bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract A39: The novel atypical retinoid ST1926 is active against rhabdomyosarcoma and induces cell cycle arrest in S and G2/M phases
Authors: Basma Hussein , Dweik Loai , Darwiche Nadine , Pisano Claudio , Saab Raya
Published: May 2015

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children with two subtypes: embryonal rhabdomyosarcoma (ERMS) and alveolar rhabdomyosarcoma (ARMS). With current treatment strategies, most children with recurrent or high-risk disease fare poorly, identifying a need for novel therapeutic approaches. The novel retinoid, ST1926, is an orally available compound belonging to the class of synthetic atypical retinoids and is currently in clinical trials. ST1926 is showing promise because of its increased specificity and reduced toxicity and its unique antitumor mechanism of action that appears different from that of classical all-trans retinoic acid (ATRA). We are investigating the therapeutic potential of this novel synthetic retinoid ST1926, in treatment of RMS. Cell viability assessed by MTT assay showed that ST1926 was a much more potent inhibitor of cell proliferation than ATRA, in both ERMS and ARMS cell lines in vitro. In fact, ST1926 effectively inhibited cell proliferation in all tested cell lines, at concentrations as low as 0.5 micromolar, which is easily achievable in vivo. Unlike ATRA, ST1926 did not induce morphological differentiation in RMS cells. Further analysis showed that ST1926 induced accumulation of cells in S and/or in G2/M phases of the cell cycle, as well as induction of apoptosis in some cell lines, in a p53-independent manner. We are currently investigating the mechanistic details of the cell cycle inhibitory activities of ST1926 in RMS cells. This data identifies ST1926 as an interesting possible therapeutic agent in RMS, and in vivo preclinical studies utilizing this agent are currently underway.

Citation Format: Hussein Basma, Loai Dweik, Nadine Darwiche, Claudio Pisano, Raya Saab. The novel atypical retinoid ST1926 is active against rhabdomyosarcoma and induces cell cycle arrest in S and G2/M phases. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A39.
Abstract A44: Proprotein convertase furin in rhabdomyosarcoma progression: A potential target for pediatric sarcomas therapy?
Authors: Jaaks Patricia , D'Alessandro Valentina , Schäfer Beat W. , Bernasconi Michele
Published: May 2015

To improve therapies for embryonal pediatric tumors such as rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children, we have selected, by in vivo phage display, for peptides that bind to RMS with high specificity. We have shown that coupling of doxorubicin to RMS-P3, our lead RMS-targeting peptide, increases its therapeutic impact in a xenograft mouse model for RMS.

We have identified furin as potential target for RMS binding peptide RMS-P3. Furin is a member of the proprotein convertases (PC), a family of ten serine proteases, which convert inactive proproteins into their active form. We have found consistent expression of furin in a panel of RMS cell lines and in RMS biopsies at the mRNA level. To elucidate the contribution of furin to RMS growth we have generated a panel of RMS cell lines either overexpressing furin, or a specific intrinsic PC inhibitor called α1-PDX, as well as RMS cell lines were expression of furin has been stably reduced by shRNA. These cells have been tested for their growth, migration and invasion potential in vitro as well as for their growth in vivo as subcutaneous xenografts. The results suggest a direct correlation between furin activity and RMS cells migration and invasive properties in vitro as well as RMS tumor growth in vivo. Interestingly, alveolar RMS cells display a higher furin activity compared to embryonal RMS cells. Alveolar RMS cells growth in vivo cannot be further enhanced by furin overexpression, in contrast to embryonal RMS cells, suggesting a causal link between high furin activity and alveolar RMS malignant phenotype. Among the known furin substrates, which are processed and activated by furin, and involved in tumor growth, migration and invasion, we found a direct correlation between furin activity and IGFR1 activation.

Our results suggest that furin plays a relevant role in RMS progression through enhanced activation of the IGF1R pathway, among others, and that it might represent a viable target for therapeutic intervention in RMS. This warrants further studies in the development of novel therapeutic approaches for RMS based both on specific inhibition of its activity and on targeted drug delivery by furin targeting peptides.

Citation Format: Patricia Jaaks, Valentina D'Alessandro, Beat W. Schäfer, Michele Bernasconi.{Authors}. Proprotein convertase furin in rhabdomyosarcoma progression: A potential target for pediatric sarcomas therapy? [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A44.
Abstract A58: HMGA2 controls muscle stem cell activation and rhabdomyosarcoma progression
Authors: Li Zhizhong
Published: May 2015

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children and it shares significant features with proliferating muscle progenitor (myoblast). In an effort to profile mechanistic changes that might control myogenesis and/or induce RMS, a group of genes were identified that are highly and specifically expressed in myoblasts and RMS, but not quiescent muscle stem cells or differentiated myofibers. One of these genes, HMGA2, maintains myoblast and RMS cellular proliferation and survival. Hmga2 knockout mice exhibit impaired muscle development and reduced myoblast proliferation. Similarly, targeting HMGA2 expression by shRNAs inhibited RMS proliferation and increased apoptosis. This perturbation in proliferation can be explained by the finding that HMGA2 directly regulates RNA-binding protein IGF2BP2 in both myoblast and RMS. IGF2BP2 in turn binds to and controls the translation of a set of mRNAs, including NRas, which is frequently mutated in RMS and critical for tumor progression. These data demonstrate that HMGA2-IGF2BP2 axis functions as a conserved regulator of myoblast and RMS growth and may provide a novel target for future drug development to treat this childhood cancer.

