SYT-SSX fusion genes and prognosis in synovial sarcoma

Synovial Sarcoma of the Submaxillary Salivary Gland: A Rare Location and Challenging Diagnosis

Synovial sarcoma is a high-grade sarcoma. The periarticular region, deep soft tissues, and the extremities are where it is most frequently found. The head and neck regions are rarely affected and salivary gland localization is rather rare, especially the submaxillary gland. The process of diagnosis and therapeutic management remains challenging, particularly in cases with uncommon tumor locations where the establishment of a universal therapeutic consensus is complicated. Early diagnosis and a multidisciplinary approach can lead to success without locoregional recurrence or distant metastases.

Synovial Sarcoma: A Complex Disease with Multifaceted Signaling and Epigenetic Landscapes

PURPOSE OF REVIEW

Aside from a characteristic SS18-SSX translocation identified in almost all cases, no genetic anomalies have been reliably isolated yet to drive the pathogenesis of synovial sarcoma. In the following review, we explore the structural units of wild-type SS18 and SSX, particularly as they relate to the transcriptional alterations and cellular pathway changes imposed by SS18-SSX.

RECENT FINDINGS

Native SS18 and SSX contribute recognizable domains to the SS18-SSX chimeric proteins, which inflict transcriptional and epigenetic changes through selective protein interactions involving the SWI/SNF and Polycomb chromatin remodeling complexes. Multiple oncogenic and developmental pathways become altered, collectively reprogramming the cellular origin of synovial sarcoma and promoting its malignant transformation. Synovial sarcoma is characterized by complex epigenetic and signaling landscapes. Identifying the operational pathways and concomitant genetic changes induced by SS18-SSX fusions could help develop tailored therapeutic strategies to ultimately improve disease control and patient survivorship.

Overactive IGF1/Insulin Receptors and NRASQ61R Mutation Drive Mechanisms of Resistance to Pazopanib and Define Rational Combination Strategies to Treat Synovial Sarcoma

Pazopanib is approved for treatment of advanced soft tissue sarcomas, but primary and secondary drug resistance limits its clinical utility. We investigated the molecular mechanisms mediating pazopanib resistance in human synovial sarcoma (SS) models. We found reduced cell sensitivity to pazopanib associated with inefficient inhibition of the two critical signaling nodes, AKT and ERKs, despite strong inhibition of the main drug target, PDGFRα. In the CME-1 cell line, overactivation of IGF1 and Insulin receptors (IGF1R/InsR) sustained AKT activation and pazopanib resistance, which was overcome by a combination treatment with the double IGF1R/InsR inhibitor BMS754807. In the highly pazopanib resistant MoJo cell line, NRASQ61R mutation sustained constitutive ERK activation. Transfection of the NRAS mutant in the pazopanib sensitive SYO-1 cell line increased the drug IC₅₀. MoJo cells treatment with pazopanib in combination with the MEK inhibitor trametinib restored ERK inhibition, synergistically inhibited cell growth, and induced apoptosis. The combination significantly enhanced the antitumor efficacy against MoJo orthotopic xenograft abrogating growth in 38% of mice. These findings identified two different mechanisms of intrinsic pazopanib resistance in SS cells, supporting molecular/immunohistochemical profiling of tumor specimens as a valuable approach to selecting patients who may benefit from rational drug combinations.

In silico and in vitro screening of small molecule Inhibitors against SYT-SSX1 fusion protein in synovial sarcoma

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.

Laser capture microdissection for detecting the expression of epithelial-mesenchymal transition-related genes in epithelial and spindle cells of paraffin-embedded formalin-fixed biphasic synovial sarcoma

Synovial sarcoma (SS) is a mesenchymal malignant neoplasm showing characteristics of epithelial-mesenchymal biphasic differentiation. SS is of uncertain cellular origin; however, studies have suggested that SS originates from a somatic stem cell population. In this study, we aim to determine whether differential morphological features of the epithelial-mesenchymal transition (EMT) contributed to the tumourigenesis of SS invasion and metastasis. Twelve paraffin-embedded formalin-fixed tissue (FFPE) SS tissue specimens were obtained, and laser capture microdissection (LCM) with the ArcturusXT system and small chip method (SCM) were used to isolate and purify spindle and epithelial cells from SS specimens. The TRIzol method was used to extract RNA, and the mRNA levels of EMT-related genes in epithelial and spindle cells of SS specimens were measured using real-time fluorescent quantitative reverse transcription polymerase chain reaction (qRT-PCR). The results show that collection of about 2 × 10⁴ cells from FFPE samples using LCM was sufficient for qRT-PCR, with an efficiency of 75%. Compared with LCM, 72.2% (13 of 18) RNA samples were successfully extracted using SCM to isolate cells from FFPE SS tissues. In the 16 samples (11 spindle cell samples and 5 epithelial cell samples), Snail mRNA was significantly upregulated in spindle cell areas compared with that in epithelial cell areas (P = .001). Expression levels of the epithelial marker E-cadherin and the mesenchymal marker N-cadherin were not significantly different between epithelial and spindle cell areas. In spindle cells of recurrent SS samples, the mRNA levels of E-cadherin, N-cadherin, Snail, and Slug were higher in primary SS samples than in recurrent samples. Taken together, our results indicated that in SS samples, Snail mRNA was upregulated in spindle cell areas compared with that in epithelial cell areas and that the expression of EMT-related genes was increased in primary SS. LCM could be used to isolate and purify RNA from FFPE samples.

