Development of a Sox2 reporter system modeling cellular heterogeneity in glioma

CRISPR/Cas9-Mediated Gene Therapy for Glioblastoma: A Scoping Review

This scoping review examines the use of CRISPR/Cas9 gene editing in glioblastoma (GBM), a predominant and aggressive brain tumor. Categorizing gene targets into distinct groups, this review explores their roles in cell cycle regulation, microenvironmental dynamics, interphase processes, and therapy resistance reduction. The complexity of CRISPR-Cas9 applications in GBM research is highlighted, providing unique insights into apoptosis, cell proliferation, and immune responses within the tumor microenvironment. The studies challenge conventional perspectives on specific genes, emphasizing the potential therapeutic implications of manipulating key molecular players in cell cycle dynamics. Exploring CRISPR/Cas9 gene therapy in GBMs yields significant insights into the regulation of cellular processes, spanning cell interphase, renewal, and migration. Researchers, by precisely targeting specific genes, uncover the molecular orchestration governing cell proliferation, growth, and differentiation during critical phases of the cell cycle. The findings underscore the potential of CRISPR/Cas9 technology in unraveling the complex dynamics of the GBM microenvironment, offering promising avenues for targeted therapies to curb GBM growth. This review also outlines studies addressing therapy resistance in GBM, employing CRISPR/Cas9 to target genes associated with chemotherapy resistance, showcasing its transformative potential in effective GBM treatments.

Progresses, Challenges, and Prospects of CRISPR/Cas9 Gene-Editing in Glioma Studies

Glioma refers to a tumor that is derived from brain glial stem cells or progenitor cells and is the most common primary intracranial tumor. Due to its complex cellular components, as well as the aggressiveness and specificity of the pathogenic site of glioma, most patients with malignant glioma have poor prognoses following surgeries, radiotherapies, and chemotherapies. In recent years, an increasing amount of research has focused on the use of CRISPR/Cas9 gene-editing technology in the treatment of glioma. As an emerging gene-editing technology, CRISPR/Cas9 utilizes the expression of certain functional proteins to repair tissues or treat gene-deficient diseases and could be applied to immunotherapies through the expression of antigens, antibodies, or receptors. In addition, some research also utilized CRISPR/Cas9 to establish tumor models so as to study tumor pathogenesis and screen tumor prognostic targets. This paper mainly discusses the roles of CRISPR/Cas9 in the treatment of glioma patients, the exploration of the pathogenesis of neuroglioma, and the screening targets for clinical prognosis. This paper also raises the future research prospects of CRISPR/Cas9 in glioma, as well as the opportunities and challenges that it will face in clinical treatment in the future.

Reporter gene systems for the identification and characterization of cancer stem cells

Cancer stem cells (CSCs) are tumor cells that share functional characteristics with normal and embryonic stem cells. CSCs have increased tumor-initiating capacity and metastatic potential and lower sensitivity to chemo- and radiotherapy, with important roles in tumor progression and the response to therapy. Thus, a current goal of cancer research is to eliminate CSCs, necessitating an adequate phenotypic and functional characterization of CSCs. Strategies have been developed to identify, enrich, and track CSCs, many of which distinguish CSCs by evaluating the expression of surface markers, the initiation of specific signaling pathways, and the activation of master transcription factors that control stemness in normal cells. We review and discuss the use of reporter gene systems for identifying CSCs. Reporters that are under the control of aldehyde dehydrogenase 1A1, CD133, Notch, Nanog homeobox, Sex-determining region Y-box 2, and POU class 5 homeobox can be used to identify CSCs in many tumor types, track cells in real time, and screen for drugs. Thus, reporter gene systems, in combination with in vitro and in vivo functional assays, can assess changes in the CSCs pool. We present relevant examples of these systems in the evaluation of experimental CSCs-targeting therapeutics, demonstrating their value in CSCs research.

