Targeted therapies for advanced Ewing sarcoma family of tumors

Enhanced Antipediatric Sarcoma Effect of Everolimus with Secukinumab by Targeting IL17A

In this study, we explored the therapeutic potential of everolimus, an mTOR inhibitor, in a patient-derived xenograft (PDX) of rhabdomyosarcoma, the most prevalent malignant pediatric sarcoma. In addition, rhabdoid tumor cell line A-204 and Ewings sarcoma cell line A-673 were cultured to assess the in vitro effect of everolimus. Furthermore, the cell-derived xenograft (CDX) of A-673 was established and treated with everolimus in vivo. IHC and Western blotting were performed to detect the expressions of pertinent proteins. Results showed that everolimus intervention had limited inhibitory effect on PDX tumor growth compared with cyclophosphamide. Nevertheless, everolimus treatment significantly influenced the phosphorylation levels of S6 kinase beta 1 (S6K1) and eIF4E-binding protein 1 (p-4E-BP1), resulting in the inhibition of angiogenesis in vitro and in vivo. Interestingly, everolimus led to an upregulation in the level of IL17A in sarcoma cells. Notably, when secukinumab, a mAb of IL17A, was combined with everolimus, it synergistically enhanced the inhibitory effect of everolimus on sarcoma cell proliferation in vitro and on the growth of PDX or CDX xenograft tumors in vivo. Importantly, this combination therapy did not affect the mTOR signaling. These results indicate that everolimus exerts an antipediatric sarcoma effect by inhibiting mTOR signal. However, everolimus induces sarcoma cells to produce IL17A, which promotes tumor cell survival and counteracts its antipediatric sarcoma effect. The combination of secukinumab effectively eliminates the effects of IL17A, thereby improving the therapeutic efficacy of everolimus in the context of pediatric sarcomas.

A Spontaneous Assembling Lipopeptide Nanoconjugate Transporting the Anthracycline Drug N-Benzyladriamycin-14-valerate for Personalized Therapy of Ewing Sarcoma

To meet the current need for a tumor-selective, targeted therapy regimen associated with reduced toxicity, our laboratory has developed a spontaneously assembled nanostructure that resembles high-density lipoproteins (HDLs). These myristoyl-5A (MYR-5A) nanotransporters are designed to safely transport lipophilic pharmaceuticals, including a novel anthracycline drug (N-benzyladriamycin-14-valerate (AD198)). This formulation has been found to enhance the therapeutic efficacy and reduced toxicity of drugs in preclinical studies of 2D and 3D models of Ewing sarcoma (EWS) and cardiomyocytes. Our findings indicate that the MYR-5A/AD198 nanocomplex delivers its payload selectively to cancer cells via the scavenger receptor type B1 (SR-B1), thus providing a solid proof of concept for the development of an improved and highly effective, potentially personalized therapy for EWS while protecting against treatment-associated cardiotoxicity.

DNMT1 determines osteosarcoma cell resistance to apoptosis by associatively modulating DNA and mRNA cytosine-5 methylation

Cellular apoptosis is a central mechanism leveraged by chemotherapy to treat human cancers. 5-Methylcytosine (m5C) modifications installed on both DNA and mRNA are documented to regulate apoptosis independently. However, the interplay or crosstalk between them in cellular apoptosis has not yet been explored. Here, we reported that promoter methylation by DNMT1 coordinated with mRNA methylation by NSun2 to regulate osteosarcoma cell apoptosis. DNMT1 was induced during osteosarcoma cell apoptosis triggered by chemotherapeutic drugs, whereas NSun2 expression was suppressed. DNMT1 was found to repress NSun2 expression by methylating the NSun2 promoter. Moreover, DNMT1 and NSun2 regulate the anti-apoptotic genes AXL, NOTCH2, and YAP1 through DNA and mRNA methylation, respectively. Upon exposure to cisplatin or doxorubicin, DNMT1 elevation drastically reduced the expression of these anti-apoptotic genes via enhanced promoter methylation coupled with NSun2 ablation-mediated attenuation of mRNA methylation, thus rendering osteosarcoma cells to apoptosis. Collectively, our findings establish crosstalk of importance between DNA and RNA cytosine methylations in determining osteosarcoma resistance to apoptosis during chemotherapy, shedding new light on future treatment of osteosarcoma, and adding additional layers to the control of gene expression at different epigenetic levels.

