Glioblastoma Invasion Research Articles

AN1-type zinc finger protein 3 (ZFAND3) is a transcriptional regulator that drives Glioblastoma invasion

The infiltrative nature of Glioblastoma (GBM), the most aggressive primary brain tumor, critically prevents complete surgical resection and masks tumor cells behind the blood brain barrier reducing the efficacy of systemic treatment. Here, we use a genome-wide interference screen to determine invasion-essential genes and identify the AN1/A20 zinc finger domain containing protein 3 (ZFAND3) as a crucial driver of GBM invasion. Using patient-derived cellular models, we show that loss of ZFAND3 hampers the invasive capacity of GBM, whereas ZFAND3 overexpression increases motility in cells that were initially not invasive. At the mechanistic level, we find that ZFAND3 activity requires nuclear localization and integral zinc-finger domains. Our findings indicate that ZFAND3 acts within a nuclear protein complex to activate gene transcription and regulates the promoter of invasion-related genes such as COL6A2, FN1, and NRCAM. Further investigation in ZFAND3 function in GBM and other invasive cancers is warranted.

Deeper and Deeper on the Role of BK and Kir4.1 Channels in Glioblastoma Invasiveness: A Novel Summative Mechanism?

In the last decades, increasing evidence has revealed that a large number of channel protein and ion pumps exhibit impaired expression in cancers. This dysregulation is responsible for high proliferative rates as well as migration and invasiveness, reflected in the recently coined term oncochannelopathies. In glioblastoma (GBM), the most invasive and aggressive primary brain tumor, GBM cells modify their ionic equilibrium in order to change their volume as a necessary step prior to migration. This mechanism involves increased expression of BK channels and downregulation of the normally widespread Kir4.1 channels, as noted in GBM biopsies from patients. Despite a large body of work implicating BK channels in migration in response to an artificial intracellular calcium rise, little is known about how this channel acts in GBM cells at resting membrane potential (RMP), as compared to other channels that are constitutively open, such as Kir4.1. In this review we propose that a residual fraction of functionally active Kir4.1 channels mediates a small, but continuous, efflux of potassium at the more depolarized RMP of GBM cells. In addition, coinciding with transient membrane deformation and the intracellular rise in calcium concentration, brief activity of BK channels can induce massive and rapid cytosolic water loss that reduces cell volume (cell shrinkage), a necessary step for migration within the brain parenchyma.

ANGI-03 Functional roles of CD166/activated leukocyte cell adhesion molecule (CD166/ALCAM) for glioblastoma invasion

CD166/activated leukocyte cell adhesion molecule (CD166/ALCAM) is a transmembrane receptor, widely expressed in various tissues, and is involved in several functions such as cell adhesion, neurogenesis and angiogenesis. We have previously reported that CD166/ALCAM is expressed on glioblastoma progenitor cells and is involved in glioblastoma invasion. However, we only have analyzed the functional roles of ALCAM using glioblastoma cell lines, not using patient derived xenografts. In this study, we investigated the functional roles of CD166/ALCAM using patient derived xenografts. We established CD166/ALCAM knocked-down glioblastoma patient derived cell lines by shRNA. For in vitro analysis, we seeded control and CD166/ALCAM knocked-down glioblastoma cells on culture dishes and performed time lapse analysis to investigate cell motility. For in vivo analysis, we orthotopically injected control and CD166/ALCAM knocked-down glioblastoma cells into the immunodeficient mice. When the mice got sick due to the tumor, we dissected the mice and analyzed the difference in invasion by immunohistochemical analysis. We found that CD166/ALCAM knocked-down glioblastoma cells significantly decreased cell motility by time lapse analysis. In addition, CD166/ALCAM knocked-down glioblastoma cells suppressed cell invasion and leptomeningeal metastasis by immunohistochemical analysis from patient derived xenografts. Our results suggest that CD166/ALCAM is involved in glioblastoma invasion, thus future studies are necessary to investigate whether CD166/ALCAM could be a therapeutic target for glioblastoma.

