Inhibition of Gap Junctions Sensitizes Primary Glioblastoma Cells for Temozolomide

Current status of precision oncology in adult glioblastoma

The concept of precision oncology, the application of targeted drugs based on comprehensive molecular profiling, has revolutionized treatment strategies in oncology. This review summarizes the current status of precision oncology in glioblastoma (GBM), the most common and aggressive primary brain tumor in adults with a median survival below 2 years. Targeted treatments without prior target verification have consistently failed. Patients with BRAF V600E-mutated GBM benefit from BRAF/MEK-inhibition, whereas targeting EGFR alterations was unsuccessful due to poor tumor penetration, tumor cell heterogeneity, and pathway redundancies. Systematic screening for actionable molecular alterations resulted in low rates (< 10%) of targeted treatments. Efficacy was observed in one-third and currently appears to be limited to BRAF-, VEGFR-, and mTOR-directed treatments. Advancing precision oncology for GBM requires consideration of pathways instead of single alterations, new trial concepts enabling rapid and adaptive drug evaluation, a focus on drugs with sufficient bioavailability in the CNS, and the extension of target discovery and validation to the tumor microenvironment, tumor cell networks, and their interaction with immune cells and neurons.

Central nervous system regulation of diffuse glioma growth and invasion: from single unit physiology to circuit remodeling

PURPOSE

Understanding the complex bidirectional interactions between neurons and glioma cells could help to identify new therapeutic targets. Herein, the techniques and application of novel neuroscience tools implemented to study the complex interactions between brain and malignant gliomas, their results, and the potential therapeutic opportunities were reviewed.

METHODS

Literature search was performed on PubMed between 2001 and 2023 using the keywords "glioma", "glioblastoma", "circuit remodeling", "plasticity", "neuron networks" and "cortical networks". Studies including grade 2 to 4 gliomas, diffuse midline gliomas, and diffuse intrinsic pontine gliomas were considered.

RESULTS

Glioma cells are connected through tumour microtubes and form a highly connected network within which pacemaker cells drive tumorigenesis. Unconnected cells have increased invasion capabilities. Glioma cells are also synaptically integrated within neural circuitry. Neurons promote tumour growth via paracrine and direct electrochemical mechanisms, including glutamatergic AMPA-receptors. Increased glutamate release in the tumor microenvironment and loss of peritumoral GABAergic inhibitory interneurons result in network hyperexcitability and secondary epilepsy. Functional imaging, local field potentials and subcortical mapping, performed in awake patients, have defined patterns of malignant circuit remodeling. Glioma-induced remodeling is frequent in language and even motor cortical networks, depending on tumour biological parameters, and influences functional outcomes.

CONCLUSION

These data offer new insights into glioma tumorigenesis. Future work will be needed to understand how tumor intrinsic molecular drivers influence neuron-glioma interactions but also to integrate these results to design new therapeutic options for patients.

The Alcatraz-Strategy: a roadmap to break the connectivity barrier in malignant brain tumours

In recent years, the discovery of functional and communicative cellular tumour networks has led to a new understanding of malignant primary brain tumours. In this review, the authors shed light on the diverse nature of cell-to-cell connections in brain tumours and propose an innovative treatment approach to address the detrimental connectivity of these networks. The proposed therapeutic outlook revolves around three main strategies: (a) supramarginal resection removing a substantial portion of the communicating tumour cell front far beyond the gadolinium-enhancing tumour mass, (b) morphological isolation at the single cell level disrupting structural cell-to-cell contacts facilitated by elongated cellular membrane protrusions known as tumour microtubes (TMs), and (c) functional isolation at the single cell level blocking TM-mediated intercellular cytosolic exchange and inhibiting neuronal excitatory input into the malignant network. We draw an analogy between the proposed therapeutic outlook and the Alcatraz Federal Penitentiary, where inmates faced an impassable sea barrier and experienced both spatial and functional isolation within individual cells. Based on current translational efforts and ongoing clinical trials, we propose the Alcatraz-Strategy as a promising framework to tackle the harmful effects of cellular brain tumour networks.

