Treatment Of Ewing Sarcoma Research Articles

Comparison of treatment effect and long-term outcomes for pediatric and adult Ewing sarcoma patients in British Columbia, Canada.

11531 Background: Treatment of Ewing Sarcoma (EWS) is challenging. While it is known to be sensitive to chemotherapy and radiation, the number of lines of therapy available are limited. This disease affects pediatric patients (PP) more often than adults (AP), and reported outcomes are worse for AP onset EWS in the literature. It is unclear if this is due to difference in the biology of disease in AP compared to PP, or if this is due to differences in treatment approach. Furthermore, optimal treatments and real world impact of treatment is unclear in both the PP and AP populations. This study identifies the features of therapy received by AP and PP with EWS in a large, mutli-institutional cohort, and provides real world evidence for the expected outcomes in both AP and PP with EWS. Methods: A cohort study analysis of the Sarcoma Outcomes Unit database at BC Cancer was conducted to identify patients diagnosed with EWS in British Columbia from January 1, 2000 to December 31, 2018. Data on the frequency, amount, and regimen of chemotherapy were collected. Baseline Charlson comorbidity index, age at diagnosis, progression free survival and overall survival were collected. Results: 108 patients with EWS were identified, 66 AP and 42 PP Median age at diagnosis for adults was 37 (19-86) and median age for diagnosis of pediatric patients was 14 (1-18). Real world median PFS and OS for AP were 23 mos and 79 mos, and for the PP were 32 mos and NE. Five year overall survival was 54% in AP and 77% in PP. Overall, there was no difference in the number of lines of therapy received between PP and AP, but the type of therapy was more dose-dense in the PP than in the AP, (85% vs 28% for dose dense chemo). 5 year overall survival was longer for PP who received dose dense regimens compared to non-dose dense regimens (HR 0.87), but was not different in the AP receiving dose dense regimens (HR 0.95), even when controlling for comorbidities. The most common chemotherapy regimen for AP was Vincristine, Adriamycin, cyclophosphamide alternating with Ifosfamide and Etoposide q3weeks, whereas in the pediatric population the most common chemotherapy regimen was the same but alternating q2weeks. Conclusions: The treatment plans for PP with EWS were more often dose dense compared to the AP. Outcomes for PP were vastly better than for APs, despite overall similarities in the number of lines of therapy and types of agents used. Given the lack of difference between dose dense and non-dose dense regimens for APs, this is not the likely cause of difference in survival between PPs and APs. Extrapolating pediatric protocols to the adult setting may not be appropriate given the differences in outcomes. Further work to identify effective therapies and predictive biomarkers in this disease are needed, and my further identify reasons for discrepant outcomes in pediatric and adult populations.

Phase 1 trial of seclidemstat (SP-2577) in patients with relapsed/refractory Ewing sarcoma.

11514 Background: Ewing sarcoma (ES), a rare bone and soft tissue sarcoma mainly of adolescents and young adults, is characterized by a chromosomal translocation resulting in a fusion oncoprotein. Lysine specific demethylase 1 (LSD1) has been shown to associate with the fusion oncoprotein and promote oncogenic transcriptional activity making LSD1 an attractive target for ES treatment. Seclidemstat is a novel, selective, reversible oral LSD1 inhibitor capable of inhibiting both LSD1’s catalytic and scaffolding functions. This is the first report of an LSD1 inhibitor in a Phase 1 trial focused exclusively on ES. Methods: SALA-002-EW16 is a Phase 1 trial of single agent seclidemstat in patients (pts) with relapsed or refractory (R/R) ES. This report describes the completed monotherapy dose escalation. Pts > 12 years received oral SP-2577 twice daily in 28-day cycles under fasting conditions at the assigned dose level. The primary objective was safety and tolerability. Secondary objectives include to determine maximum-tolerated dose (MTD), recommended Phase 2 dose (RP2D), preliminary efficacy, pharmacokinetics, and pharmacodynamics. Results: As of December 30, 2020, 27 pts with R/R ES were enrolled. Pts received escalating doses of SP-2577 at 75 (n = 1), 150 (n = 2), 300 (n = 4), 600 (n = 6), 900 (n = 8), or 1200 mg PO BID (n = 6). The median age was 25 years (range 15–68), 63% were male, and pts had received a median of 3 (range 2–12) prior systemic therapies. There were no treatment-related deaths. The most common ( > 5%) grade 3 treatment-related adverse events (TRAEs) were vomiting (15%), abdominal pain (11%), and hypokalemia (11%). One pt (4%) with grade 3 pancreatitis reported a grade 4 AE of elevated lipase. All remaining grade 3 TRAEs, including hematological TRAEs, were reported in only one pt each. Four pts discontinued study for an AE (weight loss, pancreatitis, vomiting, abdominal pain). Three pts had a dose reduction. The first cycle dose-limiting toxicities were gastrointestinal-related AEs observed in 2 pts at 1200 mg BID. Thus, the MTD/RP2D was established as 900 mg BID. Peak plasma concentrations occurred at a median of 4 hours (h) post-dose and median terminal half-life was 6 h; exposure was dose proportional through 900 mg BID. One pt at 600 mg BID achieved a reduction in target lesions starting at end of C2 with further target lesion tumor shrinkage through end of C4 and C6 (maximum 76% tumor shrinkage) with coincident new non-target lesion appearance at end of C2. Of pts evaluable for response at the end of C2 (12 pts), two additional pts (16.7%) at 600 mg BID and 900 mg BID had overall stable disease. Conclusions: Seclidemstat has a manageable safety profile with proof-of-concept preliminary activity in heavily pretreated pts with relapsed/refractory ES. These data support the planned Phase 2 expansion of seclidemstat as single agent and in combination with chemotherapy in ES and other sarcomas that share similar translocations. Clinical trial information: NCT03600649.

