Effect of CCL2 siRNA on proliferation and apoptosis in the U251 human glioma cell line

Neutrophil infiltration associated genes on the prognosis and tumor immune microenvironment of lung adenocarcinoma

The neutrophils exhibit both anti-tumor and pro-tumor effects in cancers. The correlation between neutrophils and tumor development in lung adenocarcinoma (LUAD) is still uncertain, possibly due to a lack of specific neutrophil infiltration evaluation methods. In this study, we identified 30 hub genes that were significantly associated with neutrophil infiltration in LUAD through data mining, survival analysis, and multiple tumor-infiltrating immune cells (TICs) analysis, including TIMER, CIBERSORT, QUANTISEQ, XCELL, and MCPCOUNTER. Consensus clustering analysis showed that these 30 hub genes were correlated with clinical features in LUAD. We further developed a neutrophil scoring system based on these hub genes. The neutrophil score was significantly correlated with prognosis and tumor immune microenvironment (TIME) in LUAD. It was also positively associated with PD-L1 expression and negatively associated with tumor mutational burden (TMB). When combined with the neutrophil score, the predictive capacity of PD-L1 and TMB for prognosis was significantly improved. Thus, the 30 hub genes might play an essential role in the interaction of neutrophils and LUAD, and the neutrophil scoring system might effectually assess the infiltration of neutrophils. Furthermore, we verified the expression of these 30 genes in the LUAD tumor tissues collected from our department. We further found that overexpressed TNFAIP6 and TLR6 and downregulated P2RY13, SCARF1, DPEP2, PRAM1, CYP27A1, CFP, GPX3, and NCF1 in LUAD tissue might be potentially associated with neutrophils pro-tumor effects. The following in vitro experiments demonstrated that TNFAIP6 and TLR6 were significantly overexpressed, and P2RY13 and CYP27A1 were significantly downregulated in LUAD cell lines, compared to BEAS-2B cells. Knocking down TNFAIP6 in A549 and PC9 resulted in the upregulation of FAS, CCL3, and ICAM-1, and the downregulation of CCL2, CXCR4, and VEGF-A in neutrophils when co-culturing with the conditioned medium (CM) from LUAD cells. Knocking down TNFAIP6 in LUAD also led to an elevated early apoptosis rate of neutrophils. Therefore, overexpressed TNFAIP6 in LUAD cancer cells might lead to neutrophils "N2" polarization, which exhibited pro-tumor effects. Further research based on the genes identified in this pilot study might shed light on neutrophils' effects on LUAD in the future.

Promising Modulatory Effects of Cenicriviroc on the Progression of Mouse Colorectal Cancer through Inhibition of CCR2_CCL2 Signaling Pathway

The study was designed to assay the efficacy of cenicriviroc (CVC) on the progression of mouse colorectal cancer by downregulation of CCR2_CCL2. In this study, CVC was used to inhibit the CCR2 receptor. Next, an MTT assay was performed to evaluate the cytotoxic effects of CVC on the CT26 cell line. CT26 cells were implanted subcutaneously in BALB/c mice. After tumor implantation, one group of animals received 20 mg/kg of CVC several times. The mRNA levels of CCR2, CCL2, VEGF, NF-κB, c-Myc, vimentin, and IL33 were determined in the CT26 cell line and then tumor tissues (after 21 days), by qRT-PCR. Protein levels of the above-mentioned targets were determined by western blot and ELISA. Flow cytometry was performed to assess the changes in apoptosis. Tumor growth inhibition was measured on the 1st, 7th, and 21st days after the first treatment. In both cell line and tumor cells treated with CVC, expression levels of the markers of our interest in mRNA and protein levels were significantly reduced compared to controls. A significantly higher apoptotic index was observed in CVC-treated groups. The rates of tumor growth were significantly decreased on the 7th and 21st days after the first injection. To our knowledge, this was the first time that we demonstrated the promising effect of CVC on the development of CRC through inhibition of the CCR2_CCL2 signaling and its downstream biomarkers.

