Vascular endothelial growth factor: a therapeutic target for tumors of the Ewing's sarcoma family

Tyrosine kinase inhibitors in Ewing's sarcoma: a systematic review

Ewing's sarcoma (ES) is a highly aggressive primary bone malignancy that primarily affects children and adolescents. Several tyrosine kinase receptors (RTKs) have been found to be overexpressed in ES samples, and it was demonstrated that some play significant roles in driving the malignant phenotype of ES. Specifically, ES with insulin-like growth factor 1 (IGF1R) or vascular endothelial growth factor (VEGFR) overexpression were correlated with more aggressive ES and worse outcomes. Other RTKs that were determined to be overexpressed in ES include platelet-derived growth factor receptor, stem cell factor receptor, and hepatocyte growth factor. Overexpression of these molecules suggests their possible tumor-driving role, making them potential targets for intervention. Various tyrosine kinase inhibitors (TKIs), including apatinib, anlotinib, and cabozantinib have shown clinical promise in patients with recurrent ES who have progressed on previous lines of therapy. The findings reported in this review emphasize the importance of assessing IGF1R-focused inhibitors and combinational therapeutic regimens in future research. Furthermore, biomarkers predictive of response are necessary to improve patient outcomes. In order to optimize ES care, considerations for patient eligibility on the basis of positivity for biomarkers predictive of response, and the inclusion of quality-of-life evaluations in studies must be addressed.

Druggable upregulated proteins in EWS-FLI-driven Ewing sarcoma as emerging new therapeutic targets

Ewing sarcoma (ES) is a highly aggressive soft tissue tumor that primarily affects the long bones of children and young adults. It is distinguished by a characteristic chromosomal translocation between the Ewing sarcoma breakpoint region 1 (EWS) gene and the erythroblast transformation-specific (ETS) family of genes, most commonly resulting in the EWS-friend leukemia integration 1 (EWS-FLI1) fusion gene. This translocation is observed in approximately 80%-85% of ES cases. This fusion gene encodes a non-physiological chimeric fusion protein that plays a central role in tumorigenesis by interacting with numerous partner proteins. Several studies have demonstrated the tumorigenic potential of the EWS-FLI1 protein when transfected into non-cancer cell lines. However, targeting EWS-FLI1 directly remains a significant challenge, as no drug to date has been reported to bind to and inhibit its activity effectively. An alternative therapeutic strategy involves targeting key overexpressed protein complexes implicated in ES tumorigenesis, many of which may be downstream interacting partners of EWS-FLI1. This review explores emerging protein targets as potential therapeutic avenues in ES treatment.

A Novel Treatment for Ewing's Sarcoma: Chimeric Antigen Receptor-T Cell Therapy

Ewing's sarcoma (EWS) is a malignant and aggressive tumor type that predominantly occurs in children and adolescents. Traditional treatments such as surgery, radiotherapy and chemotherapy, while successful in the early disease stages, are ineffective in patients with metastases and relapses who often have poor prognosis. Therefore, new treatments for EWS are needed to improve patient's outcomes. Chimeric antigen receptor (CAR)-T cells therapy, a novel adoptive immunotherapy, has been developing over the past few decades, and is increasingly popular in researches and treatments of various cancers. CAR-T cell therapy has been approved by the Food and Drug Administration (FDA) for the treatment of leukemia and lymphoma. Recently, this therapeutic approach has been employed for solid tumors including EWS. In this review, we summarize the safety, specificity and clinical transformation of the treatment targets of EWS, and point out the directions for further research.

An overview of current results with the vincristine-irinotecan-temozolomide combination with or without bevacizumab in pediatric, adolescence and adult solid tumors

Malignant tumors in young patients present a significant therapeutic challenge for physicians, partially due to their rarity and a relative lack of data, at least compared to adult tumors. As a result, there is an urgent need to explore new possible therapeutic regimens, either by introducing novel agents or by exploring combinations of existing agents. Vincristine, Temozolomide and Irinotecan are chemotherapeutic drugs which have emerged over the last six decades as monotherapy or as part of therapeutic regimens in various solid tumors. Combining these agents can yield strong synergistic effects, as suggested by preclinical data and results from clinical trials. Furthermore, adding novel molecules, such as anti-VEGF factor Bevacizumab to the aforementioned regimens, has shown efficacy in a limited number of trials, which are thoroughly analyzed throughout this review. Data presented throughout this paper suggest that VIT(b) regimen should be further explored in solid tumors in pediatric and adolescent patients.

Targeting EYA3 in Ewing Sarcoma Retards Tumor Growth and Angiogenesis

EWSR1/FLI1, the most common fusion gene in Ewing sarcoma, upregulates expression of the Eyes Absent 3 (EYA3) transactivator-phosphatase protein. The purpose of this study was to investigate molecular and cellular mechanisms through which EYA3 might promote Ewing sarcoma tumor growth and to determine whether the EYA3 tyrosine phosphatase activity represents a viable therapeutic target. We used genetic and pharmacologic modulation of EYA3 in cell line-based xenografts to examine how loss of EYA3 tyrosine phosphatase activity affects tumor growth and angiogenesis. Molecular mechanisms were evaluated in vivo and in vitro through analyses of tumor tissue and multicellular tumor spheroids. Our results show that both loss of EYA3 in Ewing sarcoma cells and pharmacologic inhibition of the EYA3 tyrosine phosphatase activity inhibit tumor growth and tumor angiogenesis. EYA3 regulates levels of VEGFA in Ewing tumors, as well as promoting DNA damage repair and survival of Ewing sarcoma tumor cells. Target engagement is demonstrated in tumor tissue through elevated levels of the EYA3 substrate H2AX-pY142 upon loss of EYA3 or with Benzarone treatment. The efficacy of EYA3 tyrosine phosphatase inhibition in attenuating tumor growth and angiogenesis is corroborated in an Ewing sarcoma patient-derived tumor xenograft. Together, the results presented here validate EYA3 as a target for the development of novel Ewing sarcoma therapeutic strategies, and set the stage for evaluating the efficacy of combining the antiangiogenic and anti-cell survival effects of EYA3 inhibition with cytotoxic chemotherapy.