The evolution of the cancer stem cell state in glioblastoma: emerging insights into the next generation of functional interactions

Cellular heterogeneity is a hallmark of advanced cancers and has been ascribed in part to a population of self-renewing, therapeutically resistant cancer stem cells (CSCs). Glioblastoma (GBM), the most common primary malignant brain tumor, has served as a platform for the study of CSCs. In addition to illustrating the complexities of CSC biology, these investigations have led to a deeper understanding of GBM pathogenesis, revealed novel therapeutic targets, and driven innovation towards the development of next-generation therapies. While there continues to be an expansion in our knowledge of how CSCs contribute to GBM progression, opportunities have emerged to revisit this conceptual framework. In this review, we will summarize the current state of CSCs in GBM using key concepts of evolution as a paradigm (variation, inheritance, selection, and time) to describe how the CSC state is subject to alterations of cell intrinsic and extrinsic interactions that shape their evolutionarily trajectory. We identify emerging areas for future consideration, including appreciating CSCs as a cell state that is subject to plasticity, as opposed to a discrete population. These future considerations will not only have an impact on our understanding of this ever-expanding field but will also provide an opportunity to inform future therapies to effectively treat this complex and devastating disease.

A Novel Six-mRNA Signature Predicts Survival of Patients With Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a devastating brain tumor and displays divergent clinical outcomes due to its high degree of heterogeneity. Reliable prognostic biomarkers are urgently needed for improving risk stratification and survival prediction. In this study, we analyzed genome-wide mRNA profiles in GBM patients derived from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases to identify mRNA-based signatures for GBM prognosis with survival analysis. Univariate Cox regression model was used to evaluate the relationship between the expression of mRNA and the prognosis of patients with GBM. We established a risk score model that consisted of six mRNA (AACS, STEAP1, STEAP2, G6PC3, FKBP9, and LOXL1) by the LASSO regression method. The six-mRNA signature could divide patients into a high-risk and a low-risk group with significantly different survival rates in training and test sets. Multivariate Cox regression analysis confirmed that it was an independent prognostic factor in GBM patients, and it has a superior predictive power as compared with age, IDH mutation status, MGMT, and G-CIMP methylation status. By combining this signature and clinical risk factors, a nomogram can be established to predict 1-, 2-, and 3-year OS in GBM patients with relatively high accuracy.

Glioma stem cells and their roles within the hypoxic tumor microenvironment

Tumor microenvironments are the result of cellular alterations in cancer that support unrestricted growth and proliferation and result in further modifications in cell behavior, which are critical for tumor progression. Angiogenesis and therapeutic resistance are known to be modulated by hypoxia and other tumor microenvironments, such as acidic stress, both of which are core features of the glioblastoma microenvironment. Hypoxia has also been shown to promote a stem-like state in both non-neoplastic and tumor cells. In glial tumors, glioma stem cells (GSCs) are central in tumor growth, angiogenesis, and therapeutic resistance, and further investigation of the interplay between tumor microenvironments and GSCs is critical to the search for better treatment options for glioblastoma. Accordingly, we summarize the impact of hypoxia and acidic stress on GSC signaling and biologic phenotypes, and potential methods to inhibit these pathways.

SOX2 Expression and Transcriptional Activity Identifies a Subpopulation of Cancer Stem Cells in Sarcoma with Prognostic Implications

Stemness in sarcomas is coordinated by the expression of pluripotency factors, like SOX2, in cancer stem cells (CSC). The role of SOX2 in tumor initiation and progression has been well characterized in osteosarcoma. However, the pro-tumorigenic features of SOX2 have been scarcely investigated in other sarcoma subtypes. Here, we show that SOX2 depletion dramatically reduced the ability of undifferentiated pleomorphic sarcoma (UPS) cells to form tumorspheres and to initiate tumor growth. Conversely, SOX2 overexpression resulted in increased in vivo tumorigenicity. Moreover, using a reporter system (SORE6) which allows to monitor viable cells expressing SOX2 and/or OCT4, we found that SORE6+ cells were significantly more tumorigenic than the SORE6- subpopulation. In agreement with this findings, SOX2 expression in sarcoma patients was associated to tumor grade, differentiation, invasive potential and lower patient survival. Finally, we studied the effect of a panel of anti-tumor drugs on the SORE6+ cells of the UPS model and patient-derived chondrosarcoma lines. We found that the mithramycin analogue EC-8042 was the most efficient in reducing SORE6+ cells in vitro and in vivo. Overall, this study demonstrates that SOX2 is a pro-tumorigenic factor with prognostic potential in sarcoma. Moreover, SORE6 transcriptional activity is a bona fide CSC marker in sarcoma and constitutes an excellent biomarker for evaluating the efficacy of anti-tumor treatments on CSC subpopulations.

