Epigenetic Reprogramming of Autophagy Drives Mutant IDH1 Glioma Progression and Response to Radiation

Mutant isocitrate dehydrogenase 1 (mIDH1; IDH1 R132H ) exhibits a gain of function mutation enabling 2-hydroxyglutarate (2HG) production. 2HG inhibits DNA and histone demethylases, inducing epigenetic reprogramming and corresponding changes to the transcriptome. We previously demonstrated 2HG-mediated epigenetic reprogramming enhances DNA-damage response and confers radioresistance in mIDH1 gliomas harboring p53 and ATRX loss of function mutations. In this study, RNA-seq and ChIP-seq data revealed human and mouse mIDH1 glioma neurospheres have downregulated gene ontologies related to mitochondrial metabolism and upregulated autophagy. Further analysis revealed that the decreased mitochondrial metabolism was paralleled by a decrease in glycolysis, rendering autophagy as a source of energy in mIDH1 glioma cells. Analysis of autophagy pathways showed that mIDH1 glioma cells exhibited increased expression of pULK1-S555 and enhanced LC3 I/II conversion, indicating augmented autophagy activity. This dependence is reflected by increased sensitivity of mIDH1 glioma cells to autophagy inhibition. Blocking autophagy selectively impairs the growth of cultured mIDH1 glioma cells but not wild-type IDH1 (wtIDH1) glioma cells. Targeting autophagy by systemic administration of synthetic protein nanoparticles packaged with siRNA targeting Atg7 (SPNP-siRNA-Atg7) sensitized mIDH1 glioma cells to radiation-induced cell death, resulting in tumor regression, long-term survival, and immunological memory, when used in combination with IR. Our results indicate autophagy as a critical pathway for survival and maintenance of mIDH1 glioma cells, a strategy that has significant potential for future clinical translation.

One Sentence Summary

The inhibition of autophagy sensitizes mIDH1 glioma cells to radiation, thus creating a promising therapeutic strategy for mIDH1 glioma patients.

Graphical abstract

Our genetically engineered mIDH1 mouse glioma model harbors IDH1 R132H in the context of ATRX and TP53 knockdown. The production of 2-HG elicited an epigenetic reprogramming associated with a disruption in mitochondrial activity and an enhancement of autophagy in mIDH1 glioma cells. Autophagy is a mechanism involved in cell homeostasis related with cell survival under energetic stress and DNA damage protection. Autophagy has been associated with radio resistance. The inhibition of autophagy thus radio sensitizes mIDH1 glioma cells and enhances survival of mIDH1 glioma-bearing mice, representing a novel therapeutic target for this glioma subtype with potential applicability in combined clinical strategies.

Synthesis and Structural Optimization of ATG4B Inhibitors for the Attenuation of Autophagy in Glioblastoma

Glioblastoma, a prevalent malignant CNS tumor, presents a therapeutic challenge because of resistance to standard treatments, including radiation therapy and temozolomide. Both modalities induce autophagy, thereby paradoxically promoting tumor survival. The cysteine protease ATG4B is implicated in this cellular process, which highlights the enzyme as a viable therapeutic target for glioblastoma. We have developed streamlined syntheses for ATG4B inhibitor NSC185058, its derivatives, and fluorogenic ATG4B substrate pim-FG-PABA-AMC. We leveraged these findings to rapidly identify novel compound MJO445, which demonstrates markedly greater potency biochemically and in cells.

CDK7 and CDK9 inhibition interferes with transcription, translation, and stemness, and induces cytotoxicity in GBM irrespective of temozolomide sensitivity

BACKGROUND

Glioblastoma (GBM) is refractory to current treatment modalities while side effects of treatments result in neurotoxicity and cognitive impairment. Here we test the hypothesis that inhibiting CDK7 or CDK9 would effectively combat GBM with reduced neurotoxicity.

METHODS

We examined the effect of a CDK7 inhibitor, THZ1, and multiple CDK9 inhibitors (SNS032, AZD4573, NVP2, and JSH150) on GBM cell lines, patient-derived temozolomide (TMZ)-resistant and responsive primary tumor cells and glioma stem cells (GSCs). Biochemical changes were assessed by western blotting, immunofluorescence, multispectral imaging, and RT-PCR. In vivo, efficacy was assessed in orthotopic and subcutaneous xenograft models.

RESULTS

CDK7 and CDK9 inhibitors suppressed the viability of TMZ-responsive and resistant GBM cells and GSCs at low nanomolar concentrations, with limited cytotoxic effects in vivo. The inhibitors abrogated RNA Pol II and p70S6K phosphorylation and nascent protein synthesis. Furthermore, the self-renewal of GSCs was significantly reduced with a corresponding reduction in Sox2 and Sox9 levels. Analysis of TCGA data showed increased expression of CDK7, CDK9, SOX2, SOX9, and RPS6KB1 in GBM; supporting this, multispectral imaging of a TMA revealed increased levels of CDK9, Sox2, Sox9, phospho-S6, and phospho-p70S6K in GBM compared to normal brains. RNA-Seq results suggested that inhibitors suppressed tumor-promoting genes while inducing tumor-suppressive genes. Furthermore, the studies conducted on subcutaneous and orthotopic GBM tumor xenograft models showed that administration of CDK9 inhibitors markedly suppressed tumor growth in vivo.

CONCLUSIONS

Our results suggest that CDK7 and CDK9 targeted therapies may be effective against TMZ-sensitive and resistant GBM.

SGC-CLK-1: A chemical probe for the Cdc2-like kinases CLK1, CLK2, and CLK4

Small molecule modulators are important tools to study both basic biology and the complex signaling of protein kinases. The cdc2-like kinases (CLK) are a family of four kinases that have garnered recent interest for their involvement in a diverse set of diseases such as neurodegeneration, autoimmunity, and many cancers. Targeted medicinal chemistry around a CLK inhibitor hit identified through screening of a kinase inhibitor set against a large panel of kinases allowed us to identify a potent and selective inhibitor of CLK1, 2, and 4. Here, we present the synthesis, selectivity, and preliminary biological characterization of this compound - SGC-CLK-1 (CAF-170). We further show CLK2 has the highest binding affinity, and high CLK2 expression correlates with a lower IC50 in a screen of multiple cancer cell lines. Finally, we show that SGC-CLK-1 not only reduces serine arginine-rich (SR) protein phosphorylation but also alters SR protein and CLK2 subcellular localization in a reversible way. Therefore, we anticipate that this compound will be a valuable tool for increasing our understanding of CLKs and their targets, SR proteins, at the level of phosphorylation and subcellular localization.

Repurposing Clemastine to Target Glioblastoma Cell Stemness

Brain tumor-initiating cells (BTICs) and tumor cell plasticity promote glioblastoma (GBM) progression. Here, we demonstrate that clemastine, an over-the-counter drug for treating hay fever and allergy symptoms, effectively attenuated the stemness and suppressed the propagation of primary BTIC cultures bearing PDGFRA amplification. These effects on BTICs were accompanied by altered gene expression profiling indicative of their more differentiated states, resonating with the activity of clemastine in promoting the differentiation of normal oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes. Functional assays for pharmacological targets of clemastine revealed that the Emopamil Binding Protein (EBP), an enzyme in the cholesterol biosynthesis pathway, is essential for BTIC propagation and a target that mediates the suppressive effects of clemastine. Finally, we showed that a neural stem cell-derived mouse glioma model displaying predominantly proneural features was similarly susceptible to clemastine treatment. Collectively, these results identify pathways essential for maintaining the stemness and progenitor features of GBMs, uncover BTIC dependency on EBP, and suggest that non-oncology, low-toxicity drugs with OPC differentiation-promoting activity can be repurposed to target GBM stemness and aid in their treatment.

Oncogenic long noncoding RNA LINC02283 enhances PDGF receptor A-mediated signaling and drives glioblastoma tumorigenesis

BACKGROUND

Long noncoding RNAs (lncRNAs) regulate the etiology of complex diseases and cancers, including glioblastoma (GBM). However, lncRNA-based therapies are limited because the mechanisms of action of many lncRNAs with their binding partners are not completely understood.

METHODS

We used transcriptomic and genomic data to analyze correlations between LINC02283 and PDGFRA (platelet-derived growth factor receptor A). The biological functions of the novel lncRNA were assessed in vivo using patient-derived glioma stem-like cells (GSCs), and orthotopic GBM xenografts. Immunoblotting, qRT-PCR, RNA pull down, crosslinked RNA immunoprecipitation, fluorescence in situ hybridization, and antisense oligo-mediated knockdown were performed to explore the regulation of LINC02283 on PDGFRA signaling. Expression of LINC02283 in clinical samples was assessed using pathologically diagnosed GBM patient samples.