Deciphering Glioblastoma: Fundamental and Novel Insights into the Biology and Therapeutic Strategies of Gliomas

Gliomas constitute a diverse and complex array of tumors within the central nervous system (CNS), characterized by a wide range of prognostic outcomes and responses to therapeutic interventions. This literature review endeavors to conduct a thorough investigation of gliomas, with a particular emphasis on glioblastoma (GBM), beginning with their classification and epidemiological characteristics, evaluating their relative importance within the CNS tumor spectrum. We examine the immunological context of gliomas, unveiling the intricate immune environment and its ramifications for disease progression and therapeutic strategies. Moreover, we accentuate critical developments in understanding tumor behavior, focusing on recent research breakthroughs in treatment responses and the elucidation of cellular signaling pathways. Analyzing the most novel transcriptomic studies, we investigate the variations in gene expression patterns in glioma cells, assessing the prognostic and therapeutic implications of these genetic alterations. Furthermore, the role of epigenetic modifications in the pathogenesis of gliomas is underscored, suggesting that such changes are fundamental to tumor evolution and possible therapeutic advancements. In the end, this comparative oncological analysis situates GBM within the wider context of neoplasms, delineating both distinct and shared characteristics with other types of tumors.

Intrinsic and Microenvironmental Drivers of Glioblastoma Invasion

Gliomas are diffusely infiltrating brain tumors whose prognosis is strongly influenced by their extent of invasion into the surrounding brain tissue. While lower-grade gliomas present more circumscribed borders, high-grade gliomas are aggressive tumors with widespread brain infiltration and dissemination. Glioblastoma (GBM) is known for its high invasiveness and association with poor prognosis. Its low survival rate is due to the certainty of its recurrence, caused by microscopic brain infiltration which makes surgical eradication unattainable. New insights into GBM biology at the single-cell level have enabled the identification of mechanisms exploited by glioma cells for brain invasion. In this review, we explore the current understanding of several molecular pathways and mechanisms used by tumor cells to invade normal brain tissue. We address the intrinsic biological drivers of tumor cell invasion, by tackling how tumor cells interact with each other and with the tumor microenvironment (TME). We focus on the recently discovered neuronal niche in the TME, including local as well as distant neurons, contributing to glioma growth and invasion. We then address the mechanisms of invasion promoted by astrocytes and immune cells. Finally, we review the current literature on the therapeutic targeting of the molecular mechanisms of invasion.

Connexins Control Glial Inflammation in Various Neurological Diseases

Connexins (Cxs) form gap junctions through homotypic/heterotypic oligomerization. Cxs are initially synthesized in the endoplasmic reticulum, then assembled as hexamers in the Golgi apparatus before being integrated into the cell membrane as hemichannels. These hemichannels remain closed until they combine to create gap junctions, directly connecting neighboring cells. Changes in the intracellular or extracellular environment are believed to trigger the opening of hemichannels, creating a passage between the inside and outside of the cell. The size of the channel pore depends on the Cx isoform and cellular context-specific effects such as posttranslational modifications. Hemichannels allow various bioactive molecules, under ~1 kDa, to move in and out of the host cell in the direction of the electrochemical gradient. In this review, we explore the fundamental roles of Cxs and their clinical implications in various neurological dysfunctions, including hereditary diseases, ischemic brain disorders, degenerative conditions, demyelinating disorders, and psychiatric illnesses. The influence of Cxs on the pathomechanisms of different neurological disorders varies depending on the circumstances. Hemichannels are hypothesized to contribute to proinflammatory effects by releasing ATP, adenosine, glutamate, and other bioactive molecules, leading to neuroglial inflammation. Modulating Cxs' hemichannels has emerged as a promising therapeutic approach.

Sialic acid metabolism orchestrates transcellular connectivity and signaling in glioblastoma

BACKGROUND

In glioblastoma (GBM), the effects of altered glycocalyx are largely unexplored. The terminal moiety of cell coating glycans, sialic acid, is of paramount importance for cell-cell contacts. However, sialic acid turnover in gliomas and its impact on tumor networks remain unknown.

METHODS

We streamlined an experimental setup using organotypic human brain slice cultures as a framework for exploring brain glycobiology, including metabolic labeling of sialic acid moieties and quantification of glycocalyx changes. By live, 2-photon and high-resolution microscopy we have examined morphological and functional effects of altered sialic acid metabolism in GBM. By calcium imaging we investigated the effects of the altered glycocalyx on a functional level of GBM networks.

RESULTS

The visualization and quantitative analysis of newly synthesized sialic acids revealed a high rate of de novo sialylation in GBM cells. Sialyltrasferases and sialidases were highly expressed in GBM, indicating that significant turnover of sialic acids is involved in GBM pathology. Inhibition of either sialic acid biosynthesis or desialylation affected the pattern of tumor growth and lead to the alterations in the connectivity of glioblastoma cells network.