Sacral Ewing sarcoma with rib, lung, and multifocal skull metastases: A rare case report and review of treatments

Ewing sarcoma (ES) rarely derives from the sacrum or mobile spine. The discovery of primary ES with multimetastatic involvements is exceedingly less frequent in clinical practice. A 23-year-old man with initial primary sacral ES developed metastases of rib, lung, and multifocal skull after receiving surgical intervention and series of adjuvant therapies. We provide this very rare case consisting of its clinical features, imaging findings, treatments, and outcomes. Therapeutic modalities of ES are also reviewed in previous published articles. The prognosis of metastatic ES remains dismal; effective therapeutic modalities for ES require multidisciplinary collaboration, with more high-quality clinical trials to promote the optimal protocols.

Quality of life and Q-TWiST were not adversely affected in Ewing sarcoma patients treated with combined anlotinib, irinotecan, and vincristine: (Peking University People's Hospital Ewing sarcoma trial-02, PKUPH-EWS-02)

BACKGROUND

Combined treatment with anlotinib, irinotecan, as well as vincristine for advanced Ewing sarcoma (EWS) has been verified been effective in the prospective trial of Peking University People's Hospital EWS trial-02. We aimed to assess the dynamic changes in health-related quality of life (QoL) and the benefit-risk in quality-adjusted survival in current study.

METHODS

Twelve "pediatric" patients and 23 "adult" patients were enrolled. QoL was assessed with the EORTC QLQ-C30 for adults and PedsQL 3.0 Cancer Module for children and adolescents. The quality-adjusted time without symptoms of disease progression or toxicity of treatment (Q-TWiST) analysis was used to describe treatment results.

RESULTS

Progression-free survival was not accompanied by diminished QoL. Differences in scores on the QoL global health status and specific functioning before, during, and after treatment were not significantly different with time (P = .14 for adults and .91 for children). During treatment, there was a statistically insignificant trend towards improved QoL with reduced tumor burden (P = .14 for adults and .10 for children), but QoL significantly declined with progression of disease (P = .05 for adults and .04 for children). The most common adverse events were neutropenia (12.1%), leukopenia (16.6%), anemia (12.7%), and diarrhea (4.93%). Results across the trial analyses showed that the median time of Q-TWiST was 0.73 (interquartile range, 0-1.57) months, whereas the median time with toxicity before disease progression was 3.9 (interquartile range, 2.3, 6.1).

CONCLUSION

QoL exhibited a trend towards improvement in accordance with high objective response in this trial with the receipt of combination therapy of anlotinib, vinsristine, and irinotecan for advanced EWS. The toxicity profile did not translate into significantly worse overall scores during treatment.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Preliminary Study on β3-Adrenoreceptor as Predictor Marker of Relapse in Ewing Sarcoma Patients

Ewing sarcoma (EWS) is a paediatric aggressive malignant tumour of bones and soft tissues. Multidisciplinary chemotherapies, surgical resection, and radiation represent the only strategies counteracting the disease, however spreading and relapse of disease still remain a clinical issue. Circulating tumour cells (CTCs) are an important feature of EWS but the prognostic significance has not been, yet, clarified. CTCs have been found both in patients with localized disease and in those who recur or metastasize. The identification of markers that can detect recurrences and metastasis remains an important challenge for research. Unfortunately, even most of patients with localized cancer relapsed and the reason has not yet been fully understood. In this clinical study on EWS patients, we evaluated the expression of CD99 antigen and beta-3 adrenergic receptor (β3-AR) on CTCs and bioptic derived cells by flow cytometry. The preliminary data revealed a higher β3-AR expression on cells derived from metastatic or relapsed patients, suggesting a role for the β3-AR as a possible predictive maker of disease recurrence in both patients with metastatic and localized disease.