RESULTS

We identified a novel oncogenic lncRNA, LINC02283, that is highly expressed in the PDGFRA mutation-driven cohort of glioma patients and associated with worse prognosis. LINC02283 gene co-amplifies with the PDGFRA locus and shows high correlation with PDGFRA expression. Deprivation of LINC02283 in GSCs with PDGFRA amplification mutation, attenuated tumorigenicity and enhanced survival in orthotopic GBM xenograft models, while overexpression of LINC02283 in GSCs with wild-type PDGFRA, enhances PDGFRA signaling, and decreases survival. Further, LINC02283 interacts with PDGFRA to enhance its signaling and that of its downstream targets AKT and ERK, thus promoting oncogenesis in GBM.

CONCLUSIONS

Our results provide strong evidence of LINC02283 as a regulator of PDGFRA oncogenic activity and GBM malignancy and support the potential of lncRNAs as possible therapeutic targets.

Dissection of transcriptomic and epigenetic heterogeneity of grade 4 gliomas: implications for prognosis

BACKGROUND

Grade 4 glioma is the most aggressive and currently incurable brain tumor with a median survival of one year in adult patients. Elucidating novel transcriptomic and epigenetic contributors to the molecular heterogeneity underlying its aggressiveness may lead to improved clinical outcomes.

METHODS

To identify grade 4 glioma -associated 5-hydroxymethylcytosine (5hmC) and transcriptomic features as well as their cross-talks, genome-wide 5hmC and transcriptomic profiles of tissue samples from 61 patients with grade 4 gliomas and 9 normal controls were obtained for differential and co-regulation/co-modification analyses. Prognostic models on overall survival based on transcriptomic features and the 5hmC modifications summarized over genic regions (promoters, gene bodies) and brain-derived histone marks were developed using machine learning algorithms.

RESULTS

Despite global reduction, the majority of differential 5hmC features showed higher modification levels in grade 4 gliomas as compared to normal controls. In addition, the bi-directional correlations between 5hmC modifications over promoter regions or gene bodies and gene expression were greatly disturbed in grade 4 gliomas regardless of IDH1 mutation status. Phenotype-associated co-regulated 5hmC-5hmC modules and 5hmC-mRNA modules not only are enriched with different molecular pathways that are indicative of the pathogenesis of grade 4 gliomas, but also are of prognostic significance comparable to IDH1 mutation status. Lastly, the best-performing 5hmC model can predict patient survival at a much higher accuracy (c-index = 74%) when compared to conventional prognostic factor IDH1 (c-index = 57%), capturing the molecular characteristics of tumors that are independent of IDH1 mutation status and gene expression-based molecular subtypes.

CONCLUSIONS

The 5hmC-based prognostic model could offer a robust tool to predict survival in patients with grade 4 gliomas, potentially outperforming existing prognostic factors such as IDH1 mutations. The crosstalk between 5hmC and gene expression revealed another layer of complexity underlying the molecular heterogeneity in grade 4 gliomas, offering opportunities for identifying novel therapeutic targets.

PETCH-DB: a Portal for Exploring Tissue-specific and Complex disease-associated 5-Hydroxymethylcytosines

Epigenetic modifications play critical roles in gene regulation and disease pathobiology. Highly sensitive enabling technologies, including microarray- and sequencing-based approaches have allowed genome-wide profiling of cytosine modifications in DNAs in clinical samples to facilitate discovery of epigenetic biomarkers for disease diagnosis and prognosis. Historically, many previous studies, however, did not distinguish the most investigated 5-methylcytosines (5mC) from other modified cytosines, especially the biochemically stable 5-hydroxymethylcytosines (5hmC), which have been shown to have a distinct genomic distribution and regulatory role from 5mC. Notably, during the past several years, the 5hmC-Seal, a highly sensitive chemical labeling technique, has been demonstrated to be a powerful tool for genome-wide profiling of 5hmC in clinically feasible biospecimens (e.g. a few milliliter of plasma or serum). The 5hmC-Seal technique has been utilized by our team in biomarker discovery for human cancers and other complex diseases using circulating cell-free DNA (cfDNA), as well as the characterization of the first 5hmC Human Tissue Map. Convenient access to the accumulating 5hmC-Seal data will allow the research community to validate and re-use these results, potentially providing novel insights into epigenetic contribution to a range of human diseases. Here we introduce the PETCH-DB, an integrated database that was implemented to provide 5hmC-related results generated using the 5hmC-Seal technique. We aim the PETCH-DB to be a central portal, which will be available to the scientific community with regularly updated 5hmC data in clinical samples to reflect current advances in this field. Database URL http://petch-db.org/.

The mammalian Sterile 20-like kinase 4 (MST4) signaling in tumor progression: Implications for therapy

Cancer is a leading cause of death in humans, with a complex and dynamic nature that makes it challenging to fully comprehend and treat. The Mammalian Sterile 20-Like Kinase 4 (MST4 or STK26) is a serine/threonine-protein kinase that plays a crucial role in cell migration and polarity in both normal and tumor cells via activation of intracellular signaling molecules and pathways. MST4 is involved in tumor cell proliferation, migration and invasion, epithelial-mesenchymal transition (EMT), survival, and cancer metastasis through modulation of downstream signaling pathways including the extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) pathways. Additionally, MST4 interacts with programmed cell death 10 (PDCD10) to promote tumor proliferation and migration. MST4 phosphorylates autophagy related 4B cysteine peptidase (ATG4B) to mediate autophagy signaling, promote tumor cell survival and proliferation, and contribute to treatment resistance. Taken together, MST4 functions as an oncogene and is a promising therapeutic target which deserves further exploration.

STEM-21. REPURPOSING CLEMASTINE TO SUPPRESS GLIOBLASTOMA STEM CELLS

Glioblastoma stem cells (GSCs), also known as brain tumor initiating cells (BTICs), drive tumor progression, heterogeneity, and resistance to treatments, posing formidable challenges to advancing effective treatments against glioblastoma (GBM). We postulated that inducing BTIC differentiation can serve as a solution to diminishing their stem-like features. Here, we report that clemastine, an over-the-counter oral medication for allergy relief, attenuates stemness and proliferation of BTICs. These effects of clemastine were accompanied by altered transcriptional programs suggestive of a shift from maintaining stem cell identity to differentiation, resonating with the ability of clemastine to promote oligodendrocyte precursor cell (OPC) differentiation to mature oligodendrocytes. Genetic perturbation and small-molecule inhibition of putative pharmacological targets of clemastine revealed that Emopamil-binding protein (EBP), an enzyme in the sterol biosynthesis pathway, played a pivotal role in mediating the differentiating and anti-tumor effects of clemastine. Notably, loss-of-function assays showed that EBP expression was indispensable for BTIC propagation. In contrast, overexpression of EBP stimulated BTIC proliferation, thus uncovering a previously unknown role of sterol metabolism in BTIC maintenance. Finally, we demonstrated that a mouse neural stem cell-derived glioma model was similarly susceptible to clemastine treatment. Taken together, our study identifies pathways essential for the perpetuation of stemness in GBM, and implicates a non-oncology drug with a well-established safety profile that can be repurposed to mitigate the stem-like properties of GBM.

