The D Domain of LRRC4 anchors ERK1/2 in the cytoplasm and competitively inhibits MEK/ERK activation in glioma cells

β-receptor blocker enhances anti-tumor immunity via inhibiting lactate-induced norepinephrine metabolism of macrophages during malignant pleural effusion

Introduction

Malignant pleural effusion (MPE) is associated with poor quality of life and mortality in patients with tumors. In clinical practice, we observed that patients with malignant pleural effusion (MPE) and concurrent heart disease exhibited a decrease in MPE volumes following treatment with β-receptor blockers for heart disease. Immunosuppressive tumor microenvironment was found to play a substantial role in the progression of MPE, and mainly attributed to tumor-associated macrophages (TAMs). However, whether β-receptor blockers improve MPE through affecting the immune microenvironment especially TAMs and the potential mechanism behind remains unclear.

Methods

In this study, we collected the MPE samples from MPE and heart disease patients treated with propranolol, and performed flow cytometry experiment to evaluate the effect of propranolol on MPE immune microenvironment. Then, the mechanism that how propranolol effectively reprogrammed the immunosuppressive microenvironment of MPE was conducted by the experiments of mass spectrometry, RNA-seq, flow cytometry, immunofluorescence, western blotting, etc. Lastly, to further evaluate the effect of propranolol on MPE therapy in vivo, we developed a mouse model of MPE. We administrated propranolol into MPE-bearing mice to investigate the therapy efficacy and the changes of MPE microenvironment by the experiments of computed tomography (CT) scanning, flow cytometry, etc.

Results

We observed that propranolol treatment in MPE patients with heart disease decreased TAM frequency and immunosuppression and enhanced anti-tumor immunity. Macrophages in MPE exhibited an immunosuppressive phenotype via the activation of norepinephrine metabolism. Subsequently, we found that lactate was increased in MPE and may contribute to an increase in TAM frequency and inhibition of anti-tumor immunity by macrophages. Additionally, lactate triggered phenylalanine/norepinephrine signaling and further induced macrophage immunosuppression in an ERK-depended way. Lastly, in the MPE mouse model, propranolol inhibited MPE development and reversed the immune microenvironment of MPE.

Discussion

Here, we reveal the mechanism by which lactate induces macrophage immunosuppression via activating phenylalanine/norepinephrine signaling. Our findings highlight that blocking norepinephrine signaling by β-receptor blockers is an attractive therapeutic strategy to enhance anti-tumor immunity in the context of MPE.

Leucine-rich repeats containing 4 protein (LRRC4) in memory, psychoneurosis, and glioblastoma

ABSTRACT

Leucine-rich repeats containing 4 ( LRRC4 , also named netrin-G ligand 2 [NGL-2]) is a member of the NetrinGs ligands (NGLs) family. As a gene with relatively high and specific expression in brain, it is a member of the leucine-rich repeat superfamily and has been proven to be a suppressor gene for gliomas, thus being involved in gliomagenesis. LRRC4 is the core of microRNA-dependent multi-phase regulatory loops that inhibit the proliferation and invasion of glioblastoma (GB) cells, including LRRC4/NGL2-activator protein 2 (AP2)-microRNA (miR) 182-LRRC4 and LRRC4-miR185-DNA methyltransferase 1 (DNMT1)-LRRC4/specific protein 1 (SP1)-DNMT1-LRRC4. In this review, we demonstrated LRRC4 as a new member of the partitioning-defective protein (PAR) polarity complex that promotes axon differentiation, mediates the formation and plasticity of synapses, and assists information input to the hippocampus and storage of memory. As an important synapse regulator, aberrant expression of LRRC4 has been detected in autism, spinal injury and GBs. LRRC4 is a candidate susceptibility gene for autism and a neuro-protective factor in spinal nerve damage. In GBs, LRRC4 is a novel inhibitor of autophagy, and an inhibitor of protein-protein interactions involving in temozolomide resistance, tumor immune microenvironment, and formation of circular RNA.

The Current Status of SSRP1 in Cancer: Tribulation and Road Ahead

Methods

We search PubMed and Web of Sciences with keywords “SSRP1” and “Cancer.” Only English literature was included, and conference papers and abstract were all excluded.

Results

Transcription factors are classified into three groups based on their DNA binding motifs: simple helix-loop-helix (bHLH), classical zinc fingers (ZF-TFs), and homeodomains. The tumor-suppressive miR-497 (microRNA-497) acted as an undesirable regulator of SSRP1 upregulation, which led to tumor growth. The siRNA (small interfering RNA) knockdown of SSRP1 hindered cell proliferation along with incursion and glioma cell migration. Through the AKT (also known as protein kinase B) signaling pathway, SSRP1 silencing affected cancer apoptosis and cell proliferation.

Conclusion

The MAPK (mitogen-activated protein kinase) signaling pathway's phosphorylation was suppressed when SSRP1 was depleted. The effect of curaxins on p53 and NF-B (nuclear factor-κB), and their toxicity to cancer cells, is attributable to the FACT (facilitates chromatin transcription) complex's chromatin trapping.

LRRC4 mediates the formation of circular RNA CD44 to inhibitGBM cell proliferation

Mounting evidence reveals that dysregulation of circular RNAs (circRNAs) is involved in the development of glioblastoma. Leucine-rich repeat-containing 4 (LRRC4) has been shown to suppress tumors in glioblastoma. However, whether LRRC4 can regulate the formation of circRNA is not yet understood. In this study, LRRC4 was found to interact with SAM68. LRRC4 promoted the generation of circCD44 by inhibiting the binding between SAM68 and CD44 pre-mRNA. Moreover, downregulated expression of circCD44 was found in glioblastoma multiforme (GBM) tissues and GBM primary cells. Re-expression of circCD44 significantly suppressed the proliferation, colony formation, and invasion of GBM cells and inhibited tumor growth in vivo. Mechanistically, circCD44 could regulate the expression of SMAD6 via sponging miR-326 and miR-330-5p involved in the progression of GBM. Thus, the LRRC4/SAM68/circCD44/miR-326/miR-330-5p/SMAD6 signaling axis could be a potential target for GBM treatment.