References:

Li Z, et.al. Oncogenic NRAS, required for pathogenesis of embryonic rhabdomyosarcoma, relies upon the HMGA2-IGF2BP2 pathway. Cancer Res. 2013 May 15;73(10):3041-50.

Li Z, et,al. An HMGA2-IGF2BP2 axis regulates myoblast proliferation and myogenesis. Dev Cell. 2012 Dec 11;23(6):1176-88.

Note: This abstract was not presented at the conference.

Citation Format: Zhizhong Li. HMGA2 controls muscle stem cell activation and rhabdomyosarcoma progression. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A58.
Abstract A63: YB-1 is critical for stress granule assembly and protects cells from oxidative stress
Authors: Somasekharan Syam Prakash , Leprivier Gabriel , Evdokimova Valentina , EI-Naggar Amal , Hajee Shamil , Gleave Martin , Sorensen Poul HB
Published: May 2015

Stress granules (SGs) are highly conserved cytoplasmic ribonucleoprotein complexes that modulate gene expression and cellular homeostasis under prototypical stress forms. SG formation protects cells under stress conditions by protecting untranslated mRNAs until stress relief, and cells that are incapable of forming SGs are more vulnerable to diverse stressors compared to cells that are proficient at SG formation. The transcription and translation regulation factor Y-box binding protein 1 (YB-1) is recruited to SG, but its exact contribution to formation of these structures is not clear. Using several stress inducing agents, arsenite, H2O2, piperlongumine, thapsigargin, heat shock, curcumin and hypoxia we demonstrate that YB-1 co-localizes to SG along with G3BP, TIA-1 and poly(A)+ mRNA in various human cancer cell lines. YB-1 inactivation by siRNA knockdown dramatically reduces the efficiency of SG assembly in two sarcoma cell lines, U2OS and Rh-30 and a prostate cancer cell line DU-145, with high YB-1 expression. We also found that si-YB-1 cells with an inefficient stress granule formation were more sensitive to stress induced by arsenite, H2O2, or piperlongumine compared to control cells. YB-1 influences SG assembly via two distinct mechanisms. First, it acts as a scaffold protein to recruit mRNA and SG associated RNA-binding proteins into SGs. Second, YB-1 regulates the mRNA translation of the essential nucleator SG proteins, G3BP and TIA-1, thus controlling their availability during SG assembly under oxidative stress. Finally, in vivo, downregulation of YB-1 significantly affected the formation of stress granules in primary tumors generated in mice. Taken together, YB-1 is critical in SG formation and cell survival.

Citation Format: Syam Prakash Somasekharan, Gabriel Leprivier, Valentina Evdokimova, Amal EI-Naggar, Shamil Hajee, Martin Gleave, Poul HB Sorensen. YB-1 is critical for stress granule assembly and protects cells from oxidative stress. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A63.
Abstract A67: Canonical WNT/β;-catenin pathway activation suppresses embryonal rhabdomyosarcoma growth and self-renewal
Authors: Chen Eleanor , DeRan Michael , Grandinetti Katherine Brooke , Ignatius Myron , Clagg Ryan , McCarthy Karin , Lobbardi Riadh , Wu Xu , Langenau David
Published: May 2015

Embryonal rhabdomyosarcoma (ERMS) is a common pediatric malignancy of muscle with relapse being the major clinical challenge. Self-renewing tumor-propagating cells (TPCs) drive cancer relapse and are confined to a molecularly definable subset of ERMS cells. To identify drugs that suppress TPC function, a large-scale chemical screen comprising of ∼40,000 compounds including 47% FDA-approved drugs was completed, identifying GSK3-inhibitors as potent suppressors of ERMS growth through inducing terminal differentiation of TPCs into myosin-expressing cells. In support of GSK3 inhibitors functioning through activation of the canonical WNT pathway, recombinant WNT3A and a stabilized β-catenin enhanced differentiation and reduced self-renewal in human ERMS cell lines. Moreover, treatment of tumor-bearing zebrafish with a GSK3 inhibitor activated the WNT/β-catenin pathway, resulting in suppressed ERMS growth, depleted TPCs, and diminished self-renewal capacity in vivo. As canonical WNT signaling is essential for transition from muscle stem cell proliferation to myogenic differentiation during regeneration, our findings suggest that the same developmental pathways that regulate muscle stem cell self-renewal also contribute to tumorigenesis in ERMS. GSK3 inhibitors are being assessed for their efficacy in inhibiting growth as well as inducing differentiation of human ERMS in xenograft mouse models. Our work has identified the vital role of canonical WNT pathway in regulating differentiation and self-renewal of ERMS and demonstrated the effective application of small molecule inhibitors to target differentiation of TPCs in ERMS.

