Tabelecleucel for EBV+ PTLD following allogeneic HCT or SOT in a multicenter expanded access protocol

Patients with Epstein-Barr virus (EBV)-positive post-transplant lymphoproliferative disease (EBV+ PTLD) in whom initial treatment fails have few options and historically low median overall survival (OS) of 0.7 months following allogeneic hematopoietic cell transplant (HCT) and 4.1 months following solid organ transplant (SOT). Tabelecleucel is an off-the-shelf, allogeneic EBV-specific cytotoxic T-lymphocyte immunotherapy for EBV+ PTLD. Previous single-center experience showed responses in patients with EBV+ PTLD following HCT or SOT. We now report outcomes from a multicenter expanded access protocol (NCT02822495) in HCT (n = 14) and SOT (n = 12) recipients treated with tabelecleucel for EBV+ PTLD that was relapsed/refractory to rituximab ± chemotherapy. The investigator-assessed objective response rate was 65.4% overall (including 38.5% with a complete and 26.9% with a partial response), 50.0% in HCT, and 83.3% in SOT. The estimated 1- and 2-year OS rates (95% CI) were both 70.0% (46.5, 84.7) overall, both 61.5% (30.8, 81.8) in HCT, and both 81.5% (43.5, 95.1) in SOT (median follow-up: 8.2, 2.8, and 22.5 months, respectively). Patients responding to tabelecleucel had higher 1- and 2-year OS rates (94.1%) than non-responders (0%). Treatment was well tolerated with no reports of tumor flare, cytokine release syndrome, or rejection of marrow and SOT. Results demonstrate clinically meaningful outcomes across a broad population treated with tabelecleucel, indicating a potentially transformative and accessible treatment advance for relapsed/refractory EBV+ PTLD following HCT or SOT.

Breaking down the tumor immune infiltration within pediatric sarcomas

Immunotherapies are a promising therapeutic option, yet for a variety of reasons, these treatments have achieved limited success against sarcomas. The immunosuppressive tumor microenvironment (TME) of sarcomas as well as lack of predictive biomarkers, decreased T-cell clonal frequency, and high expression of immunosuppressive infiltrating cells has thus far prevented major success using immunotherapies. By breaking down the TME into its individual components and understanding how the various cell types interact with each other as well as in the context of the complex immune microenvironment, can lead to effective therapeutic immunotherapy treatments, potentially improving outcomes for those with metastatic disease.

Impact of race/ethnicity and language preferences on pediatric ALL survival outcomes

BACKGROUND

Ethnic and racial disparities have recently been observed both in treatment-related toxicities and rates of long-lasting cure in acute lymphoblastic leukemia (ALL) and acute lymphoblastic lymphoma (ALLy), the most common pediatric malignancy. Despite significant improvements in overall survival in the recent past, a large number of children die from aggressive disease.

METHODS

We performed a retrospective cohort analysis of 274 pediatric ALL/ALLy patients within Montefiore Health System from 2004 to 2021 to determine differences in all-cause mortality within the Pediatric Hematologic Malignancies Cohort using Cox Proportional Hazard regression modeling, adjusted for age at diagnosis, race/ethnicity, administration of intensive chemotherapy, preferred language, maximum glucose, and hypertension.

RESULTS

Among our 274 patients, 132 were Hispanic, 54 Non-Hispanic Black, and 25 Non-Hispanic White, with 25 identified as "Non-Hispanic Other," including Asian, Arabic, and Other. Hispanic patients were 78% less likely to die (HR 0.22; 95% CI 0.07, 0.73) when compared with Non-Hispanic Black individuals. Spanish speakers were 2.91 times more likely to die compared with those who spoke English (HR 2.91; 95% CI 1.08, 7.82). Among those English speakers, the diagnosis of hypertension and Hispanic ethnicity significantly impacted the risk of death, while these factors did not impact survival in Spanish speakers. High-risk cytogenetics did not impact survival.

CONCLUSIONS

Hispanic children with ALL/ALLy have improved survival outcomes compared with Non-Hispanic Blacks. Additionally, Spanish language preference was strongly associated with poorer survival, a novel finding that should be validated in future studies.

