Expansion of CD133-positive glioma cells in recurrent de novo glioblastomas after radiotherapy and chemotherapy

Red light-activated depletion of drug-refractory glioblastoma stem cells and chemosensitization of an acquired-resistant mesenchymal phenotype

Glioblastoma stem cells (GSCs) are potent tumor initiators resistant to radiochemotherapy, and this subpopulation is hypothesized to re-populate the tumor milieu due to selection following conventional therapies. Here, we show that 5-aminolevulinic acid (ALA) treatment-a pro-fluorophore used for fluorescence-guided cancer surgery-leads to elevated levels of fluorophore conversion in patient-derived GSC cultures, and subsequent red light-activation induces apoptosis in both intrinsically temozolomide chemotherapy-sensitive and -resistant GSC phenotypes. Red light irradiation of ALA-treated cultures also exhibits the ability to target mesenchymal GSCs (Mes-GSCs) with induced temozolomide resistance. Furthermore, sub-lethal light doses restore Mes-GSC sensitivity to temozolomide, abrogating GSC-acquired chemoresistance. These results suggest that ALA is not only useful for fluorescence-guided glioblastoma tumor resection, but that it also facilitates a GSC drug-resistance agnostic, red light-activated modality to mop up the surgical margins and prime subsequent chemotherapy.

Mitochondrial-Stem Cell Connection: Providing Additional Explanations for Understanding Cancer

The cancer paradigm is generally based on the somatic mutation model, asserting that cancer is a disease of genetic origin. The mitochondrial-stem cell connection (MSCC) proposes that tumorigenesis may result from an alteration of the mitochondria, specifically a chronic oxidative phosphorylation (OxPhos) insufficiency in stem cells, which forms cancer stem cells (CSCs) and leads to malignancy. Reviewed evidence suggests that the MSCC could provide a comprehensive understanding of all the different stages of cancer. The metabolism of cancer cells is altered (OxPhos insufficiency) and must be compensated by using the glycolysis and the glutaminolysis pathways, which are essential to their growth. The altered mitochondria regulate the tumor microenvironment, which is also necessary for cancer evolution. Therefore, the MSCC could help improve our understanding of tumorigenesis, metastases, the efficiency of standard treatments, and relapses.

Molecular diversity in isocitrate dehydrogenase-wild-type glioblastoma

In the dynamic landscape of glioblastoma, the 2021 World Health Organization Classification of Central Nervous System tumours endeavoured to establish biological homogeneity, yet isocitrate dehydrogenase-wild-type (IDH-wt) glioblastoma persists as a tapestry of clinical and molecular diversity. Intertumoural heterogeneity in IDH-wt glioblastoma presents a formidable challenge in treatment strategies. Recent strides in genetics and molecular biology have enhanced diagnostic precision, revealing distinct subtypes and invasive patterns that influence survival in patients with IDH-wt glioblastoma. Genetic and molecular biomarkers, such as the overexpression of neurofibromin 1, phosphatase and tensin homolog and/or cyclin-dependent kinase inhibitor 2A, along with specific immune cell abundance and neurotransmitters, correlate with favourable outcomes. Conversely, increased expression of epidermal growth factor receptor tyrosine kinase, platelet-derived growth factor receptor alpha and/or vascular endothelial growth factor receptor, coupled with the prevalence of glioma stem cells, tumour-associated myeloid cells, regulatory T cells and exhausted effector cells, signifies an unfavourable prognosis. The methylation status of O6-methylguanine-DNA methyltransferase and the influence of microenvironmental factors and neurotransmitters further shape treatment responses. Understanding intertumoural heterogeneity is complemented by insights into intratumoural dynamics and cellular interactions within the tumour microenvironment. Glioma stem cells and immune cell composition significantly impact progression and outcomes, emphasizing the need for personalized therapies targeting pro-tumoural signalling pathways and resistance mechanisms. A successful glioblastoma management demands biomarker identification, combination therapies and a nuanced approach considering intratumoural variability. These advancements herald a transformative era in glioblastoma comprehension and treatment.

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.

Tumor Niches: Perspectives for Targeted Therapies in Glioblastoma

Significance: Glioblastoma (GBM), the most common and lethal primary brain tumor with a median survival rate of only 15 months and a 5-year survival rate of only 6.8%, remains largely incurable despite the intensive multimodal treatment of surgical resection and radiochemotherapy. Developing effective new therapies is an unmet need for patients with GBM. Recent Advances: Targeted therapies, such as antiangiogenesis therapy and immunotherapy, show great promise in treating GBM based upon increasing knowledge about brain tumor biology. Single-cell transcriptomics reveals the plasticity, heterogeneity, and dynamics of tumor cells during GBM development and progression. Critical Issues: While antiangiogenesis therapy and immunotherapy have been highly effective in some types of cancer, the disappointing results from clinical trials represent continued challenges in applying these treatments to GBM. Molecular and cellular heterogeneity of GBM is developed temporally and spatially, which profoundly contributes to therapeutic resistance and tumor recurrence. Future Directions: Deciphering mechanisms of tumor heterogeneity and mapping tumor niche trajectories and functions will provide a foundation for the development of more effective therapies for GBM patients. In this review, we discuss five different tumor niches and the intercellular and intracellular communications among these niches, including the perivascular, hypoxic, invasive, immunosuppressive, and glioma-stem cell niches. We also highlight the cellular and molecular biology of these niches and discuss potential strategies to target these tumor niches for GBM therapy. Antioxid. Redox Signal. 39, 904-922.

Targeting EZH2 regulates the biological characteristics of glioma stem cells via the Notch1 pathway

Glioma is the most common malignant brain tumor, and its behavior is closely related to the presence of glioma stem cells (GSCs). We found that the enhancer of zeste homolog 2 (EZH2) is highly expressed in glioma and that its expression is correlated with the prognosis of glioblastoma multiforme (GBM) in two databases: The Cancer Genome Atlas and the Chinese Glioma Genome Atlas. Additionally, EZH2 is known to regulate the stemness-associated gene expression, proliferation, and invasion ability of GSCs, which may be achieved through the activation of the STAT3 and Notch1 pathways. Furthermore, we demonstrated the effect of the EZH2-specific inhibitor GSK126 on GSCs; these results not only corroborate our hypothesis, but also provide a potential novel treatment approach for glioma.

Cancer Stem Cells and Glioblastoma: Time for Innovative Biomarkers of Radio-Resistance?

Despite countless papers in the field of radioresistance, researchers are still far from clearly understanding the mechanisms triggered in glioblastoma. Cancer stem cells (CSC) are important to the growth and spread of cancer, according to many studies. In addition, more recently, it has been suggested that CSCs have an impact on glioblastoma patients' prognosis, tumor aggressiveness, and treatment outcomes. In reviewing this new area of biology, we will provide a summary of the most recent research on CSCs and their role in the response to radio-chemotherapy in GB. In this review, we will examine the radiosensitivity of stem cells. Moreover, we summarize the current knowledge of the biomarkers of stemness and evaluate their potential function in the study of radiosensitivity.

Role of SH3GLB1 in the regulation of CD133 expression in GBM cells

BACKGROUND

Glioblastoma (GBM), a malignant brain tumor, has poor survival outcomes due to recurrence or drug resistance. We found that SH3GLB1 is a crucial factor for cells to evade temozolomide (TMZ) cytotoxicity through autophagy-mediated oxidative phosphorylation, which is associated with CD133 levels. Therefore, we propose that SH3GLB1 participate in the impact on tumor-initiating cells (TICs).

