High-grade gliomas: reality and hopes

circRNA-SMO upregulates CEP85 to promote proliferation and migration of glioblastoma via sponging miR-326

Circular RNAs (circRNAs) play an important role in cancer development by sponging microRNAs (miRNAs) to regulate the signaling axis. However, more comprehensive mechanisms of circRNAs in glioblastoma need to be elucidated. RT-qPCR was used to detect the expression levels of circRNA-SMO and miR-326. Dual-luciferase reporter assays were conducted to verify the interaction among circRNA-SMO, miR-326, and CEP85. Flow cytometric analysis was performed to detect apoptosis. Western blotting was used to determine the protein levels of the different molecules. Animal xenograft experiments were performed to evaluate the role of circRNA-SMO in vivo. CircRNA-SMO was upregulated in glioblastoma tissues and glioblastoma cells. CircRNA-SMO downregulation inhibited the viability and colony-forming ability of the glioblastoma cells. In addition, miR-326 was downregulated in glioblastoma cells, which was verified to sponge circRNA-SMO and interact with CEP85. Moreover, circRNA-SMO inhibition induced the elevation of miR-326 and apoptosis, accompanied by a decrease in CEP85. CircRNA-SMO knockdown-mediated tumor inhibition was prevented by an miR-326 inhibitor. Furthermore, circRNA-SMO inhibition inhibited tumor growth in vivo, accompanied by an increase in miR-326 and a decline in CEP85 in tumor tissues. Conclusions. CircRNA-SMO sponges miR-326 to promote glioblastoma proliferation and migration by upregulating CEP85 expression. This study clarified the role of circRNA-SMO in the development of glioblastoma, providing novel insights for its treatment.

Preoperative Systemic Immune-Inflammation Index is a Potential Biomarker in Adult Patients with High-Grade Gliomas Undergoing Radical Resection

Background

Increasing evidence has highlighted that systemic immune-inflammation index (SII), a recently developed prognostic biomarker that utilizes peripheral platelet, lymphocyte and neutrophil counts, is associated with unfavorable prognosis in various tumors. Nevertheless, the prognostic significance of SII in high-grade gliomas patients undergoing radical resection remains unclear. Therefore, the present study aimed to assess the potential of SII as a prognostic biomarker in this patient population.

Methods

A total of 111 adult patients with high-grade gliomas who underwent radical resection were consecutively enrolled in this investigation. The study involved the categorization of patients into high and low SII groups using predetermined cut-off values. Subsequently, forward stepwise logistic regression was employed to identify autonomous predictors for early gliomas recurrence. To mitigate the impact of confounding factors, a propensity score matching (PSM) analysis was performed between high and low SII patients. Finally, the Kaplan-Meier approach was utilized to compare the progression-free survival (PFS) and overall survival (OS) of the two groups.

Results

The study involved the categorization of patients into two groups based on their SII levels, namely high SII (> 604.8) and low SII (≤ 604.8) groups. Forward stepwise logistic regression revealed that high SII (p < 0.001) and tumor size ≥ 50 mm (p < 0.001) were significantly related to early recurrence of gliomas. Furthermore, the results indicate that PFS and OS were significantly shorter in the high SII group compared to the low SII group, both before and after PSM (p < 0.05).

Conclusion

Preoperative biomarker SII can serve as a prognostic biomarker for early recurrence and prognosis in patients with high-grade gliomas undergoing radical resection. Furthermore, the combination of tumor size and SII demonstrates a robust predictive capacity for early recurrence and prognosis in this patient population.