Abstract 6211: Targeting the tumor microenvironment of metastasis to treat metastatic Ewing sarcoma

Introduction: Ewing sarcoma (EWS) is the second most common bone cancer in adolescents and young adults. Intensive multimodal treatment cures almost 75% of patients who present with localized disease. However, only 25% of patients who present with metastases become long term survivors, and those who suffer a metastatic relapse are almost never cured. Recently, a 3-cell assembly consisting of an invasive cancer cell, a Tie2-high expressing macrophage, and an endothelial cell (termed the Tumor Microenvironment of Metastasis, or TMEM), has been described as the doorway through which breast cancer cells enter the vasculature and disseminate to distant sites. We hypothesized that EWS cells use a similar mechanism for dissemination, and that targeting TMEM offers a novel therapeutic opportunity to prevent metastatic recurrence.

Methods: Formalin-fixed, paraffin embedded tissue samples were obtained from 16 patients with EWS treated at our institution, and these were evaluated for the presence of TMEM structures by immunohistochemistry. We also evaluated samples obtained from our novel, clinically relevant murine model of spontaneous distant EWS metastasis. Fragments of EWS either from cell line-derived tumors or patient-derived xenografts (PDX) orthotopically or subcutaneously. After tumors grew, mice were injected with fluorescent dextran in the tail vein and tumors harvested 60 minutes later. Intravascular dextran remains inside blood vessels because the molecular weight is too large to allow diffusion between endothelial cells. As TMEM disrupts the endothelial barrier, dextran leaks out of blood vessels and can be detected and quantified using fluorescence microscopy. Tumors were evaluated for the presence of TMEM structures by immunohistochemistry (IHC), and for the presence of localized vascular leakiness, (the hallmark of functional TMEM), by fluorescence microscopy.

Results: We found TMEM assemblies in all patient samples, at numbers well in excess of those seen in samples of metastatic breast cancer. Interestingly, although there was no difference in TMEM counts from patients who were survivors compared with those who died from metastatic disease, there was an increase in TMEM counts in samples from tumors that were exposed to chemotherapy compared to diagnostic biopsy samples, something also reported in breast cancer patients. We also identified TMEM assemblies and localized vascular leakiness in EWS PDX tumors implanted orthotopically.

Discussion: TMEM assemblies are present in both EWS patient samples and PDX models, suggesting that this important mechanism of tumor intravasation into the vasculature may be contributing to distant metastasis. Future work will focus on identifying drugs that inhibit the function of TMEM, with the goal of translating this work into clinical trials aimed at diminishing the burden of metastasis in EWS patients.

Citation Format: Rachel Offenbacher, Yu Lin, George Karagiannis, Maja Oktay, David Loeb. Targeting the tumor microenvironment of metastasis to treat metastatic Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6211.

Clinician and staff perspectives on potential disparities introduced by the rapid implementation of telehealth services during COVID-19: a mixed-methods analysis

The COVID-19 pandemic has rapidly altered ambulatory health care delivery and may have worsened disparities in health care access. To assess the telehealth implementation experiences of ambulatory personnel in different disciplines and their perspectives on potential telehealth disparities, and to make recommendations for more equitable telehealth delivery. We used a convergent parallel mixed-methods design. Clinic managers from geriatric medicine, internal medicine, and psychiatry e-mailed a survey to clinicians and staff regarding experiences with telehealth care delivery. Quantitative survey responses were analyzed with Fisher's Exact tests. Qualitative responses were coded thematically. Recommendations were categorized by type of implementation strategy. Quantitative and qualitative findings on telehealth disparities were merged in a joint data display. Respondents (n = 147, 57% response rate) were distributed across three specialties: 66% internal medicine, 19% psychiatry, and 14% geriatric medicine. Prior to 2020, 77% of clinicians had never delivered telehealth services. By Spring 2020, 78% reported conducting more than half of clinic visits by telehealth. Among clinicians, 52% agreed/strongly agreed that rapid telehealth implementation exacerbated access to care disparities to: older adult patients, those with limited internet access, and those needing interpretation services. Staff expressed similar difficulties with telehealth set-up especially for these patients. To improve telehealth equity, clinicians recommended to: (i) change infrastructure; (ii) train and educate stakeholders; and (iii) support clinicians. Clinicians and staff reported specific subpopulations had challenges in accessing telehealth visits. To avoid perpetuating telehealth access disparities, further co-discovery of equitable implementation strategies with patients and clinics are urgently needed.