Genomic complexity in pediatric synovial sarcomas (Synobio study): the European pediatric soft tissue sarcoma group (EpSSG) experience

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 A² /C, where A is the total number of alterations (segmental gains and losses) and C is the number of involved chromosomes on aCGH results. GI₁ group corresponds to cases with no copy number alterations (flat profile, GI = 0) and GI₂ group cases with at least one or more copy number alterations (rearranged profile; GI ≥ 1). Samples were available from 61 patients. The median age of the cohort was 13 years (range: 4-24). Overall, 55.7% were GI₁ group, and 44.3% GI₂ . After a median follow-up of 62 months (range: 0.1-112), 10 tumor events occurred and five patients died. Respectively, for GI₁ versus GI₂ groups, five-year event-free survival (EFS) was 93.8 ± 4.2% versus 64.9 ± 10.1% (P < 0.006) and five-year Metastatic-Free Survival (MFS) 93.8 ± 4.2% versus 72.9 ± 9.5% (P < 0.04). In multivariate analysis, GI status as adjusted for IRS group, patient age, site, and tumor size remain independent prognostic for EFS with a relative risk (RR) of 6.4 [1.3-31.9] (P < 0.01) and RR for MFS is 4.8 [0.9-25.7] (P < 0.05). Genomic complexity evaluated through GI may explain the metastatic behavior of pediatric SS.

Supersulfated low-molecular weight heparin synergizes with IGF1R/IR inhibitor to suppress synovial sarcoma growth and metastases

Synovial sarcoma (SS) is an aggressive tumor with propensity for lung metastases which significantly impact patients' prognosis. New therapeutic approaches are needed to improve treatment outcome. Targeting the heparanase/heparan sulfate proteoglycan system by heparin derivatives which act as heparanase inhibitors/heparan sulfate mimetics is emerging as a therapeutic approach that can sensitize the tumor response to chemotherapy. We investigated the therapeutic potential of a supersulfated low molecular weight heparin (ssLMWH) in preclinical models of SS. ssLMWH showed a potent anti-heparanase activity, dose-dependently inhibited SS colony growth and cell invasion, and downregulated the activation of receptor tyrosine kinases including IGF1R and IR. The combination of ssLMWH and the IGF1R/IR inhibitor BMS754807 synergistically inhibited proliferation of cells exhibiting IGF1R hyperactivation, also abrogating cell motility and promoting apoptosis in association with PI3K/AKT pathway inhibition. The drug combination strongly enhanced the antitumor effect against the CME-1 model, as compared to single agent treatment, abrogating orthotopic tumor growth and significantly repressing spontaneous lung metastatic dissemination in treated mice. These findings provide a strong preclinical rationale for developing drug regimens combining heparanase inhibitors/HS mimetics with IGF1R antagonists for treatment of metastatic SS.

The prognostic impact of SYT-SSX fusion type and histological grade in pediatric patients with synovial sarcoma treated according to the CWS (Cooperative Weichteilsarkom Studie) trials

BACKGROUND

The aim of our analysis was the evaluation of the prognostic impact of SYT-SSX fusion status and histological grading in synovial sarcoma (SS) of children and adolescents in the context of the consistent multimodal treatment strategy of the CWS (Cooperative Weichteilsarkom Studie; Cooperative Soft Tissue Sarcoma Study Group) and in comparison with other risk factors.

PROCEDURE

Between 1986 and 2006, out of 243 patients with SS, tumor samples from 84 patients with localized disease were available for RT-PCR analysis. Outcome depending on fusion status in the context with known clinical risk factors was analyzed.

RESULTS

No prognostic significance was shown for SYT-SSX fusion status and for histological grade. Highest significance of negative prognostic impact was found for large tumor size in uni- and multivariate analysis (P < 0.01). Furthermore, male gender was shown to be an adverse prognostic factor in multivariate analysis (P = 0.01).

CONCLUSIONS

Based on our results, neither histological grading nor SYT-SSX fusion status seems to be suitable for outcome prediction and risk stratification in localized SS treated according to the CWS. This is in contrast to several other publications concerning more heterogeneous age groups including children and adults, and this indicates that prognostic factors should not be interpreted apart from the particular study population and the therapeutic context.

