Dual HDAC and PI3K Inhibition Abrogates NFκB- and FOXM1-Mediated DNA Damage Response to Radiosensitize Pediatric High-Grade Gliomas

Phase I Study of Vorinostat and Temsirolimus in Newly Diagnosed or Progressive Diffuse Intrinsic Pontine Glioma

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) carries a poor prognosis with a median survival of less than 12 months. Key molecular features include histone H3 mutation (K27M) and AKT pathway dysregulation. There is currently no curative treatment.

METHODS

This is a Phase I study of vorinostat and temsirolimus in newly diagnosed (Stratum 1) and progressive (Stratum 2) DIPG (NCT02420613). The primary aims are to determine the safety, maximum tolerated dose (MTD), and toxicities. A modified 3 + 3 design was used to establish the MTD, where the first three patients were assigned the first dose level regardless of stratum. Stratum 1 received radiotherapy with vorinostat, followed by up to 10 cycles of vorinostat and temsirolimus. Stratum 2 received up to 12 cycles of vorinostat and temsirolimus. Vorinostat was administered at a fixed dose of 230 mg/m2 daily on Days 1-8, and temsirolimus was administered on Days 1 and 8 at 25 mg/m2 (Dose level 1) or 35 mg/m2 (Dose level 2).

RESULTS

Six patients were enrolled, three in each stratum. No dose-limiting toxicity was observed, and most adverse effects were limited to Grades 1 or 2, including fatigue, myelosuppression, hyperlipidemia, hyperglycemia, elevated creatinine, nausea, vomiting, and headache. One patient experienced Grade 3 leukopenia. In the study, the MTD with acceptable toxicity was vorinostat 230 mg/m2 and temsirolimus 35 mg/m2.

CONCLUSIONS

Overall, the combination of temsirolimus and vorinostat is well-tolerated and safe, prompting the need for larger studies to investigate its efficacy.

Key genes altered in glioblastoma based on bioinformatics (Review)

Glioblastoma multiforme (GBM) is an aggressive brain tumor with poor prognosis. Recent advancements in bioinformatics have contributed to uncovering the genetic alterations that underlie the development and progression of GBM. Analysis of extensive genomic data led to the identification of significant pathways involved in GBM, such as the PI3K/AKT/mTOR and Ras/Raf/MEK/ERK signaling pathways, alongside key genes such as EGFR, TP53 and TERT. These findings have enhanced our understanding of GBM biology and led to the identification of new therapeutic targets. Bioinformatics has become an indispensable tool in pinpointing the genetic modifications that drive GBM, paving the way for innovative treatment strategies. This approach not only aids in comprehending the complexities of GBM but also holds promise for improving outcomes in patients suffering from this devastating disease. The ongoing integration of bioinformatics in GBM research continues to be vital for advancing therapeutic options.

The dual HDAC/PI3K inhibitor CUDC-907 inhibits the growth and proliferation of MYC-driven Group 3 medulloblastoma

Metastatic Group 3 medulloblastoma (G3 MB) have been shown in several studies to be very high risk, particularly those harboring MYC amplification. More effective therapies are especially important for these patients. CUDC-907, a novel dual inhibitor targeting the MYC upstream pathway (HDAC/PI3K), shows significant antitumor efficacy across multiple cancer types. However, the antitumor effects and underlying mechanisms of CUDC-907 in MB, particularly in very high-risk MB, remain unexplored. In this study, we showed that MYC amplified G3 MB cells, patient-derived organoids and xenograft models were sensitive to CUDC-907. CUDC-907 inhibited MYC expression through the HDAC and PI3K pathways, and then induced G0/G1 phase arrest through the MYC-P21/P27-CDKs/cyclins axis. Furthermore, when CUDC-907 was combined with chemotherapeutic drug cisplatin, G0/G1 phase blocking effect was further enhanced. CUDC-907 in combination with radiotherapy (RT) inhibited DNA damage repair and increased DNA damage. These findings indicate that CUDC-907, either as a monotherapy or in combination with chemoradiotherapy, represents a promising therapeutic strategy for MYC amplified G3 MB, potentially influencing future clinical trials targeting this patient population.

Regulation of FOXM1 by HDAC3 Inhibition Ameliorates Macrophage Endoplasmic Reticulum stress and Apoptosis in Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) infection may induce significant damage to the host lung tissues. Endoplasmic reticulum stress (ERS) and apoptosis of macrophages are considered key factors affecting the survival and pathogenicity of intracellular Mtb. Forkhead box M1 (FOXM1) is closely implicated in lung diseases. This study aimed to investigate the role of FOXM1 in Mtb infection and the involvement of histone deacetylase 3 (HDAC3) in this process. An in vitro Mtb infection model was established by infecting RAW264.7 macrophages with Mtb H37Ra. The results showed that RAW264.7 macrophages subjected to Mtb infection showed upregulated expressions of ERS markers and FOXM1. FOXM1 overexpression further elevated the levels of ERS and apoptosis markers, pro-inflammatory cytokines, and reactive oxygen species in Mtb-infected macrophages. FOXM1 could bind to the promoter of TXNIP and activate its transcription. Knockdown of TXNIP suppressed the effects of Mtb infection on macrophages, while upregulation of FOXM1 completely abolished the effects of TXNIP knockdown. HDAC3 inhibitor effectively diminished the effects of FOXM1 upregulation on Mtb-infected macrophages. In conclusion, inhibition of HDAC3 may reduce ERS and apoptosis of Mtb-infected macrophages by regulating the FOXM1/TXNIP axis.

Synergistic antitumor effect of MK-1775 and CUDC-907 against prostate cancer

Due to the emergence of drug resistance, androgen receptor (AR)-targeted drugs still pose great challenges in the treatment of prostate cancer, and it is urgent to explore an innovative therapeutic strategy. MK-1775, a highly selective WEE1 inhibitor, is shown to have favorable therapeutic benefits in several solid tumor models. Recent evidence suggests that the combination of MK-1775 with DNA-damaging agents could lead to enhanced antitumor efficacy. Here, our results demonstrate that MK-1775 alone could indeed inhibit proliferation and induce apoptosis in prostate cancer. Moreover, the combination of MK-1775 and a dual PI3K and HDAC inhibitor, CUDC-907, can synergistically inhibit cell proliferation and dramatically induces apoptosis in prostate cancer cells. This effect is partially mediated by DNA damage, resulting from the downregulation of DNA damage response (DDR) proteins such as CDK, CHK, and RRM1/2. Notably, the combination of MK-1775 and CUDC-907 leads to significant antitumor effects in vivo. Our findings provide a strong basis for a promising combination strategy against prostate cancer.

NCAPH serves as a prognostic factor and promotes the tumor progression in glioma through PI3K/AKT signaling pathway

Non-SMC (Structural Maintenance of Chromosomes) condensin I complex subunit H (NCAPH) has been shown to facilitate progression and predict adverse prognostic outcome in many cancer types. However, the function of NCAPH in gliomas is still unclear. Series of experiments were taken to uncover the function of NCAPH in glioma. The expression of NCAPH and potential mechanism regulating progression of glioma was verified by bioinformatics analysis. Lentiviral transfection was used for establishment of loss-of-function and gain-of-function cell lines. CCK-8 assay and Colony-formation assay were used to evaluate proliferation. Transwell assay and Cell wound healing assay were used to assess migration and invasion. Cell cycle and apoptosis were measured by flow cytometry. Protein and RNA were quantified by WB and RT-PCR, respectively. The nude mice model of glioma was used to evaluate the effect of NCAPH in vivo. The expression of NCAPH increased significantly in glioma tissues and correlated with WHO grade, IDH wild-type and non-1p/19q codeletion. Glioma patients with high expression of NCAPH had an undesirable prognosis. Functionally, upregulated NCAPH promotes the malignant hallmarks of glioma cells in vivo and in vitro. NCAPH correlated with DNA damage repair ability of glioma cells and facilitated the proliferation, invasion, and migration of glioma cells by promoting the PI3K/AKT signaling pathway. This study identifies the important pro-tumor role of NCAPH in glioma and suggests that NCAPH is a potential therapeutic target.

