Delayed Solid Tumor Presentations in Adolescent and Young Adults Patients in the Bronx

Adolescent and young adults (AYAs) require support from their parents and caregivers. While there are formal programs available for patients with complex medical problems, <20% of pediatric practices are performing transition readiness processes in patients aged 12-17 years to effective transition. Although cancer is the most common cause of disease-related death in AYAs in high-income countries, AYA oncology patients have not attained the same clinical improvements as pediatric patients, and their outcomes remain poorer. While there are published data on an expected degree of lag time for patients presenting with solid tumors, due to the underlying biology and slow growth of the cancer, we have recently witnessed extreme delays in the presentation to medical care. In this article, we share the cases of two young adults.

RNA helicase DDX3 regulates RAD51 localization and DNA damage repair in Ewing sarcoma

We previously demonstrated that RNA helicase DDX3X (DDX3) can be a therapeutic target in Ewing sarcoma (EWS), but its role in EWS biology remains unclear. The present work demonstrates that DDX3 plays a unique role in DNA damage repair (DDR). We show that DDX3 interacts with several proteins involved in homologous recombination, including RAD51, RECQL1, RPA32, and XRCC2. In particular, DDX3 colocalizes with RAD51 and RNA:DNA hybrid structures in the cytoplasm of EWS cells. Inhibition of DDX3 RNA helicase activity increases cytoplasmic RNA:DNA hybrids, sequestering RAD51 in the cytoplasm, which impairs nuclear translocation of RAD51 to sites of double-stranded DNA breaks, thus increasing sensitivity of EWS to radiation treatment, both in vitro and in vivo. This discovery lays the foundation for exploring new therapeutic approaches directed at manipulating DDR protein localization in solid tumors.

Drivers of Differential Time to Diagnosis in Pediatric ALL Tied to Race and Ethnicity

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy, with diagnosis preceded by symptoms that may include fever, weight loss, fatigue, bleeding, and bruising. Timely diagnosis and treatment of ALL may lead to improved outcomes and reduced morbidity from associated complications, including tumor lysis syndrome, hyperviscosity, and stroke. We performed a retrospective cohort analysis of 274 pediatric pre-B cell ALL and acute lymphoblastic lymphoma patients within Montefiore Health System to determine whether there were factors associated with time from symptom onset to diagnosis. The median time to diagnosis for all patients was 11.5 days (interquartile range: 7.8, 14.3). Those with Medicaid insurance (n=189) were diagnosed sooner than those with private/self-pay insurance (n=85) (median of 10 vs. 16 days; P =0.05). English and other language speakers experienced fewer median days from symptom onset to diagnosis date compared with Spanish speakers (11 vs. 7 vs. 14; P =0.05). Insurance status may impact the time to diagnosis to a greater degree in non-Hispanic patients, while the English language and female sex may represent a greater advantage to Hispanic patients. Insurance status and language preference may impact the time to diagnosis of pediatric ALL. There is a further need to confirm our findings and to study possible causes driving these disparities.

Respiratory Failure Due to Idiopathic Pneumonia Syndrome in a Pediatric Patient After Recipient-derived Allogeneic Chimeric Antigen Receptor T-Cell Therapy

Idiopathic pneumonia syndrome (IPS) is a life-threatening complication of hematopoietic cell transplantation, but it is not clearly described following chimeric antigen receptor (CAR) T-cell therapy. We describe a child who developed IPS after receiving tisagenlecleucel for post-hematopoietic cell transplantation relapsed acute lymphoblastic leukemia and had a remarkable improvement after treatment with corticosteroids and etanercept. We discuss the implications of cytokine signaling in IPS and immunologic considerations of allogeneic CAR T cells. We anticipate that the incidence of IPS and other allogeneic phenomena will be observed more often as allogeneic CAR T cells are employed in more varied settings with more mismatched donors.

RNA Helicase DDX3 Regulates RAD51 Localization and DNA Damage Repair in Ewing Sarcoma

We previously demonstrated that RNA helicase DDX3X (DDX3) can be a therapeutic target in Ewing sarcoma (EWS), but its role in EWS biology remains unclear. The present work demonstrates that DDX3 plays a unique role in DNA damage repair (DDR). We show that DDX3 interacts with several proteins involved in homologous recombination, including RAD51, RECQL1, RPA32, and XRCC2. In particular, DDX3 colocalizes with RAD51 and RNA:DNA hybrid structures in the cytoplasm of EWS cells. Inhibition of DDX3 RNA helicase activity increases cytoplasmic RNA:DNA hybrids, sequestering RAD51 in the cytoplasm, which impairs nuclear translocation of RAD51 to sites of double-stranded DNA breaks thus increasing sensitivity of EWS to radiation treatment, both in vitro and in vivo. This discovery lays the foundation for exploring new therapeutic approaches directed at manipulating DDR protein localization in solid tumors.

Acetophenone protection against cisplatin-induced end-organ damage

Cisplatin is a widely used and efficacious chemotherapeutic agent for treating solid tumors, yet it causes systemic end-organ damage that is often irreversible and detrimental to quality of life. This includes severe sensorineural hearing loss, hepatotoxicity, and renal injury. Based on the hard-soft acid-base theory, we recently developed two acetophenone-derived, enol-based compounds that directly interfere with the side effects of cisplatin. We investigated organ-specific and generalized toxicity in order to define dose-dependent responses in rodents injected with cisplatin with or without the protective compounds. All metrics that were used as indicators of toxicity showed retention of baseline or control measurements when animals were pre-treated with acetophenones prior to cisplatin administration, while animals injected with no protective compounds showed expected elevations in toxicity measurements or depressions in measurements of organ function. These data support the further investigation of novel acetophenone compounds for the prevention of cisplatin-induced end-organ toxicity.

Respiratory Failure in a Child With Pulmonary Metastatic Osteosarcoma and COVID-19

The novel coronavirus, SARS-CoV-2, causes much more severe disease in adults than in children. Although it is anticipated that immune compromised children and children with cancer may be at higher risk of developing severe or fatal COVID-19, there are no currently published reports of fatal disease in a child with cancer. Because of the discrepancy in disease severity between adult and pediatric patients, we report the case of an adolescent with pulmonary metastatic osteosarcoma who died of COVID-19 early in the course of the pandemic in New York City in the hope that heightening awareness that pulmonary metastatic disease may predispose to a more severe outcome will increase surveillance in this vulnerable population.

XPO1 inhibition with selinexor synergizes with proteasome inhibition in neuroblastoma by targeting nuclear export of IkB

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XPO1 is overabundant in high-risk neuroblastoma and correlates with poor survival.

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Neuroblastoma cells are sensitive to XPO1 inhibition with selinexor.

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Use of selinexor results in nuclear retention of IkB, diminishing NF-kB activity.

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Selinexor and bortezomib act synergistically through promotion of apoptosis.

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Synergy is mediated in part, through IkB regulation of NF-kB activity.

Across many cancer types in adults, upregulation of the nuclear-to-cytoplasmic transport protein Exportin-1 (XPO1) correlates with poor outcome and responsiveness to selinexor, an FDA-approved XPO1 inhibitor. Similar data are emerging in childhood cancers, for which selinexor is being evaluated in early phase clinical studies. Using proteomic profiling of primary tumor material from patients with high-risk neuroblastoma, as well as gene expression profiling from independent cohorts, we have demonstrated that XPO1 overexpression correlates with poor patient prognosis. Neuroblastoma cell lines are also sensitive to selinexor in the low nanomolar range. Based on these findings and knowledge that bortezomib, a proteasome inhibitor, blocks degradation of XPO1 cargo proteins, we hypothesized that combination treatment with selinexor and bortezomib would synergistically inhibit neuroblastoma cellular proliferation. We observed that selinexor promoted nuclear retention of IkB and that bortezomib augmented the ability of selinexor to induce cell-cycle arrest and cell death by apoptosis. This synergy was abrogated through siRNA knockdown of IkB. The synergistic effect of combining selinexor and bortezomib in vitro provides rationale for further investigation of this combination treatment for patients with high-risk neuroblastoma.

