFC/10
Conclusion: MAGE-A1, MAGE-A3, or SSX-2-specific T cell responses were detectable in a subgroup of NPC patients, the frequency and magnitude of which were correlated.

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.

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.

Przybyl J, Kidzinski L, Hastie T, et al.
Gene expression profiling of low-grade endometrial stromal sarcoma indicates fusion protein-mediated activation of the Wnt signaling pathway.
Gynecol Oncol. 2018; 149(2):388-393 [PubMed] Related Publications
OBJECTIVE: Low-grade endometrial stromal sarcomas (LGESS) harbor chromosomal translocations that affect proteins associated with chromatin remodeling Polycomb Repressive Complex 2 (PRC2), including SUZ12, PHF1 and EPC1. Roughly half of LGESS also demonstrate nuclear accumulation of β-catenin, which is a hallmark of Wnt signaling activation. However, the targets affected by the fusion proteins and the role of Wnt signaling in the pathogenesis of these tumors remain largely unknown.
METHODS: Here we report the results of a meta-analysis of three independent gene expression profiling studies on LGESS and immunohistochemical evaluation of nuclear expression of β-catenin and Lef1 in 112 uterine sarcoma specimens obtained from 20 LGESS and 89 LMS patients.
RESULTS: Our results demonstrate that 143 out of 310 genes overexpressed in LGESS are known to be directly regulated by SUZ12. In addition, our gene expression meta-analysis shows activation of multiple genes implicated in Wnt signaling. We further emphasize the role of the Wnt signaling pathway by demonstrating concordant nuclear expression of β-catenin and Lef1 in 7/16 LGESS.
CONCLUSIONS: Based on our findings, we suggest that LGESS-specific fusion proteins disrupt the repressive function of the PRC2 complex similar to the mechanism seen in synovial sarcoma, where the SS18-SSX fusion proteins disrupt the mSWI/SNF (BAF) chromatin remodeling complex. We propose that these fusion proteins in LGESS contribute to overexpression of Wnt ligands with subsequent activation of Wnt signaling pathway and formation of an active β-catenin/Lef1 transcriptional complex. These observations could lead to novel therapeutic approaches that focus on the Wnt pathway in LGESS.

Waterfall JJ, Meltzer PS
A Non-canonical Polycomb Dependency in Synovial Sarcoma.
Cancer Cell. 2018; 33(3):344-346 [PubMed] Related Publications
Disruptions in the antagonistic balance between the chromatin-modifying Polycomb and Trithorax group proteins drive many malignancies. In this issue of Cancer Cell, Banito et al. describe how the SS18-SSX oncogenic fusion protein in synovial sarcoma directly co-opts these complexes to drive gene dysregulation and sustain the transformed state.

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

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.

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.

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.

Zhou Y, Chen D, Qi Y, et al.
Evaluation of expression of cancer stem cell markers and fusion gene in synovial sarcoma: Insights into histogenesis and pathogenesis.
Oncol Rep. 2017; 37(6):3351-3360 [PubMed] Related Publications
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.

Van Tongelen A, Loriot A, De Smet C
Oncogenic roles of DNA hypomethylation through the activation of cancer-germline genes.
Cancer Lett. 2017; 396:130-137 [PubMed] Related Publications
Global loss of DNA methylation is frequently observed in the genome of human tumors. Although this epigenetic alteration is clearly associated with cancer progression, the way it exerts its pro-tumoral effect remains incompletely understood. A remarkable consequence of DNA hypomethylation in tumors is the aberrant activation of "cancer-germline" genes (also known as "cancer-testis" genes), which comprise a diverse group of germline-specific genes that use DNA methylation as a primary mechanism for repression in normal somatic tissues. Here we review the evidence that such cancer-germline genes contribute to key processes of tumor development. Notably, several cancer-germline genes were found to stimulate oncogenic pathways involved in cell proliferation (SSX, DDX43, MAEL, PIWIL1), angiogenesis (DDX53), immortality (BORIS/CTCFL), and metastasis (CT-GABRA3). Others appear to inhibit tumor suppressor pathways, including those controlling growth inhibition signals (MAGEA11, MAGEB2), apoptosis (MAGEA2, MAGEC2), and genome integrity (HORMAD1, NXF2). Cancer-germline genes were also implicated in the regulation of tumor metabolism (MAGEA3/MAGEA6). Together, our survey substantiates the concept that DNA hypomethylation promotes tumorigenesis via transcriptional activation of oncogenes. Importantly, considering their highly restricted pattern of expression, cancer-germline genes may represent valuable targets for the development of anti-cancer therapies with limited side effects.