Antitumor effect of 4MU on glioblastoma cells is mediated by senescence induction and CD44, RHAMM and p-ERK modulation

The extracellular matrix plays a key role in cancer progression. Hyaluronan, the main glycosaminoglycan of the extracellular matrix, has been related to several tumor processes. Hyaluronan acts through the interaction with cell membrane receptors as CD44 and RHAMM and triggers signaling pathways as MEK/ERK. 4-methylumbelliferone (4MU), a well-known hyaluronan synthesis inhibitor, is a promising alternative for cancer therapy. 4MU is a coumarin derivative without adverse effects that has been studied in several tumors. However, little is known about its use in glioblastoma (GBM), the most malignant primary brain tumor in adults. Glioblastoma is characterized by fast growth, migration and tissue invasiveness, and a poor median survival of the patients after treatment. Several reports linked glioblastoma progression with HA levels and even with CD44 and RHAMM expression, as well as MEK/ERK activation. Previously, we showed on a murine GBM cell line that HA enhances GBM migration, while 4MU markedly inhibits it. In this work we showed for the first time, that 4MU decreases cell migration and induces senescence in U251 and LN229 human GBM cell lines. Furthermore, we observed that HA promotes GBM cell migration on both cell lines and that such effects depend on CD44 and RHAMM, as well as MEK/ERK signaling pathway. Interestingly, we observed that the exogenous HA failed to counteract the effects of 4MU, indicating that 4MU effects are independent of HA synthesis inhibition. We found that 4MU decreases total CD44 and RHAMM membrane expression, which could explain the effect of 4MU on cell migration. Furthermore, we observed that 4MU increases the levels of RHAMM inside the cell while decreases the nucleus/cytoplasm relation of p-ERK, associated with 4MU effects on cell proliferation and senescence induction. Overall, 4MU should be considered as a promising therapeutic alternative to improve the outcome of patients with GBM.

LINC00152 acts as a potential marker in gliomas and promotes tumor proliferation and invasion through the LINC00152/miR-107/RAB10 axis

PURPOSE

Aberrant expression of long noncoding RNAs plays a pivotal role in tumorigenesis. Recently, several studies have showed that the LINC00152 gene is upregulated in a variety of tumors and plays an oncogene role; however, its underlying molecular mechanisms in glioblastoma remain unclear. In this study, we prepare to investigate the biological role and underlying molecular mechanisms of LINC00152 in glioblastoma cells.

METHODS

Bioinformatics analysis to identify LINC00152 expression, Cell Counting kit-8 assay and Colony formation assay were used to evaluate proliferation, Flow cytometric analysis was used to evaluate apoptosis, Cell Matrigel invasion assay and Wound healing assay was used to evaluate invasion, Western blot analysis to check protein expression level, Mouse xenograft models was used to check cell proliferation in vivo.

RESULTS

In this study, we found that LINC00152 was upregulated in gliomas and its expression was significantly associated with high tumor aggressiveness and poor outcomes for glioma patients. Functionally, the knockdown of LINC00152 not only inhibited malignant behaviors of glioma, such as proliferation and invasion of glioma cells and induced apoptosis in vitro but also suppressed tumorigenesis in vivo. Mechanistically, results of the bioinformatics analysis and experimental studies confirmed that LINC00152 and RAB10 as the targets of miR-107, and LINC00152 might act as a sponge for miR-107 to regulate the expression of RAB10 in glioblastoma. Additionally, silencing miR-107 reversed the effects induced by LINC00152 knockdown on glioblastoma cells both in vitro and in vivo.

CONCLUSION

Our data suggested that LINC00152 is a candidate prognostic marker of glioma, and that the LINC00152/MIR-107/RAB10 axis plays a pivotal role in regulation of the glioma malignancy, and therefore, targeting the axis might be an effective therapeutic strategy to treat glioma.

Circular RNAs and cancer: Opportunities and challenges

Circular RNAs (circRNAs) are covalently circularized RNA moieties that despite being relatively abundant were only recently identified and have only begun to be investigated within the last couple of years. Even though there are many thousands of genes that appear capable of producing circRNAs, and the fact that many circRNAs appear to be highly evolutionarily conserved, the function of all but a few remain to be fully explored. What has been determined, however, is that circRNAs play key regulatory roles in many aspects of biology with focus being given to their function in cancer. Most of the studies to date have found that circRNAs act as master regulator of gene expression most often than not acting to regulate levels though sequestration or "sponging" of other gene expression regulators, particularly miRNAs. They can also function directly modulating transcription, or by interfering with splicing mechanisms. Some circRNAs can also be translated into functional proteins or peptides. A combination of tissue and developmental stage specific expression along with an innate resistance to RNAse activity means that circRNAs show perhaps their greatest potential as novel biomarkers of cancer. In this chapter we consider the current state of knowledge regarding these molecules, their synthesis, function, and association with cancer. We also consider some of the challenges that remain to be overcome to allow this emerging class of RNAs to fulfill their potential in clinical practice.

