MET gain in diffuse astrocytomas is associated with poorer outcome

Neuropharmacological effects of calycosin: a translational review of molecular mechanisms and therapeutic applications

Calycosin, a naturally occurring isoflavonoid found predominantly in Astragalus membranaceus, exhibits significant therapeutic potential in various neurological conditions. Its multifaceted bioactive properties-antioxidant, anti-inflammatory, and anti-apoptotic-position it as a promising candidate for neuroprotection and neuroregeneration. This review explores calycosin's mechanisms of action, including its modulation of key signaling pathways such as HMGB1/TLR4/NF-κB (high mobility group box 1/toll-like receptor 4/nuclear factor kappa B), phosphatidylinositol-3-kinase (PI3 K)/Akt, ERK1/2 (extracellular signal-regulated kinase 1/2), and Hsp90/Akt/p38. In cerebral ischemia/reperfusion injury, calycosin reduces oxidative stress markers like ROS (reactive oxygen species) and MDA (malondialdehyde), enhances antioxidant enzymes (SOD (superoxide dismutase) and GPX (glutathione peroxidase)), and downregulates pro-inflammatory cytokines (TNF-α, IL-1β) through the HMGB1/TLR4/NF-κB pathway. It also inhibits autophagy via the STAT3/FOXO3a pathway and apoptosis by modulating Bax and Bcl-2 expression. In neuro-oncology, calycosin inhibits glioblastoma cell migration and invasion by modulating the TGF-β-mediated mesenchymal properties and suppressing the c-Met and CXCL10 signaling pathways. Additionally, it enhances the efficacy of temozolomide in glioma treatment through apoptotic pathways involving caspase-3 and caspase-9. Calycosin shows promise in Alzheimer's disease by reducing β-amyloid production and tau hyperphosphorylation via the GSK-3β pathway and improving mitochondrial function through the peroxisome proliferator-activated receptor gamma coactivator 1-Alpha (PGC-1α)/mitochondrial transcription factor A (TFAM) signaling pathway. In Parkinson's disease, calycosin mitigates oxidative stress, prevents dopaminergic neuronal death, and reduces neuroinflammation by inhibiting the TLR/NF-κB and MAPK pathways. It has also shown therapeutic potential in meningitis and even neuroprotective effects against hyperbilirubinemia-induced nerve injury. Despite these promising findings, further research, including detailed mechanistic studies and clinical trials, is needed to fully understand calycosin's therapeutic mechanisms and validate its potential in human subjects. Developing advanced delivery systems and exploring synergistic therapeutic strategies could further enhance its clinical application and effectiveness.

Prolonged complete response to adjuvant tepotinib in a patient with newly diagnosed disseminated glioblastoma harboring mesenchymal-epithelial transition fusion

The prognosis of patients with glioblastoma (GBM) remains poor despite current treatments. Targeted therapy in GBM has been the subject of intense investigation but has not been successful in clinical trials. The reasons for the failure of targeted therapy in GBM are multifold and include a lack of patient selection in trials, the failure to identify driver mutations, and poor blood-brain barrier penetration of investigational drugs. Here, we describe a case of a durable complete response in a newly diagnosed patient with GBM with leptomeningeal dissemination and PTPRZ1-MET fusion who was treated with tepotinib, a brain-penetrant MET inhibitor. This case of successful targeted therapy in a patient with GBM demonstrates that early molecular testing, identification of driver molecular alterations, and treatment with brain-penetrant small molecule inhibitors have the potential to change the outcome in select patients with GBM.

Progress in Glioma Stem Cell Research

Glioblastoma multiforme (GBM) represents a diverse spectrum of primary tumors notorious for their resistance to established therapeutic modalities. Despite aggressive interventions like surgery, radiation, and chemotherapy, these tumors, due to factors such as the blood-brain barrier, tumor heterogeneity, glioma stem cells (GSCs), drug efflux pumps, and DNA damage repair mechanisms, persist beyond complete isolation, resulting in dismal outcomes for glioma patients. Presently, the standard initial approach comprises surgical excision followed by concurrent chemotherapy, where temozolomide (TMZ) serves as the foremost option in managing GBM patients. Subsequent adjuvant chemotherapy follows this regimen. Emerging therapeutic approaches encompass immunotherapy, including checkpoint inhibitors, and targeted treatments, such as bevacizumab, aiming to exploit vulnerabilities within GBM cells. Nevertheless, there exists a pressing imperative to devise innovative strategies for both diagnosing and treating GBM. This review emphasizes the current knowledge of GSC biology, molecular mechanisms, and associations with various signals and/or pathways, such as the epidermal growth factor receptor, PI3K/AKT/mTOR, HGFR/c-MET, NF-κB, Wnt, Notch, and STAT3 pathways. Metabolic reprogramming in GSCs has also been reported with the prominent activation of the glycolytic pathway, comprising aldehyde dehydrogenase family genes. We also discuss potential therapeutic approaches to GSC targets and currently used inhibitors, as well as their mode of action on GSC targets.

Translation of circHGF RNA encodes an HGF protein variant promoting glioblastoma growth through stimulation of c-MET

INTRODUCTION

HGF/c-MET signaling is a significant driver of glioblastoma (GBM) growth and disease progression. Unfortunately, c-MET targeted therapies have been found to be largely ineffective suggesting additional redundant mechanisms of c-MET activation.