Exploring glioma heterogeneity through omics networks: from gene network discovery to causal insights and patient stratification

Gliomas are primary malignant brain tumors with a typically poor prognosis, exhibiting significant heterogeneity across different cancer types. Each glioma type possesses distinct molecular characteristics determining patient prognosis and therapeutic options. This study aims to explore the molecular complexity of gliomas at the transcriptome level, employing a comprehensive approach grounded in network discovery. The graphical lasso method was used to estimate a gene co-expression network for each glioma type from a transcriptomics dataset. Causality was subsequently inferred from correlation networks by estimating the Jacobian matrix. The networks were then analyzed for gene importance using centrality measures and modularity detection, leading to the selection of genes that might play an important role in the disease. To explore the pathways and biological functions these genes are involved in, KEGG and Gene Ontology (GO) enrichment analyses on the disclosed gene sets were performed, highlighting the significance of the genes selected across several relevent pathways and GO terms. Spectral clustering based on patient similarity networks was applied to stratify patients into groups with similar molecular characteristics and to assess whether the resulting clusters align with the diagnosed glioma type. The results presented highlight the ability of the proposed methodology to uncover relevant genes associated with glioma intertumoral heterogeneity. Further investigation might encompass biological validation of the putative biomarkers disclosed.

Progress Toward Epigenetic Targeted Therapies for Childhood Cancer

Among the most significant discoveries from cancer genomics efforts has been the critical role of epigenetic dysregulation in cancer development and progression. Studies across diverse cancer types have revealed frequent mutations in genes encoding epigenetic regulators, alterations in DNA methylation and histone modifications, and a dramatic reorganization of chromatin structure. Epigenetic changes are especially relevant to pediatric cancers, which are often characterized by a low rate of genetic mutations. The inherent reversibility of epigenetic lesions has led to an intense interest in the development of epigenetic targeted therapies. Additionally, the recent appreciation of the interplay between the epigenome and immune regulation has sparked interest in combination therapies and synergistic immunotherapy approaches. Further, the recent appreciation of epigenetic variability as a driving force in cancer evolution has suggested new roles for epigenetic therapies in limiting plasticity and resistance. Here, we review recent progress and emerging directions in the development of epigenetic targeted therapeutics and their promise across the landscape of childhood cancers.

CPT1A mediates radiation sensitivity in colorectal cancer

The prevalence and mortality rates of colorectal cancer (CRC) are increasing worldwide. Radiation resistance hinders radiotherapy, a standard treatment for advanced CRC, leading to local recurrence and metastasis. Elucidating the molecular mechanisms underlying radioresistance in CRC is critical to enhance therapeutic efficacy and patient outcomes. Bioinformatic analysis and tumour tissue examination were conducted to investigate the CPT1A mRNA and protein levels in CRC and their correlation with radiotherapy efficacy. Furthermore, lentiviral overexpression and CRISPR/Cas9 lentiviral vectors, along with in vitro and in vivo radiation experiments, were used to explore the effect of CPT1A on radiosensitivity. Additionally, transcriptomic sequencing, molecular biology experiments, and bioinformatic analyses were employed to elucidate the molecular mechanisms by which CPT1A regulates radiosensitivity. CPT1A was significantly downregulated in CRC and negatively correlated with responsiveness to neoadjuvant radiotherapy. Functional studies suggested that CPT1A mediates radiosensitivity, influencing reactive oxygen species (ROS) scavenging and DNA damage response. Transcriptomic and molecular analyses highlighted the involvement of the peroxisomal pathway. Mechanistic exploration revealed that CPT1A downregulates the FOXM1-SOD1/SOD2/CAT axis, moderating cellular ROS levels after irradiation and enhancing radiosensitivity. CPT1A downregulation contributes to radioresistance in CRC by augmenting the FOXM1-mediated antioxidant response. Thus, CPT1A is a potential biomarker of radiosensitivity and a novel target for overcoming radioresistance, offering a future direction to enhance CRC radiotherapy.

SOX10 mediates glioblastoma cell-state plasticity

Phenotypic plasticity is a cause of glioblastoma therapy failure. We previously showed that suppressing the oligodendrocyte-lineage regulator SOX10 promotes glioblastoma progression. Here, we analyze SOX10-mediated phenotypic plasticity and exploit it for glioblastoma therapy design. We show that low SOX10 expression is linked to neural stem-cell (NSC)-like glioblastoma cell states and is a consequence of temozolomide treatment in animal and cell line models. Single-cell transcriptome profiling of Sox10-KD tumors indicates that Sox10 suppression is sufficient to induce tumor progression to an aggressive NSC/developmental-like phenotype, including a quiescent NSC-like cell population. The quiescent NSC state is induced by temozolomide and Sox10-KD and reduced by Notch pathway inhibition in cell line models. Combination treatment using Notch and HDAC/PI3K inhibitors extends the survival of mice carrying Sox10-KD tumors, validating our experimental therapy approach. In summary, SOX10 suppression mediates glioblastoma progression through NSC/developmental cell-state transition, including the induction of a targetable quiescent NSC state. This work provides a rationale for the design of tumor therapies based on single-cell phenotypic plasticity analysis.

Combination treatment with histone deacetylase and carbonic anhydrase 9 inhibitors shows therapeutic potential in experimental diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) remains a significant therapeutic challenge due to the lack of effective and safe treatment options. This study explores the potential of combining histone deacetylase (HDAC) and carbonic anhydrase 9 (CA9) inhibitors in treating DIPG. Analysis of RNA sequencing data and tumor tissue from patient samples for the expression of the carbonic anhydrase family and hypoxia signaling pathway activity revealed clinical relevance for targeting CA9 in DIPG. A synergy screen was conducted using CA9 inhibitor SLC-0111 and HDAC inhibitors panobinostat, vorinostat, entinostat, and pyroxamide. The combination of SLC-0111 and pyroxamide demonstrated the highest synergy and was selected for further analysis. Combining SLC-0111 and pyroxamide effectively inhibited DIPG cell proliferation, reduced cell migration and invasion potential, and enhanced histone acetylation, leading to decreased cell population in S Phase. Additionally, the combination therapy induced a greater reduction in intracellular pH than either agent alone. Data from this study suggest that the combination of SLC-0111 and pyroxamide holds promise for treating experimental DIPG, and further investigation of this combination therapy in preclinical models is warranted to evaluate its potential as a viable treatment for DIPG.

Classical Monocytes Shuttling for Precise Delivery of Nanotherapeutics to Glioblastoma

Glioblastoma (GBM) is the most aggressive brain tumor for which current therapies have limited efficacy. Immunosuppression and difficulties in accessing tumors with therapeutic agents are major obstacles for GBM treatments. Classical monocytes (CMs) possess the strongest infiltration among myeloid cells recruited into tumors during tumorigenesis. In this study, CMs are utilized to deliver the small-molecule CUDC-907 encapsulated in nanoparticles (907-NPs@CMs) for GBM therapy. Hitchhiking on CMs enables more 907-NPs to successfully penetrate the blood-brain barrier (BBB) and reach the interior of tumors. Results demonstrate that 907-NPs@CMs significantly improve the survival rates by suppressing tumor growth and reversing the immunosuppression of tumor microenvironment (TME). Furthermore, the high delivery efficiency of CMs reduces the amount of CUDC-907 required for treatments, reducing the physiological toxicity and off-target effects caused by high doses. 907-NPs@CMs is a safe and versatile therapeutic system that provides a platform for targeted drug delivery to tumors and the ability to treat GBM through a combination of chemotherapy and immunotherapy.