The impact of chromosomal translocation locus and fusion oncogene coding sequence in synovial sarcomagenesis

Synovial sarcomas are aggressive soft-tissue malignancies that express chromosomal translocation-generated fusion genes, SS18-SSX1 or SS18-SSX2 in most cases. Here, we report a mouse sarcoma model expressing SS18-SSX1, complementing our prior model expressing SS18-SSX2. Exome sequencing identified no recurrent secondary mutations in tumors of either genotype. Most of the few mutations identified in single tumors were present in genes that were minimally or not expressed in any of the tumors. Chromosome 6, either entirely or around the fusion gene expression locus, demonstrated a copy number gain in a majority of tumors of both genotypes. Thus, by fusion oncogene coding sequence alone, SS18-SSX1 and SS18-SSX2 can each drive comparable synovial sarcomagenesis, independent from other genetic drivers. SS18-SSX1 and SS18-SSX2 tumor transcriptomes demonstrated very few consistent differences overall. In direct tumorigenesis comparisons, SS18-SSX2 was slightly more sarcomagenic than SS18-SSX1, but equivalent in its generation of biphasic histologic features. Meta-analysis of human synovial sarcoma patient series identified two tumor-gentoype-phenotype correlations that were not modeled by the mice, namely a scarcity of male hosts and biphasic histologic features among SS18-SSX2 tumors. Re-analysis of human SS18-SSX1 and SS18-SSX2 tumor transcriptomes demonstrated very few consistent differences, but highlighted increased native SSX2 expression in SS18-SSX1 tumors. This suggests that the translocated locus may drive genotype-phenotype differences more than the coding sequence of the fusion gene created. Two possible roles for native SSX2 in synovial sarcomagenesis are explored. Thus, even specific partial failures of mouse genetic modeling can be instructive to human tumor biology.

Prognostic value of SS18-SSX fusion type in synovial sarcoma; systematic review and meta-analysis

SS18-SSX (formerly called SYT-SSX) fusion gene has been established clinically as a molecular diagnostic test for synovial sarcoma, but the prognostic value of the fusion gene variant for survival is controversial. The objective of this systematic review is to provide an up-to-date and unprecedented summary of the prognostic impact of SS18-SSX fusion type in synovial sarcoma. Studies evaluating SS18-SSX fusion type as a prognostic marker in synovial sarcoma were systematically searched for in MEDLINE, EMBASE, and Web of Science. Comparative analysis of the pooled hazard ratios (HR) between fusion types was carried out, in order to assess the likelihood of overall survival (OS), disease-specific survival (DSS), progression-free survival (PFS), and metastasis-free survival (MFS). A total of 10 studies comprising 902 patients with synovial sarcoma were considered for the meta-analysis. The pooled HR for eight eligible studies evaluating for OS or DSS was 1.28 (95% confidence interval: 0.81-2.00), suggesting no significant difference between SS18-SSX1 and SS18-SSX2 (P = 0.29). For seven studies which evaluated for PFS or MFS, the presence of SS18-SSX1 may indicate a lower survival probability than that of SS18-SSX2, although the effect did not reach a level of statistical significance (P = 0.09). There was no significant difference in OS or DSS between SS18-SSX1 and SS18-SSX2, but there were indications of SS18-SSX1 being an unfavorable prognostic factor of PFS or MFS. Further studies including cohorts with a longer follow-up period are needed.

Initially localized synovial sarcoma in adults: a retrospective single-center analysis of 26 patients registered at the Department of Oncology, University of Vienna between 2004 and 2013

BACKGROUND

Synovial sarcoma is a rare subgroup of all soft-tissue sarcomas. The aim of this retrospective single-center analysis was to investigate the outcome of patients with initially localized disease.

PATIENTS AND METHODS

Twenty-six patients were enrolled in this retrospective single-center analysis. Baseline characteristics, treatment and outcome were evaluated.

RESULTS

In 13 patients (50%), the tumor was located in the lower extremity and in 4 patients (15%) in the upper extremity. Surgical resection was done in all but 2 patients (92%). Re-resection was done in 7 patients (27%). Fourteen patients (54%) received adjuvant chemotherapy. After a median follow-up of 23.3 months (range: 2.6-150.3), median disease-free survival was not reached at the time of analysis. Eight patients (31%) relapsed after initial therapy. Surgery was done in 2 patients, amputation in 1 patient, palliative chemotherapy was administered in 3 and radiation therapy in 2 patients. Median overall survival (OS) for all patients was not reached at the time of analysis. The estimated 5-year OS rate was 62%.

CONCLUSION

Patients with initially localized synovial sarcoma who were included in this retrospective single-center analysis have an estimated 5-year OS rate of 62%.

The clinical implication of SS18-SSX fusion gene in synovial sarcoma

Background:

The aim of this study is to evaluate distribution and clinical impact of the SS18-SSX fusion gene in patients with synovial sarcoma in China.

Methods:

We collected and analysed the clinical data of 88 patients using univariate and multivariate survival analysis. HEK 293T and NIH 3T3 cell lines were transfected with the SS18-SSX1 or SS18-SSX2 gene to determine the respective involvement of these fusion genes in cell proliferation and invasion.

Results:

Overall survival was significantly better among SS18-SSX2 cases (P=0.001), FNCLCC grade 2 cases (P<0.001), and UICC stage 1 or 2 (P<0.001) by univariate and multivariate survival analysis. SS18-SSX1-positive cells were more proliferative and invasive than SS18-SSX2-positive cells.

Conclusion:

SS18-SSX fusion type is a significant prognostic factor for patients with synovial sarcoma.