Circulating Plasma Tumor DNA Is Superior to Plasma Tumor RNA Detection in Ewing Sarcoma Patients: ptDNA and ptRNA in Ewing Sarcoma

The detection of tumor-specific nucleic acids from blood increasingly is being used as a method of liquid biopsy and minimal residual disease detection. However, achieving high sensitivity and high specificity remains a challenge. Here, we perform a direct comparison of two droplet digital PCR (ddPCR)-based detection methods, circulating plasma tumor RNA and circulating plasma tumor DNA (ptDNA), in blood samples from newly diagnosed Ewing sarcoma patients. First, we developed three specific ddPCR-based assays to detect EWS-FLI1 or EWS-ERG fusion transcripts, which naturally showed superior sensitivity to DNA detection on in vitro control samples. Next, we identified the patient-specific EWS-FLI1 or EWS-ERG breakpoint from five patient tumor samples and designed ddPCR-based, patient-specific ptDNA assays for each patient. These patient-specific assays show that although plasma tumor RNA can be detected in select newly diagnosed patients, positive results are low and statistically unreliable compared with ptDNA assays, which reproducibly detect robust positive results across most patients. Furthermore, the unique disease biology of Ewing sarcoma enabled us to show that most cell-free RNA is not tumor-derived, although cell-free-DNA burden is affected strongly by tumor-derived DNA burden. Here, we conclude that, even with optimized highly sensitive and specific assays, tumor DNA detection is superior to RNA detection in Ewing sarcoma patients.

A multicenter report on the safety and efficacy of plerixafor based stem cell mobilization in children with malignant disorders

BACKGROUND

Pleraxifor for peripheral blood stem cell (PBSC) mobilization in children with malignancies is often given following failure of standard mobilization (SM) rather than as a primary mobilizing agent.

STUDY DESIGN AND METHODS

In this retrospective multicenter study, we report the safety of plerixafor-based PBSC mobilization in children with malignancies and compare outcomes between patients who received plerixafor upfront with SM (Group A) with those who received plerixafor following failure of SM (Group B). In the latter pleraxifor was given either following a low peripheral blood (PB) CD34 (<20 cells/cu.mm) (Group B1) or as a second collection process due to an unsuccessful yield (CD34 + < 2 × 10⁶ /kg) (Group B2) following failed SM and first apheresis attempts.

RESULTS

The study cohort (n = 47) with a median age of 8 (range 0.6-21) year, comprised 19 (40%) Group A and 28 (60%) Group B patients (B1 = 12 and B2 = 16). Pleraxifor mobilization was successful in 87.2% of patients, similar between Groups A and B (84.2% vs 89.2%) and resulted in a median 4-fold increase in PB CD34. Median number of apheresis attempts was 2 in Groups A and B1 but 4 in Group B2. In Group B2, median total CD34+ yield post-plerixafor was 9-fold higher than after SM (P = .0013). Mild to moderate transient adverse events affected 8.5% of patients. Among patients who proceeded to autologous transplant (n = 39), all but one engrafted.

CONCLUSION

Plerixafor-based PBSC collection was safe and effective in our cohort and supports consideration as a primary mobilizing agent in children with malignancies.

Wnt Signaling in Osteosarcoma

Wnt molecules are a class of cysteine-rich secreted glycoproteins that participate in various developmental events during embryogenesis and adult tissue homeostasis. Since its discovery in 1982, the roles of Wnt signaling have been established in various key regulatory systems in biology. Wnt signals exert pleiotropic effects, including mitogenic stimulation, cell fate specification, and differentiation. The Wnt signaling pathway in humans has been shown to be involved in a wide variety of disorders including colon cancer, sarcoma, coronary artery disease, tetra-amelia, Mullerian duct regression, eye vascular defects, and abnormal bone mass. The canonical Wnt pathway functions by regulating the function of the transcriptional coactivator β-catenin, whereas noncanonical pathways function independent of β-catenin. Although the role of Wnt signaling is well established in epithelial malignancies, its role in mesenchymal tumors is more controversial. Some studies have suggested that Wnt signaling plays a pro-oncogenic role in various sarcomas by driving cell proliferation and motility; however, others have reported that Wnt signaling acts as a tumor suppressor by committing tumor cells to differentiate into a mature lineage. Wnt signaling pathway also plays an important role in regulating cancer stem cell function. In this review, we will discuss Wnt signaling pathway and its role in osteosarcoma.

Skp2 depletion reduces tumor-initiating properties and promotes apoptosis in synovial sarcoma

Synovial sarcoma (SS) is an aggressive soft-tissue cancer with a poor prognosis and a propensity for local recurrence and distant metastasis. In this study, we investigated whether S phase kinase-associated protein (Skp2) plays an oncogenic role in tumor initiation, progression, and metastasis of SS. Our study revealed that Skp2 is frequently overexpressed in SS specimens and SS18-SSX transgenic mouse tumors, as well as correlated with clinical stages. Next, we identified that genetic depletion of Skp2 reduced mesenchymal and stemness markers, and inhibited the invasive and proliferative capacities of SS cell lines. Furthermore, Skp2 depletion markedly suppressed the growth of SS xenografts tumors. Treatment of SS cell lines with the skp2 inhibitor flavokawain A (FKA) reduced Skp2 expression in a dose-dependent manner and resulted in cell cycle arrest and apoptosis. FKA also suppressed the invasion and tumor-initiating properties in SS, similar to the effects of Skp2 knockdown. In addition, a combination of FKA and conventional chemotherapy showed a synergistic therapeutic efficacy. Taken together, our results suggest that Skp2 plays an essential role in the biology of SS by promoting the mesenchymal state and cancer stemness. Given that chemotherapy resistance is often associated with cancer stemness, strategies of combining Skp2 inhibitors with conventional chemotherapy in SS may be desirable.

Abstract 5930: Targeting Skp2 in synovial sarcoma reduces tumor-initiating properties and promotes apoptosis

Background. Despite the knowledge that most synovial sarcoma (SS) is driven by the fusion oncoprotein SS18-SSX, efforts in generating therapeutic agents that target the fusion oncoproteins have not been successful. The oncogenic role of S phase kinase-associated protein (Skp2) has been demonstrated in several cancers. However, the functional involvement of this F-box protein in SS is not well understood. Our goals are to examine the oncogenic role of Skp2 in SS and assess the therapeutic potential of inhibiting Skp2. Methods. The expression of Skp2 in established cell lines, patient specimens, SS18-SSX transgenic mouse tumors was assessed using RT-PCR, western blot, and immunochemistry. Genetic depletion of Skp2 was achieved by lentiviral shRNA. Further proliferation assay, sphere formation assay, invasion assay, and ALDH assay were performed along with western blot. The efficacy of flavokawain A (FKA), an skp2 inhibitor was also analyzed correspondingly. A mouse xenograft model was used to validate in vitro results. Results. Skp2 is frequently overexpressed in established cell lines, clinical specimens, and SS18-SSX transgenic mouse tumors. High levels of Skp2 correlated with more advanced clinical stages in SS. Next, we showed that genetic depletion of Skp2 reduced mesenchymal and stemness markers and inhibited the invasive and proliferative capacities of SS cell lines, as well as increased apoptotic markers and p27. Furthermore, Skp2 depletion markedly suppressed the growth of SS xenografts tumors, which indicates that Skp2 is essential in maintaining SS tumorigenesis. Treatment of SS cell lines with FKA reduced Skp2 expression in a dose-dependent manner and resulted in G2/M phase cell cycle arrest and apoptosis. In addition, FKA also suppressed the invasion and tumor-initiating properties in SS, similar to the effects of Skp2 knockdown.Conclusions. Taken together, our results suggest that Skp2 plays an essential role in the biology of SS by promoting the mesenchymal state and cancer stemness. Given that chemoresistance is often associated with cancer stemness, strategies of combining Skp2 inhibitors with conventional chemotherapy in SS may be desirable.

Citation Format: Jichuan Wang, Kenji Sato, Ed O'Donnell, Amit Singla, Simon Yaguare, Osama Aldahamsheh, Brian Batko, Hasibagan Borjihan, Janet Tingling, Daniel A Weiser, David M Loeb, Richard Gorlick, Edward L Schwartz, Rui Yang, Xiaolin Zi, Hongling Zhao, David S Geller, Bang H Hoang. Targeting Skp2 in synovial sarcoma reduces tumor-initiating properties and promotes apoptosis [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 5930.

Phase II trial of gemcitabine and nab-paclitaxel in patients with recurrent Ewing sarcoma: A report from the National Pediatric Cancer Foundation

BACKGROUND

The combination of gemcitabine and docetaxel is often used to treat patients with recurrent sarcoma. Nab-paclitaxel is a taxane modified to improve drug exposure and increase intratumoral accumulation and, in combination with gemcitabine, is standard therapy for pancreatic cancer. Applying the dosages and schedule used for pancreatic cancer, we performed a phase II trial to assess the response rate of gemcitabine and nab-paclitaxel in patients with relapsed Ewing sarcoma.