METHODS

The parental, the derived resistant cell lines and their CD133⁺ cells were used, and the levels of the proteins were compared by western blotting. Then RNA interference was applied to observe the effects of the target protein on TIC-related features. Finally, in vitro transcription assays were used to validate the association between SH3GLB1 and CD133.

RESULTS

The CD133⁺ cells from resistant cells with enhanced SH3GLB1 levels more easily survived cytotoxic treatment than those from the parental cells. Inhibition of SH3GLB1 attenuated frequency and size of spheroid formation, and the levels of CD133 and histone 4 lysine 5 (H4K5) acetylation can be simultaneously regulated by SH3GLB1 modification. The H4K5 acetylation of the CD133 promoter was later suggested to be the mediating mechanism of SH3GLB1.

CONCLUSIONS

These data indicate that SH3GLB1 can regulate CD133 expression, suggesting that the protein plays a crucial role in TICs. Our findings on the effects of SH3GLB1 on the cells will help explain tumor resistance formation.

3D Cell Models in Radiobiology: Improving the Predictive Value of In Vitro Research

Cancer is intrinsically complex, comprising both heterogeneous cellular composition and extracellular matrix. In vitro cancer research models have been widely used in the past to model and study cancer. Although two-dimensional (2D) cell culture models have traditionally been used for cancer research, they have many limitations, such as the disturbance of interactions between cellular and extracellular environments and changes in cell morphology, polarity, division mechanism, differentiation and cell motion. Moreover, 2D cell models are usually monotypic. This implies that 2D tumor models are ineffective at accurately recapitulating complex aspects of tumor cell growth, as well as their radiation responses. Over the past decade there has been significant uptake of three-dimensional (3D) in vitro models by cancer researchers, highlighting a complementary model for studies of radiation effects on tumors, especially in conjunction with chemotherapy. The introduction of 3D cell culture approaches aims to model in vivo tissue interactions with radiation by positioning itself halfway between 2D cell and animal models, and thus opening up new possibilities in the study of radiation response mechanisms of healthy and tumor tissues.

Cancer Stem Cells in Tumours of the Central Nervous System in Children: A Comprehensive Review

Cancer stem cells (CSCs) are a subgroup of cells found in various kinds of tumours with stem cell characteristics, such as self-renewal, induced differentiation, and tumourigenicity. The existence of CSCs is regarded as a major source of tumour recurrence, metastasis, and resistance to conventional chemotherapy and radiation treatment. Tumours of the central nervous system (CNS) are the most common solid tumours in children, which have many different types including highly malignant embryonal tumours and midline gliomas, and low-grade gliomas with favourable prognoses. Stem cells from the CNS tumours have been largely found and reported by researchers in the last decade and their roles in tumour biology have been deeply studied. However, the cross-talk of CSCs among different CNS tumour types and their clinical impacts have been rarely discussed. This article comprehensively reviews the achievements in research on CSCs in paediatric CNS tumours. Biological functions, diagnostic values, and therapeutic perspectives are reviewed in detail. Further investigations into CSCs are warranted to improve the clinical practice in treating children with CNS tumours.

The "Superoncogene" Myc at the Crossroad between Metabolism and Gene Expression in Glioblastoma Multiforme

The concept of the Myc (c-myc, n-myc, l-myc) oncogene as a canonical, DNA-bound transcription factor has consistently changed over the past few years. Indeed, Myc controls gene expression programs at multiple levels: directly binding chromatin and recruiting transcriptional coregulators; modulating the activity of RNA polymerases (RNAPs); and drawing chromatin topology. Therefore, it is evident that Myc deregulation in cancer is a dramatic event. Glioblastoma multiforme (GBM) is the most lethal, still incurable, brain cancer in adults, and it is characterized in most cases by Myc deregulation. Metabolic rewiring typically occurs in cancer cells, and GBM undergoes profound metabolic changes to supply increased energy demand. In nontransformed cells, Myc tightly controls metabolic pathways to maintain cellular homeostasis. Consistently, in Myc-overexpressing cancer cells, including GBM cells, these highly controlled metabolic routes are affected by enhanced Myc activity and show substantial alterations. On the other hand, deregulated cancer metabolism impacts Myc expression and function, placing Myc at the intersection between metabolic pathway activation and gene expression. In this review paper, we summarize the available information on GBM metabolism with a specific focus on the control of the Myc oncogene that, in turn, rules the activation of metabolic signals, ensuring GBM growth.

Kavain ablates the radio-resistance of IDH-wildtype glioblastoma by targeting LITAF/NF-κB pathway

BACKGROUND

Glioblastoma multiforma (GBM) is the most malignant intrinsic tumor of the central nervous system (CNS), with high morbidity of 3.19/100,000 per year and a poor 5-year survival rate (< 5%) worldwide. Numerous studies have indicated that GBM shows remarkable radioresistance and aggressive recurrence. However, the mechanisms to endow GBM cells with radioresistance are complex and unclear.

METHODS

Cell growth curve and colony formation assays were used to analyze the radioresistance of GBM. Immunoprecipitation and immunoblotting experiments were carried out to analyze protein expression and interaction.

RESULTS

In the present study, we found that LITAF, lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α factor, is up-regulated both in mRNA and protein in GBM tumors. Meanwhile, we observed that high LITAF expression contributes to radioresistance of GBM cell lines (including U87, U251, DK, and AM38 cells), indicated by knockout or knockdown of LITAF in cells sensitizing them to radiation treatment both in vitro and in vivo. Furthermore, we demonstrated that kavain, an active constituent of Piper methysticum Forst., effectively ablates GSC-like cells' (such as CD133 + U87, U251, DK, and AM38 populations) radioresistance in a LITAF-dependent manner.

CONCLUSION

In mechanism, our results indicated that 1) the elevation of LITAF in GBM cells activates the NF-κB pathway to promote mesenchymal transition, and 2) kavain disturbs STAT6B/LITAF protein interaction and then expels LITAF from the nucleus. Therefore, we consider that kavain may be a potential candidate to develop an irradiation therapy adjuvant for GBM.

The Molecular and Cellular Strategies of Glioblastoma and Non-Small-Cell Lung Cancer Cells Conferring Radioresistance

Ionizing radiation (IR) has been shown to play a crucial role in the treatment of glioblastoma (GBM; grade IV) and non-small-cell lung cancer (NSCLC). Nevertheless, recent studies have indicated that radiotherapy can offer only palliation owing to the radioresistance of GBM and NSCLC. Therefore, delineating the major radioresistance mechanisms may provide novel therapeutic approaches to sensitize these diseases to IR and improve patient outcomes. This review provides insights into the molecular and cellular mechanisms underlying GBM and NSCLC radioresistance, where it sheds light on the role played by cancer stem cells (CSCs), as well as discusses comprehensively how the cellular dormancy/non-proliferating state and polyploidy impact on their survival and relapse post-IR exposure.

