TMET-09. LOSS OF MAT2A COMPROMISES METHIONINE METABOLISM AND REPRESENTS A VULNERABILITY IN H3K27M MUTANT GLIOMAS

H3K27-mutant diffuse midline gliomas (DMGs) are defined as grade IV tumors by the World Health Organization. DMGs are inoperable and resistant to chemo/radio therapies. Median survival ranges from 8-11 months, with 2% of patients surviving beyond 5 years. H3K27M mutations lead to global epigenetic and transcriptional reprogramming driven by global loss of negative transcriptional regulator H3K27 trimethylation (H3K27me3). Loss of H3K27me3 is an initiating event in gliomagenesis. This disease lacks appropriate models to predict disease biology and response to treatment. Therefore, we developed a novel syngeneic H3K27M mouse model. An unbiased integrated systems biology approach identified that H3K27M but not isogenic controls relied on the amino acid methionine and the enzyme Methionine Adenosyltransferase 2A (MAT2A). MAT2A is a central regulator of one-carbon metabolism by converting methionine to S-adenosylmethionine (SAM), the universal methyl-donor for protein and nucleotide methylation reactions. In complementary genetic approaches, we applied these findings to patient-derived cell lines with the H3K27M mutation. We hypothesize that MAT2A abrogation, genetic/pharmacological, would alter DMG viability by disrupting the methylome. The current MAT2A sensitivity paradigm is based on Methylthioadenosine Phosphorylase (MTAP) deletion through a synthetic lethal mechanism. We provide a novel mechanism whereby H3K27M cells are sensitive to MAT2A loss, independent of MTAP and through Adenosylmethionine Decarboxylase 1 (AMD1) overexpression disrupting MAT2A regulation. This results in H3K27M cells having lower MAT2A protein levels, conferring a sensitivity by inhibiting residual MAT2A. Genetic/pharmacological aberrations to MAT2A resulted in reduced proliferation. Parallel H3K36me3 ChIP and RNA-sequencing identified loss of oncogenic and developmental transcriptional programs associated with MAT2A loss. In vivo syngeneic and patient-derived xenograft models with both inducible MAT2A knockdown or methionine restricted diets showed extended survival. These results suggest novel interactions between methionine metabolism and the epigenome of H3K27M gliomas and provide evidence that MAT2A, presents exploitable therapeutic vulnerabilities in histone mutant gliomas.

TMIC-49. CHITINASE-3-LIKE 1 PROTEIN COMPLEXES REGULATE PD-1 SIGNALING-MEDIATED IMMUNOSUPPRESSION IN GLIOBLASTOMA

Glioblastoma (GBM), the most common and lethal brain tumor with a median survival rate of only 15 months, remains largely incurable despite intensive multimodal treatment, including immunotherapeutic strategies being tested in clinical trials. GBM is highly immunosuppressive and resistant to immunotherapy because glioma cells escape from effective antitumor immunity through programing the tumor microenvironment (TME). Owing to the tremendous heterogeneity and plasticity of tumor cells and the surrounding TME, understanding the mechanisms of immune evasion by GBM remains elusive. We have recently discovered that the Chitinase-3-like-1 (CHI3L1)-Galectin-3 (Gal3) protein binding complex can selectively promote tumor-associated macrophage migration and infiltration with a protumor M2-like phenotype and T cell-mediated immunosuppression, which are governed by a transcriptional program of NF-κB/CEBPβ in the CHI3L1/Gal3-PI3K/AKT/mTOR axis. The immunoprecipitation coupled to liquid chromatography-mass spectrometry analysis revealed that galectin 3–binding protein (Gal3BP) competes with Gal3 to bind with CHI3L1 for negative regulation of the CHI3L1-Gal3 mediated processes. Interestingly, a newly-developed Gal3BP mimetic peptide can disrupt CHI3L1-Gal3 interaction, resulting in decreasing migration of M2-like bone marrow-derived macrophages (BMDMs), increasing CD8+ T cell infiltration, reversing immunosuppression, and inhibiting tumor progression in vitro and in vivo. Analyzing PD-1 signaling activation, we found that the Gal3BP mimetic peptide significantly decreased PD-L1 expression in tumor cells. Correlation analysis showed that CHI31L and Gal3 (encoded by LGALS3 gene) are significantly associated with both PD-L1 and PD-L2 in GBM patient samples. Furthermore, overexpression of CHI3L1 increased expression levels of PD-L1 and PD-L2, and CHI3L1 deletion decreased their expression in GBM patient-derived neurosphere lines. The treatment with recombinant CHI3L1 protein significantly increased PD-L1 and PD-L2 expression in M2-like BMDMs (with high levels of endogenous Gal3). Collectively, these data suggest that CHI3L1 protein complexes control the GBM immunosuppressive microenvironment by PD-1/PD-L1/PD-L2 signaling, providing new immunotherapeutic strategies for this brain cancer.