METHODS

Utilizing RNA-sequencing (RNA-seq) and ribosome profiling analyses of circular RNAs, circ-HGF (hsa_circ_0080914) was identified as markedly upregulated in primary GBM and found to potentially encode an HGF protein variant (C-HGF) 119 amino acids in length. This candidate HGF variant was characterized and evaluated for its ability to mediate c-MET activation and regulate PDX GBM cell growth, motility and invasive potential in vitro and tumor burden in intracranial xenografts in mice.

RESULTS

An internal ribosome entry site (IRES) was identified within the circ-HGF RNA which mediated translation of the cross-junctional ORF encoding C-HGF and was observed to be highly expressed in GBM relative to normal brain tissue. C-HGF was also found to be secreted from GBM cells and concentrated cell culture supernatants or recombinant C-HGF activated known signaling cascades downstream of c-MET. C-HGF was shown to interact directly with the c-MET receptor resulting in its autophosphorylation and activation in PDX GBM lines. Knockdown of C-HGF resulted in suppression of c-MET signaling and marked inhibition of cell growth, motility and invasiveness, whereas overexpression of C-HGF displayed the opposite effects. Additionally, modulation of C-HGF expression regulated tumor growth in intracranial xenografted PDX GBM models.

CONCLUSIONS

These results reveal an alternative mechanism of c-MET activation via a circular RNA encoded HGF protein variant which is relevant in GBM biology. Targeting C-HGF may offer a promising approach for GBM clinical management.

Spotlights on adult patients with pediatric-type diffuse gliomas in accordance with the 2021 WHO classification of CNS tumors

Introduction

The fifth edition of the World Health Organization (WHO) classification of central nervous system (CNS) tumors released in 2021 formally defines pediatric-type diffuse gliomas. However, there is still little understanding of pediatric-type diffuse gliomas, and even less attention has been paid to adult patients. Therefore, this study describes the clinical radiological, survival, and molecular features of adult patients with pediatric-type glioma.

Methods

Adult patients who underwent surgery from January 2011 to January 2022, classified as pediatric-type glioma, were included in this study. Clinical, radiological, histopathological, molecular pathological, and survival data were collected for analysis.

Results

Among 596 adult patients, 20 patients with pediatric-type glioma were screened, including 6 with diffuse astrocytoma, MYB- or MYBL1-altered, 2 with diffuse midline glioma, H3 K27-altered, and 12 with diffuse pediatric-type high-grade glioma, H3-wildtype and IDH-wildtype. Pediatric high-grade glioma (pHGG) frequently showed tumor enhancement, peritumoral edema, and intratumoral necrosis. Adult patients with pHGG showed a longer life expectancy than adult patients with glioblastoma. Common molecular alterations included chromosome alterations and CDKN2A/B, PIK3CA, and PTEN, while altered KMT5B and MET were found to affect the overall survival.

Conclusion

Our study demonstrated adult patients with pediatric-type glioma. Notably, our research aims to expand the current understanding of adult patients with pediatric-type diffuse gliomas. Furthermore, personalized therapies consisting of targeted molecular inhibitors for MET and VEGFA may exhibit beneficial effects in the corresponding population.

Melanoma and Glioblastoma-Not a Serendipitous Association

Recently, we came across a patient with malignant melanoma and primary glioblastoma. Given this, we parsed the literature to ascertain the relationship, if any, between these 2 malignancies. We begin with a brief overview of melanoma and glioma in isolation followed by a chronologic overview of case reports and epidemiologic studies documenting both neoplasms. This is followed by studies detailing genetic abnormalities common to both malignancies with a view to identifying unifying genetic targets for therapeutic strategies as well as to explore the possibility of a putative association and an inherited cancer susceptibility trait. From a scientific perspective, we believe we have provided evidence favoring an association between melanoma and glioma. Future studies that include documentation of additional cases, as well as a detailed molecular analyses, will lend credence to our hypothesis that the co-occurrence of these 2 conditions is likely not serendipitous.

Signaling pathways in brain tumors and therapeutic interventions

Brain tumors, although rare, contribute to distinct mortality and morbidity at all ages. Although there are few therapeutic options for brain tumors, enhanced biological understanding and unexampled innovations in targeted therapies and immunotherapies have considerably improved patients' prognoses. Nonetheless, the reduced response rates and unavoidable drug resistance of currently available treatment approaches have become a barrier to further improvement in brain tumor (glioma, meningioma, CNS germ cell tumors, and CNS lymphoma) treatment. Previous literature data revealed that several different signaling pathways are dysregulated in brain tumor. Importantly, a better understanding of targeting signaling pathways that influences malignant behavior of brain tumor cells might open the way for the development of novel targeted therapies. Thus, there is an urgent need for a more comprehensive understanding of the pathogenesis of these brain tumors, which might result in greater progress in therapeutic approaches. This paper began with a brief description of the epidemiology, incidence, risk factors, as well as survival of brain tumors. Next, the major signaling pathways underlying these brain tumors' pathogenesis and current progress in therapies, including clinical trials, targeted therapies, immunotherapies, and system therapies, have been systemically reviewed and discussed. Finally, future perspective and challenges of development of novel therapeutic strategies in brain tumor were emphasized.

Molecular markers related to patient outcome in patients with IDH-mutant astrocytomas grade 2 to 4: A systematic review

BACKGROUND

Grading and classification of IDH-mutant astrocytomas has shifted from solely histology towards histology combined with molecular diagnostics. In this systematic review, we give an overview of all currently known clinically relevant molecular markers within IDH-mutant astrocytomas grade 2 to 4.

