Abstract 2537: Targeting chromosomal passenger complex by disruption of INCENP function inhibits tumor progression in neuroblastoma

Chromosomal passenger complex (CPC), which is composed of Aurora B and Survivin, INCENP and Borealin, regulates crucial mitotic events including chromosome alignment, segregation and cytokinesis during the mitosis. Disruption of CPC function by Aurora B and Survivin inhibition has been demonstrated to be effective at killing tumor cells and show promising results in many different cancer types including neuroblastoma (NB). However, chemical inhibition of either Aurora B or Survivin is unable to target CPC specifically due to off-target effects of Aurora B inhibitors on the other kinases and antiapoptotic activities of Survivin independent of this complex. In a chromatin-focused siRNA screen, we found that NB cells were particularly vulnerable to the silencing of INCENP, a gene encoding a key scaffolding and regulatory component of the CPC. In this study, we found that INCENP was highly expressed in NB cells and its expression levels were decreased upon Retinoic Acid (RA)-induced NB cell differentiation. Genetic silencing of INCENP reduced the growth of both MYCN single copy and MYCN amplified NB cell lines in vitro and led to significant decreases in NB xenograft growth and increases in murine survival in vivo. Elevated levels of INCENP were significantly associated with poor prognosis in primary NB tumors whereas low INCENP expression levels were predictive of better outcomes. Mechanistically, we found that INCENP depletion suppressed NB cell growth by inducing massive polyploidization, mitotic arrest, senescence and cell death (apoptosis). We also observed that in the majority of NB cell lines tested in vitro, cell death represented the primary cell fate after INCENP silencing due to a strong induction of DNA damage response and activation of the p53-p21 axis. Therefore, targeting INCENP phenocopies treatment with Aurora B inhibitor, providing a novel strategy to disrupt the activity of CPC and inhibit tumor progression in NB.

Citation Format: Ming Sun, Veronica Veschi, Norris Lam, Sukriti Bagchi, Man Xu, Arnulfo Mendoza, Zhihui Liu, Carol J. Thiele. Targeting chromosomal passenger complex by disruption of INCENP function inhibits tumor progression in neuroblastoma [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 2537.

Spatial differences in ambient coarse and fine particles in the Monterrey metropolitan area, Mexico: Implications for source contribution

The ambient air of the Monterrey Metropolitan Area (MMA) in Mexico frequently exhibits high levels of PM₁₀ and PM_2.5. However, no information exists on the chemical composition of coarse particles (PM_c = PM₁₀ - PM_2.5). A monitoring campaign was conducted during the summer of 2015, during which 24-hr average PM₁₀ and PM_2.5 samples were collected using high-volume filter-based instruments to chemically characterize the fine and coarse fractions of the PM. The collected samples were analyzed for anions (Cl^-, NO₃^-, SO₄^2-), cations (Na⁺, NH₄⁺, K⁺), organic carbon (OC), elemental carbon (EC), and 35 trace elements (Al to Pb). During the campaign, the average PM_2.5 concentrations did not showed significance differences among sampling sites, whereas the average PM_c concentrations did. In addition, the PM_c accounted for 75% to 90% of the PM₁₀ across the MMA. The average contribution of the main chemical species to the total mass indicated that geological material including Ca, Fe, Si, and Al (45%) and sulfates (11%) were the principal components of PM_c, whereas sulfates (54%) and organic matter (30%) were the principal components of PM_2.5. The OC-to-EC ratio for PM_c ranged from 4.4 to 13, whereas that for PM_2.5 ranged from 3.97 to 6.08. The estimated contribution of Secondary Organic Aerosol (SOA) to the total mass of organic aerosol in PM_2.5 was estimated to be around 70-80%; for PM_c, the contribution was lower (20-50%). The enrichment factors (EF) for most of the trace elements exhibited high values for PM_2.5 (EF: 10-1000) and low values for PM_c (EF: 1-10). Given the high contribution of crustal elements and the high values of EFs, PM_c is heavily influenced by soil resuspension and PM_2.5 by anthropogenic sources. Finally, the airborne particles found in the eastern region of the MMA were chemically distinguishable from those in its western region. Implications: Concentration and chemical composition patterns of fine and coarse particles can vary significantly across the MMA. Public policy solutions have to be built based on these observations. There is clear evidence that the spatial variations in the MMA's coarse fractions are influenced by clearly recognizable primary emission sources, while fine particles exhibit a homogeneous concentration field and a clear spatial pattern of increasing secondary contributions. Important reductions in the coarse fraction can come from primary particles' emission controls; for fine particles, control of gaseous precursors-particularly sulfur-containing species and organic compounds-should be considered.