Citation Format: Eleanor Chen, Michael DeRan, Katherine Brooke Grandinetti, Myron Ignatius, Ryan Clagg, Karin McCarthy, Riadh Lobbardi, Xu Wu, David Langenau. Canonical WNT/β;-catenin pathway activation suppresses embryonal rhabdomyosarcoma growth and self-renewal. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A67.
Abstract A75: A new, microRNA-regulated, epigenetic tumor-promoting pathway in Ewing sarcoma
Authors: Parrish Janet K. , Sechler Marybeth , Jedlicka Paul
Published: May 2015

Ewing Sarcoma is an aggressive pediatric bone and soft tissue malignancy driven by transcription factor oncogenic fusions, of which EWS/Fli1 is the most common. Our studies of the role of microRNAs in EWS/Fli1-driven oncogenesis have uncovered a new tumor-promoting pathway in Ewing Sarcoma. Specifically, we have found that EWS/Fli1 downregulates miR-22, which in turn results in increased expression of the H3K9 histone demethylase, and miR-22 target, KDM3A. Overexpression of miR-22 and stable depletion of KDM3A each results in impaired clonogenic and anchorage-independent growth of Ewing Sarcoma cells. KDM3A depletion further results in impaired tumorigenesis in a xenograft model, upregulation of the repressive H3K9 methyl histone mark, and diminished expression of multiple oncogenes in Ewing Sarcoma. Our studies thus identify a new, potentially targetable, tumor-promoting pathway in Ewing Sarcoma, involving modulation of H3K9 histone methylation downstream of EWS/Fli1.

Citation Format: Janet K. Parrish, Marybeth Sechler, Paul Jedlicka. A new, microRNA-regulated, epigenetic tumor-promoting pathway in Ewing sarcoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A75.
Abstract B24: Inhibition of mTOR induces multidrug resistance in B-progenitor acute lymphocytic leukemia
Authors: Vo Thanh-Trang , Lu Mengrou , Nguyen Duc , Lui Brandon , Maylla Sharmila , Fruman David
Published: May 2015

In B-progenitor acute lymphocytic leukemia (B-ALL), the current chemotherapeutic regimen can effectively cure most patients. However, some patients like those with the Philadelphia chromosome (Ph+) often relapse. Many of these Ph+ and some Ph- B-ALL have elevated signaling through the PI3K/AKT/mTOR pathway. The cancer proliferation and survival driven by this pathway provides these cancers an advantage that likely contributes to survival after chemotherapy, resulting in a high rate of relapse. The goal of this project is to test inhibitors of the various components of the PI3K/AKT/mTOR pathway to determine how to combine them with current chemotherapy to enhance leukemia killing and prevent relapse. Our pilot studies using Annexin-V and PI staining revealed that upstream PI3K inhibition often sensitizes B-ALL cell lines to chemotherapy but, surprisingly, downstream mTOR inhibition induces multidrug resistance. Using a novel assay called BH3 profiling we have found that mTOR inhibition actually sensitizes cells to triggers of mitochondrial apoptosis but an unknown resistance mechanism reverses the effects of this sensitization. This resistance is observed when using rapamycin as well as active-site mTOR inhibitors (MLN-0128 and AZD8055). The degree of drug resistance upon mTOR inhibition varies with different chemotherapeutic agents. mTOR inhibition best protects cells from killing by methotrexate and is least protective when combined with daunorubicin. Future work will focus on identifying the mechanism of drug resistance induced by mTOR inhibition. Thus far, we have found that resistance does not correspond with the effects on cell cycle. Identifying and finding mechanisms of reversing this protective effect could potentially augment the effectiveness of inhibiting the PI3K/AKT/mTOR pathway. Our results will lead to a better understanding of how to best utilize PI3K pathway inhibitors in combination with standard chemotherapy as an option for high-risk B-ALL cases driven by oncogenic PI3K signaling.

Citation Format: Thanh-Trang Vo, Mengrou Lu, Duc Nguyen, Brandon Lui, Sharmila Maylla, David Fruman. Inhibition of mTOR induces multidrug resistance in B-progenitor acute lymphocytic leukemia. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B24.
Abstract B29: Increased vertebral marrow adiposity in long-term survivors of pediatric allogeneic hematopoietic stem cell transplant is associated with deficits in trabecular microarchitecture
Authors: Mostoufi-Moab Sogol , Sun Wenli , Magland Jeremy , Isaacoff Elizabeth , Bunin Nancy J. , Ginsberg Jill P. , Wehrli Felix , Shults Justine , Leonard Mary B.
Published: May 2015

Background: As treatment-related mortality following allogeneic hematopoietic stem-cell transplantation (alloHSCT) declines, a major unmet need is the identification and prevention of late effects. Long-term survivors of hematologic malignancies requiring alloHSCT show impaired bone density and structure with excess whole body adiposity (Mostoufi-Moab, JBMR, 2012). Marrow adipocytes share common mesenchymal stem cells (MSC) with bone-forming osteoblasts, with an inverse relation between MSC differentiation into osteoblasts or adipocytes. The impact of alloHSCT and total body irradiation (TBI) on marrow adipose tissue (MAT) and trabecular bone microarchitecture (TBA) has not been addressed.