METHODS

A literature search was performed in five electronic databases for English original papers on patient outcome with respect to a molecular marker as determined by DNA/RNA sequencing, micro-arrays, or DNA methylation profiling in IDH-mutant astrocytomas grade 2 to 4. Papers were included if molecular diagnostics were performed on tumour tissue of at least 15 IDH-mutant astrocytoma patients, and if the investigated molecular markers were not limited to the diagnostic markers MGMT, ATRX, TERT, and/or TP53.

RESULTS

The literature search identified 4508 unique articles, published between August 2012 and December 2021, of which ultimately 44 articles were included. Numerous molecular markers from these papers were significantly correlated to patient outcome. The associations between patient outcome and non-canonical IDH mutations, PI3K mutations, high expression of MSH2, high expression of RAD18, homozygous deletion of CDKN2A/B, amplification of PDGFRA, copy number neutral loss of chromosomal arm 17p, loss of chromosomal arm 19q, the G-CIMP-low DNA methylation cluster, high total CNV, and high tumour mutation burden were confirmed in multiple studies.

CONCLUSIONS

Multiple genetic and epigenetic markers are associated with survival in IDH-mutant astrocytoma patients. Commonly affected are the RB signalling pathway, the RTK-PI3K-mTOR signalling pathway, genomic stability markers, and (epigenetic) gene regulation.

Aptamer-Modified Erythrocyte Membrane-Coated pH-Sensitive Nanoparticles for c-Met-Targeted Therapy of Glioblastoma Multiforme

Biomimetic drug delivery systems, especially red blood cell (RBC) membrane-based nanoparticle drug delivery systems (RNP), have been extensively utilized in tumor drug delivery because of their excellent biocompatibility and prolonged circulation. In this study, we developed an active targeting pH-sensitive RNP loaded with DOX by decorating an aptamer SL1 on RBC membranes (SL1-RNP-DOX) for c-Met-targeted therapy of glioblastoma multiforme (GBM). SL1 could specifically bind to c-Met, which is highly expressed in GBM U87MG cells and facilitate DOX delivery to GBM cells. In vitro studies demonstrated that U87MG cells had a higher uptake of SL1-RNP-DOX (3.25 folds) and a stronger pro-apoptosis effect than unmodified RNP-DOX. In vivo fluorescence imaging and tissue distribution further demonstrated the higher tumor distribution of SL1-RNP-DOX (2.17 folds) compared with RNP-DOX. As a result, SL1-RNP-DOX presented the best anti-GBM effect with a prolonged median survival time (23 days vs. 15.5 days) and the strongest tumor cell apoptosis in vivo among all groups. In conclusion, SL1-RNP-DOX exhibited a promising targeting delivery strategy for GBM therapy.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Molecular and Circulating Biomarkers in Patients with Glioblastoma

Glioblastoma is the most aggressive malignant tumor of the central nervous system with a low survival rate. The difficulty of obtaining this tumor material represents a major limitation, making the real-time monitoring of tumor progression difficult, especially in the events of recurrence or resistance to treatment. The identification of characteristic biomarkers is indispensable for an accurate diagnosis, the rigorous follow-up of patients, and the development of new personalized treatments. Liquid biopsy, as a minimally invasive procedure, holds promise in this regard. The purpose of this paper is to summarize the current literature regarding the identification of molecular and circulating glioblastoma biomarkers and the importance of their integration as a valuable tool to improve patient care.

The hepatocyte growth factor/mesenchymal epithelial transition factor axis in high-risk pediatric solid tumors and the anti-tumor activity of targeted therapeutic agents

Clinical trials completed in the last two decades have contributed significantly to the improved overall survival of children with cancer. In spite of these advancements, disease relapse still remains a significant cause of death in this patient population. Often, increasing the intensity of current protocols is not feasible because of cumulative toxicity and development of drug resistance. Therefore, the identification and clinical validation of novel targets in high-risk and refractory childhood malignancies are essential to develop effective new generation treatment protocols. A number of recent studies have shown that the hepatocyte growth factor (HGF) and its receptor Mesenchymal epithelial transition factor (c-MET) influence the growth, survival, angiogenesis, and metastasis of cancer cells. Therefore, the c-MET receptor tyrosine kinase and HGF have been identified as potential targets for cancer therapeutics and recent years have seen a race to synthesize molecules to block their expression and function. In this review we aim to summarize the literature that explores the potential and biological rationale for targeting the HGF/c-MET pathway in common and high-risk pediatric solid tumors. We also discuss selected recent and ongoing clinical trials with these agents in relapsed pediatric tumors that may provide applicable future treatments for these patients.

Identification of CRYAB+ KCNN3+ SOX9+ Astrocyte-Like and EGFR+ PDGFRA+ OLIG1+ Oligodendrocyte-Like Tumoral Cells in Diffuse IDH1-Mutant Gliomas and Implication of NOTCH1 Signalling in Their Genesis

Simple Summary

Diffuse grade II IDH-mutant gliomas are rare brain tumors mainly affecting young patients. These tumors are composed of different populations of tumoral cells. Little is known of these cells and how they are generated. These different cells may show different sensitivity to treatments, so our aim was to study them in detail by directly using patient resections. We identified two clearly distinct tumoral populations and defined reliable markers for them. We also uncovered part of the molecular mechanisms that generate them. Finally, we found that the two cell types have different electrical activity. This article provides unique data and new issues on these rare tumors, which need to be further investigated to develop innovative treatments.