CSIG-14. THE PDGFRA-REGULATING LNCRNA LINC02283 IS AMPLIFIED IN HIGH-GRADE GLIOMA AND FACILITATES GLIOMAGENESIS

Long non-coding RNAs (lncRNAs) regulate numerous physiological processes and the etiology of diseases including cancers. However, lncRNA-based therapies are limited because the mechanism of action of many lncRNAs and their interaction with binding partners is not completely understood. We have identified LINC02283, a novel oncogenic lncRNA, highly expressed in the PDGF Receptor A (PDGFRA)-mutation driven cohort of high-grade glioma (HGG) patients which accounts for ~8% of glioma cases. LINC02283 gene co-amplifies with the PDGFRA locus and is upregulated in HGG. LINC02283 expression and copy number variation were highly correlated to that of PDGFRA expression and amplification respectively, and high LINC02283 levels leads to worse survival in HGG patients. We found that LINC02283 transcription is essential for the survival of Glioma Stem cells (GSCs) with PDGFRA amplification mutation, and its inhibition significantly improves survival in orthotopic HGG xenograft models. Interestingly, overexpression of LINC02283 in GSCs with wild type (wt) - PDGFRA, enhance PDGFRA signaling, increases cell proliferation and worsens survival in orthotopic HGG xenograft models. Inhibition of PDGFRA signaling using AG1296, represses the high endogenous LINC02283 levels in PDGFRA-mutant GSCs, reduces LINC02283 induced signaling in PDGFRA-wt GSCs, and suppresses cell proliferation in both the cellular models of HGG. Moreover, LINC02283 co-localizes and interacts with the wild-type and mutant PDGFRA to enhance its signaling and that of its downstream targets Akt and Erk. In a feedback regulation, dysregulated PDGFRA signaling induces LINC02283 levels to enhance cell proliferation in GSC and GBM cellular models through activating its downstream, Akt and Erk signaling pathways, as their inhibition reduces the lncRNA induction and function. Thus, blocking the LINC02283-PDGFRA interaction could be a plausible therapeutic strategy in HGG. Altogether, our results provide strong evidence of lncRNAs as drivers of PDGF Receptor A activity and HGG progression and support the potential of lncRNAs as possible therapeutic targets.

CNSC-06. TEMOZOLOMIDE-INDUCED GUANINE MUTATIONS CREATE EXPLOITABLE VULNERABILITIES OF GUANINE-RICH DNA AND RNA REGIONS IN DRUG-RESISTANT GLIOMAS

Temozolomide (TMZ) is a chemotherapeutic agent that has been the first-line standard of care for the aggressive braincancer glioblastoma (GBM) since 2005. Although initially beneficial, TMZ resistance is universal and second-lineinterventions are an unmet clinical need. Here, we took advantage of the known mechanism of action of TMZ to targetguanines (G) and investigated G-rich G-quadruplex (G4) and splice site changes that occur upon TMZ resistance. We reportthat TMZ-resistant GBM has guanine mutations that disrupt the G-rich DNA G4s and splice sites that lead to deregulatedalternative splicing. These alterations create vulnerabilities, which are selectively targeted by either the G4-stabilizingdrug TMPyP4 or a novel splicing kinase inhibitor of cdc2-like kinase. Lastly, we show that the G4 and RNA binding proteinEWSR1, member of the FUS, EWSR1, and TAF15 family, aggregates in the cytoplasm in TMZ-resistant GBM cells and patient samples. Together, our findings provide insight into targetable vulnerabilities of TMZ-resistant GBM and present cytoplasmic EWSR1 as a putative biomarker.

Modeling Therapy-Driven Evolution of Glioblastoma with Patient-Derived Xenografts

Adult-type diffusely infiltrating gliomas, of which glioblastoma is the most common and aggressive, almost always recur after treatment and are fatal. Improved understanding of therapy-driven tumor evolution and acquired therapy resistance in gliomas is essential for improving patient outcomes, yet the majority of the models currently used in preclinical research are of therapy-naïve tumors. Here, we describe the development of therapy-resistant IDH-wildtype glioblastoma patient-derived xenografts (PDX) through orthotopic engraftment of therapy naïve PDX in athymic nude mice, and repeated in vivo exposure to the therapeutic modalities most often used in treating glioblastoma patients: radiotherapy and temozolomide chemotherapy. Post-temozolomide PDX became enriched for C>T transition mutations, acquired inactivating mutations in DNA mismatch repair genes (especially MSH6), and developed hypermutation. Such post-temozolomide PDX were resistant to additional temozolomide (median survival decrease from 80 days in parental PDX to 42 days in a temozolomide-resistant derivative). However, temozolomide-resistant PDX were sensitive to lomustine (also known as CCNU), a nitrosourea which induces tumor cell apoptosis by a different mechanism than temozolomide. These PDX models mimic changes observed in recurrent GBM in patients, including critical features of therapy-driven tumor evolution. These models can therefore serve as valuable tools for improving our understanding and treatment of recurrent glioma.

The Role of Non-Coding RNAs in Glioma

For decades, research in cancer biology has been focused on the protein-coding fraction of the human genome. However, with the discovery of non-coding RNAs (ncRNAs), it has become known that these entities not only function in numerous fundamental life processes such as growth, differentiation, and development, but also play critical roles in a wide spectrum of human diseases, including cancer. Dysregulated ncRNA expression is found to affect cancer initiation, progression, and therapy resistance, through transcriptional, post-transcriptional, or epigenetic processes in the cell. In this review, we focus on the recent development and advances in ncRNA biology that are pertinent to their role in glioma tumorigenesis and therapy response. Gliomas are common, and are the most aggressive type of primary tumors, which account for ~30% of central nervous system (CNS) tumors. Of these, glioblastoma (GBM), which are grade IV tumors, are the most lethal brain tumors. Only 5% of GBM patients survive beyond five years upon diagnosis. Hence, a deeper understanding of the cellular non-coding transcriptome might help identify biomarkers and therapeutic agents for a better treatment of glioma. Here, we delve into the functional roles of microRNA (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA) in glioma tumorigenesis, discuss the function of their extracellular counterparts, and highlight their potential as biomarkers and therapeutic agents in glioma.

Temozolomide-induced guanine mutations create exploitable vulnerabilities of guanine-rich DNA and RNA regions in drug-resistant gliomas

Temozolomide (TMZ) is a chemotherapeutic agent that has been the first-line standard of care for the aggressive brain cancer glioblastoma (GBM) since 2005. Although initially beneficial, TMZ resistance is universal and second-line interventions are an unmet clinical need. Here, we took advantage of the known mechanism of action of TMZ to target guanines (G) and investigated G-rich G-quadruplex (G4) and splice site changes that occur upon TMZ resistance. We report that TMZ-resistant GBM has guanine mutations that disrupt the G-rich DNA G4s and splice sites that lead to deregulated alternative splicing. These alterations create vulnerabilities, which are selectively targeted by either the G4-stabilizing drug TMPyP4 or a novel splicing kinase inhibitor of cdc2-like kinase. Last, we show that the G4 and RNA binding protein EWSR1 aggregates in the cytoplasm in TMZ-resistant GBM cells and patient samples. Together, our findings provide insight into targetable vulnerabilities of TMZ-resistant GBM and present cytoplasmic EWSR1 as a putative biomarker.

[Effects of salivary microbiota on tryptophan-aryl hydrocarbon receptor signaling axis in mice with periodontitis]

Objective: To study the effects of salivary microbiota in patients with periodontitis on the tryptophan-aryl hydrocarbon receptor (AhR) signaling axis in mice with periodontitis and to provide theoretical basis as well as new ideas for the influences of periodontitis on systemic metabolism. Methods: Salivary microbiota of 12 healthy individuals and 14 patients with periodontitis were collected in Nanjing Stomatological Hospital, Medical School of Nanjing University from June to December of 2020. According to the random number table method, twenty-four mice were randomly divided into three groups: Sham group (control group), P group (periodontitis patients' salivary microbiota group) and H group (periodontal healthy individuals' salivary microbiota group). The maxillary second molars of all mice were treated with silk thread ligation to induce periodontitis. Phosphate buffer as well as salivary microbiota of periodontal healthy individuals and periodontitis patients were gavaged into periodontitis mice for 2 weeks. The expression of inflammatory factors in mice serum were detected by enzyme linked immunosorbent assay, and the expression of tryptophan and indole metabolites in intestinal tract and serum were detected by liquid chromatography-mass spectrometry. The expression of AhR in intestinal tract of mice was detected by immunohistochemistry and quantitative real time-PCR while gut microbiota constitution was detected by 16S rRNA gene sequencing. The remaining saliva samples of periodontitis patients and periodontal healthy individuals were applied to detect the expression of tryptophan and indole metabolites themselves. Results: The salivary microbiota of periodontitis patients could induce the expression of interleukin-1β [P group: (162.38±39.46) pg/ml, H group: (82.83±20.01) pg/ml; t=4.40, P=0.001) and tumor necrosis factor-α [P group: (361.16±123.90) pg/ml, H group: (191.66±106.87) pg/ml; t=2.54, P=0.030) in serum of periodontitis mice, and reduce the expression of AhR in colon (P group: 1.18±0.05, H group:1.83±0.47; t=3.09, P=0.015) and ileum (P group: 0.80±0.13, H group: 1.18±0.11; t=4.93, P=0.001). After gavage of salivary microbiota of periodontitis patients to the mice, tryptophan (P group: (18.1±3.8)×10⁷, H group: (26.6±6.6)×10⁷; t=2.49, P=0.037] and indole lactic acid [P group: (1.9±0.7)×10⁷, H group: (3.7±0.6)×10⁷; t=4.49, P=0.002) in serum of periodontitis mice were significantly decreased, but was relatively disorder in intestinal tract. However, the expressions of tryptophan and indole metabolites in saliva of periodontitis patients were higher than those of periodontal healthy individuals. There were significant differences in indole propionic acid [P group: (1 239.39±818.72) nmol/L, H group: (56.96±38.33) nmol/L; t=2.83, P=0.022]. What we find noteworthy was that the expressions of indolelactic acid metabolism in saliva, serum and intestinal were consistent, and salivary microbiota of periodontitis patients could reduce the relative abundance of indolelactic acid-producing bacteria in the gut, suggesting that the salivary microbiota of periodontitis patients might affect the expression of AhR through gut microbiota disorder and indolelactic acid downregulation. Conclusions: Salivary microbiota in patients with periodontitis may affect the systemic inflammatory state through down-regulating the expression of tryptophan-AhR signal axis.