Productive performance and digestive response of dairy cows fed different diets combining a total mixed ration and fresh forage

The purpose of this experiment was to determine the effects of feeding increasing levels of fresh forage (FF) as a proportion of total dry matter intake (DMI) on nutrient intake, rumen digestion, nutrient utilization, and productive performance of total mixed ration (TMR)-fed cows. Twelve dairy cows (90 ± 22 d in milk, 523 ± 88 kg of body weight, 7,908 ± 719 kg of milk production in the previous lactation) were housed in individual tiestalls and assigned to treatments according to a 3 × 3 Latin square design replicated 4 times. Treatments were 100% TMR (T100), 75% TMR plus 25% FF (T75), and 50% TMR plus 50% FF (T50). The experiment lasted 60 d, divided into 3 periods of 20 d each; the first 12 d of each period were used for diet adaptation and the last 8 d for data collection. The TMR (18.1% crude protein, 24.6% acid detergent fiber) and FF (Lolium multiflorum; 15.1% crude protein, 24.1% acid detergent fiber) were prepared and cut daily and offered to each cow individually. The highest DMI was reached in T100 and T75, which was reflected in greater intake of the different nutrients than T50. No differences were detected in the apparent total digestibility of the nutrients, mean ruminal pH, and total volatile fatty acid concentrations among treatments. Cows in T50 resulted in the lowest ruminal N-NH₃ concentration and the lowest microbial N flow to the duodenum. Milk yield was 8.5% higher from cows in T100 and T75 compared with T50, but we observed no differences for milk fat or milk protein yield among treatments. Milk fat of cows fed T50 had 8% more unsaturated fatty acids (FA) than that of cows fed T100, mostly because of a higher content of monounsaturated FA. Additionally, cows in T50 had a higher concentration of linoleic acid, vaccenic acid, and rumenic acid than T100. Meanwhile, the concentration of linoleic acid and vaccenic acid in cows fed T75 was higher than T100. The milk fat of the cows fed T50 and T75 had a lower n-6:n-3 ratio than T100. We concluded that including up to 29% of FF in the total DMI in combination with a TMR did not affect the intake or digestion of nutrients or the productive response in dairy cows and resulted in a higher concentration of desirable FA from a consumer's perspective.

Abstract B16: Evaluation of LDH inhibition as a treatment strategy in Ewing sarcoma

Long-term outcomes for patients with relapsed, recurrent, or metastatic Ewing sarcoma (ES) remain poor despite advances in multimodal chemotherapy and local tumor control. The discovery of new targets and novel therapies is therefore critical to improving care for these patients. Recent insights into the metabolic landscape of ES have revealed that the EWS/FLI1 fusion oncoprotein regulates metabolic pathways in this disease, including shifting glucose consumption away from oxidative metabolism and towards glycolysis, a pathway that relies on LDH. Targeting this increased dependence on glycolysis presents an opportunity to inhibit the growth of ES cells through a novel therapeutic approach, while potentially limiting the toxicity delivered to normal cells. We therefore sought to evaluate the activity of NCGC-737 and NCGC-006, two novel LDHA/B inhibitors identified and validated as part of the Experimental Therapeutics Program of the National Cancer Institute (NCI-NExT), in ES.

For in vitro studies, proliferation of ES cells lines was assessed after inhibition of LDHA/B by each agent using IncuCyte and MTS assays. Protein expression of phospho- and total LDH was evaluated by Western blot. LDH activity was assessed using the pyruvate-dependent oxidation of NADH. NAD/NADH levels were determined using NAD/NADH-Glo. Analysis of glycolytic profiles was performed using the Agilent Extracellular Flux Analyzer. For in vivo studies, female SCID mice underwent orthotopic injection of ES cells from established cell lines. When tumors reached a desired size, mice were randomized and then treated on a variety of dosing schedules. Toxicity assessments included evaluation of overall appearance, weekly weights, blood sampling, and full necropsies on selected mice. Tumors were measured twice per week for assessment of efficacy. Tumors were harvested at midpoints and at study endpoint for assessments of drug level, target inhibition, and biology.

ES cell lines displayed varying sensitivity to NCGC-737 and NCGC-006, with IC-50 values ranging from 50 nM to 500 nM. While protein expression of phospho-LDH, total LDH-A, and total LDH-B were not correlated with sensitivity to either agent, glycolytic profiles were predictive of sensitivity. Cell lines that underwent a greater reduction in glycolytic capacity (the change in ECAR measured before and after oligomycin treatment) after LDHA/B inhibition experienced a greater antiproliferative effect, while cell lines that were able to maintain glycolytic capacity despite LDHA/B inhibition exhibited less of an effect on growth. In vivo studies to describe the toxicity of these agents demonstrated that hemolysis was the primary dose-limiting toxicity, and was dose dependent. Additional toxicity studies of specific tissues are ongoing and will be reported. Preliminary in vivo studies to optimize dosing regimen established that compared to oral dosing, intravenous dosing resulted in higher and more consistent tumor drug levels and improved target inhibition, with up to 93% of intratumoral LDH activity inhibited. Efficacy studies are ongoing and will be reported.

Preclinical data suggest that inhibition of LDHA/B may represent a potentially novel therapeutic strategy in the treatment of ES.