EXTH-79. HIJACKING A NEURODEVELOPMENTAL EPIGENOMIC PROGRAM IN METASTATIC DISSEMINATION OF MEDULLOBLASTOMA

Normal brain development relies on precise genetic and epigenetic spatiotemporal regulation of gene expression. How dysregulation of neurodevelopment relates to medulloblastoma, the most common pediatric brain tumor, remains elusive. Here, we uncovered a novel neurodevelopmental epigenomic program that regulates Purkinje cell migration in developing cerebellum is hijacked to induce tumor metastatic dissemination in medulloblastoma. Integrating publicly available datasets with our in-house data, unsupervised analyses revealed that BAF60C/SMARCD3, a subunit of SWI/SNF chromatin remodeling complex, promotes tumor cell migration in vitro and metastasis in vivo. Based on analyzing the single-cell RNAseq data of cerebellum developmental trajectory in mice and humans, aligning with the medulloblastoma patients’ datasets, we found that BAF60C/SMARCD3 regulated DAB1-mediated Reelin signaling is involved in Purkinje cell positioning during cerebellum development and medulloblastoma metastasis by orchestrating the cis-regulatory elements (CREs) at the DAB1 gene locus. Moreover, analysis of spatiotemporal gene expression and chromatin architecture in the human and mouse cerebellum demonstrated that transcription activity of the BAF60C/SMARCD3-DAB1 circuit is downregulated in a mature state of cerebellar development, however, is upregulated in metastatic medulloblastoma. We further identified that a core set of transcription factors, enhancer of zeste homolog 2 (EZH2) and nuclear factor I X (NFIX), bi-directionally control BAF60C/SMARCD3 transcriptional regulation by coordinating with the CREs at the BAF60C/SMARCD3 gene locus to form a chromatin hub during developing cerebellar development and medulloblastoma metastatic dissemination. Highly expressed BAF60C/SMARCD3 activates the Reelin/DAB1 signaling pathway downstream Src kinase, which was validated in the pair-wised primary and metastatic tumors from medulloblastoma patients. Preclinical medulloblastoma mouse models revealed that inhibiting Src activity reduces tumor cell migration and metastatic dissemination at a lower and safe dose. Together, these data deepen our understanding of how the developmental program influences disease progression and provide an opportunity for the development of therapeutics for this devastating brain cancer in children.

The effects of ALDH2 Glu487Lys polymorphism on vasovagal syncope patients undergoing head-up tilt test supplemented with sublingual nitroglycerin

Background and objective

Head-up tilt test (HUTT) is clinically advantageous for diagnosing patients with vasovagal syncope (VVS). Nitroglycerin is mainly used as a stimulant during HUTT, and mitochondrial aldehyde dehydrogenase 2 (ALDH2) is involved in the metabolism of nitroglycerin (NTG). ALDH2 Glu487Lys polymorphism (ALDH2 rs671) is the most common variant in the East Asian population. This study aimed to assess the effects of ALDH2 rs671 on VVS patients undergoing HUTT supplemented with sublingual NTG (HUTT-NTG). 

Methods

Patients with recurrent VVS (at least 2 times) who were admitted to the syncope center of our hospital were enrolled. All VVS patients have undergone HUTT. The polymorphism of Glu487Lys gene of ALDH2 was measured by the DNA Microarray Chip Method. The results of HUTT-NTG of VVS patients with different ALDH2 genotypes were compared and their hemodynamic characteristics were assessed.