PROCEDURE

Using a Simon's two-stage design to identify a response rate of ≥ 35%, patients received nab-paclitaxel 125 mg/m² followed by gemcitabine 1000 mg/m² i.v. on days 1, 8, and 15 of four-week cycles. Immunohistochemical analysis of archival tissue was performed to identify possible biomarkers of response.

RESULTS

Eleven patients from four institutions enrolled, with a median age of 22 years (range, 14-27). Patients were heavily pretreated (median 3 prior regimens, range, 1-7). Thirty-five cycles were administered (median 2, range, 1-8). Accrual was stopped after 11 patients, due to only one confirmed partial response. Two other patients had partial responses after two cycles, but withdrew because of adverse effects or progression before confirmation of continued response. The predominant toxicity was myelosuppression, and four (36%) patients were removed due to hematologic toxicity despite pegfilgrastim and dose reductions. Expression of secreted protein, acidic and rich in cysteine (SPARC) and CAV-1 in archival tumors was not predictive of clinical benefit in this small cohort of patients.

CONCLUSIONS

In patients with heavily pretreated Ewing sarcoma, the confirmed response rate of 9% was similar to multi-institutional studies of gemcitabine and docetaxel.

A clinically and genomically annotated nerve sheath tumor biospecimen repository

Nerve sheath tumors occur as a heterogeneous group of neoplasms in patients with neurofibromatosis type 1 (NF1). The malignant form represents the most common cause of death in people with NF1, and even when benign, these tumors can result in significant disfigurement, neurologic dysfunction, and a range of profound symptoms. Lack of human tissue across the peripheral nerve tumors common in NF1 has been a major limitation in the development of new therapies. To address this unmet need, we have created an annotated collection of patient tumor samples, patient-derived cell lines, and patient-derived xenografts, and carried out high-throughput genomic and transcriptomic characterization to serve as a resource for further biologic and preclinical therapeutic studies. In this work, we release genomic and transcriptomic datasets comprised of 55 tumor samples derived from 23 individuals, complete with clinical annotation. All data are publicly available through the NF Data Portal and at http://synapse.org/jhubiobank.

Measurement(s)	gene expression • gene_variant
Technology Type(s)	RNA sequencing • exome sequencing • DNA sequencing
Factor Type(s)	tumor type
Sample Characteristic - Organism	Homo sapiens • Homo sapiens/Mus musculus xenograft

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12037599

Circulating stromal cells as a potential blood-based biomarker for screening invasive solid tumors

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Background: Peripheral blood allows for a simple non-invasive method for isolating various cancer associated circulating stromal cells (CStCs) which may predict for cancer presence. Cancer Associated Macrophage-Like cells (CAMLs), a specific CStC, are phagocytic myeloid cells that derive from an immunological response to cancer and emanate from primary tumors. Using a filtration platform we screened the peripheral blood of untreated newly diagnosed cancer patients (n = 308) for CAMLs. In parallel, we screened patients with newly diagnosed non-malignant diseases, i.e. lupus, benign cysts, etc. (n = 39), and healthy control samples (n = 76). We found that CAMLs are highly prevalent (87%) in the blood of cancer patients, but uncommon in non-malignant conditions (20%) & absent in healthy individuals (0%). Methods: Anonymized peripheral blood were taken from 308 cancer patients after confirmation of invasive malignancy [stage I (n = 76), stage II (n = 73), stage III (n = 72), stage IV (n = 65) and unstaged non-metastatic (n = 22)] with pathologically confirmed lung (n = 65), pancreas (n = 53), breast (n = 52), prostate (n = 40), esophageal (n = 30), renal cell (n = 18), hepatocellular (n = 15), neuroblastoma (n = 10), melanoma (n = 8), and other (n = 17). Further, anonymized blood was taken from patients with untreated non-malignant conditions including benign breast masses (n = 19), lupus (n = 11), liver cirrhosis (n = 5), benign prostatic hyperplasia (BPH) (n = 3), and viral infection (n = 1); or from healthy control volunteers (n = 76). CAMLs were isolated from whole peripheral blood by the CellSieve™ microfiltration technique and defined as enlarged, multinuclear cells with cytokeratin and/or CD45/CD14 positive. Results: CAMLs were found in 87% of all cancer patients regardless of stage, ~5.4 CAMLs/7.5mL blood. Specifically, CAMLs were found in 80% of Stage I, 90% Stage II, 89% Stage III, and 97% Stage IV patients. No CAMLs were found in any healthy controls, but were found in 26% of benign breast masses, 18% of lupus, 0% of BPH and 0% of cirrhosis. In total, CAML sensitivity in cancer vs healthy was 87% (CI95% 82-90%), specificity = 100% (CI95% 95-100%), PPV = 100% (CI95% 100%), NPV = 67% (CI95% 58-71%). CAML sensitivity in cancer vs benign was 87% (CI95% 82-90%), specificity = 80% (CI95% 64-91%), PPV = 97% (CI95% 95-98%), NPV = 43% (CI95% 35-51%). Conclusions: CAMLs, a Circulating Stromal Cell subtype, is a sensitive blood based biomarker found in all stages of cancer that is rare in non-malignant conditions and absent in healthy individuals.

An evolutionary framework for treating pediatric sarcomas

Lessons from extinction can be used in trials designed to pursue a cure for cancer. When cancer cannot be cured, similar strategies may be unwise, and strategies that leverage the adaptations of cancer to therapy should be considered.

Enolate-forming compounds provide protection from platinum neurotoxicity

Cisplatin (CisPt) and other platinum (Pt)-based antineoplastic drugs (e.g., carboplatin, oxaliplatin) are highly effective and widely used in the treatment of solid tumors in both pediatric and adult patients. Although considered to be life-saving as a cancer treatment, Pt-based drugs frequently result in dose-limiting toxicities such as chemotherapy-induced peripheral neuropathies (CIPN). Specifically, irreversible damage to outer hair cells and injury of sensory neurons are linked to profound sensorineural hearing loss (ototoxicity), which complicates tumor management and can lead to a poor clinical prognosis. Given the severity of CIPN, substantial effort has been devoted to the development of neuroprotective compounds, regardless clinical results have been underwhelming. It is noteworthy that Pt is a highly reactive electrophile (electron deficient) that causes toxicity by forming adducts with nucleophilic (electron rich) targets on macromolecules. In this regard, we have discovered a series of carbon-based enol nucleophiles; e.g., N-(4-acetyl-3,5-dihydroxyphenyl)-2-oxocytclopentane-1-carboxamide (Gavinol), that can prevent neurotoxicity by scavenging the platinum ion. The chemistry of enol compounds is well understood and mechanistic research has demonstrated the role of this chemistry in cytoprotection. Our cell-derived data were corroborated by calculations of hard and soft, acids and bases (HSAB) parameters that describe the electronic character of interacting electrophiles and nucleophiles. Together, these observations indicate that the respective mechanisms of Pt neurotoxicity and antitumor activity are separable and can therefore be affected independently.

Association of Dasatinib With Progression-Free Survival Among Patients With Advanced Gastrointestinal Stromal Tumors Resistant to Imatinib

Importance

Gastrointestinal stromal tumors (GISTs) are life-threatening when metastatic or not amenable to surgical removal. In a few patients with advanced GISTs refractory to imatinib mesylate, treatment with sunitinib malate followed by regorafenib provides tumor control; however, additional active treatments are needed for most patients.

Objective

To evaluate the 6-month progression-free survival (PFS), tumor objective response, and overall survival rates in patients with GISTs treated with dasatinib.

Design, Setting, and Participants

This single-arm clinical trial used a Bayesian design to enroll patients 13 years or older with measurable imatinib-refractory metastatic GISTs treated at 14 sarcoma referral centers from June 1, 2008, through December 31, 2009. A control group was not included. Patients were followed up for survival for a minimum of 5 years from date of enrollment. Tumor imaging using computed tomography or magnetic resonance imaging was performed every 8 weeks for the first 24 weeks and every 12 weeks thereafter. Tumor response was assessed by local site using the Choi criteria. Treatment was continued until tumor progression, unacceptable toxic effects after reduction in drug dose, or patient or physician decision. Archival tumor tissue was evaluated for expression of the proto-oncogene tyrosine-protein kinase Src (SRC), phosphorylated SRC (pSRC), and succinate dehydrogenase complex iron sulfur subunit B (SDHB) proteins and for mutation in the V-Kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT) and platelet-derived growth factor receptor α (PDGFRA) genes. Data analysis was performed from May 19, 2017, through December 20, 2017.