Citation Format: Christine M. Heske, Anna E. Gibson, Josh T. Baumgart, Choh Yeung, Sameer H. Issaq, A Mendoza, Michelle S. Johnson, Guiseppe L. Squadrito, Lillian Culp, Victor M. Darley-Usmar, Len M. Neckers. Evaluation of LDH inhibition as a treatment strategy in Ewing sarcoma [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr B16.

Abstract 5211: Dual E-selectin and CXCR4 inhibition reduces tumor growth and metastatic progression in an orthotopic model of osteosarcoma

Osteosarcoma is the most common bone cancer in children and young adults and has a strong propensity to develop lung metastases. E-selectin is known to be involved in the focal adhesion of tumor cells to cytokine exposed endothelial cells and we postulated may play a central role in osteosarcoma progression. Previously we identified that SDF-1, the main ligand for CXCR4, was upregulated in the pre-metastatic niche (Kaplan et al Nature 2005). Many tumor cells express CXCR4 and may use this signaling pathway to direct disseminated tumor cells to pre- and early metastatic sites in the lung. Based on these findings we examined human osteosarcoma cell lines and primary patient derived xenografts (PDXs) for the expression of CXCR4 and E-selectin ligands by flow cytometry. We found robust expression of these ligands in the majority of both the human osteosarcoma cell lines and PDXs examined. We therefore, investigated the impact of targeting these two axes on metastatic progression of orthotopic osteosarcoma using a small molecule, glycomimetic compound with dual inhibitory activity against E-selectin and CXCR4, GMI-1359. Five days post paratibial injection the HOS cell line, female NMRI-nu mice (n=12/group) were treated with saline; GMI-1359 alone (40 mg/kg IP BID x 25 days); doxorubicin (DOX) alone (5 mg/kg IV days 5, 15 and 25), or the combination of GMI-1359 and DOX. All treatments were well tolerated. The % tumor volume in treatment/control on day 27 of mice treated with GMI-1359, DOX or the combination was 35.5, 36.7 and 32.5, respectively. At study conclusion the incidence of lung metastases was approximately 60% and 50% in mice treated with saline or DOX and 15% in mice treated with GMI-1369 alone or in combination with DOX. Moreover, the extent of ectopic bone formation and/or osteolytic lesions was lower in mice treated with GMI-1359 compared to saline and DOX. These results indicate that the E-selectin and CXCR4 axes are important for the progression of osteosarcoma, and further, that inhibition of these two pro-tumor growth components by GMI-1359 has a therapeutic advantage over chemotherapy alone. Furthermore, studies in the adjuvant setting can provide proof of concept of utility of targeting CXCR4 and E- selectin ligands in the metastatic niche as a therapeutic strategy to limit metastatic progression in high risk patients.

Citation Format: Wei Ju, Choh L. Yeung, Arnulfo Mendoza, Meera Murgai, Sabina Kaczanowska, Jennifer Zhu, Shil Patel, David A. Stewart, William E. Fogler, John L. Magnani, Rosandra N. Kaplan. Dual E-selectin and CXCR4 inhibition reduces tumor growth and metastatic progression in an orthotopic model of osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5211.

Metabolomics uncovers a link between inositol metabolism and osteosarcoma metastasis

Cancer development and progression are characterized by complex molecular events. The acquisition of these events is primarily believed to result from alterations in gene and protein expression/function. Recent studies have also suggested the role of metabolic alterations, or "metabolic reprogramming," that may similarly contribute to these events. Indeed, our previous investigations in osteosarcoma (OS) identified metabolic changes uniquely linked to metastasis. Based on those findings, here we sought to build a more detailed understanding of the specific alterations in metabolites or metabolic pathways that may be responsible for the observed metastasis-associated metabolic alterations, suggested by gene expression data. This was pursued using a combination of high-throughput liquid- and gas-chromatography-based mass spectrometry (LC/MS and GC/MS) for a global metabolic profiling/subtraction of four pairs of high/low metastatic OS cell lines. By comparing the identity and level of the metabolites between high/low metastatic cells, several metabolic pathways were identified to be differentially activated, such as arginine, glutathione, inositol and fatty acid metabolic pathways. To further interrogate these results, we investigated the effects of inositol pathway dysregulation, through the exposure of metastatic OS cells to IP6 (inositol hexaphosphate). Although IP6 exposures had modest to minimal effects on cell proliferation, we observed reduced cellular glycolysis, down-regulation of PI3K/Akt signaling and suppression of OS metastatic progression. Collectively these data supported further investigation of metabolic sensitivities as anti-metastatic strategies in a clinical setting as well as investigation of altered metabolomics associated with metastatic progression.