Myosin 10 Regulates Invasion, Mitosis, and Metabolic Signaling in Glioblastoma.

SummaryInvasion and proliferation are defining phenotypes of cancer, and in glioblastoma blocking one stimulates the other, implying that effective therapy must inhibit both, ideally through a single target that is also dispensable for normal tissue function. The molecular motor myosin 10 meets these criteria. Myosin 10 knockout mice can survive to adulthood, implying that normal cells can compensate for its loss; its deletion impairs invasion, slows proliferation, and prolongs survival in murine models of glioblastoma. Myosin 10 deletion also enhances tumor dependency on the DNA damage and the metabolic stress responses and induces synthetic lethality when combined with inhibitors of these processes. Our results thus demonstrate that targeting myosin 10 is active against glioblastoma by itself, synergizes with other clinically available therapeutics, may have acceptable side effects in normal tissues, and has potential as a heretofore unexplored therapeutic approach for this disease.

Influence of Lipoxygenase Inhibition on Glioblastoma Cell Biology.

Background: The relationship between glioblastoma (GBM) and fatty acid metabolism could be the key to elucidate more effective therapeutic targets. 15-lipoxygenase-1 (15-LOX), a linolenic acid and arachidonic acid metabolizing enzyme, induces both pro- and antitumorigenic effects in different cancer types. Its role in glioma activity has not yet been clearly described. The objective of this study was to identify the influence of 15-LOX and its metabolites on glioblastoma cell activity. Methods: GBM cell lines were examined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to identify 15-LOX metabolites. GBM cells treated with 15-LOX metabolites, 13-hydroxyoctadecadeinoic acid (HODE) and 9-HODE, and two 15-LOX inhibitors (luteolin and nordihydroguaiaretic acid) were also examined. Dose response/viability curves, RT-PCRs, flow cytometry, migration assays, and zymograms were performed to analyze GBM growth, migration, and invasion. Results: Higher quantities of 13-HODE were observed in five GBM cell lines compared to other lipids analyzed. Both 13-HODE and 9-HODE increased cell count in U87MG. 15-LOX inhibition decreased migration and increased cell cycle arrest in the G2/M phase. Conclusion: 15-LOX and its linoleic acid (LA)-derived metabolites exercise a protumorigenic influence on GBM cells in vitro. Elevated endogenous levels of 13-HODE called attention to the relationship between linoleic acid metabolism and GBM cell activity.

AEBP1 Promotes Glioblastoma Progression and Activates the Classical NF-κB Pathway.

Objective Our study was aimed at investigating the mechanistic consequences of the upregulation of adipocyte enhancer-binding protein 1 (AEBP1) in glioblastoma (GBM). Methods The expression of AEBP1 in GBM was assessed by bioinformatics analysis and qRT-PCR; the effects of AEBP1 on GBM cell proliferation, migration, invasion, and tumor growth in vitro and in vivo were detected by a CCK-8 assay, colony formation assay, scratch assay, Transwell assay, and subcutaneous tumor formation, respectively. The activation of related signaling pathways was monitored using western blot. Results Tumor-related databases and bioinformatics analysis revealed that AEBP1 was highly expressed in GBM and indicated poor outcome of patients; its high expression that was also confirmed in GBM tissues and cell lines was closely related to the tumor size. The results of in vitro experiments showed that AEBP1 could significantly promote GBM cell proliferation, migration, and invasion; in vivo experiments suggested that AEBP1 could contribute to the growth of GBM tumors. AEBP1 could upregulate the level of IκBα phosphorylation, decrease IκBα expression, activate the NF-κB signaling pathway, and promote the expression of downstream oncogenes. Conclusion Upregulated AEBP1 in GBM promotes GBM cell proliferation, migration, and invasion and facilitates tumor growth in vivo by activating the classical NF-κB pathway.

Astrocyte elevated gene-1 serves as a target of miR542 to promote glioblastoma proliferation and invasion.

