Prevalence of the Hippo Effectors YAP1/TAZ in Tumors of Soft Tissue and Bone

Vasculature is getting Hip(po): Hippo signaling in vascular development and disease

The Hippo signaling pathway regulates developmental organ growth, regeneration, and cell fate decisions. Although the role of the Hippo pathway, and its transcriptional effectors YAP and TAZ, has been well documented in many cell types and species, only recently have the roles for this pathway come to light in vascular development and disease. Experiments in mice, zebrafish, and in vitro have uncovered roles for the Hippo pathway, YAP, and TAZ in vasculogenesis, angiogenesis, and lymphangiogenesis. In addition, the Hippo pathway has been implicated in vascular cancers and cardiovascular diseases, thus identifying it as a potential therapeutic target for the treatment of these conditions. However, despite recent advances, Hippo's role in the vasculature is still underappreciated compared with its role in epithelial tissues. In this review, we appraise our current understanding of the Hippo pathway in blood and lymphatic vessel development and highlight the current knowledge gaps and opportunities for further research.

The spectrum and significance of secondary (co-occurring) genetic alterations in sarcomas: the hallmarks of sarcomagenesis

Bone and soft tissue tumors are generally classified into complex karyotype sarcomas versus those with recurrent genetic alterations, often in the form of gene fusions. In this review, we provide an overview of important co-occurring genomic alterations, organized by biological mechanisms and covering a spectrum of genomic alteration types: mutations (single-nucleotide variations or indels) in oncogenes or tumor suppressor genes, copy number alterations, transcriptomic signatures, genomic complexity indices (e.g. CINSARC), and complex genomic structural variants. We discuss the biological and prognostic roles of these so-called secondary or co-occurring alterations, arguing that recognition and detection of these alterations may be significant for our understanding and management of mesenchymal tumors. On a related note, we also discuss major recurrent alterations in so-called complex karyotype sarcomas. These secondary alterations are essential to sarcomagenesis via a variety of mechanisms, such as inactivation of tumor suppressors, activation of proliferative signal transduction, telomere maintenance, and aberrant regulation of epigenomic/chromatin remodeling players. The use of comprehensive genomic profiling, including targeted next-generation sequencing panels or whole-exome sequencing, may be incorporated into clinical workflows to offer more comprehensive, potentially clinically actionable information. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

YAP/TAZ as master regulators in cancer: modulation, function and therapeutic approaches

Our understanding of the function of the transcriptional regulators YAP and TAZ (YAP/TAZ) in cancer is advancing. In this Review, we provide an update on recent progress in YAP/TAZ biology, their regulation by Hippo signaling and mechanotransduction and highlight open questions. YAP/TAZ signaling is an addiction shared by multiple tumor types and their microenvironments, providing many malignant attributes. As such, it represents an important vulnerability that may offer a broad window of therapeutic efficacy, and here we give an overview of the current treatment strategies and pioneering clinical trials.

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.

Total-Body Irradiation Is Associated With Increased Incidence of Mesenchymal Neoplasia in a Radiation Late Effects Cohort of Rhesus Macaques (Macaca mulatta)

PURPOSE

Cancer is a severe delayed effect of acute radiation exposure. Total-body irradiation has been associated with an increased risk of solid cancer and leukemia in Japanese atomic bomb survivors, and secondary malignancies, such as sarcoma, are a serious consequence of cancer radiation therapy. The radiation late effects cohort (RLEC) of rhesus macaques (Macaca mulatta) is a unique resource of more than 200 animals for studying the long-term consequences of total-body irradiation in an animal model that closely resembles humans at the genetic and physiologic levels.

METHODS AND MATERIALS

Using clinical records, clinical imaging, histopathology, and immunohistochemistry, this retrospective study characterized the incidence of neoplasia in the RLEC.

RESULTS

Since 2007, 61 neoplasms in 44 of 239 irradiated animals were documented (18.4% of the irradiated population). Only 1 neoplasm was diagnosed among the 51 nonirradiated controls of the RLEC (2.0%). The most common malignancies in the RLEC were sarcomas (38.3% of diagnoses), which are rare neoplasms in nonirradiated macaques. The most common sarcomas included malignant nerve sheath tumors and malignant glomus tumors. Carcinomas were less common (19.7% of diagnoses), and consisted primarily of renal cell and hepatocellular carcinomas. Neoplasia occurred in most major body systems, with the skin and subcutis being the most common site (40%). RNA analysis showed similarities in transcriptional profiles between RLEC and human malignant nerve sheath tumors.