Recent Emerging Immunological Treatments for Primary Brain Tumors: Focus on Chemokine-Targeting Immunotherapies

Primary brain tumors are a leading cause of death worldwide and are characterized by extraordinary heterogeneity and high invasiveness. Current drug and radiotherapy therapies combined with surgical approaches tend to increase the five-year survival of affected patients, however, the overall mortality rate remains high, thus constituting a clinical challenge for which the discovery of new therapeutic strategies is needed. In this field, novel immunotherapy approaches, aimed at overcoming the complex immunosuppressive microenvironment, could represent a new method of treatment for central nervous system (CNS) tumors. Chemokines especially are a well-defined group of proteins that were so named due to their chemotactic properties of binding their receptors. Chemokines regulate the recruitment and/or tissue retention of immune cells as well as the mobilization of tumor cells that have undergone epithelial–mesenchymal transition, promoting tumor growth. On this basis, this review focuses on the function and involvement of chemokines and their receptors in primary brain tumors, specifically examining chemokine-targeting immunotherapies as one of the most promising strategies in neuro-oncology.

Gold nanoparticles enhances radiosensitivity in glioma cells by inhibiting TRAF6/NF-κB induced CCL2 expression

Gliomas are inherently difficult to treat by radiotherapy because glioma cells become radioresistant over time. However, combining radiotherapy with a radiosensitizer could be an effective strategy to mitigate the radioresistance of glioma cells. Gold nanoparticles (AuNPs) have emerged as a promising nanomaterial for cancer therapy, but little is known about whether AuNPs and X-ray radiation have cytotoxic synergistic effects against tumors. In this study, we found that the combination of AuNPs and X-ray irradiation significantly reduced the viabilities, as well as the migration and invasion, of glioma cells. Mechanistically, we observed that the AuNPs inhibited radiation-induced CCL2 expression by inhibiting the TRAF6/NF-κB pathway, which likely manifested the synergistic therapeutic effect between the AuNPs and X-ray radiation. The AuNPs also re-sensitized radioresistant glioma cells by inhibiting CCL2 expression. These results were also observed in another tumor cell line with a different molecular pattern, indicating that the underlying mechanism may be ubiquitous through cancer cells. Lastly, using the glioma mouse model, we observed that AuNPs significantly reduced tumor growth in the presence of X-ray radiation compared to radiotherapy alone.

CCL2 activates AKT signaling to promote glycolysis and chemoresistance in glioma cells

The incidence of gliomas is increasing. Although great progress in glioma treatment has been made, the clinical outcome remains unsatisfactory. Chemokine (C-C motif) ligand 2 (CCL2) plays a key role in different types of cancers, including glioma. However, the function of CCL2 in glioma chemoresistance is not fully understood. In the current study, CCL2 was significantly upregulated in glioma. More importantly, CCL2 and CCR2 were significantly upregulated in temozolomide (TMZ)-resistant glioma. TMZ-resistant malignant glioblastoma cells (U251/TMZ) had higher expressions of CCL2 and CCR2 and a higher level of glycolysis as compared to its parental cell line U251. Silencing of CCL2 in U251/TMZ cells inhibited glycolysis. Overexpression of CCL2 reduced TMZ-induced apoptosis through activation of the AKT pathway and promotion of glycolysis. Moreover, overexpression of CCL2 significantly reduced the antitumor effect of TMZ in vivo. In conclusion, CCL2 overexpression reduced the antitumor effect of TMZ by enhancing glycolysis through activation of AKT signaling. The findings highlighted the importance of CCL2/CCR2/glycolysis and its potential value i developing new treatment for glioma. This article is protected by copyright. All rights reserved.