Natural and Synthetic Cannabinoids Reduce Cell Viability of Ewing Sarcoma TC‐71 Cells Potentially via Non‐canonical CB receptors

Ewing Sarcoma (EWS) is the second most common bone tumor in children, characterized by rapid tumor growth and extensive bone destruction. Treatment for EWS is multimodal: surgery, radiation, and chemotherapy. However, these approaches are effective in only 70% of the patients with localized disease and thus new drugs are needed. WIN-55,212-2 (WIN-2), a synthetic cannabinoid in the aminoalkyindole (AI) class, has been shown to slow tumor growth in several types of cancer and human Kaposi sarcoma via cannabinoid (CB) and non-CB mechanisms. Therefore, we hypothesize that WIN-2 and other synthetic CBs will exhibit anti-proliferative effects in EWS TC-71 cells via CB receptors. Competitive binding screens using TC-71 membranes showed that binding of the nonselective CB1/CB2 radiolabeled agonist [3H]CP-55,940 could not be displaced by selective CB1 or CB2 ligands, or even non-radioactive CP-55,940 itself. However, binding of a second nonselective CB1/CB2 radiolabeled agonist [3H]WIN-2 could be displaced with a CB1 but not CB2 antagonist, and non-radioactive WIN-2 itself. This suggests that TC-71 cells express a novel non-canonical CB binding site (WIN-2 site). Subsequent homologous receptor binding studies with [3H]WIN-2 showed that TC-71 cells do indeed express a WIN-2 site at a density (Bmax) of 3.7 +/- 1.6 pmole/mg, to which WIN-2 binds with an affinity (Ki) of 4.5 +/- 0.6 nM. Next, thirty-eight different synthetic CBs were screened for potential binding to WIN-2 receptors in TC-71 cells. Only four compounds exhibited a high affinity for the WIN-2 receptor in the low to the mid-nanomolar range. Interestingly, four other compounds increased [3H]WIN-2 binding, indicating that these ligands might act as positive allosteric modulators of the WIN-2 site. When compounds with the highest affinity were examined in G-protein activation assays for functional activity, two of them reduced [35S]GTPgS binding below basal levels indicating that they may act as inverse agonists at the novel WIN-2 site. Most importantly, WIN-2 and all four compounds with high affinity for the WIN-2 site produced a significant time-dependent reduction in viability of EWS TC-71 cells as measured by trypan blue exclusion and lactate dehydrogenase (LDH) release. In conclusion, WIN-2 and other synthetic CBs reduce EWS cell viability potentially via a non-canonical CB binding site. These results suggest that the WIN-2 site might be a novel therapeutic target for drug development to treat EWS and perhaps other types of cancer as well.

The miR-146b-5p promotes Ewing's sarcoma cells progression via suppressing the expression of BTG2.