Interventions

Dasatinib, 70 mg orally twice daily.

Main Outcomes and Measures

The primary end point was the 6-month PFS estimate using greater than 30% as evidence of an active drug and less than 10% as evidence of inactive treatment.

Results

In this study, 50 patients were enrolled (median age, 60 years; age range, 19-78 years; 31 [62%] male and 19 [38%] female; 41 [82%] white), and 48 were evaluable for response. The estimated 6-month PFS rate was 29% in the overall population and 50% in a subset of 14 patients with pSRC in GISTs. Objective tumor response was observed in 25%, including 1 patient with an imatinib-resistant mutation in PDGFRA exon 18.

Conclusions and Relevance

Dasatinib may have activity in a subset of patients with imatinib-resistant GISTs. Further study is needed to determine whether pSRC is a prognostic biomarker.

Abstract CT109: A Phase I dose escalation and expansion study of seclidemstat (SP-2577) a first-in class reversible LSD1 inhibitor for patients with relapsed or refractory Ewing sarcoma

Introduction: Ewing sarcoma is an aggressive pediatric and young adult bone tumor dependent almost exclusively on the EWS/ETS fusion protein family for transcriptional activity. EWS/FLI is the most common fusion resulting in the repression of vital tumor suppressor genes by the activity of lysine-specific histone demethylase 1 (LSD1). Seclidemstat (SP-2577) is a first in class, orally bioavailable, small molecule with reversible and noncompetitive selective inhibition of LSD1 at low nanomolar concentrations (IC50: 25-50 nM). Seclidemstat has demonstrated disruption of global transcriptional function of EWS/ETS fusions and impairs multiple EWS/ETS-associated oncogenic phenotypes in xenograft models of Ewing sarcoma. This Phase I study aims primarily to assess the safety and tolerability of seclidemstat and to secondarily characterize the pharmacokinetics (PK), food effects, and preliminary anti-tumor activity via RECIST 1.1. Exploratory objectives include using circulating tumor cells, cell-free DNA, and hemoglobin F as pharmacodynamic markers of response.

Methods: This multi-center phase I study (NCT03600649) is open-label and non-randomized and utilizes an accelerated dose escalation phase followed by a conventional 3+3 design to determine the maximum tolerated dose (MTD). Initially, one subject per dose cohort will be recruited in the accelerated dose escalation phase until the first instance of grade 2 or greater drug related toxicity or dose limiting toxicity (DLT). Further cohorts will be recruited in cohorts of three subjects in the 3+3 dose escalation phase. Once a declared suitable dose and schedule for further investigation has been identified, 14 additional patients will be enrolled in the dose expansion part of the study for a total of 20 patients treated at the MTD. The starting dose of seclidemstat is 75 mg PO BID with seven dose levels planned by modified Fibonacci schema. Food effects on PK are planned on day 1 and 2 of cycles 1 and 2. Patients at least 12 years of age will be included with histologically confirmed relapsed or refractory Ewing sarcoma with adequate performance status and organ function. Archival tumor tissue is required during screening. Tumor biopsies and measurable disease are required in dose expansion only. This trial is currently open for requirement at five locations in the United States. Dose level 2 (150 mg PO BID) began enrollment in November 2018 with no drug related grade 2 or greater adverse events or DLTs observed in dose level 1.

Citation Format: Damon Reed, Steven G. DuBois, Richard Gorlick, Leo Mascarenhas, Douglas Harrison, Jonathan Metts, Stephen L. Lessnick, Brian D. Crompton, David M. Loeb, Rose Hernandez, Jeff Larson, David D. Stenehjem. A Phase I dose escalation and expansion study of seclidemstat (SP-2577) a first-in class reversible LSD1 inhibitor for patients with relapsed or refractory Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT109.

Three-dimensional in vitro modeling of malignant bone disease recapitulates experimentally accessible mechanisms of osteoinhibition

Malignant bone disease (MBD) occurs when tumors establish in bone, causing catastrophic tissue damage as a result of accelerated bone destruction and inhibition of repair. The resultant so-called osteolytic lesions (OL) take the form of tumor-filled cavities in bone that cause pain, fractures, and associated morbidity. Furthermore, the OL microenvironment can support survival of tumor cells and resistance to chemotherapy. Therefore, a deeper understanding of OL formation and MBD progression is imperative for the development of future therapeutic strategies. Herein, we describe a novel in vitro platform to study bone-tumor interactions based on three-dimensional co-culture of osteogenically enhanced human mesenchymal stem cells (OEhMSCs) in a rotating wall vessel bioreactor (RWV) while attached to micro-carrier beads coated with extracellular matrix (ECM) composed of factors found in anabolic bone tissue. Osteoinhibition was recapitulated in this model by co-culturing the OEhMSCs with a bone-tumor cell line (MOSJ-Dkk1) that secretes the canonical Wnt (cWnt) inhibitor Dkk-1, a tumor-borne osteoinhibitory factor widely associated with several forms of MBD, or intact tumor fragments from Dkk-1 positive patient-derived xenografts (PDX). Using the model, we observed that depending on the conditions of growth, tumor cells can biochemically inhibit osteogenesis by disrupting cWnt activity in OEhMSCs, while simultaneously co-engrafting with OEhMSCs, displacing them from the niche, perturbing their activity, and promoting cell death. In the absence of detectable co-engraftment with OEhMSCs, Dkk-1 positive PDX fragments had the capacity to enhance OEhMSC proliferation while inhibiting their osteogenic differentiation. The model described has the capacity to provide new and quantifiable insights into the multiple pathological mechanisms of MBD that are not readily measured using monolayer culture or animal models.

A phase II study of temsirolimus and liposomal doxorubicin for patients with recurrent and refractory bone and soft tissue sarcomas

Background

Relapsed and refractory sarcomas continue to have poor survival rates. The cancer stem cell (CSC) theory provides a tractable explanation for the observation that recurrences occur despite dramatic responses to upfront chemotherapy. Preclinical studies demonstrated that inhibition of the mechanistic target of rapamycin (mTOR) sensitizes the CSC population to chemotherapy.

Methods

Here we present the results of the Phase II portion of a Phase I/II clinical trial that aimed to overcome the chemoresistance of sarcoma CSC by combining the mTOR inhibitor temsirolimus (20 mg/m² weekly) with the chemotherapeutic agent liposomal doxorubicin (30 mg/m² monthly).

Results

Fifteen patients with relapsed/refractory sarcoma were evaluable at this recommended Phase 2 dose level. The median progression free survival was 315 days (range 27–799). Response rate, defined as stable disease or better for 60 days, was 53%. Nine of the patients had been previously treated with doxorubicin. Therapy was well tolerated. In a small number of patients, pre- and post- treatment tumor biopsies were available for assessment of ALDH expression as a marker of CSCs and showed a correlation between response and decreased ALDH expression. We also found a correlation between biopsy-proven inhibition of mTOR and response.

Conclusions

Our study adds to the literature supporting the addition of mTOR inhibition to chemotherapy agents for the treatment of sarcomas, and proposes that a mechanism by which mTOR inhibition enhances the efficacy of chemotherapy may be through sensitizing the chemoresistant CSC population. Further study, ideally with pre- and post-therapy assessment of ALDH expression in tumor cells, is warranted.

