Enhancing standard of care chemotherapy efficacy using DNA-dependent protein kinase (DNA-PK) inhibition in preclinical models of Ewing sarcoma

Disruption of DNA damage repair via impaired homologous recombination is characteristic of Ewing sarcoma (EWS) cells. We hypothesize that this disruption results in increased reliance on non-homologous end joining (NHEJ) to repair DNA damage. In this study, we investigated if pharmacological inhibition of the enzyme responsible for NHEJ, the DNA-PK holoenzyme, alters the response of EWS cells to genotoxic standard of care chemotherapy. We used analyses of cell viability and proliferation to investigate the effects of clinical DNA-PK inhibitors (DNA-PKi) in combination with six therapeutic or experimental agents for EWS. We performed calculations of synergy using the Loewe Additivity Model. Immunoblotting evaluated treatment effects on DNA-PK, DNA damage, and apoptosis. Flow cytometric analyses evaluated effects on cell cycle and fate. We used orthotopic xenograft models to interrogate tolerability, drug mechanism, and efficacy in vivo. DNA-PKi demonstrated on-target activity, reducing phosphorylated DNA-PK levels in EWS cells. DNA-PKi sensitized EWS cell lines to agents that function as topoisomerase 2 (TOP2) poisons and enhanced the DNA damage induced by TOP2 poisons. Nanomolar concentrations of single agent TOP2 poisons induced G2M arrest and little apoptotic response, while adding DNA-PKi mediated apoptosis. In vivo, the combination of AZD-7648 and etoposide had limited tolerability but resulted in enhanced DNA damage, apoptosis, and EWS tumor shrinkage. The combination of DNA-PKi with standard of care TOP2 poisons in EWS models is synergistic, enhances DNA damage and cell death, and may form the basis of a promising future therapeutic strategy for EWS.

Inhibition of NAD+-Dependent Metabolic Processes Induces Cellular Necrosis and Tumor Regression in Rhabdomyosarcoma Models

PURPOSE

Deregulated metabolism in cancer cells represents a vulnerability that may be therapeutically exploited to benefit patients. One such target is nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD+ salvage pathway. NAMPT is necessary for efficient NAD+ production and may be exploited in cells with increased metabolic demands. We have identified NAMPT as a dependency in rhabdomyosarcoma (RMS), a malignancy for which novel therapies are critically needed. Here we describe the effect of NAMPT inhibition on RMS proliferation and metabolism in vitro and in vivo.

EXPERIMENTAL DESIGN

Assays of proliferation and cell death were used to determine the effects of pharmacologic NAMPT inhibition in a panel of ten molecularly diverse RMS cell lines. Mechanism of the clinical NAMPTi OT-82 was determined using measures of NAD+ and downstream NAD+-dependent functions, including energy metabolism. We used orthotopic xenograft models to examine tolerability, efficacy, and drug mechanism in vivo.

RESULTS

Across all ten RMS cell lines, OT-82 depleted NAD+ and inhibited cell growth at concentrations ≤1 nmol/L. Significant impairment of glycolysis was a universal finding, with some cell lines also exhibiting diminished oxidative phosphorylation. Most cell lines experienced profound depletion of ATP with subsequent irreversible necrotic cell death. Importantly, loss of NAD and glycolytic activity were confirmed in orthotopic in vivo models, which exhibited complete tumor regressions with OT-82 treatment delivered on the clinical schedule.

CONCLUSIONS

RMS is highly vulnerable to NAMPT inhibition. These findings underscore the need for further clinical study of this class of agents for this malignancy.

A meta-analysis of the effects of colostrum heat treatment on colostral viscosity, immunoglobulin G concentration, and the transfer of passive immunity in newborn dairy calves

Newborn ruminants depend on colostrum intake immediately after birth to obtain immunoglobulins for effective transfer of passive immunity (TPI). As colostrum may also be a vehicle of infectious agents, heat treatment of raw colostrum is a practice aimed at eliminating or reducing its pathogen load. Despite the usefulness of heat treatment in preventing the transmission of infectious colostrum-borne diseases, heat treatment of colostrum may have some side effects. A systematic review and meta-analysis were conducted to summarize the effects of colostrum heat treatment on colostral viscosity and IgG concentration, and serum IgG concentration as a proxy for TPI in newborn calves fed raw versus heat-treated colostrum. Moderators were studied to identify sources of heterogeneity. Literature databases were searched for peer-reviewed articles published between 1946 and 2022. A Master of Science thesis was also included. Five, 21, and 19 original publications were quantitatively evaluated in 3 separate meta-analyses, based on predefined selection criteria. Two-level and 3-level random-effects meta-analysis revealed a significant overall effect of heat treatment on colostral viscosity and IgG concentration, and serum IgG concentration in newborns. Heat-treated colostrum had significantly higher viscosity (21.0 cP, 95% CI: 3.8 to 38.2) and lower IgG concentration (-7.4 g/L, 95% CI: -11.1 to -3.7) compared with raw colostrum. Overall, newborn calves fed heat-treated colostrum had higher serum IgG concentrations (2.8 g/L, 95% CI: 1.4 to 4.0) 24-48 h after birth than those fed with raw colostrum. Particularly, this positive effect on the serum IgG concentrations was seen when colostrum was heat-treated at ≤60°C (2.9 g/L, 95% CI: 0.9 to 4.2) and when the standard low-temperature low-time (LTLT) method was used for heat treatment (2.6 g/L, 95% CI: 0.1 to 5.1). Colostrum treated at >60-63.5°C tended to have higher viscosity (275.6 cP, 95% CI: -37.9 to 589.3) and had lower IgG concentration (-21.7 g/L, 95% CI: -27.3 to -16.1). Calves fed colostrum treated at this temperature range had significantly lower serum IgG (-4.2 g/L, 95% CI: -7.9 to -0.4) compared with those fed raw colostrum. Heat treatment of colostrum at 72-76°C was not associated with a significant increase in colostral viscosity (6.3 cP, 95% CI: -324.3 to 336.9) nor a reduction in IgG colostral concentration (-13.1 g/L, 95% CI: -26.5 to 0.2), but calves fed colostrum treated at this temperature range had a significant reduction in serum IgG (-11.3 g/L, 95% CI: -17.1 to -5.4). Feeding newborn calves with colostrum heat-treated at ≤60°C by the standard LTLT method, particularly within 2 h after birth, resulted in increased serum IgG concentration at 24-48 h of age. Importantly, delaying feeding of heat-treated colostrum to newborns beyond 2 h of age resulted in no significant difference in IgG serum levels compared with feeding raw colostrum, highlighting the importance of early administration of heat-treated colostrum to favor TPI. On-farm colostrum heat treating should achieve an equilibrium between pathogen elimination and the preservation of colostral immunoglobulins while minimizing undesired increases in viscosity. The beneficial effects of colostrum heat treatment on TPI can be negligible if colostrum feeding is not performed within 2 h after birth.