Abstract

Diffuse grade II IDH-mutant gliomas are slow-growing brain tumors that progress into high-grade gliomas. They present intratumoral cell heterogeneity, and no reliable markers are available to distinguish the different cell subtypes. The molecular mechanisms underlying the formation of this cell diversity is also ill-defined. Here, we report that SOX9 and OLIG1 transcription factors, which specifically label astrocytes and oligodendrocytes in the normal brain, revealed the presence of two largely nonoverlapping tumoral populations in IDH1-mutant oligodendrogliomas and astrocytomas. Astrocyte-like SOX9⁺ cells additionally stained for APOE, CRYAB, ID4, KCNN3, while oligodendrocyte-like OLIG1⁺ cells stained for ASCL1, EGFR, IDH1, PDGFRA, PTPRZ1, SOX4, and SOX8. GPR17, an oligodendrocytic marker, was expressed by both cells. These two subpopulations appear to have distinct BMP, NOTCH1, and MAPK active pathways as stainings for BMP4, HEY1, HEY2, p-SMAD1/5 and p-ERK were higher in SOX9⁺ cells. We used primary cultures and a new cell line to explore the influence of NOTCH1 activation and BMP treatment on the IDH1-mutant glioma cell phenotype. This revealed that NOTCH1 globally reduced oligodendrocytic markers and IDH1 expression while upregulating APOE, CRYAB, HEY1/2, and an electrophysiologically-active Ca²⁺-activated apamin-sensitive K⁺ channel (KCNN3/SK3). This was accompanied by a reduction in proliferation. Similar effects of NOTCH1 activation were observed in nontumoral human oligodendrocytic cells, which additionally induced strong SOX9 expression. BMP treatment reduced OLIG1/2 expression and strongly upregulated CRYAB and NOGGIN, a negative regulator of BMP. The presence of astrocyte-like SOX9⁺ and oligodendrocyte-like OLIG1⁺ cells in grade II IDH1-mutant gliomas raises new questions about their role in the pathology.

HGF/MET Signaling in Malignant Brain Tumors

Hepatocyte growth factor (HGF) ligand and its receptor tyrosine kinase (RTK) mesenchymal-epithelial transition factor (MET) are important regulators of cellular processes such as proliferation, motility, angiogenesis, and tissue regeneration. In healthy adult somatic cells, this ligand and receptor pair is expressed at low levels and has little activity except when tissue injuries arise. In cancer cells, HGF/MET are often overexpressed, and this overexpression is found to correlate with tumorigenesis, metastasis, and poorer overall prognosis. This review focuses on the signaling of these molecules in the context of malignant brain tumors. RTK signaling pathways are among the most common and universally dysregulated pathways in gliomas. We focus on the role of HGF/MET in the following primary malignant brain tumors: astrocytomas, glioblastomas, oligodendrogliomas, ependymomas, and embryonal central nervous system tumors (including medulloblastomas and others). Brain metastasis, as well as current advances in targeted therapies, are also discussed.

Personalized and translational approach for malignant brain tumors in the era of precision medicine: the strategic contribution of an experienced neurosurgery laboratory in a modern neurosurgery and neuro-oncology department

Personalized medicine (PM) aims to optimize patient management, taking into account the individual traits of each patient. The main purpose of PM is to obtain the best response, improving health care and lowering costs. Extending traditional approaches, PM introduces novel patient-specific paradigms from diagnosis to treatment, with greater precision. In neuro-oncology, the concept of PM is well established. Indeed, every neurosurgical intervention for brain tumors has always been highly personalized. In recent years, PM has been introduced in neuro-oncology also to design and prescribe specific therapies for the patient and the patient's tumor. The huge advances in basic and translational research in the fields of genetics, molecular and cellular biology, transcriptomics, proteomics, and metabolomics have led to the introduction of PM into clinical practice. The identification of a patient's individual variation map may allow to design selected therapeutic protocols that ensure successful outcomes and minimize harmful side effects. Thus, clinicians can switch from the "one-size-fits-all" approach to PM, ensuring better patient care and high safety margin. Here, we review emerging trends and the current literature about the development of PM in neuro-oncology, considering the positive impact of innovative advanced researches conducted by a neurosurgical laboratory.

Super-enhancers: A new frontier for glioma treatment

Glioma is the most common primary malignant tumor in the human brain. Although there are a variety of treatments, such as surgery, radiation and chemotherapy, glioma is still an incurable disease. Super-enhancers (SEs) are implicated in the control of tumor cell identity, and they promote oncogenic transcription, which supports tumor cells. Inhibition of the SE complex, which is required for the assembly and maintenance of SEs, may repress oncogenic transcription and impede tumor growth. In this review, we discuss the unique characteristics of SEs compared to typical enhancers, and we summarize the recent advances in the understanding of their properties and biological role in gene regulation. Additionally, we highlight that SE-driven lncRNAs, miRNAs and genes are involved in the malignant phenotype of glioma. Most importantly, the application of SE inhibitors in different cancer subtypes has introduced new directions in glioma treatment.