A lightweight 3D UNet model for glioma grading

Objective. Glioma is one of the most fatal cancers in the world which has been divided into low grade glioma (LGG) and high grade glioma (HGG), and its image grading has become a hot topic of contemporary research. Magnetic resonance imaging (MRI) is a vital diagnostic tool for brain tumor detection, analysis, and surgical planning. Accurate and automatic glioma grading is crucial for speeding up diagnosis and treatment planning. Aiming at the problems of (1) large number of parameters, (2) complex calculation, and (3) poor speed of the current glioma grading algorithms based on deep learning, this paper proposes a lightweight 3D UNet deep learning framework, which can improve classification accuracy in comparison with the existing methods. Approach. To improve efficiency while maintaining accuracy, existing 3D UNet has been excluded, and depthwise separable convolution has been applied to 3D convolution to reduce the number of network parameters. The weight of parameters on the basis of space and channel compression & excitation module has been strengthened to improve the model in the feature map, reduce the weight of redundant parameters, and strengthen the performance of the model. Main results. A total of 560 patients with glioma were retrospectively reviewed. All patients underwent MRI before surgery. The experiments were carried out on T1w, T2w, fluid attenuated inversion recovery, and CET1w images. Additionally, a way of marking tumor area by cube bounding box is presented which has no significant difference in model performance with the manually drawn ground truth. Evaluated on test datasets using the proposed model has shown good results (with accuracy of 89.29%). Significance. This work serves to achieve LGG/HGG grading by simple, effective, and non-invasive diagnostic approaches to provide diagnostic suggestions for clinical usage, thereby facilitating hasten treatment decisions.

Corpus Callosum Remodeling in Glioma: Constancy of Fiber Density and Anisotropy in MRI

Corpus callosum (CC) is the primary fiber system bridging the cerebral hemispheres and is of critical importance for glioma migration which downgrades the prognosis. Here we present the specific pattern of CC restructuring in glioma patients. We probe that the magnetic resonance imaging-based fiber count decrease can be a ready noninvasive indicator of glioma aggressivity and prognosis. We find that to maintain the callosal neural transmission efficiency, the optimum architectural density of white matter fibers remains unchanged, even though there is gross fiber loss. This adaptation occurs by CC's isotonic restructuration, a protective compensatory behavior for maintaining CC's optimal functional efficiency despite malignant infiltration.

Role of autophagy in regulation of glioma stem cells population during therapeutic stress

Glioblastoma is highly recurrent and aggressive tumor with poor prognosis where existence of glioma stem cell (GSCs) population is well established. The GSCs display stem cell properties such as self-renewable, proliferation and therapeutic resistance which contribute to its role in tumor progression, metastasis and recurrence. Cancer stem cells (CSCs) can also be induced from non-stem cancer cells in response to radio/chemotherapy that further contribute to cancer relapse post therapy. Role of autophagy has been implicated in the existence of CSCs in different cancers; however, its role in GSCs is still unclear. Moreover, since autophagy is induced in response to various chemotherapeutic agents, it becomes imperative to understand the role of autophagy in therapy-induced pool of CSCs. Here, we investigated the role of autophagy in the maintenance of GSCs and temozolomide (TMZ)-induced therapeutic response. Glioblastoma cell lines (U87MG, LN229) were cultured as monolayer as well as GSC enriched tumorspheres and sub-spheroid population. Our results demonstrated that the tumorspheres maintained higher level of autophagy than the monolayer cells and inhibition of autophagy significantly reduced the percentage of GSCs and their self-renewal capacity. Further, TMZ at clinically relevant concentration resulted in an induction of survival autophagy in glioblastoma cells. We also observed that TMZ treatment significantly increased the expression of GSC markers, suggesting an increased pool of GSCs. Importantly, inhibition of autophagy prevented this TMZ-induced increased GSC population, suggesting a critical role for autophagy in therapy-induced generation of GSC pool. Overall, our findings revealed; i) higher levels of autophagy in GSCs; ii) TMZ induces protective autophagy and up-regulates pool of GSCs; and iii) inhibition of autophagy prevents TMZ-induced GSCs pool suggesting its role regulating GSC population in response to chemotherapy. Our study signifies a positive contribution of autophagy in survival of GSCs which implicates the use of autophagy inhibitors in a combinational approach to target TMZ-induced GSCs for developing effective therapeutic strategies. Further efforts are required to study the role of autophagy in therapy- induced GSC pool in other cancer types for its broad therapeutic implication.