Expression of FGFR3 and FGFR4 and clinical risk factors associated with progression-free survival in synovial sarcoma

Although rare, synovial sarcoma (SS) is one of the most common soft tissue sarcomas affecting young adults. To investigate potential tumor markers related to synovial sarcoma prognosis, we carried out a single-institution retrospective analysis of 103 patients diagnosed with SS between 1980 and 2009. Clinical outcome data were obtained from medical records, and archived tissue samples were used to evaluate the relationship between progression-free survival (PFS) and several prognostic factors, including tumor expression of FGFR3 and FGFR4. No associations were found between PFS and gender, body mass index, tumor site, SS18-SSX translocation, or FGFR4 expression. As seen in previous studies, age at diagnosis (<35, 63% versus ≥35 years, 31% 10-year PFS; P = .033), histologic subtype (biphasic, 75% versus monophasic 34% 10-year PFS; P = .034), and tumor size (≤5 cm, 70% versus >5 cm, 22% 10-year PFS; P < .0001) were associated with PFS in SS patients. In addition, in a subset of patients with available archived tumor samples taken prior to chemotherapy or radiation (n = 34), higher FGFR3 expression was associated with improved PFS (P = .030). To the best of our knowledge, this is the largest study of SS to date to suggest a potential clinical role for FGFR3. While small numbers make this investigation somewhat exploratory, the findings merit future investigation on a larger scale.

Recurrent and novel SS18-SSX fusion transcripts in synovial sarcoma: description of three new cases

Synovial sarcoma (SS) is an aggressive type of tumor, comprising approximately 10 % of soft tissue sarcomas. Over 90 % of SS cases are characterized by the t(X;18)(p11.2;q11.2) translocation, which results mainly in the formation of oncogenic SS18-SSX1 or SS18-SSX2 fusions. In a typical SS18-SSX fusion transcript, exon 10 of SS18 is fused to exon 6 of SSX1/2. However, several variant fusion transcripts have been already described. In the present study, we examined the fusion transcript type in a series of 40 primary untreated SS tumor specimens using reverse transcription polymerase chain reaction and fluorescence in situ hybridization assay. We detected SS18-SSX1 transcript in 22 (55 %) patients and SS18-SSX2 transcript in 17 (42.5 %) patients, while in one patient, none of SS18-SSX1/2 fusion transcripts were identified. Among the cases under study, two tumors carried novel SS18-SSX1 and SS18-SSX2 variant translocations that were allegedly created by an alternative splicing, and in additional case, an unusual translocation variant previously described by other group was found. Our data suggest that alternative splicing may play an important role in novel fusion transcript formation, and additionally we show that it may be a recurrent event in SS. Furthermore, we describe the first case of a complex rearrangement possibly linking SS to REPS2 gene.

Synovial sarcoma in patients under 20 years of age: a multicenter study with a minimum follow-up of 10 years

PURPOSE

Synovial sarcoma (SS) is an aggressive soft-tissue tumor noted for late local recurrence and metastasis. This study investigates the long-term outcome of SS in patients of pediatric age and evaluates potential prognostic factors for SS.

METHODS

We performed a retrospective review of 13 SS cases in patients younger than 20 years at the time of diagnosis who had a minimum follow-up of 10 years. The mean follow-up for living patients (n = 8) was 20.1 years (12.1-27.6) and for nonsurvivors (n = 5) 4.9 years (range: 2.6-9.3). Nine patients had unplanned excisions (69%), of which 6 (67%) were performed prior to their referral. Re-excisions were necessary in all 13 patients. The factors sex, tumor site, tumor size, tumor grade, histological subtype, fusion type, and type of treatment were evaluated for their prognostic value.

RESULTS

Only 2 patients (15%) met the criteria of adequate tumor treatment. Overall, the 5- and 10-year survival rates were 77 and 61%, respectively. The mean time until a local recurrence (n = 5) was 3.2 years (range: 0.7-10.2), while there was a mean time of 2.1 years until the occurrence of late metastases (n = 5; range: 0.8-4.8). A high tumor grade and having a tumor in the trunk were adverse factors in terms of overall, local recurrence-free, and metastasis-free survival. Patients with wide resections or amputations had fewer local recurrences than patients with marginal or intralesional resections.

CONCLUSION

Inadequate primary excision of SS results in incomplete excision in the majority of cases. The tumor site, size, and histological grade should be considered when determining a risk-adapted treatment for SS, and wide surgical excision is the surgical intervention of choice. While local recurrence and late metastases appear to occur after a shorter time period in pediatric patients than in adults, in view of the tendency for late recurrence and metastasis with SS, follow-up should be at least 10 years.

Molecular and clinicopathological findings in a tonsillar synovial sarcoma. A case study and review of the literature

Synovial sarcoma (SS), 3-5% of which occurs in the head and neck region, has generally been regarded as high grade sarcoma. Recent analysis of clinical, morphological, and molecular characteristics of SS, however, identified low and high risk group of patients, resulting in important implications for the treatment of patients diagnosed with SS. We describe the case of a 31-year-old male who presented with biphasic SS with poorly differentiated areas (clinical stage IIA) in a palatine tonsil, an extremely rare site of SS. Molecular analyses revealed typical t(X;18) translocation of the SYT gene and a SYT/SSX1 fusion type. The tumor was surgically resected with free margins. Adjuvant radiotherapy or chemotherapy was not considered indicated. To date, the patient has remained free of tumor for 4 years after surgery. Literature review reveals that primary tonsillar HNSS has previously been documented only in three patients. In all of these patients the tumor was histologically biphasic; however only one published case and the case presented here showed areas of poor differentiation. We discuss the relevance of the presented findings with regard to prognostic and therapeutic considerations in SS in the head and neck region.