Transgenic models for investigating the nervous system: Currently available neurofluorescent reporters and potential neuronal markers

Recombinant DNA technologies have enabled the development of transgenic animal models for use in studying a myriad of diseases and biological states. By placing fluorescent reporters under the direct regulation of the promoter region of specific marker proteins, these models can localize and characterize very specific cell types. One important application of transgenic species is the study of the cytoarchitecture of the nervous system. Neurofluorescent reporters can be used to study the structural patterns of nerves in the central or peripheral nervous system in vivo, as well as phenomena involving embryologic or adult neurogenesis, injury, degeneration, and recovery. Furthermore, crucial molecular factors can also be screened via the transgenic approach, which may eventually play a major role in the development of therapeutic strategies against diseases like Alzheimer's or Parkinson's. This review describes currently available reporters and their uses in the literature as well as potential neural markers that can be leveraged to create additional, robust transgenic models for future studies.

Tunneling nanotubes: A bridge for heterogeneity in glioblastoma and a new therapeutic target?

BACKGROUND

The concept of tumour heterogeneity is not novel but is fast becoming a paradigm by which to explain part of the highly recalcitrant nature of aggressive malignant tumours. Glioblastoma is a prime example of such difficult-to-treat, invasive, and incurable malignancies. With the advent of the post-genomic age and increased access to next-generation sequencing technologies, numerous publications have described the presence and extent of intratumoural and intertumoural heterogeneity present in glioblastoma. Moreover, there have been numerous reports more directly correlating the heterogeneity of glioblastoma to its refractory, reoccurring, and inevitably terminal nature. It is therefore prudent to consider the different forms of heterogeneity seen in glioblastoma and how to harness this understanding to better strategize novel therapeutic approaches. One of the most central questions of tumour heterogeneity is how these numerous different cell types (both tumour and non-tumour) in the tumour mass communicate.

RECENT FINDINGS

This chapter provides a brief review on the variable heterogeneity of glioblastoma, with a focus on cellular heterogeneity and on modalities of communication that can induce further molecular diversity within the complex and ever-evolving tumour microenvironment. We provide particular emphasis on the emerging role of actin-based cellular conduits called tunnelling nanotubes (TNTs) and tumour microtubes (TMs) and outline the perceived current problems in the field that need to be resolved before pharmacological targeting of TNTs can become a reality.

CONCLUSIONS

We conclude that TNTs and TMs provide a new and exciting avenue for the therapeutic targeting of glioblastoma and that numerous inroads have already made into TNT and TM biology. However, to target TMs and TNTs, several advances must be made before this aim can become a reality.

Diagnostic and prognostic value of microRNA-193b in patients with glioma and its effect on tumor progression

Emerging evidence has indicated the important roles of microRNAs (miRs) in the pathogenesis of cancer in humans. The present study sought to assess the expression patterns of miR-193b in patients with glioma, and investigated its clinical significance and biological function in this disease. The expression of miR-193b in the serum, tissues and cells of patients with glioma was analyzed using reverse transcription-quantitative PCR. Its diagnostic value was evaluated using the receiver operating characteristic (ROC) curve analysis, and its prognostic value was analyzed using Kaplan-Meier survival and Cox regression analyses. Experiments on glioma cells were conducted to explore the influence of miR-193b on proliferation, migration and invasion. Increased expression of miR-193b was observed in serum, tissues and cells of patients with glioma compared with the corresponding controls (all P<0.05). miR-193b expression was associated with the World Health Organization grading and the Karnofsky Performance Scale of the patients (all P<0.05). The area under the curve of the ROC analysis of miR-193b was 0.903, indicating its high diagnostic accuracy for glioma. High expression of miR-193b was associated with poor overall survival rate in patients (P=0.002). Therefore, miR-193b is a potential independent prognostic factor in glioma. Furthermore, the overexpression of this miR in glioma cells led to increased proliferation, migration and invasion, whereas its inhibition resulted in the opposite effects on these cell behaviors (all P<0.05). Thus, the findings from the present study indicate that the overexpression of miR-193b serves as a useful biomarker for the diagnosis and prediction of prognosis in glioma. The upregulation of miR-193b expression may enhance glioma progression, and may therefore be a potential target for glioma therapy.