Synergistic Cytotoxicity of Histone Deacetylase and Poly-ADP Ribose Polymerase Inhibitors and Decitabine in Breast and Ovarian Cancer Cells: Implications for Novel Therapeutic Combinations

Breast and ovarian cancers pose significant therapeutic challenges. We explored the synergistic cytotoxicity of histone deacetylase inhibitors (HDACis), poly(ADP-ribose) polymerase inhibitors (PARPis), and decitabine in breast (MDA-MB-231 and MCF-7) and ovarian (HEY-T30 and SKOV-3) cancer cell lines that were exposed to HDACi (panobinostat or vorinostat), PARPi (talazoparib or olaparib), decitabine, or their combinations. HDACi, PARPi, and decitabine combinations had synergistic cytotoxicity (assessed by MTT and clonogenic assays) in all cell lines (combination index < 1). Clonogenic assays confirmed the sensitivity of breast and ovarian cancer cell lines to the three-drug combinations (panobinostat, talazoparib, and decitabine; panobinostat, olaparib, and decitabine; vorinostat, talazoparib, and decitabine; vorinostat, olaparib, and decitabine). Cell proliferation was inhibited by 48-70%, and Annexin V positivity was 42-59% in all cell lines exposed to the three-drug combinations. Western blot analysis showed protein PARylation inhibition, caspase 3 and PARP1 cleavage, and c-MYC down-regulation. The three-drug combinations induced more DNA damage (increased phosphorylation of histone 2AX) than the individual drugs, impaired the DNA repair pathways, and altered the epigenetic regulation of gene expression. These results indicate that HDACi, PARPi, and decitabine combinations should be further explored in these tumor types. Further clinical validation is warranted to assess their safety and efficacy.

Current status and advances to improving drug delivery in diffuse intrinsic pontine glioma

Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma - DIPG), is the primary cause of brain tumor-related death in pediatric patients. DIPG is characterized by a median survival of <12 months from diagnosis, harboring the worst 5-year survival rate of any cancer. Corticosteroids and radiation are the mainstay of therapy; however, they only provide transient relief from the devastating neurological symptoms. Numerous therapies have been investigated for DIPG, but the majority have been unsuccessful in demonstrating a survival benefit beyond radiation alone. Although many barriers hinder brain drug delivery in DIPG, one of the most significant challenges is the blood-brain barrier (BBB). Therapeutic compounds must possess specific properties to enable efficient passage across the BBB. In brain cancer, the BBB is referred to as the blood-brain tumor barrier (BBTB), where tumors disrupt the structure and function of the BBB, which may provide opportunities for drug delivery. However, the biological characteristics of the brainstem's BBB/BBTB, both under normal physiological conditions and in response to DIPG, are poorly understood, which further complicates treatment. Better characterization of the changes that occur in the BBB/BBTB of DIPG patients is essential, as this informs future treatment strategies. Many novel drug delivery technologies have been investigated to bypass or disrupt the BBB/BBTB, including convection enhanced delivery, focused ultrasound, nanoparticle-mediated delivery, and intranasal delivery, all of which are yet to be clinically established for the treatment of DIPG. Herein, we review what is known about the BBB/BBTB and discuss the current status, limitations, and advances of conventional and novel treatments to improving brain drug delivery in DIPG.

Metabolic Roles of HIF1, c-Myc, and p53 in Glioma Cells

The metabolic reprogramming that promotes tumorigenesis in glioblastoma is induced by dynamic alterations in the hypoxic tumor microenvironment, as well as in transcriptional and signaling networks, which result in changes in global genetic expression. The signaling pathways PI3K/AKT/mTOR and RAS/RAF/MEK/ERK stimulate cell metabolism, either directly or indirectly, by modulating the transcriptional factors p53, HIF1, and c-Myc. The overexpression of HIF1 and c-Myc, master regulators of cellular metabolism, is a key contributor to the synthesis of bioenergetic molecules that mediate glioma cell transformation, proliferation, survival, migration, and invasion by modifying the transcription levels of key gene groups involved in metabolism. Meanwhile, the tumor-suppressing protein p53, which negatively regulates HIF1 and c-Myc, is often lost in glioblastoma. Alterations in this triad of transcriptional factors induce a metabolic shift in glioma cells that allows them to adapt and survive changes such as mutations, hypoxia, acidosis, the presence of reactive oxygen species, and nutrient deprivation, by modulating the activity and expression of signaling molecules, enzymes, metabolites, transporters, and regulators involved in glycolysis and glutamine metabolism, the pentose phosphate cycle, the tricarboxylic acid cycle, and oxidative phosphorylation, as well as the synthesis and degradation of fatty acids and nucleic acids. This review summarizes our current knowledge on the role of HIF1, c-Myc, and p53 in the genic regulatory network for metabolism in glioma cells, as well as potential therapeutic inhibitors of these factors.

Fimepinostat Impairs NF-κB and PI3K/AKT Signaling and Enhances Gemcitabine Efficacy in H3.3K27M-Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is the most aggressive pediatric brain tumor, and the oncohistone H3.3K27M mutation is associated with significantly worse clinical outcomes. Despite extensive research efforts, effective approaches for treating DIPG are lacking. Through drug screening, we identified the combination of gemcitabine and fimepinostat as a potent therapeutic intervention for H3.3K27M DIPG. H3.3K27M facilitated gemcitabine-induced apoptosis in DIPG, and gemcitabine stabilized and activated p53, including increasing chromatin accessibility for p53 at apoptosis-related loci. Gemcitabine simultaneously induced a prosurvival program in DIPG through activation of RELB-mediated NF-κB signaling. Specifically, gemcitabine induced the transcription of long terminal repeat elements, activated cGAS-STING signaling, and stimulated noncanonical NF-κB signaling. A drug screen in gemcitabine-treated DIPG cells revealed that fimepinostat, a dual inhibitor of HDAC and PI3K, effectively suppressed the gemcitabine-induced NF-κB signaling in addition to blocking PI3K/AKT activation. Combination therapy comprising gemcitabine and fimepinostat elicited synergistic antitumor effects in vitro and in orthotopic H3.3K27M DIPG xenograft models. Collectively, p53 activation using gemcitabine and suppression of RELB-mediated NF-κB activation and PI3K/AKT signaling using fimepinostat is a potential therapeutic strategy for treating H3.3K27M DIPG.

SIGNIFICANCE

Gemcitabine activates p53 and induces apoptosis to elicit antitumor effects in H3.3K27M DIPG, which can be enhanced by blocking NF-κB and PI3K/AKT signaling with fimepinostat, providing a synergistic combination therapy for DIPG.

The dual HDAC and PI3K inhibitor, CUDC‑907, inhibits tumor growth and stem‑like properties by suppressing PTX3 in neuroblastoma

Neuroblastoma (NB) is one of the common solid tumors in childhood and poses a threat to the lives of children. Patients with advanced‑stage or recurrent NB have a poor prognosis. CUDC‑907, as a novel dual‑target inhibitor of histone deacetylase (HDAC) and phosphatidylinositol‑3‑kinase (PI3K), has been proven to play an antitumor role in several types of tumors. However, the exact role of CUDC‑907 in NB remains unclear. In the present study, in vivo and in vitro assays were performed to investigate the anti‑NB activity of CUDC‑907. Pentraxin 3 (PTX3) small interfering RNA (siRNA) and PTX3 overexpression plasmid were transfected into cells to define the underlying mechanisms of CUDC‑907. Tumor tissues and clinical information were collected and immunohistochemistry (IHC) was conducted to analyze the association between the expression of HDAC1, HDAC2, HDAC3 and CD44, and the prognosis of patients with NB. The results indicated that CUDC‑907 significantly inhibited the proliferation and migration, and induced the apoptosis of NB cells, downregulating the expression level of MYCN, and suppressing the PI3K/AKT and MAPK/ERK pathways. Furthermore, CUDC‑907 suppressed the stem‑like properties of NB cells by inhibiting PTX3, a ligand and upstream protein of CD44. IHC revealed that the high expression of HDAC1, 2, 3 and CD44 was associated with a poor prognosis of patients with NB. On the whole, these findings indicate that CUDC‑907 may be developed into a possible therapeutic approach for patients with NB.