Trial registration The trial was registered on clinicaltrials.gov (NCT00949325) on 30 July 2009. http://www.editorialmanager.com/csrj/default.aspx

Knock-in of the Wt1 R394W mutation causes MDS and cooperates with Flt3/ITD to drive aggressive myeloid neoplasms in mice

Wilms tumor 1 (WT1) is a zinc finger transcriptional regulator, and has been implicated as both a tumor suppressor and oncogene in various malignancies. Mutations in the DNA-binding domain of the WT1 gene are described in 10-15% of normal-karyotype AML (NK-AML) in pediatric and adult patients. Similar WT1 mutations have been reported in adult patients with myelodysplastic syndrome (MDS). WT1 mutations have been independently associated with treatment failure and poor prognosis in NK-AML. Internal tandem duplication (ITD) mutations of FMS-like tyrosine kinase 3 (FLT3) commonly co-occur with WT1-mutant AML, suggesting a cooperative role in leukemogenesis. The functional role of WT1 mutations in hematologic malignancies appears to be complex and is not yet fully elucidated. Here, we describe the hematologic phenotype of a knock-in mouse model of a Wt1 mutation (R394W), described in cases of human leukemia. We show that Wt1 ^+/R394W mice develop MDS which becomes 100% penetrant in a transplant model, exhibit an aberrant expansion of myeloid progenitor cells, and demonstrate enhanced self-renewal of hematopoietic progenitor cells in vitro. We crossbred Wt1 ^+/R394W mice with knock-in Flt3 ^+/ITD mice, and show that mice with both mutations (Flt3 ^+/ITD/Wt1 ^+/R394W) develop a transplantable MDS/MPN, with more aggressive features compared to either single mutant mouse model.

Outcomes of Measurable Residual Disease in Pediatric Acute Myeloid Leukemia before and after Hematopoietic Stem Cell Transplant: Validation of Difference from Normal Flow Cytometry with Chimerism Studies and Wilms Tumor 1 Gene Expression

We enrolled 150 patients in a prospective multicenter study of children with acute myeloid leukemia undergoing hematopoietic stem cell transplantation (HSCT) to compare the detection of measurable residual disease (MRD) by a "difference from normal" flow cytometry (ΔN) approach with assessment of Wilms tumor 1 (WT1) gene expression without access to the diagnostic specimen. Prospective analysis of the specimens using this approach showed that 23% of patients screened for HSCT had detectable residual disease by ΔN (.04% to 53%). Of those patients who proceeded to transplant as being in morphologic remission, 10 had detectable disease (.04% to 14%) by ΔN. The disease-free survival of this group was 10% (0 to 35%) compared with 55% (46% to 64%, P < .001) for those without disease. The ΔN assay was validated using the post-HSCT specimen by sorting abnormal or suspicious cells to confirm recipient or donor origin by chimerism studies. All 15 patients who had confirmation of tumor detection relapsed, whereas the 2 patients with suspicious phenotype cells lacking this confirmation did not. The phenotype of the relapse specimen was then used retrospectively to assess the pre-HSCT specimen, allowing identification of additional samples with low levels of MRD involvement that were previously undetected. Quantitative assessment of WT1 gene expression was not predictive of relapse or other outcomes in either pre- or post-transplant specimens. MRD detected by ΔN was highly specific, but did not identify most relapsing patients. The application of the assay was limited by poor quality among one-third of the specimens and lack of a diagnostic phenotype for comparison.

Consensus and controversies regarding the treatment of rhabdomyosarcoma

Optimal treatment of rhabdomyosarcoma (RMS) requires multidisciplinary approach, incorporating chemotherapy with local control. Although current therapies are built on cooperative group trials, a comprehensive standard of care to guide clinical decision making has been lacking, especially for relapsed patients. Therefore, we assembled a panel of pediatric and adolescent and young adult sarcoma experts to develop treatment guidelines for managing RMS and to identify areas in which further research is needed. We created algorithms incorporating evidence-based care for patients with RMS, emphasizing the importance of clinical trials and close integration of all specialties involved in the care of these patients.

A monoclonal antibody against the Wnt signaling inhibitor dickkopf-1 inhibits osteosarcoma metastasis in a preclinical model

The outcome of patients with metastatic osteosarcoma has not improved since the introduction of chemotherapy in the 1970s. Development of therapies targeting the metastatic cascade is a tremendous unmet medical need. The Wnt signaling pathway has been the focus of intense investigation in osteosarcoma because of its role in normal bone development. Although the role of Wnt signaling in the pathogenesis of osteosarcoma is controversial, there are several reports of dickkopf-1 (DKK-1), a Wnt signaling antagonist, possibly playing a pro-tumorigenic role. In this work we investigated the effect of anti-DKK-1 antibodies on the growth and metastasis of patient-derived osteosarcoma xenografts. We were able to detect human DKK-1 in the blood of tumor-bearing mice and found a correlation between DKK-1 level and tumor proliferation. Treatment with the anti-DKK-1 antibody, BHQ880, slowed the growth of orthotopically implanted patient-derived osteosarcoma xenografts and inhibited metastasis. This effect was correlated with increased nuclear beta-catenin staining and increased expression of the bone differentiation marker osteopontin. These findings suggest that Wnt signaling is anti-tumorigenic in osteosarcoma, and support the targeting of DKK-1 as an anti-metastatic strategy for patients with osteosarcoma.

Reduced-Intensity Haploidentical Bone Marrow Transplantation with Post-Transplant Cyclophosphamide for Solid Tumors in Pediatric and Young Adult Patients

High-risk, recurrent, or refractory solid tumors in pediatric, adolescent, and young adult (AYA) patients have an extremely poor prognosis despite current intensive treatment regimens. We piloted an allogeneic bone marrow transplant platform using reduced-intensity conditioning (RIC) and partially HLA-mismatched (haploidentical) related donors for this population of pediatric and AYA solid tumor patients. Sixteen patients received fludarabine, cyclophosphamide, melphalan, and low-dose total body irradiation RIC haploidentical BMT (haploBMT) followed by post-transplantation cyclophosphamide (PTCy), mycophenolate mofetil, and sirolimus. All assessable patients were full donor chimeras on day 30 with a median neutrophil recovery of 19 days and platelet recovery of 21 days. One patient (7%) exhibited secondary graft failure associated with concomitant infection. The median follow-up time was 15 months. Overall survival was 88%, 56%, and 21% at 6, 12, and 24 months, respectively. Median survival from transplant date was 14 months with a median progression-free survival 7 months. We observed limited graft-versus-host disease in 3 patients and nonrelapse mortality in 1 patient. We demonstrated that RIC haploBMT with PTCy is feasible and has acceptable toxicities in patients with incurable pediatric and AYA solid tumors; thus, this approach serves as a platform for post-transplant strategies to prevent relapse and optimize progression-free survival.

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

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

Inhibition of porcupine prolongs metastasis free survival in a mouse xenograft model of Ewing sarcoma

The most pressing unmet clinical need for patients with Ewing sarcoma (ES) is the prevention and treatment of metastasis. The Wnt signaling pathway regulates a number of cellular functions associated with metastasis, including proliferation, motility, and stem cell self-renewal. Functional interaction between Wnt ligands and their receptors requires palmitoylation by Porcupine (Porcn), making this an ideal therapeutic target. We studied the effect of WNT974, a potent, selective Porcn inhibitor, on ES metastasis. In vitro, WNT974 does not affect ES proliferation or sarcosphere formation, but suppresses multiple transcriptional regulators of metastasis and inhibits cell migration. In vivo, in an orthotopic implantation/amputation model of spontaneous distant metastasis, single agent WNT974 treatment leads to a significant delay in formation of lung metastasis and a substantial improvement in post-amputation survival without a major effect on primary tumor growth. The drug produces no survival benefit in a tail vein injection model, supporting the hypothesis that WNT974 inhibits early steps in the metastatic cascade, such as migration and invasion. Our findings strongly implicate Wnt signaling in the early steps of ES metastasis and demonstrate that WNT974 has the potential to significantly improve the survival of ES patients through the specific inhibition of metastasis.

A phase II trial evaluating the feasibility of adding bevacizumab to standard osteosarcoma therapy

Increased vascular endothelial growth factor (VEGF) expression in osteosarcoma correlates with a poor outcome. We conducted a phase II trial to evaluate the feasibility and efficacy of combining bevacizumab, a monoclonal antibody against VEGF, with methotrexate, doxorubicin and cisplatin (MAP) in patients with localized osteosarcoma. Eligible patients received two courses of MAP chemotherapy before definitive surgery at week 10. Bevacizumab (15 mg/kg) was administered 3 days before starting chemotherapy then on day 1 of weeks 3 and 5 of chemotherapy. After surgery, patients received MAP for a total of 29 weeks; bevacizumab was added every 2 or 3 weeks on day 1 of chemotherapy at least 5 weeks after surgery. Group sequential monitoring rules were used to monitor for unacceptable bevacizumab-related targeted toxicity (grade 4 hypertension, proteinuria or bleeding, grade 3 or 4 thrombosis/embolism, and grade 2-4 major wound complications). Thirty-one patients (median age 12.8 years) with localized osteosarcoma were enrolled. No unacceptable targeted toxicities were observed except for wound complications (9 minor and 6 major), which occurred in 15 patients; none required removal of prosthetic hardware or amputation. The estimated 4-year event-free survival (EFS) rate and overall survival rate were 57.5 ± 10.0% and 83.4 ± 7.8%, respectively. Eight (28%) of 29 evaluable patients had good histologic response (<5% viable tumor) to preoperative chemotherapy. The addition of bevacizumab to MAP for localized osteosarcoma is feasible but frequent wound complications are encountered. The observed histologic response and EFS do not support further evaluation of bevacizumab in osteosarcoma.