DNA damage and metabolic mechanisms of cancer drug resistance

Cancer drug resistance is one of the main barriers to overcome to ensure durable treatment responses. While many pivotal advances have been made in first combination therapies, then targeted therapies, and now broadening out to immunomodulatory drugs or metabolic targeting compounds, drug resistance is still ultimately universally fatal. In this brief review, we will discuss different strategies that have been used to fight drug resistance from synthetic lethality to tumor microenvironment modulation, focusing on the DNA damage response and tumor metabolism both within tumor cells and their surrounding microenvironment. In this way, with a better understanding of both targetable mutations in combination with the metabolism, smarter drugs may be designed to combat cancer drug resistance.

LY6K promotes glioblastoma tumorigenicity via CAV-1-mediated ERK1/2 signaling enhancement

BACKGROUND

Lymphocyte antigen 6 complex, locus K (LY6K) is a putative oncogene in various cancers. Elevated expression of LY6K is correlated with poor patient prognosis in glioblastoma (GBM). The aim of this study is to advance our understanding of the mechanism by which LY6K contributes to GBM tumor biology.

METHODS

Bioinformatic data mining was used to investigate LY6K expression in relation to GBM clinical outcome. To understand the role of LY6K in GBM, we utilized patient-derived glioma stemlike cells (GSCs) and U87 cells and employed immunoblotting, immunofluorescent staining, radiation treatment, and orthotopic GBM xenograft models.

RESULTS

Our results show that increased expression of LY6K inversely correlates with GBM patient survival. LY6K promotes tumorigenicity in GBM cells both in vitro and in vivo. The mechanism underlying this tumorigenic behavior is enhancement of extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling. Interestingly, we observed that tumor-promoting LY6K-ERK1/2 signaling is mediated by the interaction of LY6K with caveolin-1, rather than through oncogenic receptor tyrosine kinase-mediated signaling. Moreover, association of LY6K with the cell membrane is crucial for its tumorigenic functions. Finally, DNA methylation maintains LY6K silencing, and hypomethylation of the LY6K promoter increases its expression. In GSCs, ionizing radiation leads to demethylation of the LY6K promoter, thereby increasing LY6K expression and GSC resistance to radiation.

CONCLUSIONS

Our study highlights the importance of the contribution of LY6K to GBM tumor biology and suggests LY6K as a potential membrane target for treating GBM.

An integrative analysis of genome-wide 5-hydroxymethylcytosines in circulating cell-free DNA detects noninvasive diagnostic markers for gliomas

Background

Gliomas, especially the high-grade glioblastomas (GBM), are highly aggressive tumors in the central nervous system (CNS) with dismal clinical outcomes. Effective biomarkers, which are not currently available, may improve clinical outcomes through early detection. We sought to develop a noninvasive diagnostic approach for gliomas based on 5-hydroxymethylcytosines (5hmC) in circulating cell-free DNA (cfDNA).

Methods

We obtained genome-wide 5hmC profiles using the 5hmC-Seal technique in cfDNA samples from 111 prospectively enrolled patients with gliomas and 111 age-, gender-matched healthy individuals, which were split into a training set and a validation set. Integrated models comprised 5hmC levels summarized for gene bodies, long noncoding RNAs (lncRNAs), cis-regulatory elements, and repetitive elements were developed using the elastic net regularization under a case-control design.

Results

The integrated 5hmC-based models differentiated healthy individuals from gliomas (area under the curve [AUC] = 84%; 95% confidence interval [CI], 74-93%), GBM patients (AUC = 84%; 95% CI, 74-94%), WHO II-III glioma patients (AUC = 86%; 95% CI, 76-96%), regardless of IDH1 (encoding isocitrate dehydrogenase) mutation status or other glioma-related pathological features such as TERT, TP53 in the validation set. Furthermore, the 5hmC biomarkers in cfDNA showed the potential as an independent indicator from IDH1 mutation status and worked in synergy with IDH1 mutation to distinguish GBM from WHO II-III gliomas. Exploration of the 5hmC biomarkers for gliomas revealed relevance to glioma biology.

Conclusions

The 5hmC-Seal in cfDNA offers the promise as a noninvasive approach for effective detection of gliomas in a screening program.

Circular RNA-encoded oncogenic E-cadherin variant promotes glioblastoma tumorigenicity through activation of EGFR-STAT3 signalling

Activated EGFR signalling drives tumorigenicity in 50% of glioblastoma (GBM). However, EGFR-targeting therapy has proven ineffective in treating patients with GBM, indicating that there is redundant EGFR activation. Circular RNAs are covalently closed RNA transcripts that are involved in various physiological and pathological processes. Herein, we report an additional activation mechanism of EGFR signalling in GBM by an undescribed secretory E-cadherin protein variant (C-E-Cad) encoded by a circular E-cadherin (circ-E-Cad) RNA through multiple-round open reading frame translation. C-E-Cad is overexpressed in GBM and promotes glioma stem cell tumorigenicity. C-E-Cad activates EGFR independent of EGF through association with the EGFR CR2 domain using a unique 14-amino-acid carboxy terminus, thereby maintaining glioma stem cell tumorigenicity. Notably, inhibition of C-E-Cad markedly enhances the antitumour activity of therapeutic anti-EGFR strategies in GBM. Our results uncover a critical role of C-E-Cad in stimulating EGFR signalling and provide a promising approach for treating EGFR-driven GBM.

The Many Facets of Therapy Resistance and Tumor Recurrence in Glioblastoma

Glioblastoma (GBM) is the most lethal type of primary brain cancer. Standard care using chemo- and radio-therapy modestly increases the overall survival of patients; however, recurrence is inevitable, due to treatment resistance and lack of response to targeted therapies. GBM therapy resistance has been attributed to several extrinsic and intrinsic factors which affect the dynamics of tumor evolution and physiology thus creating clinical challenges. Tumor-intrinsic factors such as tumor heterogeneity, hypermutation, altered metabolomics and oncologically activated alternative splicing pathways change the tumor landscape to facilitate therapy failure and tumor progression. Moreover, tumor-extrinsic factors such as hypoxia and an immune-suppressive tumor microenvironment (TME) are the chief causes of immunotherapy failure in GBM. Amid the success of immunotherapy in other cancers, GBM has occurred as a model of resistance, thus focusing current efforts on not only alleviating the immunotolerance but also evading the escape mechanisms of tumor cells to therapy, caused by inter- and intra-tumoral heterogeneity. Here we review the various mechanisms of therapy resistance in GBM, caused by the continuously evolving tumor dynamics as well as the complex TME, which cumulatively contribute to GBM malignancy and therapy failure; in an attempt to understand and identify effective therapies for recurrent GBM.

PRMT6 methylation of RCC1 regulates mitosis, tumorigenicity, and radiation response of glioblastoma stem cells

Aberrant cell proliferation is a hallmark of cancer, including glioblastoma (GBM). Here we report that protein arginine methyltransferase (PRMT) 6 activity is required for the proliferation, stem-like properties, and tumorigenicity of glioblastoma stem cells (GSCs), a subpopulation in GBM critical for malignancy. We identified a casein kinase 2 (CK2)-PRMT6-regulator of chromatin condensation 1 (RCC1) signaling axis whose activity is an important contributor to the stem-like properties and tumor biology of GSCs. CK2 phosphorylates and stabilizes PRMT6 through deubiquitylation, which promotes PRMT6 methylation of RCC1, which in turn is required for RCC1 association with chromatin and activation of RAN. Disruption of this pathway results in defects in mitosis. EPZ020411, a specific small-molecule inhibitor for PRMT6, suppresses RCC1 arginine methylation and improves the cytotoxic activity of radiotherapy against GSC brain tumor xenografts. This study identifies a CK2α-PRMT6-RCC1 signaling axis that can be therapeutically targeted in the treatment of GBM.