MET in glioma: signaling pathways and targeted therapies

Gliomas represent the most common type of malignant brain tumor, among which, glioblastoma remains a clinical challenge with limited treatment options and dismal prognosis. It has been shown that the dysregulated receptor tyrosine kinase (RTK, including EGFR, MET, PDGFRα, ect.) signaling pathways have pivotal roles in the progression of gliomas, especially glioblastoma. Increasing evidence suggests that expression levels of the RTK MET and its specific stimulatory factors are significantly increased in glioblastomas compared to those in normal brain tissues, whereas some negative regulators are found to be downregulated. Mutations in MET, as well as the dysregulation of other regulators of cross-talk with MET signaling pathways, have also been identified. MET and its ligand hepatocyte growth factor (HGF) play a critical role in the proliferation, survival, migration, invasion, angiogenesis, stem cell characteristics, and therapeutic resistance and recurrence of glioblastomas. Therefore, combined targeted therapy for this pathway and associated molecules could be a novel and attractive strategy for the treatment of human glioblastoma. In this review, we highlight progress made in the understanding of MET signaling in glioma and advances in therapies targeting HGF/MET molecules for glioma patients in recent years, in addition to studies on the expression and mutation status of MET.

The Prognostic and Therapeutic Potential of LRIG3 and Soluble LRIG3 in Glioblastoma

Glioblastoma is a highly lethal type of primary brain tumor that exhibits unrestricted growth and aggressive invasion capabilities, leading to a dismal prognosis despite a multitude of therapies. Multiple alterations in the expression level of genes and/or proteins have been identified in glioblastomas, including the activation of oncogenes and/or silencing of tumor-suppressor genes. Nevertheless, there are still no effective targeted therapies associated with these changes. In this study, we investigated the expression of human leucine-rich repeats and immunoglobulin-like domains protein 3 (LRIG3) in human glioma specimens through immunohistochemical analysis. The results showed that LRIG3 was weakly expressed in high-grade gliomas (WHO [World Health Organization] grades III and IV) compared with that in low-grade gliomas (WHO grade II). Survival analysis of these patients with glioma indicated that LRIG3 is an important prognostic marker for better survival. Moreover, we confirmed the existence of soluble ectodomain of LRIG3 (sLRIG3) in the cell culture supernatant, serum, and in tumor cystic fluid of patients with glioma. Molecular mechanistic investigation demonstrated that both LRIG3 and sLRIG3 inhibit the growth and invasion capabilities of GL15, U87, and PriGBM cells and tumor xenografts in nude mice through regulating the MET/phosphatidylinositol 3-kinase/Akt signaling pathway. Enzyme-linked immunosorbent assay confirmed the positive correlation between serum sLRIG3 protein levels and overall survival time in patients with high-grade gliomas. Taken together, our data for the first time demonstrate the existence of sLRIG3 and that both LRIG3 and sLRIG3 are potent tumor suppressors, which could be used as prognostic markers for better overall survival and therapeutic agents for glioblastoma.

The landscape of postsurgical recurrence patterns in diffuse low-grade gliomas

Early and maximal safe surgical resection optionally followed by adjuvant treatment is currently recommended in diffuse low-grade glioma (DLGG). Although this management delays malignant transformation (MT), recurrence will most often occur. Because this relapse usually arises locally, reoperation can be considered, with possible further chemotherapy/radiotherapy. However, due to a prolonged overall survival, a large spectrum of unusual recurrence patterns begins to emerge during long-term follow-up, beyond the classical slow and local tumor re-growth. We review various atypical patterns of DLGG relapse, we discuss their pathophysiological mechanisms and how to adapt the treatment(s). Those patterns include very diffuse, ipsi- or bilateral gliomatosis-like progression, multicentric recurrence with emergence of remote low-grade or high-grade glioma, leptomeningeal dissemination, acute (early or delayed) local MT or bulky relapse into the operating cavity. This landscape of recurrence patterns may allow physicians to elaborate new tailored therapeutic strategies and scientists to develop original hypotheses for basic research.

c-Met Expression Is a Useful Marker for Prognosis Prediction in IDH-Mutant Lower-Grade Gliomas and IDH-Wildtype Glioblastomas

OBJECTIVE

c-Met has been shown to be associated with tumor growth in several human cancers. This study aims to evaluate the correlation between the c-Met expression and histopathologic/clinical characteristics.

METHODS

A total of 153 patients with histologically defined World Health Organization grade II-IV diffuse astrocytic and oligodendroglial tumors were analyzed.

RESULTS

For each histopathologic diagnosis, the number of cases and positive rate of c-Met expression are as follows: oligodendroglioma, IDH-mutant, and 1p19q codeletion (OD): 16 cases, 6.3%; anaplastic oligodendroglioma, IDH-mutant, and 1p19q codeletion (AO): 11 cases, 36.4%; diffuse astrocytoma (DA), IDH-mutant: 21 cases, 28.6%; anaplastic astrocytoma (AA), IDH- mutant: 15 cases, 20%; glioblastoma, IDH-mutant: 2, 100%, DA, IDH-wildtype: 9 cases, 33.3%; AA, IDH-wildtype: 20 cases, 30.0%; and glioblastoma, IDH-wildtype: 59 cases, 52.5%. c-Met expression was correlated with progression-free survival in oligodendroglial tumors and glioblastoma, IDH-wildtype. Furthermore, it was correlated with overall survival in AO, oligodendroglial tumors, DA, IDH-mutant, DA, IDH-wildtype, and glioblastoma, IDH-wildtype, and tend to be correlated with overall survival in IDH-mutant lower-grade astrocytic tumors.

CONCLUSIONS

c-Met expression was revealed to be a useful marker for prognosis prediction in IDH-mutant lower-grade gliomas and glioblastoma, IDH-wildtype, representing a new independent prognostic marker that can be easily measured.