A novel function of IMPA2, plays a tumor-promoting role in cervical cancer

Discovery of genes and molecular mechanism involved in cervical cancer development would promote the prevention and treatment. By comparing gene expression profiles of cervical carcinoma in situ (CCIS) and adjacent normal tissues, we identified a potential cancer-promoting gene, IMPA2. This study aimed to elucidate the role of IMPA2 and underlying molecular mechanisms in cervical cancer progression. To do this expression of IMPA2 was compared between human cervical cancer and corresponding adjacent normal cervical tissues firstly. CCK-8 assay, clone formation assay, wound healing assay, transwell assay, and tumor formation in nude mice were performed to demonstrate the effect of IMPA2 in cervical cancer proliferation and metastasis. Further proteomic profiling and western blotting explored the molecular pathway involved in the IMPA2-regulating process. The results showed that IMPA2 gene expression was upregulated in cervical cancer. Consistently, silencing of IMPA2 suppressed tumor formation in BALB/c nude mice. Short hairpin RNA (shRNA)-mediated IMPA2 silencing significantly inhibited proliferation and colony-forming abilities of cervical cancer cells, while IMPA2 overexpression had little impact. Also, IMPA2 silencing suppressed cellular migration, but overexpression promoted migration. Proteomics analysis revealed the involvement of mitogen-activated protein kinase (MAPK) pathway in tumor-promoting action of IMPA2. Significantly, the inhibition of IMPA2 activated ERK phosphorylation, and its inhibitory effects can be restored by using selective ERK inhibitor, FR180204. In conclusion, IMPA2 acts as an oncogene in the proliferation and migration of cervical cancer. IMPA2 downregulated ERK phosphorylation to promote cervical cancer. These findings identify a new mechanism underlying cervical cancer and suggest a regulating effect of IMPA2 in MAPK signaling pathway.

Leucine-rich repeat containing 4 act as an autophagy inhibitor that restores sensitivity of glioblastoma to temozolomide

Temozolomide (TMZ) insensitivity and resistance are major causes of treatment failure and poor prognosis for GBM patients. Here, we identify LRRC4 as a novel autophagy inhibitor that restores the sensitivity of GBMs to TMZ. LRRC4 was associated with the DEPTOR/mTOR complex, and this interaction resulted in autophagy inhibition. Further investigation demonstrated that the PDZ binding domain of LRRC4 binds to the PDZ domain of DEPTOR. This binding decreases the half-life of DEPTOR via ubiquitination, thus inhibiting GBM cell autophagy and increasing the TMZ treatment response of GBM. Combined LRRC4 expression and TMZ treatment prolonged the survival of mice with tumour xenografts. Furthermore, the levels of LRRC4, DEPTOR and autophagy are clinically relevant for GBM, indicating that LRRC4 is likely to have significant potential as a therapeutic marker and target for TMZ treatment in glioma patients.

LRRC4 Suppresses E-Cadherin-Dependent Collective Cell Invasion and Metastasis in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the most malignant gynecological carcinoma and is of a high incidence of death due to detection at late stages when metastasis already occurs. However, the mechanism underlying metastasis of EOC remains unclear. Analysis of the open database and experiments with immunochemistry showed that LRRC4 is lowly expressed in high-grade serous ovarian cancer (HGSC) cells and during EOC metastasis. The 3D cell culture system and the orthotopic ovarian xenograft model infected with LRRC4-containing adeno-associated virus serotype 9 (AAV9) were used to confirm collective invasion and metastasis of cells in vitro and in vivo. Phos-tag SDS-PAGE was used to detect the phosphorylation of LRRC4 and PIK3R1. A number of experiments with methods such as co-immunoprecipitation and immunoblotting were performed to explore the mechanism for the actions of LRRC4 and PIK3R1 in EOC metastasis. An inverse correlation between LRRC4 and E-cadherin expression was detected in the regions of invasion in primary EOC tissues and metastatic ascites. LRRC4 binds to the cSH2 domain of PIK3R1 and inhibits the activity of PIK3R1, without disrupting the physical interactions between PIK3R1 and PIK3CA. LRRC4 inhibits EOC metastasis by targeting E-cadherin-dependent collective cell invasion and does so by inhibiting the PIK3R1-mediated AKT/GSK3β/β-catenin signaling pathway. LRRC4 functions as a tumor suppressor gene to inhibit EOC collective invasion and metastasis in vitro and in vivo and does so by directly binding to the cSH2 domain of PIK3R1 to exert its regulatory function. Our findings provide a potential novel approach for metastasis prognosis and a new strategy for the treatment of EOC.

TNF-α mediated MEK-ERK signaling in invasion with putative network involving NF-κB and STAT-6: a new perspective in glioma

Glioblastoma is the most common malignant primary brain tumor with poor prognosis. Invasion involves pro-inflammatory cytokines and major signaling hubs. Tumor necrosis factor-α (TNF-α) acts as a master switch in establishing an intricate link between inflammation and cancer. The present study attempted to explore the possible implication of MAPK extracellular signaling-regulated kinase kinase (MEK)-extracellular signaling-regulated kinase (ERK) signaling pathway and expression of nuclear factor-κB (NF-κB), signal transducers and activators of transcription-6 (STAT-6), ERK, and phosphorylated-ERK (p-ERK) signaling proteins in TNF-α microenvironment. U0126 and PD98059 were used to inhibit the MEK-ERK1/2 pathway. TNF-α stimulation enhanced invasion in U87MG, U251MG and patient-derived primary glioma cells, whereas cell viability was not altered. Matrix metalloproteinase-2 (MMP-2) activity was increased only in U251MG glioma cells. These data suggest that TNF-α microenvironment plays an important role in the invasion of U251MG, U87MG, and patient-derived primary glioma cells, without any cytotoxic effect. The MMP-2 activity is differentially regulated by TNF-α stimulation in these cells. TNF-α stimulation upregulated the protein expression of ERK-1, ERK-2 and also increased the level of p-ERK1/2. TNF-α stimulation further upregulated the expression of NF-κB1, STAT-6 in tandem with Ras-MEK signaling system in U87MG cells, which emphasized the possible involvement of these signaling hubs in the glioma microenvironment. MEK-ERK inhibitors significantly attenuated the invasion of U87MG cells mediated by the TNF-α stimulation, probably through their inhibitory impact on p-ERK1/2 and ERK-2. This study provides the possible rationale of invasion by glioma cells in a TNF-α-induced pro-inflammatory milieu, which involves direct role of MEK-ERK signaling, with possible implication of NF-κB and STAT-6.