The Optimal Outcome of Suppressing Ewing Sarcoma Growth in vivo With Biocompatible Bioengineered miR-34a-5p Prodrug

Being the second most common type of primary bone malignancy in children and adolescents, Ewing Sarcoma (ES) encounters the dilemma of low survival rate with a lack of effective treatments. As an emerging approach to combat cancer, RNA therapeutics may expand the range of druggable targets. Since the genome-derived oncolytic microRNA-34a (miR-34a) is down-regulated in ES, restoration of miR-34a-5p expression or function represents a new therapeutic strategy which is, however, limited to the use of chemically-engineered miRNA mimics. Very recently we have developed a novel bioengineering technology using a stable non-coding RNA carrier (nCAR) to achieve high-yield production of biocompatible miRNA prodrugs, which is a great addition to current tools for the assessment of RNA therapeutics. Herein, for the first time, we investigated the biochemical pharmacology of bioengineered miR-34a-5p prodrug (nCAR/miR-34a-5p) in the control of ES using human ES cells and xenograft mouse models. The bioengineered nCAR/miR-34a-5p was precisely processed to mature miR-34a-5p in ES cells and subsequently suppressed cell proliferation, attributable to the enhancement of apoptosis and induction of G2 cell cycle arrest through downregulation of SIRT-1, BCL-2 and CDK6 protein levels. Furthermore, systemic administration of nCAR/miR-34a-5p dramatically suppressed the ES xenograft tumor growth in vivo while showing biocompatibility. In addition, the antitumor effect of bioengineered nCAR/miR-34a-5p was associated with a lower degree of tumoral cell proliferation and greater extent of apoptosis. These findings demonstrate the efficacy of bioengineered miR-34a-5p prodrug for the treatment of ES and support the development of miRNA therapeutics using biocompatible bioengineered miRNA prodrugs.

Precision medicine in Ewing sarcoma: a translational point of view

Ewing sarcoma is a rare tumor that arises in bones of children and teenagers but, in 15% of the patients it is presented as a primary soft tissue tumor. Balanced reciprocal chimeric translocation t(11;22)(q24;q12), which encodes an oncogenic protein fusion (EWSR1/FLI1), is the most generalized and characteristic molecular event. Using conventional treatments, (chemotherapy, surgery and radiotherapy) long-term overall survival rate is 30% for patients with disseminated disease and 65-75% for patients with localized tumors. Urgent new effective drug development is a challenge. This review summarizes the preclinical and clinical investigational knowledge about prognostic and targetable biomarkers in Ewing sarcoma, finally suggesting a workflow for precision medicine committees.

Ewing's sarcoma with distant metastasis: A brief note on management and emerging therapies

Ewing’s sarcoma is an aggressive fatal malignancy of bones and soft-tissue. It predominantly affects the young population, with a worldwide incidence of three cases per million. The pelvis, extremities, and ribs are the most common sites. We present a case of massive Ewing’s sarcoma of the right femur with metastasis to bones and lungs. The patient was treated with chemotherapy. However, he succumbed to his illness before completion of therapy. In conclusion, Ewing’s sarcoma with distant metastasis is a high risk case with poor prognosis. Integrating novel molecular targets with conventional chemotherapeutic agents holds a promise for high-risk Ewing’s sarcoma patients.

The efficacy and safety of apatinib in Ewing's sarcoma: a retrospective analysis in one institution

BACKGROUND

Ewing's sarcoma (ES) is a highly aggressive and metastatic neoplasm occurring mainly in children and young adults. The standard treatment of localized ES requires a combination of surgery, chemotherapy, and radiotherapy. Although the 5-year survival rate for local ES has improved, the survival rate and prognosis are still very poor for metastatic or recurrent ES patients. The aim of this study was to investigate the efficacy and safety of apatinib, a specific vascular endothelial growth factor receptor 2 inhibitor, in ES patients.

METHODS

This retrospective analysis involved eleven patients with ES not amenable to curative treatment. All patients suffered poor responses to two cycles of chemotherapy (vincristine, doxorubicin, and cyclophosphamide). Apatinib 500 mg (or 250 mg) was given daily. Tumor responses were assessed according to the Response Evaluation Criteria in Solid Tumors 1.1. Survival analysis was performed by the Kaplan-Meier test. The safety profile was also recorded.