Methods: Magnetic resonance spectroscopic imaging (MRSI) and high-resolution structural imaging were used to quantify vertebral MAT and distal tibia TBA on a 1.5 Tesla magnet. Twenty-five alloHSCT recipients with underlying diagnosis of acute leukemia, ages 12-24 years, were enrolled, a median of 11 years (range 5-19) after alloHSCT and TBI, and compared with age-, sex- and race-matched healthy controls.

Results: AlloHSCT survivors had lower height Z-scores (-1.39 ± 0.98 vs. -0.04 ± 0.98; p < 0.001), compared with controls, while BMI Z-scores did not differ. Overall, greater MAT was associated with lower bone volume fraction (BVF), R = -0.57, p < 0.001. AlloHSCT was associated with higher mean (± SD) vertebral fat fraction (59.0 ± 11.3 vs. 29.3 ± 9.9; p < 0.001) and trabecular deficits including lower bone volume fraction (β -0.01; 95% CI -0.12, -0.00; p=0.02) and evidence of abnormal microarchitecture [greater erosion (p=0.01) with a more rod like structure (p=0.02)], vs. controls. TBA deficits were more pronounced in female alloHSCT recipients. Growth hormone deficiency was not associated with MAT or bone deficits.

Conclusion: Survivors of childhood alloHSCT after TBI demonstrate marked increases in vertebral MAT combined with abnormal trabecular bone microarchitecture. Future studies are needed to determine the metabolic effects and fracture implications of excess MAT, and to identify therapies for improved bone accrual following childhood alloHSCT.

Citation Format: Sogol Mostoufi-Moab, Wenli Sun, Jeremy Magland, Elizabeth Isaacoff, Nancy J. Bunin, Jill P. Ginsberg, Felix Wehrli, Justine Shults, Mary B. Leonard. Increased vertebral marrow adiposity in long-term survivors of pediatric allogeneic hematopoietic stem cell transplant is associated with deficits in trabecular microarchitecture. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B29.
Abstract B39: IGF-IR regulation of osteoclastogenesis in neuroblastoma bone metastasis
Authors: Rivera-Pintado Chris A. , Shan Yufei , Golen Cynthia M. van
Published: May 2015

Neuroblastoma is a tumor that is responsible for 15% of cancer deaths in children and has a mortality rate greater than 90% percent upon metastasis to bone. Due to the high mortality rate and lack of effective treatment options, our laboratory is investigating potential new therapeutic targets in neuroblastoma bone metastases. Since, insulin-like growth factor I (IGF-I) production in the bone promotes neuroblastoma growth and survival, our hypothesis is that inhibiting IGF-I receptor (IGF-IR) will prevent metastasis of this tumor to bone. Furthermore, neuroblastoma with increased IGF-IR expression induces osteoclasts to differentiate, with the percentage of differentiated osteoclasts in vitro increasing to 30% in the presence of conditioned medium from high IGF-IR expressing cells. The addition of a monoclonal, neutralizing antibody to the IGF-IR decreases the percentage of mature osteoclasts formed by over 50%. We are testing the hypothesis that IGF-IR activation in neuroblastoma alters the levels of RANK, RANKL and OPG, proteins involved in osteoclast differentiation. This alteration in RANK, RANKL, and OPG may cause osteoclast differentiation and osteolysis. Neuroblastoma cells with high IGF-IR protein levels express low levels of the decoy receptor OPG, while some lines also express high levels of RANKL. Therefore, we are currently testing the effect of IGF-IR inhibition on RANKL and OPG levels and subsequent effect on osteolysis.

Citation Format: Chris A. Rivera-Pintado, Yufei Shan, Cynthia M. van Golen. IGF-IR regulation of osteoclastogenesis in neuroblastoma bone metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B39.
Abstract B43: Role of activated SHP2 in high-risk neuroblastoma pathogenesis
Authors: Zhu (Jane) shizhen , Neel Benjamin G. , Look A. Thomas
Published: May 2015

Neuroblastoma, an embryonic tumor of peripheral sympathetic nervous system (PSNS), accounts for 10% of all childhood cancer deaths. We recently developed a robust zebrafish model of neuroblastoma and demonstrated that activated ALK synergizes with MYCN by inhibiting a developmentally-timed apoptotic response that is otherwise induced by MYCN. Genomic studies show that PTPN11 (encoding SHP2) is the second most frequently mutated genes in high-risk neuroblastoma. We have now used our zebrafish model to ask whether mutationally activated SHP2 functions as an oncogene in neuroblastoma. We developed transgenic lines in which ptpn11E69K is overexpressed in the PSNS under control of the dopamine-beta-hydroxylase promoter. Interestingly, ptpn11E69Ksynergized with MYCN to accelerate the onset of neuroblastoma in the interrenal gland, the zebrafish analogue of the adrenal medulla. Tumors began to appear at 15 weeks in transgenic fish overexpressing MYCN alone, whereas latency was shortened to 7 weeks and the penetrance was increased more than four-fold in transgenic fish co-expressing MYCN and ptpn11E69K. Co-expression of ptpn11E69K and MYCN also induced ganglioneuroma in the sympathetic ganglia, an outcome that has not been observed in transgenic fish overexpressing MYCN and activated ALK. These results suggest that activated SHP2 can collaborate with MYCN in neuroblastoma tumorigenesis via mechanisms different from those of activated ALK. Thus, zebrafish appears to provide a robust model system for functional genomic analysis and for the investigation of the mechanisms and pathways underlying mutations identified in ongoing tumor resequencing studies.