Diosmin Inhibits Glioblastoma Growth through Inhibition of Autophagic Flux

Diosmin, a natural flavone glycoside acquired through dehydrogenation of the analogous flavanone glycoside hesperidin, is plentiful in many citrus fruits. Glioblastoma multiforme (GBM) is the most malignant primary brain tumor; the average survival time of GBM patients is less than 18 months after standard treatment. The present study demonstrated that diosmin, which is able to cross the blood-brain barrier, inhibited GBM cell growth in vitro and in vivo. Diosmin also impeded migration and invasion by GBM8401and LN229 GBM cells by suppressing epithelial-mesenchymal transition, as indicated by increased expression of E-cadherin and decreased expression of Snail and Twist. Diosmin also suppressed autophagic flux, as indicated by increased expression of LC3-II and p62, and induced cell cycle arrest at G1 phase. Importantly, diosmin did not exert serious cytotoxic effects toward control SVG-p12 astrocytes, though it did reduce astrocyte viability at high concentrations. These findings provide potentially helpful support to the development of new therapies for the treatment of GBM.

A comprehensive prognostic signature for glioblastoma patients based on transcriptomics and single cell sequencing

PURPOSE

Glioblastoma (GBM) is the most common and deadly brain tumor. We aimed to reveal potential prognostic GBM marker genes, elaborate their functions, and build an effective a prognostic model for GBM patients.

METHODS

Through data mining of The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA), we screened for significantly differentially expressed genes (DEGs) to calculate risk scores for individual patients. Published data of somatic mutation and copy number variation profiles were analyzed for distinct genomic alterations associated with risk scores. In addition, single-cell sequencing was used to explore the biological functions of the identified prognostic marker genes. By combining risk scores and other clinical features, we built a comprehensive prognostic GBM model.

RESULTS

Seven DEGs (CLEC5A, HOXC6, HOXA5, CCL2, GPRASP1, BSCL2 and PTX3) were identified as being prognostic for GBM. Expression of these genes was confirmed in different GBM cell lines using real-time PCR. Risk scores calculated from the seven DEGs revealed prognostic value irrespective of other clinical factors, including IDH mutation status, and were negatively correlated with TP53 expression. The prognostic genes were found to be associated with tumor proliferation and progression based on pseudo-time analysis in neoplastic cells. A final prognostic model was developed and validated with a good performance, especially in geriatric GBM patients.

CONCLUSIONS

Using genetic profiles, age, IDH mutation status, and chemotherapy and radiotherapy, we constructed a comprehensive prognostic model for GBM patients. The model has a good performance, especially in geriatric GBM patients.

Tumor‐associated macrophages as treatment targets in glioma

Gliomas, the most common primary tumors in the central nervous system (CNS), can be categorized into 4 grades according to the World Health Organization. The most malignant glioma type is grade Ⅳ, also named glioblastoma multiforme (GBM). However, the standard treatment of concurrent temozolomide (TMZ) chemotherapy and radiotherapy after maximum resection does not improve overall survival in patients with GBM. Targeting components of the CNS microenvironment represents a new strategy for improving the efficacy of glioma treatment. Most recent studies focused on T cells. However, there is a growing body of evidence that tumor‐associated macrophages (TAMs) play an important role in tumor progression and can be regulated by a wide array of cytokines or chemokines. New TAM‐associated immunotherapies may improve clinical outcomes by blocking tumor progression and prolonging survival. However, understanding the exact roles and possible mechanisms of TAMs in the tumor environment is necessary for developing this promising therapeutic target and identifying potential diagnostic markers for improved prognosis. This review summarizes the possible interactions between TAMs and glioma progression and discusses the potential therapeutic directions for TAM‐associated immunotherapies.

MEX3A contributes to development and progression of glioma through regulating cell proliferation and cell migration and targeting CCL2

Glioma is one of the most commonly diagnosed intracranial malignant tumors with extremely high morbidity and mortality, whose treatment was seriously limited because of the unclear molecular mechanism. In this study, in order to identify a novel therapeutic target for glioma treatment, we explored the functions and mechanism of MEX3A in regulating glioma. The immunohistochemical staining of MEX3A in glioma and normal tissues revealed the upregulation of MEX3A and further indicated the relationship between high MEX3A expression and higher malignancy as well as poorer prognosis of glioma. In vitro loss-of-function and gain-of-function experiments comprehensively demonstrated that MEX3A may promote glioma development through regulating cell proliferation, cell apoptosis, cell cycle, and cell migration. In vivo experiments also suggested the inhibition of glioma growth by MEX3A knockdown. Moreover, our mechanistic study identifies CCL2 as a potential downstream target of MEX3A, which possesses similar regulatory effects on glioma development with MEX3A and could attenuate the promotion of glioma induced by MEX3A overexpression. Overall, MEX3A was identified as a potential tumor promoter in glioma development and therapeutic target in glioma treatment.