RESULTS

The mean age of the patients was 18 (range, 10-31) years. The 12-month overall survival and progression-free survival rates were 90% and 72%, respectively. Four patients achieved partial response, and four patients achieved stable disease, with objective response rate of 40%. The median follow-up in our study was 16 months (range, 3-26 months). The most common adverse events included hand-foot skin reaction (n=5; 45%), oral ulcers (n=4; 36%), and gastrointestinal discomfort (n=4; 36%).

CONCLUSION

Apatinib may provide as second- or first-line treatment options for ES patients, particularly in chemoresistant cases. Further studies with more cases and longer follow-up will be necessary to determine the clinical efficacy and safety of apatinib in ES patients.

Clinical implications of six inflammatory biomarkers as prognostic indicators in Ewing sarcoma

Cancer-related systemic inflammation responses have been correlated with cancer development and progression. The prognostic significance of several inflammatory indicators, including neutrophil–lymphocyte ratio (NLR), platelet–lymphocyte ratio (PLR), Glasgow Prognostic Score (GPS), C-reactive protein to albumin ratio (CRP/Alb ratio), lymphocyte–monocyte ratio (LMR), and neutrophil–platelet score (NPS), were found to be correlated with prognosis in several cancers. However, the prognostic role of these inflammatory biomarkers in Ewing sarcoma has not been evaluated. This study enrolled 122 Ewing patients. Receiver operating characteristic (ROC) analysis was generated to determine optimal cutoff values; areas under the curves (AUCs) were assessed to show the discriminatory ability of the biomarkers; Kaplan–Meier analysis was conducted to plot the survival curves; and Cox multivariate survival analysis was performed to identify independent prognostic factors. The optimal cutoff values of CRP/Alb ratio, NLR, PLR, and LMR were 0.225, 2.38, 131, and 4.41, respectively. CRP/Alb ratio had a significantly larger AUC than NLR, PLR, LMR, and NPS. Higher levels of CRP/Alb ratio (hazard ratio [HR] 2.41, P=0.005), GPS (HR 2.27, P=0.006), NLR (HR 2.07, P=0.013), and PLR (HR 1.85, P=0.032) were significantly correlated with poor prognosis. As the biomarkers had internal correlations, only the CRP/Alb ratio was involved in the multivariate Cox analysis and remained an independent prognostic indicator. The study demonstrated that CRP/Alb ratio, GPS, and NLR were effective prognostic indicators for patients with Ewing sarcoma, and the CRP/Alb ratio was the most robust prognostic indicator with a discriminatory ability superior to that of the other indicators; however, PLR, LMR, and NPS may not be suitable as prognostic indicators in Ewing sarcoma.

Matrix Screen Identifies Synergistic Combination of PARP Inhibitors and Nicotinamide Phosphoribosyltransferase (NAMPT) Inhibitors in Ewing Sarcoma

Purpose: Although many cancers are showing remarkable responses to targeted therapies, pediatric sarcomas, including Ewing sarcoma, remain recalcitrant. To broaden the therapeutic landscape, we explored the in vitro response of Ewing sarcoma cell lines against a large collection of investigational and approved drugs to identify candidate combinations.Experimental Design: Drugs displaying activity as single agents were evaluated in combinatorial (matrix) format to identify highly active, synergistic drug combinations, and combinations were subsequently validated in multiple cell lines using various agents from each class. Comprehensive metabolomic and proteomic profiling was performed to better understand the mechanism underlying the synergy. Xenograft experiments were performed to determine efficacy and in vivo mechanism.Results: Several promising candidates emerged, including the combination of small-molecule PARP and nicotinamide phosphoribosyltransferase (NAMPT) inhibitors, a rational combination as NAMPTis block the rate-limiting enzyme in the production of nicotinamide adenine dinucleotide (NAD⁺), a necessary substrate of PARP. Mechanistic drivers of the synergistic cell killing phenotype of these combined drugs included depletion of NMN and NAD⁺, diminished PAR activity, increased DNA damage, and apoptosis. Combination PARPis and NAMPTis in vivo resulted in tumor regression, delayed disease progression, and increased survival.Conclusions: These studies highlight the potential of these drugs as a possible therapeutic option in treating patients with Ewing sarcoma. Clin Cancer Res; 23(23); 7301-11. ©2017 AACR.