KRAB-ZFPs and cancer stem cells identity

Studies on carcinogenesis continue to provide new information about different disease-related processes. Among others, much research has focused on the involvement of cancer stem cells (CSCs) in tumor initiation and progression. Studying the similarities and differences between CSCs and physiological stem cells (SCs) allows for a better understanding of cancer biology. Recently, it was shown that stem cell identity is partially governed by the Krϋppel-associated box domain zinc finger proteins (KRAB-ZFPs), the biggest family of transcription regulators. Several KRAB-ZFP factors exert a known effect in tumor cells, acting as tumor suppressor genes (TSGs) or oncogenes, yet their role in CSCs is still poorly characterized. Here, we review recent studies regarding the influence of KRAB-ZFPs and their cofactor protein TRIM28 on CSCs phenotype, stemness features, migration and invasion potential, metastasis, and expression of parental markers.

Differences in stem cell marker and osteopontin expression in primary and recurrent glioblastoma

Background

Despite of a multimodal approach, recurrences can hardly be prevented in glioblastoma. This may be in part due to so called glioma stem cells. However, there is no established marker to identify these stem cells.

Methods

Paired samples from glioma patients were analyzed by immunohistochemistry for expression of the following stem cell markers: CD133, Musashi, Nanog, Nestin, octamer-binding transcription factor 4 (Oct4), and sex determining region Y-box 2 (Sox2). In addition, the expression of osteopontin (OPN) was investigated. The relative number of positively stained cells was determined. By means of Kaplan–Meier analysis, a possible association with overall survival by marker expression was investigated.

Results

Sixty tissue samples from 30 patients (17 male, 13 female) were available for analysis. For Nestin, Musashi and OPN a significant increase was seen. There was also an increase (not significant) for CD133 and Oct4. Patients with mutated Isocitrate Dehydrogenase-1/2 (IDH-1/2) status had a reduced expression for CD133 and Nestin in their recurrent tumors. Significant correlations were seen for CD133 and Nanog between OPN in the primary and recurrent tumor and between CD133 and Nestin in recurrent tumors. By confocal imaging we could demonstrate a co-expression of CD133 and Nestin within recurrent glioma cells. Patients with high CD133 expression had a worse prognosis (22.6 vs 41.1 months, p = 0.013). A similar trend was seen for elevated Nestin levels (24.9 vs 41.1 months, p = 0.08).

Conclusions

Most of the evaluated markers showed an increased expression in their recurrent tumor. CD133 and Nestin were associated with survival and are candidate markers for further clinical investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02510-4.

Factors affecting the radiation response in glioblastoma

Glioblastoma (GBM) is a highly invasive primary brain tumor in adults with a 5-year survival rate of less than 10%. Conventional radiotherapy with photons, along with concurrent and adjuvant temozolomide, is the mainstay for treatment of GBM although no significant improvement in survival rates has been observed over the last 20 years. Inherent factors such as tumor hypoxia, radioresistant GBM stem cells, and upregulated DNA damage response mechanisms are well established as contributing to treatment resistance and tumor recurrence. While it is understandable that efforts have focused on targeting these factors to overcome this phenotype, there have also been striking advances in precision radiotherapy techniques, including proton beam therapy and carbon ion radiotherapy (CIRT). These enable higher doses of radiation to be delivered precisely to the tumor, while minimizing doses to surrounding normal tissues and organs at risk. These alternative radiotherapy techniques also benefit from increased biological effectiveness, particularly in the case of CIRT. Although not researched extensively to date, combining these new radiation modalities with radio-enhancing agents may be particularly effective in improving outcomes for patients with GBM.

Immunotherapy Resistance in Glioblastoma

Glioblastoma is the most common malignant primary brain tumor in adults. Despite treatment consisting of surgical resection followed by radiotherapy and adjuvant chemotherapy, survival remains poor at a rate of 26.5% at 2 years. Recent successes in using immunotherapies to treat a number of solid and hematologic cancers have led to a growing interest in harnessing the immune system to target glioblastoma. Several studies have examined the efficacy of various immunotherapies, including checkpoint inhibitors, vaccines, adoptive transfer of lymphocytes, and oncolytic virotherapy in both pre-clinical and clinical settings. However, these therapies have yielded mixed results at best when applied to glioblastoma. While the initial failures of immunotherapy were thought to reflect the immunoprivileged environment of the brain, more recent studies have revealed immune escape mechanisms created by the tumor itself and adaptive resistance acquired in response to therapy. Several of these resistance mechanisms hijack key signaling pathways within the immune system to create a protumoral microenvironment. In this review, we discuss immunotherapies that have been trialed in glioblastoma, mechanisms of tumor resistance, and strategies to sensitize these tumors to immunotherapies. Insights gained from the studies summarized here may help pave the way for novel therapies to overcome barriers that have thus far limited the success of immunotherapy in glioblastoma.

Mesenchymal type neuroblastoma cells escape ALK inhibitors

Cancer therapy frequently fails due to the emergence of resistance. Many tumors include phenotypically immature tumor cells, which have been implicated in therapy resistance. Neuroblastoma cells can adopt a lineage committed adrenergic (ADRN) or an immature mesenchymal (MES) state. They differ in epigenetic landscape and transcription factors, and MES cells are more resistant to chemotherapy. Here we analyzed the response of MES cells to targeted drugs. Activating ALK mutations are frequently found in neuroblastoma and ALK inhibitors (ALKi) are in clinical trials. ALKi treatment of ADRN neuroblastoma cells with a tumor-driving ALK mutation induced cell death. Conversely, MES cells did not express either mutant or wild-type ALK and were resistant to ALKi, and MES cells formed tumors that progressed under ALKi therapy. In assessing the role of MES cells in relapse development, TRAIL was identified to specifically induce apoptosis in MES cells and suppress MES tumor growth. Addition of TRAIL to ALKi treatment of neuroblastoma xenografts delayed relapses in a subset of the animals, suggesting a role for MES cells in relapse formation. While ADRN cells resembled normal embryonal neuroblasts, MES cells resembled immature precursor cells which also lacked ALK expression. Resistance to targeted drugs can therefore be an intrinsic property of immature cancer cells based on their resemblance to developmental precursors.

DNA Damage Response in Glioblastoma: Mechanism for Treatment Resistance and Emerging Therapeutic Strategies

ABSTRACT

Glioblastoma (GBM) is an intrinsically treatment-resistant tumor and has been shown to upregulate DNA damage response (DDR) components after treatment. DNA damage response signaling mediates treatment resistance by promoting cell cycle arrest in order to allow for DNA damage repair and avoid mitotic catastrophe. Therefore, targeting the DDR pathway is an attractive strategy to combat treatment resistance in GBM. In this review, we discuss the different DDR pathways and then summarize the current preclinical evidence for DDR inhibitors in GBM, as well as completed and ongoing clinical trials.

Exploring the cytotoxicity and anticancer effects of doxycycline and azithromycin on human glioblastoma multiforme cells

BACKGROUND

Previous studies had reported on the cytotoxic activities of generic antibiotics such as doxycycline (DOXY) and azithromycin (AZI) in multiple types of human cancers. Given that resistance to standard anti-glioblastoma multiforme (GBM) drug [temozolomide (TMZ)] is common and inevitable, alternative candidates are greatly needed.

PURPOSE AND METHOD

The present study was undertaken to explore the cytotoxicity and anticancer effects of DOXY and AZI on human GBM U87 cells via 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), Hoechst, Annexin V-FITC/PI, and clonogenic assays. CompuSyn software was used to determine the combination index (CI) for DOXY+AZI.

