Synovial sarcoma: from genetics to genetic-based animal modeling

Genetic and Molecular Heterogeneity of Synovial Sarcoma and Associated Challenges in Therapy

Synovial sarcoma (SS) is one of the most common types of pediatric soft tissue sarcoma (STS) being far less frequent in adults. This STS type is characterized by one specific chromosomal translocation SS18-SSX and the associated changes in signaling. However, other genetic and epigenetic abnormalities in SS do not necessarily include SS18-SSX-related events, but abnormalities are more sporadic and do not correlate well with the prognosis and response to therapy. Currently, targeted therapy for synovial sarcoma includes a limited range of drugs, and surgical resection is the mainstay treatment for localized cancer with adjuvant or neoadjuvant chemotherapy and radiotherapy. Understanding the molecular characteristics of synovial sarcoma subtypes is becoming increasingly important for detecting new potential targets and developing innovative therapies. Novel approaches to treating synovial sarcoma include immune-based therapies (such as TCR-T cell therapy to NY-ESO-1, MAGE4, PRAME or using immune checkpoint inhibitors), epigenetic modifiers (HDAC inhibitors, EZH2 inhibitors, BRD disruptors), as well as novel or repurposed receptor tyrosine kinase inhibitors. In the presented review, we aimed to summarize the genetic and epigenetic landscape of SS as well as to find out the potential niches for the development of novel diagnostics and therapies.

Synovial sarcoma of the viscera (lung and jejunum): a case report

We report the case of a woman nearing 70 years old who was admitted to the hospital with a complaint of "epigastric distension for 1 month". Her main signs and symptoms were progressive abdominal distension and occasional abdominal pain. Computed tomography suggested an abdominal mass. She had a surgical history of synovial sarcoma (SS) of the lungs. After admission, she was diagnosed with jejunal SS following a puncture biopsy and laparoscopic surgery. This disease usually occurs in the soft tissues of the limbs, and it is extremely rare for SS to originate in the jejunum. The morphologic heterogeneity of SS overlaps with other tumors and makes the diagnosis particularly difficult. Imaging studies usually lack specificity; however, measuring multiple immunohistochemical markers can greatly assist in the diagnosis and differential diagnosis of SS. This case not only enriches our understanding of SS and describes a rare site of origin, but also emphasizes the importance and challenges of achieving an accurate diagnosis. Immunohistochemical and molecular biological testing have important roles in the definitive diagnosis, highlighting the need for precise and innovative diagnostic and therapeutic approaches in SS.

Tumor size and surgical margins are important prognostic factors of synovial sarcoma - A retrospective study

Background

Synovial Sarcoma (SS) is a rare soft tissue sarcoma. Mean time to get a SS diagnosis from the onset of symptoms is 10 years, furthermore, SS is associated with late metastasis. Surgery is the main treatment option, whose quality deeply affects SS outcomes, and it can be associated to preoperative or post-operative radiotherapy. Chemotherapy is considered very effective in Children, while in adults its efficacy is still under debate. The aim of this study was to investigate the oncologic results in SS treatment and to identify the risk factors for local and systemic control of the disease.

Methods

From 1994 to 2018, 211 patients affected by SS were treated in 3 Referral Centres of Orthopaedic Oncology. One hundred seventy-seven patients were included in the study, the median follow-up length was 96 months (5-374).

Results

Overall Survival on the Kaplan Meier Analyses was 80%, 70% and 56% at 5, 10 and 20 years. In multivariate analyses, OS correlated with tumour size and negative surgical margins. Chemotherapy use wasn't associated with better survival although patients who underwent CT had bigger and more aggressive tumours.

Conclusions

Our findings suggests that surgery with negative margins is the most important factor in Synovial Sarcoma. Adjuvant treatments as chemotherapy and radiation therapy didn't change the disease's course.

Synovial Sarcoma of the Foot as an Atypical Cause of Persistent Metatarsalgia: A Report of 3 Cases

CASE

Three cases of atypical metatarsalgia are presented, all diagnosed with foot synovial sarcomas (SSs) at different stages of evolution, after a year of medical consultations. One case was treated with marginal excision without requiring bone excision; the second patient required amputation of the first ray; and the third patient, with advanced disease, required amputation through Chopart's joint.

CONCLUSION

Metatarsalgia is a recurrent reason for consultation in orthopaedics. Even so, patients with persistent symptoms should be studied further in depth. Computed tomography or magnetic resonance imaging can detect tumor pathology, such as SS, of insidious development.

SS18-SSX drives CREB activation in synovial sarcoma

Purpose

Synovial sarcoma (SySa) is a rare soft tissue tumor characterized by a reciprocal t(X;18) translocation. The chimeric SS18-SSX fusion protein represents the major driver of the disease, acting as aberrant transcriptional dysregulator. Oncogenic mechanisms whereby SS18-SSX mediates sarcomagenesis are incompletely understood, and strategies to selectively target SySa cells remain elusive. Based on results of Phospho-Kinase screening arrays, we here investigate the functional and therapeutic relevance of the transcription factor CREB in SySa tumorigenesis.

Methods

Immunohistochemistry of phosphorylated CREB and its downstream targets (Rb, Cyclin D1, PCNA, Bcl-xL and Bcl-2) was performed in a large cohort of SySa. Functional aspects of CREB activity, including SS18-SSX driven circuits involved in CREB activation, were analyzed in vitro employing five SySa cell lines and a mesenchymal stem cell model. CREB mediated transcriptional activity was modulated by RNAi-mediated knockdown and small molecule inhibitors (666-15, KG-501, NASTRp and Ro 31-8220). Anti-proliferative effects of the CREB inhibitor 666-15 were tested in SySa avian chorioallantoic membrane and murine xenograft models in vivo.

Results

We show that CREB is phosphorylated and activated in SySa, accompanied by downstream target expression. Human mesenchymal stem cells engineered to express SS18-SSX promote CREB expression and phosphorylation. Conversely, RNAi-mediated knockdown of SS18-SSX impairs CREB phosphorylation in SySa cells. Inhibition of CREB activity reduces downstream target expression, accompanied by suppression of SySa cell proliferation and induction of apoptosis invitro and in vivo.

Conclusion

In conclusion, our data underline an essential role of CREB in SySa tumorigenesis and provides evidence for molecular targeted therapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13402-022-00673-w.