Metabolic modulation of Ewing sarcoma cells inhibits tumor growth and stem cell properties

Ewing sarcoma (EWS) is a highly aggressive and metabolically active malignant tumor. Metabolic activity can broadly be characterized by features of glycolytic activity and oxidative phosphorylation. We have further characterized metabolic features of EWS cells to identify potential therapeutic targets. EWS cells had significantly more glycolytic activity compared to their non-malignant counterparts. Thus, metabolic inhibitors of glycolysis such as 2-deoxy-D-glucose (2DG) and of the mitochondrial respiratory pathway, such as metformin, were evaluated as potential therapeutic agents against a panel of EWS cell lines in vitro. Results indicate that 2DG alone or in combination with metformin was effective at inducing cell death in EWS cell lines. The predominant mechanism of cell death appears to be through stimulating apoptosis leading into necrosis with concomitant activation of AMPK-α. Furthermore, we demonstrate that the use of metabolic modulators can target putative EWS stem cells, both in vitro and in vivo, and potentially overcome chemotherapeutic resistance in EWS. Based on these data, clinical strategies using drugs targeting tumor cell metabolism present a viable therapeutic modality against EWS.

Shikonin promotes adriamycin‑induced apoptosis by upregulating caspase‑3 and caspase‑8 in osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor. Cancer cells employ a host of mechanisms to develop resistance to adriamycin (ADM) or other chemotherapeutic drugs. Shikonin (SK), an active constituent extracted from a Chinese medicinal herb, has been shown to cooperate with ADM in the treatment of osteosarcoma and certain other types of cancer by contributing to the response rate of chemotherapy and the side effects. The aim of the present study was to investigate the role and underlying mechanism of SK in chemotherapy for osteosarcoma. In the present study, a CCK-8 assay was performed to assess cell survival rate in vitro. Western blot analysis was performed to determine the expression levels of B-cell lymphoma 2-associated X protein (Bax), caspase-3, caspase-8, and poly (ADP-ribose) polymerase (PARP). Flow cytometry was used to analyze cell cycle and cell death. The survival rate of cells decreased significantly in a dose- and time-dependent manner when treated with a combination of SK and ADM. Western blot analysis revealed increased expression levels of Bax, caspase-3, caspase-8 and PARP in U2OS and MG63 cells 48 h following treatment with SK and ADM. Flow cytometric analysis showed that the combined treatment of SK and ADM significantly induced apoptosis in the osteosarcoma cells. Taken together SK cooperated with ADM to promote apoptosis, possibly by inducing caspase-3- and caspase-8-dependent apoptosis. SK may be a potential enhancer in the treatment of drug-resistant primary osteosarcoma.

EWSR1 rearrangement is a frequent event in papillary thyroid carcinoma and in carcinoma of the thyroid with Ewing family tumor elements (CEFTE)

Carcinomas of the thyroid with Ewing family tumor element (CEFTEs) are small-cell thyroid tumors with epithelial differentiation that disclose p63 expression and EWSR1-FLI1 rearrangement, carry a favorable prognosis and may co-exist with papillary thyroid carcinoma (PTC) foci. Two histogenetic hypotheses have been advanced regarding the origin of CEFTEs: arising in PTCs or in solid cell nests (SCN). A total of 3 CEFTEs, 54 PTCs, and 10 SCNs were reviewed, and fluorescence in situ hybridization (FISH) technique was performed in all cases to search for the presence of EWSR1 rearrangements. The three CEFTEs disclosed the EWSR1-FLI1 rearrangement both in the small cell and in the PTC component. Out of the 54 PTC cases, 28 (51.9%) were positive, 20 (37.0%) were negative, and 6 (11.1%) were inconclusive for EWSR1 rearrangement; in two of the positive PTC cases, the EWSR1-FLI1 rearrangement was detected. Classic PTC disclosed more often the EWSR1 rearrangement than other PTC variants (p = 0.031). PTCs with EWSR1 rearrangement disclosed a lower percentage of nuclei with EWSR1 polysomy than those without EWSR1 rearrangement (p = 0.001). Out of the 10 SCNs, 7 (70.0%) were negative and 3 (30.0%) were inconclusive for the EWSR1 rearrangement. Monosomic nuclei were more frequent (mean of 44.3%) in SCNs than in PTCs (p < 0.001). The presence of the EWSR1-FLI1 rearrangement in PTC component of all studied CEFTEs and the existence of the EWSR1 rearrangement in some PTCs favor the origin of CEFTE from PTC. The high frequency of EWSR1 rearrangements in PTC may represent a new diagnostic marker of these tumors.