Background:Epithelial to mesenchymal transition (EMT) is strongly linked with tumor invasion and metastasis, which performs a vital role in carcinogenesis and cancer progression. Emerging evidence suggests that microRNAs (miRNAs) expression are closely associated to EMT by regulating targeted genes. MiR542 has been found to be involved in the EMT program and bound up with various cancers. However, the functions of miR542 and its underlying mechanism in glioblastoma multiforme (GBM) remain largely unknown. In the current study, we investigated the effect of astrocyte elevated gene-1 (AEG-1) on U251 cells aggressiveness, proliferation, apoptosis, and cell cycle.Methods:The screening of targeted miRNAs was performed, as well as the functional roles and mechanisms of miR542 were explored.Results:MiR542 was selected as the target because of the most significantly differential expression and this high level of expression negatively correlated with cell migration and proliferation, which suggested that miR542 could be a novel tumor suppressor. Moreover, we confirmed that AEG-1 was a direct targeted gene of miR542 by luciferase activity assay, reverse transcription-polymerase chain reaction, and immunoblotting analysis. Furthermore, miR542 suppressed the expression of AEG-1, which upgraded the level of E-cadherin and degraded Vimentin expression contributing to retraining EMT.Conclusion:The in vitro findings demonstrated that miR542 inhibited the migration and proliferation of U251 cells and suppressed EMT through targeting AEG-1, indicating that miR542 may be a potential anti-cancer target for GBM.

BYSL Promotes Glioblastoma Cell Migration, Invasion, and Mesenchymal Transition Through the GSK-3β/β-Catenin Signaling Pathway.

BYSL, which encodes the human bystin protein, is a sensitive marker for astrocyte proliferation during brain damage and inflammation. Previous studies have revealed that BYSL has important roles in embryo implantation and prostate cancer infiltration. However, the role and mechanism of BYSL in glioblastoma (GBM) cell migration and invasion remain unknown. We found that knockdown of BYSL inhibited cell migration and invasion, downregulated the expression of mesenchymal markers (e.g., β-catenin and N-cadherin), and upregulated the expression of epithelial marker E-cadherin in GBM cell lines. Overexpression of BYSL promoted GBM cell migration, invasion, and epithelial-mesenchymal transition (EMT). In addition, the role of BYSL in promoting EMT was further confirmed in a glioma stem cell line derived from a GBM patient. Mechanistically, overexpression of BYSL increased the phosphorylation of GSK-3β and the nuclear distribution of β-catenin. Inhibition of GSK-3β by 1-Azakenpaullone could partially reverse the effects of BYSL downregulation on the transcriptional activity of β-catenin, the expression of EMT markers, and GBM cell migration/invasion. Moreover, immunohistochemical analysis showed strong expression of BYSL in GBM tissues, which was positively correlated with markers of mesenchymal GBM. These results suggest that BYSL promotes GBM cell migration, invasion, and EMT through the GSK-3β/β-catenin signaling pathway.

Inhibition of TRPM7 with waixenicin A reduces glioblastoma cellular functions

Glioblastoma (GBM) is the most common malignant primary brain tumour originating in the CNS. Median patient survival is <15 months with standard treatment which consists of surgery alongside radiation therapy and temozolomide chemotherapy. However, because of the aggressive nature of GBM, and the significant toxicity of these adjuvant therapies, long-term therapeutic effects are unsatisfactory. Thus, there is urgency to identify new drug targets for GBM. Recent evidence shows that the transient receptor potential melastatin 7 (TRPM7) cation channel is aberrantly upregulated in GBM and its inhibition leads to reduction of GBM cellular functions. This suggests that TRPM7 may be a potential drug target for GBM treatment. In this study, we assessed the effects of the specific TRPM7 antagonist waixenicin A on human GBM cell lines U87 or U251 both in vitro and in vivo. First, we demonstrated in vitro that application of waixenicin A reduced TRPM7 protein expression and inhibited the TRPM7-like currents in GBM cells. We also observed reduction of GBM cell viability, migration, and invasion. Using an intracranial xenograft GBM mouse model, we showed that with treatment of waixenicin A, there was increased cleaved caspase 3 activity, alongside reduction in Ki-67, cofilin, and Akt activity in vivo. Together, these data demonstrate higher GBM cell apoptosis, and lower proliferation, migration, invasion and survivability following treatment with waixenicin A.