Owosho AA, Estilo CL, Rosen EB, et al.
A clinicopathologic study on SS18 fusion positive head and neck synovial sarcomas.
Oral Oncol. 2017; 66:46-51 [PubMed] Free Access to Full Article Related Publications
OBJECTIVE: To determine clinicopathologic factors on survival in patients with head and neck synovial sarcoma.
PATIENTS AND METHODS: We retrospectively identified patients with molecularly confirmed synovial sarcomas of the head and neck (SS-HN), either by the presence of SS18-SSX fusion transcript by RT-PCR or SS18 gene rearrangement by FISH, who were managed at our institution over a 20-year period (1996-2015). Kaplan-Meier survival analysis and log-rank test were performed to evaluate variables related to disease specific survival (DSS). Fisher exact test was performed to evaluate variables related to local recurrence.
RESULTS: Thirty-four patients (20 males and 14 females, mean of 31years) with SS18-SSX fusion-positive SS-HN were identified. The parapharyngeal region of the neck was the most common site. The mean tumor size was 4.8cm (0.8-10cm). Two-thirds (n=23) of cases had a monophasic histology. The 2, 5 and 10-year DSS rates were 97%, 79% and 68%. The 5-year DSS rates for the adult/pediatric cohort were 74%/88%. Recurrence showed significant effect on DSS (p=0.021). There was no significant effect on DSS with age, therapy modality, tumor site, surgical margin, tumor size (⩽5cm vs. >5cm) and histopathologic subtype. Tumor site (i.e. skull base/paranasal sinus region) was associated with local recurrence (p=0.003).
CONCLUSION: In our cohort DSS rate was associated with recurrence. Tumors located in the skull base/paranasal sinus region were associated with a higher rate of local recurrence. Thus appropriate selection of high risk patients who can benefit from multimodality therapies might improve survival.

Olofson AM, Linos K
Primary Intraprostatic Synovial Sarcoma.
Arch Pathol Lab Med. 2017; 141(2):301-304 [PubMed] Related Publications
Primary intraprostatic synovial sarcoma is a rare presentation of an otherwise well-studied disease, and it is one of the few primary sarcomas to occur in the prostate. Ancillary diagnostic techniques including immunohistochemistry and molecular genetics are useful to establish a definitive diagnosis. Despite its unorthodox location, it shares histologic and molecular genetic characteristics with tumors found elsewhere in the body. Most notably, the chromosomal translocation t(X;18)(p11;q11) encodes a chimeric transcription-activating protein, SS18-SSX, which has been identified as the primary driver mutation. The SS18-SSX fusion gene provides a consistent and dependable means of establishing a definitive diagnosis via reverse transcription-polymerase chain reaction or fluorescence in situ hybridization. Recent studies have continued to provide insight into the oncogenesis of this disease. The goal of this review is to elaborate on the clinicopathologic characteristics and underline those techniques that best facilitate the diagnosis of primary intraprostatic synovial sarcoma.

Kao YC, Sung YS, Zhang L, et al.
BCOR upregulation in a poorly differentiated synovial sarcoma with SS18L1-SSX1 fusion-A pathologic and molecular pitfall.
Genes Chromosomes Cancer. 2017; 56(4):296-302 [PubMed] Free Access to Full Article Related Publications
The diagnosis of poorly differentiated synovial sarcoma (PD-SS) may be challenging due to overlapping morphologic features with other undifferentiated round cell sarcomas (URCS). Particularly relevant is the histologic overlap and shared BCOR overexpression between a subset of SS and URCS with various BCOR genetic abnormalities. Here, we report a case of PD-SS lacking the canonical SS18-SSX gene fusion, but showing strong BCOR immunoreactivity and BCOR gene abnormalities by FISH, which were misinterpreted as a URCS with BCOR gene rearrangements. The tumor had an unusual clinical presentation arising as an intraneural tumor in the ankle of a 29-year-old female. The tumor displayed a mixture of fascicular spindle cells and undifferentiated round cell components. FISH studies showed no SS18 gene abnormality; however, RNA sequencing identified a fusion transcript involving SS18L1 (a paralog gene of SS18 at 20q13.33) and SSX1. Further FISH testing validated rearrangements in SSX1 and SS18L1 genes, in addition to complex structural abnormalities of the Xp11.22-4 region. This is the second reported SS case harboring an SS18L1-SSX1 alternative fusion variant, similarly occurring in association with a large nerve. The lack of SS18 gene rearrangements by FISH corroborated with the BCOR overexpression at both mRNA and protein level may result in diagnostic pitfalls with URCS with BCOR gene abnormalities. Our results further suggest that BCOR upregulation is emerging as a common downstream pathway for SS with either typical SS18-SSX transcript or with rare fusion variants, such as SS18L1-SSX. © 2017 Wiley Periodicals, Inc.

