A novel preclinical model of craniospinal irradiation in pediatric diffuse midline glioma demonstrates decreased metastatic disease.

Background: Diffuse midline glioma (DMG) is an aggressive pediatric central nervous system tumor with strong metastatic potential. As localized treatment of the primary tumor improves, metastatic disease is becoming a more important factor in treatment. We hypothesized that we could model craniospinal irradiation (CSI) through a DMG patient-derived xenograft (PDX) model and that CSI would limit metastatic tumor. Methods: We used a BT245 murine orthotopic DMG PDX model for this work. We developed a protocol and specialized platform to deliver craniospinal irradiation (CSI) (4 Gy x2 days) with a pontine boost (4 Gy x2 days) and compared metastatic disease by pathology, bioluminescence, and MRI to mice treated with focal radiation only (4 Gy x4 days) or no radiation. Results: Mice receiving CSI plus boost showed minimal spinal and brain leptomeningeal metastatic disease by bioluminescence, MRI, and pathology compared to mice receiving radiation to the pons only or no radiation. Conclusion: In a DMG PDX model, CSI+boost minimizes tumor dissemination compared to focal radiation. By expanding effective DMG treatment to the entire neuraxis, CSI has potential as a key component to combination, multimodality treatment for DMG designed to achieve long-term survival once novel therapies definitively demonstrate improved local control.

Surgical Management of Acute Abdomen in Adult Patients: Experience from a Private Hospital in Addis Ababa, Ethiopia.

Background: Acute abdomen is a major surgical problem in Ethiopia with surgery for acute abdominal conditions accounting for roughly one-third of total emergency operations in many centers. This study was conducted with the aim of studying the pattern and outcome of surgically managed acute abdominal cases in a private general hospital in Addis Ababa, Ethiopia. Methods: This was a retrospective cross-sectional study of acute abdominal cases in adult patients operated at Teklehaimanot General Hospital between January 1, 2018 and August 1, 2019. Results: A total of 267 patients' medical records were reviewed. The male to female ratio was 1.5:1 and majority of patients were between the age range of 20 to 40 years with mean age of 36±16 years. The average duration of symptoms before arrival was 71.1±84.4 hours (range 3 to 504 hours) and only 85 (31.8%) of patients reached to the Hospital within 24 hours or less of onset of symptoms. Acute appendicitis was the most common cause of acute abdomen; observed in 193 (72.3%) of the cases. Overall post-operative complication rate was 14.8% and post-operative mortality rate was 1.9%. It was found that delayed presentation (OR 2.01, 95% CI 1.64-7.84), old age (OR 1.51, 95% CI 1.89-3.59), and tachycardia at presentation (OR 2.85, 95% CI 1.03-6.82) were major predictors of morbidity and mortality in operated patients. Conclusion: In this study acute appendicitis accounted for the majority of cases operated for acute abdomen. Length of post-operative hospital stay, early post-operative complication rate, and overall mortality rate were found to be significantly lower in our series than other reports.

Comprehensive molecular characterization of pediatric radiation-induced high-grade glioma.

Radiation-induced high-grade gliomas (RIGs) are an incurable late complication of cranial radiation therapy. We performed DNA methylation profiling, RNA-seq, and DNA sequencing on 32 RIG tumors and an in vitro drug screen in two RIG cell lines. We report that based on DNA methylation, RIGs cluster primarily with the pediatric receptor tyrosine kinase I high-grade glioma subtype. Common copy-number alterations include Chromosome (Ch.) 1p loss/1q gain, and Ch. 13q and Ch. 14q loss; focal alterations include PDGFRA and CDK4 gain and CDKN2A and BCOR loss. Transcriptomically, RIGs comprise a stem-like subgroup with lesser mutation burden and Ch. 1p loss and a pro-inflammatory subgroup with greater mutation burden and depleted DNA repair gene expression. Chromothripsis in several RIG samples is associated with extrachromosomal circular DNA-mediated amplification of PDGFRA and CDK4. Drug screening suggests microtubule inhibitors/stabilizers, DNA-damaging agents, MEK inhibition, and, in the inflammatory subgroup, proteasome inhibitors, as potentially effective therapies.

Senescence Induced by BMI1 Inhibition Is a Therapeutic Vulnerability in H3K27M-Mutant DIPG.

Diffuse intrinsic pontine glioma (DIPG) is an incurable brain tumor of childhood characterized by histone mutations at lysine 27, which results in epigenomic dysregulation. There has been a failure to develop effective treatment for this tumor. Using a combined RNAi and chemical screen targeting epigenomic regulators, we identify the polycomb repressive complex 1 (PRC1) component BMI1 as a critical factor for DIPG tumor maintenance in vivo. BMI1 chromatin occupancy is enriched at genes associated with differentiation and tumor suppressors in DIPG cells. Inhibition of BMI1 decreases cell self-renewal and attenuates tumor growth due to induction of senescence. Prolonged BMI1 inhibition induces a senescence-associated secretory phenotype, which promotes tumor recurrence. Clearance of senescent cells using BH3 protein mimetics co-operates with BMI1 inhibition to enhance tumor cell killing in vivo.

Preclinical and clinical investigation of intratumoral chemotherapy pharmacokinetics in DIPG using gemcitabine.

