Ipsilateral and Contralateral MRI Volumetric Abnormalities in Chronic Unilateral Temporal Lobe Epilepsy and their Clinical Correlates

PURPOSE

To assess the presence, extent, and clinical correlates of quantitative MR volumetric abnormalities in ipsilateral and contralateral hippocampus, and temporal and extratemporal lobe regions in unilateral temporal lobe epilepsy (TLE).

METHODS

In total, 34 subjects with unilateral left (n = 15) or right (n = 19) TLE were compared with 65 healthy controls. Regions of interest included the ipsilateral and contralateral hippocampus as well as temporal, frontal, parietal, and occipital lobe gray and white matter. Clinical markers of neurodevelopmental insult (initial precipitating insult, early age of recurrent seizures) and chronicity of epilepsy (epilepsy duration, estimated number of lifetime generalized seizures) were related to magnetic resonance (MR) volume abnormalities.

RESULTS

Quantitative MR abnormalities extend beyond the ipsilateral hippocampus and temporal lobe with extratemporal (frontal and parietal lobe) reductions in cerebral white matter, especially ipsilateral but also contralateral to the side of seizure onset. Volumetric abnormalities in ipsilateral hippocampus and bilateral cerebral white matter are associated with factors related to both the onset and the chronicity of the patients' epilepsy.

CONCLUSIONS

These cross-sectional findings support the view that volumetric abnormalities in chronic TLE are associated with a combination of neurodevelopmental and progressive effects, characterized by a prominent disruption in ipsilateral hippocampus and neural connectivity (i.e., white matter volume loss) that extends beyond the temporal lobe, affecting both ipsilateral and contralateral hemispheres.

Executive functioning in childhood epilepsy: parent-report and cognitive assessment

There is considerable interest in the assessment of executive function (EF) in pediatric clinical populations but only a few well-standardized measures exist. We examined EF in 53 children aged 8 to 18 years with recent onset epilepsy (31 males, 22 females) and 50 control children (23 males, 27 females) using the Behavior Rating Inventory of Executive Function (BRIEF) and the Delis-Kaplan Executive Function System (D-KEFS). Thirty children had localization-related epilepsy and 23 had idiopathic generalized epilepsy; average duration of 10 months (SD 4y 1mo) and onset age of 11 years 6 months (SD 3y 6mo). The study sample was characterized by good seizure control, with 40 participants taking one antiepileptic drug (AED), one taking two AEDs, and 12 not treated pharmacologically. Children with epilepsy showed greater executive difficulties on both measures than children in the control group. The BRIEF and D-KEFS were significantly correlated, and an 'at-risk' group identified from the BRIEF was more significantly impaired on the D-KEFS than a 'low risk' group. The BRIEF was also a better predictor of performance on the D-KEFS than the Child Behavior Checklist. These findings indicate that children with recent onset epilepsy show significant difficulties in E F, and demonstrate the utility of parent ratings (BRIEF) in the assessment of EF.

MRI volume loss of subcortical structures in unilateral temporal lobe epilepsy

Few studies have examined the relative degree of brain volume loss in both the hippocampi and subcortical structures in unilateral temporal lobe epilepsy (TLE) and their association with clinical seizure correlates. In this study, quantitative MRI volumes were measured in the hippocampus, thalamus, caudate, putamen, and corpus callosum in 48 patients with unilateral TLE (26 right, and 22 left) and compared with the volumes of 29 healthy controls. The ipsilateral hippocampus, corpus callosum, and bilateral thalami exhibited the greatest volume loss, reflected by large to moderate effect size differences compared with controls. Bilaterally, the putamen showed the next highest volume reduction. The contralateral hippocampus and bilateral caudate nuclei showed the least volume reduction, characterized by small effect sizes. Furthermore, clinical seizure characteristics (e.g., duration of epilepsy) exhibited different patterns of association with the volume reductions observed across these structures. Findings suggest that distinct neurodevelopmental features may play a role in the volume abnormality observed in these regions.

BJS commission on surgery and perioperative care post-COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) was declared a pandemic by the WHO on 11 March 2020 and global surgical practice was compromised. This Commission aimed to document and reflect on the changes seen in the surgical environment during the pandemic, by reviewing colleagues' experiences and published evidence.