Ewing sarcoma (ES) is a malignant tumor that occurs mostly in children. However, the underlying mechanisms of ES are still unknown. Analyzing the results of two previous miRNA array reports, we found that miR-146b-5p might be an onco-miRNA in ES progression. To test this hypothesis, we detected the expression levels of miR-146b-5p by real-time PCR and observed the effects of miR-146b-5p on the progression of ES cells by CCK8 and transwell assays. Bioinformatics and luciferase assays were used to identify the target genes of miR-146b-5p. It showed that the expression levels of miR-146b-5p were upregulated in ES cell lines compared with human mesenchymal stem cells (MSCs). Up- or downregulation of miR-146b-5p in ES cell lines could effectively promote or block the proliferation, migration, and invasion of ES cells, respectively. Furthermore, we demonstrated that BTG2 was one of the target genes and mediated the effects of miR-146b-5p in ES cells. Interestingly, we also found that miR-146b-5p was partly involved in the anticancer effects of pemetrexed in ES cells. Our study revealed that miR-146b-5p affected the progression of ES by suppressing BTG2, which might shed light on anticancer drug development and ES treatment in the future.

Impact of location of inpatient cancer care on patients with Ewing sarcoma and osteosarcoma-A population-based study.

Ewing sarcoma (EWS) and osteosarcoma (OS) require multidisciplinary treatment. Care at specialized cancer centers (SCC: Children's Oncology Group affiliated and/or National Cancer Institute-designated cancer center) has been found to improve outcomes in patients with leukemia, but studies have not considered location of care and outcomes in EWS and OS patients, an ideal group to evaluate given their specialized multidisciplinary treatment needs. Patients hospitalized with primary EWS and OS (2000-2014) were identified using the California Cancer Registry linked with hospitalization data. Patients were divided into age groups (0-18, 19-39, ≥40years), and classified on whether they received all versus part/none of their inpatient treatment at a SCC within 1year of diagnosis. Multivariable Cox proportional hazards regression identified factors associated with survival. There were 531 ES and 959 OS patients. Five-year overall survival was better for patients with EWS (all: 63% vs. part/none: 42%) and OS (all: 64% vs. part/none: 47%) who received all of their treatment at a SCC. After adjusting for sociodemographic and clinical factors, receiving all inpatient cancer treatment at a SCC was associated with superior overall survival (EWS HR: 0.49, CI 0.37-0.67; OS HR: 0.78, CI 0.63-0.97). Our results suggest that treatment for EWS and OS at a SCC is associated with significantly improved survival even after adjustment for known prognostic factors. The superior survival among those treated at SCCs may be due to having greater access to clinical trials and services at SCCs.

Current Status of Management and Outcome for Patients with Ewing Sarcoma.

Simple SummaryEwing sarcoma is a highly aggressive malignancy affecting primarily children and adolescents. It is the second most common bone sarcoma among children, affecting between 1 and 3 persons per million inhabitants. The tumor typically carries a pathognomonic chromosomal translocation resulting in a fusion transcript (EWSR1-FLI1), which plays an orchestral role in tumor development. While the fusion transcript has been known for decades, targeted treatment has been disappointing. However, new molecular techniques such as next-generation sequencing have significantly increased our understanding of this rare disease. Moreover, new closely related tumors with similar morphology but different characteristics have evolved. Treatment today consists of multiagent chemotherapy, radiation treatment, and surgery, all of which are associated with significant short- and long-term side effects. In this review article, we describe the currently existing diagnostic- and treatment-related challenges as well as the most important ongoing or recently conducted studies.Ewing sarcoma is the second most common bone sarcoma in children after osteosarcoma. It is a very aggressive malignancy for which systemic treatment has greatly improved outcome for patients with localized disease, who now see survival rates of over 70%. However, for the quarter of patients presenting with metastatic disease, survival is still dismal with less than 30% of patients surviving past 5 years. Patients with disease relapse, local or distant, face an even poorer prognosis with an event-free 5-year survival rate of only 10%. Unfortunately, Ewing sarcoma patients have not yet seen the benefit of recent years’ technical achievements such as next-generation sequencing, which have enabled researchers to study biological systems at a level never seen before. In spite of large multinational studies, treatment of Ewing sarcoma relies entirely on chemotherapeutic agents that have been largely unchanged for decades. As many promising modern therapies, including monoclonal antibodies, small molecules, and immunotherapy, have been disappointing to date, there is no clear candidate as to which drug should be investigated in the next large-scale clinical trial. However, the mechanisms driving tumor development in Ewing sarcoma are slowly unfolding. New entities of Ewing-like tumors, with fusion transcripts that are related to the oncogenic EWSR1-FLI1 fusion seen in the majority of Ewing tumors, are being mapped. These tumors, although sharing much of the same morphologic features as classic Ewing sarcoma, behave differently and may require a different treatment. There are also controversies regarding local treatment of Ewing sarcoma. The radiosensitive nature of the disease and the tendency for Ewing sarcoma to arise in the axial skeleton make local treatment very challenging. Surgical treatment and radiotherapy have their pros and cons, which may give rise to different treatment strategies in different centers around the world. This review article discusses some of these controversies and reproduces the highlights from recent publications with regard to diagnostics, systemic treatment, and surgical treatment of Ewing sarcoma.