Wang CH, Xu CC, Jiang JH, et al.
Diagnosis of a rare primary pulmonary synovial sarcoma with endobronchial ultrasound-guided transbronchial needle aspiration.
Thorac Cancer. 2016; 7(6):684-688 [PubMed] Free Access to Full Article Related Publications
Primary pulmonary synovial sarcoma (PPSS) is a rare disease. Diagnosis is made postoperatively following resection of the tumor. We describe the case of a 39-year-old non-smoking woman whose chest imaging revealed a heterogeneous mass (5.4 cm × 4.6 cm), with soft tissue density in the right upper lobe and pleural effusion in the right hemithorax. The tumor was enhanced on a computed tomography scan, in which enlargement of the mediastinal lymph nodes compressing the adjacent superior vena cava was observed. Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) was then performed, which demonstrated PPSS, subsequently confirmed by immunohistochemistry and the detection of a SYT-SSX fusion gene. We believe that a diagnostic approach of EBUS-TBNA for lung sarcoma would provide helpful information to clinicians.

Heninger E, Krueger TE, Thiede SM, et al.
Inducible expression of cancer-testis antigens in human prostate cancer.
Oncotarget. 2016; 7(51):84359-84374 [PubMed] Free Access to Full Article Related Publications
Immune tolerance to self-antigens can limit robust anti-tumor immune responses in the use of tumor vaccines. Expression of novel tumor associated antigens can improve immune recognition and lysis of tumor cells. The cancer-testis antigen (CTA) family of proteins has been hypothesized to be an ideal class of antigens due to tumor-restricted expression, a subset of which have been found to induce antibody responses in patients with prostate disease. We demonstrate that CTA expression is highly inducible in five different Prostate Cancer (PC) cell lines using a hypomethylating agent 5-Aza-2'-deoxycytidine (5AZA) and/or a histone deacetylase inhibitor LBH589. These CTAs include NY-ESO1, multiple members of the MAGE and SSX families and NY-SAR35. A subset of CTAs is synergistically induced by the combination of 5AZA and LBH589. We developed an ex vivo organ culture using human PC biopsies for ex vivo drug treatments to evaluate these agents in clinical samples. These assays found significant induction of SSX2 in 9/9 distinct patient samples and NY-SAR35 in 7/9 samples. Further, we identify expression of SSX2 in circulating tumor cells (CTC) from patients with advanced PC. These results indicate that epigenetic modifying agents can induce expression of a broad range of neoantigens in human PC and may serve as a useful adjunctive therapy with novel tumor vaccines and checkpoint inhibitors.

He Y, Zhou J, Ma S, et al.
Multi-Responsive "Turn-On" Nanocarriers for Efficient Site-Specific Gene Delivery In Vitro and In Vivo.
Adv Healthc Mater. 2016; 5(21):2799-2812 [PubMed] Related Publications
Systemic gene delivery is a complicated and multistep process that confronts numerous biological barriers. It remains a formidable challenge to exploit a single gene carrier with multiple features to combat all obstacles collectively. Herein, a multi-responsive "turn-on" polyelectrolyte complex (DNA/OEI-SS