Citation Format: (Jane) shizhen Zhu, Benjamin G. Neel, A. Thomas Look. Role of activated SHP2 in high-risk neuroblastoma pathogenesis. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B43.
Abstract B45: A novel therapeutic approach for neuroblastoma
Authors: Mokhtari Reza Bayat , Tsui Micky , Lotfi Shamim , Kumar Sushil , Baluch Narges , Islam Syed S. , Das Bikul , Yeger Herman
Published: May 2015

Neuroblastoma (NB), a tumor of the primitive neural crest, despite aggressive treatment regimens, portends a poor long-term survival for patients with advanced high stage NB. Here, we investigated the effects of targeting two families of critical regulatory molecules involved in cancer progression, histone deacetylases (HDACs) and carbonic anhydrases (CAs). HDACs regulate the expression and activity of various proteins involved in carcinogenesis and cancer progression, whereas carbonic anhydrases (CAs) function in tumor cell pH homeostasis and therein regulation of growth, survival, and metastasis. In this study we have used HDAC inhibitor (HDACi), pyridylmethyl-N-{4-[(2-aminophenyl)-carbamoyl]-benzyl}-carbamate (MS-275) and CA inhibitor acetazolamide (AZ). We report that MS-275, at nanomolar concentrations, significantly reduced the tumor initiating cell fraction (TIC) in NB cell lines in reference to NT2/D1, a teratocarcinoma cell line, exhibiting a stem cell like phenotype in-vitro. Stemness genes Oct-5, SOX2 and nanog, assessed by flow cytometry and western blot were found to be significantly down-regulated after MS-275 treatment. Overall, the tumor growth inhibitory effect of MS-275 was demonstrated by cytotoxicity assays, FACs analysis, and “In cell Western” assay. In-vivo treatment with MS-275 (20 mg/Kg) in human NB SH-SY5Y subcutaneous NOD/SCID xenograft model significantly reduced the tumor weight after 21 days treatment compared to the control (AZ 30%; MS-275 85%; AZ+MS-275 90%); (AZ p<0.05; MS-275 and MS-275+AZ p<0.0001). The efficacy of MS-275 was further enhanced by co-administration of AZ (40 mg/Kg) without causing morbidity in mice. Electron microscopy and H&E staining revealed higher numbers of apoptotic cells in MS-275 and AZ+MS-275 treated tumors. Upon re-implantation of tumor cells from primary xenografts in mice, the MS-275+AZ treated cells did not produce palpable tumors after two months whereas untreated cells produced large tumors. This significant reduction in initial tumorigenicity and subsequent abrogation suggests potential elimination of NB tumor initiating cells. Thus MS-275 combined with AZ shows promise as a potent novel anti-NB therapeutic strategy given their current clinical utility.

Citation Format: Reza Bayat Mokhtari, Sr., Micky Tsui, Sr., Shamim Lotfi, Sr., Sushil Kumar, Sr., Narges Baluch, Syed S. Islam, Bikul Das, Herman Yeger. A novel therapeutic approach for neuroblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B45.
Abstract B57: Modeling human metastatic neuroblastoma in immunodeficient mice
Authors: Bexell Daniel , Braekeveldt Noémie , Beckman Siv , Mohlin Sofie , Gisselsson David , Påhlman Sven
Published: May 2015

Neuroblastoma is a childhood tumor located in the sympathetic nervous system and most often found in the adrenal gland. Half of the patients have metastases already at diagnosis. There is a need for improved preclinical in vivo models of human high-stage neuroblastoma. Aims: 1) To establish relevant xenograft in vivo models for studying neuroblastoma orthotopic growth and metastatic growth in bone marrow, 2) to detect tumor growth by the two imaging modalities utilized in the clinic, i.e. magnetic resonance imaging (MRI) and I-123-metaiodobenzylguanidine (MIBG)-Single photon emission computed tomography (SPECT), and 3) to characterize orthotopic and bone marrow tumor growth at a pathohistological level. Methods: SK-N-Be2c and KCN-69 neuroblastoma cells were injected into adrenal gland of immunodeficient NSG mice to establish orthotopic tumors. SK-N-Be2c cells were injected directly into femur bone marrow of NSG mice to model bone marrow metastatic growth in a reproducible way. Tumor growth was monitored by MRI or by MIBG-SPECT. Histopathological assessment was performed on formalin-fixed paraffin-embedded tissue sections. Conclusion: We have established a model for orthotopic neuroblastoma growth and characterized the model by MRI and MIBG-SPECT. Orthotopic tumors grow infiltratively into surrounding tissues and resemble the histopathological hallmarks of patient neuroblastoma. We also describe a reproducible in vivo model for neuroblastoma bone marrow metastatic growth. The in vivo models will be important tools for studying mechanisms of neuroblastoma growth and for preclinical drug testing.