Osteogenesis in the presence of chemotherapy: A biomimetic approach

Osteosarcoma (OS) is the most common bone tumor in pediatrics. After resection, allografts or metal endoprostheses reconstruct bone voids, and systemic chemotherapy is used to prevent recurrence. This urges the development of novel treatment options for the regeneration of bone after excision. We utilized a previously developed biomimetic, biodegradable magnesium-doped hydroxyapatite/type I collagen composite material (MHA/Coll) to promote bone regeneration in the presence of chemotherapy. We also performed experiments to determine if human mesenchymal stem cells (hMSCs) seeded on MHA/Coll scaffold migrate less toward OS cells, suggesting that hMSCs will not contribute to tumor growth and therefore the potential of oncologic safety in vitro. Also, hMSCs seeded on MHA/Coll had increased expression of osteogenic genes (BGLAP, SPP1, ALP) compared to hMSCs in the 2D condition, even when exposed to chemotherapeutics. This is the first study to demonstrate that a highly osteogenic scaffold can potentially be oncologically safe because hMSCs on MHA/Coll tend to differentiate and lose the ability to migrate toward tumor cells. Therefore, hMSCs on MHA/Coll could potentially be utilized for bone regeneration after OS excision.

The Biology of Synovial Sarcoma: State-of-the-Art and Future Perspectives

New molecular insights are being achieved in synovial sarcoma (SS) that can provide new potential diagnostic and prognostic markers as well as therapeutic targets. In particular, the advancement of research on epigenomics and gene regulation is promising. The concrete hypothesis that the pathogenesis of SS might mainly depend on the disruption of the balance of the complex interaction between epigenomic regulatory complexes and the consequences on gene expression opens interesting new perspectives. The standard of care for primary SS is wide surgical resection combined with radiation in selected cases. The role of chemotherapy is still under refinement and can be considered in patients at high risk of metastasis or in those with advanced disease. Cytotoxic chemotherapy (anthracyclines, ifosfamide, trabectedin, and pazopanib) is the treatment of choice, despite several possible side effects. Many possible drug-able targets have been identified. However, the impact of these strategies in improving SS outcome is still limited, thus making current and future research strongly needed to improve the survival of patients with SS.

The role of SYT-SSX fusion gene in tumorigenesis of synovial sarcoma

Synovial sarcoma (SS) is an aggressive malignancy of an unknown tissue origin that is characterized by biphasic differentiation. A possible basis of the pathogenesis of SS is pathognomonic t(X;18) (p11.2; q11.2) translocation, leading to the formation and expression of the SYT-SSX fusion gene. More than a quarter of the patients die of SS metastasis within 5 years after the diagnosis, but the pathogenic factors are unknown. Therefore, there is an urgent need to explore the pathogenesis, invasion, metastasis, and clinical treatment options for SS, especially molecular-targeted drug therapy. Recent studies have shown that the SYT-SSX fusion gene associated with SS may be regulated by different signaling pathways, microRNAs, and other molecules, which may produce stem cell characteristics or promote epithelial-mesenchymal transition, resulting in SS invasion and metastasis. This review article aims to show the relationship between the SYT-SSX fusion gene and the related pathway molecules as well as other molecules involved from different perspectives, which may provide a deeper and clearer understanding of the SYT-SSX fusion gene function. Therefore, this review may provide a more innovative and broader perspective of the current research, treatment options, and prognosis assessment of SS.

Frequency of Transducer-like Enhancer of Split 1 Immunohistochemical Expression in Synovial Sarcoma: An Institution-based Cross-sectional Study

Background Soft-tissue sarcomas comprise a diverse group of sarcomas with characteristic histologic features. However, histology alone is not adequate for a definitive diagnosis for many tumors. In such cases, immunohistochemistry (IHC) plays a key role in determining the line of differentiation and exact characterization. Transducer-like enhancer of split 1 (TLE1) has been recently described as a novel marker for synovial sarcoma (SS). Its high sensitivity and specificity make it a potential marker that distinguishes SS from histologic mimics such as malignant peripheral nerve sheath tumor (MPNST), Ewing's sarcoma (ES), and fibrosarcomatous dermatofibrosarcoma protuberans (FS-DFSP). The objective of our study was to assess the frequency of TLE1 immunohistochemical expression on SS cases of various subtypes. Methods This cross-sectional study was conducted at the Department of Histopathology, Aga Khan University, Karachi, Pakistan from February 3, 2018 to February 10, 2019. Tissue samples of 89 SS cases were selected for this study. Tumor sections were stained with hematoxylin and eosin (H&E), cytokeratin AEI/AE3 (CKAE1/AE3), epithelial membrane antigen (EMA), and TLE1 immunohistochemical stain. TLE1 expression was assessed based on the Remmele scoring system. Results Tissue samples of 89 SS cases were processed for the study. Mean (±) standard deviation (SD) of age was 25 (±7.36) years. Male:female ratio was 1.1:1. Of the 89 SS cases, 42 (47.2%) were monophasic, six (6.7%) were biphasic, and 41 (46.1%) were poorly differentiated. All the 89 cases showed positivity for TLE1 immunostain: 86 (96.6%) cases showed strong positivity, one (1.1%) case showed moderate expression, and two (2.2%) showed weak positivity. Conclusion This study shows that TLE1 is a highly sensitive immunostain for SS irrespective of the histologic type. However, it may show weak-to-moderate staining in poorly differentiated types. No statistically significant association was seen with respect to age group, gender, or type of SS.

Synovial sarcoma in the plantar region: A case report and literature review

BACKGROUND

Synovial sarcoma (SS), a rare malignant soft tissue tumor whose histological origin is still unknown, often occurs in limbs in young people and is easily misdiagnosed.

CASE SUMMARY

We report a 24-year-old man who sought treatment for plantar pain thought to be caused by a foot injury that occurred 4 years prior. Currently, he had been seen at another hospital for a 1-wk history of unexplained pain in the left plantar region and was treated with acupuncture, a kind of therapy of Chinese medicine, which partly relieved the pain. Because of this, the final diagnosis of biphasic SS was made after two subsequent treatments by pathological evaluation after the last operation. SS is rarely seen in the plantar area, and his history of a left plantar injury confused the original diagnosis.

CONCLUSION

This study shows that pathological and imaging examinations may play a vital role in the early diagnosis and treatment of SS.