Results

A total of 199 VVS patients were enrolled, including 101 patients in the ALDH2*1/*1 group and 98 patients in the ALDH2*2 group. Among patients undergoing HUTT-NTG, 70.3% of patients in the ALDH2*1/*1 group and 68.4% of patients in the ALDH2*2 group were positive, and the difference between the two groups was not statistically significant (P = 0.77). The proportions of VASIS I, VASIS II, and VASIS III were 40.6%, 8.9%, and 20.8% in the ALDH2*1/*1 group, respectively, and the corresponding proportions in the ALDH2*2 group were 36.7%, 11.2%, and 20.4%, respectively. There was no statistically significant difference between the two groups (P = 0.91). The hemodynamic characteristics of different genotypes in VVS patients undergoing HUTT-NTG were compared, and no statistically significant difference was found. The median time of syncopal episode occurred after NTG administration in the ALDH2*1/*1 group was 6 min (interquartile range [IQR]: 5.0–9.0), and it was 6.0 min in the ALDH2*2 group (IQR: 4.25–8.0, P = 0.64).

Conclusion

ALDH2 Glu487Lys polymorphism did not affect the outcome of VVS patients undergoing HUTT-NTG, and no significant change in the hemodynamic characteristics of different genotypes was found.

[Mid-term efficacy of China Net Childhood Lymphoma-mature B-cell lymphoma 2017 regimen in the treatment of pediatric Burkitt lymphoma]

Objective: To analyze the clinical characteristics of children with Burkitt lymphoma (BL) and to summarize the mid-term efficacy of China Net Childhood Lymphoma-mature B-cell lymphoma 2017 (CNCL-B-NHL-2017) regimen. Methods: Clinical features of 436 BL patients who were ≤18 years old and treated with the CNCL-B-NHL-2017 regimen from May 2017 to April 2021 were analyzed retrospectively. Clinical characteristics of patients at disease onset were analyzed and the therapeutic effects of patients with different clinical stages and risk groups were compared. Survival analysis was performed by Kaplan-Meier method, and Cox regression was used to identify the prognostic factors. Results: Among 436 patients, there were 368 (84.4%) males and 68 (15.6%) females, the age of disease onset was 6.0 (4.0, 9.0) years old. According to the St. Jude staging system, there were 4 patients (0.9%) with stage Ⅰ, 30 patients (6.9%) with stage Ⅱ, 217 patients (49.8%) with stage Ⅲ, and 185 patients (42.4%) with stage Ⅳ. All patients were stratified into following risk groups: group A (n=1, 0.2%), group B1 (n=46, 10.6%), group B2 (n=19, 4.4%), group C1 (n=285, 65.4%), group C2 (n=85, 19.5%). Sixty-three patients (14.4%) were treated with chemotherapy only and 373 patients (85.6%) were treated with chemotherapy combined with rituximab. Twenty-one patients (4.8%) suffered from progressive disease, 3 patients (0.7%) relapsed, and 13 patients (3.0%) died of treatment-related complications. The follow-up time of all patients was 24.0 (13.0, 35.0) months, the 2-year event free survival (EFS) rate of all patients was (90.9±1.4) %. The 2-year EFS rates of group A, B1, B2, C1 and C2 were 100.0%, 100.0%, (94.7±5.1) %, (90.7±1.7) % and (85.9±4.0) %, respectively. The 2-year EFS rates was higher in group A, B1, and B2 than those in group C1 (χ²=4.16, P=0.041) and group C2 (χ²=7.21, P=0.007). The 2-year EFS rates of the patients treated with chemotherapy alone and those treated with chemotherapy combined with rituximab were (79.3±5.1)% and (92.9±1.4)% (χ²=14.23, P<0.001) respectively. Multivariate analysis showed that stage Ⅳ (including leukemia stage), serum lactate dehydrogenase (LDH)>4-fold normal value, and with residual tumor in the mid-term evaluation were risk factors for poor prognosis (HR=1.38,1.23,8.52,95%CI 1.05-1.82,1.05-1.43,3.96-18.30). Conclusions: The CNCL-B-NHL-2017 regimen show significant effect in the treatment of pediatric BL. The combination of rituximab improve the efficacy further.