STA-8666, a novel HSP90 inhibitor/SN-38 drug conjugate, causes complete tumor regression in preclinical mouse models of pediatric sarcoma

Long-term survival in patients with metastatic, relapsed, or recurrent Ewing sarcoma and rhabdomyosarcoma is dismal. Irinotecan, a topoisomerase 1 inhibitor, has activity in these sarcomas, but due to poor bioavailability of its active metabolite (SN-38) has had limited clinical efficacy. In this study we have evaluated the efficacy and toxicity of STA-8666, a novel drug conjugate which uses an HSP90 inhibitor to facilitate intracellular, tumor-targeted delivery of the topoisomerase 1 inhibitor SN-38, thus preferentially delivering and concentrating SN-38 within tumor tissue. We present in vivo evidence from mouse xenograft models that STA-8666 results in more persistent inhibition of topoisomerase 1 and prolonged DNA damage compared to irinotecan. This translates into superior antitumor efficacy and survival in multiple aggressive models of both diseases in mouse xenografts, as well as in an irinotecan-resistant model of pediatric osteosarcoma, demonstrated by dramatic tumor shrinkage, durable remission and prolonged complete regressions following short-term treatment, compared to conventional irinotecan. Gene expression analysis performed on xenograft tumors treated with either irinotecan or STA-8666 showed that STA-8666 affected expression of DNA damage and repair genes more robustly than irinotecan. These results suggest that STA-8666 may be a promising new agent for patients with pediatric-type sarcoma.

Positively selected enhancer elements endow osteosarcoma cells with metastatic competence

Metastasis results from a complex set of traits acquired by tumor cells, distinct from those necessary for tumorigenesis. Here, we investigate the contribution of enhancer elements to the metastatic phenotype of osteosarcoma. Through epigenomic profiling, we identify substantial differences in enhancer activity between primary and metastatic human tumors and between near isogenic pairs of highly lung metastatic and nonmetastatic osteosarcoma cell lines. We term these regions metastatic variant enhancer loci (Met-VELs). Met-VELs drive coordinated waves of gene expression during metastatic colonization of the lung. Met-VELs cluster nonrandomly in the genome, indicating that activity of these enhancers and expression of their associated gene targets are positively selected. As evidence of this causal association, osteosarcoma lung metastasis is inhibited by global interruptions of Met-VEL-associated gene expression via pharmacologic BET inhibition, by knockdown of AP-1 transcription factors that occupy Met-VELs, and by knockdown or functional inhibition of individual genes activated by Met-VELs, such as that encoding coagulation factor III/tissue factor (F3). We further show that genetic deletion of a single Met-VEL at the F3 locus blocks metastatic cell outgrowth in the lung. These findings indicate that Met-VELs and the genes they regulate play a functional role in metastasis and may be suitable targets for antimetastatic therapies.

Abstract IA04: Targeting the expression of EWS-FLI1

Post-translational modifications (PTMs) of transcription factors represent potential therapeutic targets for a variety of diseases, including cancer. In the majority of cases of the bone and soft tissue tumor Ewing sarcoma (ES), a chromosomal translocation, t(11:22), results in expression of the fusion transcription factor EWS-FLI1. Few PTMs of EWS-FLI1 have been identified. Using functional genetic methods and mass spectrometry analysis, we have identified a phosphorylated serine residue in the FLI1 domain of EWS-FLI1 that regulates the stability of the EWS-FLI1 oncoprotein. Loss of phosphorylation of this serine residue triggers ubiquitination and proteasomal degradation of EWS-FLI1, and apoptotic cell death. Xenograft studies suggest this post-translational modification of EWS-FLI1 can be targeted in vivo and that this inhibits ES tumor growth.

Citation Format: Nirmalya Sen, Katelyn Ludwig, Guillermo O. Rangel-Rivera, Suntae Kim, Konrad Huppi, Lisa Jenkins, Jennifer E. Dwyer, Shelley Hoover, Lee Helman, Mark Simpson, Arnulfo Mendoza, Amanda B. Hummon, Natasha J. Caplen. Targeting the expression of EWS-FLI1 [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr IA04.

Abstract LB-B01: The anti-platelet-derived growth factor receptor α antibody olaratumab (Lartruvo) increases overall survival in metastatic mouse models of human osteosarcoma

Platelet-derived growth factor receptor alpha (PDGFRα) is implicated in several types of adult and pediatric malignancies, where its aberrant expression and/or activation in tumor cells and/or tumor-associated stromal cells promote primary tumor growth and metastasis. Therefore, PDGFRα signaling may regulate disease progression via autocrine and paracrine modes of activation and facilitating crosstalk between the tumor and stroma. Olaratumab is a fully humanized monoclonal antibody that selectively binds human PDGFRα and blocks signaling initiated by ligand binding. We evaluated the efficacy of olaratumab and 1E10, a high affinity anti-mouse PDGFRα antibody in preclinical metastatic models of human osteosarcoma. A metastatic derivative of the PDGFRα-positive human osteosarcoma cell line HuO9 (HuO9-H3) was implanted in the gastrocnemius of mice. Olaratumab/1E10 was administered twice weekly once tumors grew to ~ 150 mm3. When tumors reached an average of volume of 1600 mm3, tumor-bearing limbs were amputated and four separate treatment cohorts were evaluated. These cohorts were as follows: (1) continuous IgG control antibody treatment, (2) continuous olaratumab/1E10 treatment prior to and after amputation, (3) olaratumab/1E10 treatment pre-amputation followed by IgG administration post-amputation, and (4) IgG treatment pre-amputation followed by olaratumab treatment post-amputation. A statistically significant and prolonged overall survival (OS) benefit (p<0.001) was observed in the continuous olaratumab/1E10 treatment group only, and correlated with a reduced tumor burden in the lung as determined by histologic evaluation. An olaratumab/1E10-dependent statistically significant OS benefit (p<0.001) was also observed in the HuO9-H3 and PDGFRα/PDGFRβ-positive MG63.3 human osteosarcoma cell lines introduced via tail vein injection. Interestingly, histologic review shows reduced tumor burden in the lung and lung pleura/mediastinum of these models. Mouse-specific bright field in situ hybridization (BRISH) showed increased expression of PDGFRA, PDGFRB, associated ligands, and VEGFA in the murine lung stroma prior to histologically apparent metastases. These data indicate that olaratumab/1E10-mediated PDGFRα blockade significantly increases OS in preclinical mouse models of human osteosarcoma and suggest a novel role for the PDGFRα pathway in the pathogenesis of metastatic osteosarcoma lung lesions.