Megalencephalic leukoencephalopathy with subcortical cysts 1 (MLC1) promotes glioblastoma cell invasion in the brain microenvironment.

Glioblastoma (GBM), or grade IV astrocytoma, is a malignant brain cancer that contains sub-populations of proliferative and invasive cells that coordinately drive tumor growth, progression and recurrence after therapy. Here, we have analyzed functions for megalencephalic leukoencephalopathy with subcortical cysts 1 (Mlc1), an eight-transmembrane protein normally expressed in perivascular brain astrocyte endfeet that is essential for neurovascular development and physiology, in the pathogenesis of GBM. We show that Mlc1 is expressed in human stem-like GBM cells (GSCs) and is linked to the development of primary and recurrent GBM. Genetically inhibiting MLC1 in GSCs using RNAi-mediated gene silencing results in diminished growth and invasion in vitro as well as impaired tumor initiation and progression in vivo. Biochemical assays identify the receptor tyrosine kinase Axl and its intracellular signaling effectors as important for MLC1 control of GSC invasive growth. Collectively, these data reveal key functions for MLC1 in promoting GBM cell growth and invasion, and suggest that targeting the Mlc1 protein or its associated signaling effectors may be a useful therapy for blocking tumor progression in patients with primary or recurrent brain cancer.

Myosin 10 Regulates Invasion, Mitosis, and Metabolic Signaling in Glioblastoma

Invasion and proliferation are defining phenotypes of cancer, and in glioblastoma blocking one stimulates the other. This implies that effective therapy must inhibit both, ideally through a single target that is also dispensable for normal tissue function. The molecular motor myosin 10 meets these criteria. Myosin 10 knockout mice are viable, implying that normal cells can compensate for its loss; and its deletion impairs directional migration, slows proliferation, and prolongs survival in murine models of glioblastoma. Myosin 10 deletion also enhances tumor dependency on the DNA damage and the metabolic stress responses, and induces synthetic lethality when combined with inhibitors of these processes. Our results thus demonstrate that targeting myosin 10 is effective against glioblastoma by itself, synergizes with other clinically available therapeutics, is likely to be non-toxic to normal tissues, and is therefore a compelling therapeutic approach for this disease.

The Role of Hypoxia and SRC Tyrosine Kinase in Glioblastoma Invasiveness and Radioresistance.

Simple SummaryThe biological pathways underlying glioblastoma malignancy and radioresistance are still unclear. In this review, we describe the role of the hypoxic microenvironment and SRC proto-oncogene non-receptor tyrosine kinase in the activation of radioresistance and invasion pathways of glioblastoma. We also highlight the hypoxia- and ionizing radiation-induced infiltration, providing updated evidences on the involvement of SRC in these processes. Optimizing radiotherapy and identifying druggable molecular players are crucial steps to improve current glioblastoma therapeutic strategies.Advances in functional imaging are supporting neurosurgery and radiotherapy for glioblastoma, which still remains the most aggressive brain tumor with poor prognosis. The typical infiltration pattern of glioblastoma, which impedes a complete surgical resection, is coupled with a high rate of invasiveness and radioresistance, thus further limiting efficient therapy, leading to inevitable and fatal recurrences. Hypoxia is of crucial importance in gliomagenesis and, besides reducing radiotherapy efficacy, also induces cellular and molecular mediators that foster proliferation and invasion. In this review, we aimed at analyzing the biological mechanism of glioblastoma invasiveness and radioresistance in hypoxic niches of glioblastoma. We also discussed the link between hypoxia and radiation-induced radioresistance with activation of SRC proto-oncogene non-receptor tyrosine kinase, prospecting potential strategies to overcome the current limitation in glioblastoma treatment.