Primary intraosseous hybrid epithelioid schwannoma/perineurioma in the proximal tibia: a case report of benign hybrid neoplasm with local hypercellularity

Background

As a new entity included in the 4th edition of the WHO classification of tumours of soft tissue and bone in 2013, hybrid peripheral nerve sheath tumours are benign composite neoplasms that demonstrate features of more than one type of nerve sheath tumour, with a wide age distribution and a predilection for superficial location. Those involving deep sites are relatively rare. To the best of our knowledge, only one case of primary intraosseous hybrid peripheral nerve sheath tumours has been documented. In this article, we report another case of hybrid peripheral nerve sheath tumours occurring in bone with different clinical, radiological and pathological features from those in the previously reported cases.

Case presentation

A 28-year-old female presented with a painful nodule in the right tibia. Radiological examination revealed an oval eccentric osteolytic lesion in the proximal tibia. Histologically, the circumscribed but unencapsulated lesion demonstrated biphasic cellular differentiation. Bland, small epithelioid cells arranged in clusters in the myxoid or collagenous stroma and inconspicuous spindle cells scattered in the hypercellular areas were suggested to originate from Schwann cells according to the detection of S100. Both the elongated spindle cells with thin, wavy nuclei and the spindle cells in fascicular or storiform pattern in hypercellular areas showed a positive immunoreaction for epithelial membrane antigen, indicating perineurial differentiation. Based on histological and immunochemical examinations, the patient was diagnosed with hybrid epithelioid schwannoma/perineurioma. The lesion was resected and has not recurred for 8 months since resection.

Conclusion

The present case is the second primary intraosseous hybrid peripheral nerve sheath tumour to be reported. This is also the first reported intraosseous tumour composed of epithelioid schwannoma and perineurioma with hypercellularity, indicating diverse involvement sites and a wide range of histological features among hybrid peripheral nerve sheath tumours. Awareness of such diversity is critical for accurate diagnoses. The morphological overlap with other spindle and epithelioid cell neoplasms, especially pure peripheral nerve sheath tumours, requires that immunochemical and molecular examinations be used as objective tools to provide the necessary information for a differential diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s13000-019-0829-x) contains supplementary material, which is available to authorized users.

Analysis of mutations in primary and metastatic synovial sarcoma

Synovial sarcoma is the most common pediatric non-rhabdomyosarcoma soft tissue sarcoma and accounts for about 8-10% of all soft tissue sarcoma in childhood and adolescence. The presence of a chromosomal translocation-associated SS18-SSX-fusion gene is causally linked to development of primary synovial sarcoma. Metastases occur in approximately 50-70% of synovial sarcoma cases with yet unknown mechanisms, which led to about 70-80% mortality rate in five years. To explore the possibilities to investigate metastatic mechanisms of synovial sarcoma, we carried out the first genome-wide search for potential genetic biomarkers and drivers associated with metastasis by comparative mutational profiling of 18 synovial sarcoma samples isolated from four patients carrying the primary tumors and another four patients carrying the metastatic tumors through whole exome sequencing. Selected from the candidates yielded from this effort, we examined the effect of the multiple missense mutations of ADAM17, which were identified solely in metastatic synovial sarcoma. The mutant alleles as well as the wild-type control were expressed in the mammalian cells harboring the SS18-SSX1 fusion gene. The ADAM17-P729H mutation was shown to enhance cell migration, a phenotype associated with metastasis. Therefore, like ADAM17-P729H, other mutations we identified solely in metastatic synovial sarcoma may also have the potential to serve as an entry point for unraveling the metastatic mechanisms of synovial sarcoma.

Canonical Wnt/β-catenin signaling activation in soft-tissue sarcomas: A comparative study of synovial sarcoma and leiomyosarcoma

BACKGROUND

Previous studies have shown that aberrant activation of the Wnt/β-catenin pathway is associated with many malignant neoplasms. This includes some soft-tissue sarcoma phenotypes, most notably synovial sarcoma, implicating potential targets for novel molecular therapies.

OBJECTIVE

We investigate the level of Wnt/β-catenin pathway activation present in leiomyosarcomas relative to synovial sarcomas, using expression of LEF1 and β-catenin as surrogates.

METHODS

Cancer outlier profile analysis was performed on messenger RNA expression datasets in Oncomine (70 synovial sarcomas, 178 leiomyosarcomas). Results for LEF1 and β-catenin messenger RNA expression were reported in terms of median-centered intensity. Separate immunohistochemical studies were performed on tissue microarrays created from 77 synovial sarcomas and 89 leiomyosarcomas using antibodies to LEF1 and β-catenin. Tumors with unequivocal strong nuclear staining involving ⩾5% of cells were interpreted as positive.

RESULTS

Cancer outlier profile analysis demonstrated a higher level of LEF1 messenger RNA expression in synovial sarcomas than in leiomyosarcomas (p < 0.0001), but showed no significant difference in β-catenin messenger RNA expression (p = 0.868). Immunohistochemistry showed most synovial sarcomas had strong nuclear expression of LEF1 (79%) and β-catenin (84%), while a small minority of leiomyosarcomas had strong nuclear expression of LEF1 (5%) and β-catenin (6%).

CONCLUSION

These results provide further evidence that aberrant activation of the Wnt/β-catenin pathway is present in most synovial sarcomas, but not in most leiomyosarcomas. While targeting the constituents of this pathway might be effective in the treatment of synovial sarcomas, it is not likely to be an effective strategy in the treatment of leiomyosarcomas.

Clinicopathological features, treatment and survival outcomes of synovial sarcoma

Introduction:

Synovial sarcoma (SS) is a malignant mesenchymal tumor. It is most common among children and adults. The data on SS from India are scarce. In this study, we analyzed the clinicopathological treatment parameters and survival outcomes of SS patients.

Materials and Methods:

A total of 57 histologically proven SS diagnosed from 2010 to 2016 were retrospectively analyzed.

Results:

The median age was 23 years with a male-to-female ratio of 1.28:1. Localized disease was seen in 44 patients (77%) and 13 patients (23%) had metastasis. The primary sites of involvement such as lower limb, upper limb, thorax, and abdomen were seen in 60%, 28%, 7%, and 5% patients, respectively. Surgery was done in 39 patients and 18 patients had unresectable disease. Adjuvant chemotherapy with doxorubicin-based regimen was given in 30 patients and adjuvant radiotherapy in 21 patients. Palliative chemotherapy with anthracycline-based or gemcitabine-based regimen was used in 17 and 2 patients, respectively. The median event-free survival (EFS) was 30 months with 3 years and EFS rate was 36%; median progression-free survival (PFS) was 11.5 months and 1 year; and PFS rate was 38%. On univariate analysis, resection and performance status were significantly associated with survival. There is no impact of grade and size of the tumor on survival. In metastatic patients, the lung is the most common site.