LncRNA GAS5 regulates the proliferation, migration, invasion and apoptosis of brain glioma cells through targeting GSTM3 expression. The effect of LncRNA GAS5 on glioma cells

INTRODUCTION

To investigate the effects of lncRNA GAS5 on the proliferation, migration, invasion and apoptosis of brain glioma cells.

METHODS

The expression levels of lncRNA GAS5 and GSTM3 in normal glial cells (HEB) and glioma cells (U251 and U87) were detected by RT-qPCR and western blot, respectively. Glioma cells were transfected with ctrl vector, pcDNA-GAS5, siRNA ctrl (siNC) or GSTM3 siRNA and the effects of lncRNA GAS5 and GSTM3 on the proliferation, migration, invasion and apoptosis of glioma cells were detected by CCK-8 assay, transwell assay and Caspase 3/7 activity assay, respectively.

RESULTS

The expression of lncRNA GAS5 was significantly decreased in glioma cell lines U251 and U87 compared with normal glial cells HEB (p < 0.01). In addition, overexpression of lncRNA GAS5 inhibited the proliferation, migration and invasion of U251 and U87 cells, and promoted cell apoptosis as demonstrated by the increased activity of Caspase 3/7. Furthermore, GSTM3 was predicted as a target gene of lncRNA GAS5 by bioinformatics analysis and its expression was increased in glioma cells compared with the normal cells as indicated by western blotting and RT-qPCR experimental results. Silencing of GSTM3 with GSTM3 siRNA decreased the proliferation, migration and invasion but increased the apoptosis of glioma cell lines U251 and U87, which was similar to that the effect lncRNA GAS5 over-expression.

CONCLUSION

lncRNA GAS5 can effectively inhibit the proliferation, migration and invasion of glioma cells and promote cell apoptosis through targeting GSTM3 expression.

Identification of Coiled-Coil Domain-Containing Protein 180 and Leucine-Rich Repeat-Containing Protein 4 as Potential Immunohistochemical Markers for Liposarcoma Based on Proteomic Analysis Using Formalin-Fixed, Paraffin-Embedded Tissue

Recent technical improvements in both mass spectrometry and protein extraction have made it possible to use formalin-fixed, paraffin-embedded (FFPE) tissues for proteome analysis. In this study, comparable proteome analysis of FFPE tissues revealed multiple candidate marker molecules for differentiating atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) from lipoma. A total of 181 unique proteins were identified for ALT/WDL. Of the identified proteins, coiled-coil domain-containing protein 180 (CCDC180) and leucine-rich repeat-containing protein 4 (LRRC4) were studied as candidate markers of ALT/WDL. CCDC180 and LRRC4 immunohistochemistry clearly stained tumor cells of ALT/WDL and dedifferentiated liposarcoma and could differentiate them from lipoma with high accuracy. Cell biological methods were used to further examine the expression of the candidate marker molecules in liposarcoma cells. In liposarcoma cells, knockdown of CCDC180 and LRRC4 inhibited cell proliferation. CCDC180 inhibited cell migration, invasion, and apoptosis resistance in WDL cells. Adipogenic differentiation suppressed the expression of CCDC180 and LRRC4 in WDL cells. These results indicated that LRRC4 and CCDC180 are novel immunohistochemical markers for differentiating ALT/WDLs. Their expression was associated with adipocyte differentiation and contributed to malignant potentials of WDL cells. Proteome analysis using a standard stock of FFPE tissues can reveal novel biomarkers for various diseases, which contributes to the progress of molecular pathology.

miR-128-3p inhibits glioma cell proliferation and differentiation by targeting NPTX1 through IRS-1/PI3K/AKT signaling pathway

It has been reported that glioma has a higher morbidity and mortality than other types of malignant brain tumor. While glioma has been extensively researched, the exact molecular mechanisms of its genesis and progression have remained to be fully elucidated. In order to explore a novel glioma-associated pathway which may represent a therapeutic target, 61 pairs of tumor tissues and adjacent normal tissues of glioma patients were collected and subjected to reverse-transcription quantitative polymerase chain reaction analysis, indicating that the relative expression of microRNA (miR)-128-3p was significantly decreased in the tumor tissues. However, the expression of neuronal pentraxin 1 (NPTX1) was obviously elevated. Through a bioinformatics analysis using Targetscan and transfection experiments, it was confirmed that NPTX1 was targeted by miR-128-3p. In the U251 human glioma cell line, transfection with miR-128-3p mimics increased the levels of phosphorylated insulin receptor substrate 1 (p-IRS-1), phosphoinositide-3 kinase (PI3K) and p-AKT, as demonstrated by western blot analysis. In addition, the proliferation rate of the cells was notably decreased following transfection with miR-128-3p mimics. Conversely, transfection with miR-128-3p inhibitor significantly increased the levels of p-IRS-1, PI3K and p-AKT, accompanied by an elevated proliferation rate of the cells. Therefore, it was indicated that miR-128-3p could reversely regulate NPTX1 expression. After the expression of NPTX1 was inhibited with specific small interfering RNA, the levels of p-IRS-1, PI3K and p-AKT were obviously decreased, while the expression of miR-128-3p was not significantly changed. Overall, it was concluded that miR-128-3p suppresses glioma through the NPTX1/IRS-1/PI3K/AKT signaling pathway.