Upregulated CBX8 Promotes Cancer Metastasis via the WNK2/MMP2 Pathway

Metastasis is associated with poor prognosis in cancer and is a multistep process that includes invasion and migration. Several epigenetic factors are involved in this process, including chromobox protein homolog 8 (CBX8). Here, we show that CBX8 is overexpressed in many cancers compared with normal tissues. Functional analyses indicated that CBX8 promoted invasion and migration in glioblastoma, breast cancer, and lung cancer in vitro and in vivo. WNK2 was identified as a target gene of CBX8, which interacted with the WNK2 promoter to suppress WNK2 expression and activity. WNK2 acted as an antioncogene, and decreased WNK2 levels resulted in high activity of matrix metalloprotease (MMP)-2 and RAC1, which play a central role in invasion and migration, respectively. There was a positive relationship between MMP2 and RAC1 activity in CBX8-modulated cell lines. In addition, WNK2 negatively regulated MMP2 and RAC1 activity. Collectively, the results indicated that CBX8 promoted invasion and migration by targeting WNK2, which resulted in increased RAC1 and MMP2 expression and activity. Therefore, CBX8 may be a novel therapeutic target to treat metastatic cancers.

Dutasteride combined with androgen receptor antagonists inhibit glioblastoma U87 cell metabolism, proliferation, and invasion capacity: Androgen regulation

Glioblastoma (GB) is the most common and aggressive primary brain tumor in adult humans. Therapeutic resistance and tumor recurrence after surgical resection contributes to a poor prognosis for glioblastoma patients. Men are known to be more likely than women to develop an aggressive form of GB. Although the reasons for this disparity remain poorly understood, differences in sex steroids have emerged as a leading explanation. Studies indicate that GB-derived cells express androgen receptors (ARs) and synthesize androgens, suggesting that androgens may have a role in the tumor pathogenesis. Thus, our objective was to investigate the effects of the 5α-reductase enzyme inhibitor dutasteride, the AR antagonists cyproterone and flutamide, and combinations of these drugs on the metabolism, proliferation, and invasion capacity of GB-derived U87 cells. We also examined the effects of three natural androgens testosterone, androstenedione and dihydrotestosterone (T, A4, and DHT) on these cells. Cell metabolism was investigated by MTT assay, proliferation was assessed by the bromodeoxyuridine (BrdU) incorporation assay, and invasion was assessed by Boyden chamber assay. The results revealed that T and especially DHT, but not A4, increased U87 cell metabolism and proliferation. Following these findings, we examined the effect of adding dutasteride, cyproterone, or flutamide to the culture media and found that they all significantly decreased cell metabolism and proliferation. Dutasteride also significantly reduced cell invasion. Moreover, any combination of these drugs enhanced their inhibitory effects; the combination of dutasteride to flutamide was most effective at decreasing GB cell proliferation. Our results suggest that administering a combination of AR antagonists and enzyme blockers may be a more effective alternative treatment for GB.

Sphingolipid Metabolism in Glioblastoma and Metastatic Brain Tumors: A Review of Sphingomyelinases and Sphingosine-1-Phosphate.

Glioblastoma (GBM) is a primary malignant brain tumor with a dismal prognosis, partially due to our inability to completely remove and kill all GBM cells. Rapid tumor recurrence contributes to a median survival of only 15 months with the current standard of care which includes maximal surgical resection, radiation, and temozolomide (TMZ), a blood–brain barrier (BBB) penetrant chemotherapy. Radiation and TMZ cause sphingomyelinases (SMase) to hydrolyze sphingomyelins to generate ceramides, which induce apoptosis. However, cells can evade apoptosis by converting ceramides to sphingosine-1-phosphate (S1P). S1P has been implicated in a wide range of cancers including GBM. Upregulation of S1P has been linked to the proliferation and invasion of GBM and other cancers that display a propensity for brain metastasis. To mediate their biological effects, SMases and S1P modulate signaling via phospholipase C (PLC) and phospholipase D (PLD). In addition, both SMase and S1P may alter the integrity of the BBB leading to infiltration of tumor-promoting immune populations. SMase activity has been associated with tumor evasion of the immune system, while S1P creates a gradient for trafficking of innate and adaptive immune cells. This review will explore the role of sphingolipid metabolism and pharmacological interventions in GBM and metastatic brain tumors with a focus on SMase and S1P.