Conclusion:

SS is the most common soft-tissue sarcoma among adults. Resectability and performance status were impacting the survival.

Pleural malignant mesothelioma versus pleuropulmonary synovial sarcoma: a clinicopathological study of 22 cases with molecular analysis and survival data

The aim of this study was to carry out a comparative analysis by transducin-like enhancer of split 1 (TLE1) immunohistochemistry and molecular analysis of SYT-SSX, for 16 pleural predominantly sarcomatoid mesotheliomas and six cases of pleuropulmonary synovial sarcoma (five pleural in distribution only, with one case of a predominantly subpleural upper lobe synovial sarcoma), all of which were solely or predominantly monophasic. Our comparison included survival and some clinical data. We consider that the following points emerged from this study.

Combined experience of six independent laboratories attempting to create an Ewing sarcoma mouse model

Ewing sarcoma (ES) involves a tumor-specific chromosomal translocation that produces the EWS-FLI1 protein, which is required for the growth of ES cells both in vitro and in vivo. However, an EWS-FLI1-driven transgenic mouse model is not currently available. Here, we present data from six independent laboratories seeking an alternative approach to express EWS-FLI1 in different murine tissues. We used the Runx2, Col1a2.3, Col1a3.6, Prx1, CAG, Nse, NEFL, Dermo1, P0, Sox9 and Osterix promoters to target EWS-FLI1 or Cre expression. Additional approaches included the induction of an endogenous chromosomal translocation, in utero knock-in, and the injection of Cre-expressing adenovirus to induce EWS-FLI1 expression locally in multiple lineages. Most models resulted in embryonic lethality or developmental defects. EWS-FLI1-induced apoptosis, promoter leakiness, the lack of potential cofactors, and the difficulty of expressing EWS-FLI1 in specific sites were considered the primary reasons for the failed attempts to create a transgenic mouse model of ES.

Sodium selenite induces apoptosis and inhibits autophagy in human synovial sarcoma cell line SW982 in vitro

The present study aimed to examine the effects of sodium selenite on the SW982 human synovial sarcoma cell line in relation to cell viability, apoptosis and autophagy. The results indicated that sodium selenite reduced cell viability and induced apoptosis by activating caspase-3 and members of the poly (ADP-ribose) polymerase and Bcl-2 protein families in SW982 cells. Furthermore, autophagy was also suppressed by sodium selenite treatment in SW982 cells, and apoptosis was upregulated in cells co-treated with sodium selenite and the autophagy inhibitor 3-methyladenine. By contrast, apoptosis was downregulated when sodium selenite was combined with rapamycin, an inducer of autophagy. The results indicated that autophagy may protect cells from the cytotoxicity of sodium selenite. The present study results demonstrated that sodium selenite induced apoptosis and inhibited autophagy and autophagy-protected cells from death by antagonizing sodium selenite-induced apoptosis in SW982 cells in vitro.

Synovial Sarcoma: Advances in Diagnosis and Treatment Identification of New Biologic Targets to Improve Multimodal Therapy

Synovial sarcoma is a translocation-associated soft-tissue malignancy that frequently affects adolescents and young adults. It is driven by one of the fusion oncoproteins SS18-SSX1, SS18-SSX2, or rarely, SS18-SSX4. Prognosis of patients with recurrent or metastatic disease is generally poor, and newer therapeutic strategies are needed. In this review, we present recent discoveries in the pathogenesis, diagnosis, and treatment of synovial sarcoma. We discuss potential therapeutic strategies to improve clinical outcomes in this disease.

Differentiating and Categorizing of Liposarcoma and Synovial Sarcoma Neoplasms by Fluorescence in Situ Hybridization

BACKGROUND & OBJECTIVE

Soft tissue sarcomas (STS) constitute an uncommon and heterogeneous group of tumors of mesenchymal origin and various cytogenetic abnormalities ranging from distinct genomic rearrangements, such as chromosomal translocations and amplifications, to more intricate rearrangements involving multiple chromosomes. Fluorescence in situ hybridization (FISH) can be used to identify these chromosomal translocations and amplifications, and sub classify STS precisely. The current study aimed at investigating the usefulness of FISH, as a diagnostic ancillary aid, to detect cytogenetic abnormalities such as MDM2 (murine double minute 2) amplification and CHOP(C/EBP homologous protein) rearrangement in liposarcoma, as well as SYT (synaptotagmin) rearrangement in synovial sarcoma.

METHODS

The FISH technique was used to analyze 17 specimens of liposarcoma for MDM2 amplification and CHOP rearrangement, and 10 specimens of synovial sarcoma for SYT rearrangement. The subtypes of liposarcoma and synovial sarcomas were reclassified according to the FISH results and compared with those of the respective histological findings.

RESULTS

According to the FISH results in 17 liposarcoma cases, well-differentiated liposarcoma(WDLPS), dedifferentiated liposarcoma (DDLPS), and myxoidliposarcoma (MLPS)subtypes were 41%, 53%, and 6%, respectively. In different subtypes of liposarcoma, a total of 30% mismatches were observed between pathologic and cytogenetic results. According to the histological findings from FISH analysis, SYT rearrangement was found only in three out of 10 (30%) synovial sarcomas.

CONCLUSION

The detection of cytogenetic abnormalities in patients with liposarcoma and synovial sarcoma by FISH technique provides an important objective tool to confirm sarcoma diagnosis and sub classification of specific sarcoma subtypes in such patients.