Polarized macrophages promote gestational beta cell growth through extracellular signal-regulated kinase 5 signalling

AIM

To show that depletion of pancreatic macrophages impairs gestational beta cell proliferation and leads to glucose intolerance.

MATERIALS AND METHODS

Genetic animal models were applied to study the effects of depletion of pancreatic macrophges on gestational beta-cell proliferaiton and glucose response. The crosstalk between macrophages and beta-cells was studied in vivo using beta-cell-specific extracellular-signal-regulated kinase 5 (ERK5) knockout and epidermal growth receptor (EGFR) knockout mice, and in vitro using a co-culture system.

RESULTS

Beta cell-derived placental growth factor (PlGF) recruited naïve macrophages and polarized them towards an M2-like phenotype. These macrophages then secreted epidermal growth factor (EGF), which activated extracellular signal-regulated kinase 5 (ERK5) signalling in beta cells to promote gestational beta cell proliferation. On the other hand, activation of ERK5 signalling in beta cells likely, in turn, enhanced the production and secretion of PlGF by beta cells.

CONCLUSIONS

Our study shows a regulatory loop between macrophages and beta cells through PlGF/EGF/ERK5 signalling cascades to regulate gestational beta cell growth.

Self-compression of stimulated Raman backscattering by a flying focus

The regime of self-compression has been proposed for plasma-based backward Raman amplification upon a flying focus. By using a pumping focus moving with a speed equal to the group velocity of stimulated Raman backscattering (SRBS), only a short part of SRBS which always synchronizes with the flying focus can be amplified. Therefore, instead of a short pulse, plasma noise or a long pulse can seed the BRA amplifiers. Here we demonstrate the regime by 2D particle-in-cell simulations, showing that the pump pulse is compressed from 26 ps to 116 fs, with an output amplitude comparable with the case of a well-synchronized short seed. As only one laser pulse is used in the simulation, the results present a significant path to simplify the Raman amplifiers.

[Analysis of clinical features and poor prognostic factors of acute hematogenous osteomyelitis in children]