Phase 1 expansion trial of the LSD1 inhibitor seclidemstat (SP-2577) with and without topotecan and cyclophosphamide (TC) in patients (pts) with relapsed or refractory Ewing sarcoma (ES) and select sarcomas

TPS11577

Background: Several sarcomas possess chromosomal translocations in FET family members ( FUS, EWSR1, and TAF15) responsible for cancer development. Sarcomas caused by FET family gene rearrangements include ES, desmoplastic round cell small tumors (DSRCT), myxoid liposarcoma (ML), and several others. Lysine specific demethylase 1 (LSD1) is a critical protein for sarcoma development and progression through its colocalization and/or association with several FET family oncogenic transcription factors. This suggests that pharmacologic inhibition of LSD1 may be a therapeutic strategy. Seclidemstat (SP-2577, Salarius Pharmaceuticals) is an oral, first-in-class, small molecule with reversible, noncompetitive inhibition of LSD1 (IC50: 25–50 nM). In vitro and in vivo data demonstrate seclidemstat, or analogs, modulate EWS/ETS transcriptional activity, down-regulating oncogene expression and up-regulating tumor-suppressor gene expression, leading to significant tumor growth inhibition in ES mouse xenograft studies. Seclidemstat has shown in in vitro ES cell lines near additivity efficacy when added to TC. In in vitro studies of other FET-translocated sarcomas, including ML (FUS/DDIT3 fusion) and clear cell sarcoma (EWS/ATF1 fusion), seclidemstat showed anti-proliferative activity. In an ongoing Phase 1 trial investigating single agent seclidemstat in advanced solid tumors (NCT03895684), three pts with metastatic FET-translocated sarcomas had a median progression-free survival of 5.7 months (range: 4.3–7.2) with a best response of stable disease despite having a median of 5 (range: 1–7) prior therapies. Methods: This dose expansion Phase 1 study (NCT03600649) assesses seclidemstat at 900 mg PO BID, the recommended Phase 2 dose, in two expansion cohorts: a single agent expansion in select sarcoma pts (n = 30) and a safety lead-in dose escalation and expansion (n = 24) of seclidemstat combined with TC in pts with ES. Pts must be ≥12 years old, have ECOG performance status of 0 or 1, with a life expectancy > 4 months. In the select sarcoma cohort, pts must have ML (n = 15) or other sarcomas with FET family translocations (n = 15) including DSRCT. One to 3 prior lines of therapy are allowed. In the ES combination cohort, up to 2 lines of prior therapy are allowed. Primary objective is safety/tolerability and secondary objective is efficacy. The trial is currently recruiting across 8 locations in the United States. Clinical trial information: NCT03600649.

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.

The Utility of 18FDG PET/CT Versus Bone Scan for Identification of Bone Metastases in a Pediatric Sarcoma Population and a Review of the Literature

BACKGROUND

Outcome of patients with osteosarcoma (OS) and Ewing sarcoma (EWS) is dependent on presence of metastases. Imaging guidelines for OS and EWS include radiographs, computed tomography (CT), and magnetic resonance imaging for primary tumor evaluation and CT chest and bone scintigraphy (BS) for metastatic detection. 18Fluorodeoxyglucose (18FDG) positron emission tomography (PET)/CT has become more common for disease evaluation, yet there is no consensus for its use in this population.

OBJECTIVE

We aimed to compare identification of osseous metastases using BS versus 18FDG PET/CT in our patient population. We hypothesized that 18FDG PET/CT is more likely to detect osseous metastases both at diagnosis and relapse.

MATERIALS AND METHODS

We performed retrospective chart reviews of pediatric sarcoma patients treated at our institution from 2008 to 2019. Paired BS and 18FDG PET/CT scans were reviewed. Review of the literature was also performed.

RESULTS

Thirty-three patients had paired BS and 18FDG PET/CT during diagnosis or treatment. Fifteen patients had distant osseous metastases. In the OS cohort, 8/16 patients had osseous metastases; 100% of these patients were detected on 18FDG PET/CT and 75% on BS. Thirty-one bony lesions were seen on imaging in OS patients; 100% of these were identified on 18FDG PET/CT but only 29% on BS. In the EWS cohort, 6/15 patients had osseous metastases; 100% of these patients were detected on 18FDG PET/CT and 50% on BS. Eighteen bony lesions were seen on imaging in EWS patients; 94% of these were identified on 18FDG PET/CT, but only 28% on BS.

