Hippo pathway effectors YAP1/TAZ induce an EWS-FLI1-opposing gene signature and associate with disease progression in Ewing sarcoma

circELP2 reverse-splicing biogenesis and function as a pro-fibrogenic factor by targeting mitochondrial quality control pathway

Idiopathic pulmonary fibrosis (IPF) is considered as a chronic, fibrosing interstitial pneumonia with unknown mechanism. The present work aimed to explore the function, biogenesis and regulatory mechanism of circELP2 in pulmonary fibrosis and evaluate the value of blocking circELP2-medicated signal pathway for IPF treatment. The results showed that heterogeneous nuclear ribonucleoprotein L initiated reverse splicing of circELP2 resulting in the increase of circELP2 generation. The biogenetic circELP2 activated the abnormal proliferation and migration of fibroblast and extracellular matrix deposition to promote pulmonary fibrogenesis. Mechanistic studies demonstrated that cytoplasmic circELP2 sponged miR-630 to increase transcriptional co-activators Yes-associated protein 1 (YAP1) and transcriptional co-activator with PDZ-binding motif (TAZ). Then, YAP1/TAZ bound to the promoter regions of their target genes, such as mTOR, Raptor and mLST8, which in turn activated or inhibited the genes expression in mitochondrial quality control pathway. Finally, the overexpressed circELP2 and miR-630 mimic were packaged into adenovirus vector for spraying into the mice lung to evaluate therapeutic effect of blocking circELP2-miR-630-YAP1/TAZ-mitochondrial quality control pathway in vivo. In conclusion, blocking circELP2-medicated pathway can alleviate pulmonary fibrosis, and circELP2 may be a potential target to treat lung fibrosis.

IL-1 Family Members in Bone Sarcomas

IL-1 family members have multiple pleiotropic functions affecting various tissues and cells, including the regulation of the immune response, hematopoietic homeostasis, bone remodeling, neuronal physiology, and synaptic plasticity. Many of these activities are involved in various pathological processes and immunological disorders, including tumor initiation and progression. Indeed, IL-1 family members have been described to contribute to shaping the tumor microenvironment (TME), determining immune evasion and drug resistance, and to sustain tumor aggressiveness and metastasis. This review addresses the role of IL-1 family members in bone sarcomas, particularly the highly metastatic osteosarcoma (OS) and Ewing sarcoma (EWS), and discusses the IL-1-family-related mechanisms that play a role in bone metastasis development. We also consider the therapeutic implications of targeting IL-1 family members, which have been proposed as (i) relevant targets for anti-tumor and anti-metastatic drugs; (ii) immune checkpoints for immune suppression; and (iii) potential antigens for immunotherapy.

The DNA/RNA helicase DHX9 orchestrates the KDM2B-mediated transcriptional regulation of YAP1 in Ewing sarcoma

Ewing sarcomas (ES) are aggressive paediatric tumours of bone and soft tissues. Resistance to chemotherapy and high propensity to metastasize remain the main causes of treatment failure. Thus, identifying novel targets for alternative therapeutic approaches is urgently needed. DNA/RNA helicases are emerging as crucial regulators of many cellular processes often deregulated in cancer. Among them, DHX9 is up-regulated in ES and collaborates with EWS-FLI1 in ES transformation. We report that DHX9 silencing profoundly impacts on the oncogenic properties of ES cells. Transcriptome profiling combined to bioinformatic analyses disclosed a gene signature commonly regulated by DHX9 and the Lysine Demethylase KDM2B, with the Hippo pathway regulator YAP1 as a prominent target. Mechanistically, we found that DHX9 enhances H3K9 chromatin demethylation by KDM2B and favours RNA Polymerase II recruitment, thus promoting YAP1 expression. Conversely, EWS-FLI1 binding to the promoter represses YAP1 expression. These findings identify the DHX9/KDM2B complex as a new druggable target to counteract ES malignancy.