Objective: To analyze the clinical characteristics, pathogenic bacteria, complications and risk factors of prognosis of acute hematogenous osteomyelitis in children. Methods: The clinical manifestations, laboratorg tests, etiological charateristics and clinical data of 107 patients with acute hematogenous osteomyelitis admitted to Beijing Children's Hospital from January 2017 to December 2020 were retrospectively analyzed. According to the drug sensitivity results of Staphylococcus aureus, the group was divided into methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) group; according to the presence or absence of complications, the group was divided into the group with and without complications; according to the prognosis of the follow-up children, the group was divided into good prognosis and poor prognosis. The χ² test or Mann-Whitney U test used for comparison between groups, and Logistic regression was used to analyze the risk factors for complications and prognosis. Results: Of the 107 patients, 62 were males and 45 were females. The age of presentation was 5.6 (1.7, 10.0) years, including 5 patients (4.7%) age from >28 days to 3 months, 46 patients (43.0%) age from >3 months to 5 years, 43 patients (40.2%)>5-12 years of age, and 13 patients (12.1%)>12-18 years of age. The first symptoms were acute fever in 35 patients (32.7%), limb pain in 24 patients (22.4%), and fever with limb pain in 23 patients (21.5%). Pathogen culture was positive in 75 patients (70.1%), Streptococcus pyogenes, Salmonella enterica and Escherichia coli in 1 case (1.4%) each, and Staphylococcus aureus in 72 cases (96.0%), among them, 47 cases were MSSA, 22 cases were MRSA, and 3 cases had positive reports of Staphylococcus aureus from other hospitals without drug-sensitive tests. The proportion of infected children living in rural areas and receiving surgical treatment was higher in the MRSA group than in the MSSA group (14 cases (63.6%) vs. 18 cases (38.3%) and 21 cases (95.5%) vs. 33 cases (70.2%), χ²=3.87, 4.23, both P<0.05). Sixty-five children had no complications while 42 children (39.3%) suffered from complications. Common complications consisted of 19 cases (17.8%) of sepsis, 17 cases (15.9%) of septic arthritis, and 12 cases (11.2%) of venous thrombosis. The group with complications showed higher mental changes, decreased appetite and (or) weakness, positive pathogenic cultures, and time from admission to surgery than the group without complications (18 cases (42.9%) vs. 9 cases (13.8%), 20 cases (47.6%) vs. 12 cases (18.5%), 34 cases (81.0%) vs. 41 cases (63.1%), 3.5 (2.0, 6.0) vs. 2.0 (1.0, 4.0) d,χ²=11.38, 10.35, 3.89, Z=2.21, all P<0.05). The poor prognosis group had more comorbidities, combined local complications, and positive aureus than the good prognosis group (10/15 vs. 34.9% (30/86), 7/15 vs. 17.4% (15/86), 14/15 vs. 61.6% (53/86), χ²=5.39, 6.40, 4.42, all P<0.05). Multifactorial Logistic regression analysis showed that acute phase C-reactive protein (CRP) was both an independent risk factor for complications (OR=1.01, 95%CI 1.01-1.02) and an independent risk factor for poor prognosis (OR=1.01, 95%CI 1.00-1.02). Conclusions: The first symptoms of acute hematogenous osteomyelitis are acute fever, limb pain, and fever with limb pain are most common. Staphylococcus aureus is the most common pathogenic organism. Those with loss of appetite and (or) weakness, mental changes, positive pathogenic cultures, and longer time between admission and surgery are prone to complications. Those with complications, combined local complications, and positive for Staphylococcus aureus had a poor prognosis. Elevated CRP is an independent risk factor not only for complications but for poor prognosis as well.

MEDB-88. BAF60C/SMARCD3-mediated novel neurodevelopmental epigenomic program promotes metastatic dissemination in medulloblastoma

Normal brain development relies on precise genetic and epigenetic spatiotemporal regulation of gene expression. How dysregulation of neurodevelopment relates to medulloblastoma, the most common pediatric brain tumor, remains elusive. Here, we uncovered a novel neurodevelopmental epigenomic program that regulates Purkinje cell migration in developing cerebellum is hijacked to induce tumor metastatic dissemination in medulloblastoma. Integrating publicly available datasets with our in-house data, unsupervised analyses revealed that BAF60C/SMARCD3, a subunit of SWI/SNF chromatin remodeling complex, promotes tumor cell migration in vitro and metastasis in vivo. Based on analyzing the single-cell RNAseq data of cerebellum developmental trajectory in mice and humans, aligning with the medulloblastoma patients’ datasets, we found that BAF60C/SMARCD3 regulated DAB1-mediated Reelin signaling is involved in Purkinje cell positioning during cerebellum development and medulloblastoma metastasis by orchestrating the cis-regulatory elements (CREs) at the DAB1 gene locus. Analysis of spatiotemporal gene expression and chromatin architecture in the human and mouse cerebellum demonstrated that transcription activity of the BAF60C/SMARCD3-DAB1 circuit is downregulated in a mature state of cerebellar development, however, is upregulated in metastatic medulloblastoma. We further identified that a core set of transcription factors, enhancer of zeste homolog 2 (EZH2) and nuclear factor I X (NFIX), bi-directionally control BAF60C/SMARCD3 transcriptional regulation by coordinating with the CREs at the BAF60C/SMARCD3 gene locus to form a chromatin hub during developing cerebellar development and medulloblastoma metastatic dissemination. Highly expressed BAF60C/SMARCD3 activates the Reelin/DAB1 signaling pathway downstream Src kinase, which was validated in the pair-wised primary and metastatic tumors from medulloblastoma patients. Preclinical medulloblastoma mouse models revealed that inhibiting Src activity reduces tumor cell migration and metastatic dissemination at a lower and safe dose. Together, these data deepen our understanding of how the developmental program influences disease progression and provide an opportunity for the development of therapeutics for this devastating brain cancer in children.