MiR-1225-5p acts as tumor suppressor in glioblastoma via targeting FNDC3B.

This study attempted to research the molecular mechanism underlying the inhibitory role of miR-1225-5p in the malignant progression of glioblastoma. Bioinformatics analyses based on the gene expression omnibus (GEO) and Chinese glioma genome atlas (CGGA) databases showed that miR-1225-5p, as a favorable prognostic factor, was expressed at low levels in glioblastoma, and its expression was also related to WHO grade and age. The subsequent CCK-8 assay indicated that miR-1225-5p might prevent the malignant progression of glioblastoma, which was represented by that miR-1225-5p mimic reduced the viability of glioblastoma cells. Then, we predicted that FNDC3B might be a potential target gene of miR-1225-5p, and it was negatively correlated with the level of miR-1225-5p, which were confirmed by dual-luciferase reporter assay, qRT-PCR and western blot assays. Moreover, based on the analyses of the cancer genome atlas (TCGA), Oncomine and CGGA databases, FNDC3B was enriched in glioblastoma and high expression of FNDC3B led to poor prognosis. Finally, CCK8 and transwell experiments showed that the ability of miR-1225-5p to inhibit glioblastoma cell viability, invasion and migration was at least partially achieved by targeting FNDC3B. In general, these results revealed that the miR-1225-5p/FNDC3B axis contributes to inhibiting the malignant phenotype of glioblastoma cells, which lays a foundation for molecular diagnosis and treatment of glioblastoma.

Sulforaphane-cysteine inhibited migration and invasion via enhancing mitophagosome fusion to lysosome in human glioblastoma cells

Here we uncovered the involved subcellular mechanisms that sulforaphane-cysteine (SFN-Cys) inhibited invasion in human glioblastoma (GBM). SFN-Cys significantly upregulated 45 and downregulated 14 microtubule-, mitophagy-, and invasion-associated proteins in GBM cells via HPLC–MS/MS and GEO ontology analysis; SFN-Cys disrupted microtubule by ERK1/2 phosphorylation-mediated downregulation of α-tubulin and Stathmin-1 leading to the inhibition of cell migration and invasion; SFN-Cys downregulated invasion-associated Claudin-5 and S100A4, and decreased the interaction of α-tubulin to Claudin-5. Knockdown of Claudin-5 and S100A4 significantly reduced the migration and invasion. Besides, SFN-Cys lowered the expressions of α-tubulin-mediated mitophagy-associated proteins Bnip3 and Nix. Transmission electron microscopy showed more membrane-deficient mitochondria and accumulated mitophagosomes in GBM cells, and mitochondria fusion might be downregulated because that SFN-Cys downregulated mitochondrial fusion protein OPA1. SFN-Cys increased the colocalization and interplay of LC3 to lysosomal membrane-associated protein LAMP1, aggravating the fusion of mitophagosome to lysosome. Nevertheless, SFN-Cys inhibited the lysosomal proteolytic capacity causing LC3II/LC3I elevation but autophagy substrate SQSTM1/p62 was not changed, mitophagosome accumulation, and the inhibition of migration and invasion in GBM cells. These results will help us develop high-efficiency and low-toxicity anticancer drugs to inhibit migration and invasion in GBM.

MicroRNA-623 Inhibits Epithelial-Mesenchymal Transition to Attenuate Glioma Proliferation by Targeting TRIM44.