Targeting Tumor-Associated Macrophages in the Pediatric Sarcoma Tumor Microenvironment

For many pediatric sarcoma patients, multi-modal therapy including chemotherapy, radiation, and surgery is sufficient to cure their disease. However, event-free and overall survival rates for patients with more advanced disease are grim, necessitating the development of novel therapeutic approaches. Within many pediatric sarcomas, the normal immune response, including recognition and destruction of cancer cells, is lost due to the highly immune suppressive tumor microenvironment (TME). In this setting, tumor cells evade immune detection and capitalize on the immune suppressed microenvironment, leading to unchecked proliferation and metastasis. Recent preclinical and clinical approaches are aimed at understanding this immune suppressive microenvironment and employing cancer immunotherapy in an attempt to overcome this, by renewing the ability of the immune system to recognize and destroy cancer cells. While there are several factors that drive the attenuation of immune responses in the sarcoma TME, one of the most remarkable are tumor associated macrophage (TAMs). TAMs suppress immune cytolytic function, promote tumor growth and metastases, and are generally associated with a poor prognosis in most pediatric sarcoma subtypes. In this review, we summarize the mechanisms underlying TAM-facilitated immune evasion and tumorigenesis and discuss the potential therapeutic application of TAM-focused drugs in the treatment of pediatric sarcomas.

VEGFR2 as a target for CAR T cell therapy of Ewing sarcoma

BACKGROUND

T cells engineered to express chimeric antigen receptors (CARs) are a novel modality to treat refractory cancers. The development of CAR T cells against Ewing sarcoma (EwS) is limited by a lack of targetable surface antigens. We investigated vascular endothelial growth factor receptor 2 (VEGFR2) expressed on tumor-associated blood vessels as potential CAR target in this cancer.

METHODS

Expression of VEGFR2 was studied by immunohistochemistry in human EwS biopsies and in murine xenografts and by flow cytometry in EwS cell lines. CARs with short, medium, and long hinge domains against either human or murine VEGFR2 were generated and expressed in human T cells by retroviral gene transfer. The capacity of the individual CARs to activate T cells in response to VEGFR2-expressing cells was compared in vitro.

RESULTS

Tumor-associated endothelial cells in human EwS biopsies and in xenografts expressed VEGFR2. Tumor cells in the majority of EwS biopsies were also VEGFR2-positive. Following modification with anti-mouse or anti-human VEGFR2-specific CAR genes, T cells specifically lysed VEGFR2-expressing target cells of the respective species. CAR T cells with short-length or medium-length hinge domains were functionally superior over those with the long hinge region by in vitro parameters, including antigen-specific degranulation responses, lysis of tumor spheroids, tumor necrosis factor α secretion, sequential killing, and proliferation.

CONCLUSIONS

VEGFR2 is consistently expressed on endothelial cells of the tumor stroma in EwS and thus is a candidate target for CAR T cells in this cancer. Among various VEGFR2-specific CARs, a construct with a short hinge domain was chosen to be further developed toward clinical translation.

Hepatocellular carcinoma-derived exosomes in organotropic metastasis, recurrence and early diagnosis application

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, despite improvements in the clinical trial and diagnosis, HCC still remains high mortality due to the 70% recurrence and lung metastasis after surgical resection. Exosomes are small membrane vesicles, which are shuttled from donor cells to recipient cells, contributing to the recruitment and reprogramming of constituents via an autocrine or paracrine fashion. HCC derived exosomes could redirect metastasis of tumor cells which lack the capacity to metastasize to a specific organ via generating pre-metastatic niche. These findings emphasize a practical and potentially feasible role of exosomes in the treatment of patients with HCC, both as a target and a vehicle for drug design. We herein summarize recent findings that implicate oncogenes and non-canonical signaling of HCC exosomes, as well as the impact of exosomal bioactive molecules in high recurrence induced by organ-specific metastasis. The aim of review is to illustrate the underlying mechanism of exosomes in tumor metastasis, immune evasion, and the potential application of prognostic biomarker in HCC process.

Integrative Clustering Reveals a Novel Subtype of Soft Tissue Sarcoma With Poor Prognosis

Background

Soft tissue sarcomas (STSs) are heterogeneous at the clinical and molecular level and need to be further sub-clustered for treatment and prognosis.

Materials And Methods

STSs were sub-clustered based on RNAseq and miRNAseq data extracted from The Cancer Genome Atlas (TCGA) through the combined process of similarity network fusion (SNF) and consensus clustering (CC). The expression and clinical characteristics of each sub-cluster were analyzed. The genes differentially expressed (lncRNAs, miRNAs, and mRNAs) between the poor prognosis and good prognosis clusters were used to construct a competing endogenous RNA (ceRNA) network. Functional enrichment analysis was conducted and a hub network was extracted from the constructed ceRNA network.

Results

A total of 247 STSs were classified into three optimal sub-clusters, and patients in cluster 2 (C2) had a significantly lower rate of survival. A ceRNA network with 91 nodes and 167 edges was constructed according to the hypothesis of ceRNA. Functional enrichment analysis revealed that the network was mainly associated with organism development functions. Moreover, LncRNA (KCNQ1OT1)-miRNA (has-miR-29c-3p)-mRNA (JARID2, CDK8, DNMT3A, TET1)-competing endogenous gene pairs were identified as hub networks of the ceRNA network, in which each component showed survival significance.

Conclusion

Integrative clustering analysis revealed that the STSs could be clustered into three sub-clusters. The ceRNA network, especially the subnetwork LncRNA (KCNQ1OT1)-miRNA (has-miR-29c-3p)-mRNA (JARID2, CDK8, DNMT3A, TET1) was a promising therapeutic target for the STS sub-cluster associated with a poor prognosis.

Tissue engineered models of healthy and malignant human bone marrow

Tissue engineering is becoming increasingly successful in providing in vitro models of human tissues that can be used for ex vivo recapitulation of functional tissues as well as predictive testing of drug efficacy and safety. From simple tissue models to microphysiological platforms comprising multiple tissue types connected by vascular perfusion, these "tissues on a chip" are emerging as a fast track application for tissue engineering, with great potential for modeling diseases and supporting the development of new drugs and therapeutic targets. We focus here on tissue engineering of the hematopoietic stem and progenitor cell compartment and the malignancies that can develop in the human bone marrow. Our overall goal is to demonstrate the utility and interconnectedness of improvements in bioengineering methods developed in one area of bone marrow studies for the remaining, seemingly disparate, bone marrow fields.