CONCLUSIONS

Our results indicate that sialic acid is essential for the establishment of GBM tumor and its cellular network. They highlight the importance of sialic acid for glioblastoma pathology and suggest that dynamics of sialylation have the potential to be targeted therapeutically.

Cellular Conversations in Glioblastoma Progression, Diagnosis and Treatment

Glioblastoma (GBM) is the most frequent malignancy among primary brain tumors in adults and one of the worst 5-year survival rates (< 7%) among all human cancers. Till now, treatments that target particular cell or intracellular metabolism have not improved patients' survival. GBM recruits healthy brain cells and subverts their processes to create a microenvironment that contributes to supporting tumor progression. This microenvironment encompasses a complex network in which malignant cells interact with each other and with normal and immune cells to promote tumor proliferation, angiogenesis, metastasis, immune suppression, and treatment resistance. Communication can be direct via cell-to-cell contact, mainly through adhesion molecules, tunneling nanotubes, gap junctions, or indirect by conventional paracrine signaling by cytokine, neurotransmitter, and extracellular vesicles. Understanding these communication routes could open up new avenues for the treatment of this lethal tumor. Hence, therapeutic approaches based on glioma cells` communication have recently drawn attention. This review summarizes recent findings on the crosstalk between glioblastoma cells and their tumor microenvironment, and the impact of this conversation on glioblastoma progression. We also discuss the mechanism of communication of glioma cells and their importance as therapeutic targets and diagnostic and prognostic biomarkers. Overall, understanding the biological mechanism of specific interactions in the tumor microenvironment may help in predicting patient prognosis and developing novel therapeutic strategies to target GBM.

Apoptotic effects of phenols from the twigs and leaves of Garcinia nujiangensis

In order to find potential agents for treating cancer disease in naturally occurring compounds, we conducted a systematic phytochemical investigation on the endemic species of Garcinia nujiangensis. Three new biphenyl derivatives (1-3) and one new polycyclic polyprenylated benzophenone (4), together with four known benzophenone analogues (5-8), have been isolated from the CH₂Cl₂ extract of the twigs and leaves of G. nujiangensis. Their structures were determined by detailed spectroscopic analyses and comparison with structurally related known analogues. Experimental and calculated ECD method was used to determine the absolute configuration of 1 and 4. Moreover, compounds 5-7 were isolated for the first time from this species. The cytotoxicities of the new compounds were evaluated using HL-60, HepG2, and A549 human cancer cell lines. Compound 4 showed more significant antiproliferative effects against HepG2 cells with an IC₅₀ value of 11.38 ± 0.79 μM than that of three biphenyl derivatives. The morphological features of apoptosis were evaluated in 4-treated HepG2 cells. Compound 4 effectively prevented the cell cycle progression of HepG2 cells in G₂ phase. Additionally, western blot analysis indicated that treatment of 4 on HepG2 cells led to decreased expression of anti-apoptotic Bcl-2 and pro-Caspase-3, and increased protein expression of both pro-apoptotic Bax and cleaved PARP with reference to β-actin. Overall, our results suggested that the active polycyclic polyprenylated benzophenone derivatives in the twigs and leaves of G. nujiangensis can be used as a valuable source of bioactive compounds for the pharmaceutical industry.

Brain Tumor Networks in Diffuse Glioma

Diffuse gliomas are primary brain tumors associated with a poor prognosis. Cellular and molecular mechanisms driving the invasive growth patterns and therapeutic resistance are incompletely understood. The emerging field of cancer neuroscience offers a novel approach to study these brain tumors in the context of their intricate interactions with the nervous system employing and combining methodological toolsets from neuroscience and oncology. Increasing evidence has shown how neurodevelopmental and neuronal-like mechanisms are hijacked leading to the discovery of multicellular brain tumor networks. Here, we review how gap junction-coupled tumor-tumor-astrocyte networks, as well as synaptic and paracrine neuron-tumor networks drive glioma progression. Molecular mechanisms of these malignant, homo- and heterotypic networks, and their complex interplay are reviewed. Lastly, potential clinical-translational implications and resulting therapeutic strategies are discussed.