Using the single-cell imaging system and orthotropic footpad injection to establish mouse models for experimental and spontaneous melanoma metastasis

Metastasis, a complex process, is responsible for most deaths in patients with cancer. Clinically relevant research models are indispensable to advancing our understanding of metastatic mechanisms and developing new treatments. We here describe detailed protocols to establish mouse models for melanoma metastasis using the single-cell imaging system and orthotropic footpad injection. The single-cell imaging system permits the tracking and quantification of early metastatic cell survival, while the orthotropic footpad transplantation mimics aspects of the complex metastatic process. For complete details on the use and execution of this protocol, please refer to Yu et al.1,2.

Including 8 hours of access to alfalfa in 1 or 2 grazing sessions in dairy cows fed a partial mixed ration: Effects on intake, behavior, digestion, and milk production and composition

The aim of this study was to evaluate the inclusion of alfalfa grazing during 8 h continuous or partitioned in 2 separated sessions of 4 h after each milking, on nutrient intake, digestibility, ruminal fermentation, feeding behavior, milk production, milk composition, and milk fatty acid profile, in late-lactation cows fed a partial mixed ration (PMR). Twelve dairy cows (193 ± 83 d in milk, 584 ± 71 kg of body weight) were housed in individual outdoor pens and assigned to treatments according to a 3 × 3 Latin square design replicated 4 times. The treatments were as follows: (1) control (T0), cows were fed a total mixed ration (TMR) provided ad libitum 20.0% crude protein (CP), 32.2% neutral detergent fiber (NDF); (2) fed a diet combining a PMR which had the same ingredient composition as the TMR (60% of ad libitum intake) + 1 session of 8 h of pasture (T8), continuous grazing alfalfa (Medicago sativa; 20.6% CP, 35.8% NDF) after the p.m. milking; and (3) PMR (60% of ad libitum intake) + 2 daily sessions of 4 h of access to pasture after each milking (T4+4). The experiment lasted 57 d and was divided into 3 periods of 19 d each. The first 12 d of each period was used for diet adaptation, and the last 7 d was used for data collection. No differences among treatments were observed for any of the productive variables, feeding efficiency, or purine derivatives excretion. Cows in T0 had greater intake and apparent digestibility of dry matter, organic matter, and nonfibrous carbohydrates compared with T4+4 and T8. Compared with T0, alfalfa grazing increased the concentration of C18:1 trans-11 and decreased those of C16:0 and C17:0 in milk fat. Cows in T4+4 consumed 1.1 more kg DM/d of alfalfa and N provided by alfalfa in the diet was 3 percentage points higher compared with T8 cows (266 vs. 229 g/d, respectively). In addition, T4+4 cows had a greater daily range of ruminal pH than T8 (0.73 vs. 0.93), and the highest concentrations of NH3-N were recorded during the a.m. grazing session while in T8 cows it occurred during the night. In conclusion, including 8 h of alfalfa grazing in T8 and T4+4 treatments allowed the substitution between 35.8 and 38.7% of the total dry matter intake (DMI) of a PMR (with a similar CP concentration to alfalfa) for pasture, maintaining milk solids production and increasing the C18:1 trans-11 of milk fat compared with a TMR in mid late-lactation cows. In an herbage plus PMR diet, splitting the 1 continuous grazing session of 8 h into 2 sessions of 4 h increased the proportion of energy and N provided by alfalfa pasture and reduced PMR intake, without modifying the total nutrient intake or productive performance of cows.

Milk fatty acid profile from grass feeding strategies on 2 Holstein genotypes: Implications for health and technological properties

The objective of the study was to determine if a feeding system with a variable supply of grass promoted rapid changes in the fatty acid profile and technological and health indices of milk obtained from North American (NAHF) and New Zealand (NZHF) Holstein-Friesian cows. Two feeding strategies were conducted: fixed grass (GFix) and maximized grass intake when available (GMax). The results showed that as the grass intake increased in the GMax treatments, the relative amount of palmitic acid in milk decreased, whereas oleic, linoleic, linolenic, and conjugated linoleic acids increased, causing a reduction in the atherogenic, thrombogenic, and spreadability calculated indices. The changes occurred in rapid response to the changing diet, with reductions ranging from approximately 5 to 15% in the healthy and technological indices within a period of 15 d of grass intake increase. Differences were found between the 2 genotypes, with NZHF responding faster to changes in grass intake.