P21-activated kinases as viable therapeutic targets for the treatment of high-risk Ewing sarcoma.

Ewing sarcoma (ES) is the second most common bone tumor in children and young adults. Unfortunately, there have been minimal recent advancements in improving patient outcomes, especially in metastatic and recurrent diseases. In this study, we investigated the biological role of p21-activated kinases (PAKs) in ES, and the ability to therapeutically target them in high-risk disease. Via informatics analysis, we established the inverse association of PAK1 and PAK4 expression with clinical stage and outcome in ES patients. Through expression knockdown and small-molecule inhibition of PAKs, utilizing FRAX-597, KPT-9274, and PF-3758309 in multiple ES cell lines and patient-derived xenograft models, we further explored the role of PAKs in ES tumor growth and metastatic capabilities. In vitro studies in several ES cell lines indicated that diminishing PAK1 and PAK4 expression reduces tumor cell viability, migratory, and invasive properties. In vivo studies using PAK4 inhibitors, KPT-9274 and PF-3758309 demonstrated significant inhibition of primary and metastatic tumor formation, while transcriptomic analysis of PAK4-inhibitor-treated tumors identified concomitant suppression of Notch, β-catenin, and hypoxia-mediated signatures. In addition, the analysis showed enrichment of anti-tumor immune regulatory mechanisms, including interferon (IFN)-ɣ and IFN-α responses. Altogether, our molecular and pre-clinical studies are the first to establish a critical role for PAKs in ES development and progression, and consequently as viable therapeutic targets for the treatment of high-risk ES in the near future.

YAP/TAZ inhibition reduces metastatic potential of Ewing sarcoma cells

Ewing sarcoma (EwS) is a highly metastatic bone cancer characterized by the ETS fusion oncoprotein EWS-FLI1. EwS cells are phenotypically highly plastic and switch between functionally distinct cell states dependent on EWS-FLI1 fluctuations. Whereas EWS-FLI1high cells proliferate, EWS-FLI1low cells are migratory and invasive. Recently, we reported activation of MRTFB and TEAD, effectors of RhoA and Hippo signalling, upon low EWS-FLI1, orchestrating key steps of the EwS migratory gene expression program. TEAD and its co-activators YAP and TAZ are commonly overexpressed in cancer, providing attractive therapeutic targets. We find TAZ levels to increase in the migratory EWS-FLI1low state and to associate with adverse prognosis in EwS patients. We tested the effects of the potent YAP/TAZ/TEAD complex inhibitor verteporfin on EwS cell migration in vitro and on metastasis in vivo. Verteporfin suppressed expression of EWS-FLI1 regulated cytoskeletal genes involved in actin signalling to the extracellular matrix, effectively blocked F-actin and focal-adhesion assembly and inhibited EwS cell migration at submicromolar concentrations. In a mouse EwS xenograft model, verteporfin treatment reduced relapses at the surgical site and delayed lung metastasis. These data suggest that YAP/TAZ pathway inhibition may prevent EwS cell dissemination and metastasis, justifying further preclinical development of YAP/TAZ inhibitors for EwS treatment.

Eltrombopag inhibits the proliferation of Ewing sarcoma cells via iron chelation and impaired DNA replication

