Do relevant markers of cancer stem cells CD133 and Nestin indicate a poor prognosis in glioma patients? A systematic review and meta-analysis

The anti-vascular endothelial growth factor receptor-1 monoclonal antibody D16F7 inhibits invasiveness of human glioblastoma and glioblastoma stem cells

BACKGROUND

Glioblastoma (GBM) is a highly migratory, invasive, and angiogenic brain tumor. Like vascular endothelial growth factor-A (VEGF-A), placental growth factor (PlGF) promotes GBM angiogenesis. VEGF-A is a ligand for both VEGF receptor-1 (VEGFR-1) and VEGFR-2, while PlGF interacts exclusively with VEGFR-1. We recently generated the novel anti-VEGFR-1 monoclonal antibody (mAb) D16F7 that diminishes VEGFR-1 homodimerization/activation without affecting VEGF-A and PlGF binding.

METHODS

In the present study, we evaluated the expression of VEGFR-1 in human GBM tissue samples (n = 42) by immunohistochemistry, in cell lines (n = 6) and GBM stem cells (GSCs) (n = 18) by qRT-PCR and/or western blot analysis. In VEGFR-1 positive GBM or GSCs we also analyzed the ability of D16F7 to inhibit GBM invasiveness in response to VEGF-A and PlGF.

RESULTS

Most of GBM specimens stained positively for VEGFR-1 and all but one GBM cell lines expressed VEGFR-1. On the other hand, in GSCs the expression of the receptor was heterogeneous. D16F7 reduced migration and invasion of VEGFR-1 positive GBM cell lines and patient-derived GSCs in response to VEGF-A and PlGF. Interestingly, this effect was also observed in VEGFR-1 positive GSCs transfected to over-express wild-type EGFR (EGFRwt⁺) or mutant EGFR (ligand binding domain-deficient EGFRvIII⁺). Furthermore, D16F7 suppressed intracellular signal transduction in VEGFR-1 over-expressing GBM cells by reducing receptor auto-phosphorylation at tyrosine 1213 and downstream Erk1/2 activation induced by receptor ligands.

CONCLUSION

The results from this study suggest that VEGFR-1 is a relevant target for GBM therapy and that D16F7-derived humanized mAbs warrant further investigation.

CD133 in brain tumor: the prognostic factor

CD133 has been shown to be an important stem cell factor that promotes glioma progression. However, the mechanism for CD133-mediated glioma progression has yet to be fully elucidated. In this study, we found that CD133 mRNA expression was a prognostic marker in three independent glioma patient cohorts, corroborating a putative role for CD133 in glioma progression. Importantly, we found that CD133 expression in glioma was highly correlated with the expression of HOX gene stem cell factors (HOXA5, HOXA7, HOXA10, HOXC4 and HOXC6). The expression of these HOX genes individually was significantly associated with survival. Interestingly, the prognostic significance of CD133 was dependent on the expression level of HOX genes, and vice versa. CD133 (p = 0.021) and HOXA7 (p = 0.001) were independent prognostic markers when the three glioma patient cohorts were combined (n = 231). Our results suggest that HOX genes may play a more important role in progression of glioma when CD133 expression is low. Furthermore, we showed that low-level expression of LIM2 in CD133-high glioma was associated with poorer survival, suggesting that LIM2 could be a therapeutic target for glioma expressing a high level of CD133. Connectivity mapping identified vinblastine and vincristine as agents that could reverse the CD133/HOX genes/LIM2-signature, and we confirmed this by in vitro analysis in glioma cell lines, demonstrating that CD133 and HOX genes were co-expressed and could be downregulated by vincristine. In conclusion, our data show that CD133 and HOX genes are important prognostic markers in glioma and shed light on possible treatment strategies for glioma expressing a high level of CD133.

Can recurrences be predicted in craniopharyngiomas? β-catenin coexisting with stem cells markers and p-ATM in a clinicopathologic study of 45cases

Background

Recurrence is a common feature of craniopharyngiomas, benign tumors that origin from squamous epithelial remnants of Rathke’s pouch- arising at any segment of its whole course. There are two histotypes, showing different morphology and clinical behavior: adamantinomatous(adaCP) and papillary (papCP). An univocal strategy of management has not yet been defined, being considered the combination of surgery and radiotherapy the most effective, especially in case of incomplete resection. Therefore, the identification of factors influencing the biological and clinical behaviour is of paramount importance.