Circular RNA SMO sponges miR-338-3p to promote the growth of glioma by enhancing the expression of SMO

Glioma is one of the most common tumors in the brain and complete cure still a challenge. The present research aimed to investigate the molecular mechanism of circular RNA SMO (circSMO742) in glioma, via targeting miR-338-3p and regulating SMO expression. QRT-PCR was utilized to examine the expression profiles of circSMO742 and microRNA-338-3p (miR-338-3p) in glioma. SMO protein in glioma was tested via western blot. RNA pulldown assay and dual luciferase reporter assays were used to explore the targeting correlation between RNAs. MTT assay, transwell assays and flow cytometry were used to investigate cell proliferation, migration and invasion, and apoptosis, respectively. Tumor xenograft was done to ascertain the effect of circSMO742 knocking down on tumor growth. CircSMO742 and SMO were highly expressed in glioma tissues, while miR-338-3p expression was reduced. CircSMO742 together with SMO could promote cells proliferation, migration and invasion while inhibit cells apoptosis, whereas miR-338-3p showed negative impacts on the cell activity. Knocking down of circSMO742 suppressed glioma growing in vivo. CircSMO742 promoted glioma growth by sponging miR-338-3p to regulate SMO expression. Our research revealed a new molecular mechanism of glioma growth and provide a fresh perspective on circRNAs in glioma progression.

Downregulation of miR‑186 promotes the proliferation and drug resistance of glioblastoma cells by targeting Twist1

Temozolomide (TMZ) is widely used as a chemotherapeutic agent in the treatment of glioma; however, the development of drug resistance remains a major obstacle in the effective treatment of glioblastoma. Increasing evidence has indicated that microRNAs (miRs) are involved in the drug resistance of glioma; however, the role of miR‑186‑5p in the TMZ resistance of glioblastoma remains unknown. In the present study, the role of miR‑186‑5p in the resistance of glioblastoma to TMZ was investigated. mRNA and protein expression levels were detected via reverse transcription‑quantitative PCR and western blot analysis, respectively. It was determined that miR‑186‑5p was significantly downregulated in glioblastoma tissues and cell lines. Additionally, the expression of miR‑186‑5p was decreased, whereas that of Twist1 was upregulated during the development of drug resistance in glioma cells. The introduction of miR‑186 into glioblastoma cells via transfection decreased the proliferation and TMZ resistance of glioblastoma cells, as determined via 5‑ethynyl‑2'‑deoxyuridine and Cell Counting Kit‑8 assays, whereas the inhibition of miR‑186‑5p induced opposing effects. Furthermore, luciferase reporter and expression rescue assays revealed that miR‑186‑5p bound to the 3'‑untranslated region of Twist‑related protein 1 (Twist1). In conclusion, the present study demonstrated that downregulation of miR‑186‑5p may contribute to the proliferation and drug resistance of glioblastoma cells via the regulation of Twist1 expression. These results suggested that miR‑186‑5p may be a novel therapeutic target in the treatment of glioblastoma.

SAHA and/or MG132 reverse the aggressive phenotypes of glioma cells: An in vitro and vivo study

To elucidate the anti-tumor effects and molecular mechanisms of SAHA (a histone deacetylase inhibitor) and MG132 (a proteasome inhibitor) on the aggressive phenotypes of glioma cells, we treated U87 and U251 cells with SAHA or/and MG132, and detected phenotypes’ assays with phenotype-related molecules examined. It was found that SAHA or/and MG132 treatment suppressed proliferation in both concentration- and time-dependent manners, inhibited energy metabolism, migration, invasion and lamellipodia formation, and induced G₂ arrest and apoptosis in the glioma cells. The treatment with SAHA increased the expression of acetyl-histones 3 and 4, which were recruited to the promoters of p21, p27, Cyclin D1, c-myc and Nanog to down-regulate their transcriptional levels. Expression of acetyl-histones 3 and 4 was higher in gliomas than normal brain tissues. Both drugs’ exposure suppressed tumor growth in nude mice by inducing apoptosis and inhibiting proliferation, but increased serum aminotransferase and creatinine. These results indicated that SAHA and/or MG132 may suppress the aggressive phenotypes of glioma cells. They might be employed to treat the glioma if both hepatic and renal injuries are prevented.

KDM2B overexpression correlates with poor prognosis and regulates glioma cell growth

Background

Gliomas are one of the most lethal cancers in the human central nervous system. Despite clinical treatment advancements, the prognosis of patients with glioma remains poor. KDM2B is a histone lysine demethylase, which has been observed in multiple tumors. But the concrete role of KDM2B in gliomas remains to be further illustrated.