[Current status and research progress of third-line treatment for patients with gastric cancer in China]

Gastric cancer (GC) is one of the most common malignant tumors in the world. The prognosis of advanced GC is extremely poor, characterized by the high recurrence or disease progression rate after the first-line chemotherapy, and the extremely low long-term survival rate. Meanwhile, the options for subsequent treatment are limited. Studies have shown that the third-line therapy can provide significant survival benefits for selected patients with advanced GC. Currently, a series of randomized controlled trials and real-world studies related to chemotherapy, targeted therapy, and immunotherapy are conducted. In addition, the explorations of combination therapy, and screening the optimal clinical features or predictive biomarkers for the suitable population who might benefit from the third-line regimens are the hot spots for researchers. This article will provide a detailed overview of the current status and progress of the third-line treatment for advanced GC, and to illustrate the characteristics of Chinese GC treatment.

TMOD-35. DEVELOPING RECURRENT GBM PDX, IN VIVO, FROM TREATMENT NAÏVE SOURCES

PURPOSE

Post-therapy recurrent glioblastoma (GBM) patient-derived xenografts (PDX), developed from corresponding treatment-naïve PDX, could serve as useful resources for identifying therapeutics with activity against recurrent GBM. The goal of this study was to determine whether treatment-naïve intracranial GBM PDX, in mice receiving radiotherapy (RT) and/or temozolomide (TMZ), acquire the same mutations that occur in post-RT+TMZ GBMs from patients.

METHODS

Luciferase-modified, treatment-naïve GBM PDX were engrafted in the brains of athymic nude mice, followed by treatment with RT only (2 Gy/day x 5), TMZ only (10 mg/kg/day x 5), or RT+TMZ. Bioluminescence imaging was used to monitor intracranial tumor growth, response to treatment, and recurrence from treatment. Some mice with recurrent tumors received additional TMZ treatment. When mice became symptomatic, intracranial tumors were resected and engrafted subcutaneously in a new mouse host, then sequentially propagated subcutaneously into additional host mice. After the third passage, whole-exome sequencing (WES) was done, comparing post-therapy with treatment-naïve PDX sequence variants.

RESULTS

Analysis of PDX WES showed the following: 1) TMZ consistently caused more genes to incur coding sequence mutations than RT, as much as 13x more; 2) TMZ-treated tumor mutations were mostly G-C to A-T transitions (71-92%), consistent with the known mutagenic effect of TMZ; and 3) post-therapy PDX acquire similar mutations as do recurrent GBMs in patients, for example involving DNA mismatch repair gene MSH6. One of the derivative PDX with MSH6 mutation has been retested for response to RT and TMZ, with results showing its having become TMZ, but not RT resistant.

CONCLUSIONS

The mutation profiles of RT+TMZ-treated PDX are similar to those reported for GBMs that recur after RT+TMZ in patients. The new PDX resources described here may prove useful for identifying effective treatments against recurrent GBM.

Abstract LB-310: Whole-exome sequencing reveals genetic underpinnings of salivary adenoid cystic carcinoma and tongue carcinoma in Chinese population

Background: Salivary adenoid cystic carcinoma (ACC) and oral tongue squamous cell carcinoma (OTSCC) are rare malignancies with low incidence and dismal prognosis. The molecular underpinnings of these remain poorly understood, particularly in Asian population. Methods: Through a whole-exome sequencing analysis of 13 OTSCC and 30 ACC patients, a systematic overview of the mutational features in single-nucleotide variations, copy number variations and chromosomal variations were illustrated. Results: In addition to the well-characterized alterations previously reported in Caucasian patients, such as TP53 mutations (11/13, 84.6%) in OTSCC and MYB-NFIB fusion in ACC (11/30, 36.7%), we also observed several novel genetic changes, including FOXP1-TEX261 fusion (1/13, 7.7%) and MYB-FMO5 fusion (1/30, 3.3%) in OTSCC and ACC respectively, which might play a role in facilitating tumor progression. The data exhibited promising translational value as numerous actionable genes were identified with mutations. 76.9% OTSCC and 20% salivary ACC harbored at least one alteration in actionable genes, mutations in CDKN2A (4/13, 30.8%), NTRK3 (3/13, 23.1%) in OTSCC and FGFR2 (2/30, 6.7%), BRAF (2/30, 6.7%) in salivary gland ACC, suggesting targeted immunotherapy might be an effective intervention. Instead of MYB-independent NFIB fusions previously reported in ACC, only NFIB-independent MYB fusions were found in our cohort, indicating that alterations in NFIB rather than MYB might be essential to ACC tumorigenesis. Conclusions: This study reveals the genetic underpinnings of two rare malignancies in Chinese population, illustrating consistent mutational features with published literature as well as demonstrating several distinct genetic alterations, warranting further investigations.

Citation Format: Ning Li, Shuhang Wang, Yue Yu, Yuan Fang, Huiyao Huang, Dawei Wu, Hong Fang, Chao Sun, Anqi Yu, Qi Fan, Shi-Yuan Cheng. Whole-exome sequencing reveals genetic underpinnings of salivary adenoid cystic carcinoma and tongue carcinoma in Chinese population [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 LB-310.

Stem cell programs in cancer initiation, progression, and therapy resistance

Over the past few decades, substantial evidence has convincingly revealed the existence of cancer stem cells (CSCs) as a minor subpopulation in cancers, contributing to an aberrantly high degree of cellular heterogeneity within the tumor. CSCs are functionally defined by their abilities of self-renewal and differentiation, often in response to cues from their microenvironment. Biological phenotypes of CSCs are regulated by the integrated transcriptional, post-transcriptional, metabolic, and epigenetic regulatory networks. CSCs contribute to tumor progression, therapeutic resistance, and disease recurrence through their sustained proliferation, invasion into normal tissue, promotion of angiogenesis, evasion of the immune system, and resistance to conventional anticancer therapies. Therefore, elucidation of the molecular mechanisms that drive cancer stem cell maintenance, plasticity, and therapeutic resistance will enhance our ability to improve the effectiveness of targeted therapies for CSCs. In this review, we highlight the key features and mechanisms that regulate CSC function in tumor initiation, progression, and therapy resistance. We discuss factors for CSC therapeutic resistance, such as quiescence, induction of epithelial-to-mesenchymal transition (EMT), and resistance to DNA damage-induced cell death. We evaluate therapeutic approaches for eliminating therapy-resistant CSC subpopulations, including anticancer drugs that target key CSC signaling pathways and cell surface markers, viral therapies, the awakening of quiescent CSCs, and immunotherapy. We also assess the impact of new technologies, such as single-cell sequencing and CRISPR-Cas9 screening, on the investigation of the biological properties of CSCs. Moreover, challenges remain to be addressed in the coming years, including experimental approaches for investigating CSCs and obstacles in therapeutic targeting of CSCs.

Targeting PDGFRα-activated glioblastoma through specific inhibition of SHP-2-mediated signaling

BACKGROUND

Glioblastoma (GBM) is the most malignant primary brain tumor, with dismal median survival. Treatment of GBM is particularly challenging given the intrinsic resistance to chemotherapy and difficulty of drugs to reach the tumor beds due to the blood-brain barrier. Here, we examined the efficacy of SHP099, a potent, selective, and oral SHP-2 inhibitor for treating GBM with activated platelet derived growth factor receptor alpha (PDGFRα) signaling.

METHODS

The effects of SHP099 on cell survival of neural progenitor cells (NPCs), GBM cell lines, and patient-derived glioma stem-like cells (GSCs) were evaluated. Brain and plasma pharmacokinetics of SHP099 and its ability to inhibit SHP-2 signaling were assessed. SHP099 efficacy as a single agent or in combination with temozolomide (TMZ) was assessed using transformed mouse astrocyte and GSC orthotopic xenograft models.

RESULTS

Activated PDGFRα signaling in established GBM cells, GSCs, and transformed mouse astrocytes was significantly inhibited by SHP099 compared with NPCs in vitro and in vivo through targeting SHP-2-stimulated activation of extracellular signal-regulated protein kinases 1 and 2 in GBM. SHP099 treatment specifically inhibited expression of JUN, a downstream effector of PDGFR signaling, thereby attenuating cell cycle progression in GBM cells with activated PDGFRα. Moreover, SHP099 accumulated at efficacious concentrations in the brain and effectively inhibited orthotopic GBM tumor xenograft growth. SHP099 exhibited antitumor activity either as a single agent or in combination with TMZ and provided significant survival benefits for GBM tumor xenograft-bearing animals.