BackgroundThe treatment of Ewing sarcoma, an aggressive bone and soft tissue sarcoma, is associated with suboptimal outcomes and significant side-effects. Consequently, there is an urgent need to identify novel therapies that will improve outcomes for children and adults with Ewing sarcoma tumors while also decreasing treatment-related toxicities.MethodsWe analyzed data from the PRISM drug repurposing screen, which tested the activity of 4518 drugs across 578 cancer cell lines, to identify drugs that selectively inhibit the growth of Ewing sarcoma cell lines. We then tested the effects of a top hit from the screen on cell proliferation, cell cycle progression, and activation of the DNA damage pathway using Ewing sarcoma cell lines. We also used a CRISPR/Cas9 gene knockout approach to investigate the role of Schlafen 11 (SLFN11), a restriction factor for DNA replication stress that is overexpressed in Ewing sarcoma tumors, in mediating the sensitivity of Ewing sarcoma cells to the drug.ResultsWe found that eltrombopag, an FDA-approved thrombopoietin-receptor agonist (TPO-RA) that is currently being evaluated as a treatment for chemotherapy-induced thrombocytopenia, inhibits the growth of Ewing sarcoma cell lines in vitro in proliferation and colony formation assays. However, from a mechanistic standpoint, the thrombopoietin receptor is not expressed in Ewing sarcoma cells and we show that eltrombopag impairs DNA replication and causes DNA damage in Ewing sarcoma cells by chelating iron, a known “off-target” effect of the drug. We also found that the sensitivity of Ewing sarcoma cells to eltrombopag is mediated, in part, by SLFN11, which regulates the cellular response to DNA replication stress.ConclusionsEwing sarcoma cell lines are sensitive to eltrombopag and this drug could improve outcomes for patients with Ewing sarcoma tumors by both targeting the tumor, via chelation of iron and inhibition of DNA replication, and reducing chemotherapy-induced thrombocytopenia, via stimulation of the thrombopoietin receptor.

Seeking international consensus on approaches to primary tumour treatment in Ewing sarcoma

BackgroundThe local treatment of Ewing sarcoma of bone involves surgery, radiotherapy or both. The selection of treatment depends on the anatomical extent of the tumour, the effectiveness of the proposed treatment, its morbidity, and the expectation of cure. However, not only are there variations in the approach to local treatment between individual patients, but also between treatment centres and countries. Our aim was to explore variation in practice and develop consensus statements about local treatment.MethodsA three stage modified Delphi technique was used with international collaborators. This involved an expert panel to identify areas of controversy, an online survey of international collaborators and a consensus meeting in London, UK in June 2017. In the consensus meeting, teams of clinicians discussed the local management of selected cases and their responses were collected with electronic voting.ResultsAreas of greater or less consensus were identified. The lack of evidence underpinning different approaches was noted and areas for collaborative research became apparent.ConclusionThis has demonstrated that there is an international consensus around many aspects of the local treatment of Ewing sarcoma of bone, including the use of specialist MultiDisciplinary Team (MDT) meetings with access to all appropriate treatments. However, considerable variation remains including the use of different staging investigations, decision making, definitions of response, and radiotherapy doses and timing. Further collaborative work should be undertaken to determine the impact of these variations in order to define best practice.

Pain in survivors of Ewing sarcoma: Prevalence, associated factors and prediction of recurrence.

While the prognosis of patients with Ewing sarcoma (EwS) is improving, little is known about the frequency of pain and its risk factors in survivors of EwS. This study aims to analyse the prevalence and risk factors of pain and its predictive value for recurrence. In patients with remission after treatment of EwS, frequency and characteristics of pain within the first 5years of follow up were assessed retrospectively. Of 80 patients, 37 (46%) presented with at least one episode of pain. Chronic pain (>3months) was observed in 10 patients (13%). Experience of at least one episode of pain was associated with prior combined local treatment (surgery and radiation compared to surgery alone; odds ratio [OR] 5.83, 95% confidence interval [CI] 1.43-34.9, P=.007). A total of 59 episodes of pain were observed, including 47 acute and 12 chronic episodes. Lower limb pain accounted for 46% (27/59) of all episodes of pain, and was associated with primary tumour of the pelvis or lower extremity (OR 4.29, 95% CI 1.18-18.21, P=.025), which represented 64% (51/80) of all EwS. The positive predictive value of pain for recurrence was only 12%. Pain is a common problem in survivors of EwS, which mostly affects the lower extremity, and should be regularly assessed. Interventions to reduce pain may be particularly important in patients with combined local treatment with surgery and radiation, who seem to be at considerably increased risk for pain. Patients presenting with pain should be examined for recurrence.