Sirtuin 7 promotes glioma proliferation and invasion through activation of the ERK/STAT3 signaling pathway

Sirtuin7 (Sirt7) is a member of the Sir2 histone deacetylase family that functions in a number of physiological processes, including cellular metabolism, ageing and apoptosis. Several studies have indicated that Sirt7 may serve a vital role in promoting the development of cancer. However, to the best of our knowledge, its function in glioma progression has not been demonstrated. The present study revealed that Sirt7 expression was upregulated in human glioma tissues and that the high expression level of Sirt7 was positively associated with glioma malignancy. Further results indicated that the suppression of Sirt7 expression could inhibit the activation of phosphorylated extracellular signal-regulated kinase (p-ERK) concomitantly with decreased expression of cyclin-dependent kinase 2 in glioma cells. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) inhibited when Sirt7 was downregulated by siRNA interference in glioma cell lines. The findings of the present study indicated that Sirt7 affects the malignancy of glioma cells mainly in promoting glioma proliferation and invasion through ERK and STAT3 signaling. Thus, Sirt7 may function as a valuable target for the treatment of human glioma.

Circular RNAs: Functions and Prospects in Glioma

Improving the survival rate of patients with glioma, a malignant tumor of the human brain has become increasingly important. In recent years, the function of circular RNAs (circRNAs) in different diseases and the pathophysiological mechanisms involved have been elucidated. In the pathophysiological mechanism, the primary function of circRNAs is to act as microRNA sponges. An increasing number of studies have found that circRNAs are differentially expressed in gliomas and regulate the occurrence, proliferation, and invasion of glioma and thus may be potential markers for the diagnosis of gliomas. Additionally, some circRNAs have been associated with glioma staging and may be useful in determining prognosis. Based on the stability and high conservation of circRNAs, we believe that circRNAs may have molecular targets that are useful for the treatment of glioma. In this review, we summarize the current research regarding the role of circRNAs in gliomas, discuss the potential value and role of circRNAs in gliomas, and provide new perspectives for future research.

EPH receptor A2 governs a feedback loop that activates Wnt/β-catenin signaling in gastric cancer

The erythropoietin-producing hepatoma (EPH) receptor A2 (EphA2) belongs to the Eph family of receptor tyrosine kinases. EphA2 is highly correlated with the formation of many solid tumors and has been linked to the dysregulation of signaling pathways that promote tumor cell proliferation, migration, and invasion as well as angiogenesis. Deregulation of Wnt signaling is implicated in many forms of human disease including gastric cancer. We previously reported that EphA2 promotes the epithelial–mesenchymal transition through Wnt/β-catenin signaling in gastric cancer. Herein, we present a novel mechanism by which EphA2 regulates Wnt/β-catenin signaling. EphA2 acts as a receptor for Wnt ligands and recruits Axin1 to the plasma membrane by directly binding Dvl2. The EphA2-Dvl2/Axin1 interaction was enhanced by Wnt3a treatment, suggesting that EphA2 acts as a functional receptor for the Wnt/β-catenin pathway and plays a vital role in downstream signaling. We showed that Dvl2 mediates the EphA2-Axin1 interaction by binding to the tyrosine kinase domain of EphA2. We propose that EphA2/Dvl2/Axin1 forms a complex that destabilizes the β-catenin destruction complex and allows β-catenin to translocate to the nucleus and initiate the transcription of c-MYC, the primary Wnt signaling target gene. Intriguingly, c-MYC could bind directly to the EphA2 and Wnt1 promoter to enhance their transcription. The entire process formed an EphA2-mediated feed-forward loop. A small molecular inhibitor of EphA2 potently inhibited the proliferation of gastric cancer in vitro and in vivo, including gastric cancer patient–derived xenografts. Thus, our data identify EphA2 as an excellent candidate for gastric cancer therapy.

Scutellarin induces apoptosis and autophagy in NSCLC cells through ERK1/2 and AKT Signaling Pathways in vitro and in vivo

Curative molecular therapy for non-small cell lung cancer (NSCLC) is still lacking. Scutellarin, an active flavone extracted from Erigeron breviscapus Hand-Mazz, displays anti-tumor property in diverse cancer types, yet its tumor-suppressive effect on NSCLC is not reported. In this study, we found that scutellarin significantly inhibited the proliferation of NSCLC cells, induced cell apoptosis, and triggered autophagy. Notably, inhibition of autophagy with inhibitor HCQ attenuated the anti-proliferative activity of scutellarin, indicating that scutellarin-induced autophagy is antineoplastic. In addition, HCQ treatment reduced scutellarin-induced apoptosis. Further study demonstrated that scutellarin stimulated phosphorylation of ERK1/2, and inhibition of ERK1/2 with inhibitor U0126 markedly attenuated scutellarin-induced autophagy. Similarly, scutellarin downregulated the expression of p-AKT, and AKT inhibitor MK-2206 induced autophagy. Moreover, there also existed crosstalk between ERK and AKT pathways. Finally, in vivo xenograft nude mice experiment proved that scutellarin treatment significantly reduced tumor growth and increased the levels of LC3-II and p-ERK1/2, suppressed p-AKT in mice tumors. Thus, our study for the first time uncovered the anti-cancer function of scutellarin on NSCLC cells, and might provide a potential novel therapy for treatment of patients with NSCLC.

Hypermethylated gene ANKDD1A is a candidate tumor suppressor that interacts with FIH1 and decreases HIF1α stability to inhibit cell autophagy in the glioblastoma multiforme hypoxia microenvironment

Ectopic epigenetic mechanisms play important roles in facilitating tumorigenesis. Here, we first demonstrated that ANKDD1A is a functional tumor suppressor gene, especially in the hypoxia microenvironment. ANKDD1A directly interacts with FIH1 and inhibits the transcriptional activity of HIF1α by upregulating FIH1. In addition, ANKDD1A decreases the half-life of HIF1α by upregulating FIH1, decreases glucose uptake and lactate production, inhibits glioblastoma multiforme (GBM) autophagy, and induces apoptosis in GBM cells under hypoxia. Moreover, ANKDD1A is highly frequently methylated in GBM. The tumor-specific methylation of ANKDD1A indicates that it could be used as a potential epigenetic biomarker as well as a possible therapeutic target.