Citation Format: Daniel Bexell, Noémie Braekeveldt, Siv Beckman, Sofie Mohlin, David Gisselsson, Sven Påhlman. Modeling human metastatic neuroblastoma in immunodeficient mice. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B57.
Abstract B6: Epigenetic regulation of Hedgehog pathway transcriptional output by BET bromodomain proteins
Authors: Tang Yujie , Schubert Simone , Qi Jun , Nguyen Brian , Masoud Sabran , Vue Nujsaunusi , Balansay Brianna , Yu Furong , Atwood Scott X. , Whitson Ramon J. , Ponnuswami Anitha , Chen Spencer , Gholamin Sharareh , Pamelyn Woo J. , Monje-Diesseroth Michelle , Oh Sekyung , Lee Alex , Tang Jean Y. , Wechsler-Reya Rob , Oro Anthony E. , Bradner James E. , Cho Yoon-Jae
Published: May 2015

Aberrant activation of Hedgehog signaling drives oncogenesis in several types of cancer. As a result, there has been significant interest in developing therapeutic strategies targeting this pathway, most notably through inhibition of Smoothened. Though Smoothened inhibitors have shown efficacy in several cancer clinical trials, the initial enthusiasm for these inhibitors has been tempered by emergence of resistance and a priori resistance, often via mutation of Smoothened itself or through dysregulation of downstream components of the Hedgehog signaling axis. Here we reveal a strategy that overcomes these resistance mechanisms by targeting the far downstream transcriptional mediators of Hedgehog signaling through inhibition of the BET bromodomain protein, BRD4. We show that knockdown of BRD4 or treatment with the BET bromodomain inhibitor, JQ1, dramatically inhibits transcription of GLI1 and other Hedgehog target genes upon ligand-mediated or genetic activation of the Hedgehog pathway. We confirm the inhibitory effect of JQ1 occurs downstream of SMO and SUFU and verify by chromatin immunoprecipitation that Brd4 directly occupies the GLI1 and GLI2 promoters, with a substantial decrease in the engagement of these genomic sites upon treatment with JQ1. We observe a corresponding downregulation of genes associated with medulloblastoma-specific GLI1 binding sites upon exposure to JQ1, confirming the direct regulation of GLI1 by BET bromodomain proteins. Finally, using patient- and GEMM-derived cell lines of Hedgehog-driven cancer (basal cell carcinoma, medulloblastoma and ATRT), we show that JQ1 decreases Hh pathway output and proliferation, even in cell lines resistant to Smoothened inhibitors. These results expand the role of BET bromodomain inhibitors to targeting Hedgehog-driven cancers and highlight a strategy that overcomes the limitation of Hedgehog pathway inhibitors currently in clinical use.

Citation Format: Yujie Tang, Simone Schubert, Jun Qi, Brian Nguyen, Sabran Masoud, Nujsaunusi Vue, Brianna Balansay, Furong Yu, Scott X. Atwood, Ramon J. Whitson, Anitha Ponnuswami, Spencer Chen, Sharareh Gholamin, Woo J. Pamelyn, Michelle Monje-Diesseroth, Sekyung Oh, Alex Lee, Jean Y. Tang, Rob Wechsler-Reya, Anthony E. Oro, James E. Bradner, Yoon-Jae Cho. Epigenetic regulation of Hedgehog pathway transcriptional output by BET bromodomain proteins. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B6.
Abstract IA05: Targeting the oxidative stress pathway in rhabdomyosarcoma
Authors: Dyer Michael A.
Published: May 2015

Rhabdomyosarcoma is a soft-tissue sarcoma with molecular and cellular features of developing skeletal muscle. Histologically, there are two major subtypes of rhabdomyosarcoma, embryonal and alveolar, which have distinct clinical, molecular, and genetic features. Patients with resected localized disease are highly curable, but patients with recurrent, metastatic or large unresectable tumors have a poor clinical outcome. In this study, we performed whole-genome sequencing, exome sequencing, RNA-sequencing and DNA methylation profiling of embryonal and alveolar rhabdomyosarcomas. The embryonal tumors had more structural and copy number variations than did alveolar tumors and those lesions result from the accumulation of chromosomal lesions over time. Mutations in the RAS/NF1 pathway were significantly associated with intermediate- and high-risk embryonal rhabdomyosarcoma. In contrast, alveolar rhabdomyosarcoma had fewer genetic lesions overall and there were no known cancer consensus genes that were recurrently mutated other than the PAX3/7-FOXO1translocation that is a hallmark of alveolar rhabdomyosarcoma. DNA methylation profiling and RNA-seq analysis showed that embryonal and alveolar rhabdomyosarcomas are distinct and the alveolar tumors more closely resemble normal myoblasts and myotubes. To identify novel therapeutics for embryonal rhabdomyosarcomas, we developed and characterized 6 orthotopic xenografts of tumors in our discovery cohort. High throughput screening of primary cultures derived from those xenografts identified oxidative stress as a pathway of therapeutic relevance for embryonal rhabdomyosarcoma.