Combinatorial Drug Screening Identifies Ewing Sarcoma-specific Sensitivities

Improvements in survival for Ewing sarcoma pediatric and adolescent patients have been modest over the past 20 years. Combinations of anticancer agents endure as an option to overcome resistance to single treatments caused by compensatory pathways. Moreover, combinations are thought to lessen any associated adverse side effects through reduced dosing, which is particularly important in childhood tumors. Using a parallel phenotypic combinatorial screening approach of cells derived from three pediatric tumor types, we identified Ewing sarcoma-specific interactions of a diverse set of targeted agents including approved drugs. We were able to retrieve highly synergistic drug combinations specific for Ewing sarcoma and identified signaling processes important for Ewing sarcoma cell proliferation determined by EWS-FLI1 We generated a molecular target profile of PKC412, a multikinase inhibitor with strong synergistic propensity in Ewing sarcoma, revealing its targets in critical Ewing sarcoma signaling routes. Using a multilevel experimental approach including quantitative phosphoproteomics, we analyzed the molecular rationale behind the disease-specific synergistic effect of simultaneous application of PKC412 and IGF1R inhibitors. The mechanism of the drug synergy between these inhibitors is different from the sum of the mechanisms of the single agents. The combination effectively inhibited pathway crosstalk and averted feedback loop repression, in EWS-FLI1-dependent manner. Mol Cancer Ther; 16(1); 88-101. ©2016 AACR.

Clinical Decision Making: Integrating Advances in the Molecular Understanding of Spine Tumors

STUDY DESIGN

Literature review.

OBJECTIVE

To describe advancements in molecular techniques, biomarkers, technology, and targeted therapeutics and the potential these modalities hold to predict treatment paradigms, clinical outcomes, and/or survival in patients diagnosed with primary spinal column tumors.

SUMMARY OF BACKGROUND DATA

Advances in molecular technologies and techniques have influenced the prevention, diagnosis, and overall management of patients diagnosed with cancer. Assessment of genomic, proteomic alterations, epigenetic, and posttranslational modifications as well as developments in diagnostic modalities and targeted therapeutics, although the best studied in nonspinal metastatic disease, have led to increased understanding of spine oncology that is expected to improve patient outcomes. In this manuscript, the technological advancements that are expected to change the landscape of spinal oncology are discussed with a focus on how these technologies will aid in clinical decision-making for patients diagnosed with primary spinal tumors.

METHODS

A review of the literature was performed focusing on studies that integrated next-generation sequencing, circulating tumor cells/circulating tumor DNA, advances in imaging modalities and/or radiotherapy in the diagnosis and treatment of cancer.

RESULTS

We discuss genetic and epigenetic drivers, aberrations in receptor tyrosine kinase signaling, and emerging therapeutic strategies that include receptor tyrosine kinase inhibitors, immunotherapy strategies, and vaccine-based cancer prevention strategies.

CONCLUSION

The wide range of approaches currently in use and the emerging technologies yet to be fully realized will allow for better development of rationale therapeutics to improve patient outcomes.

LEVEL OF EVIDENCE

N/A.