Chemoimmunotherapy for the salvage treatment of Ewing sarcoma: A case report

Although, immune check-point inhibitors changed the course of many cancers, the outcomes in sarcomas were rather disappointing with less than 10% response rates. Ewing sarcoma is a poorly differentiated and aggressive tumor mostly seen in the children and adolescents. It's a distinct type of sarcoma with prominent chemosensitivity in the early stages. However, the relapsing disease has a poor prognosis with limited treatment options. Herein, we represent a case of relapsed Ewing sarcoma treated with multiple lines of chemotherapy.Management & outcome: The patient had a very good response to salvage treatment with a combination of paclitaxel and nivolumab which lasted for twelve months after the cessation of treatment. We think that chemotherapy plus immunotherapy can be an option for Ewing sarcoma patients treated with multiple lines of chemotherapy.

Outcomes of Adult Ewing Sarcoma Treated with Multimodality Therapy: A Single-Institute Experience

Introduction Ewing sarcoma (ES) is more common in children and relatively rare in adults. Adult ES has poor prognosis than children. Treatment approaches for adults have been extrapolated from pediatric experience. Data on adult ES are very few because of its rarity in adults. The present study was done to analyze the clinical profile and outcome of adult ES. Aims The aim was to study the clinical and pathological treatment and outcomes in adult ES. Subjects and Methods Between 2010 and 2017, a total of 73 ES patients with age more than 18 years were retrospectively analyzed. Survival analysis was done by plotting Kaplan–Meier curves. Results A total of 73 patients were diagnosed with ES during 2010 to 2017. Among them, 43 (58.9%) had localized disease with a median age of 24.5 years. Males were 44 (60.3%) and females were 29 (39.7). Pain (75.3%) was the most common symptom at presentation. Nine patients had incomplete details and were excluded from the analysis. Among 21 (28.8%) patients, the lung (61.9%) was the most common site of metastasis followed by the bone, bone marrow, and brain. The median number of chemotherapy cycles in the localized disease was 14 (range 1–17), and in metastatic disease, it was 4 (range 1–7). Univariate analysis was done with respect to age (< 25 vs. ≥25), gender, elevated or normal serum lactate dehydrogenase level, tumor size (< 8 cm versus ≥8 cm), site (axial versus extremity), and neoadjuvant chemotherapy (NACT) given or not. NACT had a significant impact on overall survival (OS) and the rest had no effect. At a median follow-up of 40 months, the 3-year OS in localized disease was 87.4%. In metastatic disease, the median OS was 13 months with 3-year OS of 26%. Conclusions Outcomes with multimodality therapy in adult ES patients with localized disease are comparable to that of a pediatric cohort. However, metastatic disease has poor survival.

Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) with OT-82 induces DNA damage, cell death, and suppression of tumor growth in preclinical models of Ewing sarcoma

NAMPT mediates the rate-limiting step of the NAD salvage pathway, which maintains cellular bioenergetics and provides a necessary substrate for functions essential to rapidly proliferating cancer cells. In this study, we evaluated the efficacy and mechanisms of action of OT-82, a novel, high-potency NAMPT inhibitor with a favorable toxicity profile, in preclinical models of Ewing sarcoma (EWS), an aggressive pediatric malignancy with previously reported selective sensitivity to NAMPT inhibition. We show that OT-82 decreased NAD concentration and impaired proliferation of EWS cells in a dose-dependent manner, with IC50 values in the single-digit nanomolar range. Notably, genetic depletion of NAMPT phenocopied pharmacological inhibition. On-target activity of OT-82 was confirmed with the addition of NMN, the product of NAMPT, which rescued NAD concentration and EWS cellular viability. Mechanistically, OT-82 treatment resulted in impaired DNA damage repair through loss of PARP activity, G2 cell-cycle arrest, and apoptosis in EWS cells. Additional consequences of OT-82 treatment included reduction of glycolytic and mitochondrial activity. In vivo, OT-82 impaired tumor growth and prolonged survival in mice bearing EWS xenografts. Importantly, antitumor effect correlated with pharmacodynamic markers of target engagement. Furthermore, combining low-dose OT-82 with low doses of agents augmenting DNA damage demonstrated enhanced antitumor activity in vitro and in vivo. Thus, OT-82 treatment represents a potential novel targeted approach for the clinical treatment of EWS.

