The Hippo signal transduction pathway in soft tissue sarcomas

mRNA Capture Sequencing and RT-qPCR for the Detection of Pathognomonic, Novel, and Secondary Fusion Transcripts in FFPE Tissue: A Sarcoma Showcase

We assess the performance of mRNA capture sequencing to identify fusion transcripts in FFPE tissue of different sarcoma types, followed by RT-qPCR confirmation. To validate our workflow, six positive control tumors with a specific chromosomal rearrangement were analyzed using the TruSight RNA Pan-Cancer Panel. Fusion transcript calling by FusionCatcher confirmed these aberrations and enabled the identification of both fusion gene partners and breakpoints. Next, whole-transcriptome TruSeq RNA Exome sequencing was applied to 17 fusion gene-negative alveolar rhabdomyosarcoma (ARMS) or undifferentiated round cell sarcoma (URCS) tumors, for whom fluorescence in situ hybridization (FISH) did not identify the classical pathognomonic rearrangements. For six patients, a pathognomonic fusion transcript was readily detected, i.e., PAX3-FOXO1 in two ARMS patients, and EWSR1-FLI1, EWSR1-ERG, or EWSR1-NFATC2 in four URCS patients. For the 11 remaining patients, 11 newly identified fusion transcripts were confirmed by RT-qPCR, including COPS3-TOM1L2, NCOA1-DTNB, WWTR1-LINC01986, PLAA-MOB3B, AP1B1-CHEK2, and BRD4-LEUTX fusion transcripts in ARMS patients. Additionally, recurrently detected secondary fusion transcripts in patients diagnosed with EWSR1-NFATC2-positive sarcoma were confirmed (COPS4-TBC1D9, PICALM-SYTL2, SMG6-VPS53, and UBE2F-ALS2). In conclusion, this study shows that mRNA capture sequencing enhances the detection rate of pathognomonic fusions and enables the identification of novel and secondary fusion transcripts in sarcomas.

YAP1-TFE3-fused hemangioendothelioma: a multi-institutional clinicopathologic study of 24 genetically-confirmed cases

YAP1-TFE3-fused hemangioendothelioma is an extremely rare malignant vascular tumor. We present the largest multi-institutional clinicopathologic study of YAP1-TFE3-fused hemangioendothelioma to date. The 24 cases of YAP1-TFE3-fused hemangioendothelioma showed a female predominance (17 female, 7 male) across a wide age range (20-78 years old, median 44). Tumors were most commonly located in soft tissue (50%), followed by bone (29%), lung (13%), and liver (8%), ranging from 3 to 115 mm in size (median 40 mm). About two-thirds presented with multifocal disease, including 7 cases with distant organ metastasis. Histopathologically, we describe three dominant architectural patterns: solid sheets of coalescing nests, pseudoalveolar and (pseudo)vasoformative pattern, and discohesive strands and clusters of cells set in a myxoid to myxohyaline stroma. These patterns were present in variable proportions across different tumors and often coexisted within the same tumor. The dominant cytomorphology (88%) was large epithelioid cells with abundant, glassy eosinophilic to vacuolated cytoplasm, prominent nucleoli and well-demarcated cell borders. Multinucleated or binucleated cells, prominent admixed erythrocytic and lymphocytic infiltrates, and intratumoral fat were frequently present. Immunohistochemically, ERG, CD31, and TFE3 were consistently expressed, while expression of CD34 (83%) and cytokeratin AE1/AE3 (20%) was variable. CAMTA1 was negative in all but one case. All cases were confirmed by molecular testing to harbor YAP1-TFE3 gene fusions: majority with YAP1 exon 1 fused to TFE3 exon 4 (88%), or less commonly, TFE3 exon 6 (12%). Most patients (88%) were treated with primary surgical resection. Over a follow-up period of 4-360 months (median 36 months) in 17 cases, 35% of patients remained alive without disease, and 47% survived many years with stable, albeit multifocal and/or metastatic disease. Five-year progression-free survival probability was 88%. We propose categorizing YAP1-TFE3-fused hemangioendothelioma as a distinct disease entity given its unique clinical and histopathologic characteristics in comparison to conventional epithelioid hemangioendothelioma.