Widely metastatic IDH1-mutant glioblastoma with oligodendroglial features and atypical molecular findings: a case report and review of current challenges in molecular diagnostics

Background

Gliomas with 1p/19q-codeletion as well as mutation of isocitrate dehydrogenase (IDH) 1 are typically characterized as oligodendrogliomas with comparatively good response to treatment with radiation and chemotherapy.

Case presentation

We present the case of a 28-year-old man with an IDH1 and TP53 mutant high grade glioma with abnormalities in chromosomes 1 and 19 suggestive of anaplastic oligodendroglioma that rapidly progressed to widespread metastatic disease. Biopsy of a liver lesion confirmed metastasis of the patient’s known brain primary and chemotherapy with temozolomide was initiated. The patient’s rapidly growing tumor burden with fulminant liver failure and tumor lysis led to multisystem failure of which the patient died. Further molecular testing illustrated features more consistent with glioblastoma: multiple large chromosomal aberrations including loss of whole chromosome 1 and 2q; gain/amplification of MYCN, MET, and CDK4; loss of CDKN2A/B; and an ATRX mutation.

Conclusion

This case illustrates the importance of higher level molecular diagnostic testing for patients with particularly aggressive disease progression that is not concordant with standard prognoses. Additional data on cases with atypical alterations of 1p and 19q are needed to better understand the distinct biology of these cancers so that appropriate therapies can be developed.

Electronic supplementary material

The online version of this article (10.1186/s13000-019-0793-5) contains supplementary material, which is available to authorized users.

MET alterations detected in blood-derived circulating tumor DNA correlate with bone metastases and poor prognosis

Background

We analyzed clinical associations of MET alterations in the plasma of patients with diverse malignancies.

Methods

Digital sequencing of circulating tumor DNA (ctDNA) (54–70 genes) was performed in 438 patients; 263 patients also had tissue sequencing (182–315 genes). The most represented tumor types were gastrointestinal (28.1%), brain (24.9%), and lung (23.2%). Most patients (71.2%) had recurrent/metastatic disease.

Results

MET alterations were observed in 31 patients (7.1%) and correlated with bone metastasis (P = 0.007), with TP53 (P = 0.001) and PTEN (P = 0.003) abnormalities, and with an increased number of alterations (median, 4 vs 1, P = 0.001) (all multivariable analyses). Patients with MET alterations demonstrated a significantly shorter median time to metastasis/recurrence (1.0 vs 10.4 months, P = 0.044, multivariable) and a poorer survival (30.6 vs 58.4 months, P = 0.013, univariate only). Of the 31 patients with MET alterations, 18 also had tissue testing; only two also had tissue MET alterations (11.1%); MET alterations were detected at a lower frequency in tissue (1.14%) compared to ctDNA (7.1%), with P = 0.0002.

Conclusions

In conclusion, the detection of MET alterations by liquid biopsy is feasible. MET ctDNA alterations were associated with a poorer prognosis, higher numbers of genomic abnormalities, and bone metastases. The correlation with bone metastases may explain the higher frequency of MET alterations in blood ctDNA than in tissue (since bones are rarely biopsied) and the previous observations of bone-predominant responses to MET inhibitors. The high number of co-altered genes suggests that MET inhibitors may need to be combined with other agents to induce/optimize responses.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0610-8) contains supplementary material, which is available to authorized users.

Selective MET Kinase Inhibition in MET-Dependent Glioma Models Alters Gene Expression and Induces Tumor Plasticity

The receptor tyrosine kinase (RTK) MET represents a promising tumor target in a subset of glioblastomas. Most RTK inhibitors available in the clinic today, including those inhibiting MET, affect multiple targets simultaneously. Previously, it was demonstrated that treatment with cabozantinib (MET/VEGFR2/RET inhibitor) prolonged survival of mice carrying orthotopic patient-derived xenografts (PDX) of the MET-addicted glioblastoma model E98, yet did not prevent development of recurrent and cabozantinib-resistant tumors. To exclude VEGFR2 inhibition-inflicted blood-brain barrier normalization and diminished tumor distribution of the drug, we have now investigated the effects of the novel MET-selective inhibitor Compound A in the orthotopic E98 xenograft model. In vitro, Compound A proved a highly potent inhibitor of proliferation of MET-addicted cell lines. In line with its target selectivity, Compound A did not restore the leaky blood-brain barrier and was more effective than cabozantinib in inhibiting MET phosphorylation in vivo Compound A treatment significantly prolonged survival of mice carrying E98 tumor xenografts, but did not prevent eventual progression. Contrasting in vitro results, the Compound A-treated xenografts displayed high levels of AKT phosphorylation despite the absence of phosphorylated MET. Profiling by RNA sequencing showed that in vivo transcriptomes differed significantly from those in control xenografts.Implications: Collectively, these findings demonstrate the plasticity of paracrine growth factor receptor signaling in vivo and urge for prudency with in vitro drug-testing strategies to validate monotherapies. Mol Cancer Res; 15(11); 1587-97. ©2017 AACR.