Abstract 6718: Exploiting metabolic vulnerabilities of pediatric rhabdomyosarcoma with novelnicotinamide phosphoribosyltransferase (NAMPT) inhibitor OT-82

Purpose: A hallmark of cancer cells is altered metabolism. Therapeutically, these alterations may be exploited by targeting metabolic vulnerabilities specific to cancer cells. Efficient production of NAD through the NAD salvage pathway is one such potential vulnerability, as some tumor cells demonstrate a high need for rapid NAD turnover. Nicotinamide phosphoribosyltransferase (NAMPT) is the pharmacologically targetable rate-limiting enzyme in this pathway. We report on the effect of targeting NAMPT in models of pediatric rhabdomyosarcoma (RMS), a cancer for which novel therapeutics remain an unmet need.

Experimental Procedures: The relative sensitivity of RMS cell lines to NAMPT inhibitors was first compared to NAMPT inhibitor sensitivity of other cancer cell lines using viability assays. A panel of ten molecularly diverse RMS cell lines was used for the remainder of the evaluations. In vitro activity of NAMPT inhibition was evaluated using assays of proliferation and cell death. Measurements of NAD and functional assessment of NAD-dependent processes, such as glucose metabolism, were used to study the mechanistic activity of NAMPT inhibition in these models. In vivo studies included assessments of toxicity, efficacy, and mechanism of action of a clinical NAMPT inhibitor, OT-82, in four orthotopic RMS models.

Results: RMS cells showed striking sensitivity to NAMPT inhibition with IC-50 values in the low nanomolar range. In vitro, NAMPT inhibition resulted in NAD depletion and impaired cellular proliferation. Effects on glucose metabolism included decreases in glycolytic activity and glycolytic capacity in all cell lines tested, as well as decreased oxidative phosphorylation in a subset of cell lines. The majority of cell lines exhibited ATP depletion and irreversible necrotic cell death. Apoptotic cell death was not observed. In vivo, the effects of OT-82 treatment delivered on the human clinical schedule replicated those seen in vitro, including loss of glycolytic activity as measured using hyperpolarized 13C MRI spectroscopy. In all four xenograft models, complete tumor regressions were observed at multiple doses and with minimal toxicity.

Conclusions: NAMPT inhibition with OT-82 was highly effective in decreasing RMS proliferation and impairing glucose metabolism both in vitro and in vivo. Given these results, there is a critical need for further clinical study of this class of agents for RMS.

Citation Format: Grace McKay-Corkum, Victor J. Collins, Choh Yeung, Takeshi Ito, Sameer H. Issaq, Arnulfo Mendoza, Kazutoshi Yamamoto, Murali Cherukuri, Len Neckers, Christine M. Heske. Exploiting metabolic vulnerabilities of pediatric rhabdomyosarcoma with novelnicotinamide phosphoribosyltransferase (NAMPT) inhibitor OT-82 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6718.

CHALLENGING THE DOGMAS: LAPAROSCOPIC COMMON BILE DUCT EXPLORATION THROUGH DIATHERMY, CHOLEDOCHOTOMY AND PRIMARY CLOSURE. LONG TERM OUTCOMES IN A REFERRAL CENTER

Introduction

Choledocholithiasis is a frequent pathology, unfortunately when its endoscopic management fails there is no consensus on how it should be addressed. The aim of this study was to evaluate the safety, feasibility and long-term outcomes of laparoscopic common bile duct exploration (LCDBE) using electrosurgery (coagulation) for choledochotomy followed by primary closure after endoscopic treatment failure.

Methods

A retrospective cohort of 168 patients who underwent LCDBE from 2013 to 2018 which was conducted all by choledochotomy. Clinical demographics, operative outcomes, recurrence rate of CBD stones, and long-term bile duct complications were analyzed.

Results

The male/female ratio was 90/78 and mean age was 73 years. Stone clearance was successful in 167 patients (99.4%). Nonlethal complications were noted in 3 patients during the surgery or in the immediate postoperative (1.79%) and managed with T-tube or endoscopically. No cases of surgery-related mortality were observed. There were no signs of any type of biliary injury or stricture observed in any of the patients during the 24-month follow-up period.

Conclusions

LCBDE through choledochotomy with diathermy and primary closure can be performed without increased risk of operative complications such as important and visual-impairment bleeding as well as long-term complications such as bile duct stricture or recurrent CBD stones. LCBDE with diathermy and primary closure is a safe and effective treatment option for choledocholithiasis for failed ERCP in terms of long-term outcome as well as short-term outcome.

The Assessment of the Diagnostic Accuracy of Antigen-Detecting Rapid Diagnostic Test using Nasopharyngeal Swab Specimen in Detecting SARS-CoV-2 among Patients in a Private Hospital in Bulacan, Philippines

Introduction/Objective

Continuous progression of the COVID-19 outbreak prompted an expensive, limited, and slow-moving laboratory-based molecular testing capacity of the gold standard, Real-time Reverse Transcription- Polymerase Chain Reaction (rRT-PCR), in detecting SARS-CoV-2. The vital step in mitigation is utilizing an accurate diagnostic detection assay to deploy various preventive measures. Therefore, there is a need to evaluate an accessible, fast, and inexpensive point-of-care immunoassay, such as Antigen-detecting Rapid Diagnostic Tests (Ag- RDTs). Thus, the study aimed to assess the diagnostic accuracy of Ag-RDT in detecting SARS-CoV-2.