Disconnecting multicellular networks in brain tumours

Cancer cells can organize and communicate in functional networks. Similarly to other networks in biology and sociology, these can be highly relevant for growth and resilience. In this Perspective, we demonstrate by the example of glioblastomas and other incurable brain tumours how versatile multicellular tumour networks are formed by two classes of long intercellular membrane protrusions: tumour microtubes and tunnelling nanotubes. The resulting networks drive tumour growth and resistance to standard therapies. This raises the question of how to disconnect brain tumour networks to halt tumour growth and whether this can make established therapies more effective. Emerging principles of tumour networks, their potential relevance for tumour types outside the brain and translational implications, including clinical trials that are already based on these discoveries, are discussed.

Glioblastoma Microenvironment and Cellular Interactions

Simple Summary

This paper summarizes the crosstalk between tumor/non-tumor cells and other elements of the glioblastoma (GB) microenvironment. In tumor pathology, glial cells result in the highest number of cancers, and GB is considered the most lethal tumor of the central nervous system (CNS). The tumor microenvironment (TME) is a complex peritumoral hallo composed of tumor cells and several non-tumor cells (e.g., nervous cells, stem cells, fibroblasts, vascular and immune cells), which might be a key factor for the ineffective treatment since the microenvironment modulates the biologic status of the tumor with the increase in its evasion capacity. A deeper understanding of cell–cell interactions in the TME and with the tumor cells could be the basis for a more efficient therapy.

Abstract

The central nervous system (CNS) represents a complex network of different cells, such as neurons, glial cells, and blood vessels. In tumor pathology, glial cells result in the highest number of cancers, and glioblastoma (GB) is considered the most lethal tumor in this region. The development of GB leads to the infiltration of healthy tissue through the interaction between all the elements of the brain network. This results in a GB microenvironment, a complex peritumoral hallo composed of tumor cells and several non-tumor cells (e.g., nervous cells, stem cells, fibroblasts, vascular and immune cells), which might be the principal factor for the ineffective treatment due to the fact that the microenvironment modulates the biologic status of the tumor with the increase in its evasion capacity. Crosstalk between glioma cells and the brain microenvironment finally inhibits the beneficial action of molecular pathways, favoring the development and invasion of the tumor and its increasing resistance to treatment. A deeper understanding of cell–cell interactions in the tumor microenvironment (TME) and with the tumor cells could be the basis for a more efficient therapy.

Phase I/II trial of meclofenamate in progressive MGMT-methylated glioblastoma under temozolomide second-line therapy-the MecMeth/NOA-24 trial

Background

Glioblastoma is the most frequent and malignant primary brain tumor. Even in the subgroup with O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation and favorable response to first-line therapy, survival after relapse is short (12 months). Standard therapy for recurrent MGMT-methylated glioblastoma is not standardized and may consist of re-resection, re-irradiation, and chemotherapy with temozolomide (TMZ), lomustine (CCNU), or a combination thereof. Preclinical results show that meclofenamate (MFA), originally developed as a nonsteroidal anti-inflammatory drug (NSAID) and registered in the USA, sensitizes glioblastoma cells to temozolomide-induced toxicity via inhibition of gap junction-mediated intercellular cytosolic traffic and demolishment of tumor microtube (TM)-based network morphology.

Methods

In this study, combined MFA/TMZ therapy will be administered (orally) in patients with first relapse of MGMT-methylated glioblastoma. A phase I component (6–12 patients, 2 dose levels of MFA + standard dose TMZ) evaluates safety and feasibility and determines the dose for the randomized phase II component (2 × 30 patients) with progression-free survival as the primary endpoint.

Discussion

This study is set up to assess toxicity and first indications of efficacy of MFA repurposed in the setting of a very difficult-to-treat recurrent tumor. The trial is a logical next step after the identification of the role of resistance-providing TMs in glioblastoma, and results will be crucial for further trials targeting TMs. In case of favorable results, MFA may constitute the first clinically feasible TM-targeted drug and therefore might bridge the idea of a TM-targeted therapeutic approach from basic insights into clinical reality.

Trial registration

EudraCT 2021-000708-39. Registered on 08 February 2021

Meclofenamate causes loss of cellular tethering and decoupling of functional networks in glioblastoma

BACKGROUND

Glioblastoma cells assemble to a syncytial communicating network based on tumor microtubes (TMs) as ultra-long membrane protrusions. The relationship between network architecture and transcriptional profile remains poorly investigated. Drugs that interfere with this syncytial connectivity such as meclofenamate (MFA) may be highly attractive for glioblastoma therapy.