Versatile Role of Rab27a in Glioma: Effects on Release of Extracellular Vesicles, Cell Viability, and Tumor Progression

Introduction: Glioma cells exert influence over the tumor-microenvironment in part through the release of extracellular vesicles (EVs), membrane-enclosed structures containing proteins, lipids, and RNAs. In this study, we evaluated the function of Ras-associated protein 27a (Rab27a) in glioma and evaluated the feasibility of assessing its role in EV release in glioma cells in vitro and in vivo. Methods: Rab27a was knocked down via a short hairpin RNA (shRNA) stably expressed in mouse glioma cell line GL261, with a scrambled shRNA as control. EVs were isolated by ultracentrifugation and quantified with Nanoparticle Tracking Analysis (NTA) and Tunable Resistive Pulse Sensing (TRPS). CellTiter-Glo viability assays and cytokine arrays were used to evaluate the impact of Rab27a knockdown. GL261.shRab27a cells and GL261.shControl were implanted into the left striatum of eight mice to assess tumor growth and changes in the tumor microenvironment. Results: Knockdown of Rab27a in GL261 glioma cells decreased the release of small EVs isolated at 100,000 × g in vitro (p = 0.005), but not the release of larger EVs, isolated at 10,000 × g. GL261.shRab27a cells were less viable compared to the scramble control in vitro (p < 0.005). A significant increase in CCL2 expression in shRab27a GL261 cells was also observed (p < 0.001). However, in vivo there was no difference in tumor growth or overall survival between the two groups, while shRab27a tumors showed lower proliferation at the tumor borders. Decreased infiltration of IBA1 positive macrophages and microglia, but not FoxP3 positive regulatory T cells was observed. Conclusion: Rab27a plays an important role in the release of small EVs from glioma cells, and also in their viability and expression of CCL2 in vitro. As interference in Rab27a expression influences glioma cell viability and expression profiles, future studies should be cautious in using the knockdown of Rab27a as a means of studying the role of small EVs in glioma growth.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of the Ligands of Receptors CCR1, CCR2, CCR3, and CCR4

CC chemokines, a subfamily of 27 chemotactic cytokines, are a component of intercellular communication, which is crucial for the functioning of the tumor microenvironment. Although many individual chemokines have been well researched, there has been no comprehensive review presenting the role of all known human CC chemokines in the hallmarks of cancer, and this paper aims at filling this gap. The first part of this review discusses the importance of CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 in cancer. Here, we discuss the significance of CCL2 (MCP-1), CCL7, CCL8, CCL11, CCL13, CCL14, CCL15, CCL16, CCL17, CCL22, CCL23, CCL24, and CCL26. The presentation of each chemokine includes its physiological function and then the role in tumor, including proliferation, drug resistance, migration, invasion, and organ-specific metastasis of tumor cells, as well as the effects on angiogenesis and lymphangiogenesis. We also discuss the effects of each CC chemokine on the recruitment of cancer-associated cells to the tumor niche (eosinophils, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), tumor-associated neutrophils (TAN), regulatory T cells (T_reg)). On the other hand, we also present the anti-cancer properties of CC chemokines, consisting in the recruitment of tumor-infiltrating lymphocytes (TIL).

Epithelial-stromal communication via CXCL1-CXCR2 interaction stimulates growth of ovarian cancer cells through p38 activation

PURPOSE

Paracrine interactions with the stromal environment, including fibroblasts, may be important in the pathogenesis of ovarian cancer. Here, we evaluated the effect of conditioned media derived from ovarian fibroblasts (fibroblast-CMs) and their major cytokines on the growth of ovarian cancer cells, as well as the involvement of mitogen-activated protein kinases (MAPKs) and AKT in mediating this effect.