Citation Format: Amy K. LeBlanc, Gerard J. Oakley, Caitlin D. Lowery, Arnulfo Mendoza, Ling Ren, Timothy Holzer, Kelly Credille, Cynthia Winings, Amanda Estelle, Mia Chen, Patrick Finnegan, Wayne Blosser, Andrew Schade, Symantha Melemed, Louis F. Stancato. The anti-platelet-derived growth factor receptor α antibody olaratumab (Lartruvo) increases overall survival in metastatic mouse models of human osteosarcoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B01.

Matrix Screen Identifies Synergistic Combination of PARP Inhibitors and Nicotinamide Phosphoribosyltransferase (NAMPT) Inhibitors in Ewing Sarcoma

Purpose: Although many cancers are showing remarkable responses to targeted therapies, pediatric sarcomas, including Ewing sarcoma, remain recalcitrant. To broaden the therapeutic landscape, we explored the in vitro response of Ewing sarcoma cell lines against a large collection of investigational and approved drugs to identify candidate combinations.Experimental Design: Drugs displaying activity as single agents were evaluated in combinatorial (matrix) format to identify highly active, synergistic drug combinations, and combinations were subsequently validated in multiple cell lines using various agents from each class. Comprehensive metabolomic and proteomic profiling was performed to better understand the mechanism underlying the synergy. Xenograft experiments were performed to determine efficacy and in vivo mechanism.Results: Several promising candidates emerged, including the combination of small-molecule PARP and nicotinamide phosphoribosyltransferase (NAMPT) inhibitors, a rational combination as NAMPTis block the rate-limiting enzyme in the production of nicotinamide adenine dinucleotide (NAD⁺), a necessary substrate of PARP. Mechanistic drivers of the synergistic cell killing phenotype of these combined drugs included depletion of NMN and NAD⁺, diminished PAR activity, increased DNA damage, and apoptosis. Combination PARPis and NAMPTis in vivo resulted in tumor regression, delayed disease progression, and increased survival.Conclusions: These studies highlight the potential of these drugs as a possible therapeutic option in treating patients with Ewing sarcoma. Clin Cancer Res; 23(23); 7301-11. ©2017 AACR.

Abstract 1930: Evaluating the effect of PARP inhibitors in combination with nicotinamide phosphoribosyltransferase inhibitors in Ewing sarcoma

Previous research has shown that Ewing sarcoma cells are sensitive to PARP inhibition, but in vivo studies and early phase clinical trials have failed to demonstrate meaningful responses to PARP inhibitors when used as single agents. For this reason, studies combining PARP inhibitors with other agents to enhance their effects in Ewing sarcoma are of particular interest. PARP, an enzyme involved in DNA damage repair, relies on NAD to function. In tumor cells, NAD production occurs primarily through the salvage pathway, in which nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme. Hence, the combination of PARP and NAMPT inhibition would be expected to enhance the activity of PARP inhibition through depletion of cellular NAD. The aim of this study was to assess the synergistic potential of PARP inhibition in combination with NAMPT inhibition in Ewing sarcoma cell lines and xenograft models. Synergistic drug combinations in Ewing sarcoma cells were initially identified using a high-throughput matrix drug screen. In vitro activity was further assessed using proliferation assays of multiple Ewing sarcoma cell lines treated with the PARP inhibitor niraparib and the NAMPT inhibitor GNE-618. In vitro measurement of PAR activity was performed to further understand the mechanism of action of the combination. For in vivo studies, female SCID-biege mice were orthotopically injected with Ewing sarcoma cells and randomized into treatment groups of vehicle, niraparib, GNE-618, or the combination. The initial screen revealed synergy between NAMPT inhibitors and PARP inhibitors using multiple combinations of different agents in each drug class. In vitro assays of the combination of niraparib with GNE-618 confirmed the results of the screen. Assays measuring PAR activity yielded results supporting the hypothesis that dual inhibition of NAMPT and PARP depletes PARP more than PARP inhibitors alone. In vivo studies with short term (5 day) dosing showed no activity of single agent nirapirib and only temporary disease stabilization with single agent GNE-618. However, mice treated with the combination underwent tumor regressions resulting in prolonged survival. When treatments were extended to 2 cycles (5 days each), the effect persisted for longer. Mice tolerated the agents well, with no signs of toxicity. Preclinical data suggest that PARP inhibition in combination with NAMPT inhibition may be a promising therapeutic strategy for Ewing sarcoma patients.