Use of bevacizumab as a single agent or in adjunct with traditional chemotherapy regimens in children with unresectable or progressive low-grade glioma

In pediatric low‐grade gliomas not amenable to complete resection, various chemotherapy regimens are the mainstream of treatment. An excellent overall survival of these patients makes justification of the intensification of chemotherapy difficult and calls for the development of new strategies. Bevacizumab, a humanized monoclonal antibody directed against Vascular endothelial growth factor (VEGF), has been successfully used in combination with irinotecan in a number of adult and pediatric studies and reports. Fifteen patients at median age of 7 years old (range 3 months to 15 years) were treated with bevacizumab in combination with conventional low‐toxicity chemotherapy. The majority had chiasmatic/hypothalamic and midline tumors, seven had confirmed BRAF pathway alterations including neurofibromatosis type 1 (2). Fourteen patients had more than one progression and three had radiotherapy. No deaths were documented, PFS at 11 and 15 months was 71.5% ± 13.9% and 44.7% ± 17.6% respectively. At the end of follow‐up 40% of patients has radiologically stable disease, three patients progressed shortly after completion of bevacizumab and two showed mixed response with progression of cystic component. Rapid visual improvement was seen in 6/8 patients, resolution of endocrine symptoms in 2/4 and motor function improvement in 4/6. No relation between histology or BRAF status and treatment response was observed. Treatment‐limiting toxicities included grade 4 proteinuria (2) and hypertension (2) managed with cessation (1) and pausing of therapy plus antihypertensives (1). In conclusion, bevacizumab is well tolerated and appears most effective for rapid tumor control to preserve vision and improve morbidity.

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.

Evaluation of Detection Methods and Values of Circulating Vascular Endothelial Growth Factor in Lung Cancer

Lung cancer is the deadliest cancer in the world. Angiogenesis plays a crucial role of the incidence, progression, and metastasis in lung cancer. Angiogenesis inhibitors are used to treat non-small cell lung cancer (NSCLC) patients, and the molecular biomarkers are also being assessed to predict treatment response/therapeutic response and patients' prognosis. Vascular endothelial growth factor (VEGF) is a signal protein produced by cells that stimulates angiogenesis. Due to its predictive values of prognosis on NSCLC, a large number of methods have been developed and evaluated to detect VEGF levels in a variety of studies. In this article, we review the detection methods designed to measure the VEGF levels in different body fluids and prognosticate the value of VEGF in treatment, diagnosis and survival in lung cancer.

Pediatric Orbital Primitive Neuroectodermal Tumors

PURPOSE

To present the clinical, radiological, histopathological, immunohistochemical features and the follow-up of orbital primitive neuroectodermal tumors (PNETs) in pediatric patients along with a review of the literature.

METHODS

A retrospective analysis of all diagnosed cases of orbital PNET was done. Patients' ophthalmic findings, imaging, immunohistochemistry, metastatic work-up, treatment, globe salvation, and survival were documented and a mini literature review of orbital PNET was performed.

RESULTS

Four diagnosed cases of orbital PNET presented with proptosis and visual impairment were treated during the study period. The radiological imaging showed primary orbital involvement. There were three males and one female with a mean age of 63.75 months (range: 3 to 244 months). Histopathology of all studied patients showed round malignant cells with hyperchromatic nuclei, increased nuclear cytoplasmic ratio, and positive test results for CD99 and FLI-1. The studied patients underwent orbital surgery for excision of tumors followed by chemotherapy. One of the patients also had external radiation in addition to chemotherapy after a second recurrence. The follow-up period of these patients varied from 1 to 5 years. Only one child who had recurrence twice was followed up to 5 years, but was lost to follow-up after that.

CONCLUSIONS

The authors believe that most orbital peripheral PNET tumors present as well-defined masses on both imaging and perioperatively and are easily removed surgically. The apparently disguised "benign profile" of orbital PNET may prove deceptive and the shorter duration of symptoms remains a strong reminder of the malignant nature of the lesion. [J Pediatr Ophthalmol Strabismus. 2018;55(2):93-99.].

Receptor tyrosine kinase gene expression profiles of Ewing sarcomas reveal ROR1 as a potential therapeutic target in metastatic disease

Receptor tyrosine kinases (RTKs) have provided molecular targets for the development of novel, prognosis-improving agents in many cancers; however, resistances to these therapies occur. On the cellular level, one resistance mechanism is attributed to functional RTK redundancies and compensatory cross-signaling, leading to perception of RTKs as signaling and target networks. To provide a basis for better exploitation of this network in Ewing sarcoma, we generated comprehensive qPCR gene expression profiles of RTKs in Ewing sarcoma cell lines and 21 untreated primary tumors. Key findings confirm broad-spectrum RTK expressions with potential for signaling redundancy. Profile analyses with regard to patient risk-group further revealed several individual RTKs of interest. Among them, VEGFR3 and TIE1 showed high-level expressions and also were suggestive of poor prognosis in localized tumors; underscoring the relevance of angiogenic signaling pathways and tumor-stroma interactions in Ewing sarcoma. Of note, compared to localized disease, tumors derived from metastatic disease were marked by global high-level RTK expressions. Nine individual RTKs were significantly over-expressed, suggesting contributions to molecular mechanisms of metastasis. Of these, ROR1 is being pursued as therapeutic target in leukemias and carcinomas, but un-characterized in sarcomas. We demonstrate expression of ROR1 and its putative ligand Wnt5a in Ewing sarcomas, and of an active ROR1 protein variant in cell lines. ROR1 silencing impaired cell migration in vitro. Therefore, ROR1 calls for further evaluation as a therapeutic target in metastatic Ewing sarcoma; and described as a pseudo-kinase with several isoforms, underlines these additional complexities arising in our understanding of RTK signaling networks.

Central-type primitive neuroectodermal tumor of the uterus: Case report of remission of stage IV disease using adjuvant cisplatin/etoposide/bevacizumab chemotherapy and review of the literature

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Bevacizumab was an effective agent in one case of advanced uterine PNET.

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VEGF was expressed by the tumor, supporting a mechanism for effectiveness.

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Cisplatin/etoposide/bevacizumab should be further studied in clinical trials.

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Patient remains disease-free forty-eight months following intervention.