Stagner AM, Jakobiec FA, Fay A
Primary orbital synovial sarcoma: A clinicopathologic review with a differential diagnosis and discussion of molecular genetics.
Surv Ophthalmol. 2017 Mar - Apr; 62(2):227-236 [PubMed] Related Publications
Synovial sarcoma is a soft-tissue sarcoma of the extremities developing in young adults that has rarely been reported in the orbit. Synovial sarcoma is associated with a unique translocation, resulting in an SYT-SSX fusion gene. We analyze 7 published periocular cases, together with the current one, to gain a better appreciation of the features of the tumor in this location and to compare the findings with those derived from nonophthalmic studies. An inferior orbital mass developed in a 31-year-old woman after experiencing periorbital and hemifacial pain for more than a decade. Radiographically, the mass was circumscribed and displayed coarse internal calcifications. A large but subtotal excision with histopathologic examination disclosed a primitive tumor composed of spindled and ovoid cells. Immunohistochemistry demonstrated positivity for nuclear transducin-like enhancer of split 1 and membranous CD99, typical for synovial sarcoma. Fluorescence in situ hybridization identified a (X,18) translocation in the tumor cells. The patient underwent postoperative adjuvant proton beam radiotherapy with a good response that has been maintained during 1 year of follow-up. Orbital soft-tissue tumors of all types are increasingly identified by their distinctive genetic signatures that offer more specificity than standard immunohistochemical tests.

Salmaninejad A, Zamani MR, Pourvahedi M, et al.
Cancer/Testis Antigens: Expression, Regulation, Tumor Invasion, and Use in Immunotherapy of Cancers.
Immunol Invest. 2016; 45(7):619-40 [PubMed] Related Publications
UNLABELLED: Cancer/testis antigens (CTAs) are named based on their expression pattern that is restricted in a number of normal and abnormal tissues. Tumor cells frequently express antigens whose expression is typically restricted to germ cells. Their unique expression pattern is guaranteed by precise epigenetic regulatory mechanisms. Because of their tumor-limited, high immunogenicity, and biased expression, discovery of these molecules provides unprecedented opportunities for further research and clinical development in the field of cancer diagnosis and immunotherapy. Evolving evidence reveals that a number of CTAs stimulate epithelial mesenchymal transition (EMT) and generation of cancer stem-like cells, intensifying metastasis, invasion, and tumorigenesis. Based on these features, CTAs attract attention to be considered as ideal targets for developing several clinical trials, many of them concentrating on CTA vaccine therapy. According to recent practical clinical interest, more characterizations of CTA regulation are identified. CTA expression has been demonstrated in a variety of human cancer tissues, and some of them have been found to elicit humoral and/or cellular immune responses in cancer patients. CTAs are brilliant targets for anticancer drug discovery, targeted tumor therapy, and diagnostic biomarkers, furthermore, valued genes in the study of immunotherapy, promoting tumorigenesis, and malignant progression. This review outlines and categorizes our current understanding of the complex and biased process of CTAs mRNA and protein expression in cancer, and supplies the most recent information on their regulation and function. Besides, a concise synopsis of the major clinical trials involving CTAs, as therapeutic avenues, is discussed.
ABBREVIATIONS: AIRE: autoimmune regulator; cAMP: cyclic adenosine 3',5'-cyclic monophosphate; CEA: carcinoembryonic antigen; CML: chronic myeloid leukemia; CREB: cyclicamp response element binding; CSCs: cancer stem cells; CTAs: cancer/testis antigens; CTL: cytotoxic T lymphocyte; DCs: dendritic cells; EMT: epithelial-mesenchymal transition; ERK: extracellular signal-regulated kinase; ESCC: esophageal squamous cell carcinoma; ETS: E26 transformation-specific; His: histidine; HLA: human leukocyte antigen; HNSCC: head and neck squamous cell carcinoma; IFN-γ: interferon-γ; IHC: Immunohistochemistry; IL-7: Interleukin7; MHC: major histocompatibility complex; MMP2: matrix metalloproteinase 2; mTECs: medullary thymus epithelial cells; MUC1: mucin 1; NSCLC: non-small cell lung cancer; PRAME: preferentially expressed antigen in melanoma; RDA: representational difference analysis; SEREX: serological analysis of cDNA expression; SSX: synovial sarcoma X chromosome; TAAs: tumor-associated antigens; TCR: T-cell receptor; TCGA: The Cancer Genome Atlas; TGF-β: transforming growth factor-β.

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