Coagulation Factor X Regulated by CASC2c Recruited Macrophages and Induced M2 Polarization in Glioblastoma Multiforme

Tumor-associated macrophages (TAMs) constitute a major component of inflammatory cells in the glioblastoma multiforme (GBM) tumor microenvironment. TAMs have been implicated in GBM angiogenesis, invasion, local tumor recurrence, and immunosuppression. Coagulation factor X (FX) is a vitamin K-dependent plasma protein that plays a role in the regulation of blood coagulation. In this study, we first found that FX was highly expressed and positively correlated with TAM density in human GBM. FX exhibited a potent chemotactic capacity to recruit macrophages and promoted macrophages toward M2 subtype polarization, accelerating GBM growth. FX bound to extracellular signal-related kinase (ERK)1/2 and inhibited p-ERK1/2 in GBM cells. FX was secreted in the tumor microenvironment and increased the phosphorylation and activation of ERK1/2 and AKT in macrophages, which may have been responsible for the M2 subtype macrophage polarization. Moreover, although the lncRNA CASC2c has been verified to function as a miR-101 competing endogenous RNA (ceRNA) to promote miR-101 target genes in GBM cells, we first confirmed that CASC2c did not function as a miR-338-3p ceRNA to promote FX expression, and that FX was a target gene of miR-338-3p. CASC2c interacted with and reciprocally repressed miR-338-3p. Both CASC2c and miR-388-3p bound to FX and commonly inhibited its expression and secretion. CASC2c repressed M2 subtype macrophage polarization. Taken together, our findings revealed a novel mechanism highlighting CASC2c and FX as potential therapeutic targets to improve GBM patients by altering the GBM microenvironment.

miR-519a enhances chemosensitivity and promotes autophagy in glioblastoma by targeting STAT3/Bcl2 signaling pathway

Background

Chemoresistance to temozolomide (TMZ) is a major challenge in the treatment of glioblastoma (GBM). We previously found that miR-519a functions as a tumor suppressor in glioma by targeting the signal transducer and activator of transcription 3 (STAT3)-mediated autophagy oncogenic pathway. Here, we investigated the effects of miR-519a on TMZ chemosensitivity and autophagy in GBM cells. Furthermore, the underlying molecular mechanisms and signaling pathways were explored.

Methods

In the present study, two stable TMZ-resistant GBM cell lines were successfully generated by exposure of parental cells to a gradually increasing TMZ concentration. After transfecting U87-MG/TMZ and U87-MG cells with miR-519a mimic or inhibitor, a series of biochemical assays such as MTT, apoptosis, and colony formation were performed to determine the chemosensitive response to TMZ. The autophagy levels in GBM cells were detected by transmission electron microscopy, LC3B protein immunofluorescence, and Western blotting analysis. Stable knockdown and overexpression of miR-519a in GBM cells were established using lentivirus. A xenograft nude mouse model and in situ brain model were used to examine the in vivo effects of miR-519a. Tumor tissue samples were collected from 48 patients with GBM and were used to assess the relationship between miR-519a and STAT3 expression.

Results

TMZ treatment significantly upregulated miR-519a in U87-MG cells but not in U87-MG/TMZ cells. Moreover, the expression of miR-519a and baseline autophagy levels was lower in U87-MG/TMZ cells as compared to U87-MG cells. miR-519a dramatically enhanced TMZ-induced autophagy and apoptotic cell death in U87-MG/TMZ cells, while inhibition of miR-519a promoted TMZ resistance and reduced TMZ-induced autophagy in U87-MG cells. Furthermore, miR-519a induced autophagy through modification of STAT3 expression. The in vivo results showed that miR-519a can enhance apoptosis and sensitized GBM to TMZ treatment by promoting autophagy and targeting the STAT3/Bcl-2/Beclin-1 pathway. In human GBM tissues, we found an inverse correlation between miR-519a and STAT3 expression.

Conclusions

Our results suggested that miR-519a increased the sensitivity of GBM cells to TMZ therapy. The positive effects of miR-519a may be mediated through autophagy. In addition, miR-519a overexpression can induce autophagy by inhibiting STAT3/Bcl-2 pathway. Therefore, a combination of miR-519a and TMZ may represent an effective therapeutic strategy in GBM.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0618-0) contains supplementary material, which is available to authorized users.

Circular RNA hsa-circ-0012129 Promotes Cell Proliferation and Invasion in 30 Cases of Human Glioma and Human Glioma Cell Lines U373, A172, and SHG44, by Targeting MicroRNA-661 (miR-661)

Background

Circular RNA (circRNA) is a stable non-coding RNA without 5′-3′ polarity and without a poly-A tail, that contains response elements for microRNAs (miRNAs) such as miR-661. There have previously been few reported studies on the role of circRNAs in glioma. The aim of this study was to investigate the effects of the expression of the circRNA, hsa-circ-0012129, and miR-661 in human glioma tissue and human glioma cell lines.

Material/Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of hsa-circ-0012129 and miR-661 in glioma tissues from 31 patients (WHO grades I–IV), compared with adjacent normal tissue, and in human glioma cell lines, U373, A172, and SHG44, compared with the normal human astrocyte cell line, NHA. The MTT assay, colony formation assay, transwell and wound scratch assays were performed to analyze and compare cell viability, cell migration, and invasion.