CONCLUSIONS

Our data demonstrate the utility and feasibility of SHP099 as a potential therapeutic option for improving the clinical treatment of GBM in combination with TMZ.

Perioperative outcomes of women with and without class III obesity undergoing hysterectomy for endometrioid endometrial cancer: A population-based study

OBJECTIVE

Population-based data on perioperative complications among women with endometrial cancer and severe obesity are lacking. We evaluated 30-day complication rates among women with and without class III obesity (body mass index ≥ 40 kg/m²) undergoing primary surgical management for endometrioid endometrial cancer (EEC), and how outcomes differed according to surgical approach (open vs. minimally invasive).

METHODS

We performed a retrospective population-based cohort study of women with EEC undergoing hysterectomy in Ontario, Canada, between 2006 and 2015. We evaluated perioperative complications in the whole cohort, and in a 1:1 matched analysis using hard and propensity score matching to ensure similar distributions of patient, tumour, provider and institution-level factors between women with and without class III obesity (identified using a surgical billing code). The primary outcome of interest was the 30-day perioperative complication rate.

RESULTS

12,112 women met inclusion criteria; 2697 (22.3%) had class III obesity. We matched 2320 (86%) women with class III obesity to those without. The composite complication rate was significantly higher among women with class III obesity (23.2% vs. 18.4%, standardized mean difference [SMD] = 0.12), primarily due to wound infection/disruption (12.1% vs. 6.2%). There was no difference in outcomes for women with and without class III obesity when a minimally invasive approach was used.

CONCLUSIONS

Wound infection/disruption was increased for women with class III obesity compared to women without. Otherwise, perioperative complications were similar between the matched pairs. When minimally invasive approaches were used, women with class III obesity had a similar risk of complications as women without obesity.

RDNA-03. AUTOPHAGY AS A NOVEL THERAPEUTIC TARGET IN MUTANT IDH1 GLIOMAS

Mutated Isocitrate dehydrogenase 1 (IDH1R132H; mIDH1) is found in 50% of all adult gliomas and in 80% of lower-grade gliomas. IDH1R132H promotes 2-hydroxyglutarate production which inhibits histone and DNA demethylases, inducing epigenetic reprogramming of the tumor transcriptome. We recently demonstrated that epigenetic reprogramming enhances DNA-damage response and confers radioresistance in mIDH1 glioma, harboring p53 and ATRX loss. Furthermore, several studies indicate that IDH1R132H triggers cellular metabolism reprogramming. In this study, RNA-seq data revealed that mIDH1 glioma neurospheres (mIDH1-NS) have downregulated gene ontologies related to mitochondrial metabolism. Analysis of mitochondrial and glycolytic activity, using a Seahorse Analyzer, showed that mIDH1-NS have decreased levels of oxygen consumption and extracellular acidification rates, characteristic of quiescent state. Nevertheless, mIDH1 glioma cells can grow and generate tumors, suggesting that they might maintain self-renewal via autophagy. To investigate this hypothesis, we studied autophagy in wild-type and mIDH1 glioma cells analyzing LC3 conversion, p62 expression, and ULK1 protein phosphorylation. Mouse and human mIDH1 glioma cells exhibited increased expression of pULK1-S555, enhanced conversion of LC3I to LC3II, and decreased expression of p62, indicating that mIDH1 cells have an augmented autophagy. Also, key proteins involved in autophagy, including MST4 and UVRAG, are upregulated in mIDH1-NS. We also studied autophagy flux using LC3-mCherry-GFP reporter to identify LC3 recruitment at the autophagosome membranes and the autolysosome activity. Our results showed that mIDH1 cells have increased LC3 recruitment and enhanced autolysosome activity. Interestingly, autophagy has been related with glioma radioresistance. In our study, mouse and human mIDH1 glioma cells are sensitive to autophagy inhibition. In addition, autophagy inhibition restored radiosensitivity in mouse and human mIDH1 glioma cells, and in our mIDH1 glioma model, enhancing median survival compared with radiation alone. In conclusion, our results indicate that mIDH1 glioma cells maintain self-renewal via activation of autophagy, which represents a novel therapeutic target.

Temperature and excitation wavelength dependence of circular and linear photogalvanic effect in a three dimensional topological insulator Bi2Se3

The circular (CPGE) and linear photogalvanic effect (LPGE) of a three-dimensional topological insulator Bi₂Se₃ thin film of seven quintuple layers excited by near-infrared (1064 nm) and mid-infrared (10.6 [Formula: see text]m) radiations have been investigated. The comparison of the CPGE current measured parallel and perpendicular to the incident plane, together with the comparison of the CPGE current under front and back illuminations, indicates that the CPGE under front illumination of 1064 nm light is dominated by the top surface states of the Bi₂Se₃ thin film. The CPGE current excited by 10.6 [Formula: see text]m light is about one order larger than that excited by 1064 nm light, which may be attributed to the smaller cancelation effect of the CPGE generated in the two-dimensional electron gas when excited by 10.6 [Formula: see text]m light. Under the excitation of 1064 nm light, the LPGE current is dominated by the component which shows an even parity of incident angles, while the LPGE current excited by 10.6 [Formula: see text]m light is mainly contributed by the component which is an odd parity of incident angles. Both of the CPGE and LPGE currents excited by 1064 nm decrease with increasing temperature, which may be owing to the decrease of the momentum relaxation time and the stronger electron-electron scattering with increasing temperature, respectively.

The generation of two specific cancer costing algorithms using Ontario administrative databases

Cancer treatment and management have become increasingly economically burdensome. Consequently, to help with planning health service delivery, it is vital to understand the associated costs. Administrative databases can be used to help understand and generate real-world system-level costs. Using databases to generate costs can take one of two approaches: top-down or bottom-up. Top-down approaches disaggregate the total health care spending from a global health care budget by sector and provider. A bottom-up approach begins with individual-level health care use and its costs, which are then aggregated.

SRSF3-Regulated RNA Alternative Splicing Promotes Glioblastoma Tumorigenicity by Affecting Multiple Cellular Processes

Misregulated alternative RNA splicing (AS) contributes to the tumorigenesis and progression of human cancers, including glioblastoma (GBM). Here, we showed that a major splicing factor, serine and arginine rich splicing factor 3 (SRSF3), was frequently upregulated in clinical glioma specimens and that elevated SRSF3 was associated with tumor progression and a poor prognosis for patients with glioma. In patient-derived glioma stem-like cells (GSC), SRSF3 expression promoted cell proliferation, self-renewal, and tumorigenesis. Transcriptomic profiling identified more than 1,000 SRSF3-affected AS events, with a preference for exon skipping in genes involved with cell mitosis. Motif analysis identified the sequence of CA(G/C/A)CC(C/A) as a potential exonic splicing enhancer for these SRSF3-regulated exons. To evaluate the biological impact of SRSF3-affected AS events, four candidates were selected whose AS correlated with SRSF3 expression in glioma tissues, and their splicing pattern was modified using a CRISPR/Cas9 approach. Two functionally validated AS candidates were further investigated for the mechanisms underlying their isoform-specific functions. Specifically, following knockout of SRSF3, transcription factor ETS variant 1 (ETV1) gene showed exon skipping at exon 7, while nudE neurodevelopment protein 1 (NDE1) gene showed replacement of terminal exon 9 with a mutually exclusive exon 9'. SRSF3-regulated AS of these two genes markedly increased their oncogenic activity in GSCs. Taken together, our data demonstrate that SRSF3 is a key regulator of AS in GBM and that understanding mechanisms of misregulated AS could provide critical insights for developing effective therapeutic strategies against GBMs. SIGNIFICANCE: SRSF3 is a significant regulator of glioma-associated alternative splicing, implicating SRSF3 as an oncogenic factor that contributes to the tumor biology of GBM.

Correction to: Lipolytic inhibitor G0S2 modulates glioma stem-like cell radiation response

In the original publication of this article [1], the Gene Expression Omnibus (GEO) accession code GSE79772 is wrong. The correct accession code should be GSE86213.