CONCLUSIONS

This study indicates that total-body irradiation is associated with an increased incidence of neoplasia years following irradiation, at more than double the incidence described in aging, nonirradiated animals, and promotes tumor histotypes that are rarely observed in nonirradiated, aging rhesus macaques.

Mice with Trp53 and Rb1 deficiency in chondrocytes spontaneously develop chondrosarcoma via overactivation of YAP signaling

Chondrosarcoma (CHS) is a rare type of soft sarcoma with increased production of cartilage matrix arising from soft bone tissues. Currently, surgical resection is the primary clinical treatment for chondrosarcoma due to the poor response to radiotherapy and chemotherapy. However, the therapeutic effect is not satisfactory due to the higher local recurrence rate. Thus, management and elucidation of the pathological mechanism of chondrosarcoma remain an ongoing challenge, and the development of effective chondrosarcoma mouse models and treatment options are urgently needed. Here, we generated a new transgenic chondrosarcoma model by double conditional deletions of Trp53 and Rb1 in chondrocyte lineage which spontaneously caused spinal chondrosarcoma and lung metastasis. Bioinformatic analysis of the human soft sarcoma database showed that Trp53 and Rb1 genes had higher mutations, reaching up to approximately 33.5% and 8.7%, respectively. Additionally, Trp53 and Rb1 signatures were decreased in the human and mouse chondrosarcoma tissues. Mechanistically, we found that YAP expression and activity were significantly increased in mouse Col2-Cre;Trp53f/f/Rb1f/f chondrosarcoma tissues compared to the adjacent normal cartilage. Knockdown of YAP in primary chondrosarcoma cells significantly inhibited chondrosarcoma proliferation, invasion, and tumorsphere formation. Chondrocyte lineage ablation of YAP delayed chondrosarcoma progression and lung metastasis in Col2-Cre;Trp53f/f/Rb1f/f mice. Moreover, we found that metformin served as a YAP inhibitor, which bound to the activity area of YAP protein, and inhibited chondrosarcoma cell proliferation, migration, invasion, and progression in vitro and significantly suppressed chondrosarcoma formation in vivo. Collectively, this study identifies the inhibition of YAP may be an effective therapeutic strategy for the treatment of chondrosarcoma.

Fusion protein-driven IGF-IR/PI3K/AKT signals deregulate Hippo pathway promoting oncogenic cooperation of YAP1 and FUS-DDIT3 in myxoid liposarcoma

Myxoid liposarcoma (MLS) represents a common subtype of liposarcoma molecularly characterized by a recurrent chromosomal translocation that generates a chimeric FUS-DDIT3 fusion gene. The FUS-DDIT3 oncoprotein has been shown to be crucial in MLS pathogenesis. Acting as a transcriptional dysregulator, FUS-DDIT3 stimulates proliferation and interferes with adipogenic differentiation. As the fusion protein represents a therapeutically challenging target, a profound understanding of MLS biology is elementary to uncover FUS-DDIT3-dependent molecular vulnerabilities. Recently, a specific reliance on the Hippo pathway effector and transcriptional co-regulator YAP1 was detected in MLS; however, details on the molecular mechanism of FUS-DDIT3-dependent YAP1 activation, and YAP1´s precise mode of action remain unclear. In elaborate in vitro studies, employing RNA interference-based approaches, small-molecule inhibitors, and stimulation experiments with IGF-II, we show that FUS-DDIT3-driven IGF-IR/PI3K/AKT signaling promotes stability and nuclear accumulation of YAP1 via deregulation of the Hippo pathway. Co-immunoprecipitation and proximity ligation assays revealed nuclear co-localization of FUS-DDIT3 and YAP1/TEAD in FUS-DDIT3-expressing mesenchymal stem cells and MLS cell lines. Transcriptome sequencing of MLS cells demonstrated that FUS-DDIT3 and YAP1 co-regulate oncogenic gene signatures related to proliferation, cell cycle progression, apoptosis, and adipogenesis. In adipogenic differentiation assays, we show that YAP1 critically contributes to FUS-DDIT3-mediated adipogenic differentiation arrest. Taken together, our study provides mechanistic insights into a complex FUS-DDIT3-driven network involving IGF-IR/PI3K/AKT signals acting on Hippo/YAP1, and uncovers substantial cooperative effects of YAP1 and FUS-DDIT3 in the pathogenesis of MLS.