Glycolysis-Metabolism-Related Prognostic Signature for Ewing Sarcoma Patients

Ewing sarcoma (EwS) is a malignant sarcoma which occurs in bone and soft tissues commonly happening in children with poor survival rates. Changes in cell metabolism, such as glycolysis, may provide the environment for the transformation and progression of tumors. We aimed to build a model to predict prognosis of EwS patients based on glycolysis and metabolism genes. Candidate genes were obtained by differential gene expression analysis based on GSE17679, GSE17674 and ICGC datasets. We performed GO and KEGG pathway enrichment analysis on candidate genes. Univariate Cox and LASSO Cox regression analyses were conducted to construct a model to calculate the Risk Score. GSEA was done between high-risk and low-risk groups. CIBERSORT was applied to analyze the immune landscape. We got 295 candidate glycolysis-metabolism-related genes which were enriched in 620 GO terms and 18 KEGG pathways. 12 Genes were selected by univariate Cox model and 5 of them were determined by LASSO Cox regression analysis to be used in the construction of the Risk Score model. The Risk Score could be considered as an independent prognosis factor. The immune landscape and immune checkpoints' expression significantly differed between high- and low-risk groups. Our research constructed a new glycolysis-metabolism-related genes (FABP5, EMILIN1, GLCE, PHF11 and PALM3) based prognostic signature for EwS patients and assisted in gaining insight into prognosis to improve therapies further.

Clinical perspectives and outcomes of the giant breast phyllodes tumor and sarcoma: a real-world retrospective study

BACKGROUND

Giant breast malignant phyllodes tumor or sarcoma (GBPS) are rare entities with diameter larger than 10 cm and variously histological pleomorphisms. This disease poses a significant threat to the quality of life of individuals, and its prognosis remains unclear. This study aimed to explore the differential diagnosis, treatment, and prognosis of GBPS in a real-world retrospective cohort.

METHODS

We collected GBPS (diameter > 10 cm, n = 10) and BPS (diameter ≤ 10 cm, n = 126) from patients diagnosed with sarcoma or malignant phyllodes tumor between 2008 and 2022. We analyzed clinical characteristics, histological status, treatment, and local recurrence using the Fisher's exact test between GBPS (diameter > 10 cm) and BPS (diameter ≤ 10 cm) cohort. We described overall survival (OS) and disease-free survival (DFS) using Kaplan-Meier curves and identified risk factors for local recurrence using logistic regression. The tumor size, age at diagnosis, and differential immunohistochemistry markers of breast sarcoma or phyllodes tumor to determine the prognosis of GBPS.

RESULTS

In our retrospective analysis of breast malignancies, we identified 10 cases of GBPS and 126 cases of BPS, corresponding to a GBPS prevalence of 0.17% (10/6000). The median age was 38.5 years (inter-quartile range, IQR: 28.25-48.5 years). During the follow-up of period (median: 80.5 months, IQR: 36.75-122 months), the local recurrence (LR) rate was 40% and 20.6%, respectively. Clinical characteristics of young age (HR:2.799, 95%CI -00.09276-0.017, p < 0.05) and cytological characteristics of marked stromal atypia (HR:0.88, 95% CI 0.39-1.40, p < 0.05) were risk factors for the poor prognosis of GBPS by COX regression model analysis. The Kaplan-Meier curves of GBPS 5-year disease-free survival (DFS) and overall survival (OS) were 31.5 months and 40 months, respectively, and were not associated with adjuvant radiation or chemotherapy.

CONCLUSION

We recommend mastectomy with a clear surgical margin as the preferred treatment for GBPS. Age and stromal atypia are significantly associated with recurrence. Adjuvant radiation therapy is advised; however, there was no improvement in overall survival. There is no consensus on the effectiveness of adjuvant chemotherapy and genetic methods, highlighting the need for further research into this aggressive tumor. We recommend a multidisciplinary approach involving a dedicated team for the management of GBPS.

Genetic Alterations and Deregulation of Hippo Pathway as a Pathogenetic Mechanism in Bone and Soft Tissue Sarcoma

The Hippo pathway is an evolutionarily conserved modulator of developmental biology with a key role in tissue and organ size regulation under homeostatic conditions. Like other signaling pathways with a significant role in embryonic development, the deregulation of Hippo signaling contributes to oncogenesis. Central to the Hippo pathway is a conserved cascade of adaptor proteins and inhibitory kinases that converge and regulate the activity of the oncoproteins YAP and TAZ, the final transducers of the pathway. Elevated levels and aberrant activation of YAP and TAZ have been described in many cancers. Though most of the studies describe their pervasive activation in epithelial neoplasms, there is increasing evidence pointing out its relevance in mesenchymal malignancies as well. Interestingly, somatic or germline mutations in genes of the Hippo pathway are scarce compared to other signaling pathways that are frequently disrupted in cancer. However, in the case of sarcomas, several examples of genetic alteration of Hippo members, including gene fusions, have been described during the last few years. Here, we review the current knowledge of Hippo pathway implication in sarcoma, describing mechanistic hints recently reported in specific histological entities and how these alterations represent an opportunity for targeted therapy in this heterogeneous group of neoplasm.