POS0750 THE STATUS OF BREGS AND BREG-RELATED CYTOKINES IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS

Background

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease which involves in multiple tissue and organ injury. Regulatory B cells (Bregs) are unique subpopulations of B cells with immune-regulating properties. Interestingly, different subsets of Bregs have distinct markers and phenotypes and participate in self immune regulation by different ways. However, the level of Bregs in SLE remains debated.

Objectives

This study aims to clarify the proportions of Bregs with special controversial cellular markers and Breg-related cytokines in SLE patients.

Methods

We explored the proportion of Bregs and Breg-related cytokines (IL-10) in SLE patients by searching literature through November 2021 from CBM, CNKI, China Science and Technology Journal Database, Wan Fang Data, PubMed, Embase, Web of Science, Cochrane Library and Medline. Random effects model was used to pool data. Heterogeneity and risk of bias was examined with I-squared index (I2) statistic. Inconsistency was evaluated by using the I2 and Egger tests were used for the evaluation of potential publication bias (STATA v.12.0).

Results

Total 14 case-control studies involving 489 PsA patients and 330 healthy controls (HCs) were included in this study (Table 1). No significant difference in the proportions of Bregs was evident between SLE patients and HCs［SMD=0.067, 95%CI (-0.924,1.059), P=0.894]. Because of a significant statistical heterogeneity observed [I2=97.1%, p<0.001], we conducted sub-analyses based on individual definitions of Bregs. We found the proportions of CD19+CD24hiCD38hi Breg cells was significantly increased in SLE [SMD=0.902, 95%CI (0.157,1.647), P<0.001](Figure 1A). The level of serum IL-10 was increased in SLE compared to that of HCs [SMD=1.062, 95%CI (0.754,1.370), P<0.001] with no publication bias based on the Egger tests (t=0.91, P=0.366)(Figure 1B).

Table 1.

Characteristics of the individual studies included in the meta-analysis.

AuthorPublish YearEIaQbCase NumbersBreg’s definitionMean % of Breg (mean(or median)±SD)% of Breg among PBMC/CD19+T cellsSLEHCBlair,P.A2010462514CD19+CD24hiCD38hiSLE: 13.9±5.21PBMCHC: 9.02±2.71Wang,T.2017475635CD19+CD24hiCD38hiSLE: 39.83±21.39PBMCHC: 8.74±3.97Wang,H.2019463630CD19+CD24hiCD38hiSLE: 12.94±5.45PBMCHC: 5.64±3.13Simon,Q2016461633CD19+CD24hiCD38hiSLE: 17.9±7.2PBMCHC: 11.65±4.01Zhuo-long Wang2018462830CD19+CD24hiCD38hiSLE: 3.62±1.25PBMCHC: 4.07±1.48Heinemann,K.2016463321CD19+CD24hiCD38hiSLE: 1.6±2.6PBMCHC: 1.5±1.1Chu,M.2015474332CD19+CD24highCD27+SLE: 8.39±7.22PBMCHC: 26.58±8.96Vadasz,Z.2015462120CD19+CD25hiFoxP3hiSLE: 18.5±3.05PBMCHC: 11±1.65Cai,X.2015476020CD19+CD5+SLE: 1.86±0.8PBMCHC: 4.35±1Yang,X.2014473015CD19+CD5+CD1dhiSLE: 4±1.57PBMCHC: 1.63±0.99Shan-feng Liu2015461010CD19+CD5+CD1dhiSLE: 0.83±0.28CD19+B cellHC: 0.2±0.21Zhong-wei Huang2014453430CD19+CD5+CD1dhiSLE: 7.86±4.1PBMCHC: 22.71±9.17Ye, Z.2019464720CD19+IL-10+SLE: 0.1±2.78CD19+B cellHC: 4.85±4.54Rong-wei Zhang2016465020CD19+IL-35+SLE: 1.77±0.79PBMCHC: 4.24±1.11

SLE: systemic lupus erythematosus. aEvidence level (EL) of each study was based on Oxford Center for Evidence-Based Medicine 2011. bQuality (Q) of each study was based on the Newcastle-Ottawa Quality Assessment Scale case.