Malignant peripheral nerve sheath tumor: models, biology, and translation

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive, invasive cancer that comprise around 10% of all soft tissue sarcomas and develop in about 8-13% of patients with Neurofibromatosis Type 1. They are associated with poor prognosis and are the leading cause of mortality in NF1 patients. MPNSTs can also develop sporadically or following exposure to radiation. There is currently no effective targeted therapy to treat MPNSTs and surgical removal remains the mainstay treatment. Unfortunately, surgery is not always possible due to the size and location of the tumor, thus, a better understanding of MPNST initiation and development is required to design novel therapeutics. Here, we provide an overview of MPNST biology and genetics, discuss findings regarding the developmental origin of MPNST, and summarize the various model systems employed to study MPNST. Finally, we discuss current management strategies for MPNST, as well as recent developments in translating basic research findings into potential therapies.

Oligosarcomas, IDH-mutant are distinct and aggressive

Oligodendrogliomas are defined at the molecular level by the presence of an IDH mutation and codeletion of chromosomal arms 1p and 19q. In the past, case reports and small studies described gliomas with sarcomatous features arising from oligodendrogliomas, so called oligosarcomas. Here, we report a series of 24 IDH-mutant oligosarcomas from 23 patients forming a distinct methylation class. The tumors were recurrences from prior oligodendrogliomas or developed de novo. Precursor tumors of 12 oligosarcomas were histologically and molecularly indistinguishable from conventional oligodendrogliomas. Oligosarcoma tumor cells were embedded in a dense network of reticulin fibers, frequently showing p53 accumulation, positivity for SMA and CALD1, loss of OLIG2 and gain of H3K27 trimethylation (H3K27me3) as compared to primary lesions. In 5 oligosarcomas no 1p/19q codeletion was detectable, although it was present in the primary lesions. Copy number neutral LOH was determined as underlying mechanism. Oligosarcomas harbored an increased chromosomal copy number variation load with frequent CDKN2A/B deletions. Proteomic profiling demonstrated oligosarcomas to be highly distinct from conventional CNS WHO grade 3 oligodendrogliomas with consistent evidence for a smooth muscle differentiation. Expression of several tumor suppressors was reduced with NF1 being lost frequently. In contrast, oncogenic YAP1 was aberrantly overexpressed in oligosarcomas. Panel sequencing revealed mutations in NF1 and TP53 along with IDH1/2 and TERT promoter mutations. Survival of patients was significantly poorer for oligosarcomas as first recurrence than for grade 3 oligodendrogliomas as first recurrence. These results establish oligosarcomas as a distinct group of IDH-mutant gliomas differing from conventional oligodendrogliomas on the histologic, epigenetic, proteomic, molecular and clinical level. The diagnosis can be based on the combined presence of (a) sarcomatous histology, (b) IDH-mutation and (c) TERT promoter mutation and/or 1p/19q codeletion, or, in unresolved cases, on its characteristic DNA methylation profile.

Berberine for bone regeneration: Therapeutic potential and molecular mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Berberine is a quaternary ammonium isoquinoline alkaloid, mainly extracted from plants berberaceae, papaveraceae, ranunculaceae and rutaceae such as coptis chinensis Franch, Phellodendron chinense, and berberis pruinosa. The plants are extensively used in traditional medicine for treating infection, diabetes, arrhythmia, tumor, osteoporosis et al. Pharmacological studies showed berberine has effects of anti-inflammation, anti-tumor, lower blood lipid, lower blood glucose, anti-osteoporosis, anti-osteoarthritis et al. AIM OF THE STUDY: This review aims to summarize the application of natural herbs that contain berberine, the further use and development of berberine, the effects as well as mechanism of berberine on osteoblasts and osteoclasts, the recent advances of in vivo studies, in order to provide a scientific basis for its traditional uses and to prospect of the potential applications of berberine in clinics.

METHOD

The research was achieved by retrieving from the online electronic database, including PubMed, Web of Science, Google Scholar and China national knowledge infrastructure (CNKI). Patents, doctoral dissertations and master dissertations are also searched.