Unraveling the IGF System Interactome in Sarcomas Exploits Novel Therapeutic Options

Aberrant bioactivity of the insulin-like growth factor (IGF) system results in the development and progression of several pathologic conditions including cancer. Preclinical studies have shown promising anti-cancer therapeutic potentials for anti-IGF targeted therapies. However, a clear but limited clinical benefit was observed only in a minority of patients with sarcomas. The molecular complexity of the IGF system, which comprises multiple regulators and interactions with other cancer-related pathways, poses a major limitation in the use of anti-IGF agents and supports the need of combinatorial therapeutic strategies to better tackle this axis. In this review, we will initially highlight multiple mechanisms underlying IGF dysregulation in cancer and then focus on the impact of the IGF system and its complexity in sarcoma development and progression as well as response to anti-IGF therapies. We will also discuss the role of Ephrin receptors, Hippo pathway, BET proteins and CXCR4 signaling, as mediators of sarcoma malignancy and relevant interactors with the IGF system in tumor cells. A deeper understanding of these molecular interactions might provide the rationale for novel and more effective therapeutic combinations to treat sarcomas.

Metabolic landscapes in sarcomas

Metabolic rewiring offers novel therapeutic opportunities in cancer. Until recently, there was scant information regarding soft tissue sarcomas, due to their heterogeneous tissue origin, histological definition and underlying genetic history. Novel large-scale genomic and metabolomics approaches are now helping stratify their physiopathology. In this review, we show how various genetic alterations skew activation pathways and orient metabolic rewiring in sarcomas. We provide an update on the contribution of newly described mechanisms of metabolic regulation. We underscore mechanisms that are relevant to sarcomagenesis or shared with other cancers. We then discuss how diverse metabolic landscapes condition the tumor microenvironment, anti-sarcoma immune responses and prognosis. Finally, we review current attempts to control sarcoma growth using metabolite-targeting drugs.

YAP1-TFE3 gene fusion variant in clear cell stromal tumour of lung: report of two cases in support of a distinct entity

AIMS

Clear cell (haemangioblastoma-like) stromal tumour of the lung is a newly described, rare pulmonary neoplasm. Recurrent YAP1-TFE3 gene fusions have recently been reported in three cases. We describe two additional cases and confirm the characteristic YAP1-TFE3 gene fusion.

METHODS AND RESULTS

Two mesenchymal tumours of lung were identified from our soft tissue pathology consultation services and RNA sequencing was performed. Both cases were in male patients, aged 35 and 77 years. Both presented as solitary lung nodules measuring 3.9 and 7.5 cm in greatest dimension. Histopathologically, the tumours were composed of epithelioid to plump spindle cells arranged in packets and solid sheets. The cells showed fusiform to ovoid nuclei with open chromatin, variably prominent nucleoli and scant to moderate, clear to eosinophilic cytoplasm. Cytological atypia and significant mitotic activity were minimal. None of the tumours expressed lineage-specific immunophenotypical markers. Both cases were diffusely positive for nuclear TFE3. Unlike YAP1-TFE3-fused epithelioid haemangioendothelioma, for which the fusion breakpoint occurs in YAP1 exon 1 and TFE3 exons 4 or 6, the fusion breakpoints of these tumours were located in YAP1 exon 4 and TFE3 exon 7. Following complete surgical resection, neither of the tumours has recurred or metastasised (follow-up period 6-7 months).

CONCLUSIONS

We validate the presence of YAP1-TFE3 gene fusion in a unique primary mesenchymal tumour of lung, adding additional support for clear cell stromal tumour of the lung as a distinct entity.

Establishment and Characterization of a Cell Line (S-RMS1) Derived from an Infantile Spindle Cell Rhabdomyosarcoma with SRF-NCOA2 Fusion Transcript

Background: Spindle cell rhabdomyosarcoma (S-RMS) is a rare tumor that was previously considered as an uncommon variant of embryonal RMS (ERMS) and recently reclassified as a distinct RMS subtype with NCOA2, NCOA1, and VGLL2 fusion genes. In this study, we established a cell line (S-RMS1) derived from a four-month-old boy with infantile spindle cell RMS harboring SRF-NCOA2 gene fusion. Methods: Morphological and molecular characteristics of S-RMS1 were analyzed and compared with two RMS cell lines, RH30 and RD18. Whole genome sequencing of S-RMS1 and clinical exome sequencing of genomic DNA were performed. Results: S-RMS1 showed cells small in size, with a fibroblast-like morphology and positivity for MyoD-1, myogenin, desmin, and smooth muscle actin. The population doubling time was 3.7 days. Whole genome sequencing demonstrated that S-RMS1 retained the same genetic profile of the tumor at diagnosis. A Western blot analysis showed downregulation of AKT-p and YAP-p while RT-qPCR showed upregulation of endoglin and GATA6 as well as downregulation of TGFßR1 and Mef2C transcripts. Conclusion: This is the first report of the establishment of a cell line from an infantile spindle cell RMS with SRF-NCOA2 gene fusion. S-RMS1 should represent a useful tool for the molecular characterization of this rare and almost unknown tumor.