Personalized Medicine in the Oncology Clinic: Implementation and Outcomes of the Johns Hopkins Molecular Tumor Board

Purpose

Tumor genomic profiling for personalized oncology therapy is being widely applied in clinical practice even as it is being evaluated more formally in clinical trials. Given the complexities of genomic data and its application to clinical use, molecular tumor boards with diverse expertise can provide guidance to oncologists and patients seeking to implement personalized genetically targeted therapy in practice.

Methods

A multidisciplinary molecular tumor board reviewed tumor molecular profiling reports from consecutive referrals at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins over a 3-year period. The tumor board weighed evidence for actionability of genomic alterations identified by molecular profiling and provided recommendations including US Food and Drug Administration-approved drug therapy, clinical trials of matched targeted therapy, off-label use of such therapy, and additional tumor or germline genetic testing.

Results

One hundred fifty-five patients were reviewed. Actionable genomic alterations were identified in 132 patients (85%). Off-label therapies were recommended in 37 patients (24%). Eleven patients were treated off-label, and 13 patients were enrolled onto clinical trials of matched targeted therapies. Median progression-free survival of patients treated with matched therapies was 5 months (95% CI, 2.9 months to not reached), and the progression-free survival probability at 6 months was 43%(95% CI, 26% to 71%). Lack of locally available clinical trials was the major limitation on clinical actionability of tumor profiling reports.

Conclusion

The molecular tumor board recommended off-label targeted therapies for a quarter of all patients reviewed. Outcomes were heterogeneous, although 43% of patients receiving genomically matched therapy derived clinical benefit lasting at least 6 months. Until more data become available from precision oncology trials, molecular tumor boards can help guide appropriate use of tumor molecular testing to direct therapy.

Targeted therapy for soft tissue sarcomas in adolescents and young adults

Soft tissue sarcomas (STSs) are a heterogeneous group of tumors originating from the mesenchyme. Even though they affect individuals in all age groups, the prevalence of subtypes of STSs changes significantly from childhood through adolescence into adulthood. The mainstay of therapy is surgery, with or without the addition of chemotherapy and/or radiation therapy. These treatment modalities are associated, in many cases, with significant morbidity and, given the heterogeneity of tumor histologies encompassed by the term "STS", have not uniformly improved outcomes. Moreover, some subgroups of STSs appear to be more, and others less, responsive to conventional chemotherapy agents. Over the last two decades, our understanding of the biology of STSs is slowly increasing, allowing for the development of more targeted therapies. We review the new treatment modalities that have been tested on patients with STSs, with a special focus on adolescents and young adults, a group of patients that is often underrepresented in clinical trials and has not received the dedicated attention it deserves, given the significant differences in biology and treatment response in comparison to children and adults.

Treatment pathway of bone sarcoma in children, adolescents, and young adults

When pediatric, adolescent, and young adult patients present with a bone sarcoma, treatment decisions, especially after relapse, are complex and require a multidisciplinary approach. This review presents scenarios commonly encountered in the therapy of bone sarcomas with the goal of objectively presenting a consensus, multidisciplinary management approach. Little variation was found in the authors' group with respect to local control or systemic therapy. Clinical trials were universally prioritized in all settings. Decisions regarding relapse therapies in the absence of a clinical trial had very minor variations initially, but a consensus was reached after a literature review and discussion. This review presents a concise document and figures as a starting point for evidence‐based care for patients with these rare diseases. This framework allows prospective decision making and prioritization of clinical trials. It is hoped that this framework will inspire and focus future clinical research and thus lead to new trials to improve efficacy and reduce toxicity. Cancer 2017;123:2206–2218. © 2017 American Cancer Society.

This review presents a pathway for the management of common clinical scenarios that arise in the treatment of bone sarcomas in children, adolescents, and young adults. Clinical trials should be prioritized when they are available, and for those times when trials are unavailable, a consensus, multidisciplinary management approach to bone sarcomas is presented.

Phase 2 study of dasatinib in patients with alveolar soft part sarcoma, chondrosarcoma, chordoma, epithelioid sarcoma, or solitary fibrous tumor

BACKGROUND

Alveolar soft part sarcoma (ASPS), chondrosarcoma (CS), chordoma, epithelioid sarcoma, and solitary fibrous tumor (SFT) are malignant tumors that are relatively resistant to chemotherapy and for which more effective drug therapy is needed.

METHODS

The 5 listed subtypes were enrolled into a single indolent sarcoma cohort in a phase 2 study of dasatinib using a Bayesian continuous monitoring rule for enrollment. The primary objective was to estimate the 6-month progression-free survival (PFS) rate according to the Choi criteria with a target of ≥50%. Cross-sectional imaging was performed before the start of treatment, every 2 months for 6 months, and then every 3 months during treatment. The 2- and 5-year survival rates were determined.

RESULTS

One hundred sixteen patients were enrolled within 45 months, and 109 began treatment with dasatinib. The 6-month PFS rate and the median PFS were 48% and 5.8 months, respectively. The PFS rate at 6 months was highest with ASPS (62%) and lowest with SFT (30%). More than 10% of the patients with ASPS, CS, or chordoma had stable disease for more than 1 year. Collectively, for all 5 subtypes, the 2- and 5-year overall survival rates were 44% and 13%, respectively. An objective response was observed in 18% of the patients with CS or chordoma.

CONCLUSIONS

Dasatinib failed to achieve control of sarcoma growth for at least 6 months in more than 50% of the patients in this trial according to the Choi tumor response criteria. An objective tumor response and prolonged stable disease was observed in >10% of patients with CS or chordoma. Cancer 2017;90-97. © 2016 American Cancer Society.

Induction of Immune Response after Allogeneic Wilms' Tumor 1 Dendritic Cell Vaccination and Donor Lymphocyte Infusion in Patients with Hematologic Malignancies and Post-Transplantation Relapse

Relapse of hematologic malignancies is the primary cause of treatment failure after allogeneic hematopoietic stem cell transplantation (HCT). Treatment for post-HCT relapse using donor lymphocyte infusion (DLI) has limited utility, particularly in the setting of acute leukemia, and can result in the development of graft-versus-host disease (GVHD). The Wilms' tumor 1 (WT1) gene product is a tumor-associated antigen that is expressed in acute leukemia and other hematologic malignancies, with limited expression in normal tissues. In this pilot trial, we assessed safety and feasibility of a WT1 peptide-loaded donor-derived dendritic cell (DC) vaccine given with DLI designed to enhance and direct the graft-versus-leukemia effect. Secondary objectives were to evaluate immunologic and clinical responses. A total of 5 subjects, median age 17 years (range, 9 to 19 years), with post-HCT relapse were enrolled. Disease subtypes included acute lymphoblastic leukemia (n = 3), acute myelogenous leukemia (n = 1), and Hodgkin lymphoma (n = 1). Successful vaccine production was feasible from all donors. DC vaccination and DLI were well tolerated. One recipient developed grade 1 skin GVHD not requiring systemic therapy. The most common adverse events included grade 1 reversible pain and pruritus at the vaccine injection and delayed-type hypersensitivity (DTH) skin testing sites. There were no grade 3 or higher adverse events related to the research. Immune responses consisted of ELISpot response in 3 recipients and positive DTH tests to WT1 peptide cocktail in 2 subjects. Our study provides 1 of the first attempts to apply tumor-specific vaccine therapy to the allogeneic setting. Preliminary results show the DC-based vaccination is safe and feasible after allogeneic HCT, with a suggestion that this approach can be used to sensitize the repopulated allogeneic-donor immune system to WT1. Future directions may include testing of vaccination strategies in the early post-transplantation setting for relapse prevention.