Abstract 1717: Targeted NanoSpheres (TNS): An effective, non-toxic nano-formulated therapeutic platform for broad use in cancer treatment

Abstract Current cancer therapy relies on the use of cytotoxic agents (‘chemotherapy') that was developed over 50 years ago. These agents are very effective, but efficacy is limited by off-target toxicity to normal tissues. It is widely recognized that chemotherapy could be far more effective if higher doses could be delivered to the tumor and not to normal tissues. By refining the early formulations and after extensive testing, we developed a novel targeted nanoparticle called Targeted NanoSpheres or TNS. We showed this novel nano-formulated platform can overcome many deficiencies of conventional nanoparticles and therefore has enhanced potential as an effective delivery vehicle for virtually any type of cancer for which a suitable tumor cell surface antigen is present. We are exploring the development of NV103, a first-in-class anti-CD99 TNS (CD99-TNS/Ir), for the treatment of Ewing Sarcoma (EWS), a highly lethal pediatric and young adult bone and soft tissue tumor driven by a fusion protein, typically EWS/FLI1 in over 85% of cases. This platform is also being investigated for other types of cancer that either express CD99, or other tumor antigens like GD2 and B7-H3. In addition, a variety of payloads, including small molecules chemotherapeutics like irinotecan and doxorubicin, as well as plasmids, siRNA, ASOs, and mRNA, have been successfully incorporated and effectively delivered with documented superior anti-tumor effect. NV103 itself showed significant anti-tumor effect in hepatocellular carcinoma and prostate tumor cell lines and xenografts. In all cases, systemic toxicity is minimized by use of targeting antibodies that enhance tumor delivery while minimizing systemic exposure of normal tissues. Citation Format: Hyunggyoo Kang, Jon Nagy, Timothy Triche. Targeted NanoSpheres (TNS): An effective, non-toxic nano-formulated therapeutic platform for broad use in cancer treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1717.

Abstract 3411: High-throughput drug screening combined with a druggable target CRISPR drop-out screen identifies therapeutic vulnerabilities of BCOR-CCNB3 fusion positive sarcomas

Abstract Undifferentiated round cell sarcomas, which carry the BCOR-CCNB3 fusion gene, have traditionally been called “Ewing-like sarcomas” and have been treated with Ewing sarcoma treatment regimens. While there has been emerging evidence that these BCOR-CCNB3 sarcomas (BCS) are molecularly distinct from Ewing sarcomas, the biology of these tumors is poorly understood, and patients have few options when they do not respond to Ewing sarcoma-based therapies. Here, we report the establishment of a novel BCS cell line, which we utilized to identify a unique BCS-specific therapeutic vulnerability using a hybrid screening approach consisting of a high-throughput drug screen combined with a CRISPR/Cas9-based knock out genetic screen. The BCOR-CCNB3-positive sarcoma cell line NBC-1 was established from the tumor tissue obtained from an 18-year-old male with a soft tissue tumor of the buttock with lymph node metastasis, and the expression of the fusion BCOR-CCNB3 transcript was confirmed by RT-PCR. An in vitro high-throughput screening was performed using the L1300 library of 2570 drugs, where the cells were incubated for 48 hours with drug before cell viability was measured. This drug screen identified 148 drugs, which included 84 FDA-approved drugs. While these drugs predictably included a significant number of conventional cytotoxic chemotherapy drugs currently used to treat BCS, such as vincristine and doxorubicin, several other drug classes emerged, identifying twenty tyrosine kinase inhibitors, proteasome inhibitors such as Carfizomib, Ixazomib, and Bortezomib, and a histone deacetylase inhibitor, Panobinostat, all of which had distinctly higher cytotoxicity compared to the Ewing sarcoma cell controls. Next, we utilized a custom-made CRISPR panel consisting of 9771 sgRNAs targeting 1221 genes where we were able to identify a specific pharmacologic inhibitor in the literature. Using this library, we carried out a genetic loss-of-function screen to identify genes that are required for the proliferation of BCS. Based on these initial findings, we were able to demonstrate that BCS tumors have distinct vulnerabilities from Ewing sarcoma, suggesting that a BCS-specific therapeutic approach is necessary. Citation Format: Naoki Oike, Hiroyuki Kawashima, Akira Ogose, Takashi Ariizumi, Yudai Murayama, Hajime Umezu, Molishree Joshi, Colin Sempeck, Deandra Warker, Avery Bodlak, Naoto Endo, Masanori Hayashi. High-throughput drug screening combined with a druggable target CRISPR drop-out screen identifies therapeutic vulnerabilities of BCOR-CCNB3 fusion positive sarcomas [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3411.

Outcomes with nondose-dense chemotherapy for Ewing sarcoma: A practical approach for the developing world.