New insights into the core Hippo signaling and biological macromolecules interactions in the biology of solid tumors

As an evolutionarily conserved pathway, Hippo signaling pathway impacts different pathology and physiology processes such as wound healing, tissue repair/size and regeneration. When some components of Hippo signaling dysregulated, it affects cancer cells proliferation. Moreover, the relation Hippo pathway with other signaling including Wnt, TGFβ, Notch, and EGFR signaling leaves effect on the proliferation of cancer cells. Utilizing a number of therapeutic approaches, such as siRNAs and long noncoding RNA (lncRNA) to prevent cancer cells through the targeting of Hippo pathways, can provide new insights into cancer target therapy. The purpose of present review, first of all, is to demonstrate the importance of Hippo signaling and its relation with other signaling pathways in cancer. It also tries to demonstrate targeting Hippo signaling progress in cancer therapy.

Discoidin Domain Receptors, DDR1b and DDR2, Promote Tumour Growth within Collagen but DDR1b Suppresses Experimental Lung Metastasis in HT1080 Xenografts

The Discoidin Domain Receptors (DDRs) constitute a unique set of receptor tyrosine kinases that signal in response to collagen. Using an inducible expression system in human HT1080 fibrosarcoma cells, we investigated the role of DDR1b and DDR2 on primary tumour growth and experimental lung metastases. Neither DDR1b nor DDR2 expression altered tumour growth at the primary site. However, implantation of DDR1b- or DDR2-expressing HT1080 cells with collagen I significantly accelerated tumour growth rate, an effect that could not be observed with collagen I in the absence of DDR induction. Interestingly, DDR1b, but not DDR2, completely hindered the ability of HT1080 cells to form lung colonies after intravenous inoculation, suggesting a differential role for DDR1b in primary tumour growth and lung colonization. Analyses of tumour extracts revealed specific alterations in Hippo pathway core components, as a function of DDR and collagen expression, that were associated with stimulation of tumour growth by DDRs and collagen I. Collectively, these findings identified divergent effects of DDRs on primary tumour growth and experimental lung metastasis in the HT1080 xenograft model and highlight the critical role of fibrillar collagen and DDRs in supporting the growth of tumours thriving within a collagen-rich stroma.

Inhibition of cyclin-dependent kinase 7 down-regulates yes-associated protein expression in mesothelioma cells

Cyclin-dependent kinase 7 (CDK7) is a protein kinase that plays a major role in transcription initiation. Yes-associated protein (YAP) is a main effector of the Hippo/YAP signalling pathway. Here, we investigated the role of CDK7 on YAP regulation in human malignant pleural mesothelioma (MPM). We found that in microarray samples of human MPM tissue, immunohistochemistry staining showed correlation between the expression level of CDK7 and YAP (n = 70, r = .513). In MPM cells, CDK7 expression level was significantly correlated with GTIIC reporter activity (r = .886, P = .019). Inhibition of CDK7 by siRNA decreased the YAP protein level and the GTIIC reporter activity in the MPM cell lines 211H, H290 and H2052. Degradation of the YAP protein was accelerated after CDK7 knockdown in 211H, H290 and H2052 cells. Inhibition of CDK7 reduced tumour cell migration and invasion, as well as tumorsphere formation ability. Restoration of the CDK7 gene rescued the YAP protein level and GTIIC reporter activity after siRNA knockdown in 211H and H2052 cells. Finally, we performed a co-immunoprecipitation analysis using an anti-YAP antibody and captured the CDK7 protein in 211H cells. Our results suggest that CDK7 inhibition reduces the YAP protein level by promoting its degradation and suppresses the migration and invasion of MPM cells. Cyclin-dependent kinase 7 may be a promising therapeutic target for MPM.