MicroRNA 145 enhances chemosensitivity of glioblastoma stem cells to demethoxycurcumin

Background: The presence of glioma stem cells (GSCs) is thought to be a key factor responsible for development of the incurable glioblastoma multiforme (GBM). GSCs are often displayed during chemotherapy resistance, except for demethoxycurcumin (DMC), a component of curcumin, which has been previously confirmed to inhibit GSCs proliferation and induce apoptosis.

Purpose: The objective of this study was to identify the main mechanism underlying anti-GSCs resistance by DMC.

Patients and methods: qRT-PCR was used to determine the expression of miR-145 in glioma patients and GSCs, and GSCs were transfected with miR-145 overexpressed vectors. Then, functional analyses (in vitro and in vivo) were performed to confirm the role of miR-145 and DMC in GSCs. Finally, related proteins were tested by immunohistochemistry and Western blot.

Results: miR-145 was atypically low-expressed miRNA in GSCs, and could enhance GSC chemosensitivity to DMC both in vitro and in vivo. Upregulation of miR-145 in GSCs resulted in increased cell growth inhibition and apoptosis to DMC. Further research on the mechanism demonstrated that the combined effects of miR-145 and DMC were involved in the miR-145/SOX2-Wnt/β-catenin pathway. Overexpression of SOX2 reduced GSC resistance to growth inhibition by miR-145+ DMC treatment.

Conclusion: Our data strongly support an important role for miR-145 in enhancing GSC chemosensitivity to DMC by targeting the SOX2-Wnt/β-catenin axis.

GBM heterogeneity as a function of variable epidermal growth factor receptor variant III activity

Abnormal activation of the epidermal growth factor receptor (EGFR) due to a deletion of exons 2-7 of EGFR (EGFRvIII) is a common alteration in glioblastoma (GBM). While this alteration can drive gliomagenesis, tumors harboring EGFRvIII are heterogeneous. To investigate the role for EGFRvIII activation in tumor phenotype we used a neural progenitor cell-based murine model of GBM driven by EGFR signaling and generated tumor progenitor cells with high and low EGFRvIII activation, pEGFR^Hi and pEGFR^Lo. In vivo, ex vivo, and in vitro studies suggested a direct association between EGFRvIII activity and increased tumor cell proliferation, decreased tumor cell adhesion to the extracellular matrix, and altered progenitor cell phenotype. Time-lapse confocal imaging of tumor cells in brain slice cultures demonstrated blood vessel co-option by tumor cells and highlighted differences in invasive pattern. Inhibition of EGFR signaling in pEGFR^Hi promoted cell differentiation and increased cell-matrix adhesion. Conversely, increased EGFRvIII activation in pEGFR^Lo reduced cell-matrix adhesion. Our study using a murine model for GBM driven by a single genetic driver, suggests differences in EGFR activation contribute to tumor heterogeneity and aggressiveness.

DICER governs characteristics of glioma stem cells and the resulting tumors in xenograft mouse models of glioblastoma

The RNAse III endonuclease DICER is a key regulator of microRNA (miRNA) biogenesis and is frequently decreased in a variety of malignancies. We characterized the role of DICER in glioblastoma (GB), specifically demonstrating its effects on the ability of glioma stem-like cells (GSCs) to form tumors in a mouse model of GB. DICER silencing in GSCs reduced their stem cell characteristics, while tumors arising from these cells were more aggressive, larger in volume, and displayed a higher proliferation index and lineage differentiation. The resulting tumors, however, were more sensitive to radiation treatment. Our results demonstrate that DICER silencing enhances the tumorigenic potential of GSCs, providing a platform for analysis of specific relevant miRNAs and development of potentially novel therapies against GB.

Reporter Systems to Study Cancer Stem Cells

Cancer stem cells have been identified in primary tumors, patient derived xenografts, and established cancer cell lines. The development of reporters has enabled investigators to rapidly enrich for these cells and more importantly track these cells in real time. Here we describe the current state of the reporter field and their use and limitations in multiple cancers.