Genetic testing in orbital tumors

OBJECTIVE

This review aims to discuss the clinical application of cytogenetic and molecular testing in the diagnosis and prognosis of orbital tumors and, in so doing, highlight the basis of these methods, their advantages, and limitations.

SUMMARY

Specific chromosomal aberrations are detected in many lymphoproliferative neoplasms, soft tissue tumors, and in a few benign tumors of the orbit. Detection of these characteristic chromosomal translocations is most helpful to refine the diagnosis and classification, especially when the tumor is poorly differentiated and shows overlapping morphological features with another tumor type. This review outlines orbital tumors with characteristic chromosomal translocations and the relative frequency of detecting the genetic mutation. Various genetic techniques are available for genetic testing, including karyotyping, fluorescence in situ hybridization (FISH), reverse transcriptase polymerase chain reaction (RT-PCR), and genomic polymerase chain reaction (PCR). As yet, the newer methods of array-comparative genomic hybridization (array-CGH) and expression profiling are most commonly used in research settings or in large specialist centers, and their general application to cancer diagnostics is limited by their cost. Therefore, this review focuses on the methodologies that should be available to most diagnostic units. It is true that "one size does not fit all" in this field and that a combination of molecular techniques may be needed to confirm results at the genomic and transcriptional levels.

Prognostic implication of SYT-SSX fusion type and clinicopathological parameters for tumor-related death, recurrence, and metastasis in synovial sarcoma

The present study aimed to describe the distribution and features of the SYT-SSX fusion gene in Chinese patients with synovial sarcoma (SS), and to analyze the prognostic value of SYT-SSX fusion type and clinicopathological parameters for tumor-related death, recurrence, and metastasis in SS. SYT-SSX1 and SYT-SSX2 fusion transcripts were tested by reverse transcription-polymerase chain reaction in 141 formalin-fixed, paraffin-embedded SS. The prognostic implication of SYT-SSX fusion type and clinicopathological parameters were analyzed by univariate and multivariate survival analyses. SYT-SSX1 and SYT-SSX2 were detected in 50 (34.5%) and 91 (64.5%) tumors, respectively. SYT-SSX1 (risk ratio [RR] = 2.032, P = 0.004), larger tumor size (RR = 1.859, P = 0.008), and aggressive Fédération Nationale des Centers de Lutte Contre le Cancer grade (RR = 2.094, P = 0.001) were adverse predictors for disease-specific survival. However, SYT-SSX fusion type was not associated with local recurrence-free survival (P = 0.216). Patients with larger tumors (RR = 2.071, P = 0.005) and those who received marginal excision (RR = 2.556, P = 0.005) had poor local recurrence-free survival. Besides, SYT-SSX1 (RR = 1.859, P = 0.037), older age (RR = 1.799, P = 0.040), and aggressive International Union Against Cancer stage (RR = 3.690, P < 0.001) proved to be adverse prognostic factors for metastasis-free survival. In conclusion, compared to SYT-SSX1, SYT-SSX2 was more frequent in Chinese patients with SS. Moreover, SYT-SSX1 was an adverse predictor for disease-specific survival and metastasis-free survival, but had no relation to local recurrence-free survival. In addition, histological grade and tumor size were also important prognostic factors for SS.

Gene translocations in musculoskeletal neoplasms

Establishing the best diagnosis for musculoskeletal neoplasms requires a multidisciplinary approach using clinical, radiographic, and histologic analyses. Despite this rigorous approach, establishing accurate diagnoses and prognoses remains challenging. Improved diagnostic methods are expected as unique molecular signals for specific bone and soft tissue cancers are identified. We performed a systematic review of the best available evidence to explore three major applications of molecular genetics that will best benefit clinical management of musculoskeletal neoplasms: diagnostic, prognostic, and therapeutic applications. The specific questions addressed in this systematic review are: (1) What sets of histopathologic sarcoma subtypes will benefit from molecular evaluation and diagnosis? (2) What molecular methods are best applied to histopathologic sarcomas to distinguish between major subtypes? (3) How do the molecular patterns discovered on genetic diagnosis affect prognosis of certain sarcomas? (4) Which sarcoma translocations can benefit from an improved response and outcome using existing and forthcoming pharmacogenetic approaches targeting molecular events? This review summarizes recent advances in molecular genetics that are available and will soon be available to clinicians to better predict outcomes and subsequently help make future treatment decisions.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Sarcoma