METHODS

In late 2020, BJS contacted colleagues across the global surgical community and asked them to describe how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had affected their practice. In addition to this, the Commission undertook a literature review on the impact of COVID-19 on surgery and perioperative care. A thematic analysis was performed to identify the issues most frequently encountered by the correspondents, as well as the solutions and ideas suggested to address them.

RESULTS

BJS received communications for this Commission from leading clinicians and academics across a variety of surgical specialties in every inhabited continent. The responses from all over the world provided insights into multiple facets of surgical practice from a governmental level to individual clinical practice and training.

CONCLUSION

The COVID-19 pandemic has uncovered a variety of problems in healthcare systems, including negative impacts on surgical practice. Global surgical multidisciplinary teams are working collaboratively to address research questions about the future of surgery in the post-COVID-19 era. The COVID-19 pandemic is severely damaging surgical training. The establishment of a multidisciplinary ethics committee should be encouraged at all surgical oncology centres. Innovative leadership and collaboration is vital in the post-COVID-19 era.

Executive functioning in childhood epilepsy: parent-report and cognitive assessment

There is considerable interest in the assessment of executive function (EF) in pediatric clinical populations but only a few well-standardized measures exist. We examined EF in 53 children aged 8 to 18 years with recent onset epilepsy (31 males, 22 females) and 50 control children (23 males, 27 females) using the Behavior Rating Inventory of Executive Function (BRIEF) and the Delis-Kaplan Executive Function System (D-KEFS). Thirty children had localization-related epilepsy and 23 had idiopathic generalized epilepsy; average duration of 10 months (SD 4y 1mo) and onset age of 11 years 6 months (SD 3y 6mo). The study sample was characterized by good seizure control, with 40 participants taking one antiepileptic drug (AED), one taking two AEDs, and 12 not treated pharmacologically. Children with epilepsy showed greater executive difficulties on both measures than children in the control group. The BRIEF and D-KEFS were significantly correlated, and an 'at-risk' group identified from the BRIEF was more significantly impaired on the D-KEFS than a 'low risk' group. The BRIEF was also a better predictor of performance on the D-KEFS than the Child Behavior Checklist. These findings indicate that children with recent onset epilepsy show significant difficulties in E F, and demonstrate the utility of parent ratings (BRIEF) in the assessment of EF.

Effects of chicken slurry inclusion on apparent total tract macronutrient digestibility, palatability, and fecal characteristics, microbiota, and metabolites of healthy adult dogs

"Premium" pet foods are often formulated with meat slurries. Meat slurries are believed to be of higher quality than rendered meals, but inadequate research has been performed to test how their inclusion affects palatability, digestibility, or indicators of gastrointestinal health. Therefore, the objectives of this study were to determine how chicken slurry inclusion affected the palatability and apparent total tract digestibility (ATTD) of dog foods and to assess their effects on the fecal characteristics, metabolites, and microbiota of dogs. A replicated 3 × 3 Latin square design digestibility study was conducted using 9 healthy adult dogs (age = 5.44 ± 0.53 yr) to test diets containing 0% (control; CON), 8% (low inclusion; LOW), and 16% (high inclusion; HIGH) chicken slurry. The experiment comprised three 21-d experimental periods (14 d of adaptation, 5 d of total fecal collection (used for ATTD calculations), and 2 d of blood collection). On the first day of fecal collections, one fresh sample was collected for measurement of pH, dry matter (DM) content, fermentative metabolite concentrations, and microbiota populations. A 2-d palatability study (n = 20 dogs) was also conducted to compare CON vs. HIGH. Data were analyzed statistically by Mixed Models using SAS 9.4, with P < 0.05 being significant. In the palatability study, dogs were shown to prefer (P < 0.05) the HIGH diet by a ratio of 2:1. In the digestibility study, fecal output, scores, pH, and DM percentage were not different among diets. The ATTD of protein was higher (P < 0.05) for the HIGH diet (84.6%) than for the LOW (82.7%) or CON (82.6%) diets. The ATTD of other nutrients and energy were not different among diets (all over 80%). Fecal propionate, butyrate, and total short-chain fatty acid concentrations were higher (P < 0.05) in dogs fed the LOW diet (122.0, 67.4, and 408.2 μmol/g, respectively) than those fed the HIGH diet (89.0, 46.9, and 338.2 μmol/g, respectively). The other fecal metabolites (acetate, branched-chain fatty acids, ammonia, phenol, and indole) were not different among treatments. Few changes to the fecal microbiota were noted. However, the relative abundance of fecal Fusobacterium was higher (P < 0.05) in dogs fed the CON diet than those fed the HIGH diet (25.7% vs. 20.0% relative abundance). In summary, chicken slurry inclusion improved palatability but had minimal effects on nutrient digestibility and fecal characteristics, metabolites, and microbiota.