RESULT

Individual treatment with DOXY and AZI decreased U87 cell viability in dose- and time-dependent, and quantitatively comparable to TMZ. Nevertheless, combinations of both antibiotics evidenced antagonistic behaviour in U87 cells. Increased apoptotic event was also observed with the individual treatment of DOXY and AZI. Furthermore, the proliferative and clonogenic capability of 21-day survived U87 cells was completely terminated by DOXY and AZI, but not TMZ.

CONCLUSION

The antiproliferative and apoptosis-inducing activity exhibited by both antibiotics against U87 cells demonstrates their potential as a likely alternative to combat GBM. It would be interesting to find out more about their molecular players and cytotoxic effects in different types of GBM cells, including glioma stem cells (GSCs).

Role of glioblastoma stem cells in cancer therapeutic resistance: a perspective on antineoplastic agents from natural sources and chemical derivatives

Glioblastoma (GBM) is the highest-grade form of glioma, as well as one of the most aggressive types of cancer, exhibiting rapid cellular growth and highly invasive behavior. Despite significant advances in diagnosis and therapy in recent decades, the outcomes for high-grade gliomas (WHO grades III-IV) remain unfavorable, with a median overall survival time of 15–18 months. The concept of cancer stem cells (CSCs) has emerged and provided new insight into GBM resistance and management. CSCs can self-renew and initiate tumor growth and are also responsible for tumor cell heterogeneity and the induction of systemic immunosuppression. The idea that GBM resistance could be dependent on innate differences in the sensitivity of clonogenic glial stem cells (GSCs) to chemotherapeutic drugs/radiation prompted the scientific community to rethink the understanding of GBM growth and therapies directed at eliminating these cells or modulating their stemness. This review aims to describe major intrinsic and extrinsic mechanisms that mediate chemoradioresistant GSCs and therapies based on antineoplastic agents from natural sources, derivatives, and synthetics used alone or in synergistic combination with conventional treatment. We will also address ongoing clinical trials focused on these promising targets. Although the development of effective therapy for GBM remains a major challenge in molecular oncology, GSC knowledge can offer new directions for a promising future.

Lidocaine inhibits glioma cell proliferation, migration and invasion by modulating the circEZH2/miR-181b-5p pathway

BACKGROUND

Lidocaine is well known as a local anesthetic that has been reported to play an antitumor role in numerous cancers, including glioma. Circular RNAs (circRNAs) play multiple biological roles in cancers. The aim of this study was to determine the effects of lidocaine in glioma in vitro and in vivo and explore functional mechanisms.

METHODS

The effects of lidocaine on glioma progression were investigated by cell proliferation, migration and invasion using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, colony formation assay and transwell assay. The expression of CD133 and glial fibrillary acidic protein (GFAP) was quantified by western blot to assess cell differentiation. The expression of circEZH2 and miR-181b-5p was detected by a quantitative real-time PCR (qRT-PCR). The target relationship between circEZH2 and miR-181b-5p was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. The effect of lidocaine on tumor growth in vivo was investigated by establishing Xenograft models.

RESULTS

Lidocaine inhibited proliferation, migration, invasion and induced differentiation of glioma cells in vitro. Lidocaine suppressed the expression of circEZH2, and circEZH2 was highly expressed in glioma tissues and cells. CircEZH2 overexpression partly inhibited the function of lidocaine. CircEZH2 was a sponge of miR-181b-5p, and miR-181b-5p was downregulated in glioma tissues and cells. Besides, miR-181b-5p restoration reversed the effects of circEZH2 overexpression to repress the malignant behaviors of glioma cells. In addition, lidocaine mediated the circEZH2/miR-181b-5p axis to inhibit tumor growth in vivo.

CONCLUSION

Lidocaine suppressed glioma progression by modulating the circEZH2/miR-181b-5p pathway.

Biological Characterization and Therapeutics for Subscalp Recurrent in Intracranial Glioblastoma

Purpose

Gliomas are common intracranial tumors, of which 70% are malignant gliomas. Glioblastoma multiforme (GBM) is the most aggressive tumor, and patients with GBM have a median survival time of only 9–12 months; extracranial recurrence of GBM is very rare. A therapeutic strategy for this kind of recurrent tumor is lacking.

Materials and Methods

We present a case of a patient with extracranial recurrence of subscalp GBM. The subscalp tumor was resected and xenotransplanted into BALB/C nude mice. Then, glioma cells were isolated from the xenograft models and passaged in vitro. HE staining, immunohistochemistry, CCK-8 assays, karyotypic analysis, short tandem repeat STR analysis and flow cytometry were used to analyze the biological characteristics and malignant phenotype of these established cells. The cells and xenografts were then used as preclinical models to evaluate the antitumor efficacy of oncolytic herpes simplex virus 1 (oHSV-1).

Results

The isolated cells, which were named BT-01, were positive for Nestin and GFAP. The main characteristics of BT-01 cells were that they harbored glioblastoma stem-like cells (GSCs) and that they possessed highly aggressive migration capacities compared with the existing cell lines U87-MG and U251-MG. Moreover, BT-01 cells tolerated the chemotherapeutic drug temozolomide. Our study showed that oHSV-1 could replicate in and repress the growth of BT-01 cells and significantly inhibit tumor growth in xenograft models.

Conclusion

Taken together, our results showed that a new recurrent glioblastoma cell line was established, which can be useful for research on recurrent glioblastoma. We provided a reliable preclinical model to evaluate the antitumor efficacy of oHSV-1 in vivo and a promising therapy for recurrent GBM.

Advances in histone deacetylase inhibitors in targeting glioblastoma stem cells

Glioblastoma multiforme (GBM) is a lethal grade IV glioma (WHO classification) and widely prevalent primary brain tumor in adults. GBM tumors harbor cellular heterogeneity with the presence of a small subpopulation of tumor cells, described as GBM cancer stem cells (CSCs) that pose resistance to standard anticancer regimens and eventually mediate aggressive relapse or intractable progressive GBM. Existing conventional anticancer therapies for GBM do not target GBM stem cells and are mostly palliative; therefore, exploration of new strategies to target stem cells of GBM has to be prioritized for the development of effective GBM therapy. Recent developments in the understanding of GBM pathophysiology demonstrated dysregulation of epigenetic mechanisms along with the genetic changes in GBM CSCs. Altered expression/activity of key epigenetic regulators, especially histone deacetylases (HDACs) in GBM stem cells has been associated with poor prognosis; inhibiting the activity of HDACs using histone deacetylase inhibitors (HDACi) has been promising as mono-therapeutic in targeting GBM and in sensitizing GBM stem cells to an existing anticancer regimen. Here, we review the development of pan/selective HDACi as potential anticancer agents in targeting the stem cells of glioblastoma as a mono or combination therapy.

Ly6G+ inflammatory cells enable the conversion of cancer cells to cancer stem cells in an irradiated glioblastoma model

Most glioblastomas frequently recur at sites of radiotherapy, but it is unclear if changes in the tumor microenvironment due to radiotherapy influence glioblastoma recurrence. Here, we demonstrate that radiation-induced senescent glioblastoma cells exhibit a senescence-associated secretory phenotype that functions through NFκB signaling to influence changes in the tumor microenvironment, such as recruitment of Ly6G⁺ inflammatory cells and vessel formation. In particular, Ly6G⁺ cells promote conversion of glioblastoma cells to glioblastoma stem cells (GSCs) through the NOS2-NO-ID4 regulatory axis. Specific inhibition of NFκB signaling in irradiated glioma cells using the IκBα super repressor prevents changes in the tumor microenvironment and dedifferentiation of glioblastoma cells. Treatment with Ly6G-neutralizing antibodies also reduces the number of GSCs and prolongs survival in tumor-bearing mice after radiotherapy. Clinically, a positive correlation exists between Ly6G⁺ cells and the NOS2-NO-ID4 regulatory axis in patients diagnosed with recurrent glioblastoma. Together, our results illustrate important roles for Ly6G⁺ inflammatory cells recruited by radiation-induced SASP in cancer cell dedifferentiation and tumor recurrence.