Figure 1.

Conclusion

The levels of CD19+CD24hiCD38hi Bregs and IL-10 were significantly increased in SLE patients, suggesting that the abnormalities of Bregs numbers and function are the critical causes in the development of SLE.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 82001740).

Disclosure of Interests

None declared

Loss of MAT2A compromises methionine metabolism and represents a vulnerability in H3K27M mutant glioma by modulating the epigenome

Diffuse midline gliomas (DMGs) bearing driver mutations of histone 3 lysine 27 (H3K27M) are incurable brain tumors with unique epigenomes. Here, we generated a syngeneic H3K27M mouse model to study the amino acid metabolic dependencies of these tumors. H3K27M mutant cells were highly dependent on methionine. Interrogating the methionine cycle dependency through a short-interfering RNA screen identified the enzyme methionine adenosyltransferase 2A (MAT2A) as a critical vulnerability in these tumors. This vulnerability was not mediated through the canonical mechanism of MTAP deletion; instead, DMG cells have lower levels of MAT2A protein, which is mediated by negative feedback induced by the metabolite decarboxylated S-adenosyl methionine. Depletion of residual MAT2A induces global depletion of H3K36me3, a chromatin mark of transcriptional elongation perturbing oncogenic and developmental transcriptional programs. Moreover, methionine-restricted diets extended survival in multiple models of DMG in vivo. Collectively, our results suggest that MAT2A presents an exploitable therapeutic vulnerability in H3K27M gliomas.

N(6)-methyladenosine RNA methyltransferase like 3 inhibits extracellular matrix synthesis of endplate chondrocytes by downregulating sex-determining region Y-Box transcription factor 9 expression under tension

OBJECTIVE

Tension stimulation is an important inducer of endplate cartilage degeneration, but the specific regulatory mechanism remains unclear. This study was the first to reveal the mechanism by which methyltransferase-like 3 (METTL3)-mediated N(6)-methyladenosine (m6A) modification affected the extracellular matrix anabolism by tension-induced endplate chondrocytes.

METHOD

We examined the differences in METTL3 expression and m6A methylation levels in human endplate chondrocytes and human cartilage endplate tissues under in vitro tension. The effect on endplate cartilage degeneration was evaluated by manipulating m6A methylation mediated by METTL3 in vivo and in vitro. The effect of METTL3-mediated m6A methylation on the stability of sex-determining region Y-box transcription factor 9 (SOX9) gene expression was determined experimentally.

RESULTS

METTL3 expression and m6A methylation levels were significantly increased in degenerative human endplate cartilage tissue. Similarly, tension stimulation inhibited the ability of human endplate chondrocytes to synthesize extracellular matrix, which was accompanied by an increase in METTL3-mediated m6A methylation. The ability of endplate chondrocytes to resist tension was significantly enhanced by inhibiting METTL3 expression and subsequently downregulating m6A methylation in vitro and in vivo, thereby reducing intervertebral disc degeneration. Furthermore, METTL3 mediated SOX9 RNA methylation and disrupted SOX9 mRNA stability, thereby inhibiting the gene expression of the downstream collagen type II alpha 1 chain.

CONCLUSION

Tension stimulation downregulated SOX9 expression through METTL3-mediated m6A methylation, thereby inhibiting the synthesis of extracellular matrix in endplate chondrocytes.

[CT-based morphological and hemodynamics analysis for rupture risk of mirror intracranial aneurysm]