Citation Format: Joshua T. Baumgart, Christine Heske, Mindy I. Davis, Kelli Wilson, Xiaoha Zhang, Rajarshi Guha, Marc Ferrer, Arnulfo Mendoza, Craig J. Thomas, Lee J. Helman. Evaluating the effect of PARP inhibitors in combination with nicotinamide phosphoribosyltransferase inhibitors in Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1930. doi:10.1158/1538-7445.AM2017-1930

Abstract 5522: Novel myogenic differentiation transcription factor CASZ1 suppresses rhabdomyosarcoma tumor growth

Disruption of muscle regulatory factors (MRFs) in muscle progenitor cells results in a failure to withdraw from cell cycle and terminal differentiation and is proposed to contribute to rhabdomyosarcoma (RMS) tumorigenesis. Zinc finger transcription factor CASZ1 is a tumor suppressor gene and regulates normal nervous system and heart development. CASZ1 is known to regulate a subset of genes that are involved in skeletal muscle development although the function of CASZ1 in normal myogenesis and RMS tumorigenesis is unknown. CASZ1 levels increase over 20-fold when C2C12 myoblasts differentiate into myotubes. To probe its role in normal myogenesis we performed genetic knockdown or overexpression experiments in C2C12 myoblasts. When CASZ1 expression is silenced using RNAi, there is a significant reduction in myotubes upon induction of differentiation. Realtime PCR shows that knockdown of CASZ1 increases Myf5, a MRF that determines early commitment of muscle precursor cells, but decreases Myogenin (2-fold, p<0.01), a MRF required for terminal differentiation and myotube formation. Knockdown of CASZ1 also decreases late skeletal differentiation genes Acta1, Ckm, Tnnt1 and Tnni2 (> 2-fold, p<0.01). Overexpression of CASZ1 induces expression of Myogenin, Acta1, Ckm and Tnnt1, represses Myf5 and accelerates myotube formation. This indicates that CASZ1 regulates genes important in the transition from early to late myogenic differentiation. To investigate the role of CASZ1 in RMS, we first evaluated the expression of CASZ1 in primary RMS tumors using public available microarray database. CASZ1 mRNA levels are ~1.5-fold lower in embryonal RMS (ERMS) samples compared to normal muscle (p<0.001), while levels of CASZ1 in alveolar (ARMS) are similar to levels in normal muscle. CASZ1 levels increase over 3-fold when RD cells (ERMS) were cultured in differentiation medium (100 nM 12-O-tetradecanoylphorbol-13-acetate, TPA). Knockdown of CASZ1 in the RD cells suppressed TPA induced expression of myogenic markers TNNT1 and TNNI2 while CASZ1 overexpression stimulated expression of TNNT1 and TNNI2 (all p<0.05). An in vivo spontaneous xenograft model showed that overexpression of CASZ1 significantly suppressed RD tumor growth (p<0.005). In RMS patients, NexGen sequencing of 85 tumors identified 4 samples with nonsynonymous single nucleotide variants (SNVs) in CASZ1 that were absent in the 1000 Genomes databases. We engineered these SNVs into CASZ1 construct and transfected them into C2C12 cells. We found that the R25C SNV had impaired nuclear localization and failed to activate skeletal muscle gene transcription (p<0.03). Taken together, our results suggest that the regulation of muscle differentiation program by CASZ1 in C2C12 is integral to proper myogenic differentiation, and genetic variants of CASZ1 disrupt early myogenesis and may contribute to ERMS tumorigenesis and progression.

Citation Format: Zhihui Liu, Norris Lam, Arnulfo Mendoza, Jun S. Wei, John F. Shern, Marielle Yohe, Javed Khan, Carol J. Thiele. Novel myogenic differentiation transcription factor CASZ1 suppresses rhabdomyosarcoma tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5522. doi:10.1158/1538-7445.AM2017-5522

Grating coupled SPR microarray analysis of proteins and cells in blood from mice with breast cancer