Effects of a mildly cooked human-grade dog diet on gene expression, skin and coat health measures, and fecal microbiota of healthy adult dogs

Purported benefits of human-grade pet foods include reduced inflammation, enhanced coat quality, and improved gut health, but research is scarce. Therefore, we compared gene expression, skin and coat health measures, and the fecal microbiome of dogs consuming a mildly cooked human-grade or extruded kibble diet. Twenty beagles (BW = 10.25 ± 0.82 kg; age = 3.85 ± 1.84 yr) were used in a completely randomized design. Test diets included: 1) chicken and brown rice recipe [feed-grade; extruded; blue buffalo (BB)]; and 2) chicken and white rice [human-grade; mildly cooked; Just Food for Dogs (JFFD)]. The study consisted of a 4-week baseline when all dogs ate BB, and a 12-week treatment phase when dogs were randomized to either diet (n = 10/group). After the baseline and treatment phases, fresh fecal samples were scored and collected for pH, dry matter (DM), and microbiome analysis; blood samples were collected for gene expression analysis; hair samples were microscopically imaged; and skin was analyzed for delayed-type hypersensitivity (DTH), sebum concentration, hydration status, and transepidermal water loss (TEWL). Data were analyzed as a change from baseline (CFB) using the Mixed Models procedure of SAS (version 9.4). At baseline, fecal pH was higher (P < 0.05) and hair surface score, superoxide dismutase (SOD) expression, and tumor necrosis factor-α (TNF-α) expression was lower (P < 0.05) in dogs allotted to JFFD. The decrease in CFB fecal pH and DM was greater (P < 0.05) in dogs fed JFFD, but fecal scores were not different. The increase in CFB hair surface score was higher (P < 0.05) in dogs fed JFFD. The decrease in CFB TEWL (back region) was greater (P < 0.05) in dogs fed JFFD, but TEWL (inguinal and ear regions), hydration status, and sebum concentrations in all regions were not different. Hair cortex scores and DTH responses were not affected by diet. The increase in CFB gene expression of SOD, COX-2, and TNF-α was greater (P < 0.05) in dogs fed JFFD. PCoA plots based on Bray-Curtis distances of bacterial genera and species showed small shifts over time in dogs fed BB, but dramatic shifts in those fed JFFD. JFFD increased (adj. P < 0.05) relative abundances of 4 bacterial genera, 11 bacterial species, 68 KEGG pathways, and 167 MetaCyc pathways, and decreased (adj. P < 0.05) 16 genera, 25 species, 98 KEGG pathways, and 87 MetaCyc pathways. In conclusion, the JFFD diet dramatically shifted the fecal microbiome but had minor effects on skin and coat measures and gene expression.

Activator Protein-1 (AP-1) Signaling Inhibits the Growth of Ewing Sarcoma Cells in Response to DNA Replication Stress

Ribonucleotide reductase (RNR) catalyzes the rate-limiting step in the synthesis of deoxyribonucleosides and is required for DNA replication. Multiple types of cancer, including Ewing sarcoma tumors, are sensitive to RNR inhibitors or a reduction in the levels of either the RRM1 or RRM2 subunits of RNR. However, the polypharmacology and off-target effects of RNR inhibitors have complicated the identification of the mechanisms that regulate sensitivity and resistance to this class of drugs. Consequently, we used a conditional knockout (CRISPR/Cas9) and rescue approach to target RRM1 in Ewing sarcoma cells and identified that loss of the RRM1 protein results in the upregulation of the expression of multiple members of the activator protein-1 (AP-1) transcription factor complex, including c-Jun and c-Fos, and downregulation of c-Myc. Notably, overexpression of c-Jun and c-Fos in Ewing sarcoma cells is sufficient to inhibit cell growth and downregulate the expression of the c-Myc oncogene. We also identified that the upregulation of AP-1 is mediated, in part, by SLFN11, which is a replication stress response protein that is expressed at high levels in Ewing sarcoma. In addition, small-molecule inhibitors of RNR, including gemcitabine, and histone deacetylase inhibitors, which reduce the level of the RRM1 protein, also activate AP-1 signaling and downregulate the level of c-Myc in Ewing sarcoma. Overall, these results provide novel insight into the critical pathways activated by loss of RNR activity and the mechanisms of action of inhibitors of RNR.