Importance of GFAP isoform-specific analyses in astrocytoma

Gliomas are a heterogenous group of malignant primary brain tumors that arise from glia cells or their progenitors and rely on accurate diagnosis for prognosis and treatment strategies. Although recent developments in the molecular biology of glioma have improved diagnosis, classical histological methods and biomarkers are still being used. The glial fibrillary acidic protein (GFAP) is a classical marker of astrocytoma, both in clinical and experimental settings. GFAP is used to determine glial differentiation, which is associated with a less malignant tumor. However, since GFAP is not only expressed by mature astrocytes but also by radial glia during development and neural stem cells in the adult brain, we hypothesized that GFAP expression in astrocytoma might not be a direct indication of glial differentiation and a less malignant phenotype. Therefore, we here review all existing literature from 1972 up to 2018 on GFAP expression in astrocytoma patient material to revisit GFAP as a marker of lower grade, more differentiated astrocytoma. We conclude that GFAP is heterogeneously expressed in astrocytoma, which most likely masks a consistent correlation of GFAP expression to astrocytoma malignancy grade. The GFAP positive cell population contains cells with differences in morphology, function, and differentiation state showing that GFAP is not merely a marker of less malignant and more differentiated astrocytoma. We suggest that discriminating between the GFAP isoforms GFAPδ and GFAPα will improve the accuracy of assessing the differentiation state of astrocytoma in clinical and experimental settings and will benefit glioma classification.

PIM kinases mediate resistance of glioblastoma cells to TRAIL by a p62/SQSTM1-dependent mechanism

Glioblastoma (GBM) is the most common and aggressive brain tumor and is associated with poor prognosis. GBM cells are frequently resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and finding new combinatorial therapies to sensitize glioma cells to TRAIL remains an important challenge. PIM kinases are serine/threonine kinases that promote cell survival and proliferation and are highly expressed in different tumors. In this work, we studied the role of PIM kinases as regulators of TRAIL sensitivity in GBM cells. Remarkably, PIM inhibition or knockdown facilitated activation by TRAIL of a TRAIL-R2/DR5-mediated and mitochondria-operated apoptotic pathway in TRAIL-resistant GBM cells. The sensitizing effect of PIM knockdown on TRAIL-induced apoptosis was mediated by enhanced caspase-8 recruitment to and activation at the death-inducing signaling complex (DISC). Interestingly, TRAIL-induced internalization of TRAIL-R2/DR5 was significantly reduced in PIM knockdown cells. Phospho-proteome profiling revealed a decreased phosphorylation of p62/SQSTM1 after PIM knockdown. Our results also showed an interaction between p62/SQSTM1 and the DISC that was reverted after PIM knockdown. In line with this, p62/SQSTM1 ablation increased TRAIL-R2/DR5 levels and facilitated TRAIL-induced caspase-8 activation, revealing an inhibitory role of p62/SQSTM1 in TRAIL-mediated apoptosis in GBM. Conversely, upregulation of TRAIL-R2/DR5 upon PIM inhibition and apoptosis induced by the combination of PIM inhibitor and TRAIL were abrogated by a constitutively phosphorylated p62/SQSTM1^S332E mutant. Globally, our data represent the first evidence that PIM kinases regulate TRAIL-induced apoptosis in GBM and identify a specific role of p62/SQSTM1^Ser332 phosphorylation in the regulation of the extrinsic apoptosis pathway activated by TRAIL.

Activation of Dopamine Receptor 2 Prompts Transcriptomic and Metabolic Plasticity in Glioblastoma

Glioblastoma (GBM) is one of the most aggressive and lethal tumor types. Evidence continues to accrue indicating that the complex relationship between GBM and the brain microenvironment contributes to this malignant phenotype. However, the interaction between GBM and neurotransmitters, signaling molecules involved in neuronal communication, remains incompletely understood. Here we examined, using human patient-derived xenograft lines, how the monoamine dopamine influences GBM cells. We demonstrate that GBM cells express dopamine receptor 2 (DRD2), with elevated expression in the glioma-initiating cell (GIC) population. Stimulation of DRD2 caused a neuron-like hyperpolarization exclusively in GICs. In addition, long-term activation of DRD2 heightened the sphere-forming capacity of GBM cells, as well as tumor engraftment efficiency in both male and female mice. Mechanistic investigation revealed that DRD2 signaling activates the hypoxia response and functionally alters metabolism. Finally, we found that GBM cells synthesize and secrete dopamine themselves, suggesting a potential autocrine mechanism. These results identify dopamine signaling as a potential therapeutic target in GBM and further highlight neurotransmitters as a key feature of the pro-tumor microenvironment.SIGNIFICANCE STATEMENT This work offers critical insight into the role of the neurotransmitter dopamine in the progression of GBM. We show that dopamine induces specific changes in the state of tumor cells, augmenting their growth and shifting them to a more stem-cell like state. Further, our data illustrate that dopamine can alter the metabolic behavior of GBM cells, increasing glycolysis. Finally, this work demonstrates that GBM cells, including tumor samples from patients, can synthesize and secrete dopamine, suggesting an autocrine signaling process underlying these results. These results describe a novel connection between neurotransmitters and brain cancer, further highlighting the critical influence of the brain milieu on GBM.

Distribution of cancer stem cells in two human brain gliomas

There is compelling evidence that brain tumors, particularly glioblastoma multiforme (GBM), harbor a small population of cancer stem cells (CSCs). These CSCs have the ability to undergo self-renewal, initiate tumors in vivo, and are resistant to chemotherapy and radiation therapy. The present study determined the spatial distribution of CSCs within the donated brains of two deceased patients affected by glioblastoma multiforme. The following six grossly visible functional regions were identified: Necrotic tumor, viable solid tumor, infiltrating tumor edge, peritumoral normal brain, normal brain close to the tumor and normal brain distant from the tumor. Each region was snap-frozen, sectioned and immunostained for the CSC biomarkers prominin-1 (CD133) and sex-determining region Y-box 2 (SOX2). The percentages of CD133⁺ and SOX2⁺ cells within each region were determined. Different percentages of CD133⁺ and SOX2⁺ cells were identified in different regions. Significantly higher percentages of CD133⁺ and SOX2⁺ cells were indicated at the infiltrating tumor edge when compared with other areas. In summary, the spatial distributions of CSCs in these two brains with glioblastoma multiforme were similar, with the highest concentration being at the infiltrating tumor edge. This suggests that the edge of the tumor is the moving front for tumor progression and invasion, and should be targeted for therapeutic intervention.