Cisplatin induces stemness in ovarian cancer

The mainstay of treatment for ovarian cancer is platinum-based cytotoxic chemotherapy. However, therapeutic resistance and recurrence is a common eventuality for nearly all ovarian cancer patients, resulting in poor median survival. Recurrence is postulated to be driven by a population of self-renewing, therapeutically resistant cancer stem cells (CSCs). A current limitation in CSC studies is the inability to interrogate their dynamic changes in real time. Here we utilized a GFP reporter driven by the NANOG-promoter to enrich and track ovarian CSCs. Using this approach, we identified a population of cells with CSC properties including enhanced expression of stem cell transcription factors, self-renewal, and tumor initiation. We also observed elevations in CSC properties in cisplatin-resistant ovarian cancer cells as compared to cisplatin-naïve ovarian cancer cells. CD49f, a marker for CSCs in other solid tumors, enriched CSCs in cisplatin-resistant and -naïve cells. NANOG-GFP enriched CSCs (GFP+ cells) were more resistant to cisplatin as compared to GFP-negative cells. Moreover, upon cisplatin treatment, the GFP signal intensity and NANOG expression increased in GFP-negative cells, indicating that cisplatin was able to induce the CSC state. Taken together, we describe a reporter-based strategy that allows for determination of the CSC state in real time and can be used to detect the induction of the CSC state upon cisplatin treatment. As cisplatin may provide an inductive stress for the stem cell state, future efforts should focus on combining cytotoxic chemotherapy with a CSC targeted therapy for greater clinical utility.

Overview of Cancer Stem Cells and Stemness for Community Oncologists

Advances in cancer research in the past have led to an evolving understanding of cancer pathogenesis and the development of novel drugs that significantly improve patient outcomes. However, many patients still encounter treatment resistance, recurrence, or metastasis and eventually die from progressing disease. Experimental evidence indicates that a subpopulation of cancer cells, called cancer stem cells (CSCs), possess "stemness" properties similar to normal stem cells, including self-renewal, differentiation, and proliferative potential. These stemness properties are lost during differentiation and are governed by pathways such as STAT3, NANOG, NOTCH, WNT, and HEDGEHOG, which are highly dysregulated in CSCs due to genetic and epigenetic changes. Promising results have been observed in preclinical models targeting these CSCs through the disruption of stemness pathways in combination with current treatment modalities. This has led to anti-CSC-based clinical trials in multiple stages of development. In this review, we discuss the role of CSCs and stemness pathways in cancer treatment and how they relate to clinical observations. Because CSCs and the stemness pathways governing them may explain the negative clinical outcomes observed during treatment, it is important for oncologists to understand how they contribute to cancer progression and how they may be targeted to improve patient outcomes.

Technological advances for interrogating the human kinome

There is increasing appreciation among researchers and clinicians of the value of investigating biology and pathobiology at the level of cellular kinase (kinome) activity. Kinome analysis provides valuable opportunity to gain insights into complex biology (including disease pathology), identify biomarkers of critical phenotypes (including disease prognosis and evaluation of therapeutic efficacy), and identify targets for therapeutic intervention through kinase inhibitors. The growing interest in kinome analysis has fueled efforts to develop and optimize technologies that enable characterization of phosphorylation-mediated signaling events in a cost-effective, high-throughput manner. In this review, we highlight recent advances to the central technologies currently available for kinome profiling and offer our perspectives on the key challenges remaining to be addressed.

Mechanistic Parameterization of the Kinomic Signal in Peptide Arrays

Kinases play a role in every cellular process involved in tumorigenesis ranging from proliferation, migration, and protein synthesis to DNA repair. While genetic sequencing has identified most kinases in the human genome, it does not describe the ‘kinome’ at the level of activity of kinases against their substrate targets. An attempt to address that limitation and give researchers a more direct view of cellular kinase activity is found in the PamGene PamChip® system, which records and compares the phosphorylation of 144 tyrosine or serine/threonine peptides as they are phosphorylated by cellular kinases. Accordingly, the kinetics of this time dependent kinomic signal needs to be well understood in order to transduce a parameter set into an accurate and meaningful mathematical model.

Here we report the analysis and mathematical modeling of kinomic time series, which achieves a more accurate description of the accumulation of phosphorylated product than the current model, which assumes first order enzyme-substrate kinetics. Reproducibility of the proposed solution was of particular attention. Specifically, the non-linear parameterization procedure is delivered as a public open source web application where kinomic time series can be accurately decomposed into the model’s two parameter values measuring phosphorylation rate and capacity. The ability to deliver model parameterization entirely as a client side web application is an important result on its own given increasing scientific preoccupation with reproducibility. There is also no need for a potentially transitory and opaque server-side component maintained by the authors, nor of exchanging potentially sensitive data as part of the model parameterization process since the code is transferred to the browser client where it can be inspected and executed.