Self-renewal is a crucial property of glioblastoma cells that is enabled by the choreographed functions of chromatin regulators and transcription factors. Identifying targetable epigenetic mechanisms ...of self-renewal could therefore represent an important step toward developing effective treatments for this universally lethal cancer. Here we uncover an epigenetic axis of self-renewal mediated by the histone variant macroH2A2. With omics and functional assays deploying patient-derived in vitro and in vivo models, we show that macroH2A2 shapes chromatin accessibility at enhancer elements to antagonize transcriptional programs of self-renewal. macroH2A2 also sensitizes cells to small molecule-mediated cell death via activation of a viral mimicry response. Consistent with these results, our analyses of clinical cohorts indicate that high transcriptional levels of this histone variant are associated with better prognosis of high-grade glioma patients. Our results reveal a targetable epigenetic mechanism of self-renewal controlled by macroH2A2 and suggest additional treatment approaches for glioblastoma patients.
The current standard of care for glioblastoma (GBM) involves a combination of surgery, radiotherapy, and temozolomide chemotherapy, but this regimen fails to achieve long-term tumor control. ...Resistance to temozolomide is largely mediated by expression of the DNA repair enzyme MGMT; however, emerging evidence suggests that inactivation of MSH6 and other mismatch repair proteins plays an important role in temozolomide resistance. Here, we investigate endogenous MSH6 mutations in GBM, anaplastic oligodendroglial tumor tissue, and corresponding brain tumor-initiating cell lines (BTIC).
MSH6 sequence and MGMT promoter methylation were determined in human tumor samples and BTICs. Sensitivity to temozolomide was evaluated in vitro using BTICs in the absence and presence of O(6)-benzylguanine to deplete MGMT. The influence of MGMT and MSH6 status on in vivo sensitivity to temozolomide was evaluated using intracranial BTIC xenografts.
We identified 11 previously unreported mutations in MSH6 in nine different glioma samples and six paired BTIC lines from adult patients. In addition, MSH6 mutations were documented in three oligodendrogliomas and two treatment-naïve gliomas, both previously unreported findings. These mutations were found to influence the sensitivity of BTICs to temozolomide both in vitro and in vivo, independent of MGMT promoter methylation status.
These data demonstrate that endogenous MSH6 mutations may be present before alkylator therapy and occur in at least two histologic subtypes of adult glial neoplasms, with this report serving as the first to note these mutations in oligodendroglioma. These findings broaden our understanding of the clinical response to temozolomide in gliomas.
Primary glial tumors of the central nervous system, most commonly glioblastoma multiforme (GBM), are aggressive lesions with a dismal prognosis. Despite identification and isolation of human brain ...tumor stem cells (BTSCs), characteristics that distinguish BTSCs from neural stem cells remain to be elucidated. We cultured cells isolated from gliomas, using the neurosphere culture system, to understand their growth requirements. Both CD133+ and CD133− adult GBM BTSCs proliferated in the absence of exogenous mitogenic stimulation and gave rise to multipotent GBM spheres that were capable of self‐renewal. Epidermal growth factor (EGF) and fibroblast growth factor‐2 enhanced GBM BTSC survival, proliferation, and subsequent sphere size. Blockade of EGF receptor (EGFR) signaling reduced exogenous mitogen‐independent GBM sphere growth. Implantation of as few as 10 exogenous mitogen‐independent GBM BTSCs led to the formation of highly invasive intracranial tumors, which closely resembled human GBMs, in immunocompromised mice. These results demonstrate that exogenous mitogen independence, mediated in part through EGFR signaling, is one characteristic that distinguishes CD133+ and CD133− GBM BTSCs from neural stem cells. This novel experimental system will permit the elucidation of additional constitutively activated mechanisms that promote GBM BTSC survival, self‐renewal, and proliferation. STEM CELLS 2009;27:1722–1733
The invasive nature of cancers in general, and malignant gliomas in particular, is a major clinical problem rendering tumors incurable by conventional therapies. Using a novel invasive glioma mouse ...model established by serial in vivo selection, we identified the p75 neurotrophin receptor (p75(NTR)) as a critical regulator of glioma invasion. Through a series of functional, biochemical, and clinical studies, we found that p75(NTR) dramatically enhanced migration and invasion of genetically distinct glioma and frequently exhibited robust expression in highly invasive glioblastoma patient specimens. Moreover, we found that p75(NTR)-mediated invasion was neurotrophin dependent, resulting in the activation of downstream pathways and producing striking cytoskeletal changes of the invading cells. These results provide the first evidence for p75(NTR) as a major contributor to the highly invasive nature of malignant gliomas and identify a novel therapeutic target.