β-catenin is a cell-cell adhesion protein, whose nuclear localization has been linked to the pathogenesis of adaCP: its nuclear accumulation is associated to the presence of a tumor stem cell subpopulation. The latter is made of cells capable of self-renewal, hence believed to be responsible of recurrence, metastases and resistance to therapy in all tumors.

ATM is a kinase activated by autophosphorylation (p-ATM) upon DNA double-strand breaks. It is involved not only in DNA repair, but also in tumor migration and invasiveness. Its expression may have prognostic implications in many neoplastic diseases.

Methods

In this study, we measured the immunohistochemical expression of β-catenin, stem cell markers (CD133, CD166), Ki67 and pATMin 45 craniopharyngiomas and correlated it with clinicopathologic features.

Results

Statistical analysis revealed strong correlation of β-catenin with recurrence (p = 0.0039), Ki67 (p = 0.0011, r = 0.4903) and CD166 (p = 0.0002, r = 0.6218). A slight tendency to a higher expression of β-catenin was recorded for adaCP rather than papCP (p = 0.0895).Fisher’s exact test showed that CD166 was significantlyrelated with recurrence (p = 0.0040). Furthermore, cytoplasmic pATM was more expressed in adaCPs (p = 0.0470), compared to papCPs that displayed a more evident nuclear signal (p = 0.0313) instead.

Conclusions

Backing upon these data, we could weigh in on the need of identifying β-catenin and CD166 as prognostic markersthat could be useful in predicting thebiologicalbehavior, as recurrence risk incraniopharyngiomas. The final goal is to drew up a prognostic algorithm to be of aid in the planning of an appropriate treatment strategy. Furthermore, our findings demonstrate that pATM could be used as additional distinction-marker between the two histotypes.

Enhancing the Oncolytic Activity of CD133-Targeted Measles Virus: Receptor Extension or Chimerism with Vesicular Stomatitis Virus Are Most Effective

Therapy resistance and tumor recurrence are often linked to a small refractory and highly tumorigenic subpopulation of neoplastic cells, known as cancer stem cells (CSCs). A putative marker of CSCs is CD133 (prominin-1). We have previously described a CD133-targeted oncolytic measles virus (MV-CD133) as a promising approach to specifically eliminate CD133-positive tumor cells. Selectivity was introduced at the level of cell entry by an engineered MV hemagglutinin (H). The H protein was blinded for its native receptors and displayed a CD133-specific single-chain antibody fragment (scFv) as targeting domain. Interestingly, MV-CD133 was more active in killing CD133-positive tumors than the unmodified MV-NSe despite being highly selective for its target cells. To further enhance the antitumoral activity of MV-CD133, we here pursued arming technologies, receptor extension, and chimeras between MV-CD133 and vesicular stomatitis virus (VSV). All newly generated viruses including VSV-CD133 were highly selective in eliminating CD133-positive cells. MV-CD46/CD133 killed in addition CD133-negative cells being positive for the MV receptors. In an orthotopic glioma model, MV-CD46/CD133 and MV^SCD-CD133, which encodes the super cytosine deaminase, were most effective. Notably, VSV-CD133 caused fatal neurotoxicity in this tumor model. Use of CD133 as receptor could be excluded as being causative. In a subcutaneous tumor model of hepatocellular cancer, VSV-CD133 revealed the most potent oncolytic activity and also significantly prolonged survival of the mice when injected intravenously. Compared to MV-CD133, VSV-CD133 infected a more than 10⁴-fold larger area of the tumor within the same time period. Our data not only suggest new concepts and approaches toward enhancing the oncolytic activity of CD133-targeted oncolytic viruses but also raise awareness about careful toxicity testing of novel virus types.

LPS alters the immuno-phenotype of glioma and glioma stem-like cells and induces in vivo antitumor immunity via TLR4

BACKGROUND

This study examined the ability of lipopolysaccharide (LPS) to affect glioma and glioma stem-like cells (GSCs) in vitro and to induce antitumor immunity in vivo and the role of TLR4 in these processes.

METHODS

Using RT-PCR and immunohistochemistry, we examined the expression of TLR4 in 34 glioblastoma clinical samples. Using real time-PCR, western blot and ELISA analyses, the effect of LPS stimulation on the expression of immune related molecules was evaluated in RG2 and U87 GSCs. Control or LPS-pretreated RG2 GSCs were intracranially or subcutaneously implanted into wild-type or nude Fisher 344 rats. Histopathological examinations were used to assess tumor progression and immune infiltration and Kaplan-Meier analyses to compare survival times of the animal models.