Immunotherapy of Childhood Sarcomas

Pediatric sarcomas are a heterogeneous group of malignant tumors of bone and soft tissue origin. Although more than 100 different histologic subtypes have been described, the majority of pediatric cases belong to the Ewing’s family of tumors, rhabdomyosarcoma and osteosarcoma. Most patients that present with localized stage are curable with surgery and/or chemotherapy; however, those with metastatic disease at diagnosis or those who experience a relapse continue to have a very poor prognosis. New therapies for these patients are urgently needed. Immunotherapy is an established treatment modality for both liquid and solid tumors, and in pediatrics, most notably for neuroblastoma and osteosarcoma. In the past, immunomodulatory agents such as interferon, interleukin-2, and liposomal-muramyl tripeptide phosphatidyl-ethanolamine have been tried, with some activity seen in subsets of patients; additionally, various cancer vaccines have been studied with possible benefit. Monoclonal antibody therapies against tumor antigens such as disialoganglioside GD2 or immune checkpoint targets such as CTLA-4 and PD-1 are being actively explored in pediatric sarcomas. Building on the success of adoptive T cell therapy for EBV-related lymphoma, strategies to redirect T cells using chimeric antigen receptors and bispecific antibodies are rapidly evolving with potential for the treatment of sarcomas. This review will focus on recent preclinical and clinical developments in targeted agents for pediatric sarcomas with emphasis on the immunobiology of immune checkpoints, immunoediting, tumor microenvironment, antibody engineering, cell engineering, and tumor vaccines. The future integration of antibody-based and cell-based therapies into an overall treatment strategy of sarcoma will be discussed.

Bone Sarcomas in Pediatrics: Progress in Our Understanding of Tumor Biology and Implications for Therapy

The pediatric bone sarcomas osteosarcoma and Ewing sarcoma represent a tremendous challenge for the clinician. Though less common than acute lymphoblastic leukemia or brain tumors, these aggressive cancers account for a disproportionate amount of the cancer morbidity and mortality in children, and have seen few advances in survival in the past decade, despite many large, complicated, and expensive trials of various chemotherapy combinations. To improve the outcomes of children with bone sarcomas, a better understanding of the biology of these cancers is needed, together with informed use of targeted therapies that exploit the unique biology of each disease. Here we summarize the current state of knowledge regarding the contribution of receptor tyrosine kinases, intracellular signaling pathways, bone biology and physiology, the immune system, and the tumor microenvironment in promoting and maintaining the malignant phenotype. These observations are coupled with a review of the therapies that target each of these mechanisms, focusing on recent or ongoing clinical trials if such information is available. It is our hope that, by better understanding the biology of osteosarcoma and Ewing sarcoma, rational combination therapies can be designed and systematically tested, leading to improved outcomes for a group of children who desperately need them.

Aflibercept a new target therapy in cancer treatment: a review

Angiogenesis is the process through which new blood vessels are formed from pre-existing vessels and is essential for the growth of all solid tumors. Vascular endothelial growth factor (VEGF) is a regulator of angiogenesis, which is crucial for tumor growth and metastasis. Its inhibition with antiangiogenic drugs is thought to improve delivery of chemotherapy through vascular normalization and disruption of tumor vasculature. Aflibercept is a recombinant fusion protein of the VEGF receptor (VEGFR)1 and VEGFR2 extracellular domains that binds to VEGF-A, VEGF-B, placental growth factor (PlGF) 1 and 2. Aflibercept has demonstrated preclinical efficacy in different tumor types and exerts its antiangiogenic effects through regression of tumor vasculature, remolding of vasculature, and inhibition of new tumor vessel growth. This review examines the effects of aflibercept on tumor vasculature and on different types of solid tumors, and explores the preclinical and clinical benefits of inclusion aflibercept into anticancer treatment strategies.

Expression profile of Twist, vascular endothelial growth factor and CD34 in patients with different phases of osteosarcoma

The aim of the present study was to investigate the clinical significance of Twist, vascular endothelial growth factor (VEGF) and CD34 expression in osteosarcoma (OS) in order to elucidate potential therapeutic targets for the treatment of OS. Immunohistochemistry was performed to detect the protein expression of Twist, VEGF and CD34 in OS and osteochondroma (OC) tissues. The ratio of the protein expression of Twist and VEGF in OS and OC tissues as well as at different phases of OS was compared using chi-squared tests. Microvessel density (MVD), as determined by CD34 labeling, in OS and OC tissue as well as at different phases of OS was compared using the Student's t-test. In addition, associations between Twist, VEGF and MVD were assessed using the Spearman's rank correlation test. The results revealed that out of the 32 OS tissues examined, 56.25% exhibited Twist positive expression, 71.88% exhibited VEGF positive expression and the MVD was increased compared with that of the OC tissue. The positive rate of Twist and VEGF expression in phase III OS tissues was significantly increased compared with that in phase I/II OS tissues (Twist: χ²=5.732, P=0.018; VEGF: χ²=7.513, P=0.006). The MVD in phase III OS tissues (31.08±3.36 per field) was significantly higher compared with that of the phase I/II OS tissues (41.2±4.17 per field; t=7.536, P<0.001). Spearman's rank correlation analysis revealed that Twist expression was positively associated with VEGF expression (r=0.371, P=0.002) and with MVD (r=0.393, P=0.001) in OS; in addition, VEGF expression was found to have a positive correlation with MVD (r=0.469, P=0.001). In conclusion, the results of the present study demonstrated that OS tissues exhibited elevated Twist and VEGF expression as well as MVD compared with OC tissue. In addition, metastatic OS (phase III) exhibited an increased positive rate of Twist and VEGF expression as well as MVD values compared with non-metastatic OS (phase I/II). Furthermore associations were detected between Twist and VEGF expression as well as VEGF and MVD. Therefore, inhibition of Twist expression may have potential therapeutic use for the treatment of OS.

A Case of Renal Primitive Neuroectodermal Tumor Confirmed by Fluorescence in situ Hybridization

Primitive neuroectodermal tumor (PNET) is a member of the Ewing's sarcoma family of tumors (ESFT). We report a case of PNET in a 66-year-old male who presented with a large solid tumor within the parenchyma of the middle pole of the left kidney with metastases to the left adrenal gland and right ischium. A fine-needle biopsy was performed and showed a small round cell tumor. Results of immunohistochemical staining suggested this tumor belonged to ESFT. Preoperative VDC-IE (combined vincristine, doxorubicin and cyclophosphamide followed by another combination of ifosfamide and etoposide) chemotherapy and left radical nephrectomy and adrenalectomy were performed. The histopathological findings of the resected tumor were similar to those in the biopsy specimen, but the results of AE1/AE3 were different. For the diagnosis, fluorescence in situ hybridization was performed. Split signals of the EWSR1 gene were detected, and transmission electron microscopy showed neuroendocrine granules and microtubules. The final diagnosis of this tumor was PNET of the kidney.