Methods

The KDM2B expression in gliomas was detected with immunohistochemistry and Western blot assay. Furthermore, knockdown of KDM2B in U87 and U251 glioma cell lines, the proliferation capacity was evaluated by cell viability assay, colon formation assay and flow cytometry in vitro. Western blot assay was used to analyze the p21, EZH2 and cyclinD1 changes followed by knockdown of KDM2B.

Results

KDM2B was upregulated in tissues of glioma patients, and the expression was correlated to cancer progression. Downregulation of KDM2B in U87 and U251 glioma cell lines inhibited cell proliferation and arrested cell cycle in G0/G1 phase. In addition, silencing KDM2B promoted the upregulation of p21 while reduced the expression of EZH2 and cyclinD1.

Conclusion

Taken together, our results revealed that KDM2B might influence gliomas growth and act as a novel therapeutic target for glioma patients.

Methylation of the miR-126 gene associated with glioma progression

Gliomas are the most common and the most malignant brain tumors, accouting for 45-55% of all intracranial tumors. The incidence of glioma worldwide is about 6-12 per 100,000. Recently, several studies showed that the activation of the oncogenes and the inactivation and/or loss of the tumor suppressor genes, especially for miRNA-21, let-7 and so on, are the most primary molecule event in gliomas. MicroRNAs (miRNAs) are a class of endogenously expressed small noncoding RNAs which are usually 21-23 nucleotides long. miRNAs regulate gene expression and play important roles in a variety of physiological and pathological processes, such as cell proliferation, differentiation and apoptosis. To date, Growing evidence has shown that mi RNAs are frequently dysregulated in human cancers and can act as both tumor suppressors and oncogenes. Along with the discovery of micro RNA, more and more research focusing on its relationship with glioma was carried out to investigate the biological features of glioma and to provide experimental evidence for glioma mechanism. In the present study, we aimed to verify the miRNA-126 down-regulation which showed in the results of glioma tissue miRNAs chip and discuss the miRNA-126 methylation in patients with glioma. A total of 50 samples from patients with glioma and 20 control samples from patients with cerebral trauma were included in this study. The expression levels of the miR-126 gene were detected using quantitative polymerase chain reaction (PCR), and the methylation status of miR-126 was examined using methylation-specific PCR-denaturing high-performance liquid chromatography (MSP-DHPLC). The expression level of miRNA-126 was found to be significantly higher in the control group (0.6134 ± 0.1214) than in the glioma group (0.2771 ± 0.1529; P < 0.05). The expression was also significantly elevated in low-grade gliomas (0.3117 ± 0.1474) compared with high-grade gliomas (0.1582 ± 0.1345; P < 0.05). In addition, increased methylation of miR-126 was found in 40% of glioma patients in our study (20/50 cases), resulting in significantly decreased miR-126 expression (0.1715 ± 0.1376; P < 0.05). Our results indicate that we verified successfully the miRNA-126 down-regulation phenomenon in patients with glioma which showed in the results of glioma tissue miRNAs chip and the miRNA-126 down-regulation through methylation in patients with glioma. So we could say that epigenetic modification is a crucial mechanism for controlling the expression of miR-126 in glioma.

Anti-tumoral activity of native compound morelloflavone in glioma

The aim of the study was to investigate the anti-tumoral activity of morelloflavone substances with different structures. We also studied the possible link between morelloflavone structure and its function. Various types of chromatographic techniques were used to isolate and screen morelloflavone substances from the extracts of gambogic tree trunk and the morelloflavone structures were identified by analytical techniques such as high resolution mass spectrometry and nuclear magnetism. Anti-tumoral activities of different compounds were investigated and the link between the antitumor activity and the structure of compound was exaimed. Our results showed that the isolated morelloflavone substances demonstrated a certain level of antitumor activity. The compound no. 1 had the strongest effect to inhibit glioma U87 and C6 cells followed by compound no. 2 while compound no. 5 was the weakest among them. We conducted a preliminary analysis on the structure-function relationship through the structure comparison and we concluded that the antitumor effects of morelloflavone substances with different structures were significantly different from each other. Thus, the glucose chain in C4 position of biflavone structure can enhance the antitumor activity of the compound in glioma cells. Additionally, the formation of intramolecular hydrogen bonds in biflavone compounds may also play a role in enhancing the antitumor activity and inhibition rate.