Abstract 3432: Novel roles of LY6K in glioblastoma tumorigenesis

Glioblastoma (GBM) is the most malignant brain cancer, with extremely poor prognosis in patients. GBM tumors are characterized by distinct molecular subtypes, known as proneural (PN), classical, and mesenchymal (MES). Inherited heterogeneity and aberrant aggressiveness contribute to therapy resistance and frequent recurrence of malignant GBM tumors. In addition, GBM tumors also contain a small subpopulation of tumor-initiating or stem-like cancer cells (GSCs). Gene expression profiling studies from our laboratory showed that patient-derived GSCs can also be classified into two subtypes, PN and MES, that are phenotypically similar to clinical GBM. Among three thousand genes that are differentially expressed between PN and MES-like GSCs, Lymphocyte Antigen 6 Complex, Locus K (LY6K) was identified as one of the top differentially expressed genes. LY6K is a GPI-anchored protein from the LY6 family. Several members of the LY6 family have been implicated in human cancers, including breast, esophageal, and lung cancers. Moreover, the function of LY6K in GBM has not been reported. Here, we examined the roles of LY6K upregulation in GBM tumorigenesis and investigated the underlying mechanism of LY6K action. We hypothesized that high levels of LY6K in GSCs promotes GBM tumorigenesis. Based on our other preliminary data, we further hypothesized that LY6K functions by enhancing ERK activation, thus promoting radioresistance. To test our hypotheses, we first examined the role of LY6K in advancing GBM tumorigenic behaviors of GSCs. We performed in vitro and in vivo tumorigenicity assays and showed that the presence of LY6K significantly increases GSC cell growth and glioma sphere forming ability in vitro and promotes tumor formation in orthotopic brain xenograft mouse models. The underlying mechanism governing LY6K expression was found to be DNA promoter methylation. Moreover, irradiation strongly induces LY6K expression via demethylation of LY6K promoter in GSCs with otherwise undetectable levels of LY6K. Furthermore, we investigated the mechanism by which LY6K contributes to GSC tumorigenicity. We observed that there is a strong relationship between LY6K and ERK signaling in GSCs and U87 glioma cells. The presence of LY6K stimulates ERK activation and subsequently augments cell proliferation of GSCs. Lastly, we identified the GPI-anchor domain of LY6K as a key region in enhancing ERK activation and are currently examining the mechanistic properties of this domain. The mechanistic insights gained from our studies will advance current knowledge of aberrantly upregulated LY6K and ERK signaling enhancement in promoting GBM tumorigenicity.

Citation Format: Namratha G. Sastry, Tianzhi Huang, Angel Alvarez, Rajendra Pangeni, Xiao Song, Xuechao Wan, John Kessler, Ichiro Nakano, Bo Hu, Shi-Yuan Cheng. Novel roles of LY6K in glioblastoma tumorigenesis [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 3432.

Abstract 5236: A qualitative change in transcriptome during MDCKII 3D epithelial morphogenesis is linked to intracellular trafficking

The majority of human cancers are derived from epithelial tissues. Understanding epithelial morphogenesis is hence important in cancer research. Madin-Darby canine kidney II (MDCKII) cells, cultured in 3D and 2D conditions, are used extensively as a model for studying cell polarity, epithelial morphogenesis and carcinogenesis. Like other cell differentiation systems, gene expression plays a key role in MDCKII epithelial morphogenesis.

To better understand the change in the transcriptome, we performed a time course RNA-seq analysis of MDCKII 3D cytogenesis, along with fully polarized 2D cells for comparison. Surprisingly, our study reveals that the change is not linear, but rather clearly biphasic. Specifically, about 3,000 genes are significantly up- or down-regulated between 24 hour and day 3 after seeding, when the lumen is forming, compared to < 120 such genes during other time intervals. Because previous studies have shown that Rab11-coordinated intracellular trafficking plays an essential role in MDCKII lumen formation, we hypothesize this qualitative change in the transcriptome is linked to intracellular trafficking. To test this hypothesis, we used knockdown clones of AVL9 and DENND5A, both interacting with Rab11 and participating in trafficking. Knockdown cells have altered cell polarity and defective trafficking, but not as significant changes in transcriptome as wild type cells, supporting our hypothesis. We then focused on β-catenin to better understand the mechanism. Our study reveals that in wild type cells, following the first cell division, β-catenin is depleted from the nucleus and enriched in cell-cell junction. This results in MYC transcriptional silencing (supported by ATAC-seq analysis), which in turn initiated down-regulation of numerous MYC target genes. These observations are however not observed in knockdown cells.

Our study supports the qualitative change (“switch on-off”) model, rather than the quantitative (gradual) change model, in transcriptome remodeling during epithelial cell differentiation. Moreover, our work supports that intracellular trafficking likely initiates this quantitative change in transcriptome.

Citation Format: Tianfang Wang, Shaying Zhao, Shi-Yuan Cheng. A qualitative change in transcriptome during MDCKII 3D epithelial morphogenesis is linked to intracellular trafficking [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 5236.

MIR93 (microRNA -93) regulates tumorigenicity and therapy response of glioblastoma by targeting autophagy

Macroautophagy/autophagy is a natural intracellular process that maintains cellular homeostasis and protects cells from death under stress conditions. Autophagy sustains tumor survival and growth when induced by common cancer treatments, including IR and cytotoxic chemotherapy, thereby contributing to therapeutic resistance of tumors. In this study, we report that the expression of MIR93, noted in two clinically relevant tumor subtypes of GBM, influenced GSC phenotype as well as tumor response to therapy through its effects on autophagy. Our mechanistic studies revealed that MIR93 regulated autophagic activities in GSCs through simultaneous inhibition of multiple autophagy regulators, including BECN1/Beclin 1, ATG5, ATG4B, and SQSTM1/p62. Moreover, two first-line treatments for GBM, IR and temozolomide (TMZ), as well as rapamycin (Rap), the prototypic MTOR inhibitor, decreased MIR93 expression that, in turn, stimulated autophagic processes in GSCs. Inhibition of autophagy by ectopic MIR93 expression, or via autophagy inhibitors NSC (an ATG4B inhibitor) and CQ, enhanced the activity of IR and TMZ against GSCs. Collectively, our findings reveal a key role for MIR93 in the regulation of autophagy and suggest a combination treatment strategy involving the inhibition of autophagy while administering cytotoxic therapy. Abbreviations: ACTB: actin beta; ATG4B: autophagy related 4B cysteine peptidase; ATG5: autophagy related 5; BECN1: beclin 1; CL: classical; CQ: chloroquine diphosphate; CSCs: cancer stem cells; GBM: glioblastoma; GSCs: glioma stem-like cells; HEK: human embryonic kidney; IB: immunoblotting; IF: immunofluorescent staining; IR: irradiation; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MES: mesenchymal; MIR93: microRNA 93; MIRC: a control miRNA; miRNA/miR: microRNA; MTOR: mechanistic target of rapamycin kinase; NSC: NSC185085; PN: proneural; qRT-PCR: quantitative reverse transcription-polymerase chain reaction; Rap: rapamycin; SQSTM1/p62: sequestosome 1; TCGA: the cancer genome atlas; TMZ: temozolomide; WT: wild type; ZIP93: lentiviral miRZIP targeting MIR93; ZIPC: lentiviral miRZip targeting control miRNA.

Effects of an Oral-Pharyngeal Motor Training Programme on Children with Obstructive Sleep Apnea Syndrome in Hong Kong: A Retrospective Pilot Study

Background

This study aimed to investigate the effects of an oropharyngeal motor training programme on children with Obstructive Sleep Apnea Syndrome (OSAS) in Hong Kong.

Methods

In this retrospective study, we reviewed the outcomes of 10 children with OSAS who had received an oropharyngeal motor training programme in Occupational Therapy Department of an acute hospital in Hong Kong over a 1-year programme. Each participant attended an individual oropharyngeal motor training programme plus a follow-up session after 2 months. The training programme consisted of 10 individual mobilization exercises involving the orofacial and pharyngeal area for 45 minutes. Each exercise had to be repeated for 10 times. Three outcome measures were chosen to study the effectiveness of the training programme including tongue strength, tongue endurance level and orofacial function. Tongue strength and tongue endurance level were assessed using the Iowa Oral Pressure Instrument (IOPI). The Nordic Orofacial Test-Screening (NOT-S) Assessment was used to assess the orofacial function. Seven out of 10 participants completed the training programme and attended the follow-up session after two months.

Results

The tongue strength and the scores of NOT-S of the 7 participants were found to have significant improvement after training. However, there was no significant difference in tongue endurance level.