Effects of NOTCH1 signaling inhibitor γ-secretase inhibitor II on growth of cancer stem cells

The present study aimed to observe the effect of the Notch1 signaling inhibitor γ-secretase inhibitor II (GSI II) on the growth and differentiation of tumor cells. The tumor cell line U87 was grown in serum-free media, and cell growth was evaluated using immunofluorescence. Single-cell wall-adherent growing conditions were prepared, GSI II was added, and the differentiation and growth of single tumor cells was evaluated. Immunofluorescence demonstrated positive results for the expression of Nestin and cluster of differentiation 133. The cell proliferation rate was reduced following the addition of GSI II (P<0.05). GSI II may significantly inhibit the proliferation and differentiation of U87 tumor stem cells.

The Pluripotent Stem-Cell Marker Alkaline Phosphatase is Highly Expressed in Refractory Glioblastoma with DNA Hypomethylation

Background

Hypomethylation of genomic DNA induces stem-cell properties in cancer cells and contributes to the treatment resistance of various malignancies.

Objective

To examine the correlation between the methylation status of stem-cell-related genes and the treatment outcomes in patients with glioblastoma (GBM).

Methods

The genome-wide DNA methylation status was determined using HumanMethylation450 BeadChips, and the methylation status was compared between a group of patients with good prognosis (survival > 4 yr) and a group with poor prognosis (survival < 1 yr). Immunohistochemistry for proteins translated from hypomethylated genes, including alkaline phosphatase (ALPL), CD133, and CD44, was performed in 70 GBMs and 60 oligodendroglial tumors.

Results

The genomic DNA in refractory GBM was more hypomethylated than in GBM from patients with relatively long survival (P = .0111). Stem-cell-related genes including ALPL, CD133, and CD44 were also significantly hypomethylated. A validation study using immunohistochemistry showed that DNA hypomethylation was strongly correlated with high protein expression of ALPL, CD133, and CD44. GBM patients with short survival showed high expression of these stem-cell markers. Multivariate analysis confirmed that co-expression of ALPL + CD133 or ALPL + CD44 was a strong predictor of short survival. Anaplastic oligodendroglial tumors without isocitrate dehydrogenase 1 mutation were significantly correlated with high ALPL expression and poor survival.

Conclusion

Accumulation of stem-cell properties due to aberrant DNA hypomethylation is associated with the refractory nature of GBM.

Intratumoral heterogeneity: pathways to treatment resistance and relapse in human glioblastoma

Intratumoral heterogeneity (ITH) has increasingly being described for multiple cancers as the root cause of therapy resistance. Recent studies have started to explore the scope of ITH in glioblastoma (GBM), a highly aggressive and fatal form of brain tumor, to explain its inevitable therapy resistance and disease relapse. In this review, we detail the emerging data that explores the extensive genetic, cellular and functional ITH present in GBM. We discuss current experimental models of human GBM recurrence and suggest harnessing new technologies (CRISPR-Cas9 screening, CyTOF, cellular barcoding, single cell analysis) to delineate GBM ITH and identify treatment-refractory cell populations, thus opening new therapeutic windows. We will also explore why current therapeutics have failed in clinical trials and how ITH can inform us on developing empiric therapies for the treatment of recurrent GBM.

Large Scale Identification of Variant Proteins in Glioma Stem Cells

Glioblastoma (GBM), the most malignant of primary brain tumors, is a devastating and deadly disease, with a median survival of 14 months from diagnosis, despite standard regimens of radical brain tumor surgery, maximal safe radiation, and concomitant chemotherapy. GBM tumors nearly always re-emerge after initial treatment and frequently display resistance to current treatments. One theory that may explain GBM re-emergence is the existence of glioma stemlike cells (GSCs). We sought to identify variant protein features expressed in low passage GSCs derived from patient tumors. To this end, we developed a proteomic database that reflected variant and nonvariant sequences in the human proteome, and applied a novel retrograde proteomic workflow, to identify and validate the expression of 126 protein variants in 33 glioma stem cell strains. These newly identified proteins may harbor a subset of novel protein targets for future development of GBM therapy.

Combined Proteomic-Molecular Epidemiology Approach to Identify Precision Targets in Brain Cancer

Primary brain tumors are predominantly malignant gliomas. Grade IV astrocytomas (glioblastomas, GBM) are among the most deadly of all tumors; most patients will succumb to their disease within 2 years of diagnosis despite standard of care. The grim outlook for brain tumor patients indicates that novel precision therapeutic targets must be identified. Our hypothesis is that the cancer proteomes of glioma tumors may contain protein variants that are linked to the aggressive pathology of the disease. To this end, we devised a novel workflow that combined variant proteomics with molecular epidemiological mining of public cancer data sets to identify 10 previously unrecognized variants linked to the risk of death in low grade glioma or GBM. We hypothesize that a subset of the protein variants may be successfully developed in the future as novel targets for malignant gliomas.

Therapeutic targeting of chemoresistant and recurrent glioblastoma stem cells with a proapoptotic variant of oncolytic herpes simplex virus

Temozolomide (TMZ) chemotherapy, in combination with maximal safe resection and radiotherapy, is the current standard of care for patients with glioblastoma (GBM). Despite this multimodal approach, GBM inevitably relapses primarily due to resistance to chemo-radiotherapy, and effective treatment is not available for recurrent disease. In this study we identified TMZ resistant patient-derived primary and previously treated recurrent GBM stem cells (GSC), and investigated the therapeutic activity of a pro-apoptotic variant of oHSV (oHSV-TRAIL) in vitro and in vivo. We show that oHSV-TRAIL modulates cell survival and MAP Kinase proliferation signaling pathways as well as DNA damage response pathways in both primary and recurrent TMZ-resistant GSC. Utilizing real time in vivo imaging and correlative immunohistochemistry, we show that oHSV-TRAIL potently inhibits tumor growth and extends survival of mice bearing TMZ-insensitive recurrent intracerebral GSC tumors via robust and selective induction of apoptosis-mediated death in tumor cells, resulting in cures in 40% of the treated mice. In comparison, the anti-tumor effects in a primary chemoresistant GSC GBM model exhibiting a highly invasive phenotype were significant but less prominent. This work thus demonstrates the ability of oHSV-TRAIL to overcome the therapeutic resistance and recurrence of GBM, and provides a basis for its testing in a GBM clinical trial.

A molecular view of the radioresistance of gliomas

Gliomas originate from glial cells and are the most frequent primary brain tumors. High-grade gliomas occur ∼4 times more frequently than low-grade gliomas, are highly malignant, and have extremely poor prognosis. Radiotherapy, sometimes combined with chemotherapy, is considered the treatment of choice for gliomas and is used after resective surgery. Despite great technological improvements, the radiotherapeutic effect is generally limited, due to the marked radioresistance exhibited by gliomas cells, especially glioma stem cells (GSCs). The mechanisms underlying this phenomenon are multiple and remain to be fully elucidated. This review attempts to summarize current knowledge on the molecular basis of glioma radioresistance by focusing on signaling pathways, microRNAs, hypoxia, the brain microenvironment, and GSCs. A thorough understanding of the complex interactions between molecular, cellular, and environmental factors should provide new insight into the intrinsic radioresistance of gliomas, potentially enabling improvement, through novel concurrent therapies, of the clinical efficacy of radiotherapy.

Radiotherapy and Glioma Stem Cells: Searching for Chinks in Cellular Armor

Purpose of the review

Radiation became a pillar of oncologic treatment in the last century and provided a powerful and effective locoregional treatment of solid malignancies. After achieving some of the first cures in lymphomas and skin cancers, it assumed a key role in curative treatment of epithelioid malignancies. Despite success across a variety of histologic types, glioblastoma (GBM), the most common primary brain tumor afflicting adults, remains ultimately resistant to current radiation strategies. While GBMs demonstrate an initial response, recurrence is essentially universal and fatal, and typically reoccur in the areas that received the most intense radiation.