Sarcomas comprise a heterogeneous group of mesenchymal neoplasms. They can be grouped into 2 general categories, soft tissue sarcoma and primary bone sarcoma, which have different staging and treatment approaches. This review includes a discussion of both soft tissue sarcomas (malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, synovial sarcoma, dermatofibrosarcoma protuberans, angiosarcoma, Kaposi sarcoma, gastrointestinal stromal tumor, aggressive fibromatosis or desmoid tumor, rhabdomyosarcoma, and primary alveolar soft-part sarcoma) and primary bone sarcomas (osteosarcoma, Ewing sarcoma, giant cell tumor, and chondrosarcoma). The 3 most important prognostic variables are grade, size, and location of the primary tumor. The approach to a patient with a sarcoma begins with a biopsy that obtains adequate tissue for diagnosis without interfering with subsequent optimal definitive surgery. Subsequent treatment depends on the specific type of sarcoma. Because sarcomas are relatively uncommon yet comprise a wide variety of different entities, evaluation by oncology teams who have expertise in the field is recommended. Treatment and follow-up guidelines have been published by the National Comprehensive Cancer Network (www.nccn.org).

Sarcoma molecular testing: diagnosis and prognosis

Methodologies employed in the rapidly developing field of soft tissue sarcoma molecular testing focus primarily on diagnosis using chromosomal translocations and the resulting fusion transcripts. Molecular prognostic testing holds promise in this complex group of rare mesenchymal malignancies, but results are preliminary and require further confirmation. Analysis of activating KIT mutations in gastrointestinal stromal tumors is currently being used in management of patient therapy.

Detection of SS18-SSX fusion transcripts in formalin-fixed paraffin-embedded neoplasms: analysis of conventional RT-PCR, qRT-PCR and dual color FISH as diagnostic tools for synovial sarcoma

Synovial Sarcoma consistently harbors t(X;18) resulting in SS18-SSX1, SS18-SSX2 and rarely SS18-SSX4 fusion transcripts. Of 328 cases included in our study, synovial sarcoma was either the primary diagnosis or was very high in the differential diagnosis in 134 cases: of these, amplifiable cDNA was obtained from 131. SS18-SSX fusion products were found in 126 (96%) cases (74 SS18-SSX1, 52 SS18-SSX2), using quantitative and 120 by conventional reverse transcriptase-polymerase chain reaction (RT-PCR). One hundred and one cases in a tissue microarray, analyzed by fluorescence in situ hybridization (FISH), revealed that 87 (86%) showed SS18 rearrangement: four RT-PCR positive cases, reported as negative for FISH, showed loss of one spectrum green signal, and 15 cases had multiple copies of the SS18 gene: both findings are potentially problematic when interpreting results. One of three cases, not analyzed by RT-PCR reaction owing to poor quality RNA, was positive by FISH. SS18-SSX1 was present in 56 monophasic and 18 biphasic synovial sarcoma: SS18-SSX2 was detected in 41 monophasic and 11 biphasic synovial sarcoma. Poorly differentiated areas were identified in 44 cases (31%). There was no statistically significant association between biphasic, monophasic and fusion type. Five cases were negative for SS18 rearrangement by all methods, three of which were pleural-sited neoplasms. Following clinical input, a diagnosis of mesothelioma was favored in one case, a sarcoma, not otherwise specified in another and a solitary fibrous tumor in the third case. The possibility of a malignant peripheral nerve sheath tumor could not be excluded in the other two cases. We concluded that the employment of a combination of molecular approaches is a powerful aid to diagnosing synovial sarcoma giving at least 96% sensitivity and 100% specificity but results must be interpreted in the light of other modalities such as clinical findings and immunohistochemical data.

Molecular Diagnosis of Sarcomas: Chromosomal Translocations in Sarcomas

Context.—Sarcomas are rare, numerous in type, and often difficult to definitively classify. Work in the last 2 decades has revealed that a significant subset of sarcomas are associated with specific chromosomal translocations producing chimeric (fusion) genes that play a role in the sarcomas' biology and are helpful in their differential diagnosis.

Objective.—To briefly review the sarcomas associated with specific translocations presenting Ewing sarcoma and synovial sarcoma as archetypes and to further explain how cytogenetic and molecular biologic approaches are being used in the diagnosis of sarcomas.

Data Sources.—This work is based on a selected review of the relevant medical and scientific literature and our extensive experience with molecular testing in sarcomas.

Conclusions.—In addition to, and complementing, the traditional diagnostic methods of examination of hematoxylin-eosin stained slides, immunohistochemistry, and sound clinical-pathologic correlation, additional cytogenetic and molecular biologic methods are being increasingly utilized and relied on in sarcoma pathology. These methods include chromosomal karyotyping, fluorescence in-situ hybridization, spectral karyotyping, and polymerase chain reaction– based methods for demonstrating specific chromosomal translocations and fusion genes. Understanding the basis of these methods and their application is critical to better provide accurate and validated specific diagnoses of sarcomas.