Endoglin and MMP14 Contribute to Ewing Sarcoma Spreading by Modulation of Cell–Matrix Interactions

Endoglin (ENG) is a mesenchymal stem cell (MSC) marker typically expressed by active endothelium. This transmembrane glycoprotein is shed by matrix metalloproteinase 14 (MMP14). Our previous work demonstrated potent preclinical activity of first-in-class anti-ENG antibody-drug conjugates as a nascent strategy to eradicate Ewing sarcoma (ES), a devastating rare bone/soft tissue cancer with a putative MSC origin. We also defined a correlation between ENG and MMP14 expression in ES. Herein, we show that ENG expression is significantly associated with a dismal prognosis in a large cohort of ES patients. Moreover, both ENG/MMP14 are frequently expressed in primary ES tumors and metastasis. To deepen in their functional relevance in ES, we conducted transcriptomic and proteomic profiling of in vitro ES models that unveiled a key role of ENG and MMP14 in cell mechano-transduction. Migration and adhesion assays confirmed that loss of ENG disrupts actin filament assembly and filopodia formation, with a concomitant effect on cell spreading. Furthermore, we observed that ENG regulates cell–matrix interaction through activation of focal adhesion signaling and protein kinase C expression. In turn, loss of MMP14 contributed to a more adhesive phenotype of ES cells by modulating the transcriptional extracellular matrix dynamics. Overall, these results suggest that ENG and MMP14 exert a significant role in mediating correct spreading machinery of ES cells, impacting the aggressiveness of the disease.

Hypoxia-activated neuropeptide Y/Y5 receptor/RhoA pathway triggers chromosomal instability and bone metastasis in Ewing sarcoma

Adverse prognosis in Ewing sarcoma (ES) is associated with the presence of metastases, particularly in bone, tumor hypoxia and chromosomal instability (CIN). Yet, a mechanistic link between these factors remains unknown. We demonstrate that in ES, tumor hypoxia selectively exacerbates bone metastasis. This process is triggered by hypoxia-induced stimulation of the neuropeptide Y (NPY)/Y5 receptor (Y5R) pathway, which leads to RhoA over-activation and cytokinesis failure. These mitotic defects result in the formation of polyploid ES cells, the progeny of which exhibit high CIN, an ability to invade and colonize bone, and a resistance to chemotherapy. Blocking Y5R in hypoxic ES tumors prevents polyploidization and bone metastasis. Our findings provide evidence for the role of the hypoxia-inducible NPY/Y5R/RhoA axis in promoting genomic changes and subsequent osseous dissemination in ES, and suggest that targeting this pathway may prevent CIN and disease progression in ES and other cancers rich in NPY and Y5R.

Ewing sarcoma tumour cells frequently metastasize to the bone but the molecular mechanisms governing this process are not well understood. Here, the authors show that neuropeptide Y/Y5 receptor pathway is activated in the hypoxic tumour microenvironment, which results in cytokinesis defects and chromosomal instability, leading to bone invasion.

Lamin A and the LINC complex act as potential tumor suppressors in Ewing Sarcoma

Lamin A, a main constituent of the nuclear lamina, is involved in mechanosignaling and cell migration through dynamic interactions with the LINC complex, formed by the nuclear envelope proteins SUN1, SUN2 and the nesprins. Here, we investigated lamin A role in Ewing Sarcoma (EWS), an aggressive bone tumor affecting children and young adults. In patients affected by EWS, we found a significant inverse correlation between LMNA gene expression and tumor aggressiveness. Accordingly, in experimental in vitro models, low lamin A expression correlated with enhanced cell migration and invasiveness and, in vivo, with an increased metastatic load. At the molecular level, this condition was linked to altered expression and anchorage of nuclear envelope proteins and increased nuclear retention of YAP/TAZ, a mechanosignaling effector. Conversely, overexpression of lamin A rescued LINC complex organization, thus reducing YAP/TAZ nuclear recruitment and preventing cell invasiveness. These effects were also obtained through modulation of lamin A maturation by a statin-based pharmacological treatment that further elicited a more differentiated phenotype in EWS cells. These results demonstrate that drugs inducing nuclear envelope remodeling could be exploited to improve therapeutic strategies for EWS.