Silencing of PROS1 induces apoptosis and inhibits migration and invasion of glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is an aggressive brain tumor and most patients have poor prognosis. Despite many advances in research, there has been no significant improvement in the patient survival rate. New molecular therapies are being studied and RNA interference (RNAi) therapy is one of the promising approaches to improve prognosis and increase survival in patients with GBM. We performed a meta‑analysis of five different microarray datasets and identified 460 significantly upregulated genes in GBM. Loss‑of‑function screening of these upregulated genes using LN18 cells was performed to identify the significant target genes for glioma. Further investigations were performed using siRNA in LN18 cells and various functional assays were carried out on the selected candidate gene to understand further its role in GBM. We identified PROS1 as a candidate gene for GBM from the meta‑analysis and RNAi screening. Knockdown of PROS1 in LN18 cells significantly induced apoptosis compared to siPROS1‑untreated cells (p<0.05). Migration in cells treated with siPROS1 was reduced significantly (p<0.05) and this was confirmed with wound-healing assay. PROS1 knockdown showed substantial reduction in cell invasion up to 82% (p<0.01). In addition, inhibition of PROS1 leads to decrease in cellular proliferation by 18%. Knockdown of PROS1 in LN18 cells caused activation of both of the extrinsic and intrinsic apoptotic pathways. It caused major upregulation of FasL which is important for death receptor signaling activation and also downregulation of GAS6 and other members of TAM family of receptors. PROS1 may play an important role in the development of GBM through cellular proliferation, migration and invasion as well as apoptosis. Targeting PROS1 in GBM could be a novel therapeutic strategy in GBM treatment.

Mesenchymal/radioresistant traits in granular astrocytomas: evidence from a combined clinical and molecular approach

AIMS

Granular-cell astrocytomas (GCAs) are morphologically characterized by a prominent component of granular periodic acid-Schiff-positive cells, and show increased aggressiveness as compared with 'ordinary' astrocytomas. The aim of this study was to investigate, in a small series of three GCAs, the expression of mesenchymal/radioresistance-associated biomarkers [such as chitinase-3-like protein 1 (YKL-40), hepatocyte growth factor receptor (c-Met), and caveolin 1 (Cav1)] that could contribute to the poor outcome associated with this glioma subgroup.

METHODS AND RESULTS

Our results show that GCAs, according to the new molecular glioma classifications, consistently show a prognostically negative molecular trait (IDH1wt-ATRX noloss-1p/19q nocodeletion). Furthermore, GCAs significantly differed from a control series of 33 'conventional' astrocytomas, because of diffuse and strong immunohistochemical coexpression of YKL-40, c-Met, and Cav1.

CONCLUSIONS

Our findings show that specific morphological traits, such as a granular-cell component, could represent useful features in guiding the search for prognostic and predictive biomarkers that could eventually be therapy-targetable (e.g. Met inhibitors aimed at reducing radioresistance).

Novel MET/TIE2/VEGFR2 inhibitor altiratinib inhibits tumor growth and invasiveness in bevacizumab-resistant glioblastoma mouse models

BACKGROUND

Glioblastoma highly expresses the proto-oncogene MET in the setting of resistance to bevacizumab. MET engagement by hepatocyte growth factor (HGF) results in receptor dimerization and autophosphorylation mediating tumor growth, invasion, and metastasis. Evasive revascularization and the recruitment of TIE2-expressing macrophages (TEMs) are also triggered by anti-VEGF therapy.

METHODS

We investigated the activity of altiratinib (a novel balanced inhibitor of MET/TIE2/VEGFR2) against human glioblastoma stem cell lines in vitro and in vivo using xenograft mouse models. The biological activity of altiratinib was assessed in vitro by testing the expression of HGF-stimulated MET phosphorylation as well as cell viability after altiratinib treatment. Tumor volume, stem cell and mesenchymal marker levels, microvessel density, and TIE2-expressing monocyte infiltration were evaluated in vivo following treatment with a control, bevacizumab alone, bevacizumab combined with altiratinib, or altiratinib alone.

RESULTS

In vitro, HGF-stimulated MET phosphorylation was completely suppressed by altiratinib in GSC17 and GSC267, and altiratinib markedly inhibited cell viability in several glioblastoma stem cell lines. More importantly, in multiple xenograft mouse models, altiratinib combined with bevacizumab dramatically reduced tumor volume, invasiveness, mesenchymal marker expression, microvessel density, and TIE2-expressing monocyte infiltration compared with bevacizumab alone. Furthermore, in the GSC17 xenograft model, altiratinib combined with bevacizumab significantly prolonged survival compared with bevacizumab alone.

CONCLUSIONS

Together, these data suggest that altiratinib may suppress tumor growth, invasiveness, angiogenesis, and myeloid cell infiltration in glioblastoma. Thus, altiratinib administered alone or in combination with bevacizumab may overcome resistance to bevacizumab and prolong survival in patients with glioblastoma.

C-MET overexpression and amplification in gliomas

We investigated c-Met overexpression and MET gene amplification in gliomas to determine their incidence and prognostic significance. c-Met immunohistochemistry and MET gene fluorescence in situ hybridization were carried out on tissue microarrays from 250 patients with gliomas (137 grade IV GBMs and 113 grade II and III diffuse gliomas). Clinicopathological features of these cases were reviewed. c-Met overexpression and MET gene amplification were detected in 13.1% and 5.1% of the GBMs, respectively. All the MET-amplified cases showed c-Met overexpression, but MET amplification was not always concordant with c-Met overexpression. None of grade II and III gliomas demonstrated c-Met overexpression or MET gene amplification. Mean survival of the GBM patients with MET amplification was not significantly different from patients without MET amplification (P=0.155). However, GBM patients with c-Met overexpression survived longer than patients without c-Met overexpression (P=0.035). Although MET amplification was not related to poor GBM prognosis, it is partially associated with the aggressiveness of gliomas, as MET amplification was found only in grade IV, not in grade II and III gliomas. We suggest that MET inhibitor therapy may be beneficial in about 5% GBMs, which was the incidence of MET gene amplification found in the patients included in this study.