HMGB1-mediated autophagy decreases sensitivity to oxymatrine in SW982 human synovial sarcoma cells

Oxymatrine (OMT) is a type of alkaloid extracted from a traditional Chinese medicinal herb, Sophora flavescens. Although the antitumor activities of OMT have been observed in various cancers, there are no reports regarding the effects of OMT on human synovial sarcoma. In the present study, we analyzed the antitumor activities of OMT in SW982 human synovial sarcoma cells and determine whether high mobility group box protein 1 (HMGB1)-mediated autophagy was associated with its therapeutic effects. We found that OMT exhibited antitumor activity in SW982 cells and facilitated increases in autophagy. Inhibition of autophagy by 3-MA or ATG7 siRNA increased the level of apoptosis, which indicated that OMT-induced autophagy protected cells from the cytotoxicity of OMT. Administration of OMT to SW982 cells increased the expression of HMGB1. When HMGB1 was inhibited via HMGB1-siRNA, OMT-induced autophagy was decreased, and apoptosis was increased. Furthermore, we found that HMGB1-siRNA significantly increased the expression of p-Akt and p-mTOR. OMT-induced autophagy may be mediated by the Akt/mTOR pathway, and HMGB1 plays a vital role in the regulation of autophagy. Therefore, we believe that combining OMT with an inhibitor of autophagy or HMGB1 may make OMT more effective in the treatment of human synovial sarcoma.

The fusion protein SS18-SSX1 employs core Wnt pathway transcription factors to induce a partial Wnt signature in synovial sarcoma

Expression of the SS18/SYT-SSX fusion protein is believed to underlie the pathogenesis of synovial sarcoma (SS). Recent evidence suggests that deregulation of the Wnt pathway may play an important role in SS but the mechanisms whereby SS18-SSX might affect Wnt signaling remain to be elucidated. Here, we show that SS18/SSX tightly regulates the elevated expression of the key Wnt target AXIN2 in primary SS. SS18-SSX is shown to interact with TCF/LEF, TLE and HDAC but not β-catenin in vivo and to induce Wnt target gene expression by forming a complex containing promoter-bound TCF/LEF and HDAC but lacking β-catenin. Our observations provide a tumor-specific mechanistic basis for Wnt target gene induction in SS that can occur in the absence of Wnt ligand stimulation.

Preclinical Models Provide Scientific Justification and Translational Relevance for Moving Novel Therapeutics into Clinical Trials for Pediatric Cancer

Despite improvements in survival rates for children with cancer since the 1960s, progress for many pediatric malignancies has slowed over the past two decades. With the recent advances in our understanding of the genomic landscape of pediatric cancer, there is now enthusiasm for individualized cancer therapy based on genomic profiling of patients' tumors. However, several obstacles to effective personalized cancer therapy remain. For example, relatively little data from prospective clinical trials demonstrate the selective efficacy of molecular-targeted therapeutics based on somatic mutations in the patient's tumor. In this commentary, we discuss recent advances in preclinical testing for pediatric cancer and provide recommendations for providing scientific justification and translational relevance for novel therapeutic combinations for childhood cancer. Establishing rigorous criteria for defining and validating druggable mutations will be essential for the success of ongoing and future clinical genomic trials for pediatric malignancies.

Identification of potential mutations and genomic alterations in the epithelial and spindle cell components of biphasic synovial sarcomas using a human exome SNP chip

Background

Synovial sarcoma (SS) is one of the most aggressive soft-tissue sarcomas and is noted for late local recurrence and metastasis. It is of uncertain histological origin and exhibits a biphasic histopathological form involving both the mesenchyme and epithelium. Thus, its diagnosis and therapy remain a huge challenge for clinicians and pathologists. This study aimed to determine whether differential morphological-associated genomic changes could aid in ascertaining the histogenesis of SS and to determine whether these sarcomas showed some specific mutated genes between epithelial and spindle cells that would promote tumor invasion and metastasis.

Methods

We conducted a comprehensive genomic analysis of mesenchymal and epithelial components in 12 formalin-fixed paraffin-embedded biphasic SS samples using the Illumina human exon microarray. Exome capture sequencing was performed to validate the single nucleotide polymorphism (SNP)-chip data, and de novo data were generated using a whole-exome chip with the Illumina exon microarray. Fisher’s exact test based on PLINK analysis of the SNP-chip data.

Results

Here, the SNP-chip data showed that 336 SNPs had association P-values of less than 0.05 by chi-square test. We identified 23 significantly mutated genes between epithelial and spindle cell regions of SSs. Fifteen gene mutations were specific for the spindle cell component (65.2 %) and eight for the epithelial cell component (34.8 %). Most of these genes have not been previously reported in SS, and neuroguidin (NGDN), RAS protein activator like 3 (RASAL3), KLHL34 and MUM1L1 have not previously been linked to cancer; only one gene (EP300) has been reported in SS. Genomic analyses suggested that the differential SNPs in genes used for functional enrichment are mainly related to the inflammatory response pathway, adhesion, ECM–receptor interactions, TGF-β signaling, JAK–STAT signaling, phenylalanine metabolism, the intrinsic pathway and formation of fibrin.

Conclusions

This study investigated novel biological markers and tumorigenic pathways that would greatly improve therapeutic strategies for SS. The identified pathways may be closely correlated with the pathogenic mechanisms underlying SS, and SS development is associated with morphological features.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0144-7) contains supplementary material, which is available to authorized users.

Cells of origin in osteosarcoma: mesenchymal stem cells or osteoblast committed cells?

Osteosarcoma is a disease with many complex genetic abnormalities but few well defined genetic drivers of tumor initiation and evolution. The disease is diagnosed and defined through the observation of malignant osteoblastic cells that produce osteoid, however the exact cell of origin for this cancer remains to be definitively defined. Evidence exists to support a mesenchymal stem cell as well as committed osteoblast precursors as the cell of origin. Increasing numbers of experimental models have begun to shed light on to the likely cell population that gives rise to OS in vivo with the weight of evidence favoring an osteoblastic population as the cell of origin. As more information is gathered regarding osteosarcoma initiating cells and how they may relate to the cell of origin we will derive a better understanding of the development of this disease which may ultimately lead to clinical improvements through more personalized therapeutic approaches.

Structural network analysis of biological networks for assessment of potential disease model organisms

Model organisms provide opportunities to design research experiments focused on disease-related processes (e.g., using genetically engineered populations that produce phenotypes of interest). For some diseases, there may be non-obvious model organisms that can help in the study of underlying disease factors. In this study, an approach is presented that leverages knowledge about human diseases and associated biological interactions networks to identify potential model organisms for a given disease category. The approach starts with the identification of functional and interaction patterns of diseases within genetic pathways. Next, these characteristic patterns are matched to interaction networks of candidate model organisms to identify similar subsystems that have characteristic patterns for diseases of interest. The quality of a candidate model organism is then determined by the degree to which the identified subsystems match genetic pathways from validated knowledge. The results of this study suggest that non-obvious model organisms may be identified through the proposed approach.