MiR-422a acts as a tumor suppressor in glioblastoma by targeting PIK3CA

Although surgical treatment, chemotherapy, and radiotherapy have improved the overall survival rate in glioblastoma multiforme (GBM), further intensive research of GBM's molecular mechanism is still needed. In this study, we observed that miR-422a was downregulated in GBM tissues and cell lines by quantitative real-time polymerase chain reaction (PCR) and primer extension assay. Overexpression of miR-422a significantly reduced the cell proliferation, migration, and invasion of GBM cells. Functional study indicated that miR-422a inhibited cell proliferation, invasion, and migration by targeting PIK3CA, an important member of PI3K/Akt signal pathway. These results demonstrate that the miR-422a/PIK3CA axis may constitute a potential target for GBM therapy.

Recurrence patterns in patients with high-grade glioma following temozolomide-based chemoradiotherapy

There is currently no consensus regarding the optimal radiation volume for high-grade glioma (HGG). The brain volume irradiated is associated with the extent of radiation neurotoxicity. When reducing the treatment volume, the risk of geographic tumor miss should be considered. In such cases, the recurrence patterns and, particularly, the rate of marginal tumor recurrence, are important indices for determining the optimal radiation volume. In the present study, a smaller-target delineation protocol with limited margins was adopted. The postoperative enhancing tumor and resection cavity were defined as gross tumor volume (GTV); 1 and 2 cm were added to the GTV to create clinical target volume (CTV1 and CTV2), which received 60 and 54 Gy, respectively. At a median follow-up of 14 months, 54 HGG patients developed tumor recurrence. The median overall and progression-free survival were 14 and 10.5 months, respectively. A total of 34 patients developed central recurrence, 8 presented with in-field recurrence, 2 developed marginal recurrence, 2 had distant recurrence and 11 patients developed cerebrospinal fluid dissemination, 2 of whom developed central recurrence, with 1 patient simultaneously developing marginal recurrence. Local recurrence (central and in-field) was found to be the main recurrence pattern. As the rate of marginal recurrence was low (<5%), it appears that the smaller irradiated volume in the present study was appropriate. However, clinical trials investigating limited irradiation volume are required to validate our findings.

Myosin VI contributes to malignant proliferation of human glioma cells

Previously characterized as a backward motor, myosin VI (MYO6), which belongs to myosin family, moves toward the minus end of the actin track, a direction opposite to all other known myosin members. Recent researches have illuminated the role of MYO6 in human cancers, particularly in prostate cancer. However, the role of MYO6 in glioma has not yet been determined. In this study, to explore the role of MYO6 in human glioma, lentivirus-delivered short hairpin RNA (shRNA) targeting MYO6 was designed to stably down-regulate its endogenous expression in glioblastoma cells U251. Knockdown of MYO6 signifi cantly inhibited viability and proliferation of U251 cells in vitro. Moreover, the cell cycle of U251 cells was arrested at G0/G1 phase with the absence of MYO6, which could contribute to the suppression of cell proliferation. In conclusion, we firstly identified the crucial involvement of MYO6 in human glioma. The inhibition of MYO6 by shRNA might be a potential therapeutic method in human glioma.

Two mature products of MIR-491 coordinate to suppress key cancer hallmarks in glioblastoma

MIR-491 is commonly co-deleted with its adjacent CDKN2A on chromosome 9p21.3 in glioblastoma multiforme (GBM). However, it is not known whether deletion of MIR-491 is only a passenger event or has an important role. Small-RNA sequencing of samples from GBM patients demonstrated that both mature products of MIR-491 (miR-491-5p and -3p) are downregulated in tumors compared with the normal brain. The integration of GBM data from The Cancer Genome Atlas (TCGA), miRNA target prediction and reporter assays showed that miR-491-5p directly targets EGFR, CDK6 and Bcl-xL, whereas miR-491-3p targets IGFBP2 and CDK6. Functionally, miR-491-3p inhibited glioma cell invasion; overexpression of both miR-491-5p and -3p inhibited proliferation of glioma cell lines and impaired the propagation of glioma stem cells (GSCs), thereby prolonging survival of xenograft mice. Moreover, knockdown of miR-491-5p in primary Ink4a-Arf-null mouse glial progenitor cells exacerbated cell proliferation and invasion. Therefore, MIR-491 is a tumor suppressor gene that, by utilizing both mature forms, coordinately controls the key cancer hallmarks: proliferation, invasion and stem cell propagation.