Analysis of Yes-Associated Protein-1 (YAP1) Target Gene Signature to Predict Progressive Breast Cancer

Breast cancers are treated according to the ER/PR or HER2 expression and show better survival outcomes with targeted therapy. Triple-negative breast cancers (TNBCs) with a lack of expression of ER/PR and HER2 are treated with systemic therapy with unpredictable responses and outcomes. It is essential to investigate novel markers to identify targeted therapies for TNBC. One such marker is YAP1, a transcription co-activator protein that shows association with poor prognosis of breast cancer. YAP1 transcriptionally regulates the expression of genes that drive the oncogenic phenotypes. Here, we assess a potential YAP target gene signature to predict a progressive subset of breast tumors from METABRIC and TCGA datasets. YAP1 target genes were shortlisted based on expression correlation and concordance with YAP1 expression and significant association with survival outcomes of patients. Hierarchical clustering was performed for the shortlisted genes. The utility of the clustered genes was assessed by survival analysis to identify a recurring subset. Expression of the shortlisted target genes showed significant association with survival outcomes of HER2-positive and TNBC subset in both datasets. The shortlisted genes were verified using an independent dataset. Further validation using IHC can prove the utility of this potential prognostic signature to identify a recurrent subset of HER2-positive and TNBC subtypes.

Targeting the IGF/PI3K/mTOR Pathway and AXL/YAP1/TAZ pathways in Primary Bone Cancer

Primary bone cancers (PBC) belong to the family of mesenchymal tumors classified based on their cellular origin, extracellular matrix, genetic regulation, and epigenetic modification. The three major PBC types, Ewing sarcoma, osteosarcoma, and chondrosarcoma, are frequently aggressive tumors, highly metastatic, and typically occur in children and young adults. Despite their distinct origins and pathogenesis, these sarcoma subtypes rely upon common signaling pathways to promote tumor progression, metastasis, and survival. The IGF/PI3K/mTOR and AXL/YAP/TAZ pathways, in particular, have gained significant attention recently given their ties to oncogenesis, cell fate and differentiation, metastasis, and drug resistance. Naturally, these pathways – and their protein constituents – have caught the eye of the pharmaceutical industry, and a wide array of small molecule inhibitors and antibody drug-conjugates have emerged. Here, we review how the IGF/PI3K/mTOR and AXL/YAP/TAZ pathways promote PBC and highlight the drug candidates under clinical trial investigation.

Evaluation of NAB2-STAT6 Fusion Variants and Other Molecular Alterations as Prognostic Biomarkers in a Case Series of 83 Solitary Fibrous Tumors

Simple Summary

A solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm that can arise at any body location. Local or distant recurrences occur in a significant proportion of cases, but these recurrences are difficult to predict using clinical or pathological features. A specific genetic alteration, the gene fusion NAB2-STAT6, is considered to be the defining driver mutation, and different fusion variants seem to account for specific clinical and pathological features, but their prognostic value remains controversial. We inspected a series of 83 SFTs with a high rate of recurrence to evaluate the clinical significance of several potential biomarkers in addition to gene fusion. Our findings confirm previous observations and uncover novel associations of molecular alterations with clinical features, adding additional evidence for their potential application as molecular biomarkers that are helpful to predict the course of the disease.