RESULTS

Berberine has a long history of medicinal use to treat various diseases including bone disease in China. Recent studies have defined its function in promoting bone regeneration and great potential in developing new drugs. But the systemic mechanism of berberine on bone regeneration still needs more research to clarify.

CONCLUSION

This review has systematically summarized the application, pharmacological effects, mechanism as well as in vivo studies of berberine and herbs which contain berberine. Berberine has a definite effect in promoting the proliferation and differentiation of osteoblasts as well as inhibiting the production of osteoclasts to promote bone regeneration. However, the present studies about the system mechanisms and pharmacological activity of berberine were incomplete. Applying berberine for new drug development remains an exciting and promising alternative to bone regeneration engineering, with broad potential for therapeutic and clinical practice.

The chorioallantoic membrane as a bio-barrier model for the evaluation of nanoscale drug delivery systems for tumour therapy

In 2010, the European Parliament and the European Union adopted a directive on the protection of animals used for scientific purposes. The directive aims to protect animals in scientific research, with the final goal of complete replacement of procedures on live animals for scientific and educational purposes as soon as it is scientifically viable. Furthermore, the directive announces the implementation of the 3Rs principle: "When choosing methods, the principles of replacement, reduction and refinement should be implemented through a strict hierarchy of the requirement to use alternative methods." The visibility, accessibility, and the rapid growth of the chorioallantoic membrane (CAM) offers a clear advantage for various manipulations and for the simulation of different Bio-Barriers according to the 3R principle. The extensive vascularisation on the CAM provides an excellent substrate for the cultivation of tumour cells or tumour xenografts which could be used for the therapeutic evaluation of nanoscale drug delivery systems. The tumour can be targeted either by topical application, intratumoural injection or i.v. injection. Different application sites and biological barriers can be examined within a single model.

TAZ-CAMTA1 and YAP-TFE3 alter the TAZ/YAP transcriptome by recruiting the ATAC histone acetyltransferase complex

Epithelioid hemangioendothelioma (EHE) is a vascular sarcoma that metastasizes early in its clinical course and lacks an effective medical therapy. The TAZ-CAMTA1 and YAP-TFE3 fusion proteins are chimeric transcription factors and initiating oncogenic drivers of EHE. A combined proteomic/genetic screen in human cell lines identified YEATS2 and ZZZ3, components of the Ada2a-containing histone acetyltransferase (ATAC) complex, as key interactors of both fusion proteins despite the dissimilarity of the C terminal fusion partners CAMTA1 and TFE3. Integrative next-generation sequencing approaches in human and murine cell lines showed that the fusion proteins drive a unique transcriptome by simultaneously hyperactivating a TEAD-based transcriptional program and modulating the chromatin environment via interaction with the ATAC complex. Interaction of the ATAC complex with both fusion proteins indicates that it is a key oncogenic driver and unifying enzymatic therapeutic target for this sarcoma. This study presents an approach to mechanistically dissect how chimeric transcription factors drive the formation of human cancers.

The proliferation of human cells is tightly regulated to ensure that enough cells are made to build and repair organs and tissues, while at the same time stopping cells from dividing uncontrollably and damaging the body. To get the right balance, cells rely on physical and chemical cues from their environment that trigger the biochemical signals that regulate two proteins called TAZ and YAP. These proteins control gene activity by regulating the rate at which genes are copied to produce proteins. If this process becomes dysregulated, cells can grow uncontrollably, causing cancer.

In cancer cells, it is common to find TAZ and YAP fused to other proteins. In epithelioid hemangioendothelioma, a rare cancer that grows in the blood vessels, cancerous growth can be driven by a version of TAZ fused to the protein CAMTA1, or a version of YAP fused to the protein TFE3. While the role of TAZ and YAP in promoting gene activity is known, it is unclear how CAMTA1 and TFE3 contribute to cell growth becoming dysregulated.

Merritt, Garcia et al. studied sarcoma cell lines to show that these two fusion proteins, TAZ-CAMTA1 and YAP-TFE3, change the pattern of gene activity seen in the cells compared to TAZ or YAP alone. An analysis of molecules that interact with the two fusion proteins identified a complex called ATAC as the cause of these changes. This complex adds chemical markers to DNA-packaging proteins, which control which genes are available for activation. The fusion proteins combine the ability of TAZ and YAP to control gene activity and the ability of CAMTA1 and TFE3 to make DNA more accessible, allowing the fusion proteins to drive uncontrolled cancerous growth.