Methods/Case Report

A non-experimental, quantitative, and cross-sectional cohort study utilized 272 SARS-CoV-2 Ag-RDT with rRT-PCR confirmation collected from April 2021 to February 2022 in a private primary hospital laboratory database in Bulacan, Philippines. Diagnostic accuracy parameters of Ag-RDT included in the study are sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results (if a Case Study enter NA)

The overall sensitivity and specificity of Ag-RDT were 69.6% and 98.8%, respectively. Additionally, it exhibited a PPV of 84.2% and an NPV of 97.2%. With a hypothetical 1% prevalence, PPV and NPV were 36.8% and 99.7%. Meanwhile, PPV and NPV were 86.5% and 96.7% at 10% prevalence. High specificity denotes that positive Ag-RDT test results can be confidently considered in true SARS-CoV-2 infection, while low sensitivity entails that a negative result must be subjected to confirmatory tests. Furthermore, when prevalence increases, PPV increases while NPV decreases.

Conclusion

The study primarily encapsulated that the Ag-RDT cannot replace rRT-PCR in detecting SARS-CoV-2 infections. Despite its shortcomings, Ag-RDT is still valuable in areas with moderate-to-high disease prevalence and with limited access to confirmatory test due to its high predictive values and advantages. A larger number of positive results of rRT-PCR, evaluation of factors correlating to low sensitivity, and a prospective study are recommended for future studies.

Caregiver willingness to give TPT to children living with drug-resistant TB patients

BACKGROUND Pediatric household contacts (HHCs) of patients with multidrug-resistant TB (MDR-TB) are at high risk of infection and active disease. Evidence of caregiver willingness to give MDR-TB preventive therapy (TPT) to children is limited.METHODS This was a cross-sectional study of HHCs of patients with MDR-TB to assess caregiver willingness to give TPT to children aged <13 years.RESULTS Of 743 adult and adolescent HHCs, 299 reported caring for children aged <13 years of age. The median caregiver age was 35 years (IQR 27-48); 75% were women. Among caregivers, 89% were willing to give children MDR TPT. In unadjusted analyses, increased willingness was associated with TB-related knowledge (OR 5.1, 95% CI 2.3-11.3), belief that one can die of MDR-TB (OR 5.2, 95% CI 1.2-23.4), concern for MDR-TB transmission to child (OR 4.5, 95% CI 1.6-12.4), confidence in properly taking TPT (OR 4.5, 95% CI 1.6-12.6), comfort telling family about TPT (OR 5.5, 95% CI 2.1-14.3), and willingness to take TPT oneself (OR 35.1, 95% CI 11.0-112.8).CONCLUSIONS A high percentage of caregivers living with MDR- or rifampicin-resistant TB patients were willing to give children a hypothetical MDR TPT. These results provide important evidence for the potential uptake of effective MDR TPT when implemented.

Genetic background in pediatric pulmonary arterial hypertension. Should we change the current recommendations for genetic testing?

Background

Pulmonary arterial hypertension (PAH) is a rare and severe disease, genetically predisposed in a high proportion of patients. PAH is subclassified in different subtypes depending on the underlying condition. Gene variants are more frequent among heritable or idiopathic forms. Nevertheless, pathogenic variants have been described across the entire spectrum of this disease. Evidence regarding genetics in pediatric PAH is scarce [1].

Purpose

Our aim is to describe the prevalence of significant gene mutations among a pediatric PAH cohort and to define specific data in the different subtypes.

Methods

Samples for genetic studies were obtained from blood tests of patients included in the Spanish National Registry of Pediatric Pulmonary Hypertension (REHIPED). Guardians signed informed consent before the inclusion in the study. Qualitative variables were compared by Chi-square test. Quantitative variables were assessed by Kruskal-Wallis, considering the asymmetric distribution of variables. STATA 14.0 was used for analyses.

Results

Sixty four patients were included between 2011 and 2021. Median age of the entire sample was 7.1 years (2.0–12.6) and 42.2% of them were male. There were significant differences in the age at diagnosis and race between the different included groups (table). Pathogenic or likely pathogenic variants were more frequent in familial pulmonary venooclusive disease (PVOD) and familial PAH cases. A similar percentage of mutations were found in idiopathic cases and in PAH associated with congenital heart disease (Figure). Gene variants in the gene encoding the bone morphogenetic protein receptor type 2 (BMPR2) were the most frequent mutations in the PAH familial cohort and there was also the most frequent finding in congenital heart disease and sporadic PAH, in conjunction with the TBX4 gene. Homozygous or compound heterozygous EIF2AK4 (eukaryotic translation initiation factor 2 a kinase 4) mutations were found in all the patients diagnosed with PVOD. Heritable PAH and PVOD cases were diagnosed more frequently after family screening.

Conclusions

This study shows a comparable proportion of pathogenic-likely pathogenic gene mutations in patients diagnosed of pulmonary arterial hypertension associated with congenital heart disease and idiopathic cases, with similar distribution of specific genes. BMPR2 and TBX 4 were the most frequent gene variants in this pediatric PAH population. BMPR2 and EIF2AK4 are the most common mutations in familial PAH and PVOD subtypes, respectively.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): ACU holds a Rio Hortega Grant from the Instituto de Salud Carlos III, Spanish Ministry of Science and Innovation.JAT and NG hold grants from FEDER (Federaciόn Española de Enfermedades Raras) and from the FCHP. Table 1. Characteristics of PAH subtypesFigure 1. PAH and ACMG classification.