Conclusion

The findings of this study support the role of occupational therapist in oromotor training modalities to improve the respiratory function for children with OSAS in Hong Kong. Copyright © 2017, Hong Kong Occupational Therapy Association. Published by Elsevier (Singapore) Pte Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Genome-wide methylomic and transcriptomic analyses identify subtype-specific epigenetic signatures commonly dysregulated in glioma stem cells and glioblastoma

Glioma stem cells (GSCs), a subpopulation of tumor cells, contribute to tumor heterogeneity and therapy resistance. Gene expression profiling classified glioblastoma (GBM) and GSCs into four transcriptomically-defined subtypes. Here, we determined the DNA methylation signatures in transcriptomically pre-classified GSC and GBM bulk tumors subtypes. We hypothesized that these DNA methylation signatures correlate with gene expression and are uniquely associated either with only GSCs or only GBM bulk tumors. Additional methylation signatures may be commonly associated with both GSCs and GBM bulk tumors, i.e., common to non-stem-like and stem-like tumor cell populations and correlating with the clinical prognosis of glioma patients. We analyzed Illumina 450K methylation array and expression data from a panel of 23 patient-derived GSCs. We referenced these results with The Cancer Genome Atlas (TCGA) GBM datasets to generate methylomic and transcriptomic signatures for GSCs and GBM bulk tumors of each transcriptomically pre-defined tumor subtype. Survival analyses were carried out for these signature genes using publicly available datasets, including from TCGA. We report that DNA methylation signatures in proneural and mesenchymal tumor subtypes are either unique to GSCs, unique to GBM bulk tumors, or common to both. Further, dysregulated DNA methylation correlates with gene expression and clinical prognoses. Additionally, many previously identified transcriptionally-regulated markers are also dysregulated due to DNA methylation. The subtype-specific DNA methylation signatures described in this study could be useful for refining GBM sub-classification, improving prognostic accuracy, and making therapeutic decisions.

Abstract 355: Histone acetyltransferase KAT6A upregulates PI3K/AKT signaling through TRIM24 binding

Lysine acetyltransferase KAT6A is a chromatin regulator that contributes to histone modification and cancer, but the basis of its actions are not well understood. Here we identify a KAT6A signaling pathway that facilitates glioblastoma (GBM) where it is upregulated. KAT6A expression was associated with GBM patient survival. KAT6A silencing suppressed cell proliferation, cell migration, colony formation and tumor development in an orthotopic mouse xenograft model system. Mechanistic investigations demonstrated that KAT6A acetylates lysine 23 of histone H3 (H3K23), which recruits the nuclear receptor binding protein TRIM24 to activate PIK3CA transcription, thereby enhancing PI3K/AKT signaling and tumorigenesis. Overexpressing activated AKT or PIK3CA rescued the growth inhibition due to KAT6A silencing. Conversely, the pan-PI3K inhibitor LY294002 abrogated the growth-promoting effect of KAT6A. Overexpression of KAT6A or TRIM24, but not KAT6A acetyltransferase activity- deficient mutants or TRIM24 mutants lacking H3K23ac binding sites promoted PIK3CA expression, AKT phosphorylation and cell proliferation. Taken together, our results define an essential role of KAT6A in glioma formation, rationalizing its candidacy as a therapeutic target for GBM treatment.

Citation Format: Deguan Lv, Feng Jia, Yanli Hou, Youzhou Sang, Angel A. Alvarez, Weiwei Zhang, Bo Hu, Shi-Yuan Cheng, Jianwei Ge, Yanxin Li, Haizhong Feng. Histone acetyltransferase KAT6A upregulates PI3K/AKT signaling through TRIM24 binding [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 355.

Abstract 1122: MST4 phosphorylation of ATG4B regulates autophagic activity, tumorigenicity, and radio resistance in glioblastoma

Autophagy-mediated intracellular catabolism sustains the rapid growth of established tumors and tumors in response to multiple stresses including genotoxic/cytotoxic therapies. Here we identify and validate ATG4B, a key regulator that stimulates autophagic process by promoting autophagosome through reversible modification of ATG8 as a novel substrate of mammalian sterile20-like kinase (STK) 26/MST4 that is less known for its function in cellular process (none in autophagy) and unknown authentic substrates in cancer. We show that MST4 phosphorylates ATG4B at serine residue 383, which stimulates ATG4B activity and increases autophagic flux. Inhibition of MST4 or ATG4B activities suppresses autophagic process and the tumorigenicity of glioblastoma (GBM) cells. Furthermore, radiation induces MST4 expression, ATG4B phosphorylation and autophagy. Inhibiting ATG4B in combination with radiotherapy in treating mice with intracranial GBM tumor xenografts markedly slows tumor growth and provides significant survival benefit to animal subjects. This study not only describes a novel regulatory mechanism by which the MST4-ATG4B axis accelerates autophagic process, regulates GBM tumorigenicity, and responses to radiotherapy (RT), but also explores imminent clinical utility of combination of ATG4B inhibition with RT to suppress orthotopic GBM tumor xenografts. This study should prove generalizable to other types of cancer and have positive impacts in advancing our knowledge of cancer biology and designing new cancer treatments.

Citation Format: Tianzhi Huang, Chung Kwon Kim, Angel A. Alvarez, Rajendra P Pangeni, Xuechao Wan, xiao song, Taiping shi, Yongyong Yongyong, Namratha Sastry, Craig Horbinski, Songjian Lu, Roger Stupp, John Kessler, Ryo Nishikawa, Ichiro Nakano, Erik Sulman, Xinghua Lu, Charles David James, Xiao-Ming Yin, Bo Hu, Shi-Yuan Cheng. MST4 phosphorylation of ATG4B regulates autophagic activity, tumorigenicity, and radio resistance in glioblastoma [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 1122.

Abstract 2540: TRIM24 is an oncogenic transcriptional co-activator of STAT3 in glioblastoma

Aberrant amplification and mutations of epidermal growth factor receptor (EGFR) are the most common oncogenic events in glioblastoma (GBM), but the mechanisms by which they promote aggressive pathogenesis are not well understood. Here, we determine that non-canonical histone signature acetylated H3 lysine 23 (H3K23ac)-binding protein tripartite motif-containing 24 (TRIM24) is upregulated in clinical GBM specimens and required for EGFR-driven tumorigenesis. In multiple glioma cell lines and patient-derived glioma stem cells (GSCs), EGFR signaling promotes H3K23 acetylation and association with TRIM24. Consequently, TRIM24 functions as a transcriptional co-activator and recruits STAT3, leading to stabilized STAT3-chromatin interactions and subsequent activation of STAT3 downstream signaling, thereby enhancing EGFR-driven tumorigenesis. Our findings uncover a pathway in which TRIM24 functions as a signal relay for oncogenic EGFR signaling and suggest TRIM24 as a potential therapeutic target for GBM that are associated with EGFR activation.

Citation Format: Deguan Lv, Yanxin Li, Weiwei Zhang, Angel A. Alvarez, Jianming Tang, Bo Hu, Shi-Yuan Cheng, Haizhong Feng. TRIM24 is an oncogenic transcriptional co-activator of STAT3 in glioblastoma [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 2540.

TRIM59 Promotes Gliomagenesis by Inhibiting TC45 Dephosphorylation of STAT3

Aberrant EGFR signaling is a common driver of glioblastoma (GBM) pathogenesis; however, the downstream effectors that sustain this oncogenic pathway remain unclarified. Here we demonstrate that tripartite motif-containing protein 59 (TRIM59) acts as a new downstream effector of EGFR signaling by regulating STAT3 activation in GBM. EGFR signaling led to TRIM59 upregulation through SOX9 and enhanced the interaction between TRIM59 and nuclear STAT3, which prevents STAT3 dephosphorylation by the nuclear form of T-cell protein tyrosine phosphatase (TC45), thereby maintaining transcriptional activation and promoting tumorigenesis. Silencing TRIM59 suppresses cell proliferation, migration, and orthotopic xenograft brain tumor formation of GBM cells and glioma stem cells. Evaluation of GBM patient samples revealed an association between EGFR activation, TRIM59 expression, STAT3 phosphorylation, and poor prognoses. Our study identifies TRIM59 as a new regulator of oncogenic EGFR/STAT3 signaling and as a potential therapeutic target for GBM patients with EGFR activation.Significance: These findings identify a novel component of the EGFR/STAT3 signaling axis in the regulation of glioma tumorigenesis. Cancer Res; 78(7); 1792-804. ©2018 AACR.