CONCLUSION

For patients in our institution with OS or EWS, osseous metastases were more likely detected using 18FDG PET/CT.

Electrophysiological effects of anthracyclines in adult survivors of pediatric malignancy

BACKGROUND

Anthracycline use is limited by cardiotoxicity, including arrhythmias and left ventricular (LV) dysfunction. We aim to characterize the association between electrophysiological changes and LV dysfunction.

METHODS

A retrospective chart review was conducted, including all 147 pediatric cancer survivors at our institution over 18 years of age and treated with an anthracycline. One hundred thirty-four patients who had at least one electrocardiogram (ECG) and echocardiogram were analyzed. The association between dysfunction and baseline characteristics, treatment history, and electrocardigraphic parameters were analyzed using multivariable logistic regression. Additionally, a longitudinal generalized estimating equation (GEE) model was used to examine the temporal association between repeated measure corrected QT (QTc) intervals and subsequent LV function.

RESULTS

In our population, 24% of patients had LV dysfunction. The initial posttreatment QTc interval was longer in patients with LV dysfunction (438 ± 35 vs. 420 ± 20 msec, P = 0.002). In logistic regression analysis, QTc interval (P < 0.001) and cumulative radiation dose (P = 0.027) were associated with LV dysfunction. On ECGs performed prior to evidence of LV dysfunction, the QTc was longer than on ECGs preceding a normal echocardiogram (451 ± 32 msec vs. 423 ± 25 msec, P < 0.001). Mean time from QTc ≥ 450 msec to evidence of LV dysfunction was 1.8 ± 2.9 years. In the longitudinal GEE model, QTc prolongation was associated with subsequent decreased fractional shortening.

CONCLUSIONS

Among adult survivors of pediatric cancer treated with anthracyclines, prolongation of the QTc interval was associated with subsequent LV dysfunction.

Alternative-Donor Hematopoietic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide for Nonmalignant Disorders

Allogeneic hematopoietic stem cell transplantation (HSCT) is curative for many nonmalignant pediatric disorders, including hemoglobinopathies, bone marrow failure syndromes, and immunodeficiencies. There is great success using HLA-matched related donors for these patients; however, the use of alternative donors has been associated with increased graft failure, graft-versus-host disease (GVHD), and transplant-related mortality (TRM). HSCT using alternative donors with post-transplantation cyclophosphamide (PT/Cy) for GVHD prophylaxis has been performed for hematologic malignancies with engraftment, GVHD, and TRM comparable with that seen with HLA-matched related donors. There are limited reports of HSCT in nonmalignant pediatric disorders other than hemoglobinopathies using alternative donors and PT/Cy. We transplanted 11 pediatric patients with life-threatening nonmalignant conditions using reduced-intensity conditioning, alternative donors, and PT/Cy alone or in combination with tacrolimus and mycophenolate mofetil. We observed limited GVHD, no TRM, and successful engraftment sufficient to eliminate manifestations of disease in all patients. Allogeneic HSCT using alternative donors and PT/Cy shows promise for curing nonmalignant disorders; development of prospective clinical trials to confirm these observations is warranted.

Abstract A70: Targeting pediatric bone sarcoma stem cell with metabolic inhibitors

Our project tests whether metabolic inhibitors are able to target putative sarcoma stem cells in osteosarcoma and Ewing sarcoma. The cure rate for the two most common bone sarcomas affecting children and adolescents, osteosarcoma and Ewing sarcoma, has plateaued around 70% over the past twenty years, and the cure rate for patients with metastatic bone sarcomas has not significantly improved over 20% in several decades. The subpopulation of cells in these tumors referred to as sarcoma stem cells are thought to be responsible for resistance to current therapies, relapses and metastases. To date therapies targeting the sarcoma stem cell population have not been identified. We studied the ability of metabolic inhibitors to eliminate the sarcoma stem cell population.