Patterns of response to crizotinib in recurrent glioblastoma according to ALK and MET molecular profile in two patients

Two patients with an unmethylated MGMT promoter and IDH1 (R132H) wild-type recurrent glioblastoma were treated with crizotinib. Prolonged stabilization of the disease (17 months) was achieved in the first case. Interestingly, anaplastic lymphoma kinase (ALK) expression and c-MET protein overexpression was observed. Conversely, no response to crizotinib was obtained in the second case with MET protein overexpression and c-MET amplification but no ALK expression or ALK gene amplification. These case studies suggest that novel targeted ALK inhibitors may provide relevant clinical benefit in selected cases in which driver mutations are demonstrable.

High levels of c-Met is associated with poor prognosis in glioblastoma

The tyrosine kinase receptor c-Met has been suggested to be involved in crucial parts of glioma biology like tumor stemness, growth and invasion. The aim of this study was to investigate the prognostic value of c-Met in a population-based glioma patient cohort. Tissue samples from 238 patients with WHO grade I, II, III and IV tumors were analyzed using immunohistochemical staining and advanced image analysis. Strong c-Met expression was found in tumor cells, blood vessels, and peri-necrotic areas. At the subcellular level, c-Met was identified in the cytoplasm and in the cell membrane. Measurements of high c-Met intensity correlated with high WHO grade (p = 0.006) but no association with survival was observed in patients with WHO grade II (p = 0.09) or III (p = 0.17) tumors. High expression of c-Met was associated with shorter overall survival in patients with glioblastoma multiforme (p = 0.03). However the prognostic effect of c-Met in glioblastomas was time-dependent and only observed in patients who survived more than 8.5 months, and not within the first 8.5 months after diagnosis. This was significant in multivariate analysis (HR 1.99, 95 % CI 1.29-3.08, p = 0.002) adjusted for treatment and the clinical variables age (HR 1.01, 95 % CI 0.99-1.03, p = 0.30), performance status (HR 1.34, 95 % CI 1.17-1.53, p < 0.001), and tumor crossing midline (HR 1.28, 95 % CI 0.79-2.07, p = 0.29). In conclusion, this study showed that high levels of c-Met holds unfavorable prognostic value in glioblastomas.

PDGFRA gain in low-grade diffuse gliomas

Glioblastomas with a proneural expression signature are characterized by frequent IDH1 mutations (i.e. genetic hallmarks of secondary glioblastomas) and PDGFRA (platelet-derived growth factor receptor-α) amplification. Mutations in IDH1/2 are frequent and early genetic events in diffuse astrocytomas (World Health Organization grade II), precursor to secondary glioblastomas, but little is known about the role and timing of PDGFRA amplification in these tumors. We assessed PDGFRA gain in 342 low-grade diffuse gliomas by quantitative polymerase chain reaction. Gain in PDGFRA was detected in 27 (16.3%) of 166 diffuse astrocytomas, significantly more frequent than in oligodendrogliomas (3 [2.6%] of 115, p < 0.0001). Analyses using previously published data from our laboratory showed an inverse correlation between PDGFRA gain and IDH1/2 mutations (p = 0.018) or 1p/19q loss (p < 0.0001). The vast majority of diffuse astrocytomas showed IDH1/2 mutations and/or PDGFRA gain (154 [93%] of 166). Mean survival of diffuse astrocytoma patients with PDGFRA gain was 8.8 ± 1.6 years, similar to that with IDH1/2 mutations (7.8 ± 0.5 years) or TP53 mutations (7.6 ± 0.6 years) but significantly longer than those with MET gain (4.4 ± 0.7 years). Dual-color fluorescence in situ hybridization in 6 diffuse astrocytomas with PDGFRA/MET co-gain identified by quantitative polymerase chain reaction revealed that PDGFRA and MET were typically amplified in different tumor cell populations. Tumor cells with coamplification were also focally observed, suggesting intratumoral heterogeneity, even in diffuse astrocytomas.

The definition of primary and secondary glioblastoma

Glioblastoma is the most frequent and malignant brain tumor. The vast majority of glioblastomas (~90%) develop rapidly de novo in elderly patients, without clinical or histologic evidence of a less malignant precursor lesion (primary glioblastomas). Secondary glioblastomas progress from low-grade diffuse astrocytoma or anaplastic astrocytoma. They manifest in younger patients, have a lesser degree of necrosis, are preferentially located in the frontal lobe, and carry a significantly better prognosis. Histologically, primary and secondary glioblastomas are largely indistinguishable, but they differ in their genetic and epigenetic profiles. Decisive genetic signposts of secondary glioblastoma are IDH1 mutations, which are absent in primary glioblastomas and which are associated with a hypermethylation phenotype. IDH1 mutations are the earliest detectable genetic alteration in precursor low-grade diffuse astrocytomas and in oligodendrogliomas, indicating that these tumors are derived from neural precursor cells that differ from those of primary glioblastomas. In this review, we summarize epidemiologic, clinical, histopathologic, genetic, and expression features of primary and secondary glioblastomas and the biologic consequences of IDH1 mutations. We conclude that this genetic alteration is a definitive diagnostic molecular marker of secondary glioblastomas and more reliable and objective than clinical criteria. Despite a similar histologic appearance, primary and secondary glioblastomas are distinct tumor entities that originate from different precursor cells and may require different therapeutic approaches.