RESULTS

TLR4 was highly expressed in glioblastoma clinical samples. In vitro LPS stimulation for 6 h significantly altered expression of immune related molecules in RG2 and U87 GSCs. However, prolonged LPS stimulation diminished this effect. Rats inoculated intracranially with LPS-pretreated RG2 GSCs survived significantly longer than rats inoculated with control RG2 GSCs. In vivo, LPS-pretreated RG2 GSCs expressed higher levels of MHC molecules, CXCL10 and TNF-α and recruited more CD8⁺ lymphocytes. However, intratumoral LPS treatment was not equally beneficial. Furthermore, the in vitro and in vivo effects of LPS stimulation appeared to be largely TLR4-dependent.

CONCLUSION

LPS pretreatment promotes the recognition and eradication of tumor GSCs in vivo when the immune function of the tumor-bearing host is intact. In addition, our data indicate a complex relationship between bacterial infection and glioma prognosis.

CD147 and glioma: a meta-analysis

Gliomas are the most common primary brain tumors. This meta-analysis aimed to systematically evaluate the relationship between CD147 expression in tissues and the clinicopathological features of patients with glioma. We searched PubMed (1966-2016), EMBASE (1980-2016), Cochrane Library (1996-2016), Web of Science (1945-2016), China National Knowledge Infrastructure (1982-2016), and Wan Fang databases (1988-2016). Quality assessment of the literature was performed using the Newcastle-Ottawa Scale, with Revman 5.3 and Stata 14.0 for analysis. In total, 1806 glioma patients from 19 studies were included, and patients with CD147 overexpression had poorer overall survival [hazard ratio (HR) = 2.211, P < 0.0001], a higher risk of recurrence (HR = 2.20, P = 0.0025), and a lower 5-year survival rate [odds ratio (OR) 0.12; 95% CI 0.08-0.19; P < 0.00001]. We observed significant differences in CD147 expression when comparing glioma tissues versus non-cancerous brain tissues (OR 20.42; 95% CI 13.94-29.91; P < 0.00001), tumor grades III-IV versus grades I-II (OR 5.88, 95% CI 4.15-8.34; P < 0.00001), and large versus small tumors (OR 1.58, 95% CI 1.04-2.40; P = 0.03). We also observed a significant correlation with matrix metalloproteinase (MMP) 2 (OR 39.11, 95% CI 11.47-133.34; P < 0.00001) and MMP9 (OR 13.35, 95% CI 4.67-38.18; P < 0.00001). CD147 expression did not differ based on patient's age (young vs. old, P = 0.89) or gender (female vs. male, P = 0.57). CD147 expression may be a potential prognostic biomarker for poorer overall and relapse-free survival, and may affect the 5-year survival rate in glioma patients. CD147 expression is also closely correlated with poor clinical characteristics in glioma patients.

Overexpression of leptin receptor in human glioblastoma: Correlation with vasculogenic mimicry and poor prognosis

Vasculogenic mimicry (VM) was an important tumor blood supply to complement the endothelial cell-dependent angiogenesis, while leptin and receptor (ObR) involved in angiogenesis in glioblastoma has been reported on previous study, but the relationship between ObR expression and VM formation in human glioblastoma tissues, as well as their prognostic significance still remains unclear. In our study, we found that VM recognized by CD31-/PAS+ immunohistochemical staining in glioblastoma tissues showed a positive correlation with leptin expression (r = 0.58, P < 0.01), as well as ObR expression in glioblastoma tissues (r = 0.61, P < 0.01). Association of glial to mesenchymal transition (GMT)-related molecular with ObR expression and VM formation in glioblastoma tissues indicated that ObR-positive glioblastoma cells with GMT phenotype might be more likely to constitute VM, and co-expression of ObR and CD133 or Nestin to constitute the channel impliated that ObR-positive glioblastoma cells displayed glioblastoma stem cells (GSC) properties. Moreover, Kaplan-Meier statistical analysis showed that patients with more VM or ObR expression displayed poorer prognosis for overall survival times than patients with less expression (VM^high vs. VM^low: P = 0.033; ObR^high vs. ObR^low: P = 0.009). And ObR+ glioblastoma cells with GSC characteristic were mostly involved in VM formation, whereas a little part of cells were also related to microvascular density (MVD), which suggested that ObR was an important target for anticancer therapy, so further related studies were needed to improve glioblastoma treatment.