Objective: To compare the morphological and hemodynamic features of mirror intracranial aneurysms (MIAs) on CT angiography (CTA), and to elucidate the rupture risk factors of MIAs. Methods: This study retrospectively collected 29 patients with 58 digital subtraction angiography (DSA) or surgically confirmed MIAs from January 2010 to December 2016 in Jinling Hospital, Medical School of Nanjing University. Among them, there are 6 males and 23 females, aged from 40 to 83 (61±11) years old. Based on the results of hemorrhagic manifestation, 58 MIAs were divided as the ruptured (n=29) group and unruptured group (n=29). In addition, according to the location of aneurysms, they were further divided into the subgroup of posterior communicating MIAs (n=32) and non-posterior communicating MIAs (n=26). Clinical data of the patients and the morphological parameters of the MIAs were collected. Computational fluid dynamics (CFD) analysis was performed to obtain hemodynamic parameters, such as pressure (P), wall shear stress (WSS), wall shear stress gradient (WSSG), and oscillatory shear index (OSI). The coefficient of variation (CV) was used to describe the aforementioned hemodynamic parameters of intracranial aneurysms, so the index after CV adjustment is expressed as P_CV , WSS_CV , WSSG_CV , OSI_CV . Characteristics between ruptured and unruptured groups were compared. Conditional logistic regression analysis was conducted to evaluate the rupture risk factors of MIAs. Results: Among the 29 pairs of mirror aneurysms, 16 pairs were distributed in bilateral posterior communicating arteries (55%), 9 pairs distributed in bilateral middle cerebral arteries (31%), and 4 pairs distributed in bilateral internal carotid arteries (14%). Compared with the unruptured MIAs group, the ruptured aneurysms group usually had a larger maximum diameter, neck width, and size ratio (SR) [4.98 (3.18, 6.79) mm vs 3.20 (2.10, 4.31) mm, 4.19 (3.46, 5.95) mm vs 4.05 (3.23, 5.02) mm, 1.69 (0.81, 2.28) vs 0.96 (0.67, 1.49)] (all P<0.05). In the subgroup hemodynamic analysis of MIAs, the ruptured aneurysms had higher WSS_CV and WSSG_CV than the contralateral unruptured ones [1.00(0.87, 1.21) vs 0.65(0.57, 0.87), 1.09(0.56, 1.90) vs 0.57(0.50, 1.13), 1.52 (1.34, 1.80) vs 1.21 (1.07, 1.38), 1.52±0.46 vs 1.21±0.23] (all P<0.05), while the P_CV was lower than the contralateral unruptured ones [0.004 (0.002, 0.008) vs 0.010 (0.006, 0.013), 0.003 (0.002, 0.011) vs 0.009 (0.002, 0.066)] (both P<0.05). Logistic regression analysis showed that high WSSG_CV was an independent risk factor for MIAs rupture (OR=279.20(95%CI:1.10-71 028.28)). Conclusion: The maximum diameter, neck width, and SR were considered as a reliable morphological parameters to distinguish the ruptured status of MIAs, higher WSSG_CV in the aneurysm sac are highly correlated with MIAs rupture.

Repurposing Ivermectin to augment chemotherapy's efficacy in osteosarcoma

BACKGROUND

Osteosarcoma is the most frequent malignant bone malignancy and the current treatments are ineffective. Ivermectin, an anti-protozoal drug, has been shown to have anti-cancer activity. This work investigated the potential of repurposing ivermectin to augment chemotherapy's efficacy in osteosarcoma.

METHODS

Proliferation, migration and apoptosis assays were performed in ivermectin-treated osteosarcoma cells. Combination studies were performed. Osteosarcoma xenograft mouse model was established to investigate the in vivo efficacy of ivermectin. Intracellular reactive oxygen species (ROS) and mitochondrial superoxide, membrane potential, ATP, 8-OHdG level, protein carbonylation and lipid peroxidation were determined after ivermectin treatment.

RESULTS

Ivermectin was effective and acted synergistically with doxorubicin in osteosarcoma cells regardless of cellular origin and genetic profiling. This was achieved through suppressing inhibiting growth and migration, and inducing caspase-dependent apoptosis. Ivermectin also significantly inhibited osteosarcoma growth in vivo and its combination with doxorubicin resulted in much greater efficacy than doxorubicin alone. Importantly, the effective dose of ivermectin was clinically feasible and did not cause significant toxicity in mice. Mechanistical analysis showed that ivermectin induced oxidative stress and damage, and mitochondrial dysfunction.

CONCLUSIONS

Our findings indicate that ivermectin has utility in treating patients with osteosarcoma, especially those resistant to chemotherapy.