The Lethality of [Pazopanib + HDAC Inhibitors] Is Enhanced by Neratinib

Sarcomas are a diverse set of malignancies. For soft tissue sarcomas, the kinase and chaperone inhibitor pazopanib is a standard of care therapeutic. Previously, we demonstrated that HDAC inhibitors enhanced pazopanib lethality against sarcoma and other tumor cell types in vitro and in vivo. The present studies defined mechanisms of drug-combination resistance. Exposure of sarcoma and PDX ovarian carcinoma cells to [pazopanib + entinostat] caused a prolonged activation of ERBB1 and transient/prolonged activations of ERBB2, c-KIT, and c-MET, in a cell-specific fashion. The activities of mTORC1, mTORC2, GRP78, HSP90, and HSP70 were reduced, expression of Beclin1 and ATG5 enhanced, and the ATM-AMPK-ULK1-ATG13-Beclin1/ATG5 pathway activated. Inhibition of ERBB1/2/4 using neratinib or of c-MET using crizotinib significantly enhanced [pazopanib + entinostat] lethality. For neratinib with [pazopanib + entinostat], this effect correlated with reduced phosphorylation and expression of ERBB1, ERBB2, c-KIT, and c-MET and reduced expression, regardless of mutational status, of N-RAS and K-RAS. [Pazopanib + entinostat + neratinib] reduced the phosphorylation of the Hippo pathway proteins MST1/3/4 and MOB1 whereas this treatment increased the phosphorylation of LATS1, YAP, and TAZ. The activation of ATM, ULK-1, and eIF2α was further enhanced by [pazopanib + entinostat + neratinib] as was the expression of ATG5 and Beclin1. Compared to other manipulations, knock down of eIF2α or over-expression of BCL-XL significantly reduced killing by the three-drug interaction. In vivo, pazopanib and entinostat, and also neratinib and entinostat, both combined to significantly suppress the growth of sarcoma tumors.

Clinical and biological implications of Hippo pathway dysregulation in sarcomas

Sarcomas are mesenchymal malignant tumors with poor prognosis and limited treatment options. Hippo pathway is a recently discovered pathway normally involved in organ development and wound healing. Hippo signaling is often altered in solid tumors. The molecular elements of Hippo signaling include MST1/2 and LATS1/2 kinases which phosphorylate and regulate the activity of YAP and TAZ co-transcriptional activators. Hippo pathway cross-talks with several molecular pathways with known oncogenic function. In sarcomas Hippo signaling plays a pivotal role in tumorigenesis, evolution and resistance in chemotherapy regimens. Targeting Hippo pathway could potentially improve prognosis and outcome of sarcoma patients.

The Hippo Pathway in Prostate Cancer

Despite recent efforts, prostate cancer (PCa) remains one of the most common cancers in men. Currently, there is no effective treatment for castration-resistant prostate cancer (CRPC). There is, therefore, an urgent need to identify new therapeutic targets. The Hippo pathway and its downstream effectors—the transcriptional co-activators, Yes-associated protein (YAP) and its paralog, transcriptional co-activator with PDZ-binding motif (TAZ)—are foremost regulators of stem cells and cancer biology. Defective Hippo pathway signaling and YAP/TAZ hyperactivation are common across various cancers. Here, we draw on insights learned from other types of cancers and review the latest advances linking the Hippo pathway and YAP/TAZ to PCa onset and progression. We examine the regulatory interaction between Hippo-YAP/TAZ and the androgen receptor (AR), as main regulators of PCa development, and how uncontrolled expression of YAP/TAZ drives castration resistance by inducing cellular stemness. Finally, we survey the potential therapeutic targeting of the Hippo pathway and YAP/TAZ to overcome PCa.

Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and represents a high-grade neoplasm of skeletal myoblast-like cells. Decades of clinical and basic research have gradually improved our understanding of the pathophysiology of RMS and helped to optimize clinical care. The two major subtypes of RMS, originally characterized on the basis of light microscopic features, are driven by fundamentally different molecular mechanisms and pose distinct clinical challenges. Curative therapy depends on control of the primary tumour, which can arise at many distinct anatomical sites, as well as controlling disseminated disease that is known or assumed to be present in every case. Sophisticated risk stratification for children with RMS incorporates various clinical, pathological and molecular features, and that information is used to guide the application of multifaceted therapy. Such therapy has historically included cytotoxic chemotherapy as well as surgery, ionizing radiation or both. This Primer describes our current understanding of RMS epidemiology, disease susceptibility factors, disease mechanisms and elements of clinical care, including diagnostics, risk-based care of newly diagnosed and relapsed disease and the prevention and management of late effects in survivors. We also outline potential opportunities to further translate new biological insights into improved clinical outcomes.