Recent Findings

Glioma stem cells (GSCs), a subpopulation of tumor cells with expression profiles similar to neural stem cells and marked self-renewal capacities, have been shown to drive tumor recurrence and preclude curative radiotherapy. Recent research has shown that these cells have enhanced DNA repair capacity, elevated resistance to cytotoxic ion fluxes and escape multi-modality therapies.

Summary

We will analyze the current understanding of GSCs and radiation by highlighting key discoveries probing their ability to withstand radiotherapy. We then speculate on novel mechanisms by which GSC can be made sensitive to or specifically targeted by radiation therapy.

Rad51 Degradation: Role in Oncolytic Virus-Poly(ADP-Ribose) Polymerase Inhibitor Combination Therapy in Glioblastoma

Background

Clinical success of poly(ADP-ribose) polymerase inhibitors (PARP i ) has been limited to repair-deficient cancers and by resistance. Oncolytic herpes simplex viruses (oHSVs) selectively kill cancer cells, irrespective of mutation, and manipulate DNA damage responses (DDR). Here, we explore potential synthetic lethal-like interactions between oHSV and PARP i .

Methods

The efficacy of combining PARP i , oHSV MG18L, and G47Δ in killing patient-derived glioblastoma stem cells (GSCs) was assessed using cell viability assays and Chou-Talalay synergy analysis. Effects on DDR pathways, apoptosis, and cell cycle after manipulation with pharmacological inhibitors and lentivirus-mediated knockdown or overexpression were examined by immunoblotting and FACS. In vivo efficacy was evaluated in two GSC-derived orthotopic xenograft models (n = 7-8 per group). All statistical tests were two-sided.

Results

GSCs are differentially sensitive to PARP i despite uniform inhibition of PARP activity. oHSV sensitized GSCs to PARP i , irrespective of their PARP i sensitivity through selective proteasomal degradation of key DDR proteins; Rad51, mediating the combination effects; and Chk1. Rad51 degradation required HSV DNA replication. This synthetic lethal-like interaction increased DNA damage, apoptosis, and cell death in vitro and in vivo. Combined treatment of mice bearing PARP i -sensitive or -resistant GSC-derived brain tumors greatly extended median survival compared to either agent alone (vs olaparib: P ≤.001; vs MG18L: P  = .005; median survival for sensitive of 83 [95% CI = 77 to 86], 94 [95% CI = 75 to 107], 102 [95% CI = 85 to 110], and 131 [95% CI = 108 to 170] days and for resistant of 54 [95% CI = 52 to 58], 56 [95% CI = 52 to 61], 62 [95% CI = 56 to 72], and 75 [95% CI = 64 to 90] days for mock, PARPi, oHSV, and combination, respectively).

Conclusions

The unique oHSV property to target multiple components of DDR generates cancer selective sensitivity to PARP i . This combination of oHSV with PARP i is a new anticancer strategy that overcomes the clinical barriers of PARP i resistance and DNA repair proficiency and is applicable not only to glioblastoma, an invariably lethal tumor, but also to other tumor types.

Glucose metabolism-targeted therapy and withaferin A are effective for epidermal growth factor receptor tyrosine kinase inhibitor-induced drug-tolerant persisters

In pathway‐targeted cancer drug therapies, the relatively rapid emergence of drug‐tolerant persisters (DTPs) substantially limits the overall therapeutic benefit. However, little is known about the roles of DTPs in drug resistance. In this study, we investigated the features of epidermal growth factor receptor–tyrosine kinase inhibitor‐induced DTPs and explored a new treatment strategy to overcome the emergence of these DTPs. We used two EGFR‐mutated lung adenocarcinoma cell lines, PC9 and II‐18. They were treated with 2 μM gefitinib for 6, 12, or 24 days or 6 months. We analyzed the mRNA expression of the stem cell‐related markers by quantitative RT‐PCR and the expression of the cellular senescence‐associated proteins. Then we sorted DTPs according to the expression pattern of CD133 and analyzed the features of sorted cells. Finally, we tried to ablate DTPs by glucose metabolism targeting therapies and a stem‐like cell targeting drug, withaferin A. Drug‐tolerant persisters were composed of at least two types of cells, one with the properties of cancer stem‐like cells (CSCs) and the other with the properties of therapy‐induced senescent (TIS) cells. The CD133^high cell population had CSC properties and the CD133^low cell population had TIS properties. The CD133^low cell population containing TIS cells showed a senescence‐associated secretory phenotype that supported the emergence of the CD133^high cell population containing CSCs. Glucose metabolism inhibitors effectively eliminated the CD133^low cell population. Withaferin A effectively eliminated the CD133^high cell population. The combination of phloretin and withaferin A effectively suppressed gefitinib‐resistant tumor growth.

Adaptive Chromatin Remodeling Drives Glioblastoma Stem Cell Plasticity and Drug Tolerance

Glioblastoma, the most common and aggressive malignant brain tumor, is propagated by stem-like cancer cells refractory to existing therapies. Understanding the molecular mechanisms that control glioblastoma stem cell (GSC) proliferation and drug resistance may reveal opportunities for therapeutic interventions. Here we show that GSCs can reversibly transition to a slow-cycling, persistent state in response to targeted kinase inhibitors. In this state, GSCs upregulate primitive developmental programs and are dependent upon Notch signaling. This transition is accompanied by widespread redistribution of repressive histone methylation. Accordingly, persister GSCs upregulate, and are dependent on, the histone demethylases KDM6A/B. Slow-cycling cells with high Notch activity and histone demethylase expression are present in primary glioblastomas before treatment, potentially contributing to relapse. Our findings illustrate how cancer cells may hijack aspects of native developmental programs for deranged proliferation, adaptation, and tolerance. They also suggest strategies for eliminating refractory tumor cells by targeting epigenetic and developmental pathways.

Network Plasticity and Intraoperative Mapping for Personalized Multimodal Management of Diffuse Low-Grade Gliomas

Gliomas are the most frequent primary brain tumors and include a variety of different histological tumor types and malignancy grades. Recent achievements in terms of molecular and imaging fields have created an unprecedented opportunity to perform a comprehensive interdisciplinary assessment of the glioma pathophysiology, with direct implications in terms of the medical and surgical treatment strategies available for patients. The current paradigm shift considers glioma management in a comprehensive perspective that takes into account the intricate connectivity of the cerebral networks. This allowed significant improvement in the outcome of patients with lesions previously considered inoperable. The current review summarizes the current theoretical framework integrating the adult human brain plasticity and functional reorganization within a dynamic individualized treatment strategy for patients affected by diffuse low-grade gliomas. The concept of neuro-oncology as a brain network surgery has major implications in terms of the clinical management and ensuing outcomes, as indexed by the increased survival and quality of life of patients managed using such an approach.