Genomically amplified Akt3 activates DNA repair pathway and promotes glioma progression

Akt is a robust oncogene that plays key roles in the development and progression of many cancers, including glioma. We evaluated the differential propensities of the Akt isoforms toward progression in the well-characterized RCAS/Ntv-a mouse model of PDGFB-driven low grade glioma. A constitutively active myristoylated form of Akt1 did not induce high-grade glioma (HGG). In stark contrast, Akt2 and Akt3 showed strong progression potential with 78% and 97% of tumors diagnosed as HGG, respectively. We further revealed that significant variations in polarity and hydropathy values among the Akt isoforms in both the pleckstrin homology domain (P domain) and regulatory domain (R domain) were critical in mediating glioma progression. Gene expression profiles from representative Akt-derived tumors indicated dominant and distinct roles for Akt3, consisting primarily of DNA repair pathways. TCGA data from human GBM closely reflected the DNA repair function, as Akt3 was significantly correlated with a 76-gene signature DNA repair panel. Consistently, compared with Akt1 and Akt2 overexpression models, Akt3-expressing human GBM cells had enhanced activation of DNA repair proteins, leading to increased DNA repair and subsequent resistance to radiation and temozolomide. Given the wide range of Akt3-amplified cancers, Akt3 may represent a key resistance factor.

Insulin-like growth factor (IGF) signaling in tumorigenesis and the development of cancer drug resistance

One of the greatest obstacles to current cancer treatment efforts is the development of drug resistance by tumors. Despite recent advances in diagnostic practices and surgical interventions, many neoplasms demonstrate poor response to adjuvant or neoadjuvant radiation and chemotherapy. As a result, the prognosis for many patients afflicted with these aggressive cancers remains bleak. The insulin-like growth factor (IGF) signaling axis has been shown to play critical role in the development and progression of various tumors. Many basic science and translational studies have shown that IGF pathway modulators can have promising effects when used to treat various malignancies. There also exists a substantial body of recent evidence implicating IGF signaling dysregulation in the dwindling response of tumors to current standard-of-care therapy. By better understanding both the IGF-dependent and -independent mechanisms by which pathway members can influence drug sensitivity, we can eventually aim to use modulators of IGF signaling to augment the effects of current therapy. This review summarizes and synthesizes numerous recent investigations looking at the role of the IGF pathway in drug resistance. We offer a brief overview of IGF signaling and its general role in neoplasia, and then delve into detail about the many types of human cancer that have been shown to have IGF pathway involvement in resistance and/or sensitization to therapy. Ultimately, our hope is that such a compilation of evidence will compel investigators to carry out much needed studies looking at combination treatment with IGF signaling modulators to overcome current therapy resistance.

Fractionated stereotactic radiotherapy plus bevacizumab after response to bevacizumab plus irinotecan as a rescue treatment for high-grade gliomas

AIM

To evaluate the possibility of implementing a new scheme of rescue treatment after relapse or progression of high-grade glioma (HGG) treated at the first-line with bevacizumab and irinotecan (BVZ+CPT11), evaluating the response and toxicity of associating BVZ and fractionated stereotactic radiotherapy (BVZ+FSRT).

MATERIALS AND METHODS

We retrospectively analysed data from 59 patients with relapse of HGG. Nine patients with HGG relapse after treatment using the Stupp protocol that were treated with BVZ+CPT11 for progression between July 2007 and August 2012, after which the response was assessed according to the Revised Assessment in Neuro-Oncology (RANO) criteria. BVZ was administered at a dose of 10 mg/kg and FSRT up to a prescribed dose of 30 Gy, 500 cGy per fraction, three days a week. The median follow-up was 38 months.

RESULTS

The treatment was well-tolerated by all patients. The response after nuclear magnetic resonance imaging (MRI) at 3-6 months was progression in two patients, stable disease in four, and three patients had a partial response. The median overall survival (OS) from diagnosis until death or the last control was 36.8 months. The median progression-free survival (PFS) was 10.8 months. The results from tumour sub-group analysis indicated that the PFS was not statistically significant although it seemed that it was higher in grade-III. The OS was higher in grade-III gliomas.