Desmoplastic small round cell tumor: postoperative retroperitoneal mass

We describe the case of a 14-year-old boy who presented with a large, 17.6-cm retroperitoneal mass, along with multiple metastases, and was diagnosed with desmoplastic small round cell tumor. After initial chemotherapy, he underwent gross total resection with a positive margin. On postoperative radiation planning computed tomography, a 6.8-cm heterogeneous mass was noted in the surgical bed. Given the tumor's aggressive nature and positive surgical margins, there was real concern for recurrent disease. Further evaluation with magnetic resonance imaging elucidated that the mass consisted of simple fluid and fat, without contrast enhancement, suggesting a postoperative fluid collection. He was able to continue with adjuvant treatment as planned. This case example illustrates that even large postoperative heterogeneous masses may still be related to postoperative fluid collection in patients with aggressive tumor. However, it is important to rule out recurrent disease before starting adjuvant therapy given improved outcomes with gross total resection in desmoplastic small round cell tumor.

Strengths and Weaknesses of a Planar Whole-Body Method of (153)Sm Dosimetry for Patients with Metastatic Osteosarcoma and Comparison with Three-Dimensional Dosimetry

PURPOSE

Dosimetric accuracy depends directly upon the accuracy of the activity measurements in tumors and organs. The authors present the methods and results of a retrospective tumor dosimetry analysis in 14 patients with a total of 28 tumors treated with high activities of (153)Sm-ethylenediaminetetramethylenephosphonate ((153)Sm-EDTMP) for therapy of metastatic osteosarcoma using planar images and compare the results with three-dimensional dosimetry.

MATERIALS AND METHODS

Analysis of phantom data provided a complete set of parameters for dosimetric calculations, including buildup factor, attenuation coefficient, and camera dead-time compensation. The latter was obtained using a previously developed methodology that accounts for the relative motion of the camera and patient during whole-body (WB) imaging. Tumor activity values calculated from the anterior and posterior views of WB planar images of patients treated with (153)Sm-EDTMP for pediatric osteosarcoma were compared with the geometric mean value. The mean activities were integrated over time and tumor-absorbed doses were calculated using the software package OLINDA/EXM.

RESULTS

The authors found that it was necessary to employ the dead-time correction algorithm to prevent measured tumor activity half-lives from often exceeding the physical decay half-life of (153)Sm. Measured half-lives so long are unquestionably in error. Tumor-absorbed doses varied between 0.0022 and 0.27 cGy/MBq with an average of 0.065 cGy/MBq; however, a comparison with absorbed dose values derived from a three-dimensional analysis for the same tumors showed no correlation; moreover, the ratio of three-dimensional absorbed dose value to planar absorbed dose value was 2.19. From the anterior and posterior activity comparisons, the order of clinical uncertainty for activity and dose calculations from WB planar images, with the present methodology, is hypothesized to be about 70%.

CONCLUSION

The dosimetric results from clinical patient data indicate that absolute planar dosimetry is unreliable and dosimetry using three-dimensional imaging is preferable, particularly for tumors, except perhaps for the most sophisticated planar methods. The relative activity and patient kinetics derived from planar imaging show a greater level of reliability than the dosimetry.

Abstract 4119: Inhibition of PORCN prolongs metastasis free survival in a mouse model of Ewing sarcoma

Metastatic disease is the most important factor in determining the survival of patients with Ewing sarcoma (ES). Although intensive cytotoxic chemotherapy has improved the survival of patients with localized disease, the survival rate for patients with metastatic disease remains dismal, and the most pressing unmet need in ES is to prevent and treat metastasis better. The Wnt signaling pathway is a key regulator of a number of cellular functions associated with metastasis, including proliferation, motility, and stem cell self-renewal. A single enzyme, Porcupine (Porcn), mediates post-translational palmitoylation of Wnt ligands, and it's activity is required for secretion of all 17 Wnt ligands, making it an attractive target for a pan-Wnt inhibitor. We have studied the effect of LGK974, a potent, selective, Porcn inhibitor, on Ewing sarcoma metastasis. In vitro, we have observed that LGK974 does not affect proliferation or sarcosphere formation, but inhibits migration of ES cell lines through the suppression of expression of multiple transcriptional regulators of Epithelial-Mesenchymal Transition (EMT). In our orthotopic implantation/amputation mouse model, single agent LGK974 treatment leads to significant delay in formation of lung metastasis following amputation of the affected leg, without a significant effect on primary tumor growth. This delay leads to a significant post-amputation survival benefit in multiple xenografts. In LGK974 treated xenografts, the expression of multiple EMT related transcription factors were observed to be suppressed. Furthermore, in tail vein injection models, LGK974 did not produce a survival benefit, suggesting that LGK974 effects Ewing sarcoma metastasis by inhibiting early steps in the metastatic cascade, such as migration and invasion. Our findings strongly implicate Wnt signaling in the early steps of ES metastasis and demonstrate that LGK974 has the potential to significantly improve the survival of ES patients through the specific inhibition of metastasis.

Citation Format: Masanori Hayashi, Alissa C. Baker, Seth D. Goldstein, Catherine M. Albert, Kyle W. Jackson, David M. Loeb. Inhibition of PORCN prolongs metastasis free survival in a mouse model of Ewing sarcoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4119.

Highly personalized detection of minimal Ewing sarcoma disease burden from plasma tumor DNA

BACKGROUND

Even though virtually all patients with Ewing sarcoma achieve a radiographic complete response, up to 30% of patients who present with localized disease and up to 90% of those who present with metastases experience a metastatic disease recurrence, highlighting the inability to identify patients with residual disease at the end of therapy. Up to 95% of Ewing sarcomas carry a driving EWS-ETS translocation that has an intronic breakpoint that is specific to each tumor, and the authors developed a system to quantitatively detect the specific breakpoint DNA fragment in patient plasma.

METHODS

The authors used a long-range multiplex polymerase chain reaction (PCR) technique to identify tumor-specific EWS-ETS breakpoints in Ewing sarcoma cell lines, patient-derived xenografts, and patient tumors, and this sequence was used to design tumor-specific primer sets to detect plasma tumor DNA (ptDNA) by droplet digital PCR in xenograft-bearing mice and patients.

RESULTS

Tumor-specific breakpoint DNA fragments were detected in the plasma of xenograft-bearing mice, and the signal correlated with tumor burden during primary tumor growth, after surgical resection, and at the time of metastatic disease recurrence. Furthermore, the authors were able to detect the specific breakpoint in plasma DNA obtained from 3 patients with Ewing sarcoma and in 2 patients the authors were able to detect ptDNA when there was radiographically undetectable disease present.

CONCLUSIONS

The use of droplet digital PCR to detect tumor-specific EWS-ETS fusion gene breakpoint ptDNA fragments can be developed into a highly personalized biomarker of disease recurrence that can be optimized in animal studies for ultimate use in patients. Cancer 2016;122:3015-3023. © 2016 American Cancer Society.

Abstract B37: Detection of sarcoma circulating tumor cells using a size based microfiltration device

The inability to effectively treat hematogenous metastasis remains the largest challenge of sarcoma therapy. The ability to isolate, quantify, and study circulating tumor cells (CTC) in sarcomas has the potential to enhance our understanding of the biology of metastasis, altering the way we treat patients with high grade sarcomas. Using a size based filtration device, CellSieve™, we were able to successfully identify and quantify CTC in a metastatic xenograft model as well as in blood samples from patients with high grade sarcomas. In mice, we utilized our orthotopic implantation/amputation model of metastasis. Using a TdTomato-expressing Ewing sarcoma cell line and a cocktail of fluorescently labeled antibodies to vimentin and CD45, we were able to detect both CTC and circulating tumor clusters (CTCL) in mice with growing tumors and with metastatic disease, but not in mice immediately post-amputation. These experiments were augmented with samples collected from patients with high grade sarcomas. In 18 samples from 15 patients, we were able to identify both CTC and CTCL. Furthermore, we were also able to validate the presence of CTC by PCR amplification of sarcoma-associated chromosomal translocations. Future work will use this system to explore the biology of sarcoma metastasis by studying genetic, transcriptional, and epigenetic characteristics of CTC and CTCL and comparing these cells to those in the bulk primary tumor. We will also further explore the possibility that CTC and/or CTCL might serve as a biomarker of disease burden, response to treatment, or metastatic risk.

Citation Format: Masanori Hayashi, Peixuan Zhu, Catherine M. Albert, Diana Steppan, Gregory McCarty, Kyle W. Jackson, Cha-Mei Tang, David M. Loeb. Detection of sarcoma circulating tumor cells using a size based microfiltration device. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B37.