METHODS

In a human neocortical slice model using glioblastoma cell populations of different transcriptional signatures, three-dimensional tumor networks were reconstructed, and TM-based intercellular connectivity was mapped on the basis of two-photon imaging data. MFA was used to modulate morphological and functional connectivity; downstream effects of MFA treatment were investigated by RNA sequencing and fluorescence-activated cell sorting (FACS) analysis.

RESULTS

TM-based network morphology strongly differed between the transcriptional cellular subtypes of glioblastoma and was dependent on axon guidance molecule expression. MFA revealed both a functional and morphological demolishment of glioblastoma network architectures which was reflected by a reduction of TM-mediated intercellular cytosolic traffic as well as a breakdown of TM length. RNA sequencing confirmed a downregulation of NCAM and axon guidance molecule signaling upon MFA treatment. Loss of glioblastoma communicating networks was accompanied by a failure in the upregulation of genes that are required for DNA repair in response to temozolomide (TMZ) treatment and culminated in profound treatment response to TMZ-mediated toxicity.

CONCLUSION

The capacity of TM formation reflects transcriptional cellular heterogeneity. MFA effectively demolishes functional and morphological TM-based syncytial network architectures. These findings might pave the way to a clinical implementation of MFA as a TM-targeted therapeutic approach.

A bioelectric model of carcinogenesis, including propagation of cell membrane depolarization and reversal therapies

As the main theory of carcinogenesis, the Somatic Mutation Theory, increasingly presents difficulties to explain some experimental observations, different theories are being proposed. A major alternative approach is the Tissue Organization Field Theory, which explains cancer origin as a tissue regulation disease instead of having a mainly cellular origin. This work fits in the latter hypothesis, proposing the bioelectric field, in particular the cell membrane polarization state, and ionic exchange through ion channels and gap junctions, as an important mechanism of cell communication and tissue organization and regulation. Taking into account recent experimental results and proposed bioelectric models, a computational model of cancer initiation was developed, including the propagation of a cell depolarization wave in the tissue under consideration. Cell depolarization leads to a change in its state, with the activation and deactivation of several regulation pathways, increasing cell proliferation and motility, changing its epigenetic state to a more stem cell-like behavior without the requirement of genomic mutation. The intercellular communication via gap junctions leads, in certain circumstances, to a bioelectric state propagation to neighbor cells, in a chain-like reaction, till an electric discontinuity is reached. However, this is a reversible process, and it was shown experimentally that, by implementing a therapy targeted on cell ion exchange channels, it is possible to reverse the state and repolarize cells. This mechanism can be an important alternative way in cancer prevention, diagnosis and therapy, and new experiments are proposed to test the presented hypothesis.

The advanced development of Cx43 and GAP-43 mediated intercellular networking in IDH1 wildtype diffuse and anaplastic gliomas with lower mitotic rate

PURPOSE

The biologic behavior and the therapeutic resistance of diffuse and anaplastic gliomas varies greatly. This may be explained by differences in cell-to-cell communication, determined by the Cx43-associated junctional activity and the microtubules-defined network, in which GAP-43 is the dominant structural component. We assessed the expression of these crucial communication proteins in samples of patients harboring WHO°II and III gliomas, graded according to the current 4th revised WHO classification.

METHODS

Tissue of adult patients with WHO°II and III gliomas, who underwent surgery between 2014 and 2018, were selected from our institutional biobank. GAP-43 and Cx43 expression was analyzed using IHC. Routine clinical and neuropathological findings were additionally retrieved from our institutional prospective database.

RESULTS

43 (57%) males and 33 (43%) females with a median age of 47 (IqR: 35-61) years were selected. IDH1 wildtype tumors showed a significantly higher expression of Cx43 (p = 0.014) and a tendency for increased GAP-43 production. Advanced Cx43 expression significantly correlated with lower mitosis rate (p = 0.014): more in IDH1 wildtype (r = - 0.57, p = 0.003) than in mutated gliomas (r = - 0.37, p = 0.019). There was no difference in Cx43 or GAP-43 expression in relation to anaplastic phenotype, Gadolinum-contrasted enhancement (CE) on MRI and advanced EGFR or p53 expression.

CONCLUSIONS

Intercellular communication tends to be more relevant in slower proliferating, e.g. lower malignant tumors. They could have more time to establish this network, providing longitudinally acquired resistance against specific oncological therapy. This feature matches the unfavorable IDH1 wildtype status of glioma and supports the noted malignant behavior of these tumors in the upcoming 5th WHO classification of gliomas.