METHODS

Ovarian cancer cells were cultured in serum-free media (SF), or conditioned media of fibroblasts derived from normal ovary (CM1) and ovarian tumor tissue (CM2). Cell proliferation was measured by MTT assay. Phosphorylation of MAPKs and AKT was evaluated by Western blotting. Specific inhibitors of MAPKs and AKT were used to evaluate their respective involvement in mediating increased cell growth. Cytokine levels in fibroblast-CMs were measured using Luminex assays. Immunohistochemical staining was conducted for CXCL1, CXCR2 and phosphorylated p38 in primary ovarian tumors.

RESULTS

CM1 and CM2 significantly increased the growth of ovarian cancer cells relative to SF. In OVCAR3 and OVCAR4 cells, p38 phosphorylation was strongly induced by fibroblast-CMs, and pre-treatment with a p38 inhibitor prevented the growth increase induced by fibroblast-CMs. Fibroblasts secreted high levels of IL-6, IL-8, MCP1 and CXCL1. Treatment with only CXCL1 (1 μg/ml) increased cell growth and p38 phosphorylation. Treatment with a CXCR2 inhibitor effectively prevented p38 activation and cell growth induced by fibroblast-CMs. High expression of both CXCL1 and CXCR2 correlated with high expression of phosphorylated p38 in primary ovarian tumors.

CONCLUSIONS

From our data, we conclude that CXCL1 is a key factor derived from ovarian fibroblasts that is responsible for increased ovarian cancer cell growth in part through p38 activation. Phosphorylated p38 can be used as a biomarker to predict CXCL1-CXCR2 interaction in vivo.

Third Ventricular Injection of CCL2 in Rat Embryo Stimulates CCL2/CCR2 Neuroimmune System in Neuroepithelial Radial Glia Progenitor Cells: Relation to Sexually Dimorphic, Stimulatory Effects on Peptide Neurons in Lateral Hypothalamus

Clinical and animal studies show maternal alcohol consumption during pregnancy causes in offspring persistent alterations in neuroimmune and neurochemical systems known to increase alcohol drinking and related behaviors. Studies in lateral hypothalamus (LH) demonstrate in adolescent offspring that maternal oral administration of ethanol stimulates the neuropeptide, melanin-concentrating hormone (MCH), together with the inflammatory chemokine C-C motif ligand 2 (CCL2) and its receptor CCR2 which are increased in most MCH neurons. These effects, consistently stronger in females than males, are detected in embryos, not only in LH but hypothalamic neuroepithelium (NEP) along the third ventricle where neurons are born and CCL2 is stimulated within radial glia progenitor cells and their laterally projecting processes that facilitate MCH neuronal migration toward LH. With ethanol's effects similarly produced by maternal peripheral CCL2 administration and blocked by CCR2 antagonist, we tested here using in utero intracerebroventricular (ICV) injections whether CCL2 acts locally within the embryonic NEP. After ICV injection of CCL2 (0.1 µg/µl) on embryonic day 14 (E14) when neurogenesis peaks, we observed in embryos just before birth (E19) a significant increase in endogenous CCL2 within radial glia cells and their processes in NEP. These auto-regulatory effects, evident only in female embryos, were accompanied by increased density of CCL2 and MCH neurons in LH, more strongly in females than males. These results support involvement of embryonic CCL2/CCR2 neuroimmune system in radial glia progenitor cells in mediating sexually dimorphic effects of maternal challenges such as ethanol on LH MCH neurons that colocalize CCL2 and CCR2.

Integrated Analysis to Evaluate the Prognostic Value of Signature mRNAs in Glioblastoma Multiforme

Background

Gliomas are the most common intracranial tumors and are classified as I-IV. Among them, glioblastoma multiforme (GBM) is the most common invasive glioma with a poor prognosis. New molecular biomarkers that can predict clinical outcomes in GBM patients must be identified, which will help comprehend their pathogenesis and supply personalized treatment. Our research revealed four powerful survival indicators in GBM by reanalyzing microarray data and genetic sequencing data in public databases. Moreover, it unraveled new potential therapeutic targets which could help improve the survival time and quality of life of GBM patients.