Exomic analysis of myxoid liposarcomas, synovial sarcomas, and osteosarcomas

Bone and soft tissue sarcomas are a group of histologically heterogeneous and relatively uncommon tumors. To explore their genetic origins, we sequenced the exomes of 13 osteosarcomas, eight myxoid liposarcomas (MLPS), and seven synovial sarcomas (SYN). These tumors had few genetic alterations (median of 10.8). Nevertheless, clear examples of driver gene mutations were observed, including canonical mutations in TP53, PIK3CA, SETD2, AKT1, and subclonal mutation in FBXW7. Of particular interest were mutations in H3F3A, encoding the variant histone H3.3. Mutations in this gene have only been previously observed in gliomas. Loss of heterozygosity of exomic regions was extensive in osteosarcomas but rare in SYN and MLPS. These results provide intriguing nucleotide-level information on these relatively uncommon neoplasms and highlight pathways that help explain their pathogenesis.

Fusion genes in solid tumors: an emerging target for cancer diagnosis and treatment

Studies over the past decades have uncovered fusion genes, a class of oncogenes that provide immense diagnostic and therapeutic advantages because of their tumor-specific expression. Originally associated with hemotologic cancers, fusion genes have recently been discovered in a wide array of solid tumors, including sarcomas, carcinomas, and tumors of the central nervous system. Fusion genes are attractive as both therapeutic targets and diagnostic tools due to their inherent expression in tumor tissue alone. Therefore, the discovery and elucidation of fusion genes in various cancer types may provide more effective therapies in the future for cancer patients.

SS18-SSX fusion protein-induced Wnt/β-catenin signaling is a therapeutic target in synovial sarcoma

Synovial sarcoma is a high-grade soft tissue malignancy characterized by a specific reciprocal translocation t(X;18), which leads to the fusion of the SS18 (SYT) gene to one of three SSX genes (SSX1, SSX2 or SSX4). The resulting chimeric SS18-SSX protein is suggested to act as an oncogenic transcriptional regulator. Despite multimodal therapeutic approaches, metastatic disease is often lethal and the development of novel targeted therapeutic strategies is required. Several expression-profiling studies identified distinct gene expression signatures, implying a consistent role of Wnt/β-catenin signaling in synovial sarcoma tumorigenesis. Here we investigate the functional and therapeutic relevance of Wnt/β-catenin pathway activation in vitro and in vivo. Immunohistochemical analyses of nuclear β-catenin and Wnt downstream targets revealed activation of canonical Wnt signaling in a significant subset of 30 primary synovial sarcoma specimens. Functional aspects of Wnt signaling including dependence of Tcf/β-catenin complex activity on the SS18-SSX fusion proteins were analyzed. Efficient SS18-SSX-dependent activation of the Tcf/β-catenin transcriptional complex was confirmed by TOPflash reporter luciferase assays and immunoblotting. In five human synovial sarcoma cell lines, inhibition of the Tcf/β-catenin protein-protein interaction significantly blocked the canonical Wnt/β-catenin signaling cascade, accompanied by the effective downregulation of Wnt targets (AXIN2, CDC25A, c-MYC, DKK1, CyclinD1 and Survivin) and the specific suppression of cell viability associated with the induction of apoptosis. In SYO-1 synovial sarcoma xenografts, administration of small molecule Tcf/β-catenin complex inhibitors significantly reduced tumor growth, associated with diminished AXIN2 protein levels. In summary, SS18-SSX-induced Wnt/β-catenin signaling appears to be of crucial biological importance in synovial sarcoma tumorigenesis and progression, representing a potential molecular target for the development of novel therapeutic strategies.

Twist1 is essential in maintaining mesenchymal state and tumor-initiating properties in synovial sarcoma

Synovial sarcoma is an aggressive mesenchymal tumor with dual differentiation; epithelial and mesenchymal differentiation. However, the molecular mechanisms behind tumorigenesis and dual differentiation have remained elusive. In this study, we investigated whether Twist1 is an essential transcription factor for maintaining tumor-initiating cell properties in synovial sarcoma. First, we identified that Twist1 is overexpressed in most cases of synovial sarcoma (SS) samples as well as in two synovial sarcoma cell lines (HSSYII, SW982). Additionally, Twist1 depletion led to down-regulation of mesenchymal markers and up-regulation of epithelial markers in SS cell lines. The migratory and invasive abilities of SS cell lines were also significantly reduced following the loss of Twist1. These results indicate that Twist1 plays an essential role in the maintenance of mesenchymal character in SS. Furthermore, knock-down of Twist1 induced G1 cycle arrest and apoptosis as well as remarkable reduction in the sphere-forming cell subpopulation and side population cells. Moreover, Twist1 knock-down profoundly inhibited the growth of synovial sarcoma xenograft in nude mice compared to controls indicating that Twist1 is essential for tumor initiating cell properties. To explore transcriptional regulation by Twist1 at the genomic level, Chromatin immunoprecipiation-solexa whole genome sequencing (ChIP-SEQ) and cDNA microarray analysis were performed. Mesenchymal differentiation/proliferation and PDGF related genes were found to be affected by Twist1. Finally, depletion of SS18-SSX fusion oncoprotein by RNA inference induced down-regulation of Twist1, implying that Twist1 is regulated by SS18-SSX. Hence, our results suggest that Twist1 is an essential transcription factor for the maintenance of mesenchymal characters and tumor initiating properties of synovial sarcoma.

Targeting the Wnt pathway in synovial sarcoma models

Synovial sarcoma is an aggressive soft-tissue malignancy of children and young adults, with no effective systemic therapies. Its specific oncogene, SYT-SSX (SS18-SSX), drives sarcoma initiation and development. The exact mechanism of SYT-SSX oncogenic function remains unknown. In an SYT-SSX2 transgenic model, we show that a constitutive Wnt/β-catenin signal is aberrantly activated by SYT-SSX2, and inhibition of Wnt signaling through the genetic loss of β-catenin blocks synovial sarcoma tumor formation. In a combination of cell-based and synovial sarcoma tumor xenograft models, we show that inhibition of the Wnt cascade through coreceptor blockade and the use of small-molecule CK1α activators arrests synovial sarcoma tumor growth. We find that upregulation of the Wnt/β-catenin cascade by SYT-SSX2 correlates with its nuclear reprogramming function. These studies reveal the central role of Wnt/β-catenin signaling in SYT-SSX2-induced sarcoma genesis, and open new venues for the development of effective synovial sarcoma curative agents.