Significance

RNR is the rate-limiting enzyme in the synthesis of deoxyribonucleotides. Although RNR is the target of multiple chemotherapy drugs, polypharmacology and off-target effects have complicated the identification of the precise mechanism of action of these drugs. In this work, using a knockout-rescue approach, we identified that inhibition of RNR upregulates AP-1 signaling and downregulates the level of c-Myc in Ewing sarcoma tumors.

Standardized amino acid digestibility and nitrogen-corrected true metabolizable energy of frozen raw, freeze-dried raw, fresh, and extruded dog foods using precision-fed cecectomized and conventional rooster assays

Processing conditions, particularly temperature and duration of heating, impact pet food digestibility. Various commercial pet food formats are now available, but few have been tested thoroughly. The objective of this study was to determine the amino acid (AA) digestibilities and nitrogen-corrected true metabolizable energy (TMEn) values of frozen raw, freeze-dried raw, fresh (mildly cooked), and extruded dog foods using the precision-fed cecectomized and conventional rooster assays. The diets tested were Chicken and Barley Recipe [Hill's Science Diet, extruded diet (EXT)], Chicken and White Rice Recipe [Just Food for Dogs, fresh diet (FRSH)], Chicken Formula [Primal Pet Foods, frozen raw diet (FRZN)], Chicken and Sorghum Hybrid Freeze-dried Formula [Primal Pet Foods, hybrid freeze-dried raw diet (HFD)], and Chicken Dinner Patties [Stella & Chewy's, freeze-dried raw diet (FD)]. Two precision-fed rooster assays utilizing Single Comb White Leghorn roosters were conducted. Cecectomized roosters (n = 4/treatment) and conventional roosters (n = 4/treatment) were used to determine standardized AA digestibilities and TMEn, respectively. All roosters were crop intubated with 12 g of test diet and 12 g of corn, with excreta collected for 48 h. In general, FD had the highest, while EXT had the lowest AA digestibilities; however, all diets performed relatively well and few differences in AA digestibility were detected among the diets. Lysine digestibility was higher (P < 0.05) in FD and FRZN than EXT, with other diets being intermediate. Threonine digestibility was higher (P < 0.05) in FD than EXT, with other diets being intermediate. Digestibilities of the other indispensable AA were not different among diets. The reactive lysine:total lysine ratios were 0.94, 0.96, 0.93, 0.93, and 0.95 for EXT, FRSH, FRZN, HFD, and FD, respectively. TMEn was higher (P < 0.05) in FRZN than FD, FRSH, and EXT, higher (P < 0.05) in HFD than FRSH and EXT, and higher (P < 0.05) in FD than EXT. In conclusion, our results support the notion that AA digestibilities are affected by diet processing, with FD, HFD, FRZN, and FRSH diets having higher AA digestibility coefficients and greater TMEn values, than the EXT diet; however, other factors such as ingredient inclusion and macronutrient composition may also have affected these results. More research in dogs is necessary to test the effects of format on diet palatability, digestibility, stool quality, and other physiologically relevant outcomes.

A-143 Sorry, I Wasn’t Paying Attention. The Moderating Role of Auditory Attention on the Relationship between Age and Verbal Learning

Objective

Attentional difficulties are known to negatively impact learning (Hervey et al., 2004; Alderson et al., 2013). This study builds upon previous work examining the effect of sustained visual attention as a moderator of age and learning (Thomas et al., 2019) by examining performance on an auditory attention measure as a moderator of the relationship between age and performance on a verbal list-learning task.

Method

Archival data from 424 adults (Mage = 36.01, SD = 15.13) were collected at an outpatient clinic. Auditory attention was assessed via the Brief Test of Attention (BTA) raw score. Learning was assessed via the California Verbal Learning Test (CVLT-II) total T-Score (Trials 1–5).