Current and future therapeutic strategies for high-grade gliomas leveraging the interplay between epigenetic regulators and kinase signaling networks

Targeted therapies, including small molecule inhibitors directed against aberrant kinase signaling and chromatin regulators, are emerging treatment options for high-grade gliomas (HGG). However, when translating these inhibitors into the clinic, their efficacy is generally limited to partial and transient responses. Recent studies in models of high-grade gliomas reveal a convergence of epigenetic regulators and kinase signaling networks that often cooperate to promote malignant properties and drug resistance. This review examines the interplay between five well-characterized groups of chromatin regulators, including the histone deacetylase (HDAC) family, bromodomain and extraterminal (BET)-containing proteins, protein arginine methyltransferase (PRMT) family, Enhancer of zeste homolog 2 (EZH2), and lysine-specific demethylase 1 (LSD1), and various signaling pathways essential for cancer cell growth and progression. These specific epigenetic regulators were chosen for review due to their targetability via pharmacological intervention and clinical relevance. Several studies have demonstrated improved efficacy from the dual inhibition of the epigenetic regulators and signaling kinases. Overall, the interactions between epigenetic regulators and kinase signaling pathways are likely influenced by several factors, including individual glioma subtypes, preexisting mutations, and overlapping/interdependent functions of the chromatin regulators. The insights gained by understanding how the genome and epigenome cooperate in high-grade gliomas will guide the design of future therapeutic strategies that utilize dual inhibition with improved efficacy and overall survival.

Research on the Regulatory Mechanism of Ginseng on the Tumor Microenvironment of Colorectal Cancer based on Network Pharmacology and Bioinformatics Validation

BACKGROUND

A network pharmacology study on the biological action of ginseng in the treatment of colorectal cancer (CRC) by regulating the tumor microenvironment (TME).

OBJECTIVES

To investigate the potential mechanism of action of ginseng in the treatment of CRC by regulating TME.

METHODS

This research employed network pharmacology, molecular docking techniques, and bioinformatics validation. Firstly, the active ingredients and the corresponding targets of ginseng were retrieved using the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP), the Traditional Chinese Medicine Integrated Database (TCMID), and the Traditional Chinese Medicine Database@Taiwan (TCM Database@Taiwan). Secondly, the targets related to CRC were retrieved using Genecards, Therapeutic Target Database (TTD), and Online Mendelian Inheritance in Man (OMIM). Tertiary, the targets related to TME were derived from screening the GeneCards and National Center for Biotechnology Information (NCBI)-Gene. Then the common targets of ginseng, CRC, and TME were obtained by Venn diagram. Afterward, the Protein-protein interaction (PPI) network was constructed in the STRING 11.5 database, intersecting targets identified by PPI analysis were introduced into Cytoscape 3.8.2 software cytoHubba plugin, and the final determination of core targets was based on degree value. The OmicShare Tools platform was used to analyze the Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the core targets. Autodock and PyMOL were used for molecular docking verification and visual data analysis of docking results. Finally, we verified the core targets by Gene Expression Profiling Interactive Analysis (GEPIA) and Human Protein Atlas (HPA) databases in bioinformatics.

RESULTS

A total of 22 active ingredients and 202 targets were identified to be closely related to the TME of CRC. PPI network mapping identified SRC, STAT3, PIK3R1, HSP90AA1, and AKT1 as possible core targets. Go enrichment analysis showed that it was mainly involved in T cell co-stimulation, lymphocyte co-stimulation, growth hormone response, protein input, and other biological processes; KEGG pathway analysis found 123 related signal pathways, including EGFR tyrosine kinase inhibitor resistance, chemokine signaling pathway, VEGF signaling pathway, ErbB signaling pathway, PD-L1 expression and PD-1 checkpoint pathway in cancer, etc. The molecular docking results showed that the main chemical components of ginseng have a stable binding activity to the core targets. The results of the GEPIA database showed that the mRNA levels of PIK3R1 were significantly lowly expressed and HSP90AA1 was significantly highly expressed in CRC tissues. Analysis of the relationship between core target mRNA levels and the pathological stage of CRC showed that the levels of SRC changed significantly with the pathological stage. The HPA database results showed that the expression levels of SRC were increased in CRC tissues, while the expression of STAT3, PIK3R1, HSP90AA1, and AKT1 were decreased in CRC tissues.

CONCLUSION

Ginseng may act on SRC, STAT3, PIK3R1, HSP90AA1, and AKT1 to regulate T cell costimulation, lymphocyte costimulation, growth hormone response, protein input as a molecular mechanism regulating TME for CRC. It reflects the multi-target and multi-pathway role of ginseng in modulating TME for CRC, which provides new ideas to further reveal its pharmacological basis, mechanism of action and new drug design and development.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

Glioma is the most aggressive and malignant type of primary brain tumor, comprises the majority of central nervous system deaths, and is categorized into different subgroups according to its histological characteristics, including astrocytomas, oligodendrogliomas, glioblastoma multiforme (GBM), and mixed tumors. The forkhead box (FOX) transcription factors comprise a collection of proteins that play various roles in numerous complex molecular cascades and have been discovered to be differentially expressed in distinct glioma subtypes. FOXM1 and FOXOs have been recognized as crucial transcription factors in tumor cells, including glioma cells. Accumulating data indicates that FOXM1 acts as an oncogene in various types of cancers, and a significant part of studies has investigated its function in glioma. Although recent studies considered FOXO subgroups as tumor suppressors, there are pieces of evidence that they may have an oncogenic role. This review will discuss the subtle functions of FOXOs and FOXM1 in gliomas, dissecting their regulatory network with other proteins, microRNAs and their role in glioma progression, including stem cell differentiation and therapy resistance/sensitivity, alongside highlighting recent pharmacological progress for modulating their expression.

ATM inhibition enhances the efficacy of radiation across distinct molecular subgroups of pediatric high-grade glioma

BACKGROUND

Pediatric high-grade glioma (pHGG) is largely incurable and accounts for most brain tumor-related deaths in children. Radiation is a standard therapy, yet the benefit from this treatment modality is transient, and most children succumb to disease within 2 years. Recent large-scale genomic studies suggest that pHGG has alterations in DNA damage response (DDR) pathways that induce resistance to DNA damaging agents. The aim of this study was to evaluate the therapeutic potential and molecular consequences of combining radiation with selective DDR inhibition in pHGG.

METHODS

We conducted an unbiased screen in pHGG cells that combined radiation with clinical candidates targeting the DDR and identified the ATM inhibitor AZD1390. Subsequently, we profiled AZD1390 + radiation in an extensive panel of early passage pHGG cell lines, mechanistically characterized response to the combination in vitro in sensitive and resistant cells and evaluated the combination in vivo using TP53 wild-type and TP53 mutant orthotopic xenografts.

RESULTS

AZD1390 significantly potentiated radiation across molecular subgroups of pHGG by increasing mutagenic nonhomologous end joining and augmenting genomic instability. In contrast to previous reports, ATM inhibition significantly improved the efficacy of radiation in both TP53 wild-type and TP53 mutant isogenic cell lines and distinct orthotopic xenograft models. Furthermore, we identified a novel mechanism of resistance to AZD1390 + radiation that was marked by an attenuated ATM pathway response which dampened sensitivity to ATM inhibition and induced synthetic lethality with ATR inhibition.

CONCLUSIONS

Our study supports the clinical evaluation of AZD1390 in combination with radiation in pediatric patients with HGG.

RNA methylation, homologous recombination repair and therapeutic resistance

Homologous recombination (HR) repair of DNA double-strand breaks (DSBs) is critical for maintaining genomic integrity and stability. Defects in HR increase the risk of tumorigenesis. However, many human tumors exhibit enhanced HR repair capabilities, consequently endowing tumor cells with resistance to DNA-damaging chemotherapy and radiotherapy. This review summarizes the role of RNA methylation in HR repair and therapeutic resistance in human tumors. We also analyzed the interactions between RNA methylation and other HR-modulating modifications including histone acetylation, histone deacetylation, ubiquitination, deubiquitination, protein arginine methylation, and gene transcription. This review proposes that targeting RNA methylation is a promising approach to overcoming HR-mediated therapeutic resistance.