Biomarker discovery for early disease diagnosis is highly important. Of late, much effort has been made to analyze complex biological fluids in an effort to develop new markers specific for different cancer types. Recent advancements in label-free technologies such as surface plasmon resonance (SPR)-based biosensors have shown promise as a diagnostic tool since there is no need for labeling or separation of cells. Furthermore, SPR can provide rapid, real-time detection of antigens from biological samples since SPR is highly sensitive to changes in surface-associated molecular and cellular interactions. Herein, we report a lab-on-a-chip microarray biosensor that utilizes grating-coupled surface plasmon resonance (GCSPR) and grating-coupled surface plasmon coupled fluorescence (GCSPCF) imaging to detect circulating tumor cells (CTCs) from a mouse model (FVB-MMTV-PyVT). GCSPR and GCSPCF analysis was accomplished by spotting antibodies to surface cell markers, cytokines and stress proteins on a nanofabricated GCSPR microchip and screening blood samples from FVB control mice or FVB-MMTV-PyVT mice with developing mammary carcinomas. A transgenic MMTV-PyVT mouse derived cancer cell line was also analyzed. The analyses indicated that CD24, CD44, CD326, CD133 and CD49b were expressed in both cell lines and in blood from MMTV-PyVT mice. Furthermore, cytokines such as IL-6, IL-10 and TNF-α, along with heat shock proteins HSP60, HSP27, HSc70(HSP73), HSP90 total, HSP70/HSc70, HSP90, HSP70, HSP90 alpha, phosphotyrosine and HSF-1 were overexpressed in MMTV-PyVT mice.

Upregulation of Glucose-Regulated Protein 78 in Metastatic Cancer Cells Is Necessary for Lung Metastasis Progression

Metastasis is the cause of more than 90% of all cancer deaths. Despite this fact, most anticancer therapeutics currently in clinical use have limited efficacy in treating established metastases. Here, we identify the endoplasmic reticulum chaperone protein, glucose-regulated protein 78 (GRP78), as a metastatic dependency in several highly metastatic cancer cell models. We find that GRP78 is consistently upregulated when highly metastatic cancer cells colonize the lung microenvironment and that mitigation of GRP78 upregulation via short hairpin RNA or treatment with the small molecule IT-139, which is currently under clinical investigation for the treatment of primary tumors, inhibits metastatic growth in the lung microenvironment. Inhibition of GRP78 upregulation and an associated reduction in metastatic potential have been shown in four highly metastatic cell line models: three human osteosarcomas and one murine mammary adenocarcinoma. Lastly, we show that downmodulation of GRP78 in highly metastatic cancer cells significantly increases median survival times in our in vivo animal model of experimental metastasis. Collectively, our data indicate that GRP78 is an attractive target for the development of antimetastatic therapies.

Aurora B kinase is a potent and selective target in MYCN-driven neuroblastoma

Despite advances in multimodal treatment, neuroblastoma (NB) is often fatal for children with high-risk disease and many survivors need to cope with long-term side effects from high-dose chemotherapy and radiation. To identify new therapeutic targets, we performed an siRNA screen of the druggable genome combined with a small molecule screen of 465 compounds targeting 39 different mechanisms of actions in four NB cell lines. We identified 58 genes as targets, including AURKB, in at least one cell line. In the drug screen, aurora kinase inhibitors (nine molecules) and in particular the AURKB-selective compound, barasertib, were the most discriminatory with regard to sensitivity for MYCN-amplified cell lines. In an expanded panel of ten NB cell lines, those with MYCN-amplification and wild-type TP53 were the most sensitive to low nanomolar concentrations of barasertib. Inhibition of the AURKB kinase activity resulted in decreased phosphorylation of the known target, histone H3, and upregulation of TP53 in MYCN-amplified, TP53 wild-type cells. However, both wild-type and TP53 mutant MYCN-amplified cell lines arrested in G2/M phase upon AURKB inhibition. Additionally, barasertib induced endoreduplication and apoptosis. Treatment of MYCN-amplified/TP53 wild-type neuroblastoma xenografts resulted in profound growth inhibition and tumor regression. Therefore, aurora B kinase inhibition is highly effective in aggressive neuroblastoma and warrants further investigation in clinical trials.

Digestive response of dairy cows fed diets combining fresh forage with a total mixed ration

The objective of this experiment was to quantify the response of dairy cows fed a total mixed ration (TMR) to increasing access to high-quality temperate fresh forage with respect to energy intake, rumen fermentation, microbial protein flow, passage rate, nutrient digestion and utilization, and metabolic and endocrine profiles. Nine Holstein cows fed a TMR were assigned to the following treatments according to a 3×3 Latin square replicated 3 times with 20-d periods and sampling on the last 10 d of each period: 0 (T0), 4 (T4), or 8 (T8) h of daily access to fresh forage. The forage (Lolium multiflorum; 17.1% crude protein, 26.5% acid detergent fiber) was cut daily and offered ad libitum beginning at 0800h, and a TMR (16.1% crude protein, 22.9% acid detergent fiber) was offered ad libitum during the remaining time. Energy intake and balance were higher in T0 than in T8, which was reflected in higher blood glucose and insulin concentrations in T0. Total volatile fatty acid concentrations in the rumen were higher in T0 and T4 than in T8, pH was lower in T4 than in T8, and ammonia-N was higher in T0 than in T8. No differences among treatments were detected in microbial protein flow to the duodenum, digestibility of nutrients, apparent efficiency of energy, or N utilization for milk production, but the total mean retention time of feed in the digestive tract was higher in T8 than in T0. It is concluded that more than 4h of daily access to high-quality fresh forage in the diet of dairy cows fed a TMR reduced energy intake and balance but had no effects on nutrient digestion or utilization.