Intensification strategies for temperate hot-summer grazing dairy systems in South America: Effects of feeding strategy and cow genotype

Pasture-based dairy systems present the opportunity to increase productivity per hectare through increasing stocking rate and forage utilization. However, in the temperate hot-summer region of South America, different productive strategies are being adopted by farmers. The aim of this study was to quantify the effect of feeding strategy (FS) and cow genotype (G) on individual animal and whole-farm biophysical performance. A design with 2 × 2 levels of intensification aiming to increase home-grown forage utilization and milk output per hectare was evaluated. The experiment was a randomized complete block design with a 2 × 2 factorial arrangement of treatments, combining 2 feeding strategies with varying proportions of grazing in the annual feeding budget [grass fixed (GFix) and grass maximum (GMax)] and 2 Holstein Friesian cow genotypes [New Zealand (NZHF) or North American Holstein Friesian (NAHF)]. The effects of FS, G, and their interaction were analyzed using mixed models. New Zealand Holstein Friesian cows presented lower individual milk yield and higher milk component concentrations, maintained higher average body condition score, and increased body weight (BW) throughout the experiment, while presenting a better reproductive performance compared with the NAHF cows. Although all farmlets were planned at the same stocking rate on a per kilogram of BW basis, the current stocking rate changed as a result of animal performance and grass utilization resulting in NZHF cows achieving greater BW per hectare. The superior stocking rate led to greater milk solids production and feed consumption per hectare for the systems with NZHF cows. The GFix feeding strategy resulted in greater total home-grown forage harvest and conserved forage surplus than GMax. Overall, it was feasible to increase stocking rate and increase milk production per hectare from home-grown forage with differing feeding strategies and Holstein Friesian cow genotypes within grazing systems located in the temperate hot-summer climate region of South America. The interactions reported between FS × G highlight the superior productivity per hectare of NZHF cows within the GMax feeding strategy based on maximizing grazed pasture, which could represent a competitive intensification strategy in terms of cost of production for this region.

Rigosertib Induces Mitotic Arrest and Apoptosis in RAS-Mutated Rhabdomyosarcoma and Neuroblastoma

Relapsed pediatric rhabdomyosarcomas (RMS) and neuroblastomas (NBs) have a poor prognosis despite multimodality therapy. In addition, the current standard of care for these cancers includes vinca alkaloids that have severe toxicity profiles, further underscoring the need for novel therapies for these malignancies. Here, we show that the small-molecule rigosertib inhibits the growth of RMS and NB cell lines by arresting cells in mitosis, which leads to cell death. Our data indicate that rigosertib, like the vinca alkaloids, exerts its effects mainly by interfering with mitotic spindle assembly. Although rigosertib has the ability to inhibit oncogenic RAS signaling, we provide evidence that rigosertib does not induce cell death through inhibition of the RAS pathway in RAS-mutated RMS and NB cells. However, the combination of rigosertib and the MEK inhibitor trametinib, which has efficacy in RAS-mutated tumors, synergistically inhibits the growth of an RMS cell line, suggesting a new avenue for combination therapy. Importantly, rigosertib treatment delays tumor growth and prolongs survival in a xenograft model of RMS. In conclusion, rigosertib, through its impact on the mitotic spindle, represents a potential therapeutic for RMS.

Abstract 5714: Targeting serine metabolism impairs tumor growth in preclinical models of Ewing sarcoma

Despite a growing body of knowledge about the genomic landscape of Ewing sarcoma (ES), translation of basic discoveries into targeted therapies and significant clinical gains has remained elusive. Recent insights have revealed that the oncogenic transcription factor EWS-FLI1 can impact ES cellular metabolism, raising the possibility of targeting metabolic dependencies as a novel therapeutic strategy. Here, we show that 3-phosphoglycerate dehydrogenase (PHGDH), the first enzyme in de novo serine synthesis, is highly expressed in human ES cells and that EWS-FLI1 regulates PHGDH expression and de novo serine synthesis. PHGDH knockdown resulted in decreased ES cell proliferation, especially under serine limitation, and significantly inhibited xenograft tumorigenesis in preclinical orthotopic models of ES. Additionally, the PHGDH inhibitor NCT-503 caused a dose-dependent decrease in cellular proliferation. Moreover, we report a novel drug combination in which nicotinamide phosphoribosyltransferase (NAMPT) inhibition, which blocks production of the PHGDH substrate NAD+, synergized with NCT-503 to abolish ES cellular proliferation and tumor growth. Furthermore, we show that serine deprivation inhibited ES cell proliferation and tumorigenesis, indicating that ES cells depend on exogenous serine in addition to de novo serine synthesis. Our findings suggest that serine metabolism is critical for ES tumorigenesis, and that targeting serine metabolism should be further investigated as a potential therapeutic strategy for ES.

Citation Format: Sameer Issaq, Arnulfo Mendoza, Tracy Rosales, Christine Heske, Craig Thomas, Ralph DeBerardinis, Lee Helman. Targeting serine metabolism impairs tumor growth in preclinical models of Ewing sarcoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5714.

Abstract PR08: Lactate dehydrogenase A is a pharmacologically tractable EWS-FLI1 transcriptional target that regulates the glycolytic dependence of Ewing sarcoma

Altered cellular metabolism, including an increased dependence on aerobic glycolysis, is a hallmark of cancer. Despite the fact that this observation was first made nearly a century ago, effective therapeutic targeting of glycolysis in cancer has remained elusive. One potentially promising approach involves targeting the glycolytic enzyme lactate dehydrogenase (LDH), which is overexpressed and plays a critical role in several cancers. To uncover cell type-specific dependencies to LDH, we screened a diverse panel of 94 cancer cell lines for responsiveness to two novel LDH A/B inhibitors developed through the NCI Experimental Therapeutics Program (NExT). We found that Ewing sarcoma (EWS) cell lines were exquisitely sensitive, with IC50 values approximately ten-fold below the median IC50 of the panel. To understand the mechanism behind this sensitivity, we genetically knocked down LDHA and LDHB using siRNA, and discovered that EWS cell lines were sensitive to loss of LDHA only, which inhibited proliferation and induced apoptosis. Notably, treatment of EWS cells with the LDH inhibitors phenocopied these effects. Additionally, genetic knockdown of EWS-FLI1, the oncogenic driver of EWS, resulted in loss of LDHA, but not LDHB. Analysis of publicly available ChIP-seq data generated using shFLI1-transfected EWS cells revealed that LDHA, but not LDHB, is directly regulated by EWS-FLI1. Functional mechanistic studies of glycolytic intermediates and cellular bioenergetics in EWS cells treated with the LDH inhibitors demonstrated that loss of viability was due to impairment of glycolysis, which occurred both in vitro and in vivo, and perturbation of the NAD+/NADH ratio. The translational potential of these compounds was next evaluated using in vivo analyses of pharmacokinetics, pharmacodynamics, efficacy, and toxicity. Intravenous administration of the LDH inhibitors resulted in diminished LDH activity, reduction of the lactate-to-pyruvate ratio, tumor cell necrosis, and a decrease in tumor growth rate in aggressive xenograft models of EWS. The major dose-limiting toxicity observed was hemolysis, indicating that a narrow therapeutic window exists for these compounds. Taken together, our data suggest that targeting glycolysis through inhibition of LDH should be further investigated as a potential therapeutic approach for cancers such as EWS that exhibit oncogene-dependent expression of LDH and increased glycolytic activity.