SARC009: Phase 2 study of dasatinib in patients with previously treated, high-grade, advanced sarcoma

BACKGROUND

Dasatinib exhibited activity in preclinical models of sarcoma. The Sarcoma Alliance for Research through Collaboration (SARC) conducted a multicenter, phase 2 trial of dasatinib in patients with advanced sarcoma.

METHODS

Patients received dasatinib twice daily. The primary objective was to estimate the clinical benefit rate (CBR) (complete response or partial response within 6 months or stable disease duration of ≥6 months) with a target of ≥25%. Patients were enrolled into 1 of 7 different cohorts and assessed by imaging every 8 weeks using Choi criteria tumor response and a Bayesian hierarchical design. For each subtype, enrollment was stopped after a minimum of 9 patients were treated if there was a <1% chance the CBR was ≥25%.

RESULTS

A total of 200 patients were enrolled. Accrual was stopped early in 5 cohorts because of low CBR. The leiomyosarcoma (LMS) and undifferentiated pleomorphic sarcoma (UPS) cohorts fully accrued and 6 of 47 and 8 of 42 evaluable patients, respectively, exhibited clinical benefit. The probability that the CBR was ≥25% in the LMS and UPS cohorts was 0.008 and 0.10, respectively. The median progression-free survival ranged from 0.9 months in patients with rhabdomyosarcoma to 2.2 months in patients with LMS. The median overall survival was 8.6 months. The most frequent adverse events were constitutional, gastrointestinal, and respiratory, and 36% of patients required dose reduction for toxicity. Serious adverse events attributed to therapy occurred in 11% of patients.

CONCLUSIONS

Dasatinib may have activity in patients with UPS but is inactive as a single agent in the other sarcoma subtypes included herein. The Bayesian design allowed for the early termination of accrual in 5 subtypes because of lack of drug activity.

RNA helicase DDX3: a novel therapeutic target in Ewing sarcoma

RNA helicase DDX3 has oncogenic activity in breast and lung cancers and is required for translation of complex mRNA transcripts, including those encoding key cell-cycle regulatory proteins. We sought to determine the expression and function of DDX3 in sarcoma cells, and to investigate the antitumor activity of a novel small molecule DDX3 inhibitor, RK-33. Utilizing various sarcoma cell lines, xenografts and human tissue microarrays, we measured DDX3 expression at the mRNA and protein levels, and evaluated cytotoxicity of RK-33 in sarcoma cell lines. To study the role of DDX3 in Ewing sarcoma, we generated stable DDX3-knockdown Ewing sarcoma cell lines using DDX3-specific small hairpin RNA (shRNA), and assessed oncogenic activity. DDX3-knockdown and RK-33-treated Ewing sarcoma cells were compared with wild-type cells using an isobaric mass-tag quantitative proteomics approach to identify target proteins impacted by DDX3 inhibition. Overall, we found high expression of DDX3 in numerous human sarcoma subtypes compared with non-malignant mesenchymal cells, and knockdown of DDX3 by RNA interference inhibited oncogenic activity in Ewing sarcoma cells. Treatment with RK-33 was preferentially cytotoxic to sarcoma cells, including chemotherapy-resistant Ewing sarcoma stem cells, while sparing non-malignant cells. Sensitivity to RK-33 correlated with DDX3 protein expression. Growth of human Ewing sarcoma xenografts expressing high DDX3 was inhibited by RK-33 treatment in mice, without overt toxicity. DDX3 inhibition altered the Ewing sarcoma cellular proteome, especially proteins involved in DNA replication, mRNA translation and proteasome function. These data support further investigation of the role of DDX3 in sarcomas, advancement of RK-33 to Ewing sarcoma clinical trials and development of RNA helicase inhibition as a novel anti-neoplastic strategy.

Single-Agent Post-Transplantation Cyclophosphamide as Graft-versus-Host Disease Prophylaxis after Human Leukocyte Antigen-Matched Related Bone Marrow Transplantation for Pediatric and Young Adult Patients with Hematologic Malignancies

High-dose cyclophosphamide given after HLA-matched related and unrelated allogeneic bone marrow transplantation (BMT) for patients with hematologic malignancies is effective single-agent graft-versus-host disease (GVHD) prophylaxis in adults. Data describing outcomes for pediatric and young adult patients have not been reported. Between the years 2007 and 2013, 29 pediatric and young adult patients ages ≤21 years of age treated at our institution for high-risk hematologic malignancies underwent myeloablative HLA-matched related T cell-replete BMT. Eleven patients received post-transplantation cyclophosphamide (PTCy) as single-agent GVHD prophylaxis and were followed prospectively. Eighteen patients received calcineurin inhibitor (CNI)-based standard GVHD prophylaxis and were studied retrospectively as a control group. No acute GVHD (aGVHD) developed in patients receiving PTCy, whereas patients receiving CNI-based GVHD prophylaxis had cumulative incidences of grades II to IV and grades III and IV aGVHD of 27% and 5%, respectively. No patients receiving PTCy developed chronic GHVD, compared to 1 in the control group. Two-year overall survival was similar between the 2 groups (54% PTCy versus 58% CNI-based prophylaxis), as was event-free survival (42% PTCy versus 47% CNI-based). The 5-year cumulative incidence of relapse was 58% for PTCy and 42% for CNI-based GVHD prophylaxis (P = .45). These results suggest that PTCy is a safe and efficacious method of GVHD prophylaxis after an HLA-matched related BMT in the pediatric and young adult population that affords patients to be off all post-transplantation immunosuppression on day +5.

Caspase-8 expression is predictive of tumour response to death receptor 5 agonist antibody in Ewing's sarcoma

Background:

Despite good initial response to chemotherapy, 30% of Ewing's sarcoma (EWS) patients with localised tumours develop recurrent disease, associated with poor prognosis. The aim of this study was to address this challenge by conducting preclinical evaluation of a death receptor targeted agent in vitro and in vivo, and by identifying predictive biomarkers.

Methods:

Cell viability assays, drug dose responses, immunoblots, rescue with gene transfer, mice tumour models, and statistical comparisons of tumour growth and Kaplan–Meier survival curves.

Results:

This study shows that many EWS cell lines are selectively sensitive to a death receptor DR5 antibody and are more resistant to a DR4 antibody. Preclinical evaluation of these cell lines indicates their sensitivity to human DR5 agonist antibody conatumumab in vitro, which induces rapid activation of caspase-8 and apoptosis. We also found that sensitivity to conatumumab correlates with expression of caspase-8. Furthermore, the catalytic activity of caspase-8 is both necessary and sufficient to confer this sensitivity. In vivo, conatumumab is active against an EWS cell line and a patient-derived xenograft with higher caspase-8 expression, but is not effective against another with lower caspase-8 expression.

Conclusions:

These studies suggest the potential of conatumumab as a therapeutic agent against EWS and caspase-8 as a predictive biomarker for sensitivity.

Abstract 2917: Caspase-8 expression is predictive of tumor response to death receptor 5 agonist antibody conatumumab in Ewing's sarcoma

Despite good initial response to cytotoxic chemotherapy, approximately 30% of Ewing's sarcoma (EWS) patients who present with localized tumors develop recurrent disease, which is associated with poor prognosis. Addressing this clinical challenge requires the development of targeted therapies. This study shows that many EWS cell lines are selectively sensitive to a death receptor DR5 antibody and are more resistant to a DR4 antibody. Preclinical evaluation of these cell lines indicates their sensitivity to human DR5 agonist antibody conatumumab in vitro, which induces rapid activation of caspase-8 and apoptosis. Further analysis reveals the correlation of sensitivity to conatumumab with the expression of caspase-8, with its catalytic activity both necessary and sufficient to confer such sensitivity. In vivo, conatumumab has active against both EWS cell lines and a patient-derived xenograft with higher caspase-8 expression, but is not effective against another patient-derived xenograft with lower caspase-8 expression. These studies suggest the potential of conatumumab as a therapeutic agent against EWS and caspase-8 as a biomarker for correlative studies.

Citation Format: Zhigang Kang, D Seth Goldstein, Yunkai Yu, Paul S. Meltzer, David M. Loeb, Liang Cao. Caspase-8 expression is predictive of tumor response to death receptor 5 agonist antibody conatumumab in Ewing's sarcoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2917. doi:10.1158/1538-7445.AM2015-2917