Abstract

Risk stratification of solitary fibrous tumor (SFT) patients based on clinicopathological features has limited efficacy, especially in predicting late relapse or metastasis. The hallmark alteration of SFT is the gene fusion NAB2-STAT6, whose prognostic value remains controversial. As biological knowledge of this entity has increased in recent years, new molecular alterations have emerged that could be helpful to refine current risk models. Here, we evaluated NAB2-STAT6 fusion variants and other molecular alterations in a series of 83 SFTs that are enriched in progressing cases. Gene fusion variants were identified by targeted RNA-seq in the whole series, whereas TERT promoter (pTERT) mutations were inspected by Sanger sequencing in a subset of 18 cases. Immunohistochemical assays were performed to assess BCOR and NTRK expression as well as P53 mutation status in 45, 44, and 44 cases, respectively. While confirming the associations of gene fusion variants with clinicopathological parameters, our results do not prove their prognostic value. Pan-TRK immunoexpresion correlated with recurrence/progression, P53 staining associated with higher mitotic counts, and pTERT mutations were enriched in cases with fatal outcome. An intriguing correlation was found for BCOR protein expression with gene fusion variants, size, and tumor location.

STAG2 mutations alter CTCF-anchored loop extrusion, reduce cis-regulatory interactions and EWSR1-FLI1 activity in Ewing sarcoma

STAG2, a cohesin family gene, is among the most recurrently mutated genes in cancer. STAG2 loss of function (LOF) is associated with aggressive behavior in Ewing sarcoma, a childhood cancer driven by aberrant transcription induced by the EWSR1-FLI1 fusion oncogene. Here, using isogenic Ewing cells, we show that, while STAG2 LOF profoundly changes the transcriptome, it does not significantly impact EWSR1-FLI1, CTCF/cohesin, or acetylated H3K27 DNA binding patterns. In contrast, it strongly alters the anchored dynamic loop extrusion process at boundary CTCF sites and dramatically decreases promoter-enhancer interactions, particularly affecting the expression of genes regulated by EWSR1-FLI1 at GGAA microsatellite neo-enhancers. Down-modulation of cis-mediated EWSR1-FLI1 activity, observed in STAG2-LOF conditions, is associated with enhanced migration and invasion properties of Ewing cells previously observed in EWSR1-FLI1low cells. Our study illuminates a process whereby STAG2-LOF fine-tunes the activity of an oncogenic transcription factor through altered CTCF-anchored loop extrusion and cis-mediated enhancer mechanisms.

Ewing Sarcoma-Diagnosis, Treatment, Clinical Challenges and Future Perspectives

Ewing sarcoma, a highly aggressive bone and soft-tissue cancer, is considered a prime example of the paradigms of a translocation-positive sarcoma: a genetically rather simple disease with a specific and neomorphic-potential therapeutic target, whose oncogenic role was irrefutably defined decades ago. This is a disease that by definition has micrometastatic disease at diagnosis and a dismal prognosis for patients with macrometastatic or recurrent disease. International collaborations have defined the current standard of care in prospective studies, delivering multiple cycles of systemic therapy combined with local treatment; both are associated with significant morbidity that may result in strong psychological and physical burden for survivors. Nevertheless, the combination of non-directed chemotherapeutics and ever-evolving local modalities nowadays achieve a realistic chance of cure for the majority of patients with Ewing sarcoma. In this review, we focus on the current standard of diagnosis and treatment while attempting to answer some of the most pressing questions in clinical practice. In addition, this review provides scientific answers to clinical phenomena and occasionally defines the resulting translational studies needed to overcome the hurdle of treatment-associated morbidities and, most importantly, non-survival.

YAP/TAZ inhibition reduces metastatic potential of Ewing sarcoma cells

Ewing sarcoma (EwS) is a highly metastatic bone cancer characterized by the ETS fusion oncoprotein EWS-FLI1. EwS cells are phenotypically highly plastic and switch between functionally distinct cell states dependent on EWS-FLI1 fluctuations. Whereas EWS-FLI1^high cells proliferate, EWS-FLI1^low cells are migratory and invasive. Recently, we reported activation of MRTFB and TEAD, effectors of RhoA and Hippo signalling, upon low EWS-FLI1, orchestrating key steps of the EwS migratory gene expression program. TEAD and its co-activators YAP and TAZ are commonly overexpressed in cancer, providing attractive therapeutic targets. We find TAZ levels to increase in the migratory EWS-FLI1^low state and to associate with adverse prognosis in EwS patients. We tested the effects of the potent YAP/TAZ/TEAD complex inhibitor verteporfin on EwS cell migration in vitro and on metastasis in vivo. Verteporfin suppressed expression of EWS-FLI1 regulated cytoskeletal genes involved in actin signalling to the extracellular matrix, effectively blocked F-actin and focal-adhesion assembly and inhibited EwS cell migration at submicromolar concentrations. In a mouse EwS xenograft model, verteporfin treatment reduced relapses at the surgical site and delayed lung metastasis. These data suggest that YAP/TAZ pathway inhibition may prevent EwS cell dissemination and metastasis, justifying further preclinical development of YAP/TAZ inhibitors for EwS treatment.