A panel of established and verified osteosarcoma (HOS, 143B, MNNG, SAOS2) and Ewing sarcoma (TC71, TC32, MHH, A4573, CHLA9, CHLA10) cell lines was grown in 2-dimensional culture and treated with metabolic inhibitors, including 2-deoxyglucose, dichloroacetate, oxamate, lonidamine, 3-Bromopyruvate, and metformin for 72hrs establishing dose response curves for each individual agent. Most agents showed IC50s in the millimolar range. Combinations of two metabolic inhibitors at their IC50 were then tested and evaluated for synergy and if the combination would allow for dosing at physiologically attainable concentrations. The combination of 2-deoxyglucose and metformin proved toxic to the osteosarcoma and Ewing sarcoma cell lines (p &lt;0.0001 compared to untreated cells) with synergy detected as measured by combination index &lt;1. In particular this combination showed activity against the stem cell population in all cell lines tested, including reduction of aldehyde dehydrogenase expression as measured by ALDEFLUOR reagent system (Stem Cell Technologies, Vancouver, BC), and decreased sphere-forming efficiency using Image-Pro Plus (MediaCybernetics, Rockville, MD).

The cells were then grown in 3-dimensional cultures using Magnetic 3D Bioprinting kit(n3D Biosciences, Houston, TX) and exposed to physiologically attainable concentrations of 2-deoxyglucose (500uM) and metformin (5uM), based on Phase I studies of these individual agents in humans. The resulting 3-dimentional cell cultures were incubated for 10 days with 2-deoxyglucose and metformin and there was a significant reduction in cell proliferation as measured by trypan blue dye exclusion and reduced aldehyde dehydrogenase expression. Additionally, the functional assay of cancer stem cells, sphere-forming efficiency, was impeded in all cell lines treated with the combination of 2-deoxyglucose and metformin. Finally, the ability to establish orthotopic tumors in immune deficient mice was significantly reduced for intratibialy-injected cells pretreated with 2-deoxyglucose and metformin. In vivo testing of the combination of 2-deoxyglucose and metformin to treat established xenograft osteosarcoma and Ewing sarcomas is currently underway, and resulting tumors will be harvested and assessed for aldehyde dehydrogenase expression, sphere-forming efficiency, and further characterization of the stem cell properties and metabolic alterations. Our study will provide the preclinical basis for testing metabolic inhibitors, in particular the combination of 2-deoxyglucose and metformin, in clinical trials for pediatric bone sarcomas.

Citation Format: Matteo Trucco, Nino Rainsusso, Piti Techavichit, Ronald Bernardi, Ryan Shuck, Laura Satterfield, Wendy Allen-Rhoades, Larry Donehower, David Loeb, Jason Yustein. Targeting pediatric bone sarcoma stem cell with metabolic inhibitors. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr A70.

Abstract 2418: Establishment and characterization of a primary chordoma xenograft

Chordomas are slow growing, malignant cancers believed to originate from notochord remnants. Chordoma accounts for 1% of cancers of the central nervous system with an annual incidence of 0.08 cases per 100,000 individuals. There are 3 different histologic subtypes- classic chordoma, chondroid chordoma, and dedifferentiated chordoma. Chordomas are characterized by the presence of physaliphorous cells with vacuolated cytoplasm and high expression of the transcription factor T Brachury. Management of chordoma is primarily surgical – chemotherapy and radiation therapy have limited effect. The development of effective treatments for this tumor is hampered by the lack of adequate animal models. We report here the establishment of the first primary xenograft model of chordoma. Tumor excised from a patient diagnosed with classic chordoma was implanted adjacent to the right proximal tibia in a NOD/SCID/IL2Rγ (null) mouse. The resulting tumor has been serially transplanted at least 10 times with no diminution in growth rate over time. Histologically, the xenograft does not appear to be a classic chordoma; interestingly, the patient from whom the xenograft was derived relapsed with a dedifferentiated morphology. To confirm the identity of the tumor xenograft, T brachyury expression was demonstrated by immunohistochemistry and PCR. We have begun to characterize this xenograft by gene expression profiling and comparative genomic hybridization. Expression profiling results were verified by RT-PCR. Cells isolated from xenografts were analyzed by the Aldefluor assay to assess the levels of expression of aldehyde dehydrogenase activity. A cell line was generated from this xenograft as well and is being characterized. In summary, we report here the establishment of the first primary chordoma xenograft. Initial molecular characterization of the xenograft and a cell line derived from this tumor is ongoing. These tools will shed valuable light on the pathophysiology of this rare tumor and allow the preclinical development of novel treatment strategies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2418. doi:10.1158/1538-7445.AM2011-2418