Results

Expression of hsa-circ-0012129 was significantly increased in glioma tissues and cell lines; hsa-circ-0012129 knockdown significantly suppressed the proliferation, migration, and invasion abilities of U373 and SHG44 cells. A dual-luciferase reporter assay showed that hsa-circ-0012129 contained the complementary binding region with miR-661 and that hsa-circ-0012129 expression negatively regulated miR-661. Rescue experiments showed that miR-661 could reverse the effects of hsa-circ-0012129 on cell viability, cell migration and invasion of glioma cells in vitro.

Conclusions

The findings of this study indicated that, in human glioma cells, the circRNA, hsa-circ-0012129 might act as a natural miR-661 sponge, and that miR-661 could have suppressive effects on the expression of circ-0012129.

Therapeutic approach in glioblastoma multiforme with primitive neuroectodermal tumor components: Case report and review of the literature

Glioblastoma multiforme (GBM) is the most common and aggressive malignant glioma that is treated with first-line therapy, using surgical resection followed by local radiotherapy and concomitant/adjuvant temozolomide (TMZ) treatment. GBM is characterised by a high local recurrence rate and a low response to therapy. Primitive neuroectodermal tumour (PNET) of the brain revealed a low local recurrence rate; however, it also exhibited a high risk of cerebrospinal fluid (CSF) dissemination. PNET is treated with surgery followed by craniospinal irradiation (CSI) and platinum-based chemotherapy in order to prevent CSF dissemination. GBM with PNET-like components (GBM/PNET) is an emerging variant of GBM, characterised by a PNET-like clinical behaviour with an increased risk of CSF dissemination; it also may benefit from platinum-based chemotherapy upfront or following failure of GBM therapy. The results presented regarding the management of GBM/PNET are based on case reports or case series, so a standard therapeutic approach for GBM/PNET is not defined, constituing a challenging diagnostic and therapeutic dilemma. In this report, a case of a recurrent GBM/PNET treated with surgical resection and radiochemotherapy as Stupp protocol, and successive platinum-based chemotherapy due to the development of leptomeningeal dissemintation and an extracranial metastasis, is discussed. A review of the main papers regarding this rare GBM variant and its therapeutic approach are also reported. In conclusion, GBM/PNET should be treated with a multimodal approach including surgery, chemoradiotherapy, and/or the early introduction of CSI and platinum-based chemotherapy upfront or at recurrence.

Novel Therapy for Glioblastoma Multiforme by Restoring LRRC4 in Tumor Cells: LRRC4 Inhibits Tumor-Infitrating Regulatory T Cells by Cytokine and Programmed Cell Death 1-Containing Exosomes

Glioblastoma multiforme (GBM) is a heterogeneous malignant brain tumor, the pathological incidence of which induces the accumulation of tumor-infiltrating lymphocytes (TILs). As a tumor suppressor gene, LRRC4 is absent in GBM cells. Here, we report that the recovery of LRRC4 in GBM cells inhibited the infiltration of tumor-infiltrating regulatory T cells (Ti-Treg), promoted the expansion of tumor-infiltrating effector T (Ti-Teff) cells and CD4⁺CCR4⁺ T cells, and enhanced the chemotaxis of CD4⁺CCR4⁺ T cells in the GBM immune microenvironment. LRRC4 was not transferred into TILs from GBM cells through exosomes but mainly exerted its inhibiting function on Ti-Treg cell expansion by directly promoting cytokine secretion. GBM cell-derived exosomes (cytokine-free and programmed cell death 1 containing) also contributed to the modulation of LRRC4 on Ti-Treg, Ti-Teff, and CD4⁺CCR4⁺ T cells. In GBM cells, LRRC4 directly bound to phosphoinositide-dependent protein kinase 1 (PDPK1), phosphorylated IKKβser181, facilitated NF-κB activation, and promoted the secretion of interleukin-6 (IL-6), CCL2, and interferon gamma. In addition, HSP90 was required to maintain the interaction between LRRC4 and PDPK1. However, the inhibition of Ti-Treg cell expansion and promotion of CD4⁺CCR4⁺ T cell chemotaxis by LRRC4 could be blocked by anti-IL-6 antibody or anti-CCL2 antibody, respectively. miR-101 is a suppressor gene in GBM. Our previous studies have shown that EZH2, EED, and DNMT3A are direct targets of miR-101. Here, we showed that miR-101 reversed the hypermethylation of the LRRC4 promoter and induced the re-expression of LRRC4 in GBM cells by directly targeting EZH2, EED, and DNMT3A. Our results reveal a novel mechanism underlying GBM microenvironment and provide a new therapeutic strategy using re-expression of LRRC4 in GBM cells to create a permissive intratumoral environment.

High expression of Bruton's tyrosine kinase (BTK) is required for EGFR-induced NF-κB activation and predicts poor prognosis in human glioma

BACKGROUND

Malignant glioma is the most common primary brain tumor in adults and has a poor prognosis. However, there are no effective targeted therapies for glioma patients. Thus, the development of novel targeted therapeutics for glioma is urgently needed.

METHODS

In this study, we examined the prognostic significance BTK expression in patients with glioma. Furthermore, we investigated the mechanism and therapeutic potential of ibrutinib in the treatment of human glioma in vitro and in vivo.

RESULTS

Our data demonstrate that high expression of BTK is a novel prognostic marker for poor survival in patients with glioma. BTK-specific inhibitor ibrutinib effectively inhibits the proliferation, migration and invasion ability of glioma cells. Furthermore, ibrutinib can induce G1 cell-cycle arrest by regulating multiple cell cycle-associated proteins. More importantly, we found that BTK inhibition significantly blocks the degradation of IκBα and prevents the nuclear accumulation of NF-κB p65 subunit induced by EGF in glioma cells.