Citation Format: Michael A. Dyer. Targeting the oxidative stress pathway in rhabdomyosarcoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr IA05.
Abstract IA07: Genetic predispositions to pediatric cancers
Authors: Loh Mignon L.
Published: May 2015

Fortunately, childhood cancer remains a rare entity in the United States, with only 13,500 new cancers diagnosed per year in patients under the age of 19 years. However, an important component of the workup for the child who presents with cancer is obtaining a detailed family history of malignancy, which may provide clues to the frequently asked question posed by parents about “How did this happen to us?” Correctly identifying families who suffer from cancer predisposition syndromes provides critically important information for affected family members with respect to future prevention and screening. In addition, certain congenital syndromes are associated with an increased risk of malignancy and the altered genes identified in these syndromes have provided important clues about the pathogenesis of human cancer and cellular functions, which have also provided opportunities to identify new therapeutic approaches. This education session will provide a broad overview of the most common familial cancer risk syndromes that practicing oncologists should be familiar with as well as the types of cancers that most frequently occur in children with common congenital syndromes. In addition, emerging targeted therapeutic options will be discussed, where relevant.

Citation Format: Mignon L. Loh. Genetic predispositions to pediatric cancers. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr IA07.
Abstract IA08: Ataxia-telangiectasia: Broad implications from the study of a rare disease
Authors: Kastan Michael B.
Published: May 2015

DNA damage signaling pathways are critical mediators of both tumor development and tumor responses to chemotherapy and radiation therapy. Significant progress has been made in recent years in elucidating the molecular controls of cellular responses to DNA damage in mammalian cells. Much of what we have learned about damage signaling pathways has come from the study of human diseases, particularly cancer predisposition syndromes. Ataxia-Telangiectasia (A-T) is a pleiotropic disorder with multiple phenotypic abnormalities, including progressive neurodegeneration, immunodeficiencies, cancer predisposition, insulin resistance, telangiectasia development, infertility, and extreme radiosensitivity. ATM, the gene mutated in A-T, is a central mediator of responses to DNA double strand breaks in cells. Once activated, ATM phosphorylates numerous substrates in the cell that modulate the cell's response to the DNA damage. Though ATM clearly plays a central role in mediating cellular responses to DNA breakage, some of the clinical abnormalities in A-T are difficult to attribute directly to alterations in DNA damage signaling. The broad-based symptoms in A-T and recently acquired data suggest that ATM may have roles that extend beyond its regulation of DNA damage responses. In particular, ATM appears to affect insulin signaling pathways and evidence has been generated supporting a direct role for ATM in mitochondrial function. These new insights suggest that Ataxia-Telangiectasia should be considered, at least in part, as a mitochondrial dysfunction disease and provide links between cancer-related DNA damage signaling and more general metabolic signaling pathways. Some of these new insights are also providing opportunities for considerations of novel ways to modulate ATM function for clinical benefit.

Citation Format: Michael B. Kastan. Ataxia-telangiectasia: Broad implications from the study of a rare disease. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr IA08.
Abstract IA11: The St. Jude Children's Research Hospital - Washington University Pediatric Cancer Genome Project: Lessons learned
Authors: Downing James R.
Published: May 2015

In January of 2010, St. Jude Children's Research Hospital and The Genome Institute at the Washington University announced the launch of the Pediatric Cancer Genome Project (PCGP), a three year, $65 million privately funded initiative. The stated goal of this effort was to obtain 30-fold haploid coverage of the whole genome of 600 pediatric tumors and matched non-tumor germ line DNA samples (1200 total genomes), and to analyze these data in order to define the landscape of somatic mutations that underlie the major subtypes of pediatric leukemia, brain tumors, and solid malignancies. The initial phase of this project was completed in February of this year with over 700 pediatric cancers analyzed (1400 genomes). This effort has produced fundamental insights into each of the pediatric cancer subtypes sequenced. Not only has the data defined the spectrum of mutations that underlying specific pediatric cancers, but for some of the diseases analyzed, we have identified new prognostic markers and/or therapeutic targets. The effort has led to the generation of an incredibly rich data source that should serve the scientific community for years to come.

Based on the success of PCGP, we have begun a $30 million second phase of the project (PCGP Phase II) that will be completed in a two year timeframe. In this second phase, we will focus not only on discovery science, but also on the establishing the technologies, analytical tools, and medical interface needed to move genome-wide sequence analyses into the diagnostic work up of pediatric cancer patients. In this talk, I will present an overview of this project and highlight some of the important results that have emerged.