Results

Results of a hierarchical linear regression indicated a significant effect between BTA and learning, (β = 0.287, F(1, 422) = 17.993, p &lt; 0.001, ΔR2 = 0.078). There was no significant effect between age and learning, (β = 0.022, F(1, 422) = 0.204, p = 0.652, ΔR2 = 0.000). Additional results from a simple moderated regression analysis indicated a significant overall model between age, learning and BTA (F(3, 420) = 15.749, p &lt; 0.001, ΔR2 = 0.1011) with BTA having a significant positive interaction effect on the relation between age and learning (β = 0.816, F(1, 420) = 10.436, p = &lt; 0.001, ΔR2 = 0.022).

Conclusion

Sustained attention has been shown to be an important consideration when assessing verbal learning and memory performance. Present results demonstrate that when accounting for age, auditory attention is a significant positive predictor of performance on measures of verbal learning. Additionally, confirming prior research, performances on auditory attention and verbal learning measures are positively correlated.

In vitro fermentation characteristics of acacia fiber using canine fecal inoculum

Acacia fiber is a highly concentrated source of soluble fiber extracted from the natural resin of acacia trees. This fiber is frequently utilized in the pet food industry as a processing aid to improve texture and stability. The objective of this study was to evaluate the fermentation characteristics of acacia fiber, inulin, pectin (positive control), and cellulose (negative control) using an in vitro fermentation system and canine fecal inoculum. Triplicate samples of each fiber were fermented for 0, 6, 12, and 18 h. Blank-corrected data were analyzed using PROC GLIMMIX of SAS to evaluate the effects of fiber, time, and fiber ×time interactions; significance was declared at P≤0.05. Significant fiber ×time interactions were observed for pH change, gas and short-chain fatty acid (SCFA) production, and microbiota populations. Pectin and inulin had greater (P<0.01) gas production than acacia fiber and cellulose. Inulin had the greatest (P<0.01) pH reduction, followed closely by pectin. Acacia fiber had a small reduction in pH, being lower (P<0.01) than cellulose after 18 h. Pectin and inulin had greater (P<0.01) acetate, propionate, butyrate, and total SCFA production than acacia fiber and cellulose. Acetate and total SCFA production were also greater (P<0.01) in acacia fiber than cellulose. Bacterial alpha diversity increased (P<0.01) during acacia fiber fermentation but decreased (P<0.01) during inulin fermentation. Beta diversity shifted over time and showed separate clustering of bacterial communities among the different fiber sources. The relative abundances of approximately 40 bacterial genera were affected by fiber ×time interactions. Specifically, acacia fiber had a greater (P<0.01) increase in Bacteroides, Faecalibacterium and Ruminococcus torques group abundance than other fibers. Inulin had a greater (P<0.01) increase in Prevotella, while pectin tubes had a greater (P<0.01) increase in Bifidobacterium than other fibers. Overall, the results of this study suggest that acacia fiber is a moderately fermentable fiber, producing low levels of gas and SCFA, increasing bacterial richness and diversity, and modifying several bacterial taxa. Although these data suggest beneficial responses in vitro, research in live animals is needed to confirm potential benefits in dogs.

Investigating temporal lobe contribution to confrontation naming using MRI quantitative volumetrics

Confrontation naming ability entails the operation of distinct cognitive operations and the integrity of a distributed neural network. Previous research has indicated a critical role for the left temporal lobe region in naming ability, but there is less agreement about the relative role of distinct temporal lobe regions. In the current paper, we used quantitative MR volumetrics to investigate the relative contribution of the hippocampus and extrahippocampal temporal lobe (segmented gray and white matter) volumes to confrontation naming performance in 53 patients with temporal lobe epilepsy. Findings showed (1) a stronger relationship for left temporal lobe volume than right temporal lobe volume in predicting naming performance; (2) both left temporal lobe white matter volume and left hippocampus volume contributed a significant amount of unique variance to spontaneous naming performance; and (3) left temporal lobe white matter volume but not left hippocampus volume predicted recognition naming performance.