Analysis of the relationship between the KRAS G12V oncogene and the Hippo effector YAP1 in embryonal rhabdomyosarcoma

Persistent hyperactivity of the Hippo effector YAP in activated satellite cells is sufficient to cause embryonal rhabdomyosarcoma (ERMS) in mice. In humans, YAP is abundant and nuclear in the majority of ERMS cases, and high YAP expression is associated with poor survival. However, YAP1 is rarely mutated in human ERMS. Instead, the most common mutations in ERMS are oncogenic RAS mutations. First, to compare YAP1S127A and KRASG12V-driven rhabdomyosarcomas, we re-analysed gene expression microarray datasets from mouse rhabdomyosarcomas caused by these genes. This revealed that only 20% of the up or downregulated genes are identical, suggesting substantial differences in gene expression between YAP and KRAS-driven rhabdomyosarcomas. As oncogenic RAS has been linked to YAP in other types of cancer, we also tested whether KRAS G12V alone or in combination with loss of p53 and p16 activates YAP in myoblasts. We found that neither KRAS G12V alone nor KRAS G12V combined with loss of p53 and p16 activated Yap or Yap/Taz-Tead1–4 transcriptional activity in C2C12 myoblasts or U57810 cells. In conclusion, whilst oncogenic KRAS mutation might activate Yap in other cell types, we could find no evidence for this in myoblasts because the expression of KRAS G12V expression did not change Yap/Taz activity in myoblasts and there was a limited overlap in gene expression between KRAS G12V and YAP1 S127A-driven tumours.

A comprehensive evaluation of Hippo pathway silencing in sarcomas

TAZ and YAP are transcriptional coactivators negatively regulated by the Hippo pathway that have emerged as key oncoproteins in several cancers including sarcomas. We hypothesized that loss of expression of the Hippo kinases might be a mechanism of activating TAZ and YAP. By immunohistochemistry, TAZ/YAP activated clinical sarcoma samples demonstrated loss of MST1 (47%), MST2 (26%), LATS1 (19%), and LATS2 (27%). Western blot similarly demonstrated loss of MST1 (58%), MST2 (25%), and LATS2 (17%). Treatment with MG132 demonstrated an accumulation of MST2 in 25% of sarcoma cell lines, indicating that proteosomal degradation regulates MST2 expression. qRT-PCR in sarcoma cell lines demonstrated loss of expression of the Hippo kinases at the RNA level, most pronounced in MST1 (42%) and MST2 (25%). 5-azacytidine treatment in sarcoma cell lines modestly reversed expression of predominantly MST1 (8%) and MST2 (17%), indicating CpG island hypermethylation can silence expression of MST1 and MST2. Trichostatin A treatment reversed expression of MST1 (58%) and MST2 (67%), indicating histone deacetylation also plays a role in silencing expression of MST1 and MST2. Loss of expression of the Hippo kinases is frequent in sarcomas and is due to a variety of mechanisms including regulation at the post-translational level and epigenetic silencing.

Potential Value of YAP Staining in Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a common malignancy of soft tissue, subclassified as alveolar (ARMS), pleomorphic (PRMS), spindle cell/sclerosing (SRMS), and embryonal (ERMS) types. The Yes-associated protein (YAP) is a member of the Hippo pathway and a transcriptional regulator that controls cell proliferation. We have studied the immunohistochemical expression of YAP in different RMSs, arranged in tissue microarray (TMA) and whole slide formats. Pertinent clinical data including patient age, gender, tumor location, and clinical stage were collected. Out of 96 TMA cases, 30 cases (31%) were pleomorphic, 27 (28%) were embryonal, 24 (25%) alveolar, and 15 (16%) spindle cell. Positive nuclear YAP staining was seen in the PRMS (17/30, 56.7%), SRMS (7/15, 46.7%), ERMS (19/27 or 70%), and less in ARMS (37.5%). YAP nuclear staining was significantly more prevalent in ERMS than ARMS ( p=0.02). Of the 41 whole slide cases, nuclear staining was detected in all ARMS but was restricted in distribution to <30% of the cells, in contrast to ERMS and SRMS, which had diffuse or >30% staining. These results highlight the role of YAP in RMS tumorigenesis, a fact that can be useful in engineering targeted therapy. Restricted nuclear YAP staining (<30% of cells) may be of value in the diagnosis of ARMS.