From Laboratory Studies to Clinical Trials: Temozolomide Use in IDH-Mutant Gliomas

In this review, we discuss the use of the alkylating agent temozolomide (TMZ) in the treatment of IDH-mutant gliomas. We describe the challenges associated with TMZ in clinical (drug resistance and tumor recurrence) and preclinical settings (variabilities associated with in vitro models) in treating IDH-mutant glioma. Lastly, we summarize the emerging therapeutic targets that can potentially be used in combination with TMZ.

Inhibition of Intercellular Cytosolic Traffic via Gap Junctions Reinforces Lomustine-Induced Toxicity in Glioblastoma Independent of MGMT Promoter Methylation Status

Glioblastoma is a malignant brain tumor and one of the most lethal cancers in human. Temozolomide constitutes the standard chemotherapeutic agent, but only shows limited efficacy in glioblastoma patients with unmethylated O-6-methylguanine-DNA methyltransferase (MGMT) promoter status. Recently, it has been shown that glioblastoma cells communicate via particular ion-channels-so-called gap junctions. Interestingly, inhibition of these ion channels has been reported to render MGMT promoter-methylated glioblastoma cells more susceptible for a therapy with temozolomide. However, given the percentage of about 65% of glioblastoma patients with an unmethylated MGMT promoter methylation status, this treatment strategy is limited to only a minority of glioblastoma patients. In the present study we show that-in contrast to temozolomide-pharmacological inhibition of intercellular cytosolic traffic via gap junctions reinforces the antitumoral effects of chemotherapeutic agent lomustine, independent of MGMT promoter methylation status. In view of the growing interest of lomustine in glioblastoma first and second line therapy, these findings might provide a clinically-feasible way to profoundly augment chemotherapeutic effects for all glioblastoma patients.

Seizure outcome in temporal glioblastoma surgery: lobectomy as a supratotal resection regime outclasses conventional gross-total resection

Introduction

The postoperative seizure freedom represents an important secondary outcome measure in glioblastoma surgery. Recently, supra-total glioblastoma resection in terms of anterior temporal lobectomy (ATL) has gained growing attention with regard to superior long-term disease control for temporal-located glioblastoma compared to conventional gross-total resections (GTR). However, the impact of ATL on seizure outcome in these patients is unknown. We therefore analyzed ATL and GTR as differing extents of resection in regard of postoperative seizure control in patients with temporal glioblastoma and preoperative symptomatic seizures.

Methods

Between 2012 and 2018, 33 patients with preoperative seizures underwent GTR or ATL for temporal glioblastoma at the authors’ institution. Seizure outcome was assessed postoperatively and 6 months after tumor resection according to the International League Against Epilepsy (ILAE) classification and stratified into favorable (ILAE class 1) versus unfavorable (ILAE class 2–6).

Results

Overall, 23 out of 33 patients (70%) with preoperative seizures achieved favorable seizure outcome following resection of temporal located glioblastoma. For the ATL group, postoperative seizure freedom was present in 13 out of 13 patients (100%). In comparison, respective rates for the GTR group were 10 out of 20 patients (50%) (p = 0.002; OR 27; 95% CI 1.4–515.9).

Conclusions

ATL in terms of a supra-total resection strategy was associated with superior favorable seizure outcome following temporal glioblastoma resection compared to GTR. Regarding above mentioned survival benefit following ATL compared to GTR, ATL as an aggressive supra-total resection regime might constitute the surgical modality of choice for temporal-located glioblastoma.

Neuronal signatures in cancer

Despite advances in the treatment of solid tumors, the prognosis of patients with many cancers remains poor, particularly of those with primary and metastatic brain tumors. In the last years, "Cancer Neuroscience" emerged as novel field of research at the crossroads of oncology and classical neuroscience. In primary brain tumors, including glioblastoma (GB), communicating networks that render tumor cells resistant against cytotoxic therapies were identified. To build these networks, GB cells extend neurite-like protrusions called tumor microtubes (TMs). Synapses on TMs allow tumor cells to retrieve neuronal input that fosters growth. Single cell sequencing further revealed that primary brain tumors recapitulate many steps of neurodevelopment. Interestingly, neuronal characteristics, including the ability to extend neurite-like protrusions, neuronal gene expression signatures and interactions with neurons, have now been found not only in brain and neuroendocrine tumors but also in some cancers of epithelial origin. In this review, we will provide an overview about neurite-like protrusions as well as neurodevelopmental origins, hierarchies and gene expression signatures in cancer. We will also discuss how "Cancer Neuroscience" might provide a framework for the development of novel therapies.