3D tissue-engineered model of Ewing's sarcoma

Despite longstanding reliance upon monolayer culture for studying cancer cells, and numerous advantages from both a practical and experimental standpoint, a growing body of evidence suggests that more complex three-dimensional (3D) models are necessary to properly mimic many of the critical hallmarks associated with the oncogenesis, maintenance and spread of Ewing's sarcoma (ES), the second most common pediatric bone tumor. And as clinicians increasingly turn to biologically-targeted therapies that exert their effects not only on the tumor cells themselves, but also on the surrounding extracellular matrix, it is especially important that preclinical models evolve in parallel to reliably measure antineoplastic effects and possible mechanisms of de novo and acquired drug resistance. Herein, we highlight a number of innovative methods used to fabricate biomimetic ES tumors, encompassing both the surrounding cellular milieu and the extracellular matrix (ECM), and suggest potential applications to advance our understanding of ES biology, preclinical drug testing, and personalized medicine.

Antitumor activity of lenvatinib (e7080): an angiogenesis inhibitor that targets multiple receptor tyrosine kinases in preclinical human thyroid cancer models

Inhibition of tumor angiogenesis by blockading the vascular endothelial growth factor (VEGF) signaling pathway is a promising therapeutic strategy for thyroid cancer. Lenvatinib mesilate (lenvatinib) is a potent inhibitor of VEGF receptors (VEGFR1–3) and other prooncogenic and prooncogenic receptor tyrosine kinases, including fibroblast growth factor receptors (FGFR1–4), platelet derived growth factor receptor α (PDGFRα), KIT, and RET. We examined the antitumor activity of lenvatinib against human thyroid cancer xenograft models in nude mice. Orally administered lenvatinib showed significant antitumor activity in 5 differentiated thyroid cancer (DTC), 5 anaplastic thyroid cancer (ATC), and 1 medullary thyroid cancer (MTC) xenograft models. Lenvatinib also showed antiangiogenesis activity against 5 DTC and 5 ATC xenografts, while lenvatinib showed in vitro antiproliferative activity against only 2 of 11 thyroid cancer cell lines: that is, RO82-W-1 and TT cells. Western blot analysis showed that cultured RO82-W-1 cells overexpressed FGFR1 and that lenvatinib inhibited the phosphorylation of FGFR1 and its downstream effector FRS2. Lenvatinib also inhibited the phosphorylation of RET with the activated mutation C634W in TT cells. These data demonstrate that lenvatinib provides antitumor activity mainly via angiogenesis inhibition but also inhibits FGFR and RET signaling pathway in preclinical human thyroid cancer models.

Proliferation index: a continuous model to predict prognosis in patients with tumours of the Ewing's sarcoma family

The prognostic value of proliferation index (PI) and apoptotic index (AI), caspase-8, -9 and -10 expression have been investigated in primary Ewing's sarcoma family of tumours (ESFT). Proliferating cells, detected by immunohistochemistry for Ki-67, were identified in 91% (91/100) of tumours with a median PI of 14 (range 0-87). Apoptotic cells, identified using the TUNEL assay, were detected in 96% (76/79) of ESFT; the median AI was 3 (range 0-33). Caspase-8 protein expression was negative (0) in 14% (11/79), low (1) in 33% (26/79), medium (2) in 38% (30/79) and high (3) in 15% (12/79) of tumours, caspase-9 expression was low (1) in 66% (39/59) and high (3) in 34% (20/59), and caspase-10 protein was low (1) in 37% (23/62) and negative (0) in 63% (39/62) of primary ESFT. There was no apparent relationship between caspase-8, -9 and -10 expression, PI and AI. PI was predictive of relapse-free survival (RFS; p = 0.011) and overall survival (OS; p = <0.001) in a continuous model, whereas AI did not predict outcome. Patients with tumours expressing low levels of caspase-9 protein had a trend towards a worse RFS than patients with tumours expressing higher levels of caspase-9 protein (p = 0.054, log rank test), although expression of caspases-8, -9 and/or -10 did not significantly predict RFS or OS. In a multivariate analysis model that included tumour site, tumour volume, the presence of metastatic disease at diagnosis, PI and AI, PI independently predicts OS (p = 0.003). Consistent with previous publications, patients with pelvic tumours had a significantly worse OS than patients with tumours at other sites (p = 0.028); patients with a pelvic tumour and a PI≥20 had a 6 fold-increased risk of death. These studies advocate the evaluation of PI in a risk model of outcome for patients with ESFT.

Lenvatinib in combination with golvatinib overcomes hepatocyte growth factor pathway-induced resistance to vascular endothelial growth factor receptor inhibitor

Vascular endothelial growth factor receptor (VEGFR) inhibitors are approved for the treatment of several tumor types; however, some tumors show intrinsic resistance to VEGFR inhibitors, and some patients develop acquired resistance to these inhibitors. Therefore, a strategy to overcome VEGFR inhibitor resistance is urgently required. Recent reports suggest that activation of the hepatocyte growth factor (HGF) pathway through its cognate receptor, Met, contributes to VEGFR inhibitor resistance. Here, we explored the effect of the HGF/Met signaling pathway and its inhibitors on resistance to lenvatinib, a VEGFR inhibitor. In in vitro experiments, addition of VEGF plus HGF enhanced cell growth and tube formation of HUVECs when compared with stimulation by either factor alone. Lenvatinib potently inhibited the growth of HUVECs induced by VEGF alone, but cells induced by VEGF plus HGF showed lenvatinib resistance. This HGF-induced resistance was cancelled when the Met inhibitor, golvatinib, was added with lenvatinib. Conditioned medium from tumor cells producing high amounts of HGF also conferred resistance to inhibition by lenvatinib. In s.c. xenograft models based on various tumor cell lines with high HGF expression, treatment with lenvatinib alone showed weak antitumor effects, but treatment with lenvatinib plus golvatinib showed synergistic antitumor effects, accompanied by decreased tumor vessel density. These results suggest that HGF from tumor cells confers resistance to tumor endothelial cells against VEGFR inhibitors, and that combination therapy using VEGFR inhibitors with Met inhibitors may be effective for overcoming resistance to VEGFR inhibitors. Further evaluation in clinical trials is warranted.