Nestin servers as a promising prognostic biomarker in non-small cell lung cancer

Lung cancer is currently the leading cause of cancer-related death worldwide and it is important to identify the predictive and/or prognostic markers for the cancer. Nestin, a proliferative and multipotent biomarker has been reported to be associated with prognosis in non-small cell lung cancer (NSCLC) in a few studies. In the present study, we retrospectively recruited 153 patients with NSCLC. Nestin protein expression in tumor samples was determined by immunohistochemistry staining. Nestin expression was related with tumor differentiation (P=0.036), lymphatic metastasis (N stage, P=0.011), and p-TNM stage (P=0.013), while there was no significant association between Nestin expression level and age, smoking habits, gender, histologic type, and T stage. Nestin was an independent prognostic factor for overall survival in NSCLC with an adjusted hazard ratio of 2.701 (95% CI, 1.616-4.513, P<0.001) after controlling the confounding factors. Then we determined the effects of Nestin on cell proliferation, colony formation, invasion, and apoptosis by knockout of Nestin with a new developed method, CRISPR/Cas9 mediated genome editing. It was observed that knockout of Nestin caused enhancement of cancer cell apoptosis and inhibition of cell proliferation, colony formation, and invasion in A549 and H1299 cell lines. Furthermore, we examined the expression of epithelial-mesenchymal transition (EMT) related biomarkers such as E-cadherin and Vimentin in Nestin-depleted lung cancer cells and knockout of Nestin was found to inhibit EMT, suggesting the involvement of Nestin mediated EMT signaling in lung cancer. The finding above demonstrated that Nestin might serve as a prognostic factor and therapeutic target in NSCLCs.

Immunohistochemical Markers as Predictors of Histopathologic Response and Prognosis in Rectal Cancer Treated with Preoperative Adjuvant Therapy: State of the Art

We explain the state of the art of the immunohistochemical markers of response in rectal cancers treated with neoadjuvant medical therapies and its implication with prognosis. Neoadjuvant chemoradiotherapy is widely used to improve the outcome of patients with locally advanced rectal cancer, and the evaluation of the effects of medical therapy is to date based on histomorphological examination by applying four grading systems of response to therapy (tumor regression grade (TRG)). The need to identify immunohistochemical markers that could ensure a better assessment of response and possibly provide additional prognostic information has emerged. We identified p53, p27kip1, Ki67, matrix metalloprotease-9, survivin, Ki67 proliferative index, CD133, COX2, CD44v6, thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase as the most common markers studied in literature to date, and we explained their prognostic potential and their implications in the evaluation of the response to preoperative therapies in rectal cancers.

[Molecular markers of cancer stem cells verified in vivo]

This systematic review aims to analyze molecular markers of cancer stem cells. Only studies that confirmed tumor-initiating capacity of this population by in vivo assay in immunodeficient mice were included. Final sample of papers that fully correspond with initial aim consists of 97 original studies. The results of their analysis reveal that markers commonly used for cancer stem cells deriving were as follows: CD133, СD44, ALDH, CD34, CD24 and EpCAM. The review also contains description of molecular features of some cancer stem cell markers, modern approaches to cancer treatment by targeting this population and brief assessment of cancer stem cell theory development.

Spheres derived from the human SN12C renal cell carcinoma cell line are enriched in tumor initiating cells

Background

Recently, tumor initiating cells (TICs), which possess self-renewal and other stem cell properties, are regarded as the cause of tumor initiation, recurrence and metastasis. The isolation and identification of TICs could help to develop novel therapeutic strategies.

Methods

In this study, we isolated spheroid cells from human renal cell carcinoma (RCC) cell line SN12C in stem cell-conditioned medium. The stemness characteristics of spheroid cells, including tumorigenicity, self-renewal, proliferation and aldehyde dehydrogenase (ALDH) activity were evaluated; the expression levels of stemness genes and related proteins were assessed. Furthermore, study examined the differentiation of TICs into endothelial cells and the relationship between TICs and EMT.