Sarcoma treatment in the era of molecular medicine

Sarcomas are heterogeneous and clinically challenging soft tissue and bone cancers. Although constituting only 1% of all human malignancies, sarcomas represent the second most common type of solid tumors in children and adolescents and comprise an important group of secondary malignancies. More than 100 histological subtypes have been characterized to date, and many more are being discovered due to molecular profiling. Owing to their mostly aggressive biological behavior, relative rarity, and occurrence at virtually every anatomical site, many sarcoma subtypes are in particular difficult-to-treat categories. Current multimodal treatment concepts combine surgery, polychemotherapy (with/without local hyperthermia), irradiation, immunotherapy, and/or targeted therapeutics. Recent scientific advancements have enabled a more precise molecular characterization of sarcoma subtypes and revealed novel therapeutic targets and prognostic/predictive biomarkers. This review aims at providing a comprehensive overview of the latest advances in the molecular biology of sarcomas and their effects on clinical oncology; it is meant for a broad readership ranging from novices to experts in the field of sarcoma.

The YAP/TAZ Pathway in Osteogenesis and Bone Sarcoma Pathogenesis

YAP and TAZ are intracellular messengers communicating multiple interacting extracellular biophysical and biochemical cues to the transcription apparatus in the nucleus and back to the cell/tissue microenvironment interface through the regulation of cytoskeletal and extracellular matrix components. Their activity is negatively and positively controlled by multiple phosphorylation events. Phenotypically, they serve an important role in cellular plasticity and lineage determination during development. As they regulate self-renewal, proliferation, migration, invasion and differentiation of stem cells, perturbed expression of YAP/TAZ signaling components play important roles in tumorigenesis and metastasis. Despite their high structural similarity, YAP and TAZ are functionally not identical and may play distinct cell type and differentiation stage-specific roles mediated by a diversity of downstream effectors and upstream regulatory molecules. However, YAP and TAZ are frequently looked at as functionally redundant and are not sufficiently discriminated in the scientific literature. As the extracellular matrix composition and mechanosignaling are of particular relevance in bone formation during embryogenesis, post-natal bone elongation and bone regeneration, YAP/TAZ are believed to have critical functions in these processes. Depending on the differentiation stage of mesenchymal stem cells during endochondral bone development, YAP and TAZ serve distinct roles, which are also reflected in bone tumors arising from the mesenchymal lineage at different developmental stages. Efforts to clinically translate the wealth of available knowledge of the pathway for cancer diagnostic and therapeutic purposes focus mainly on YAP and TAZ expression and their role as transcriptional co-activators of TEAD transcription factors but rarely consider the expression and activity of pathway modulatory components and other transcriptional partners of YAP and TAZ. As there is a growing body of evidence for YAP and TAZ as potential therapeutic targets in several cancers, we here interrogate the applicability of this concept to bone tumors. To this end, this review aims to summarize our current knowledge of YAP and TAZ in cell plasticity, normal bone development and bone cancer.

Hippo/YAP Signaling Pathway: A Promising Therapeutic Target in Bone Paediatric Cancers?

Osteosarcoma and Ewing sarcoma are the most prevalent bone pediatric tumors. Despite intensive basic and medical research studies to discover new therapeutics and to improve current treatments, almost 40% of osteosarcoma and Ewing sarcoma patients succumb to the disease. Patients with poor prognosis are related to either the presence of metastases at diagnosis or resistance to chemotherapy. Over the past ten years, considerable interest for the Hippo/YAP signaling pathway has taken place within the cancer research community. This signaling pathway operates at different steps of tumor progression: Primary tumor growth, angiogenesis, epithelial to mesenchymal transition, and metastatic dissemination. This review discusses the current knowledge about the involvement of the Hippo signaling pathway in cancer and specifically in paediatric bone sarcoma progression.