Purpose: The oncolytic effects of a systemically delivered, replicating, double-deleted vaccinia virus has been previously shown for
the treatment of many cancers, including colon, ovarian, and ...others. The purpose of this study was to investigate the oncolytic
potential of double-deleted vaccinia virus alone or in combination with rapamycin or cyclophosphamide to treat malignant gliomas
in vitro and in vivo .
Experimental Design: Rat (RG2, F98, C6) and human (A172, U87MG, U118) glioma cell lines were cultured in vitro and treated with live or UV-inactivated vaccinia virus. Viral gene enhanced green fluorescent protein (EGFP) expression
by fluorescence-activated cell sorting, relative cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
(MTT), and assays for cytopathic effects were examined. S.c. murine tumor xenografts (U87MG, U118, C6) and i.c. (RG2, F98)
tumor models in immunocompetent rats were treated with systemic administration of EGFP-expressing vaccinia virus (vvDD-EGFP),
alone or in combination with rapamycin or cyclophosphamide, or controls. Tumor size, viral biodistribution, and animal survival
were assessed. Lastly, the oncolytic effects of vvDD-EGFP on human malignant glioma explants were evaluated.
Results: vvDD-EGFP was able to infect and kill glioma cells in vitro . A single systemic dose of vvDD-EGFP significantly inhibited the growth of xenografts in athymic mice. Systemic delivery
of vvDD-EGFP alone was able to target solitary and multifocal i.c. tumors and prolong survival of immunocompetent rats, whereas
combination therapy with rapamycin or cyclophosphamide enhanced viral replication and further prolonged survival. Finally,
vvDD-EGFP was able to infect and kill ex vivo primary human malignant gliomas.
Conclusions: These results suggest that vvDD-EGFP is a promising novel agent for human malignant glioma therapy, and in combination with
immunosuppressive agents, may lead to prolonged survival from this disease.
ObjectiveDipeptidase-1 (DPEP-1) is a recently discovered leucocyte adhesion receptor for neutrophils and monocytes in the lungs and kidneys and serves as a potential therapeutic target to attenuate ...inflammation in moderate-to-severe COVID-19. We aimed to evaluate the safety and efficacy of the DPEP-1 inhibitor, LSALT peptide, to prevent specific organ dysfunction in patients hospitalised with COVID-19.DesignPhase 2a randomised, placebo-controlled, double-blinded, trial.SettingHospitals in Canada, Turkey and the USA.ParticipantsA total of 61 subjects with moderate-to-severe COVID-19.InterventionsRandomisation to LSALT peptide 5 mg intravenously daily or placebo for up to 14 days.Primary and secondary outcome measuresThe primary endpoint was the proportion of subjects alive and free of respiratory failure and/or the need for renal replacement therapy (RRT). Numerous secondary and exploratory endpoints were assessed including ventilation-free days, and changes in kidney function or serum biomarkers.ResultsAt 28 days, 27 (90.3%) and 28 (93.3%) of subjects in the placebo and LSALT groups were free of respiratory failure and the need for RRT (p=0.86). On days 14 and 28, the number of patients still requiring more intensive respiratory support (O2 ≥6 L/minute, non-invasive or invasive mechanical ventilation or extracorporeal membrane oxygenation) was 6 (19.4%) and 3 (9.7%) in the placebo group versus 2 (6.7%) and 2 (6.7%) in the LSALT group, respectively (p=0.14; p=0.67). Unadjusted analysis of ventilation-free days demonstrated 22.8 days for the LSALT group compared with 20.9 in the placebo group (p=0.4). LSALT-treated subjects had a significant reduction in the fold expression from baseline to end of treatment of serum CXCL10 compared with placebo (p=0.02). Treatment-emergent adverse events were similar between groups.ConclusionIn a Phase 2 study, LSALT peptide was demonstrated to be safe and tolerated in patients hospitalised with moderate-to-severe COVID-19.Trial registration numberNCT04402957.