CONCLUSIONS

The combination of BVZ+FSRT as a second-line HGG relapse rescue treatment is well-tolerated and seems to offer promising results. We believe that multi-centre prospective studies are needed to determine the long-term efficacy and toxicity of this therapeutic approach.

Combination of unsaturated fatty acids and ionizing radiation on human glioma cells: cellular, biochemical and gene expression analysis

Background

Based on previous observations a potential resort in the therapy of the particularly radioresistant glioma would be its treatment with unsaturated fatty acids (UFAs) combined with irradiation.

Methods

We evaluated the effect of different UFAs (arachidonic acid (AA), docosahexaenoic acid (DHA), gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and oleic acid (OA)) on human U87 MG glioma cell line by classical biochemical end-point assays, impedance-based, real-time cellular and holographic microscopic analysis. We further analyzed AA, DHA, and GLA at morphological, gene and miRNA expression level.

Results

Corresponding to LDH-, MTS assays and real-time cytoxicity profiles AA, DHA, and GLA enhanced the radio sensitivity of glioma cells. The collective application of polyunsaturated fatty acids (PUFAs) and irradiation significantly changed the expression of EGR1, TNF-α, NOTCH1, c-MYC, TP53, HMOX1, AKR1C1, NQO1, while up-regulation of GADD45A, EGR1, GRP78, DDIT3, c-MYC, FOSL1 were recorded both in response to PUFA treatment or irradiation alone. Among the analyzed miRNAs miR-146 and miR-181a were induced by DHA treatment. Overexpression of miR-146 was also detected by combined treatment of GLA and irradiation.

Conclusions

Because PUFAs increased the radio responsiveness of glioma cells as assessed by biochemical and cellular assays, they might increase the therapeutic efficacy of radiation in treatment of gliomas. We demonstrated that treatment with DHA, AA and GLA as adjunct to irradiation up-regulated the expression of oxidative-stress and endoplasmic reticulum stress related genes, and affected NOTCH1 expression, which could explain their additive effects.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-142) contains supplementary material, which is available to authorized users.

MiR-181b sensitizes glioma cells to teniposide by targeting MDM2

BACKGROUND

Although the incidence of glioma is relatively low, it is the most malignant tumor of the central nervous system. The prognosis of high-grade glioma patient is very poor due to the difficulties in complete resection and resistance to radio-/chemotherapy. Therefore, it is worth investigating the molecular mechanisms involved in glioma drug resistance. MicroRNAs have been found to play important roles in tumor progression and drug resistance. Our previous work showed that miR-181b is involved in the regulation of temozolomide resistance. In the current study, we investigated whether miR-181b also plays a role in antagonizing the effect of teniposide.

METHODS

MiR-181b expression was measured in 90 glioma patient tissues and its relationship to prognosis of these patients was analyzed. Cell sensitivity to teniposide was tested in 48 primary cultured glioma samples. Then miR-181b stably overexpressed U87 cells were generated. The candidate genes of miR-181b from our previous study were reanalyzed, and the interaction between miR-181b and target gene MDM2 was confirmed by dual luciferase assay. Cell sensitivity to teniposide was detected on miR-181b over expressed and MDM2 down regulated cells.

RESULTS

Our data confirmed the low expression levels of miR-181b in high-grade glioma tissues, which is related to teniposide resistance in primary cultured glioma cells. Overexpression of miR-181b increased glioma cell sensitivity to teniposide. Through target gene prediction, we found that MDM2 is a candidate target of miR-181b. MDM2 knockdown mimicked the sensitization effect of miR-181b. Further study revealed that miR-181b binds to the 3'-UTR region of MDM2 leading to the decrease in MDM2 levels and subsequent increase in teniposide sensitivity. Partial restoration of MDM2 attenuated the sensitivity enhancement by miR-181b.

CONCLUSIONS

MiR-181b is an important positive regulator on glioma cell sensitivity to teniposide. It confers glioma cell sensitivity to teniposide through binding to the 3'-UTR region of MDM2 leading to its reduced expression. Our findings not only reveal the novel mechanism involved in teniposide resistance, but also shed light on the optimization of glioma treatment in the future.