This abstract is also being presented as Poster B33.

Citation Format: Choh Yeung, Anna E. Gibson, Sameer H. Issaq, Nobu Oshima, Marielle E. Yohe, Haiyan Lei, Ganesha Rai, Daniel J. Urban, Michelle S. Johnson, Gloria A. Benevides, Giuseppe L. Squadrito, Sandy Eldridge, John Hamre III, Arnulfo Mendoza, Jack F. Shern, Lee J. Helman, Murali C. Krishna, Matthew D. Hall, Victor M. Darley-Usmar, Leonard M. Neckers, Christine M. Heske. Lactate dehydrogenase A is a pharmacologically tractable EWS-FLI1 transcriptional target that regulates the glycolytic dependence of Ewing sarcoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr PR08.

EWS-FLI1-regulated Serine Synthesis and Exogenous Serine are Necessary for Ewing Sarcoma Cellular Proliferation and Tumor Growth

Despite a growing body of knowledge about the genomic landscape of Ewing sarcoma, translation of basic discoveries into targeted therapies and significant clinical gains has remained elusive. Recent insights have revealed that the oncogenic transcription factor EWS-FLI1 can impact Ewing sarcoma cellular metabolism, regulating expression of 3-phosphoglycerate dehydrogenase (PHGDH), the first enzyme in de novo serine synthesis. Here, we have examined the importance of serine metabolism in Ewing sarcoma tumorigenesis and evaluated the therapeutic potential of targeting serine metabolism in preclinical models of Ewing sarcoma. We show that PHGDH knockdown resulted in decreased Ewing sarcoma cell proliferation, especially under serine limitation, and significantly inhibited xenograft tumorigenesis in preclinical orthotopic models of Ewing sarcoma. In addition, the PHGDH inhibitor NCT-503 caused a dose-dependent decrease in cellular proliferation. Moreover, we report a novel drug combination in which nicotinamide phosphoribosyltransferase (NAMPT) inhibition, which blocks production of the PHGDH substrate NAD⁺, synergized with NCT-503 to abolish Ewing sarcoma cell proliferation and tumor growth. Furthermore, we show that serine deprivation inhibited Ewing sarcoma cell proliferation and tumorigenesis, indicating that Ewing sarcoma cells depend on exogenous serine in addition to de novo serine synthesis. Our findings suggest that serine metabolism is critical for Ewing sarcoma tumorigenesis, and that targeting metabolic dependencies should be further investigated as a potential therapeutic strategy for Ewing sarcoma. In addition, the combination strategy presented herein may have broader clinical applications in other PHGDH-overexpressing cancers as well.

CASZ1 induces skeletal muscle and rhabdomyosarcoma differentiation through a feed-forward loop with MYOD and MYOG

Embryonal rhabdomyosarcoma (ERMS) is a childhood cancer that expresses myogenic master regulatory factor MYOD but fails to differentiate. Here, we show that the zinc finger transcription factor CASZ1 up-regulates MYOD signature genes and induces skeletal muscle differentiation in normal myoblasts and ERMS. The oncogenic activation of the RAS-MEK pathway suppresses CASZ1 expression in ERMS. ChIP-seq, ATAC-seq and RNA-seq experiments reveal that CASZ1 directly up-regulates skeletal muscle genes and represses non-muscle genes through affecting regional epigenetic modifications, chromatin accessibility and super-enhancer establishment. Next generation sequencing of primary RMS tumors identified a single nucleotide variant in the CASZ1 coding region that potentially contributes to ERMS tumorigenesis. Taken together, loss of CASZ1 activity, due to RAS-MEK signaling or genetic alteration, impairs ERMS differentiation, contributing to RMS tumorigenesis.

MEK inhibition induces MYOG and remodels super-enhancers in RAS-driven rhabdomyosarcoma

The RAS isoforms are frequently mutated in many types of human cancers, including PAX3/PAX7 fusion-negative rhabdomyosarcoma. Pediatric RMS arises from skeletal muscle progenitor cells that have failed to differentiate normally. The role of mutant RAS in this differentiation blockade is incompletely understood. We demonstrate that oncogenic RAS, acting through the RAF-MEK [mitogen-activated protein kinase (MAPK) kinase]-ERK (extracellular signal-regulated kinase) MAPK effector pathway, inhibits myogenic differentiation in rhabdomyosarcoma by repressing the expression of the prodifferentiation myogenic transcription factor, MYOG. This repression is mediated by ERK2-dependent promoter-proximal stalling of RNA polymerase II at the MYOG locus. Small-molecule screening with a library of mechanistically defined inhibitors showed that RAS-driven RMS is vulnerable to MEK inhibition. MEK inhibition with trametinib leads to the loss of ERK2 at the MYOG promoter and releases the transcriptional stalling of MYOG expression. MYOG subsequently opens chromatin and establishes super-enhancers at genes required for late myogenic differentiation. Furthermore, trametinib, in combination with an inhibitor of IGF1R, potently decreases rhabdomyosarcoma cell viability and slows tumor growth in xenograft models. Therefore, this combination represents a potential therapeutic for RAS-mutated rhabdomyosarcoma.