BACKGROUND: Hundreds of systemic chemotherapy trials in diffuse intrinsic pontine glioma (DIPG) have not improved survival, potentially due to lack of intratumoral penetration, which has not previously been assessed in humans. METHODS: We used gemcitabine as a model agent to assess DIPG intratumoral pharmacokinetics (PK) using mass spectrometry. RESULTS: In a phase 0 clinical trial of i.v. gemcitabine prior to biopsy in children newly diagnosed with DIPG by MRI, mean concentration in 4 biopsy cores in patient 1 (H3K27M diffuse midline glioma) was 7.65 µM. These compare favorably to levels for patient 2 (mean 3.85 µM, found to have an H3K27-wildtype low-grade glioma on histology), and from a similar study in adult glioblastoma (adjusted mean 3.48 µM). In orthotopic patient-derived xenograft (PDX) models of DIPG and H3K27M-wildtype pediatric glioblastoma, gemcitabine levels and clearance were similar in tumor, pons, and cortex and did not depend on H3K27 mutation status or tumor location. Normalized gemcitabine levels were similar in patient 1 and the DIPG PDX. CONCLUSIONS: These findings, while limited to one agent, provide preliminary evidence for the hypotheses that lack of intratumoral penetration is not why systemic chemotherapy has failed in DIPG, and orthotopic PDX models can adequately model intratumoral PK in human DIPG.

Correction: BPTF regulates growth of adult and pediatric high-grade glioma through the MYC pathway.

The original version of this Article omitted the following from the Acknowledgements: This work was supported by the Luke's Army Pediatric Cancer Research Fund St. Baldrick's Scholar Award. This has now been corrected in both the PDF and HTML versions of the Article.

Exportin 1 Inhibition Induces Nerve Growth Factor Receptor Expression to Inhibit the NF-κB Pathway in Preclinical Models of Pediatric High-Grade Glioma.

High-grade glioma (HGG) is the leading cause of cancer-related death among children. Selinexor, an orally bioavailable, reversible inhibitor of the nuclear export protein, exportin 1, is in clinical trials for a range of cancers, including HGG. It inhibits the NF-κB pathway and strongly induces the expression of nerve growth factor receptor (NGFR) in preclinical cancer models. We hypothesized that selinexor inhibits NF-κB via upregulation of NGFR. In HGG cells, sensitivity to selinexor correlated with increased induction of cell surface NGFR expression. Knocking down NGFR in HGG cells increased proliferation, anchorage-independent growth, stemness markers, and levels of transcriptionally available nuclear NF-κB not bound to IκB-α, while decreasing apoptosis and sensitivity to selinexor. Increasing IκB-α levels in NGFR knockdown cells restored sensitivity to selinexor. Overexpression of NGFR using cDNA reduced levels of free nuclear NF-κB, decreased stemness markers, and increased markers of cellular differentiation. In all HGG lines tested, selinexor decreased phosphorylation of NF-κB at serine 536 (a site associated with increased transcription of proliferative and inflammatory genes). Because resistance to selinexor monotherapy occurred in our in vivo model, we screened selinexor with a panel of FDA-approved anticancer agents. Bortezomib, a proteasome inhibitor that inhibits the NF-κB pathway through a different mechanism than selinexor, showed synergy with selinexor against HGG in vitro Our results help elucidate selinexor's mechanism of action and identify NGFR as a potential biomarker of its effect in HGG and in addition suggest a combination therapy strategy for these challenging tumors.

BPTF regulates growth of adult and pediatric high-grade glioma through the MYC pathway.

High-grade gliomas (HGG) afflict both children and adults and respond poorly to current therapies. Epigenetic regulators have a role in gliomagenesis, but a broad, functional investigation of the impact and role of specific epigenetic targets has not been undertaken. Using a two-step, in vitro/in vivo epigenomic shRNA inhibition screen, we determine the chromatin remodeler BPTF to be a key regulator of adult HGG growth. We then demonstrate that BPTF knockdown decreases HGG growth in multiple pediatric HGG models as well. BPTF appears to regulate tumor growth through cell self-renewal maintenance, and BPTF knockdown leads these glial tumors toward more neuronal characteristics. BPTF's impact on growth is mediated through positive effects on expression of MYC and MYC pathway targets. HDAC inhibitors synergize with BPTF knockdown against HGG growth. BPTF inhibition is a promising strategy to combat HGG through epigenetic regulation of the MYC oncogenic pathway.

Preclinical analysis of MTOR complex 1/2 inhibition in diffuse intrinsic pontine glioma.

Diffuse intrinsic pontine glioma (DIPG) is an incurable childhood brain tumor. The mechanistic target of rapamycin (MTOR), a key oncogene, functions as two distinct signaling complexes, MTORC1 and MTORC2. We set out to determine the preclinical efficacy and mechanism of action of MTOR inhibitors in DIPG. We evaluated the MTORC1 inhibitor everolimus and the MTORC1/2 inhibitor AZD2014 in three patient-derived DIPG cell lines using cell culture models. We created dose-response curves for both compounds. We measured phenotypic effects on cell self-renewal, apoptosis, cell cycle, differentiation, senescence, and autophagy. We assessed the effects of each compound on the AKT pathway. Finally, we measured the efficacy of AZD2014 in combination with radiation therapy (RT) and a panel of FDA-approved chemotherapy drugs. While everolimus showed minimal antitumor efficacy, AZD2014 revealed IC50 levels of 410-552 nM and IC90 levels of 1.30-8.86 µM in the three cell lines. AZD2014 demonstrated increased inhibition of cell self-renewal compared to everolimus. AZD2014 decreased expression of phospho-AKT, while no such effect was noted with everolimus. Direct AKT inhibition showed similar efficacy to AZD2014, and induction of constitutive AKT activity rescued DIPG cells from the effects of AZD2014. AZD2014 exhibited synergistic relationships with both RT and various chemotherapy agents across classes, including the multikinase inhibitor ponatinib. MTORC1/2 inhibition shows antitumor activity in cell culture models of DIPG due to the effect of MTORC2 inhibition on AKT. This strategy should be further assessed for potential incorporation into combinatorial approaches to the treatment of DIPG.