Materials and Methods

To identify prognostic signatures in GBMs, we analyzed the gene profiling data of GBM and standard brain samples from the Gene Expression Omnibus, including four datasets and RNA sequencing data from The Cancer Genome Atlas (TCGA) containing 152 glioblastoma tissues. We performed the differential analysis, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, weighted gene co-expression network analysis (WGCNA) and Cox regression analysis.

Results

After differential analysis in GSE12657, GSE15824, GSE42656 and GSE50161, overlapping differentially expressed genes were identified. We identified 110 up-regulated DEGs and 75 down-regulated DEGs in the GBM samples. Significantly enriched subclasses of the GO classification of these genes included mitotic sister chromatid separation, mitotic nuclear division and so on. In KEGG pathway analysis, the most abundant terms were ECM-receptor interaction and protein digestion and absorption. WGCNA analysis was performed on these 185 DEGs in 152 glioblastoma samples obtained from TCGA, and gene co-expression networks were constructed. We then performed a multivariate Cox analysis and established a Cox proportional hazards regression model using the top 20 genes significantly correlated with survival time. We identified a four-protein prognostic signature that could divide patients into high-risk and low-risk groups. Increased expression of SLC12A5, CCL2, IGFBP2, and PDPN was associated with increased risk scores. Finally, the K-M curves confirmed that these genes could be used as independent predictors of survival in patients with glioblastoma.

Conclusion

Our analytical study identified a set of potential biomarkers that could predict survival and may contribute to successful treatment of GBM patients.

MicroRNA-6852 suppresses glioma A172 cell proliferation and invasion by targeting LEF1

microRNA (miR)-6852 has been demonstrated to suppress the progression of gastric, colorectal and cervical cancer. The mechanism by which miR-6852 regulates glioma cells is yet to be elucidated. In the present study, reverse transcription-quantitative PCR analysis was used and the results demonstrated that miR-6852 expression was reduced in glioma tissues and cells. Cell counting kit-8 and transwell assay analysis indicated that proliferation, migration and invasion of A172 cells in the miR-6852 mimic group were lower than in the miR-NC group. Compared with the Inh-NC group, A172 cells of the Inh-miR-6852 group exhibited higher proliferation, migration and invasion. Additionally, the results indicated that lymphoid enhancer binding factor 1 (LEF1) was directly inhibited by miR-6852 and LEF1 expression was negatively correlated with miR-6852 expression in glioma tissues. Furthermore, the restoration of LEF1 reversed the effects of the miR-6852 mimics. The present findings suggested that miR-6852 inhibited glioma cells proliferation, migration and invasion by targeting the suppression of LEF1.

3D-Bioprinted Mini-Brain: A Glioblastoma Model to Study Cellular Interactions and Therapeutics

Glioblastoma-associated macrophages (GAMs) play a crucial role in the progression and invasiveness of glioblastoma multiforme (GBM); however, the exact crosstalk between GAMs and glioblastoma cells is not fully understood. Furthermore, there is a lack of relevant in vitro models to mimic their interactions. Here, novel 3D-bioprinted mini-brains consisting of glioblastoma cells and macrophages are presented as tool to study the interactions between these two cell types and to test therapeutics that target this interaction. It is demonstrated that in the mini-brains, glioblastoma cells actively recruit macrophages and polarize them into a GAM-specific phenotype, showing clinical relevance to transcriptomic and patient survival data. Furthermore, it is shown that macrophages induce glioblastoma cell progression and invasiveness in the mini-brains. Finally, it is demonstrated how therapeutics can inhibit the interaction between GAMs and tumor cells resulting in reduced tumor growth and more sensitivity to chemotherapy. It is envisioned that this 3D-bioprinted tumor model is used to improve the understanding of tumor biology and for evaluating novel cancer therapeutics.