SYT-SSX1 and SYT-SSX2 Interfere with Repression of E-Cadherin by Snail and Slug: A Potential Mechanism for Aberrant Mesenchymal to Epithelial Transition in Human Synovial Sarcoma

Synovial sarcoma is a primitive mesenchymal neoplasm characterized in almost all cases by a t(X;18) fusing the SYT transcriptional coactivator gene with either SSX1 or SSX2, with the resulting fusion gene encoding an aberrant transcriptional regulator. A subset of synovial sarcoma, predominantly cases with the SYT-SSX1 fusion, shows foci of morphologic epithelial differentiation in the form of nests of glandular epithelium. The striking spontaneous mesenchymal to epithelial differentiation in this cancer is reminiscent of a developmental switch, but the only clue to its mechanistic basis has been the observation that most cases of synovial sarcoma with glandular epithelial differentiation (GED) contain SYT-SSX1 instead of SYT-SSX2. We report here that SYT-SSX1 and SYT-SSX2 interact preferentially with Snail or Slug, respectively, and prevent these transcriptional repressors from binding to the proximal E-cadherin promoter as shown by coimmunoprecipitation and chromatin immunoprecipitation. Luciferase reporter assays reveal that SYT-SSX1 and SYT-SSX2 can respectively overcome the Snail- or Slug-mediated repression of E-cadherin transcription. This provides a mechanism by which E-cadherin expression, a prerequisite of epithelial differentiation, is aberrantly derepressed in synovial sarcoma and may also explain the association of GED with the SYT-SSX1 fusion because it interferes with Snail, the stronger repressor of the E-cadherin promoter. Thus, our data provide a mechanistic basis for the observed heterogeneity in the acquisition of epithelial characteristics in synovial sarcoma and highlight the potential role of differential interactions with Snail or Slug in modulating this phenotypic transition.

Grossly-resected synovial sarcoma treated by the German and Italian Pediatric Soft Tissue Sarcoma Cooperative Groups: discussion on the role of adjuvant therapies

Differently from adult oncologists that considered synovial sarcoma (SS) a tumor with uncertain chemosensitiveness, since two decades pediatric oncologists in Europe assumed that chemotherapy played an important role in SS treatment, so most pediatric patients were included in rhabdomyosarcoma protocols, receiving adjuvant chemotherapy regardless of risk factors. The German and Italian groups reviewed the data of grossly resected SS patients in order to define a risk-adapted treatment program for the next European protocol. A total of 150 patients < 21 years with localized SS who underwent initial gross resection between 1975 and 2002 were the object of this study. All but four cases received adjuvant chemotherapy. Post-operative radiotherapy was administered to 50% Group I and to 92% Group II patients. Five-year event-free survival (EFS) and overall survival (OS) were 77% and 89%, respectively. Survival rates were influenced by tumor size (EFS 92% and 56% for size < or = and > 5 cm, respectively) and local invasiveness, not by surgical margins. No metastatic relapses occurred in Group I < or = 5 cm patients, while the outcome was poor for T2B patients (EFS 41%) due to a high rate of metastatic relapse. Our study was unable to assess the role of adjuvant treatments in grossly-resected SS, but identified a subset of low-risk patients (IRS Group I, size < or = 5 cm), for which the omission of adjuvant chemotherapy could be suggested, and a subset of high-risk patients (T2B), who need treatment intensification.

Primary Intrathoracic Synovial Sarcoma

Synovial sarcoma (SS), an aggressive neoplasm accounting for up to 14% of soft tissue sarcomas, was recently recognized as a primary tumor in the lung and pleura. SS is characterized by the chromosomal translocation t(X;18)(SYT-SSX) found in more than 95% of the tumors. We report a cooperative study from the French Sarcoma Group and the Mesopath Group on 40 t(X;18)(SYT-SSX)-positive primary intrathoracic SS. There were 22 males and 18 females, whose age ranged from 16 to 79 years (median, 47 years). Neoplasms were mostly circumscribed and of large size (median, 7.5 cm; range, 2-16 cm). Thirty-nine tumors were monophasic SS, including 24 (60%) monophasic fibrous and 15 (37.5%) poorly differentiated cases, and one lesion was a biphasic SS. A larger proportion of poorly differentiated tumors were observed among intrathoracic SS as compared with soft tissue SS. Immunohistochemically, 90% of the cases reacted with at least one epithelial marker. CD34 was focally expressed in 3 cases. SYT-SSX1 fusion transcripts were detected in 22 cases (56.4%) and SYT-SSX2 fusion transcripts in 17 cases. Median and 5-year disease-specific survival in 33 patients was 50 months and 31.6%. Median and 5-year disease-free survival was 24 months and 20.9%. Patient sex, age, tumor size, histologic subtype, grade, and SYS-SSX fusion type had no significant impact on outcome. In conclusion, intrathoracic SS are rare but aggressive tumors with poor prognosis. In this unusual location, the detection of SYT-SSX fusion transcripts is a valuable diagnostic adjunct.

Histologic grade, but not SYT-SSX fusion type, is an important prognostic factor in patients with synovial sarcoma: a multicenter, retrospective analysis

PURPOSE

To assess the prognostic value of SYT-SSX fusion type, in comparison with other factors, in a population of 165 patients with synovial sarcoma (SS).