SIGNIFICANCE

Synovial sarcoma is an aggressive soft-tissue cancer that afflicts children and young adults, and for which there is no effective treatment. The current studies provide critical insight into our understanding of the pathogenesis of SYT–SSX-dependent synovial sarcoma and pave the way for the development of effective therapeutic agents for the treatment of the disease in humans.

Challenges and controversies in the diagnosis of malignant mesothelioma: Part 2. Malignant mesothelioma subtypes, pleural synovial sarcoma, molecular and prognostic aspects of mesothelioma, BAP1, aquaporin-1 and microRNA

Pleural malignant mesothelioma (MM) includes several unusual and even rare but distinctive histological subtypes, in addition to the usual subdivision into epithelioid, biphasic and sarcomatoid MM. Criteria for discrimination between fibrous pleuritis versus desmoplastic mesothelioma include evidence of neoplastic invasion for diagnosis of desmoplastic MM, but this histological assessment is complicated by the recently-described 'fake fat phenomenon' in cases of fibrous pleuritis. The distinction between biphasic and monophasic synovial sarcoma of the pleura versus biphasic and sarcomatoid MM can be problematical and is most cogently based upon molecular detection of the t(X;18) translocation, whereas a clear diagnosis of MM for a pleural tumour histologically resembling synovial sarcoma is favoured by a negative result for this translocation and, probably, microRNA evidence supportive of a diagnosis of MM. Aquaporin-1 (AQP1) is a molecule involved in the growth of MM cells, and yet is a factor reported to correlate with improved survival rates for MM with an epithelioid component, in comparison to AQP1-poor MM, as assessed from AQP1 expression by epithelioid MM cells only (apart from co-expression by stromal endothelial cells in addition to the tumour cells). Recent reports have also focused upon germline mutations in the BRCA1-associated protein 1 (BAP1), not only in cases of familial mesothelioma, but also BAP1 deletion in sporadic MM. Prognostic factors for MM include not only the histological subtypes, but other independent variables that include (among others), AQP1 expression by mesothelioma cells, the clinical status of the patient, the serum neutrophil:lymphocyte ratio and blood thrombocytosis.

The CD133+ subpopulation of the SW982 human synovial sarcoma cell line exhibits cancer stem-like characteristics

Several soft tissues sarcomas have been reported to contain cancer stem-like cells (CSCs) or tumor-initiating cells, based on their ability to initiate and sustain tumor growth. However, these cells have not yet been identified in the human synovial sarcoma cell line SW982. CD133, a surface glycoprotein specific to stem and progenitor cells, has been described as a CSC marker in different tumor types. In the present study, we identified a CSC subpopulation in SW982 cells using the CD133 cell surface marker. CD133-positive (CD133(+)) cells were identified in SW982 cells (8.59%); these cells showed an increased ability to form spherical colonies and could self-renew in serum-starved culture conditions, compared to CD133-negative (CD133(-)) cells. Real-time PCR analysis of stemness genes revealed that the CD133+ subpopulation expresses higher levels of Bmi1, c-Myc, Nanog, Oct3/4 and Sox2. CD133(+) cells showed increased resistance to cisplatin (CDDP) and doxorubicin (DXR), possibly due to upregulation of the ABCG2 drug transporter gene. In vivo studies revealed that the CD133(+) subpopulation is highly tumorigenic. These findings indicate that CD133(+) SW982 cells have characteristics similar to CSCs. This discovery may lead to the development of novel therapies that specifically target CD133(+) synovial sarcoma CSCs.

Modeling clear cell sarcomagenesis in the mouse: cell of origin differentiation state impacts tumor characteristics

Clear cell sarcoma (CCS) of tendons and aponeuroses is a deadly soft-tissue malignancy resembling melanoma, with a predilection for young adults. EWS-ATF1, the fusion product of a balanced chromosomal translocation between chromosomes 22 and 12, is considered the definitional feature of the tumor. Conditional expression of the EWS-ATF1 human cDNA in the mouse generates CCS-like tumors with 100% penetrance. Tumors, developed through varied means of initiating expression of the fusion oncogene, model human CCS morphologically, immunohistochemically, and by genome-wide expression profiling. We also demonstrate that although fusion oncogene expression in later stages of differentiation can transform mesenchymal progenitor cells and generate tumors resembling CCS generally, expression in cells retaining stem cell markers permits the full melanoma-related phenotype.

Notch signaling in pediatric soft tissue sarcomas

Pediatric soft tissue sarcomas are rare tumors of childhood, frequently characterized by specific chromosome translocations. Despite improvements in treatment, their clinical management is often challenging due to the low responsiveness of metastatic forms and aggressive variants to conventional therapeutic approaches, which leads to poor overall survival. It is widely thought that soft tissue sarcomas derive from mesenchymal progenitor cells that, during embryonic life, have developed chromosomal aberrations with de-regulation of the main pathways governing tissue morphogenesis. The Notch signaling pathway is one of the most important molecular networks involved in differentiation processes. Emerging evidence highlights the role of Notch signaling de-regulation in the biology of these pediatric sarcomas. In this review, we present an outline of recently gathered evidence on the role of Notch signaling in soft tissue sarcomas, highlighting its importance in tumor cell biology. The potential challenges and opportunities of targeting Notch signaling in the treatment of pediatric soft tissue sarcomas are also discussed.

Pediatric sarcomas: translating molecular pathogenesis of disease to novel therapeutic possibilities

Pediatric sarcomas represent a diverse group of rare bone and soft tissue malignancies. Although the molecular mechanisms that propel the development of these cancers are not well understood, identification of tumor-specific translocations in many sarcomas has provided significant insight into their tumorigenesis. Each fusion protein resulting from these chromosomal translocations is thought to act as a driving force in the tumor, either as an aberrant transcription factor (TF), constitutively active growth factor, or ligand-independent receptor tyrosine kinase. Identification of transcriptional targets or signaling pathways modulated by these oncogenic fusions has led to the discovery of potential therapeutic targets. Some of these targets have shown considerable promise in preclinical models and are currently being tested in clinical trials. This review summarizes the molecular pathology of a subset of pediatric sarcomas with tumor-associated translocations and how increased understanding at the molecular level is being translated to novel therapeutic advances.