Auranofin and reactive oxygen species inhibit protein synthesis and regulate the level of the PLK1 protein in Ewing sarcoma cells

Novel therapeutic approaches are needed for the treatment of Ewing sarcoma tumors. We previously identified that Ewing sarcoma cell lines are sensitive to drugs that inhibit protein translation. However, translational and therapeutic approaches to inhibit protein synthesis in tumors are limited. In this work, we identified that reactive oxygen species, which are generated by a wide range of chemotherapy and other drugs, inhibit protein synthesis and reduce the level of critical proteins that support tumorigenesis in Ewing sarcoma cells. In particular, we identified that both hydrogen peroxide and auranofin, an inhibitor of thioredoxin reductase and regulator of oxidative stress and reactive oxygen species, activate the repressor of protein translation 4E-BP1 and reduce the levels of the oncogenic proteins RRM2 and PLK1 in Ewing and other sarcoma cell lines. These results provide novel insight into the mechanism of how ROS-inducing drugs target cancer cells via inhibition of protein translation and identify a mechanistic link between ROS and the DNA replication (RRM2) and cell cycle regulatory (PLK1) pathways.

Apparent total tract nutrient digestibility of frozen raw, freeze-dried raw, fresh, and extruded dog foods and their effects on serum metabolites and fecal characteristics, metabolites, and microbiota of healthy adult dogs

Various pet food diet formats are available, but many are poorly studied. The objective of this study was to determine the apparent total tract macronutrient digestibility (ATTD) of frozen raw, freeze-dried raw, fresh, and extruded dog foods and assess their effects on serum metabolites, hematology, and fecal characteristics, metabolites, and microbiota of healthy adult dogs. Ten beagle dogs (4.10 ± 0.74 yr) were used in a replicated 5 × 5 Latin square study to test the following diets: Chicken and Barley Recipe (extruded; Hill's Science Diet [EXT]), Chicken and White Rice Recipe (fresh; Just Food for Dogs [FRSH]), Chicken Formula (frozen raw; Primal [FRZN]), Chicken and Sorghum Hybrid Freeze-dried Formula (freeze-dried raw; Primal [HFD]), and Chicken Dinner Patties (freeze-dried raw; Stella & Chewy's [FD]). The experiment was composed of five 35-d periods, with each ending with fecal and blood collections. Data were analyzed using Mixed Models in SAS 9.4, with P < 0.05 being significant. Treatment was a fixed effect and dog a random effect. Protein ATTD was higher for FRZN and FD than other diets and higher for HFD than FRSH and EXT. Fat ATTD was higher for HFD than FRZN and EXT and lower for EXT than other diets. Fecal output was higher for dogs fed EXT than those fed other diets and higher for dogs fed FRSH than those fed FRZN, HFD, or FD. Fecal pH was lower in dogs fed EXT and FRSH than those fed other diets. Fecal scores were higher (looser) in dogs fed EXT and FRSH than those fed FRZN and FD. Fecal dry matter was higher in dogs fed FD than those fed other diets and higher in those fed FRZN and HFD than those fed EXT and FRSH. In general, fecal short-chain fatty acids were highest in dogs fed EXT, intermediate in dogs fed FRSH and HFD, and lowest in dogs fed FRZN and FD. Fecal isobutyrate and isovalerate were highest in dogs fed HFD, lowest in dogs fed FRSH, and intermediate in dogs fed other diets. Fecal primary bile acids were higher, while secondary bile acids were lower in dogs fed FRSH than in dogs fed other diets. Fecal microbiota were greatly impacted by diet, with alpha diversity, beta diversity, and relative abundances of over 40 bacterial genera being different among treatments. This study shows that dietary format may lead to great differences in nutrient digestibility and fecal characteristics, metabolites, and microbiota. More research is needed to distinguish the effects of ingredient source, processing method, and nutrient composition.

Effects of corn protein inclusion on apparent total tract macronutrient digestibility, palatability, and fecal characteristics, microbiota, and metabolites of healthy adult dogs