Results

Our data demonstrated that spheroid cells cultured in defined serum-free medium possessed TIC properties, such as high tumorigenic capacity, upregulation of TIC-related genes and proteins, persistent self-renewal and extensive proliferation. Furthermore, spheroid cells were more aggressive in growth, invasion, scratch recovery, clonogenic survival and high aldehyde dehydrogenase (ALDH) activity. Interestingly, a marked increase in tumor vascularity compared to adherent tumors in vivo, and spheroid cells can differentiate into functional endothelial-like cells in vitro suggesting a role of tumor initiating cells in tumor angiogenesis. The spheroid cells also demonstrated down-regulated E-cadherin and up-regulated Vimentin expression, which is the typical phenotype of EMT.

Conclusions

These results suggest that spheroid cells with tumor initiating cells-like characteristics contributed to tumor generation, progression, high tumorigenicity, pro-angiogenic capability and relationship with EMT. Further experiments using more refined selection criteria such as a combination of two or multiple markers would be useful to specifically identify and purify TICs.

Nerve growth factor: role in growth, differentiation and controlling cancer cell development

Recent progress in the Nerve Growth Factor (NGF) research has shown that this factor acts not only outside its classical domain of the peripheral and central nervous system, but also on non-neuronal and cancer cells. This latter observation has led to divergent hypothesis about the role of NGF, its specific distribution pattern within the tissues and its implication in induction as well as progression of carcinogenesis. Moreover, other recent studies have shown that NGF has direct clinical relevance in certain human brain neuron degeneration and a number of human ocular disorders. These studies, by suggesting that NGF is involved in a plethora of physiological function in health and disease, warrant further investigation regarding the true role of NGF in carcinogenesis. Based on our long-lasting experience in the physiopathology of NGF, we aimed to review previous and recent in vivo and in vitro NGF studies on tumor cell induction, progression and arrest. Overall, these studies indicate that the only presence of NGF is unable to generate cell carcinogenesis, both in normal neuronal and non-neuronal cells/tissues. However, it cannot be excluded the possibility that the co-expression of NGF and pro-carcinogenic molecules might open to different consequence. Whether NGF plays a direct or an indirect role in cell proliferation during carcinogenesis remains to demonstrate.

Nestin overexpression in hepatocellular carcinoma associates with epithelial-mesenchymal transition and chemoresistance

Background

Nestin expression has been reported to be associated with the prognosis of many solid tumors including human hepatocellular carcinoma (HCC). The present study aimed to identify the role, if any, of Nestin in the chemotherapeutic treatment of HCC.

Methods

We determined Nestin expression in nine HCC cell lines and 220 tissue samples of advanced HCC patients (retrospectively registered) treated with FOLFOX regimens. We examined the correlations between Nestin expression and clinicopatholgical variables and HCC prognosis. Also, we used in vitro and in vivo methods to determine the effects of Nestin expression on HCC cell invasion, migration and chemosensitivity.

Results

Nestin expression was significantly increased in HCC tissues and drug-resistant cell lines, and the presence of high levels of Nestin was associated with poor survival. We also showed that drug-resistance occurred in HCC cells with epithelial-mesenchymal transition (EMT), which in turn enhanced invasion ability. Nestin depletion reversed drug-resistance in the Bel-7402/5-FU and Bel-7402/ADM cell lines. Nestin knockdown enhanced chemotherapeutic efficacy in nude mice. Moreover, Nestin up-regulation in Bel-7402 was associated with the activation of Wnt/β-catenin signaling.

Conclusion

Our findings suggest that Nestin inhibitors may be useful for the chemotherapy of HCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0387-y) contains supplementary material, which is available to authorized users.

Inhibition of SALL4 reduces tumorigenicity involving epithelial-mesenchymal transition via Wnt/β-catenin pathway in esophageal squamous cell carcinoma

BACKGROUND

Growing evidence suggests that SALL4 plays a vital role in tumor progression and metastasis. However, the molecular mechanism of SALL4 promoting esophageal squamous cell carcinoma (ESCC) remains to be elucidated.

METHODS

The gene and protein expression profiles- were examined by using quantitative real-time PCR, immunohistochemistry and western blotting. Small hairpin RNA was used to evaluate the role of SALL4 both in cell lines and in animal models. Cell proliferation, apoptosis and invasion were assessed by CCK8, flow cytometry and transwell-matrigel assays. Sphere formation assay was used for cancer stem cell derivation and characterization.