ObjectiveGlioma has the highest incidence among the different tumor types within the nervous system, accounting for about 40% of them. Malignant glioma has a high invasion and metastasis rate, which leads to the poor prognosis of patients. By targeting specific genes, microRNAs serve as key regulators in the epithelial–mesenchymal transformation (EMT) process, which could provide new insights into the treatment of glioblastomas (GBM). The detailed molecular role that miR-623 plays in GBM still remains unclear.Materials and MethodsThe level of miR-623 in GBM cells was evaluated by RT-PCR. The function of miR-623 overexpression on GBM cell proliferation, migration, and invasion was assessed by MTS, Transwell analysis, and colony formation assay. In addition, a mouse subcutaneous xenograft model was used to study in vivo effects. The binding between miR-623 and TRIM44 was verified by a dual-luciferase reporter assay and the regulatory function of miR-623 on EMT markers was evaluated using Western blot.ResultsThe expression of miR-623 was repressed in the GBM cancer cell lines. MiR-623 overexpression or TRIM44 knockdown attenuated the proliferation, migration, and invasion of GBM cell lines. TRIM44 could facilitate the reverse suppression of EMT and miR-623 in GBM progression. MiR-623 was found to inhibit TRIM44 expression by directly binding to its 3ʹUTR. In addition, systemic delivery of miR-623 mimic reduced tumor growth and inhibited TRIM44 protein expression in tumor-bearing nude mice. Furthermore, our findings indicated that miR-623 overexpression or TRIM44 down-regulation impeded the proliferation and migratory ability of LN229 and U251MG glioma cells, and miR-623 attenuates TRIM44-induced EMT by directly targeting the 3ʹUTR of TRIM44, which could serve as preliminary research to identify potential therapeutic targets for future treatment of GBM.ConclusionOverall, microRNA-623 inhibits epithelial–mesenchymal transition to attenuate glioma proliferation by targeting TRIM44.

Mechanisms of invasion in glioblastoma.

This review provides an overview of recent updates in understanding the mechanisms by which glioblastoma cells interact with their cellular and molecular partners within the microenvironment. We have now a better knowledge of the cell populations involved in Glioblastoma (GBM) invasion. Recent works discovered the role of new molecular players in GBM invasion, and, most importantly, better models are emerging which better recapitulate GBM invasion. Invasive properties of glioblastoma make complete surgical resection impossible and highly invasive cells are responsible for tumor recurrence. In this review, we focus on recent updates describing how invasive cells progress in the surrounding tissue along brain structures. We also provide an overview of the current knowledge on key cells and molecular players within the microenvironment that contribute to the invasive process. VIDEO ABSTRACT.

TRPV4 activates the Cdc42/N-wasp pathway to promote glioblastoma invasion by altering cellular protrusions

The invasion ability of glioblastoma (GBM) causes tumor cells to infiltrate the surrounding brain parenchyma and leads to poor outcomes. Transient receptor potential vanilloid 4 (TRPV4) exhibits a remarkable role in cancer cell motility, but the contribution of TRPV4 to glioblastoma metastasis is not fully understood. Here, we reported that TRPV4 expression was significantly elevated in malignant glioma compared to normal brain and low-grade glioma, and TRPV4 expression was negatively correlated with the prognosis of glioma patients. Functionally, stimulation of TRPV4 promoted glioblastoma cell migration and invasion, and repression of TRPV4 hindered the migration and invasion of glioblastoma cells in vitro. Molecularly, TRPV4 strongly colocalized and interacted with skeletal protein-F-actin at cellular protrusions, and TRPV4 regulated the formation of invadopodia and filopodia in glioblastoma cells. Furthermore, the Cdc42/N-wasp axis mediated the effect of TRPV4-regulated cellular protrusions and invasion. Foremost, TRPV4 inhibitor treatment or downregulation of TRPV4 significantly reduced the invasion-growth of subcutaneously and intracranially transplanted glioblastoma in mice. In conclusion, the TRPV4/Cdc42/wasp signaling axis regulates cellular protrusion formation in glioblastoma cells and influences the invasion-growth phenotype of glioblastoma in vivo. TRPV4 may serve as a prognostic factor and specific therapeutic target for GBM patients.