Foxm1 haploinsufficiency drives clonal hematopoiesis and promotes a stress-related transition to hematologic malignancy in mice

Clonal hematopoiesis plays a critical role in the initiation and development of hematologic malignancies. In patients with del(5q) myelodysplastic syndrome (MDS), the transcription factor FOXM1 is frequently downregulated in CD34+ cells. In this study, we demonstrated that Foxm1 haploinsufficiency disturbed normal hematopoiesis and conferred a competitive repopulation advantage for a short period. However, it impaired the long-term self-renewal capacity of hematopoietic stem cells, recapitulating the phenotypes of abnormal hematopoietic stem cells observed in patients with MDS. Moreover, heterozygous inactivation of Foxm1 led to an increase in DNA damage in hematopoietic stem/progenitor cells (HSPCs). Foxm1 haploinsufficiency induced hematopoietic dysplasia in a mouse model with LPS-induced chronic inflammation and accelerated AML-ETO9a-mediated leukemogenesis. We have also identified Parp1, an important enzyme that responds to various types of DNA damage, as a target of Foxm1. Foxm1 haploinsufficiency decreased the ability of HSPCs to efficiently repair DNA damage by downregulating Parp1 expression. Our findings suggest that the downregulation of the Foxm1-Parp1 molecular axis may promote clonal hematopoiesis and reduce genome stability, contributing to del(5q) MDS pathogenesis.

HDAC-an important target for improving tumor radiotherapy resistance

Radiotherapy is an important means of tumor treatment, but radiotherapy resistance has been a difficult problem in the comprehensive treatment of clinical tumors. The mechanisms of radiotherapy resistance include the repair of sublethal damage and potentially lethal damage of tumor cells, cell repopulation, cell cycle redistribution, and reoxygenation. These processes are closely related to the regulation of epigenetic modifications. Histone deacetylases (HDACs), as important regulators of the epigenetic structure of cancer, are widely involved in the formation of tumor radiotherapy resistance by participating in DNA damage repair, cell cycle regulation, cell apoptosis, and other mechanisms. Although the important role of HDACs and their related inhibitors in tumor therapy has been reviewed, the relationship between HDACs and radiotherapy has not been systematically studied. This article systematically expounds for the first time the specific mechanism by which HDACs promote tumor radiotherapy resistance in vivo and in vitro and the clinical application prospects of HDAC inhibitors, aiming to provide a reference for HDAC-related drug development and guide the future research direction of HDAC inhibitors that improve tumor radiotherapy resistance.

Oncohistones and disrupted development in pediatric-type diffuse high-grade glioma

Recurrent, clonal somatic mutations in histone H3 are molecular hallmarks that distinguish the genetic mechanisms underlying pediatric and adult high-grade glioma (HGG), define biological subgroups of diffuse glioma, and highlight connections between cancer, development, and epigenetics. These oncogenic mutations in histones, now termed "oncohistones", were discovered through genome-wide sequencing of pediatric diffuse high-grade glioma. Up to 80% of diffuse midline glioma (DMG), including diffuse intrinsic pontine glioma (DIPG) and diffuse glioma arising in other midline structures including thalamus or spinal cord, contain histone H3 lysine 27 to methionine (K27M) mutations or, rarely, other alterations that result in a depletion of H3K27me3 similar to that induced by H3 K27M. This subgroup of glioma is now defined as diffuse midline glioma, H3K27-altered. In contrast, histone H3 Gly34Arg/Val (G34R/V) mutations are found in approximately 30% of diffuse glioma arising in the cerebral hemispheres of older adolescents and young adults, now classified as diffuse hemispheric glioma, H3G34-mutant. Here, we review how oncohistones modulate the epigenome and discuss the mutational landscape and invasive properties of histone mutant HGGs of childhood. The distinct mechanisms through which oncohistones and other mutations rewrite the epigenetic landscape provide novel insights into development and tumorigenesis and may present unique vulnerabilities for pHGGs. Lessons learned from these rare incurable brain tumors of childhood may have broader implications for cancer, as additional high- and low-frequency oncohistone mutations have been identified in other tumor types.

Radiotherapy and radio-sensitization in H3K27M -mutated diffuse midline gliomas

BACKGROUND

H3^K27M mutated diffuse midline gliomas (DMGs) are extremely aggressive and the leading cause of cancer-related deaths in pediatric brain tumors with 5-year survival <1%. Radiotherapy is the only established adjuvant treatment of H3^K27M DMGs; however, the radio-resistance is commonly observed.

METHODS

We summarized current understandings of the molecular responses of H3^K27M DMGs to radiotherapy and provide crucial insights into current advances in radiosensitivity enhancement.

RESULTS

Ionizing radiation (IR) can mainly inhibit tumor cell growth by inducing DNA damage regulated by the cell cycle checkpoints and DNA damage repair (DDR) system. In H3K27M DMGs, the aberrant genetic and epigenetic changes, stemness genotype, and epithelial-mesenchymal transition (EMT) disrupt the cell cycle checkpoints and DDR system by altering the associated regulatory signaling pathways, which leads to the development of radio-resistance.

CONCLUSIONS

The advances in mechanisms of radio-resistance in H3^K27M  DMGs promote the potential targets to enhance the sensitivity to radiotherapy.

Developing H3K27M mutant selective radiosensitization strategies in diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is a rare but highly lethal pediatric and adolescent tumor located in the pons of the brainstem. DIPGs harbor unique and specific pathological and molecular alterations, such as the hallmark lysine 27-to-methionine (H3K27M) mutation in histone H3, which lead to global changes in the epigenetic landscape and drive tumorigenesis. While fractionated radiotherapy, the current standard of care, improves symptoms and delays tumor progression, DIPGs inevitably recur, and despite extensive efforts chemotherapy-driven radiosensitization strategies have failed to improve survival. Advances in our understanding of the role of epigenetics in the cellular response to radiation-induced DNA damage, however, offer new opportunities to develop combinational therapeutic strategies selective for DIPGs expressing H3K27M. In this review, we provide an overview of preclinical studies that explore potential radiosensitization strategies targeting the unique epigenetic landscape of H3K27M mutant DIPG. We further discuss opportunities to selectively radiosensitize DIPG through strategic inhibition of the radiation-induced DNA damage response. Finally, we discuss the potential for using radiation to induce anti-tumor immune responses that may be potentiated in DIPG by radiosensitizing-therapeutic strategies.

Combined PARP inhibitors and small molecular inhibitors in solid tumor treatment (Review)

With the development of precision medicine, targeted therapy has attracted extensive attention. Poly(ADP‑ribose) polymerase inhibitors (PARPi) are critical clinical drugs designed to induce cell death and are major antitumor targeted agents. However, preclinical and clinical data have revealed the limitations of PARPi monotherapy. Therefore, their combination with other targeted drugs has become a research hotspot in tumor treatment. Recent studies have demonstrated the critical role of small molecular inhibitors in multiple haematological cancers and solid tumors via cellular signalling modulation, exhibiting potential as a combined pharmacotherapy. In the present review, studies focused on small molecular inhibitors targeting the homologous recombination pathway were summarized and clinical trials evaluating the safety and efficacy of combined treatment were discussed.

Epigenetic programming of pediatric high-grade glioma: Pushing beyond proof of concept to clinical benefit

Pediatric high-grade gliomas (pHGG) are a molecularly diverse group of malignancies, each incredibly aggressive and in dire need of treatment advancements. Genomic analysis has revolutionized our understanding of these tumors, identifying biologically relevant subgroups with differing canonical mutational profiles that vary based on tumor location and age. In particular, the discovery of recurrent histone H3 mutations (H3K27M in diffuse midline glioma, H3G34R/V in hemispheric pediatric high-grade gliomas) as unique "oncohistone" drivers revealed epigenetic dysregulation as a hallmark of pediatric high-grade gliomas oncogenesis. While reversing this signature through epigenetic programming has proven effective in several pre-clinical survival models, early results from pediatric high-grade gliomas clinical trials suggest that epigenetic modifier monotherapy will likely not provide long-term disease control. In this review we summarize the genetic, epigenetic, and cellular heterogeneity of pediatric high-grade gliomas, and highlight potential paths forward for epigenetic programming in this devastating disease.

A druggable addiction to de novo pyrimidine biosynthesis in diffuse midline glioma

Diffuse midline glioma (DMG) is a uniformly fatal pediatric cancer driven by oncohistones that do not readily lend themselves to drug development. To identify druggable targets for DMG, we conducted a genome-wide CRISPR screen that reveals a DMG selective dependency on the de novo pathway for pyrimidine biosynthesis. This metabolic vulnerability reflects an elevated rate of uridine/uracil degradation that depletes DMG cells of substrates for the alternate salvage pyrimidine biosynthesis pathway. A clinical stage inhibitor of DHODH (rate-limiting enzyme in the de novo pathway) diminishes uridine-5'-phosphate (UMP) pools, generates DNA damage, and induces apoptosis through suppression of replication forks-an "on-target" effect, as shown by uridine rescue. Matrix-assisted laser desorption/ionization (MALDI) mass spectroscopy imaging demonstrates that this DHODH inhibitor (BAY2402234) accumulates in the brain at therapeutically relevant concentrations, suppresses de novo pyrimidine biosynthesis in vivo, and prolongs survival of mice bearing intracranial DMG xenografts, highlighting BAY2402234 as a promising therapy against DMGs.