Abstract 4274: High aldehyde dehydrogenase activity identifies a chemotherapy-resistant population of ewing's sarcoma cells with a stem cell phenotype that retains sensitivity to EWS-FLI1 inhibition

Ewing's sarcoma family tumors (ESFT) are the second most common bone tumors in children and young adults. Despite being quite responsive to chemotherapy, patients with localized disease have a 30% recurrence rate, and 80% of patients with metastatic disease die within 5 years of diagnosis. The expression of the EWS-FLI1 fusion protein as a result of chromosomal translocation (11; 22) (q24; q12) is crucial for initiation and maintenance of the tumor; however, the mechanism by which EWS-FLI1 mediates neoplastic transformation is poorly understood. RNA helicase A (RHA) physically interacts with EWS-FLI1, modulating its oncogenic activity. The cancer stem cell hypothesis proposes that tumors originate from and are maintained by a small subset of chemotherapy-resistant stem cells. Thus, identification of Ewing's sarcoma stem cells will lead to the development of targeted therapies that should improve the treatment of patients with this disease. We attempted to identify a population of Ewing's sarcoma cells with stem cell properties (self-renewal in vitro, clonogenic activity, and tumor initiating activity in immunodeficient mice) based on high aldehyde dehydrogenase (ALDHhigh) activity. The ALDHhigh population was enriched for stem cell activity (compared to the ALDHlow cells) as defined by these assays, and was resistant to standard chemotherapy drugs to treat sarcomas (doxorubicin and etoposide). Both populations expressed EWS-FLI1. We then investigated whether a novel small molecule, YK-4-279, which specifically targets the RHA/EWS-FLI1 interaction, is toxic to the chemotherapy-resistant ALDHhigh cells. We found that the ALDHhigh cells retain sensitivity YK-4-279. Our data demonstrate that ESFT cells that express high levels of ALDH have stem-like properties, and, combined with evidence that YK-4-279 inhibits the growth of ESFT xenografts in mice, provide support for a novel approach to ESFT therapy. This approach should improve the survival of patients with these tumors in the future.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4274.

Physical and genetic mapping of the CMT4A locus and exclusion of PMP-2 as the defect in CMT4A

We have previously localized one form of the autosomal recessive Charcot-Marie-Tooth disease type 4 (CMT4A) to a 5-cM region of chromosome 8q13-q21. We now report the formation of a 7-Mb YAC contig spanning the region. This contig was used to map nine additional microsatellites and six STSs to this region, and subsequent haplotype analysis has narrowed the CMT4A flanking interval to less than 1 cM. In addition, using SSCP and our physical map, we have demonstrated that the myelin protein PMP-2, mapped by FISH to this region, is not the defect in CMT4A.

Partitioned pulsed-field gel electrophoresis-PCR (PPF-PCR): a new method for pulsed-field mapping for STS and microsatellites

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Puerperal Pasteurella multocida septicemia

A case of Pasteurella multocida infection in a puerperal healthy young women is reported. The agent was isolated from vaginal discharge and blood cultures of the patient, and also from pets and poultry with which the patient was in contact. Although Pasteurella multocida septicemia is rare, awareness of this infection and adequate intensive antibiotic therapy may improve its prognosis.

Two forms of ornithine decarboxylase activity in mouse kidney

Renal ornithine decarboxylase (ODC) activity was evaluated in normal female, male, testosterone-treated female and androgen-insensitive Tfm/Y mice for its heat sensitivity and in vivo half-life. ODC activity in normal female kidney consisted of 2 forms which differed in their heat sensitivity at 46 degrees C. Androgens, either endogenous in normal males or administered exogenously to females, induced primarily the heat-sensitive form. Results from mixing experiments indicated that the heat-sensitive form represented a change in the property of the ODC activity rather than a change in cytoplasmic factors. The in vivo half-life of ODC activity was increased slightly in males and short-term androgen-treated females over normal females and was markedly increased by prolonged androgen treatment. In vivo, the androgen-induced, heat-sensitive form decayed faster than did the heat-resistant form. We conclude that androgens have specific effects on both the amount as well as the biochemical properties of ODC activity in mouse kidney.