The potential of heparanase as a therapeutic target in cancer

Heparanase has generated substantial interest as therapeutic target for antitumor therapy, because its activity is implicated in malignant behavior of cancer cells and in tumor progression. Increased heparanase expression was found in numerous tumor types and correlates with poor prognosis. Heparanase, an endoglucuronidase responsible for heparan sulfate cleavage, regulates the structure and function of heparan sulfate proteoglycans, leading to disassembly of the extracellular matrix. The action of heparanase is involved in multiple regulatory events related, among other effects, to augmented bioavailability of growth factors and cytokines. Inhibitors of heparanase suppress tumor growth, angiogenesis and metastasis by modulating growth factor-mediated signaling, ECM barrier function and cell interactions in the tumor microenvironment. Therefore, targeting heparanase has potential implications for anti-tumor, anti-angiogenic and anti-inflammatory therapies. Current approaches for heparanase inhibition include development of chemically modified heparins, small molecule inhibitors and neutralizing antibodies. The available evidence supports the emerging utility of heparanase inhibition as a promising antitumor strategy, specifically in rational combination with other agents. The recent studies with compounds designed to block heparanase (e.g., modified heparins) provide a rational basis for their therapeutic application and optimization.

Anti-angiogenic therapy, a new player in the field of sarcoma treatment

Sarcomas encompass a heterogeneous family of mesenchymal malignancies. In metastatic disease improvement in outcome has been limited and there is a clear need for the development of new therapies. One potential target is angiogenesis, already an accepted target for treatment of more prevalent cancers. Multiple (pre)clinical studies focused on the role of angiogenesis and anti-angiogenic treatment in sarcomas. However, getting significant results is complicated due to the relatively small number of patients and the broad range of sarcoma subtypes. Recently, pazopanib has been approved for the treatment of advanced soft tissue sarcoma patients, which is an important step forward and paves the way for the introduction of anti-angiogenic treatment in sarcomas. However, more studies are needed to understand the biological mechanisms by which patients respond to angiogenic inhibitors and to detect markers of response. This review covers the knowledge that has been gained on the role of angiogenesis and anti-angiogenic therapy in sarcomas.

Optimal management of Ewing sarcoma family of tumors: recent developments in systemic therapy

The Ewing sarcoma family of tumors (ESFT) is defined by cell surface expression of CD99 and a translocation involving EWS and an ETS partner. Cytotoxic chemotherapy remains the benchmark of first- and second-line therapy, and although the majority of patients with localized disease are cured, almost one third of patients relapse or progress from their disease. Moreover, cure remains elusive in most patients who present with distant metastases. In recent years, the ESFT literature has been dominated by reports of attempts at modulating the insulin-like growth factor (IGF) receptor (IGFR). Unfortunately, three phase II studies examining inhibiting antibodies to IGFR-1 published disappointing results. Whether these results were due to failure to modulate the pathway or other limitations in study design and/or patient selection remain unclear. Other novel strategies currently being investigated in ESFT include tyrosine kinase, mammalian target of rapamycin (mTOR), and poly(ADP-ribose) polymerase (PARP) inhibitors.

Pilot study of vincristine, oral irinotecan, and temozolomide (VOIT regimen) combined with bevacizumab in pediatric patients with recurrent solid tumors or brain tumors

BACKGROUND

The combination of vincristine, oral irinotecan, and temozolomide (VOIT regimen) has shown antitumor activity in a pediatric Phase I trial. To further potentiate synergy, we assessed the safety and feasibility of adding bevacizumab to VOIT for children and young adults with recurrent tumors.

METHODS

Patients received vincristine (1.5 mg/m(2) on day 1), oral irinotecan (90 mg/m(2) on days 1-5), temozolomide (100-150 mg/m(2) on days 1-5), and bevacizumab (15 mg/kg on day 1) in 3-week cycles, which were repeated for up to six cycles. Cefixime prophylaxis was used to reduce irinotecan-associated diarrhea.

RESULTS

Thirteen patients received 36 total cycles. Six of the first 10 patients required dose reductions due to toxicity during the first cycle (n = 3) or subsequent cycles (n = 3), and these grade 3 side effects included prolonged nausea, dehydration, anorexia, neuropathy, diarrhea, and abdominal pain, as well as prolonged grade 4 neutropenia. After reducing daily temozolomide to 100 mg/m(2) , three additional patients tolerated therapy well without the need for dose reductions. Toxicities attributed to bevacizumab were limited to grade 1 epistaxis (1) and grade 2 proteinuria (1). Tumor responses were seen in both patients with Ewing sarcoma.

CONCLUSIONS

Reducing temozolomide from 150 to 100 mg/m(2) /day improved tolerability, and treatment with this lower temozolomide dose was feasible and convenient as outpatient therapy. Although responses were seen in Ewing sarcoma, the benefit of adding bevacizumab remains unclear.

Membrane expression of MRP-1, but not MRP-1 splicing or Pgp expression, predicts survival in patients with ESFT

Background:

Primary Ewing's sarcoma family of tumours (ESFTs) may respond to chemotherapy, although many patients experience subsequent disease recurrence and relapse. The survival of ESFT cells following chemotherapy has been attributed to the development of resistant disease, possibly through the expression of ABC transporter proteins.

Methods:

MRP-1 and Pgp mRNA and protein expression in primary ESFTs was determined by quantitative reverse-transcriptase PCR (RT-qPCR) and immunohistochemistry, respectively, and alternative splicing of MRP-1 by RT-PCR.

Results:

We observed MRP-1 protein expression in 92% (43 out of 47) of primary ESFTs, and cell membrane MRP-1 was highly predictive of both overall survival (P<0.0001) and event-free survival (P<0.0001). Alternative splicing of MRP-1 was detected in primary ESFTs, although the pattern of splicing variants was not predictive of patient outcome, with the exception of loss of exon 9 in six patients, which predicted relapse (P=0.041). Pgp protein was detected in 6% (38 out of 44) of primary ESFTs and was not associated with patient survival.

Conclusion:

For the first time we have established that cell membrane expression of MRP-1 or loss of exon 9 is predictive of outcome but not the number of splicing events or expression of Pgp, and both may be valuable factors for the stratification of patients for more intensive therapy.

BIRC5 expression is a poor prognostic marker in Ewing sarcoma

BACKGROUND

BIRC5 (Survivin), an inhibitor of apoptosis protein (IAP), is over-expressed in several human cancers and increased expression is associated with poor prognosis. The goal of the current study was to evaluate the role of BIRC5 in Ewing sarcoma (ES), the second most common pediatric bone sarcoma.