Epithelioid Hemangioendothelioma as a Model of YAP/TAZ-Driven Cancer: Insights from a Rare Fusion Sarcoma

Epithelioid hemangioendothelioma (EHE) is a rare soft-tissue sarcoma involving cells with histologic markers that suggest an endothelial origin. Around 90% of EHEs are caused by the fusion of Transcriptional Co-activator with a PDZ-motif (TAZ) with Calmodulin Binding Transcription Activator 1 (CAMTA1), a central nervous system-specific transcription activator. The 10% of EHEs that lack the TAZ–CAMTA1 fusion instead have a fusion of Yes-associated Protein (YAP) and Transcription Factor E3 (TFE3) genes (YAP-TFE3). YAP and TAZ are well-defined downstream effectors in the Hippo pathway that promote cell growth when translocated to the nucleus. The TAZ–CAMTA1 fusion transcript is insensitive to the Hippo inhibitory signals that normally prevent this process and thus constitutively activates the TAZ transcriptome. In EHE, this causes tumors to form in a variety of organs and tissue types, most commonly the liver, lung, and bone. Its clinical course is unpredictable and highly variable. TAZ activation is known to contribute to key aspects of the cancer phenotype, including metastasis and fibrosis, and increased expression of TAZ is thought to be causally related to the progression of many cancers, including breast, lung, and liver. Therefore, understanding TAZ biology and the molecular mechanisms by which it promotes unregulated cell proliferation will yield insights and possibly improved treatments for both EHE as well as much more common cancers.

TAZ induces lung cancer stem cell properties and tumorigenesis by up-regulating ALDH1A1

Recent studies suggest that lung cancer stem cells (CSCs) may play major roles in lung cancer. Therefore, identification of lung CSC drivers may provide promising targets for lung cancer. TAZ is a transcriptional co-activator and key downstream effector of the Hippo pathway, which plays critical roles in various biological processes. TAZ has been shown to be overexpressed in lung cancer and involved in tumorigenicity of lung epithelial cells. However, whether TAZ is a driver for lung CSCs and tumor formation in vivo is unknown. In addition, the molecular mechanism underlying TAZ-induced lung tumorigenesis remains to be determined. In this study, we provided evidence that constitutively active TAZ (TAZ-S89A) is a driver for lung tumorigenesis in vivo in mice and formation of lung CSC. Further RNA-seq and qRT-PCR analysis identified Aldh1a1, a well-established CSC marker, as critical TAZ downstream target and showed that TAZ induces Aldh1a1 transcription by activating its promoter activity through interaction with the transcription factor TEAD. Most significantly, inhibition of ALDH1A1 with its inhibitor A37 or CRISPR gene knockout in lung cancer cells suppressed lung tumorigenic and CSC phenotypes in vitro, and tumor formation in mice in vivo. In conclusion, this study identified TAZ as a novel inducer of lung CSCs and the first transcriptional activator of the stem cell marker ALDH1A1. Most significantly, we identified ALDH1A1 as a critical meditator of TAZ-induced tumorigenic and CSC phenotypes in lung cancer. Our studies provided preclinical data for targeting of TAZ-TEAD-ALDH1A1 signaling to inhibit CSC-induced lung tumorigenesis in the future.

Survivin: A novel marker and potential therapeutic target for human angiosarcoma

Human angiosarcoma is a rare malignant vascular tumor associated with extremely poor clinical outcome and generally arising in skin of the head and neck region. However, little is known about the molecular pathogeneses and useful immunohistochemical markers of angiosarcoma. To investigate the mechanisms of angiosarcoma progression, we collected 85 cases of human angiosarcoma specimens with clinical records and analyzed ISO-HAS-B patient-derived angiosarcoma cells. As control subjects, 54 cases of hemangioma and 34 of pyogenic granuloma were collected. Remarkably, consistent with our recent observations regarding the involvement of survivin expression following Hippo pathway inactivation in the neoplastic proliferation of murine hemangioendothelioma cells and human infantile hemangioma, nuclear survivin expression was observed in all cases of angiosarcoma but not in hemangiomas and pyogenic granulomas, and the Hippo pathway was inactivated in 90.3% of yes-associated protein (YAP) -positive angiosarcoma cases. However, survivin expression modes and YAP localization (Hippo pathway activation modes) were not correlated with survival. In addition, we confirmed that survivin small interference RNA (siRNA) transfection and YM155, an anti-survivin drug, elicited decreased nuclear survivin expression and cell proliferation in ISO-HAS-B cells which expressed survivin consistently. Conclusively, these findings support the importance of survivin as a good marker and critical regulator of cellular proliferation for human angiosarcoma and YM155 as a potential therapeutic agent.