Corn protein (CP), a co-product of the corn ethanol industry, is a sustainable protein source used in pet foods. The objectives of this study were to determine the palatability and apparent total tract digestibility (ATTD) of diets containing CP and to test the effects of CP-containing diets on the serum metabolites, hematology, and fecal characteristics, metabolites, and microbiota of healthy adult dogs. Ten female adult beagles (mean age: 6.12±1.39 yr; mean body weight: 9.33±1.04 kg) were used in a replicated 5x5 Latin square design (n=10/treatment). All dietary treatments were based on brewers rice, low-ash chicken byproduct meal, and chicken fat, and contained variable amounts of corn-based proteins: 0% (control), 15.3% corn gluten meal (CGM), 10.2% CGM + 5% CP (Low), 5.1% CGM + 10% CP (Medium), and 15% CP (High). The experiment was composed of five 28-day periods, with each consisting of a 22-day diet consumption period, a 5-day fecal collection period, and 1 day for blood collection. Data were analyzed statistically by Mixed Models using SAS 9.4, with P<0.05 accepted as being statistically significant. Two 2-day palatability studies (n=20 dogs) were also conducted to compare the High diet vs. control diet and High diet vs. CGM diet. Dogs were shown to prefer (P<0.05) the High diet over the control diet by a ratio of 1.8:1, but no preference was observed between the High and CGM diets. In the digestibility study, the ATTD of dry matter, organic matter, and energy increased (P<0.001) linearly with CP inclusion. The ATTD of fat was greater (P<0.001) for the control diet than for the CGM, Low, and High diets. Fecal scores were lower (P=0.05; firmer) and fecal dry matter percentage was higher (P<0.0001) in dogs fed CGM than those fed CP. Fecal phenol and indole, short-chain fatty acid, and branched-chain fatty acid concentrations were greater (P<0.05) in dogs fed CP than dogs fed CGM and control. Fecal bacterial diversity was not altered by diet, but the relative abundance of approximately 10 bacterial genera was altered by diet. In summary, our data demonstrate that the inclusion of CP in dog foods resulted in high diet palatability and macronutrient digestibility and altered microbial composition and activity.

Abstract 3532: Activator protein-1 (AP-1) signaling inhibits the growth of Ewing sarcoma cells in response to DNA replication stress

Ribonucleotide reductase (RNR) is the rate-limiting enzyme in the synthesis of deoxyribonucleoside triphosphates (dNTPs) and is required for DNA replication and the repair of DNA damage. Multiple types of cancer, including Ewing sarcoma tumors, are sensitive to RNR inhibitors or a reduction in the levels of either the RRM1 or RRM2 subunits of RNR. However, the polypharmacology and off-target effects of RNR inhibitors has complicated the identification of the precise mechanisms that regulate sensitivity and resistance to this class of drugs. Consequently, we used a conditional knockout (CRISPR/Cas9) and rescue approach to target RRM1 in Ewing sarcoma cells and identified that loss of RRM1 results in upregulation of the expression of multiple members of the activator protein-1 (AP-1) transcription factor complex, including c-Jun and c-Fos. This upregulation of AP-1 is mediated, in part, by SLFN11, which is expressed at high levels in Ewing sarcoma tumor and other pediatric sarcomas. Notably, the inducible expression of c-Jun and c-Fos in Ewing sarcoma cells impairs cell growth, downregulates the expression of the stem cell factor Sox2, and upregulates markers of cellular differentiation. In addition, small-molecule inhibitors of RNR, including gemcitabine and hydroxyurea, and HDAC inhibitors, which reduce the level of the RRM1 protein, also activate this AP-1 signaling pathway in Ewing sarcoma cells. Overall, these results provide novel insight into the critical pathways activated by loss of RNR activity and the mechanisms of action of inhibitors of RNR.

Citation Format: David Gordon, Emma Croushore, Stacia Koppenhafer, Kelli Goss, Elizabeth Geary. Activator protein-1 (AP-1) signaling inhibits the growth of Ewing sarcoma cells in response to DNA replication stress. [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 3532.

Auranofin and reactive oxygen species inhibit protein synthesis and regulate the level of the PLK1 protein in Ewing sarcoma cells

Novel therapeutic approaches are needed for the treatment of Ewing sarcoma tumors. We previously identified that Ewing sarcoma cell lines are sensitive to drugs that inhibit protein translation. However, translational and therapeutic approaches to inhibit protein synthesis in tumors are limited. In this work, we identified that reactive oxygen species, which are generated by a wide range of chemotherapy and other drugs, inhibit protein synthesis and reduce the level of critical proteins that support tumorigenesis in Ewing sarcoma cells. In particular, we identified that both hydrogen peroxide and auranofin, an inhibitor of thioredoxin reductase and regulator of oxidative stress and reactive oxygen species, activate the repressor of protein translation 4E-BP1 and reduce the levels of the oncogenic proteins RRM2 and PLK1 in Ewing and other sarcoma cell lines. These results provide novel insight into the mechanism of how ROS-inducing drugs target cancer cells via inhibition of protein translation and identify a mechanistic link between ROS and the DNA replication (RRM2) and cell cycle regulatory (PLK1) pathways.