Glioblastoma: Current Status, Emerging Targets, and Recent Advances

Glioblastoma (GBM) is a highly malignant brain tumor characterized by a heterogeneous population of genetically unstable and highly infiltrative cells that are resistant to chemotherapy. Although substantial efforts have been invested in the field of anti-GBM drug discovery in the past decade, success has primarily been confined to the preclinical level, and clinical studies have often been hampered due to efficacy-, selectivity-, or physicochemical property-related issues. Thus, expansion of the list of molecular targets coupled with a pragmatic design of new small-molecule inhibitors with central nervous system (CNS)-penetrating ability is required to steer the wheels of anti-GBM drug discovery endeavors. This Perspective presents various aspects of drug discovery (challenges in GBM drug discovery and delivery, therapeutic targets, and agents under clinical investigation). The comprehensively covered sections include the recent medicinal chemistry campaigns embarked upon to validate the potential of numerous enzymes/proteins/receptors as therapeutic targets in GBM.

Molecular Genetics and Targeted Therapies for Paediatric High-grade Glioma

Brain tumours are the leading cause of paediatric cancer-associated death worldwide. High-grade glioma (HGG) represents a main cause of paediatric brain tumours and is associated with poor prognosis despite surgical and chemoradiotherapeutic advances. The molecular genetics of paediatric HGG (pHGG) are distinct from those in adults, and therefore, adult clinical trial data cannot be extrapolated to children. Compared to adult HGG, pHGG is characterised by more frequent mutations in PDGFRA, TP53 and recurrent K27M and G34R/V mutations on histone H3. Ongoing trials are investigating novel targeted therapies in pHGG. Promising results have been achieved with BRAF/MEK and PI3K/mTOR inhibitors. Combination of PI3K/mTOR, EGFR, CDK4/6, and HDAC inhibitors are potentially viable options. Inhibitors targeting the UPS proteosome, ADAM10/17, IDO, and XPO1 are more novel and are being investigated in early-phase trials. Despite preclinical and clinical trials holding promise for the discovery of effective pHGG treatments, several issues persist. Inadequate blood-brain barrier penetration, unfavourable pharmacokinetics, dose-limiting toxicities, long-term adverse effects in the developing child, and short-lived duration of response due to relapse and resistance highlight the need for further improvement. Future pHGG management will largely depend on selecting combination therapies which work synergistically based on a sound knowledge of the underlying molecular target pathways. A systematic investigation of multimodal therapy with chemoradiotherapy, surgery, target agents and immunotherapy is paramount. This review provides a comprehensive overview of pHGG focusing on molecular genetics and novel targeted therapies. The diagnostics, genetic discrepancies with adults and their clinical implications, as well as conventional treatment approaches are discussed.

Small Molecule Inhibitors in Adult High-Grade Glioma: From the Past to the Future

Glioblastoma is the most common primary malignant tumor in the brain and has a dismal prognosis despite patients accepting standard therapies. Alternation of genes and deregulation of proteins, such as receptor tyrosine kinase, PI3K/Akt, PKC, Ras/Raf/MEK, histone deacetylases, poly (ADP-ribose) polymerase (PARP), CDK4/6, branched-chain amino acid transaminase 1 (BCAT1), and Isocitrate dehydrogenase (IDH), play pivotal roles in the pathogenesis and progression of glioma. Simultaneously, the abnormalities change the cellular biological behavior and microenvironment of tumor cells. The differences between tumor cells and normal tissue become the vulnerability of tumor, which can be taken advantage of using targeted therapies. Small molecule inhibitors, as an important part of modern treatment for cancers, have shown significant efficacy in hematologic cancers and some solid tumors. To date, in glioblastoma, there have been more than 200 clinical trials completed or ongoing in which trial designers used small molecules as monotherapy or combination regimens to correct the abnormalities. In this review, we summarize the dysfunctional molecular mechanisms and highlight the outcomes of relevant clinical trials associated with small-molecule targeted therapies. Based on the outcomes, the main findings were that small-molecule inhibitors did not bring more benefit to newly diagnosed glioblastoma, but the clinical studies involving progressive glioblastoma usually claimed “noninferiority” compared with historical results. However, as to the clinical inferiority trial, similar dosing regimens should be avoided in future clinical trials.

Promising Chemotherapy for Malignant Pediatric Brain Tumor in Recent Biological Insights

Brain tumors are the most widespread malignancies in children around the world. Chemotherapy plays a critical role in the treatment of these tumors. Although the current chemotherapy process has a remarkable outcome for a certain subtype of brain tumor, improving patient survival is still a major challenge. Further intensive treatment with conventional non-specific chemotherapy could cause additional adverse reactions without significant advancement in survival. Recently, patient derived brain tumor, xenograft, and whole genome analysis using deep sequencing technology has made a significant contribution to our understanding of cancer treatment. This realization has changed the focus to new agents, targeting the molecular pathways that are critical to tumor survival or proliferation. Thus, many novel drugs targeting epigenetic regulators or tyrosine kinase have been developed. These selective drugs may have less toxicity in normal cells and are expected to be more effective than non-specific chemotherapeutics. This review will summarize the latest novel targets and corresponding candidate drugs, which are promising chemotherapy for brain tumors according to the biological insights.

Dual Targeting of PI3K and HDAC by CUDC-907 Inhibits Pediatric Neuroblastoma Growth

Simple Summary

High-risk neuroblastoma (NB) is an aggressive cancer of very young children and accounts for almost 15% of all pediatric cancer deaths. Current therapies include high-dose chemotherapy and radiation, which have long-term toxic side effects. Despite these intensive therapies, the overall 5-year survival rate of NB is less than 50%. Therefore, developing novel therapeutic approaches targeting the molecular mechanisms that drive NB progression is very important. In the present study, we repurpose CUDC-907, a dual inhibitor of PI3K and histone deacetylases. These regulators are known to regulate MYCN expression, a key prognostic marker of NB. CUDC-907 potently inhibits NB growth and 3D spheroid tumor growth by inhibiting PI3K, HDAC, and MYCN. Overall, our pre-clinical data demonstrate that repurposing CUDC-907 as a single drug is a novel and effective therapeutic approach for NB.

Abstract

The dysregulation of PI3K, HDACs, and MYCN are well known for promoting multiple cancer types, including neuroblastoma (NB). Targeting the upstream regulators of MYCN, including HDACs and PI3K, was shown to suppress cancer growth. In the present study, we analyze different NB patient datasets to reveal that high PI3K and HDAC expression is correlated with overall poor NB patient survival. High PI3K level is also found to be associated with high MYCN level and NB stage progression. We repurpose a dual inhibitor CUDC-907 as a single agent to directly target both PI3K and HDAC in NB. We use in vitro methodologies to determine the efficacy and selectivity of CUDC-907 using six NB and three control fibroblast cell lines. Our results show that CUDC-907 significantly inhibits NB proliferation and colony growth, induces apoptosis, blocks cell cycle progression, inhibits MYCN, and enhances H3K9Ac levels by inhibiting the PI3K/AKT signaling pathway and HDAC function. Furthermore, CUDC-907 significantly inhibits NB tumor growth in a 3D spheroid tumor model that recapitulates the in vivo tumor growth. Overall, our findings highlight that the dual inhibition of PI3K and HDAC by CUDC-907 is an effective therapeutic strategy for NB and other MYC-dependent cancers.

Therapeutic Targets in Diffuse Midline Gliomas-An Emerging Landscape

Simple Summary

Diffuse midline gliomas (DMGs) remain one of the most devastating childhood brain tumour types, for which there is currently no known cure. In this review we provide a summary of the existing knowledge of the molecular mechanisms underlying the pathogenesis of this disease, highlighting current analyses and novel treatment propositions. Together, the accumulation of these data will aid in the understanding and development of more effective therapeutic options for the treatment of DMGs.