The Hippo effector TAZ (WWTR1) transforms myoblasts and TAZ abundance is associated with reduced survival in embryonal rhabdomyosarcoma

The Hippo effector YAP has recently been identified as a potent driver of embryonal rhabdomyosarcoma (ERMS). Most reports suggest that the YAP paralogue TAZ (gene symbol WWTR1) functions as YAP but, in skeletal muscle, TAZ has been reported to promote myogenic differentiation, whereas YAP inhibits it. Here, we investigated whether TAZ is also a rhabdomyosarcoma oncogene or whether TAZ acts as a YAP antagonist. Immunostaining of rhabdomyosarcoma tissue microarrays revealed that TAZ is significantly associated with poor survival in ERMS. In 12% of fusion gene‐negative rhabdomyosarcomas, the TAZ locus is gained, which is correlated with increased expression. Constitutively active TAZ S89A significantly increased proliferation of C2C12 myoblasts and, importantly, colony formation on soft agar, suggesting transformation. However, TAZ then switches to enhance myogenic differentiation in C2C12 myoblasts, unlike YAP. Conversely, lentiviral shRNA‐mediated TAZ knockdown in human ERMS cells reduced proliferation and anchorage‐independent growth. While TAZ S89A or YAP1 S127A similarly activated the 8XGTIIC–Luc Hippo reporter, only YAP1 S127A activated the Brachyury (T‐box) reporter. Consistent with its oncogene function, TAZ S89A induced expression of the ERMS cancer stem cell gene Myf5 and the serine biosynthesis pathway (Phgdh, Psat1, Psph) in C2C12 myoblasts. Thus, TAZ is associated with poor survival in ERMS and could act as an oncogene in rhabdomyosarcoma. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

YAP and the Hippo pathway in pediatric cancer

The Hippo pathway is an important signaling pathway that controls cell proliferation and apoptosis. It is evolutionarily conserved in mammals and is stimulated by cell-cell contact, inhibiting cell proliferation in response to increased cell density. During early embryonic development, the Hippo signaling pathway regulates organ development and size, and its functions result in the coordinated balance between proliferation, apoptosis, and differentiation. Its principal effectors, YAP and TAZ, regulate signaling by the embryonic stem cells and determine cell fate and histogenesis. Dysfunction of this pathway contributes to cancer development in adults and children. Emerging studies have shed light on the upregulation of Hippo pathway members in several pediatric cancers and may offer prognostic information on rhabdomyosarcoma, osteosarcoma, Wilms tumor, neuroblastoma, medulloblastoma, and other brain gliomas. We review the results of such published studies and highlight the potential clinical application of this pathway in pediatric oncologic and pathologic studies. These studies support targeting this pathway as a novel treatment strategy.

Effect of cytostatic proline rich polypeptide-1 on tumor suppressors of inflammation pathway signaling in chondrosarcoma

Cytokines produced in the tumour microenvironment exert an important role in cancer pathogenesis and in the inhibition of disease progression. Cancer of the cartilage is termed metastatic chondrosarcoma; however, the signaling events resulting in mesenchymal cell transformation to sarcoma have yet to be fully elucidated. The present study aimed to characterize the cytokine expression profile in the human JJ012 chondrosarcoma cell line, as well as the effect of cytostatic proline-rich polypeptide-1 (PRP-1). Western blot experiments demonstrated that the levels of suppressor of cytokine signaling 3 (SOCS3) were upregulated in chondrocytes compared with chondrosarcoma cells. Addition of PRP-1 restored the expression of the tumor suppressors, SOCS3 and ten-eleven-translocation methylcytosine dioxygenase 1 and 2 (TET1/2), in a dose-responsive manner. It is known that methylation of histone H3K9 was eliminated from the promoters of the inflammation-associated genes. PRP-1 inhibited H3K9 demethylase activity with an IC₅₀ (concentration required to give half-maximal inhibition) value of 3.72 µg/ml in the chondrosarcoma cell line. Data obtained from ELISA experiments indicated that the expression of interleukin-6 (IL-6) in chondrosarcoma cells was 86-fold lower compared with that in C28 chondrocytes. In the present study, a 53-fold downregulation of IL-6 expression in co-culture of chondrosarcoma cells and C28 chondrocytes was identified as well. Downregulation of IL-6 expression has been documented in numerous other tumor types, although the reasons for this have not been fully established. In chondrosarcoma, IL-6 manifests itself as an anti-inflammatory agent and, possibly, as an anti-tumorigenic factor. To explore protein-DNA interactions leading to such differences, a gel-shift chemiluminescent assay was performed. Gel shifts were observed for chondrosarcoma and chondrocytes in the lanes that contained nuclear cell extract and oligo-IL-6 DNA. Notably, the DNA-protein complexes in C28 chondrocytes were markedly larger compared with those in chondrosarcoma cells. The mechanisms that underpin such differences, and characterization of the interacting proteins, remain to be fully elucidated.