CONCLUSIONS

Taken together, our study suggests that BTK is a novel prognostic marker and molecular therapeutic target for glioma. BTK is required for EGFR-induced NF-κB activation in glioma cells. These findings provide the basis for future clinical studies of ibrutinib for the treatment of glioma.

SSRP1 silencing inhibits the proliferation and malignancy of human glioma cells via the MAPK signaling pathway

Structure-specific recognition protein 1 (SSRP1) has been considered as a potential biomarker, since aberrant high expression of SSRP1 has been detected in numerous malignant tumors. However, the correlation between the expression level of SSRP1 and glioma remains unclear. The present study attempted to investigate the role of SSRP1 in the pathogenesis of glioma. In the present study, our data revealed that SSRP1 overexpression was detected in glioma tissues at both the mRNA and protein levels using quantitative real-time RT-PCR and immunohistochemical analysis. We also demonstrated that the upregulated expression of SSRP1 was correlated with the World Health Organization (WHO) grade of glioma. The knockdown of SSRP1 by siRNA not only resulted in the inhibition of cell proliferation, but also significantly inhibited glioma cell migration and invasion. Mechanistic analyses revealed that SSRP1 depletion suppressed the activity of the phosphorylation of the MAPK signaling pathway. In conclusion, the present study indicated that SSRP1 regulated the proliferation and metastasis of glioma cells via the MAPK signaling pathway.

SIX3, a tumor suppressor, inhibits astrocytoma tumorigenesis by transcriptional repression of AURKA/B

BACKGROUND

SIX homeobox 3 (SIX3) is a member of the sine oculis homeobox transcription factor family. It plays a vital role in the nervous system development. Our previous study showed that the SIX3 gene is hypermethylated, and its expression is decreased in astrocytoma, but the role of SIX3 remains unknown.

METHODS

Chromatin-immunoprecipitation (ChIP) and luciferase reporter assay were used to confirm the binding of SIX3 to the promoter regions of aurora kinase A (AURKA) and aurora kinase B (AURKB). Confocal imaging and co-immunoprecipitation (Co-IP) were used to detect the interaction between AURKA and AURKB. Flow cytometry was performed to assess the effect of SIX3 on cell cycle distribution. Colony formation, EdU incorporation, transwell, and intracranial xenograft assays were performed to demonstrate the effect of SIX3 on the malignant phenotype of astrocytoma cells.

RESULTS

SIX3 is identified as a novel negative transcriptional regulator of AURKA and AURKB, and it decreases the expression of AURKA and AURKB in a dose-dependent manner in astrocytoma cells. Importantly, interactions between AURKA and AURKB stabilize and protect AURKA/B from degradation, and overexpression of SIX3 does not affect these interactions; SIX3 also acts as a tumor suppressor, and it increases p53 activity and expression at the post-translational level by the negative regulation of AURKA or AURKB, reduces the events of numerical centrosomal aberrations and misaligned chromosomes, and significantly inhibits the proliferation, invasion, and tumorigenesis of astrocytoma in vitro and in vivo. Moreover, experiments using primary cultured astrocytoma cells indicate that astrocytoma patients with a low expression of SIX3 and mutant p53 are more sensitive to treatment with aurora kinase inhibitors.

CONCLUSION

SIX3 is a novel negative transcriptional regulator and acts as a tumor suppressor that directly represses the transcription of AURKA and AURKB in astrocytoma. For the first time, the functional interaction of AURKA and AURKB has been found, which aids in the protection of their stability, and partially explains their constant high expression and activity in cancers. SIX3 is a potential biomarker that could be used to predict the response of astrocytoma patients to aurora kinase inhibitors.

TTBK2 circular RNA promotes glioma malignancy by regulating miR-217/HNF1β/Derlin-1 pathway

BACKGROUND

Circular RNAs are a subgroup of non-coding RNAs and generated by a mammalian genome. Herein, the expression and function of circular RNA circ-TTBK2 were investigated in human glioma cells.

METHODS

Fluorescence in situ hybridization and quantitative real-time PCR were conducted to profile the cell distribution and expression of circ-TTBK2 and microRNA-217 (miR-217) in glioma tissues and cells. Immunohistochemical and western blot were used to determine the expression of HNF1β and Derlin-1 in glioma tissues and cells. Stable knockdown of circ-TTBK2 or overexpression of miR-217 glioma cell lines (U87 and U251) were established to explore the function of circ-TTBK2 and miR-217 in glioma cells. Further, luciferase reports and RNA immunoprecipitation were used to investigate the correlation between circ-TTBK2 and miR-217. Cell Counting Kit-8, transwell assays, and flow cytometry were used to investigate circ-TTBK2 and miR-217 function including cell proliferation, migration and invasion, and apoptosis, respectively. ChIP assays were used to ascertain the correlations between HNF1β and Derlin-1.

RESULTS

We found that circ-TTBK2 was upregulated in glioma tissues and cell lines, while linear TTBK2 was not dysregulated in glioma tissues and cells. Enhanced expression of circ-TTBK2 promoted cell proliferation, migration, and invasion, while inhibited apoptosis. MiR-217 was downregulated in glioma tissues and cell lines. We also found that circ-TTBK2, but not linear TTBK2, acted as miR-217 sponge in a sequence-specific manner. In addition, upregulated circ-TTBK2 decreased miR-217 expression and there was a reciprocal negative feedback between them in an Argonaute2-dependent manner. Moreover, reintroduction of miR-217 significantly reversed circ-TTBK2-mediated promotion of glioma progression. HNF1β was a direct target of miR-217, and played oncogenic role in glioma cells. Remarkably, circ-TTBK2 knockdown combined with miR-217 overexpression led to tumor regression in vivo.

CONCLUSIONS

These results demonstrated a novel role circ-TTBK2 in the glioma progression.