Despite extensive molecular characterization, human glioblastoma remains a fatal disease with survival rates measured in months. Little improvement is seen with standard surgery, radiotherapy and ...chemotherapy. Clinical progress is hampered by the inability to detect and target glioblastoma disease reservoirs based on a diffuse invasive pattern and the presence of molecular and phenotypic heterogeneity. The goal of this study was to target the invasive and stem-like glioblastoma cells that evade first-line treatments using agents capable of delivering imaging enhancers or biotherapeutic cargo. To accomplish this, a combinatorial phage display library was biopanned against glioblastoma cell model systems that accurately recapitulate the intra- and inter-tumor heterogeneity and infiltrative nature of the disease. Candidate peptides were screened for specificity and ability to target glioblastoma cells in vivo. Cargo-conjugated peptides delivered contrast-enhancing agents to highly infiltrative tumor populations in intracranial xenograft models without the obvious need for blood brain barrier disruption. Simultaneous use of five independent targeting peptides provided greater coverage of this complex tumor and selected peptides have the capacity to deliver a therapeutic cargo (oncolytic virus VSVΔM51) to the tumor cells in vivo. Herein, we have identified a series of peptides with utility as an innovative platform to assist in targeting glioblastoma for the purpose of diagnostic or prognostic imaging, image-guided surgery, and/or improved delivery of therapeutic agents to glioblastoma cells implicated in disease relapse.
Glioblastoma multiforme (GBM) is among the deadliest cancers, owing in part to complex inter- and intra-tumor heterogeneity and the presence of a population of stem-like cells called brain tumour ...stem cells (BTSCs/BTICs). These cancer stem cells survive treatment and confer resistance to the current therapies - namely, radiation and the chemotherapeutic, temozolomide (TMZ). TMZ induces cell death by alkylating DNA, and BTSCs resist this mechanism via a robust DNA damage response. Hence, recent studies aimed to sensitize BTSCs to TMZ using combination therapy, such as inhibition of DNA repair machinery. We have previously demonstrated in established GBM cell lines that eukaryotic initiation factor 5B (eIF5B) promotes the translation of pro-survival and anti-apoptotic proteins. Consequently, silencing eIF5B sensitizes these cells to TRAIL-induced apoptosis. However, established cell lines do not always recapitulate the features of human glioma. Therefore, we investigated this mechanism in patient-derived BTSCs. We show that silencing eIF5B leads to increased TMZ sensitivity in two BTSC lines: BT25 and BT48. Depletion of eIF5B decreases the levels of anti-apoptotic proteins in BT48 and sensitizes these cells to TMZ-induced activation of caspase-3, cleavage of PARP, and apoptosis. We suggest that eIF5B represents a rational target to sensitize GBM tumors to the current standard-of-care.
IL-33, a member of the IL-1 cytokine family has been shown to play a dual role within the body. First IL-33, similar to other IL-1 family members, is a secreted cytokine that binds to the cell ...surface receptor ST2 to induce a number of cell signaling pathways. Second, IL-33 enters the nucleus where it binds chromatin and directs transcriptional control of an array of growth factors and cytokines. Consistent with its complex cellular regulation, IL-33 mediates an array of biological functions by acting on a wide range of innate and adaptive immune cells. Recently, we found that IL-33 is expressed in a large number of human glioma patient specimens where its expression within the tumor correlates with the increased presence of Iba+ cells that include both resident microglia and recruited monocyte and macrophages. Strikingly, glioma derived expression of IL-33 correlates with a dramatic decrease in overall survival of tumor-bearing animals and thus supports its role as an influential factor in gliomagenesis. Notably however, when the nuclear localization function of IL-33 is crippled, the tumor microenvironment is programmed to be anti-tumorigenic and results in prolonged overall survival suggesting that when educated appropriately this could represent a novel therapeutic strategy for glioma (De Boeck
(2020), Nat Commun, doi: 10.1038/s41467-020-18569-4).
Small molecules offer powerful ways to alter protein function. However, most proteins in the human proteome lack small-molecule probes, including the large class of non-catalytic transmembrane ...receptors, such as death receptors. We hypothesized that small molecules targeting the interfaces between transmembrane domains (TMDs) in receptor complexes may induce conformational changes that alter receptor function. Applying this concept in a screening assay, we identified a compound targeting the TMD of death receptor p75NTR that induced profound conformational changes and receptor activity. The compound triggered apoptotic cell death dependent on p75NTR and JNK activity in neurons and melanoma cells, and inhibited tumor growth in a melanoma mouse model. Due to their small size and crucial role in receptor activation, TMDs represent attractive targets for small-molecule manipulation of receptor function.
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•We identified a compound targeting the transmembrane domain of death receptor p75NTR•NSC49652 induced profound conformational changes and receptor activity•NSC49652 induced melanoma cell death, and inhibited melanoma tumor growth in vivo•TMDs represent attractive targets for small-molecule manipulation of receptor function
Small molecules offer powerful ways to alter protein function. However, most proteins in the human proteome lack small-molecule probes. Goh et al. Identified a small molecule that interacts with the transmembrane domain of death receptor p75NTR, which induces melanoma cell death, and inhibits melanoma tumor growth in vivo.
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