PATIENTS AND METHODS

Data on 165 patients with SS (141 with localized disease at diagnosis) were studied retrospectively. The following parameters were examined for their potential prognostic value: age at diagnosis, sex, tumor site (extremities v proximal/truncal), size, histology, mitotic count, necrosis, histologic grade (Federation Nationale des Centres de Lutte Contre le Cancer system), stage (1997 tumor-node-metastasis system classification), surgical margin status (assessed histologically), and fusion type (SYT-SSX1 v SYT-SSX2). Median follow-up time was 37 months (range, 2 to 302 months).

RESULTS

Among those patients with localized disease at diagnosis, median and 5-year disease-specific survivals (DSS) for the SYT-SSX1 and SYT-SSX2 subgroups were 126 months and 67.4% versus 82 months and 63.2%, respectively (P = .12). Median and 5-year metastasis-free survivals (MFS) were 84 months and 54.2% for SYT-SSX1 versus 50 months and 47.6% for SYT-SSX2 (P = .76). Univariate analyses showed that high histologic grade (grade 3), high mitotic count (>/= 10 mitoses/10 high-power fields), stage III disease, size greater than 7 cm, tumor necrosis, and presence of areas of poorly differentiated morphology were significant adverse prognostic factors for DSS and MFS, whereas SYT-SSX fusion type, tumor histology (biphasic v monophasic), and patient sex were not. Age greater than 35 years adversely affected DSS but not MFS. In multivariate analyses, histologic grade was the most significant prognostic factor for both DSS and MFS.

CONCLUSION

For patients with localized SS, histologic grade but not SYT-SSX fusion type is a strong predictor of survival.

Establishment and characterization of a biphasic synovial sarcoma cell line, SYO-1

We describe here the establishment of a new synovial sarcoma cell line, SYO-1, derived from a biphasic synovial sarcoma that developed in the groin of a 19-year-old female. The cell line was maintained for more than 70 passages (more than 24 months) in vitro. The SYO-1 cells in monolayer culture exhibited a spindle shape without conspicuous pleomorphism. Immunohistochemically, the cells were positive for vimentin, type IV collagen, S-100, mdm2, bcl-2, c-Met and c-Kit. Tumors developed by their implantation in nude mice histologically showed biphasic features that were composed of areas of fascicles of spindle cells and areas of compact proliferation of polygonal to ovoid cells, which occasionally formed epithelial plaque and expressed cytokeratin and EMA. SYO-1 cells harbored the characteristic t(X;18)(p11.2;q11.2) translocation by chromosome analysis and SYT-SSX2 chimeric transcript by RT-PCR. The SYO-1 cells, the first characterized cell line derived from biphasic synovial sarcoma retaining the characteristic genetic and phenotypic features of the tumor, will be useful for various investigations on synovial sarcoma, especially for its epithelial differentiation.

Are there geographical differences in the frequency of SYT-SSX1 and SYT-SSX2 chimeric transcripts in synovial sarcoma?

Synovial sarcoma (SS) is characterized by the t(X;18)(p11.2;q11.2) chromosomal translocation, which results in generating either SYT-SSX1, SYT-SSX2 or, infrequently, SYT-SSX4 fusion gene. The ratio of SYT-SSX1:SYT-SSX2 fusions is close to 2:1 in the majority of studies, and SYT-SSX2 fusion has been only rarely observed in biphasic SS. In the present study, we compared two series of patients with SS, Slovenian (37 cases) and Dutch (14 cases), with respect to clinical, pathological and molecular findings. The two groups did not differ with regard to clinicopathological features. Whereas the frequency of different SYT-SSX fusions in the Dutch group was similar to that reported in the literature, we found an unexpectedly high number of tumors with SYT-SSX2 fusion in the Slovenian group. The ratio of SYT-SSX1:SYT-SSX2 fusion was 7:18 for monophasic and 2:7 for biphasic tumors in the Slovenian group. This distribution differs significantly from that observed in the Dutch group in the present study (P = 0.041) as well as from data reported in the recent large multi-institutional study on 243 patients (P = 0.0001). Our findings indicate possible geographical differences in the frequency of two SYT-SSX fusion transcripts in patients with synovial sarcoma.

Chromosomal translocations and sarcomas

This review examines how the identification of tumor-specific translocations and fusion proteins has advanced the basic scientific and clinical understanding of sarcomas. Recent genetic advances, including the ASPL-TFE3 fusion of alveolar soft part sarcoma, the JAZF1-JJAZ1 fusion of endometrial stromal sarcoma, and HMGIC fusions in liposarcoma, are discussed. Next, the review addresses the ways in which molecular genetic data have influenced diagnostic and prognostic paradigms. For example, recent studies describe the detection of occult tumor cells and the identification of primary renal neoplasms that are genetically related to alveolar soft part sarcoma. In addition, the review discusses potential therapies based on the targeting of sarcoma-specific fusion proteins. These reports describe the potential use of Gleevec (STI571) for dermatofibrosarcoma protuberans and the use of tumor-specific fusion proteins as potential targets for immunotherapy. Finally, basic scientific findings are reviewed that elucidate, for example, the aberrant functions of SYT-SSX in chromatin remodeling and of EWS-FLI1 in transcription and mRNA splicing. These and other emerging models of tumorigenesis will help identify new therapeutic targets.