Abstract

Diffuse midline gliomas (DMGs) are invariably fatal pediatric brain tumours that are inherently resistant to conventional therapy. In recent years our understanding of the underlying molecular mechanisms of DMG tumorigenicity has resulted in the identification of novel targets and the development of a range of potential therapies, with multiple agents now being progressed to clinical translation to test their therapeutic efficacy. Here, we provide an overview of the current therapies aimed at epigenetic and mutational drivers, cellular pathway aberrations and tumor microenvironment mechanisms in DMGs in order to aid therapy development and facilitate a holistic approach to patient treatment.

Pharmaco-proteogenomic profiling of pediatric diffuse midline glioma to inform future treatment strategies

Diffuse midline glioma (DMG) is a deadly pediatric and adolescent central nervous system (CNS) tumor localized along the midline structures of the brain atop the spinal cord. With a median overall survival (OS) of just 9–11-months, DMG is characterized by global hypomethylation of histone H3 at lysine 27 (H3K27me3), driven by recurring somatic mutations in H3 genes including, HIST1H3B/C (H3.1K27M) or H3F3A (H3.3K27M), or through overexpression of EZHIP in patients harboring wildtype H3. The recent World Health Organization’s 5th Classification of CNS Tumors now designates DMG as, ‘H3 K27-altered’, suggesting that global H3K27me3 hypomethylation is a ubiquitous feature of DMG and drives devastating transcriptional programs for which there are no treatments. H3-alterations co-segregate with various other somatic driver mutations, highlighting the high-level of intertumoral heterogeneity of DMG. Furthermore, DMG is also characterized by very high-level intratumoral diversity with tumors harboring multiple subclones within each primary tumor. Each subclone contains their own combinations of driver and passenger lesions that continually evolve, making precision-based medicine challenging to successful execute. Whilst the intertumoral heterogeneity of DMG has been extensively investigated, this is yet to translate to an increase in patient survival. Conversely, our understanding of the non-genomic factors that drive the rapid growth and fatal nature of DMG, including endogenous and exogenous microenvironmental influences, neurological cues, and the posttranscriptional and posttranslational architecture of DMG remains enigmatic or at best, immature. However, these factors are likely to play a significant role in the complex biological sequelae that drives the disease. Here we summarize the heterogeneity of DMG and emphasize how analysis of the posttranslational architecture may improve treatment paradigms. We describe factors that contribute to treatment response and disease progression, as well as highlight the potential for pharmaco-proteogenomics (i.e., the integration of genomics, proteomics and pharmacology) in the management of this uniformly fatal cancer.

Molecular mechanisms involved in DNA repair in human cancers: An overview of PI3k/Akt signaling and PIKKs crosstalk

The cellular genome is frequently subjected to abundant endogenous and exogenous factors that induce DNA damage. Most of the Phosphatidylinositol 3-kinase-related kinases (PIKKs) family members are activated in response to DNA damage and are the most important DNA damage response (DDR) proteins. The DDR system protects the cells against the wrecking effects of these genotoxicants and repairs the DNA damage caused by them. If the DNA damage is severe, such as when DNA is the goal of chemo-radiotherapy, the DDR drives cells toward cell cycle arrest and apoptosis. Some intracellular pathways, such as PI3K/Akt, which is overactivated in most cancers, could stimulate the DDR process and failure of chemo-radiotherapy with the increasing repair of damaged DNA. This signaling pathway induces DNA repair through the regulation of proteins that are involved in DDR like BRCA1, HMGB1, and P53. In this review, we will focus on the crosstalk of the PI3K/Akt and PIKKs involved in DDR and then discuss current achievements in the sensitization of cancer cells to chemo-radiotherapy by PI3K/Akt inhibitors.

Patient-derived models recapitulate heterogeneity of molecular signatures and drug response in pediatric high-grade glioma

Pediatric high-grade glioma (pHGG) is a major contributor to cancer-related death in children. In vitro and in vivo disease models reflecting the intimate connection between developmental context and pathogenesis of pHGG are essential to advance understanding and identify therapeutic vulnerabilities. Here we report establishment of 21 patient-derived pHGG orthotopic xenograft (PDOX) models and eight matched cell lines from diverse groups of pHGG. These models recapitulate histopathology, DNA methylation signatures, mutations and gene expression patterns of the patient tumors from which they were derived, and include rare subgroups not well-represented by existing models. We deploy 16 new and existing cell lines for high-throughput screening (HTS). In vitro HTS results predict variable in vivo response to PI3K/mTOR and MEK pathway inhibitors. These unique new models and an online interactive data portal for exploration of associated detailed molecular characterization and HTS chemical sensitivity data provide a rich resource for pediatric brain tumor research.

FOXM1 is required for small cell lung cancer tumorigenesis and associated with poor clinical prognosis

Small cell lung cancer (SCLC) continues to cause poor clinical outcomes due to limited advances in sustained treatments for rapid cancer cell proliferation and progression. The transcriptional factor Forkhead Box M1 (FOXM1) regulates cell proliferation, tumor initiation, and progression in multiple cancer types. However, its biological function and clinical significance in SCLC remain unestablished. Analysis of the Cancer Cell Line Encyclopedia and SCLC datasets in the present study disclosed significant upregulation of FOXM1 mRNA in SCLC cell lines and tissues. Gene set enrichment analysis (GSEA) revealed that FOXM1 is positively correlated with pathways regulating cell proliferation and DNA damage repair, as evident from sensitization of FOXM1-depleted SCLC cells to chemotherapy. Furthermore, Foxm1 knockout inhibited SCLC formation in the Rb1fl/flTrp53fl/flMycLSL/LSL (RPM) mouse model associated with increased levels of neuroendocrine markers, Ascl1 and Cgrp, and decrease in Yap1. Consistently, FOXM1 depletion in NCI-H1688 SCLC cells reduced migration and enhanced apoptosis and sensitivity to cisplatin and etoposide. SCLC with high FOXM1 expression (N = 30, 57.7%) was significantly correlated with advanced clinical stage, extrathoracic metastases, and decrease in overall survival (OS), compared with the low-FOXM1 group (7.90 vs. 12.46 months). Moreover, the high-FOXM1 group showed shorter progression-free survival after standard chemotherapy, compared with the low-FOXM1 group (3.90 vs. 8.69 months). Our collective findings support the utility of FOXM1 as a prognostic biomarker and potential molecular target for SCLC.

Radiation in Combination With Targeted Agents and Immunotherapies for Pediatric Central Nervous System Tumors - Progress, Opportunities, and Challenges

Pediatric brain tumors are the most common solid tumors in children and represent a heterogenous group of diagnoses. While some are treatable with current standard of care, relapsed/refractory disease is common and some high-risk diagnoses remain incurable. A growing number of therapy options are under development for treatment of CNS tumors, including targeted therapies that disrupt key tumor promoting processes and immunotherapies that promote anti-tumor immune function. While these therapies hold promise, it is likely that single agent treatments will not be sufficient for most high-risk patients and combination strategies will be necessary. Given the central role for radiotherapy for many pediatric CNS tumors, we review current strategies that combine radiation with targeted therapies or immunotherapies. To promote the ongoing development of rational combination treatments, we highlight 1) mechanistic connections between molecular drivers of tumorigenesis and radiation response, 2) ways in which molecular alterations in tumor cells shape the immune microenvironment, and 3) how radiotherapy affects the host immune system. In addition to discussing strategies to maximize efficacy, we review principles that inform safety of combination therapies.