Characterization of the metastatic phenotype of a panel of established osteosarcoma cells

Osteosarcoma (OS) is the most common bone tumor in pediatric patients. Metastasis is a major cause of mortality and morbidity. The rarity of this disease coupled with the challenges of drug development for metastatic cancers have slowed the delivery of improvements in long-term outcomes for these patients. In this study, we collected 18 OS cell lines, confirmed their expression of bone markers and complex karyotypes, and characterized their in vivo tumorgenicity and metastatic potential. Since prior reports included conflicting descriptions of the metastatic and in vivo phenotypes of these models, there was a need for a comparative assessment of metastatic phenotypes using identical procedures in the hands of a single investigative group. We expect that this single characterization will accelerate the study of this metastatic cancer. Using these models we evaluated the expression of six previously reported metastasis-related OS genes. Ezrin was the only gene consistently differentially expressed in all the pairs of high/low metatstatic OS cells. We then used a subtractive gene expression approach of the high and low human metastatic cells to identify novel genes that may be involved in OS metastasis. PHLDA1 (pleckstrin homology-like domain, family A) was identified as one of the genes more highly expressed in the high metastatic compared to low metastatic cells. Knocking down PHLDA1 with siRNA or shRNA resulted in down regulation of the activities of MAPKs (ERK1/2), c-Jun N-terminal kinases (JNK), and p38 mitogen-activated protein kinases (MAPKs). Reducing the expression of PHLDA1 also delayed OS metastasis progression in mouse xenograft models.

Abstract LB-151: Positively selected enhancer elements endow tumor cells with metastatic competence

Metastasis results from a complex set of traits acquired by tumor cells, distinct from those necessary for tumorigenesis. Here, we investigate the contribution of enhancer elements to the metastatic phenotype of osteosarcoma. Through epigenomic profiling, we identify substantial differences in signature enhancer-histone marks between near-isogenic pairs of high and low lung-metastatic osteosarcoma cells. We term these regions Metastatic Variant Enhancer Loci (Met-VELs). Met-VELs drive coordinated waves of gene expression during metastatic colonization of the lung. Met-VELs cluster non-randomly, indicating that activity of these enhancers and their associated gene targets is positively selected. Osteosarcoma lung metastasis is inhibited by global interruptions of Met-VEL associated gene expression via pharmacologic BET inhibition, by knockdown of AP-1 transcription factors whose motifs are enriched in Met-VELs, and by knockdown of individual genes activated by Met-VELs. These observations have implications for the discovery and development of targeted anti-metastatic therapies.

Citation Format: James J. Morrow, Tyler E. Miller, Alina Saiakhova, Michael M. Lizardo, Cynthia F. Bartels, Ian Bayles, Stevephen Hung, Arnulfo Mendoza, Jay T. Myers, Frederick Allen, Analisa DiFeo, Brian P. Rubin, Alex Y. Huang, Paul S. Meltzer, Lee J. Helman, Chand Khanna, Peter C. Scacheri. Positively selected enhancer elements endow tumor cells with metastatic competence. [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 LB-151.

mTOR Inhibition Mitigates Enhanced mRNA Translation Associated with the Metastatic Phenotype of Osteosarcoma Cells In Vivo

PURPOSE

To successfully metastasize, tumor cells must respond appropriately to biological stressors encountered during metastatic progression. We sought to test the hypothesis that enhanced efficiency of mRNA translation during periods of metastatic stress is required for metastatic competence of osteosarcoma and that this metastasis-specific adaptation is amenable to therapeutic intervention.

EXPERIMENTAL DESIGN

We employ novel reporter and proteomic systems that enable tracking of mRNA translation efficiency and output in metastatic osteosarcoma cells as they colonize the lungs. We test the potential to target mRNA translation as an antimetastatic therapeutic strategy through pharmacokinetic studies and preclinical assessment of the prototypic mTOR inhibitor, rapamycin, across multiple models of metastasis.

RESULTS

Metastatic osteosarcoma cells translate mRNA more efficiently than nonmetastatic cells during critical stressful periods of metastatic colonization of the lung. Rapamycin inhibits translational output during periods of metastatic stress, mitigates lung colonization, and prolongs survival. mTOR-inhibiting exposures of rapamycin are achievable in mice using treatment schedules that correspond to human doses well below the MTDs defined in human patients, and as such are very likely to be tolerated over long exposures alone and in combination with other agents.

CONCLUSIONS

Metastatic competence of osteosarcoma cells is dependent on efficient mRNA translation during stressful periods of metastatic progression, and the mTOR inhibitor, rapamycin, can mitigate this translation and inhibit metastasis in vivo Our data suggest that mTOR pathway inhibitors should be reconsidered in the clinic using rationally designed dosing schedules and clinical metrics related to metastatic progression. Clin Cancer Res; 22(24); 6129-41. ©2016 AACR.