Targeting CD133 improves chemotherapeutic efficacy of recurrent pediatric pilocytic astrocytoma following prolonged chemotherapy

Background

Pilocytic astrocytomas (PAs) are the most common pediatric central nervous system neoplasms. In the majority of cases these tumors are benign and receive favorable prognosis following gross total surgical resection. In patients with progressive or symptomatic tumors, aggressive surgical resection is generally not feasible, thus radiation or chemotherapy are accepted initial or adjuvant interventions. Due to serious long-lasting side-effects, radiation is limited in young children; therefore, chemotherapy is widely practiced as an adjuvant treatment for these patients. However, chemotherapy can promote the emergence of multidrug resistant tumor cells that are more malignant than those of the original tumor. CD133, a putative stem cell marker in normal tissue and malignant brain tumors, enhances multidrug resistant gene 1 (MDR1) expression following chemotherapy in adult malignant glioblastomas. This study examines the relationship between CD133 and MDR1 in pediatric PAs exposed to chemotherapy, with the goal of identifying therapeutic targets that manifest as a result of chemotherapy.

Methods

Slides were obtained for 15 recurrent PAs, seven of which had received chemotherapy prior to surgical treatment for the recurrent tumor. These samples, as well as primary tumor tissue slides from the same patients were used to investigate CD133 and MDR1 expression via immunofluorescence. Archived frozen tissue samples from the same patients were used to examine CD133, MDR1 and PI3K-Akt-NF-κB signaling mediators, via western blot. Two drug resistant pediatric PA cell lines Res186 and Res199 were also used to evaluate the role of CD133 on cell response to cytotoxic therapy.

Results

CD133 and MDR1 were co-expressed and their expression was elevated in recurrent PAs from patients that had received chemotherapy, compared to patients that had not received chemotherapy. PI3K-Akt-NF-κB signaling mediator expression was also elevated in recurrent, chemotherapy-treated PA. Suppressing CD133 expression with siCD133 decreased levels of PI3K-Akt-NF-κB signaling mediators and MDR1, while increasing cell chemosensitivity, as indicated by quantification of apoptotic cells following chemotherapy.

Conclusions

CD133 contributes to multidrug resistance by regulating MDR1 levels via the PI3K-Akt-NF-κB signal pathway not only in adult glioblastomas, but also in pediatric PAs. Targeting CD133, adjuvant to conventional chemotherapy may improve outcomes for children with recurrent PA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0593-z) contains supplementary material, which is available to authorized users.

Glioblastoma Stem-Like Cells: Characteristics, Microenvironment, and Therapy

Glioblastoma multiforme (GBM), grade IV astrocytoma, is the most fatal malignant primary brain tumor. GBM contains functional subsets of cells called glioblastoma stem-like cells (GSCs), which are radioresistant and chemoresistant and eventually lead to tumor recurrence. Recent studies showed that GSCs reside in particular tumor niches that are necessary to support their behavior. To successfully eradicate GBM growth and recurrence, new strategies selectively targeting GSCs and/or their microenvironmental niche should be designed. In this regard, here we focus on elucidating the molecular mechanisms that govern these GSC properties and on understanding the mechanism of the microenvironmental signals within the tumor mass. Moreover, to overcome the blood–brain barrier, which represents a critical limitation of GBM treatments, a new drug delivery system should be developed. Nanoparticles can be easily modified by different methods to facilitate delivery efficiency of chemotherapeutics, to enhance the accumulation within the tumors, and to promote the capacity for targeting the GSCs. Therefore, nanotechnology has become the most promising approach to GSC-targeting therapy. Additionally, we discussed the future of nanotechnology-based targeted therapy and point out the disadvantages that should be overcome.

K+ channel signaling in irradiated tumor cells

K⁺ channels crosstalk with biochemical signaling cascades and regulate virtually all cellular processes by adjusting the intracellular K⁺ concentration, generating the membrane potential, mediating cell volume changes, contributing to Ca²⁺ signaling, and directly interacting within molecular complexes with membrane receptors and downstream effectors. Tumor cells exhibit aberrant expression and activity patterns of K⁺ channels. The upregulation of highly "oncogenic" K⁺ channels such as the Ca²⁺-activated IK channel may drive the neoplastic transformation, malignant progression, metastasis, or therapy resistance of tumor cells. In particular, ionizing radiation in doses used for fractionated radiotherapy in the clinic has been shown to activate K⁺ channels. Radiogenic K⁺ channel activity, in turn, contributes to the DNA damage response and promotes survival of the irradiated tumor cells. Tumor-specific overexpression of certain K⁺ channel types together with the fact that pharmacological K⁺ channel modulators are already in clinical use or well tolerated in clinical trials suggests that K⁺ channel targeting alone or in combination with radiotherapy might become a promising new strategy of anti-cancer therapy. The present article aims to review our current knowledge on K⁺ channel signaling in irradiated tumor cells. Moreover, it provides new data on molecular mechanisms of radiogenic K⁺ channel activation and downstream signaling events.

Cancer Stem Cell Hierarchy in Glioblastoma Multiforme

Glioblastoma multiforme (GBM), an aggressive tumor that typically exhibits treatment failure with high mortality rates, is associated with the presence of cancer stem cells (CSCs) within the tumor. CSCs possess the ability for perpetual self-renewal and proliferation, producing downstream progenitor cells that drive tumor growth. Studies of many cancer types have identified CSCs using specific markers, but it is still unclear as to where in the stem cell hierarchy these markers fall. This is compounded further by the presence of multiple GBM and glioblastoma cancer stem cell subtypes, making investigation and establishment of a universal treatment difficult. This review examines the current knowledge on the CSC markers SALL4, OCT-4, SOX2, STAT3, NANOG, c-Myc, KLF4, CD133, CD44, nestin, and glial fibrillary acidic protein, specifically focusing on their use and validity in GBM research and how they may be utilized for investigations into GBM's cancer biology.

A comprehensive profile of recurrent glioblastoma

In spite of relentless efforts to devise new treatment strategies, primary glioblastomas invariably recur as aggressive, therapy-resistant relapses and patients rapidly succumb to these tumors. Many therapeutic agents are first tested in clinical trials involving recurrent glioblastomas. Remarkably, however, fundamental knowledge on the biology of recurrent glioblastoma is just slowly emerging. Here, we review current knowledge on recurrent glioblastoma and ask whether and how therapies change intra-tumor heterogeneity, molecular traits and growth pattern of glioblastoma, and to which extent this information can be exploited for therapeutic decision-making. We conclude that the ability to characterize and predict therapy-induced changes in recurrent glioblastoma will determine, whether, one day, glioblastoma can be contained in a state of chronic disease.

Autologous transplantation of intestine-isolated glia cells improves neuropathology and restores cognitive deficits in β amyloid-induced neurodegeneration

Alzheimer's disease (AD) is characterized by chronic deposition of β-amyloid (Aβ) in the brain, progressive neurodegeneration and consequent cognitive and behavioral deficits that typify the disease. Astrocytes are pivotal in this process because they are activated in the attempt to digest Aβ which starts a neuroinflammatory response that further contributes to neurodegeneration. The intestine is a good source of astrocytes-like cells-referred to as enteric glial cells (EGCs). Here we show that the autologous transplantation of EGCs into the brain of Aβ-injected rats arrested the development of the disease after their engraftment. Transplanted EGCs showed anti-amyloidogenic activity, embanked Aβ-induced neuroinflammation and neurodegeneration, and released neutrophic factors. The overall result was the amelioration of the pathological hallmarks and the cognitive and behavioral deficits typical of Aβ-associated disease. Our data indicate that autologous EGCs transplantation may provide an efficient alternative for applications in cell-replacement therapies to treat neurodegeneration in AD.