Arsenic trioxide potentiates the effectiveness of etoposide in Ewing sarcomas

Ewing sarcomas (ES) are rare mesenchymal tumours, most commonly diagnosed in children and adolescents. Arsenic trioxide (ATO) has been shown to efficiently and selectively target leukaemic blasts as well as solid tumour cells. Since multidrug resistance often occurs in recurrent and metastatic ES, we tested potential additive effects of ATO in combination with the cytostatic drugs etoposide and doxorubicin. The Ewing sarcoma cell lines A673, RD-ES and SK-N-MC as well as mesenchymal stem cells (MSC) for control were treated with ATO, etoposide and doxorubicin in single and combined application. Viability and proliferation (MTS assay, colony formation, 3D spheroid culture) as well as cell death induction (western blot analysis, flow cytometry) were analysed. In the MTS viability assays ATO treatment significantly reduced the metabolic activity of all three ES cell lines (A673, RD-ES and SK-N-MC) examined. Moreover, all ES cell lines were sensitive to etoposide, whereas MSC remained unaffected by the drug concentrations used. With the exception of ATO in RD-ES cells, all drugs induced apoptosis in the ES cell lines, indicated by caspase-3 and PARP cleavage. Combination of the agents potentiated the reduction of viability as well as the inhibitory effect on clonal growth. In addition, cell death induction was obviously enhanced in RD-ES and SK-N-MC cells by a combination of ATO and etoposide compared to single application. Summarised, the combination of low dose, physiologically easily tolerable ATO with commonly used etoposide and doxorubicin concentrations efficiently and selectively suppressed viability and colony formation in ES cell lines, whereas a combination of ATO and etoposide was favourable for cell death induction. In addition to an increase of the effectiveness of the cytostatic drugs and prevention of potential drug resistance, this approach may also reduce toxicity effects, since the individual doses can be reduced.

PRAS40 deregulates apoptosis in Ewing sarcoma family tumors by enhancing the insulin receptor/Akt and mTOR signaling pathways

EWS expression in Ewing sarcoma family tumors (ESFTs) is decreased due to the haploinsufficiency elicited by chromosomal translocation. The abnormal expression levels of EWS and its downstream factors contribute to the manifestation of ESFTs. Previously, we reported that increased Proline-rich Akt substrate of 40 kDa (PRAS40), which is encoded by an EWS mRNA target, promotes the development of ESFTs. However, the mechanism remains elusive. To clarify the role of PRAS40 in ESFTs, we silenced PRAS40 expression in ESFT cells using siRNAs and found increased levels of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells. Cleaved caspase 3 levels and cytochrome C release were increased simultaneously. Furthermore, with PRAS40 knockdown, the phosphorylation of Akt and mTOR downstream factors, i.e., S6K and S6, was attenuated notably. Ectopic expression of PRAS40 increased Akt and S6 phosphorylation. Activation of Akt only partially reversed the apoptosis induced by PRAS40 knockdown, and downregulation of S6 phosphorylation by PRAS40 silencing could not be sufficiently restored via Akt activation. Searching the upstream factors in this pathway, the autophosphorylation of insulin receptor (IR) was found to be inhibited significantly by PRAS40 silencing but increased by PRAS40 overexpression. Therefore, PRAS40 may enhance IR phosphorylation to facilitate Akt and mTOR signaling leading to the apoptosis deregulation in ESFTs. Moreover, in vivo results confirmed that PRAS40 deletion suppressed the growth of ESFT xenografts and downregulated IR and S6 phosphorylation. Our findings suggest a novel functioning model for PRAS40, which represents a novel therapeutic target for ESFTs.

A Review: Molecular Aberrations within Hippo Signaling in Bone and Soft-Tissue Sarcomas

The Hippo signaling pathway is an evolutionarily conserved developmental network vital for the regulation of organ size, tissue homeostasis, repair and regeneration, and cell fate. The Hippo pathway has also been shown to have tumor suppressor properties. Hippo transduction involves a series of kinases and scaffolding proteins that are intricately connected to proteins in developmental cascades and in the tissue microenvironment. This network governs the downstream Hippo transcriptional co-activators, YAP and TAZ, which bind to and activate the output of TEADs, as well as other transcription factors responsible for cellular proliferation, self-renewal, differentiation, and survival. Surprisingly, there are few oncogenic mutations within the core components of the Hippo pathway. Instead, dysregulated Hippo signaling is a versatile accomplice to commonly mutated cancer pathways. For example, YAP and TAZ can be activated by oncogenic signaling from other pathways, or serve as co-activators for classical oncogenes. Emerging evidence suggests that Hippo signaling couples cell density and cytoskeletal structural changes to morphogenic signals and conveys a mesenchymal phenotype. While much of Hippo biology has been described in epithelial cell systems, it is clear that dysregulated Hippo signaling also contributes to malignancies of mesenchymal origin. This review will summarize the known molecular alterations within the Hippo pathway in sarcomas and highlight how several pharmacologic compounds have shown activity in modulating Hippo components, providing proof-of-principle that Hippo signaling may be harnessed for therapeutic application in sarcomas.