Expanding the molecular signature of ossifying fibromyxoid tumors with two novel gene fusions: CREBBP-BCORL1 and KDM2A-WWTR1

Ossifying fibromyxoid tumor (OFMT) is an uncommon mesenchymal neoplasm of uncertain differentiation and intermediate malignant potential. Recurrent gene fusions involving either PHF1 or BCOR have been found in 85% of OFMT, including typical and malignant examples. As a subset of OFMT still lack known genetic abnormalities, we identified two OFMTs negative for PHF1 and BCOR rearrangements, which were subjected to transcriptome analysis for fusion discovery. The RNA sequencing found a novel CREBBP-BCORL1 fusion candidate in an axillary mass of a 51 year-old male and a KDM2A-WWTR1 in a thigh mass of a 36 year-old male. The gene fusions were validated by RT-PCR and FISH in the index cases and then screened by FISH on 4 additional OFMTs lacking known fusions. An identical CREBBP-BCORL1 fusion was found in an elbow tumor from a 30 year-old male. Both OFMTs with CREBBP-BCORL1 fusions had areas of typical OFMT morphology, exhibiting uniform round to epithelioid cells arranged in cords or nesting pattern in a fibromyxoid stroma. The OFMT with KDM2A-WWTR1 fusion involved dermis and superficial subcutis, being composed of ovoid cells in a fibromyxoid background with hyalinized giant rosettes. The S100 immunoreactivity ranged from very focal to absent. Similar to other known fusion genes in OFMT, BCORL1, CREBBP and KDM2A are also involved in histone modification. In summary, we expand the spectrum of molecular abnormalities in OFMT with 2 novel fusions, CREBBP-BCORL1 and KDM2A-WWTR1, further implicating the epigenetic deregulation as the leading pathogenetic mechanism in OFMT. © 2016 Wiley Periodicals, Inc.

Genomic characterization of esophageal squamous cell carcinoma: Insights from next-generation sequencing

Two major types of cancer occur in the esophagus: squamous cell carcinoma, which is associated with chronic smoking and alcohol consumption, and adenocarcinoma, which typically arises in gastric reflux-associated Barrett’s esophagus. Although there is increasing incidence of esophageal adenocarcinoma in Western counties, esophageal squamous cell carcinoma (ESCC) accounts for most esophageal malignancies in East Asia, including China and Japan. Technological advances allowing for massively parallel, high-throughput next-generation sequencing (NGS) of DNA have enabled comprehensive characterization of somatic mutations in large numbers of tumor samples. Recently, several studies were published in which whole exome or whole genome sequencing was performed in ESCC tumors and compared with matched normal DNA. Mutations were validated in several genes, including in TP53, CDKN2A, FAT1, NOTCH1, PIK3CA, KMT2D and NFE2L2, which had been previously implicated in ESCC. Several new recurrent alterations have also been identified in ESCC. Combining the clinicopathological characteristics of patients with information obtained from NGS studies may lead to the development of effective diagnostic and therapeutic approaches for ESCC. As this research becomes more prominent, it is important that gastroenterologist become familiar with the various NGS technologies and the results generated using these methods. In the present study, we describe recent research approaches using NGS in ESCC.

The Hippo pathway effectors YAP and TAZ promote cell growth by modulating amino acid signaling to mTORC1

YAP and TAZ are transcriptional co-activators and function as the major effectors of the Hippo tumor suppressor pathway, which controls cell growth, tissue homeostasis, and organ size. Here we show that YAP/TAZ play an essential role in amino acid-induced mTORC1 activation, particularly under nutrient-limiting conditions. Mechanistically, YAP/TAZ act via the TEAD transcription factors to induce expression of the high-affinity leucine transporter LAT1, which is a heterodimeric complex of SLC7A5 and SLC3A2. Deletion of YAP/TAZ abolishes expression of LAT1 and reduces leucine uptake. Re-expression of SLC7A5 in YAP/TAZ knockout cells restores leucine uptake and mTORC1 activation. Moreover, SLC7A5 knockout cells phenocopies YAP/TAZ knockout cells which exhibit defective mTORC1 activation in response to amino acids. We further demonstrate that YAP/TAZ act through SLC7A5 to provide cells with a competitive growth advantage. Our study provides molecular insight into the mechanism of YAP/TAZ target genes in cell growth regulation.