Targeting Glycolysis through Inhibition of Lactate Dehydrogenase Impairs Tumor Growth in Preclinical Models of Ewing Sarcoma

Altered cellular metabolism, including an increased dependence on aerobic glycolysis, is a hallmark of cancer. Despite the fact that this observation was first made nearly a century ago, effective therapeutic targeting of glycolysis in cancer has remained elusive. One potentially promising approach involves targeting the glycolytic enzyme lactate dehydrogenase (LDH), which is overexpressed and plays a critical role in several cancers. Here, we used a novel class of LDH inhibitors to demonstrate, for the first time, that Ewing sarcoma cells are exquisitely sensitive to inhibition of LDH. EWS-FLI1, the oncogenic driver of Ewing sarcoma, regulated LDH A (LDHA) expression. Genetic depletion of LDHA inhibited proliferation of Ewing sarcoma cells and induced apoptosis, phenocopying pharmacologic inhibition of LDH. LDH inhibitors affected Ewing sarcoma cell viability both in vitro and in vivo by reducing glycolysis. Intravenous administration of LDH inhibitors resulted in the greatest intratumoral drug accumulation, inducing tumor cell death and reducing tumor growth. The major dose-limiting toxicity observed was hemolysis, indicating that a narrow therapeutic window exists for these compounds. Taken together, these data suggest that targeting glycolysis through inhibition of LDH should be further investigated as a potential therapeutic approach for cancers such as Ewing sarcoma that exhibit oncogene-dependent expression of LDH and increased glycolysis. SIGNIFICANCE: LDHA is a pharmacologically tractable EWS-FLI1 transcriptional target that regulates the glycolytic dependence of Ewing sarcoma.

Carbohydrate source offered in the prepartum diet did not affect postpartum metabolic status or milk yield in dairy cows

Increasing the provision of non-fibrous carbohydrates (NFC) during the prepartum period is a feeding strategy that has been recommended to facilitate the transition to the onset of lactation and improve dairy cow performance, but results are contradictory, probably because most studies have confounded the effects of level and source of energy. The objective of this experiment was to evaluate the effect of the source of carbohydrate offered in the prepartum diet on postpartum cow performance. Holstein dairy cows (n=24) were assigned to receive diets with either low (LNFC), or high (HNFC) levels of NFC during the last 3 weeks before expected calving date according to a randomized complete block design. Soybean hulls and corn grain were the main energy ingredients in the LNFC and HNFC total mixed rations (TMR), respectively, and diets were designed to be isocaloric and isoproteic. After calving, all cows were managed as a single group until day 56 postpartum and grazed on improved pastures and were supplemented with a TMR. Body condition score evaluation and blood sampling were performed weekly throughout the experimental period to monitor the metabolic status of the animals. Prepartum glucose concentrations tended to be greater in HNFC than LNFC, but there was no effect on prepartum or postpartum insulin concentrations. Although nutrient intake was greater in the immediate week after calving in HNFC than LNFC, treatment did not affect milk yield and composition. In conclusion, increasing the NFC intake during the prepartum period, at a similar level of energy and protein intake, had a marginal residual effect on postpartum intake, and did not affect metabolic status or milk production.

HIV testing uptake among the household contacts of multidrug-resistant tuberculosis index cases in eight countries

SETTING

The household contacts (HHCs) of multidrug-resistant tuberculosis (MDR-TB) index cases are at high risk of tuberculous infection and disease progression, particularly if infected with the human immunodeficiency virus (HIV). HIV testing is important for risk assessment and clinical management.

METHODS

This was a cross-sectional, multi-country study of adult MDR-TB index cases and HHCs. All adult and child HHCs were offered HIV testing if never tested or if HIV-negative >1 year previously when last tested. We measured HIV testing uptake and used logistic regression to evaluate predictors.

RESULTS

A total of 1007 HHCs of 284 index cases were enrolled in eight countries. HIV status was known at enrolment for 226 (22%) HHCs; 39 (4%) were HIV-positive. HIV testing was offered to 769 (98%) of the 781 remaining HHCs; 544 (71%) agreed to testing. Of 535 who were actually tested, 26 (5%) were HIV-infected. HIV testing uptake varied by site (median 86%, range 0-100%; P < 0.0001), and was lower in children aged <18 years than in adults (59% vs. 78%; adjusted for site P < 0.0001).

CONCLUSIONS

HIV testing of HHCs of MDR-TB index cases is feasible and high-yield, with 5% testing positive. Reasons for low test uptake among children and at specific sites-including sites with high HIV prevalence-require further study to ensure all persons at risk for HIV are aware of their status.