RESULTS

Our study showed that the transcription factor SALL4 was overexpressed in a majority of human ESCC tissues and closely correlated with a poor outcome. We established the lentiviral system using short hairpin RNA to knockdown SALL4 in TE7 and EC109 cells. Silencing of SALL4 inhibited the cell proliferation, induced apoptosis and the G1 phase arrest in cell cycle, decreased the ability of migration/invasion, clonogenicity and stemness in vitro. Besides, down-regulation of SALL4 enhanced the ESCC cells' sensitivity to cisplatin. Xenograft tumor models showed that silencing of SALL4 decreased the ability to form tumors in vivo. Furthermore, our study demonstrated that SALL4 played a vital role in modulating the stemness of ESCC cells via Wnt/β-catenin signaling pathway and in epithelial-mesenchymal transition.

CONCLUSIONS

Our results revealed that SALL4 might serve as a functional marker for ESCC cancer stem cell, a crucial marker for prognosis and an attractive candidate for target therapy of ESCC.

CD133, Selectively Targeting the Root of Cancer

Cancer stem cells (CSC) are capable of promoting tumor initiation and self-renewal, two important hallmarks of carcinoma formation. This population comprises a small percentage of the tumor mass and is highly resistant to chemotherapy, causing the most difficult problem in the field of cancer research, drug refractory relapse. Many CSC markers have been reported. One of the most promising and perhaps least ubiquitous is CD133, a membrane-bound pentaspan glycoprotein that is frequently expressed on CSC. There is evidence that directly targeting CD133 with biological drugs might be the most effective way to eliminate CSC. We have investigated two entirely unrelated, but highly effective approaches for selectively targeting CD133. The first involves using a special anti-CD133 single chain variable fragment (scFv) to deliver a catalytic toxin. The second utilizes this same scFv to deliver components of the immune system. In this review, we discuss the development and current status of these CD133 associated biological agents. Together, they show exceptional promise by specific and efficient CSC elimination.

The Effects of Thermal Preconditioning on Oncogenic and Intraspinal Cord Growth Features of Human Glioma Cells

The adult rodent spinal cord presents an inhibitory environment for donor cell survival, impeding efficiency for xenograft-based modeling of gliomas. We postulated that mild thermal preconditioning may influence the fate of the implanted tumor cells. To test this hypothesis, high-grade human astrocytoma G55 and U87 cells were cultured under 37C and 38.5C to mimic regular experimental or core body temperatures of rodents, respectively. In vitro, the 38.5C-conditioned cells, relative to 37C, grew slightly faster. Compared to U87 cells, G55 cells demonstrated a greater response to the temperature difference. Hyperthermal culture markedly increased production of Hsp27 in most G55 cells, but only promoted transient expression of cancer stem cell marker CD133 in a small cell subpopulation. We subsequently transplanted G55 cells following 37C or 38.5C culture into the C2 or T10 spinal cord of adult female immunodeficient rats (3 rats/each locus/per temperature; total: 12 rats). Systematic analyses revealed that 38.5C-preconditioned G55 cells grew more malignantly at either C2 or T10 as determined by tumor size, outgrowth profile, resistance to bolus intratumor administration of 5-fluorouracil (0.1 mol), and posttumor survival (p0.05; n=6/group). Therefore, thermal preconditioning of glioma cells may be an effective way to influence the in vitro and in vivo oncological contour of glioma cells. Future studies are needed for assessing the potential oncogenic modifying effect of hyperthermia regimens on glioma cells.

Glioma Stem Cells and Their Microenvironments: Providers of Challenging Therapeutic Targets

Malignant gliomas are aggressive brain tumors with limited therapeutic options, possibly because of highly tumorigenic subpopulations of glioma stem cells. These cells require specific microenvironments to maintain their “stemness,” described as perivascular and hypoxic niches. Each of those niches induces particular signatures in glioma stem cells (e.g., activation of Notch signaling, secretion of VEGF, bFGF, SDF1 for the vascular niche, activation of HIF2α, and metabolic reprogramming for hypoxic niche). Recently, accumulated knowledge on tumor-associated macrophages, possibly delineating a third niche, has underlined the role of immune cells in glioma progression, via specific chemoattractant factors and cytokines, such as macrophage-colony stimulation factor (M-CSF). The local or myeloid origin of this new component of glioma stem cells niche is yet to be determined. Such niches are being increasingly recognized as key regulators involved in multiple stages of disease progression, therapy resistance, immune-escaping, and distant metastasis, thereby substantially impacting the future development of frontline interventions in clinical oncology. This review focuses on the microenvironment impact on the glioma stem cell biology, emphasizing GSCs cross talk with hypoxic, perivascular, and immune niches and their potential use as targeted therapy.