PROCEDURE

BIRC5 protein expression was determined in ES cell lines using Western Blot analysis. Functional role of survivin on growth and viability of ES cells was assessed by siRNA knockdown of BIRC5 and by using a small molecule inhibitor YM155. Immunohistochemical analysis for BIRC5 protein was performed on patient tumor samples using an anti-survivin antibody. The degree of BIRC5 protein expression was correlated with clinical parameters and patient outcome.

RESULTS

BIRC5 is over-expressed in a panel of ES cell lines. Gene silencing of BIRC5 in the ES cell line TC-71 decreases cell growth by more than 50% for each BIRC5 siRNA construct compared to non-silencing siRNA control constructs. YM155 also reduces ES cell growth and viability with an EC(50) ranging from 2.8 to 6.2 nM. BIRC5 protein is expressed in majority of the ES tumor samples with minimal expression in normal tissue (P < 0.005). Tumors with more than 50% expression are associated with worse overall survival than tumors with less than 50% expression (Hazard Ratio: 6.05; CI: 1.7-21.4; P = 0.04).

CONCLUSION

BIRC5 is over-expressed in ES cell lines and tumor samples. Further, it plays an important role in cell growth and viability in vitro. Higher degree of expression in patients is an independent poor prognostic factor.

Systemic analysis of gene expression profiles identifies ErbB3 as a potential drug target in pediatric alveolar rhabdomyosarcoma

Pediatric sarcomas, including rhabdomyosarcomas, Ewing's sarcoma, and osteosarcoma, are aggressive tumors with poor survival rates. To overcome problems associated with nonselectivity of the current therapeutic approaches, targeted therapeutics have been developed. Currently, an increasing number of such drugs are used for treating malignancies of adult patients but little is known about their effects in pediatric patients. We analyzed expression of 24 clinically approved target genes in a wide variety of pediatric normal and malignant tissues using a novel high-throughput systems biology approach. Analysis of the Genesapiens database of human transcriptomes demonstrated statistically significant up-regulation of VEGFC and EPHA2 in Ewing's sarcoma, and ERBB3 in alveolar rhabdomyosarcomas. In silico data for ERBB3 was validated by demonstrating ErbB3 protein expression in pediatric rhabdomyosarcoma in vitro and in vivo. ERBB3 overexpression promoted whereas ERBB3-targeted siRNA suppressed rhabdomyosarcoma cell gowth, indicating a functional role for ErbB3 signaling in rhabdomyosarcoma. These data suggest that drugs targeting ErbB3, EphA2 or VEGF-C could be further tested as therapeutic targets for pediatric sarcomas.

Disseminated Intracranial Ewing's Sarcoma in an Adult: A Rare and Difficult Diagnosis

The Ewing sarcoma family of tumors comprises a rare class of cancers of mesenchymal origin. Cases of Ewing's sarcoma in the central nervous system – specifically, intracranial Ewing's – are extremely rare. Almost all reported cases have occurred in children. However, this rare presentation can also occur in the adult population. It is important to distinguish these tumors from primitive neuroectodermal tumors at the time of diagnosis. Testing for EWSR1(22q12) gene rearrangement using fluorescence in situ hybridization is a useful tool for making the distinction between these 2 similar but distinct entities. We present here the case of a middle-aged male patient with intracranial Ewing's sarcoma, and discuss diagnostic challenges and potential new treatment approaches for this rare disease.

Targeted therapies in sarcomas: challenging the challenge

Sarcomas are a heterogeneous group of mesenchymal malignancies that very often lead to death. Nowadays, chemotherapy is the only available treatment for most sarcomas but there are few active drugs and clinical results still remain very poor. Thus, there is an imperious need to find new therapeutic alternatives in order to improve sarcoma patient's outcome. During the last years, there have been described a number of new molecular pathways that have allowed us to know more about cancer biology and tumorigenesis. Sarcomas are one of the tumors in which more advances have been made. Identification of specific chromosomal translocations, some important pathways characterization such as mTOR pathway or the insulin-like growth factor pathway, the stunning development in angiogenesis knowledge, and brand new agents like viruses have lead to the development of new therapeutic options with promising results. This paper makes an exhaustive review of preclinical and clinical evidence of the most recent targeted therapies in sarcomas and provides a future view of treatments that may lead to improve prognosis of patients affected with this disease.

Expression of vascular endothelial growth factor in Ewing's sarcoma

PURPOSE

Vascular endothelial growth factor (VEGF) is the most potent stimulator of angiogenesis. The aim of this study was to evaluate the role of serum VEGF as a diagnostic, predictive and prognostic marker in Ewing's sarcoma.

METHODS

Patients with histopathologically proven diagnosis of Ewing's sarcoma without prior chemotherapy or radiotherapy were invited to take part in the study. Pre-chemotherapy, post-chemotherapy and post-surgery blood samples were collected for analysis of serum VEGF levels. Blood samples from ten sex- and age-matched healthy volunteers were collected for estimation of VEGF levels to act as control. Human VEGF Elisa kit (Bender Medsystem, Austria) was used to assess the serum VEGF levels.

RESULTS

A total of nine cases of Ewing's sarcoma were included in the study. Mean age in the group was 12.44 years (range, seven to 18 years). Mean and median serums VEGF level in the study population were 4,547.78 pg/ml and 3,780.00 pg/ml, respectively. Ten age- and sex-matched healthy volunteers were selected as controls. No significant correlation was obtained between serum VEGF, age, sex and tumour size. Mean serum VEGF was significantly raised in the study group as compared to controls (p = 0.001). We observed a significant decline in serum VEGF level following neoadjuvant chemotherapy (p = 0.008). No correlation could be established between serum VEGF level pulmonary metastasis and overall survival.

CONCLUSION

Serum VEGF might have a role as a diagnostic and predictive marker in patients with Ewing's sarcoma.

Head and neck lymphatic tumors and bony abnormalities: a clinical and molecular review

Lymphatic malformations and lymphatic-derived tumors commonly involve the head and neck, where they may be associated with bony abnormalities and other systemic symptoms. The reasons for the association between these disorders and local skeletal changes are largely unknown, but such changes may cause significant disease-related morbidity. Ongoing work in molecular and developmental biology is beginning to uncover potential reasons for the bony abnormalities found in head and neck lymphatic disease; this article summarizes current knowledge on possible mechanisms underlying this association.