Human telomerase reverse transcriptase recruits the β-catenin/TCF-4 complex to transactivate chemokine (C-C motif) ligand 2 expression in colorectal cancer

BACKGROUND AND AIM

Various molecular mechanisms are involved in the pathogenesis of colorectal cancer (CRC), one of the leading fatal diseases. Although human telomerase reverse transcriptase (hTERT) is critical in promoting CRC development, its regulatory mechanism is still elusive. Chemokine (C-C motif) ligand 2 (CCL2) is important to CRC pathogenesis, but the upstream regulation of CCL2 requires further investigation. Therefore, we aim to investigate the crosstalk mechanism between hTERT and CCL2 and its involvement in the pathogenesis of CRC.

METHODS

The expression relationship between hTERT and CCL2 was verified in CRC and adjacent tissues by immunohistochemistry. Lentiviruses or plasmids were used to regulate hTERT and CCL2 expression. The roles of hTERT and CCL2 in cell growth and migration were studied using CCK8 and transwell assays. The interaction between hTERT and CCL2 was detected by a luciferase reporter assay, immunofluorescence and ChIP assays. The β-catenin/TCF-4 complex was confirmed by COIP.

RESULTS

Both hTERT and CCL2 expression levels were markedly increased in CRC tissues compared to the adjacent stroma. Moreover, myeloid-derived suppressor cells (MDSCs) were found in tumor areas with higher expression levels of hTERT and CCL2. hTERT promoted HCT116 cell migration and invasion by increasing CCL2 expression. Mechanistically, ectopic hTERT facilitated the nuclear translocation of canonical β-catenin and the formation of a complex with downstream effector TCF-4, which eventually activated the CCL2 promoter.

CONCLUSIONS

hTERT may promote CRC by recruiting β-catenin/TCF-4 complex to transactivate CCL2 expression, which is a novel crosstalk mechanism likely involved in the pathogenesis of CRC.

Effects of valproic acid on the susceptibility of human glioma stem cells for TMZ and ACNU

To investigate the effect of valproic acid (VPA) on the susceptibility of glioma stem cells to temozolomide (TMZ) and nimustine (ACNU), the O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation and its expression of MGMT were examined. A total of 3 glioma cell populations were isolated from human glioma tissues, and immunocytochemistry was used to detect the expression of MGMT. VPA inhibition on the growth of the 3 glioma cell populations exposed to various concentrations of TMZ and ACNU was evaluated. Flow cytometry was applied to detect the apoptosis of glioma cells, and a methylation-specific polymerase chain reaction was used to identify methylation of MGMT promoter. Immunocytochemistry results indicated that MGMT was negatively expressed in the G1 population, but positively expressed in the G2 and G3 populations. Cell growth inhibition assays demonstrated that the survival rate in the VPA + TMZ or ACNU groups was decreased compared with that of the TMZ or ACNU alone groups (P<0.05). As for the apoptotic rate, those in the VPA alone group were increased compared with the control group (P<0.05), and the rates in the VPA + TMZ or ACNU groups were increased compared with TMZ or ACNU alone groups (P<0.05). The expression of MGMT remained negative in the G1 population following treatment with VPA, but MGMT expression became negative in the 2 MGMT-positive cell populations (G2 and G3) following VPA treatment. The MGMT promoter in the G1 population was partially methylated in the control group, but was fully methylated following VPA treatment, while the promoters of G2, G3 were unmethylated in the control group and became partially methylated in the VPA treatment group. Taken together, TMZ and ACNU may suppress the growth of glioma stem cells in vitro in a dose-dependent manner. VPA may enhance the inhibitory effects of various concentrations of TMZ and ACNU on the growth of MGMT-negative/positive cells, particularly on MGMT-positive cell populations. VPA itself may induce the apoptosis of glioma cells, and VPA combined with TMZ or ACNU may enhance TMZ/ACNU-induced apoptosis of glioma stem cells. Furthermore, VPA may also promote the methylation of the MGMT promoter to silence MGMT expression in glioma cells, which may be an important mechanism through which VPA enhances the efficacy of TMZ and ACNU in targeting glioma stem cells.