Mesenchymal Epithelial Transition Factor Signaling in Pediatric Nervous System Tumors: Implications for Malignancy and Cancer Stem Cell Enrichment

Malignant nervous system cancers in children are the most devastating and worrisome diseases, specifically due to their aggressive nature and, in some cases, inoperable location in critical regions of the brain and spinal cord, and the impermeable blood-brain barrier that hinders delivery of pharmaco-therapeutic compounds into the tumor site. Moreover, the delicate developmental processes of the nervous system throughout the childhood years adds another limitation to the therapeutic modalities and doses used to treat these malignant cancers. Therefore, pediatric oncologists are charged with the daunting responsibility of attempting to deliver effective cures to these children, yet with limited doses of the currently available therapeutic options in order to mitigate the imminent neurotoxicity of radio- and chemotherapy on the developing nervous system. Various studies reported that c-Met/HGF signaling is affiliated with increased malignancy and stem cell enrichment in various cancers such as high-grade gliomas, high-risk medulloblastomas, and MYCN-amplified, high-risk neuroblastomas. Therapeutic interventions that are utilized to target c-Met signaling in these malignant nervous system cancers have shown benefits in basic translational studies and preclinical trials, but failed to yield significant clinical benefits in patients. While numerous pre-clinical data reported promising results with the use of combinatorial therapy that targets c-Met with other tumorigenic pathways, therapeutic resistance remains a problem, and long-term cures are rare. The possible mechanisms, including the overexpression and activation of compensatory tumorigenic mechanisms within the tumors or ineffective drug delivery methods that may contribute to therapeutic resistance observed in clinical trials are elaborated in this review.

Radiosensitization in Pediatric High-Grade Glioma: Targets, Resistance and Developments

Pediatric high-grade gliomas (pHGG) are the leading cause of cancer-related death in children. These epigenetically dysregulated tumors often harbor mutations in genes encoding histone 3, which contributes to a stem cell-like, therapy-resistant phenotype. Furthermore, pHGG are characterized by a diffuse growth pattern, which, together with their delicate location, makes complete surgical resection often impossible. Radiation therapy (RT) is part of the standard therapy against pHGG and generally the only modality, apart from surgery, to provide symptom relief and a delay in tumor progression. However, as a single treatment modality, RT still offers no chance for a cure. As with most therapeutic approaches, irradiated cancer cells often acquire resistance mechanisms that permit survival or stimulate regrowth after treatment, thereby limiting the efficacy of RT. Various preclinical studies have investigated radiosensitizers in pHGG models, without leading to an improved clinical outcome for these patients. However, our recently improved molecular understanding of pHGG generates new opportunities to (re-)evaluate radiosensitizers in these malignancies. Furthermore, the use of radio-enhancing agents has several benefits in pHGG compared to other cancers, which will be discussed here. This review provides an overview and a critical evaluation of the radiosensitization strategies that have been studied to date in pHGG, thereby providing a framework for improving radiosensitivity of these rapidly fatal brain tumors.

Advanced Pediatric Diffuse Pontine Glioma Murine Models Pave the Way towards Precision Medicine

Diffuse intrinsic pontine gliomas (DIPGs) account for ~15% of pediatric brain tumors, which invariably present with poor survival regardless of treatment mode. Several seminal studies have revealed that 80% of DIPGs harbor H3K27M mutation coded by HIST1H3B, HIST1H3C and H3F3A genes. The H3K27M mutation has broad effects on gene expression and is considered a tumor driver. Determination of the effects of H3K27M on posttranslational histone modifications and gene regulations in DIPG is critical for identifying effective therapeutic targets. Advanced animal models play critical roles in translating these cutting-edge findings into clinical trial development. Here, we review current molecular research progress associated with DIPG. We also summarize DIPG animal models, highlighting novel genomic engineered mouse models (GEMMs) and innovative humanized DIPG mouse models. These models will pave the way towards personalized precision medicine for the treatment of DIPGs.

FK228 sensitizes radioresistant small cell lung cancer cells to radiation

Background

Concurrent thoracic radiation plus chemotherapy is the mainstay of first-line treatment for limited-stage small cell lung cancer (LS-SCLC). Despite initial high responsiveness to combined chemo- and radiotherapy, SCLC almost invariably relapses and develops resistance within one year, leading to poor prognosis in patients with LS-SCLC. Developing new chemical agents that increase ionizing radiation’s cytotoxicity against SCLC is urgently needed.

Results

Dual histone deacetylase (HDAC) and PI3K inhibitor FK228 not only displayed potent anticancer activity, but also enhanced the therapeutic effects of radiotherapy in SCLC cells. Mechanistically, radioresistant SCLC cells exhibit a lower level of histone H3K9 acetylation and a higher expression level of the MRE11-RAD50-NBS1 (MRN) complex and show more efficient and redundant DNA damage repair capacities than radiosensitive SCLC cells. FK228 pretreatment resulted in marked induction of H3k9 acetylation, attenuated homologous recombination (HR) repair competency and impaired non-homologous end joining (NHEJ) repair efficacy, leading to the accumulation of radiation-induced DNA damage and radiosensitization.

Conclusion

The study uncovered that FK228 sensitized human radioresistant SCLC cells to radiation mainly through induction of chromatin decondensation and suppression of DNA damage signaling and repair. Our study provides a rational basis for a further clinical study to test the potential of FK228 as a radiosensitizing agent to increase the radiation-induced tumor cell kill in LS-SCLC patients.

Pathogenetic Features and Current Management of Glioblastoma

Glioblastoma (GBM) is the most common form of primary malignant brain tumor with a devastatingly poor prognosis. The disease does not discriminate, affecting adults and children of both sexes, and has an average overall survival of 12-15 months, despite advances in diagnosis and rigorous treatment with chemotherapy, radiation therapy, and surgical resection. In addition, most survivors will eventually experience tumor recurrence that only imparts survival of a few months. GBM is highly heterogenous, invasive, vascularized, and almost always inaccessible for treatment. Based on all these outstanding obstacles, there have been tremendous efforts to develop alternative treatment options that allow for more efficient targeting of the tumor including small molecule drugs and immunotherapies. A number of other strategies in development include therapies based on nanoparticles, light, extracellular vesicles, and micro-RNA, and vessel co-option. Advances in these potential approaches shed a promising outlook on the future of GBM treatment. In this review, we briefly discuss the current understanding of adult GBM's pathogenetic features that promote treatment resistance. We also outline novel and promising targeted agents currently under development for GBM patients during the last few years with their current clinical status.

Brain stem gliomas and current landscape

PURPOSE

CNS malignancies are currently the most common cause of disease related deaths in children. Although brainstem gliomas are invariably fatal cancers in children, clinical studies against this disease are limited. This review is to lead to a succinct collection of knowledge of known biological mechanisms of this disease and discuss available therapeutics.

METHODS

A hallmark of brainstem gliomas are mutations in the histone H3.3 with the majority of cases expressing the mutation K27M on histone 3.3. Recent studies using whole genome sequencing have revealed other mutations associated with disease. Current standard clinical practice may merely involve radiation and/or chemotherapy with little hope for long term survival. Here we discuss the potential of new therapies.

CONCLUSION

Despite the lack of treatment options using frequently practiced clinical techniques, immunotherapeutic strategies have recently been developed to target brainstem gliomas. To target brainstem gliomas, investigators are evaluating the use of broad non-targeted therapy with immune checkpoint inhibitors. Alternatively, others have begun to explore adoptive T cell strategies against these fatal malignancies.

Fostering Radiation Oncology Physician Scientist Trainees Within a Diverse Workforce: The Radiation Oncology Research Scholar Track

There is a need to foster future generations of radiation oncology physician scientists, but the number of radiation oncologists with sufficient education, training, and funding to make transformative discoveries is relatively small. A large number of MD/PhD graduates have entered he field of radiation oncology over the past 2 decades, but this has not led to a significant cohort of externally funded physician scientists. Because radiation oncologists leading independent research labs have the potential to make transformative discoveries that advance our field and positively affect patients with cancer, we created the Duke Radiation Oncology Research Scholar (RORS) Program. In crafting this program, we sought to eliminate barriers preventing radiation oncology trainees from becoming independent physician scientists. The RORS program integrates the existing American Board of Radiology Holman Pathway with a 2-year post-graduate medical education instructor position with 80% research effort at the same institution. We use a separate match for RORS and traditional residency pathways, which we hope will increase the diversity of our residency program. Since the inception of the RORS program, we have matched 2 trainees into our program. We encourage other radiation oncology residency programs at peer institutions to consider this training pathway as a means to foster the development of independent physician scientists and a diverse workforce in radiation oncology.