ETV1, 4 and 5: an oncogenic subfamily of ETS transcription factors

The homologous ETV1, ETV4 and ETV5 proteins form the PEA3 subfamily of ETS transcription factors. In Ewing tumors, chromosomal translocations affecting ETV1 or ETV4 are an underlying cause of carcinogenesis. Likewise, chromosomal rearrangements of the ETV1, ETV4 or ETV5 gene occur in prostate tumors and are thought to be one of the major driving forces in the genesis of prostate cancer. In addition, these three ETS proteins are implicated in melanomas, breast and other types of cancer. Complex posttranslational modifications govern the activity of PEA3 factors, which can promote cell proliferation, motility and invasion. Here, we review evidence for a role of ETV1, 4 and 5 as oncoproteins and describe modes of their action. Modulation of their activation or interaction with cofactors as well as inhibiting crucial target gene products may ultimately be exploited to treat various cancers that are dependent on the PEA3 group of ETS transcription factors.

An unusual case of congenital primitive neuroectodermal tumor with ocular metastasis

Primitive neuroectodermal tumor (PNET) is most common in the second decade of life. Congenital PNET is very rare. Ocular metastasis of PNET is likewise exceedingly rare; with only 5 previously published cases. We report an unusual congenital PNET of the face, which metastasized to subcutis, eyes, and brain. The primary tumor responded to chemotherapy (vincristine/doxorubicin/cyclophosphamide) with metachronous progression of ocular lesions. A therapeutic trial of intraocular bevacizumab showed no efficacy on intraocular lesions. Eventually the patient developed cerebral metastasis, and second line therapy with topotecan/cyclophosphamide was initiated. The tumor progressed and the patient died after acute herniation.

Ewing sarcoma: biology-based therapeutic perspectives

Ewing sarcoma, a rare malignancy of childhood and adolescence, has attracted wide research interest. Tumor-specific chromosomal translocations generate aberrant EWS-ETS transcription factors, which alter intracellular signaling networks through gene and protein expression and are considered to be the primary tumor-initiating event. Ewing sarcoma therefore offers insights into principle molecular mechanisms of cancer development and maintenance. Still, despite long-standing research, biology-based targeted treatment strategies for Ewing sarcoma are only beginning to emerge. This article provides an overview of the biological basis and putative targeted treatment options.

Expression of therapeutic targets in Ewing sarcoma family tumors

Ewing sarcoma family tumor is an aggressive malignant tumor of bone and soft tissue in children and adolescents. Despite advances in modern therapy, metastasis occurs in 20% to 25% of cases and results in mortality in 80% of patients. Intracellular molecules mammalian target of rapamycin, Akt, vascular endothelial growth factor, nuclear factor κB, and BRAF are important kinases and transcription factors that regulate the proliferation of tumor cells. We studied the expression of these proteins in 72 Ewing sarcoma family tumors. Patients' survival data were available in 55 cases. Formalin-fixed, paraffin-embedded tumor sections were stained with antibodies against phosphorylated mammalian target of rapamycin, Akt, BRAF, vascular endothelial growth factor, and nuclear factor κB proteins. Stained sections were analyzed for percentage and strength of staining, and a composite score (0-200) was subsequently generated. Although most tumors expressed mammalian target of rapamycin, Akt, nuclear factor κB, and vascular endothelial growth factor, only 37%, 86%, 55%, and 12%, respectively, showed high expression (staining score ≥ 100). There was no significant correlation between mammalian target of rapamycin and Akt expression and clinical outcome. High nuclear factor κB expression was significantly associated with tumors in pelvic locations. Decreased vascular endothelial growth factor expression (score <100) was significantly associated with better prognosis (P < .05). BRAF was not expressed in most cases and showed negative or weak staining (score <100) in 97% of cases. Thus, except for BRAF, Ewing sarcoma family tumors may be amenable to treatment that targets the expressed proteins. High Akt expression suggests potential universal response to Akt-targeted therapy. BRAF kinase inhibitors are unlikely to be effective in the treatment of Ewing sarcoma family tumors.

Tumor Vessel Development and Expansion in Ewing's Sarcoma: A Review of the Vasculogenesis Process and Clinical Trials with Vascular-Targeting Agents

Ewing's sarcoma accounts for a disproportionately high portion of the overall pediatric mortality rate compared to its rare incidence in the pediatric population. Little progress has been made since the introduction of traditional chemotherapies, and understanding the biology of the tumor is critical for developing new therapies. Ewing's sarcomas rely on a functional vascular supply, which is formed by a combination of angiogenesis and vasculogenesis. Recent insights into the molecular regulation of bone marrow (BM) cell participation in vascular development have identified VEGF, SDF-1α, and DLL4 as critical players in the vasculogenesis process. Clinical trials using vascular targeting agents, specifically targeting VEGF or DLL4, are underway.

Characteristics of human Ewing/PNET sarcoma models

Ewing/PNET (peripheral neuroepithelioma) tumors are rare aggressive bone sarcomas occurring in young people. Rare-disease clinical trials can require global collaborations and many years. In vivo models that as accurately as possible reflect the clinical disease are helpful in selecting therapeutics with the most promise of positive clinical impact. Human Ewing/PNET sarcoma cell lines developed over the past 45 years are described. Several of these have undergone genetic analysis and have been confirmed to be those of Ewing/PNET sarcoma. The A673 Ewing sarcoma line has proven to be particularly useful in understanding the biology of this disease in the mouse. The chromosomal translocation producing the EWS/FLI1 fusion transcript characterizes clinical Ewing sarcoma. Cell lines that express this genetic profile are confirmed to be those of Ewing sarcoma. The A673 Ewing sarcoma line grows in culture and as a xenograft in immunodeficient mice. The A673 model has been used to study Ewing sarcoma angiogenesis and response to antiangiogenic agents. Many Ewing sarcoma clinical specimens express the cell surface protein endosialin. Several Ewing sarcoma cell lines, including the A673 line, also express cell surface endosialin when grown as subcutaneous tumor nodules and as disseminated disease; thus the A673 is a useful model for the study of endosialin biology and endosialin-directed therapies. With the advent of tools that allow characterization of clinical disease to facilitate optimal treatment, it becomes imperative, especially for rare tumors, to develop preclinical models reflecting disease subsets. Ewing PNET sarcomas are a rare disease where models are available.