The current multidisciplinary approach in the treatment of Ewing sarcoma has improved cure rates, with contemporary dose-dense chemotherapy attaining 5-year event-free survival (EFS) of 73% in localized cases. Dose-intense and dose-dense chemotherapy is difficult in the majority of resource-limited settings with limited access to optimal supportive care. We report on patients with Ewing sarcoma treated on EFT-2001, a nondose-dense chemotherapy protocol. A retrospective analysis was conducted of patients (<15years) with Ewing sarcoma treated with curative intent during January 2013-June 2017 with an institutional ethics committee-approved nondose-dense protocol (EFT-2001). Local therapy was planned after 9-12weeks of chemotherapy with metastatic sites addressed with radiotherapy. The study assessed outcomes and prognostic factors. We analysed 200 patients with M:F ratio of 1.27:1 and metastases in 41 patients (20.5%). At a median follow up of 41.5months (range 4.5-81.8months), respective 3-year EFS and overall survival (OS) of the whole cohort is 65.3% (95% confidence interval [CI]: 58.1-71.7%) and 79.3% (95% CI: 72.8-84.5%); for localized and metastatic cohort, 70.9% (95% CI: 62.9-77.5%) and 82.8% (95% CI: 75.7-89.0%); and for metastatic cohort, 42.8% (95% CI: 28.0-58.6%) and 65.3% (95% CI: 47.7-78.3%). Presence of residual disease (morphologic/metabolic) on positron emission tomography-computed tomography scan done 3months post definitive radiotherapy (hazard ratio [HR] 7.92 [95% CI: 3.46-18.14]) and delay in any form of local control >4months (HR 3.42 [95% CI: 1.32-8.89]) affected outcomes. Nonrelapse mortality during treatment was 6.5%, mainly due to cardiomyopathy (3.0%) and bacterial sepsis (1.5%). Cardiotoxicity was seen in 11.5% of patients. Nondose-dense chemotherapy provides good outcomes with manageable toxicities in a multidisciplinary treatment approach, while reducing cumulative drug exposures in the developing world where dose-intense or dose-dense chemotherapy could potentially increase toxicity, and hence seems a feasible approach in resource-limited settings. Presence of any residual disease post definitive radiotherapy or delay in local control portends poor outcome.

Protein phosphatase 1 regulatory subunit 1A regulates cell cycle progression in Ewing sarcoma.

Ewing sarcoma (ES) is a malignant pediatric bone and soft tissue tumor. Patients with metastatic ES have a dismal outcome which has not been improved in decades. The major challenge in the treatment of metastatic ES is the lack of specific targets and rational combinatorial therapy. We recently found that protein phosphatase 1 regulatory subunit 1A (PPP1R1A) is specifically highly expressed in ES and promotes tumor growth and metastasis in ES. In the current investigation, we show that PPP1R1A regulates ES cell cycle progression in G1/S phase by down-regulating cell cycle inhibitors p21Cip1 and p27Kip1, which leads to retinoblastoma (Rb) protein hyperphosphorylation. In addition, we show that PPP1R1A promotes normal transcription of histone genes during cell cycle progression. Importantly, we demonstrate a synergistic/additive effect of the combinatorial therapy of PPP1R1A and insulin-like growth factor 1 receptor (IGF-1R) inhibition on decreasing ES cell proliferation and migration in vitro and limiting xenograft tumor growth and metastasis in vivo. Taken together, our findings suggest a role of PPP1R1A as an ES specific cell cycle modulator and that simultaneous targeting of PPP1R1A and IGF-1R pathways is a promising specific and effective strategy to treat both primary and metastatic ES.

Breakthrough Technologies Reshape the Ewing Sarcoma Molecular Landscape.

Ewing sarcoma is a highly aggressive round cell mesenchymal neoplasm, most often occurring in children and young adults. At the molecular level, it is characterized by the presence of recurrent chromosomal translocations. In the last years, next-generation technologies have contributed to a more accurate diagnosis and a refined classification. Moreover, the application of these novel technologies has highlighted the relevance of intertumoral and intratumoral molecular heterogeneity and secondary genetic alterations. Furthermore, they have shown evidence that genomic features can change as the tumor disseminates and are influenced by treatment as well. Similarly, next-generation technologies applied to liquid biopsies will significantly impact patient management by allowing the early detection of relapse and monitoring response to treatment. Finally, the use of these novel technologies has provided data of great value in order to discover new druggable pathways. Thus, this review provides concise updates on the latest progress of these breakthrough technologies, underscoring their importance in the generation of key knowledge, prognosis, and potential treatment of Ewing Sarcoma.

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.