Similar TAZ and YAP fusion proteins have been found in other cancers, which can activate genes and potentially alter DNA packaging. Targeting drug development efforts at the proteins that complex with TAZ and YAP fusion proteins may lead to new therapies.

Prognostic and therapeutic value of the Hippo pathway, RABL6A, and p53-MDM2 axes in sarcomas

Additional prognostic and therapeutic biomarkers effective across different histological types of sarcoma are needed. Herein we evaluate expression of TAZ and YAP, the p53-MDM2 axis, and RABL6A, a novel oncoprotein with potential ties to both pathways, in sarcomas of different histological types. Immunohistochemical staining of a tissue microarray including 163 sarcomas and correlation with clinical data showed that elevated YAP and TAZ independently predict worse overall and progression-free survival, respectively. In the absence of p53 expression, combined TAZ and YAP expression adversely affect overall, progression free, and metastasis free survival more than TAZ or YAP activation alone. RABL6A independently predicted shorter time to metastasis and was positively correlated with p53, MDM2 and YAP expression, supporting a possible functional relationship between the biomarkers. Network analysis further showed that TAZ is positively correlated with MDM2 expression. The data implicate all five proteins as clinically relevant downstream players in the Hippo pathway. Finally, a novel inhibitor of MDM2 (MA242), effectively suppressed the survival of sarcoma cell lines from different histological types regardless of p53 status. These findings suggest both independent and cooperative roles for all five biomarkers across different histological types of sarcoma in predicting patient outcomes and potentially guiding future therapeutic approaches.

Photodynamic Therapy Using Hippo Pathway Inhibitor Verteporfin: A Potential Dual Mechanistic Approach in Treatment of Soft Tissue Sarcomas

Simple Summary

Advanced sarcomas have yet to undergo improved outcomes seen in other cancer subtypes. Verteporfin has the potential to show landmark change in sarcoma due to its anti-proliferative properties: inhibition of the Hippo pathway and as photodynamic therapy. The effect of verteporfin on the Hippo pathway is reviewed specifically in the setting of sarcoma due to increased activation of this pathway in multiple subtypes. Role and efficacy of photodynamic therapy in other malignancies is also reviewed, with additional discussion of preclinical studies demonstrating synergistic effects of photodynamic therapy within current sarcoma standard of care treatment. Future investigations of the feasibility of incorporating verteporfin into sarcoma treatment are discussed.

Abstract

Sarcoma is a widely varied and devastating oncological subtype, with overall five-year survival of 65% that drops to 16% with the presence of metastatic disease at diagnosis. Standard of care for localized sarcomas is predicated on local control with wide-local resection and radiation therapy, or, less commonly, chemotherapy, depending on tumor subtype. Verteporfin has the potential to be incorporated into this standard of care due to its unique molecular properties: inhibition of the upregulated Hippo pathway that frequently drives soft tissue sarcoma and photodynamic therapy-mediated necrosis due to oxidative damage. The initial anti-proliferative effect of verteporfin is mediated via binding and dissociation of YAP/TEAD proteins from the nucleus, ultimately leading to decreased cell proliferation as demonstrated in multiple in vitro studies. This effect has the potential to be compounded with use of photodynamic therapy to directly induce cellular necrosis with use of a clinical laser. Photodynamic therapy has been incorporated into multiple malignancies and has the potential to be incorporated into sarcoma treatment.

Hippo Signaling Pathway as a Central Mediator of Receptors Tyrosine Kinases (RTKs) in Tumorigenesis

The Hippo pathway plays a critical role in tissue and organ growth under normal physiological conditions, and its dysregulation in malignant growth has made it an attractive target for therapeutic intervention in the fight against cancer. To date, its complex signaling mechanisms have made it difficult to identify strong therapeutic candidates. Hippo signaling is largely carried out by two main activated signaling pathways involving receptor tyrosine kinases (RTKs)—the RTK/RAS/PI3K and the RTK-RAS-MAPK pathways. However, several RTKs have also been shown to regulate this pathway to engage downstream Hippo effectors and ultimately influence cell proliferation. In this text, we attempt to review the diverse RTK signaling pathways that influence Hippo signaling in the context of oncogenesis.