Targeting the Chromosomal Passenger Complex Subunit INCENP Induces Polyploidization, Apoptosis, and Senescence in Neuroblastoma

Chromosomal passenger complex (CPC) has been demonstrated to be a potential target of cancer therapy by inhibiting Aurora B or survivin in different types of cancer including neuroblastoma. However, chemical inhibition of either Aurora B or survivin does not target CPC specifically due to off-target effects or CPC-independent activities of these two components. In a previous chromatin-focused siRNA screen, we found that neuroblastoma cells were particularly vulnerable to loss of INCENP, a gene encoding a key scaffolding component of the CPC. In this study, INCENP was highly expressed by neuroblastoma cells, and its expression decreased following retinoic acid-induced neuroblastoma differentiation. Elevated levels of INCENP were significantly associated with poor prognosis in primary tumors of neuroblastoma patients with high-risk disease. Genetic silencing of INCENP reduced the growth of both MYCN-wild-type and MYCN-amplified neuroblastoma cell lines in vitro and decreased the growth of neuroblastoma xenografts in vivo, with significant increases in murine survival. Mechanistically, INCENP depletion suppressed neuroblastoma cell growth by inducing polyploidization, apoptosis, and senescence. In most neuroblastoma cell lines tested in vitro, apoptosis was the primary cell fate after INCENP silencing due to induction of DNA damage response and activation of the p53-p21 axis. These results confirm that CPC is a therapeutic target in neuroblastoma, and targeting INCENP is a novel way to disrupt the activity of CPC and inhibit tumor progression in neuroblastoma. SIGNIFICANCE: Dysregulation of INCENP contributes to neuroblastoma tumorigenesis and targeting INCENP presents a novel strategy to disrupt the activity of chromosomal passenger complex and inhibit neuroblastoma progression.

Reducing milking frequency in early lactation improved the energy status but reduced milk yield during the whole lactation of primiparous Holstein cows consuming a total mixed ration and pasture

To investigate the immediate and long-term performance effects of milking frequency during early lactation of primiparous dairy cows consuming a total mixed ration and pasture, 20 Holstein cows were assigned in a randomized block design to either once-daily (1×) or twice-daily (2×) milking during the first 8 wk of lactation (treatment period). After the treatment period, all cows were milked 2× until wk 43 of lactation. Cows were fed a total mixed ration (approximately 15 kg of DM/cow per day) and allowed to graze an oat pasture (Avena sativa). Dry matter intake was 19.1 kg of DM/cow per day on average and was not affected by treatments. Milk yield was 40% lower in cows milked 1× during the treatment period, and a carryover effect existed until wk 21 of lactation, resulting in a final reduction of 15% of milk yield in the whole lactation. Milk lactose concentration decreased, whereas fat and protein concentrations increased for cows milked 1×. Mobilization of energy reserves during the treatment period occurred in both groups, but cows milked 1× showed greater body condition score and greater backfat thickness. In conclusion, milking 1× during the first 8 wk of lactation resulted in immediate and carryover negative effects on milk and milk solid yield without affecting feed intake, resulting in the improved energy status of primiparous dairy cows.

Abstract 3592: Evaluation of OT-82, a nicotinamide phosphoribosyltransferase inhibitor (NAMPTi), as a potential therapeutic option for Ewing sarcoma

Targeting NAMPT, the rate-limited enzyme in the NAD salvage pathway, is a potentially attractive anticancer strategy, since cancer cells preferentially rely on this pathway to produce NAD. We explored the use of NAMPTi in Ewing sarcoma (ES), an aggressive pediatric malignancy for which novel therapeutic options are critically needed. We previously showed that ES cells are exceptionally sensitive to NAMPTi compared to other cancer types and have single agent activity in vitro and in vivo. We also demonstrated that combining NAMPTi with PARP inhibitors results in enhanced efficacy in vitro and in vivo. In this study, we further characterized the mechanisms of action of OT-82, a NAMPTi expected to enter early phase clinical trials, in ES cells and evaluated various dosing schedules for OT-82 combinations with cytotoxic therapy. On-target activity of OT-82 was assessed using NAD quantification assays and rescue experiments with multiple NAD intermediates. Characterization of NAD salvage pathway enzyme expression was performed by western blot. Mechanistic studies of cell cycle analysis, DNA damage, and cell death were performed using flow cytometry, western blotting, and comet assays. Glycolytic profiles of ES cell lines were analyzed using the Agilent Extracellular Flux Analyzer. Orthotopic ES cell line and PDX models in immunodeficient mice were used to evaluate in vivo combinations. Tumor measurements were performed with calipers twice weekly and toxicity was assessed with weekly body weights and general observations. Tumors were harvested at intermediate time points and at endpoints for biology and pharmacodynamic studies. Treatment with OT-82 revealed dose-dependent reduction of NAD both in vitro and in vivo. Addition of NMN, the product of NAMPT, rescued ES cell viability, indicating on-target activity of OT-82. While delayed NMN administration up to 48 hours after treatment with OT-82 rescued viability, a 72-hour delay rendered the effects irreversible in all cell lines. Treatment with OT-82 resulted in DNA damage, G2/M arrest and induction of apoptosis at 72 hours. Extracellular flux analysis indicated that OT-82 treatments resulted in a decrease in both oxidative and glycolytic activity. While NAMPT expression did not correlate with sensitivity to OT-82, low expression of NAPRT, an enzyme in a parallel NAD salvage pathway, appeared to be predictive of greater sensitivity to OT-82. Further, ES cells that expressed NAPRT could be fully rescued with addition of NA, the substrate of NAPRT, whereas low expressers could not. In vivo studies of the combination of OT-82 and irinotecan revealed enhanced antitumor activity. Studies of dosing schedule and tumor biology are ongoing and will be reported. OT-82 is an on-target NAMPTi that may be a novel targeted approach for the treatment of ES, especially in rational combinations.

Citation Format: Anna Gibson, Choh Yeung, Arnulfo Mendoza, Sameer Isaaq, Christine Heske. Evaluation of OT-82, a nicotinamide phosphoribosyltransferase inhibitor (NAMPTi), as a potential therapeutic option for Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3592.

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&lt;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&lt;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&lt;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 (&gt; 2-fold, p&lt;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&lt;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&lt;0.05). An in vivo spontaneous xenograft model showed that overexpression of CASZ1 significantly suppressed RD tumor growth (p&lt;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&lt;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.