Citation Format: James R. Downing. The St. Jude Children's Research Hospital - Washington University Pediatric Cancer Genome Project: Lessons learned. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr IA11.
Abstract IA18: Mapping cancer origins
Authors: Gilbertson Richard J.
Published: May 2015

Histologically similar cancers respond differently to treatment. Consequently, significant populations of cancer patients continue to suffer morbidity and mortality while others with apparently similar tumors are cured. Understanding the biology that drives this heterogeneity is crucial if we are to develop effective treatments for all patients. Advanced genomic technologies have enabled us to divide cancer patients into distinct subgroups, often with different prognoses. However unmasking the mechanisms that generate these molecular subgroups has proven difficult, since their defining genetic alterations are often numerous, and the cellular origins of most cancers remain unknown. This talk will describe a series of recent and ongoing studies in which cross-species genomics approaches have been used to define the cellular and molecular origins of subgroups of brain tumors. By mapping regional and developmental patterns of human brain tumor subgroup gene expression in the developing mouse nervous system, it has been possible to identify variants of normal neural stem cells that share remarkably similar transcriptomes. These similarities in transcriptome reveal candidate cells of origin with a biologic ‘groundstate’ that is highly susceptible to transformation into the corresponding tumor type. Introduction of gene mutations into transcriptome-matched, but not other, normal mouse NSCs generated accurate tumor models of the corresponding human brain tumor subgroup. These models can then be used in high-throughput drug screens to identify subgroup specific treatments.

Citation Format: Richard J. Gilbertson. Mapping cancer origins. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr IA18.
Abstract IA23: The genomic landscape of acute lymphoblastic leukemia
Authors: Mullighan Charles
Published: May 2015

Acute lymphoblastic leukemia (ALL) is the commonest childhood tumor and a leading cause of cancer related death in young people. The last decade has witnessed intense activity in the field of ALL genomics, initially with microarrays and more recently with next generation sequencing, with the goal of comprehensively identifying all genetic alterations contributing to leukemogenesis, treatment failure and relapse. These studies have defined new entities of ALL, and have shown that each ALL subtype is typically defined by constellations of recurring chromosomal alterations and sequence mutations that target key cellular pathways including lymphoid maturation, cellular proliferation, tumor suppression, and chromatin modification. Genomic profiling has also identified genetic alterations that have clear implications for leukemia diagnosis and therapy in several subtypes of high-risk leukemia, including early T-cell precursor ALL, hypodiploid ALL, and BCR-ABL1-like ALL. Several genetic alterations are associated with an increased risk of leukemia relapse, including IKZF1, CREBBP, and NT5C2. Moreover, studies interrogating germline genetic variation have identified common variants associated with leukemia susceptibility, including risk of specific subtypes of ALL and ALL in different ethnic groups, and inherited mutations in familial ALL. Ongoing efforts are completing the genomic characterization of the spectrum of ALL cases, dissecting the genetic basis of clonal heterogeneity of ALL, and expanding these studies into integrated analysis of structural variation with the leukemia epigenome and transcriptome.

Citation Format: Charles Mullighan. The genomic landscape of acute lymphoblastic leukemia. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr IA23.
Abstract PR01: H-RasG12V overexpression in the central nervous system leads to expansion of oligodendrocyte precursor cells and neural crest cells
Authors: Distel Martin , Traver David
Published: May 2015

Somatic mutations in Ras proto-oncogenes have been found in a large number of different cancers. In addition, germline mutations in the H-Ras gene have been shown to be the causative genetic alteration underlying Costello Syndrome (CS). Costello Syndrome belongs to the large group of Ras/MAPK pathway diseases commonly termed Rasopathies. CS patients exhibit craniofacial and cardiac abnormalities, mental retardation and are prone to develop cancers including neural crest derived neoplasias.

Since Costello Syndrome is a rare disease, the effects of H-RasG12V expression on the development of the central nervous system remain largely uncharacterized. Towards this goal, we have established a zebrafish model suitable for live imaging and cost-effective drug screening. Using the Gal4/UAS system we have enforced expression of H-RasG12V in the central nervous system starting at early neurulation stages. H-RasG12V expressing embryos develop hyperplasia of the forebrain and the spinal cord and show an outgrowth in the dorsal tail region around 3 days post fertilization (dpf). In situ hybridisation revealed an increase in oligodendrocyte precursor cells, similar to what has been reported for zebrafish neurofibromin 1 mutants. In addition, cells expressing the neural crest markers Sox10 and FoxD3 accumulate lateral to the neural tube and notochord. Time-lapse imaging revealed that H-RasG12V expressing cells indeed migrate out of the spinal cord. This migration was ectopic, occuring several hours after normal neural crest migration. Furthermore, coinciding with the accumulation of neural crest like cells around the neural tube, the intersomitic vasculature hyperbranches to form new blood vessels towards domains of H-RasG12V expressing cells.

Taking advantage of the early onset and obvious phenotypes in our H-RasG12V overexpression model we performed a pilot drug screen to identify potential therapeutic compounds for Costello Syndrome. We found the Mek1/Mek2 inhibitor PD98059 successfully inhibited hyperplasia of the forebrain and the spinal cord, with normal numbers of oligodendrocyte precursor cells and neural crest cells. Thus, this zebrafish model will be a valuable tool to further investigate the mechanisms underlying CNS- abnormalities of Costello Syndrome patients, including the formation of neural crest derived neoplasias and will be useful to identify therapies against this disease.

This abstract is also presented as Poster A3.

Citation Format: Martin Distel, David Traver. H-RasG12V overexpression in the central nervous system leads to expansion of oligodendrocyte precursor cells and neural crest cells. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr PR01.