Deconstruction of the SS18-SSX fusion oncoprotein complex: insights into disease etiology and therapeutics

Synovial sarcoma is a translocation-associated sarcoma where the underlying chromosomal event generates SS18-SSX fusion transcripts. In vitro and in vivo studies have shown that the SS18-SSX fusion oncoprotein is both necessary and sufficient to support tumorigenesis; however, its mechanism of action remains poorly defined. We have purified a core SS18-SSX complex and discovered that SS18-SSX serves as a bridge between activating transcription factor 2 (ATF2) and transducin-like enhancer of split 1 (TLE1), resulting in repression of ATF2 target genes. Disruption of these components by siRNA knockdown or treatment with HDAC inhibitors rescues target gene expression, leading to growth suppression and apoptosis. Together, these studies define a fundamental role for aberrant ATF2 transcriptional dysregulation in the etiology of synovial sarcoma.

SS18 together with animal-specific factors defines human BAF-type SWI/SNF complexes

BACKGROUND

Nucleosome translocation along DNA is catalyzed by eukaryotic SNF2-type ATPases. One class of SNF2-ATPases is distinguished by the presence of a C-terminal bromodomain and is conserved from yeast to man and plants. This class of SNF2 enzymes forms rather large protein complexes that are collectively called SWI/SNF complexes. They are involved in transcription and DNA repair. Two broad types of SWI/SNF complexes have been reported in the literature; PBAF and BAF. These are distinguished by the inclusion or not of polybromo and several ARID subunits. Here we investigated human SS18, a protein that is conserved in plants and animals. SS18 is a putative SWI/SNF subunit which has been implicated in the etiology of synovial sarcomas by virtue of being a target for oncogenic chromosomal translocations that underlie synovial sarcomas.

METHODOLOGY/PRINCIPAL FINDINGS

We pursued a proteomic approach whereby the SS18 open reading frame was fused to a tandem affinity purification tag and expressed in amenable human cells. The fusion permitted efficient and exclusive purification of so-called BAF-type SWI/SNF complexes which bear ARID1A/BAF250a or ARID1B/BAF250b subunits. This demonstrates that SS18 is a BAF subtype-specific SWI/SNF complex subunit. The same result was obtained when using the SS18-SSX1 oncogenic translocation product. Furthermore, SS18L1, DPF1, DPF2, DPF3, BRD9, BCL7A, BCL7B and BCL7C were identified. 'Complex walking' showed that they all co-purify with each other, defining human BAF-type complexes. By contrast,we demonstrate that human PHF10 is part of the PBAF complex, which harbors both ARID2/BAF200 and polybromo/BAF180 subunits, but not SS18 and nor the above BAF-specific subunits.

CONCLUSIONS/SIGNIFICANCE

SWI/SNF complexes are found in most eukaryotes and in the course of evolution new SWI/SNF subunits appeared. SS18 is found in plants as well as animals. Our results suggest that in both protostome and deuterostome animals, a class of BAF-type SWI/SNF complexes will be found that harbor SS18 or its paralogs, along with ARID1, DPF and BCL7 paralogs. Those BAF complexes are proteomically distinct from the eukaryote-wide PBAF-type SWI/SNF complexes. Finally, our results suggests that the human bromodomain factors BRD7 and BRD9 associate with PBAF and BAF, respectively.

High-dose ifosfamide as second- or third-line chemotherapy in refractory bone and soft tissue sarcoma patients

INTRODUCTION

For patients with refractory bone and soft tissue sarcoma (STS), treatment options have been limited. Ifosfamide is an alkylating agent with well-demonstrated efficacy against STS, and dose-dependent activity. The aim of this retrospective study was to evaluate the response rate, progression-free survival (PFS), progression-free rate (PFR), and median duration of response to high-dose ifosfamide (HDI) as at least second-line chemotherapy for patients with advanced bone sarcoma and STS.

PATIENTS AND METHODS

Thirty metastatic, unresectable sarcoma patients who were treated with HDI chemotherapy between May 1999 and November 2007 were included in the analysis. In total, 106 cycles (median 3 cycles; range 1-8 cycles) were administered. Twenty-one patients received treatment as second-line chemotherapy, and 9 patients as third-line treatment. HDI was given at a dose of 2 g/m(2) over 3 h, and at a dose of 2 g/m(2) per day; continuous infusion was administered on 6 consecutive days (2 g/m(2)/6 days) every 3 weeks.

RESULTS

After a median follow-up of 49 months (range 10-114), median PFS was 2.9 months (range 0.4-9.3) and median overall survival 8.7 months (range 0.4-57.8). The 3- and 6-month PFR were 47% (SE 9.1%) and 20% (SE 7.3%), respectively. Median response duration of HDI was 2.9 months (range 0.7-7.6). Of the 28 evaluable patients, 2 (7%) achieved complete response, 5 (18%) partial response, and 4 (14%) stable disease, and overall disease control was 39%. Two responders out of 7 (28.5%) and 4 patients out of 11 (36%) with controlled disease by HDI had a synovial sarcoma. Two patients were not evaluable because they were switched to another treatment due to ifosfamide-induced encephalopathy. Grade 3-4 neutropenia was seen in 13 (43%) patients, and treatment-related death was observed in one patient.

CONCLUSION

HDI at a total dose of 14 g/m(2) with mesna is still an active salvage regimen, particularly in patients with synovial sarcomas.

Intraosseous synovial sarcoma of the proximal tibia

Synovial Sarcoma is a malignant mesenchymal tumor that comprises 5–10% of all soft tissue sarcomas. The mean age of onset is thirty years old. Intraosseous presentation is very rare and has only been documented a few times. We report herein a case of a 53-year-old man with synovial sarcoma arising in the left proximal tibia. The patient underwent a wide surgical resection and reconstruction, followed by adjuvant chemotherapy. Three years later, the patient developed a local recurrence that resulted in an above-the-knee amputation. Eight months later, the patient has completed chemotherapy and is without signs of recurrence. The current recommended treatment for synovial sarcoma is wide surgical resection followed by chemotherapy as well as long-term followup. Despite improved surgical techniques, long-term survival rates remain low.