Potential Strategies Overcoming the Temozolomide Resistance for Glioblastoma

Dihydroartemisinin initiates ferroptosis in glioblastoma through GPX4 inhibition

It has been demonstrated from previous studies about the killing effect of dihydroartemisinin (DHA) on glioblastoma, which involves multiple aspects: cytotoxicity, cell cycle arrest and invasion inhibition. DHA has the advantages of low cytotoxicity to normal cells, selective killing effect and low drug resistance, making it one of the popular anti-tumor research directions. Ferroptosis is a newly discovered form of cell death characterized by iron dependence and lipid reactive oxygen species (ROS) accumulation. In the present study, we found differences in the expression of transferrin receptors in normal human astrocytes (NHA) and glioblastoma cells (U87 and A172), which may be one of the mechanisms of DHA selective killing effect. Through the determination of ferroptosis-related protein expression, we found that the significant decrease of GPX4, accompanied by the constant expression of xCT and ACSL4, suggesting GPX4 was a pivotal target for DHA-activated ferroptosis in glioblastoma. Total and lipid ROS levels were increased and all these results could be reversed by the ferroptosis inhibitor, ferrostatin-1. These findings demonstrated ferroptosis would be a critical component of cell death caused by DHA and GPX4 was the main target. All these results provide a novel treatment direction to glioblastoma. The association between ferroptosis and polyamines is also discussed, which will provide new research directions for ferroptosis caused by DHA in glioblastoma.

A Potential Mechanism of Temozolomide Resistance in Glioma-Ferroptosis

Temozolomide (TMZ) is the first-line chemotherapy drug that has been used to treat glioma for over a decade, but the benefits are limited by half of the treated patients who acquired resistance. Studies have shown that glioma TMZ resistance is a complex process with multiple factors, which has not been fully elucidated. Ferroptosis, which is a new type of cell death discovered in recent years, has been reported to play an important role in tumor drug resistance. The present study reviews the relationship between ferroptosis and glioma TMZ resistance, and highlights the role of ferroptosis in glioma TMZ resistance. Finally, the investigators discussed the future orientation for ferroptosis in glioma TMZ resistance, in order to promote the clinical use of ferroptosis induction in glioma treatment.

Temozolomide therapy for aggressive pituitary tumours - current understanding and future perspectives

The use of temozolomide (TMZ) for the management of aggressive pituitary tumours (APT) has revolutionised clinical practice in this field with significantly improved clinical outcomes and long-term survival. Its use is now well established however a large number of patients do not respond to treatment and recurrence after cessation of TMZ is common. A number of challenges remain for clinicians such as appropriate patient selection, treatment duration and the role of combination therapy. This review will examine the use of TMZ to treat APT including mechanism of action, treatment regimen and duration; biomarkers predicting response to treatment and patient selection; and current evidence for administration of TMZ in combination with other agents.

Coumarins modulate the anti-glioma properties of temozolomide

In the recent years, coumarin bioactive compounds have been identified to posess anticancer properties. Therefore, the aim of the present study was to investigate for the first time the efficacy of osthole, umbelliferone, esculin, and 4-hydroxycoumarin, alone and in combination with Temozolomide, in the elimination of deadly brain tumors, anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM) cells via programmed death. Our results indicated that osthole, umbelliferone, esculin, and 4-hydroxycoumarin initiated mainly apoptosis in the T98G and MOGGCCM cells. Osthole was the most effective. It also initiated autophagy in a small percentage of the cell population. The co-incubation with Temozolomide did not increase the pro-apoptotic potential of natural compounds but decreased the level of autophagy in the T98G cells. Apoptosis was associated with reduced mitochondrial membrane potential, activation of caspase 3, inhibition of Bcl-2 expression and the presence of a Bcl-2/Beclin 1. Blocking of Bcl-2 expression resulted in promotion of apoptosis, but not autophagy, in the MOGGCCM and T98G lines. It also sensitized astrocytoma cells, but not GBM, to the combined osthole and TMZ treatment, which was correlated with a reduced level of Beclin 1 and increased expression of caspase 3. Osthole and TMZ, alone and in combination, inhibited the migratory phenotype of the GBM and AA cells. In summary, our results indicated that osthole effectively eliminated glioma cells via apoptosis, what was correlated with Bcl-2/Beclin 1 complex formation. Considering the anti-migratory effect, osthole and Temozolomide display antiglioma potential but it needs further extensive studies.

Graphene-Induced Transdifferentiation of Cancer Stem Cells as a Therapeutic Strategy against Glioblastoma

Glioblastoma (GBM) is an extremely malignant tumor of the central nervous system, characterized by low response to treatments and reoccurrence. This therapeutic resistance is believed to arise mostly from the presence of a subpopulation of tumorigenic stem cells, known as cancer stem cells (CSCs). In addition, the surrounding microenvironment is known to maintain CSCs, thus supporting tumor development and aggressiveness. This review focuses on a therapeutic strategy involving the stem cell trans-differentiating ability of graphene and its derivatives. Graphene distinguishes itself from other carbon-based nanomaterials due to an array of properties that makes it suitable for many purposes, from bioengineering to biomedical applications. Studies have shown that graphene is able to promote and direct the differentiation of CSCs. In addition, potential usage of graphene in GBM treatment represents a challenge in respect to its administration method. The present review also provides a general outlook of the potential side effects (e.g., cell toxicity) that graphene could have. Overall, this report discusses certain graphene-based therapeutic strategies targeting CSCs, which can be considered as prospective effective GBM treatments.

CDK4/6 inhibition suppresses tumour growth and enhances the effect of temozolomide in glioma cells

In adults, glioma is the most commonly occurring and invasive brain tumour. For malignant gliomas, the current advanced chemotherapy includes TMZ (temozolomide). However, a sizeable number of gliomas are unyielding to TMZ, hence, giving rise to an urgent need for more efficient treatment choices. Here, we report that cyclin-dependent kinases 4 (CDK4) is expressed at significantly high levels in glioma cell lines and tissues. CDK4 overexpression enhances colony formation and proliferation of glioma cells and extends resistance to inhibition of TMZ-mediated cell proliferation and induction of apoptosis. However, CDK4 knockdown impedes colony formation and cell proliferation, and enhances sensitivity of glioma cells to TMZ. The selective inhibition of CDK4/6 impedes glioma cell proliferation and induces apoptotic induction. The selective inhibitors of CDK4/6 may enhance glioma cell sensitivity to TMZ. We further showed the possible role of RB phosphorylation mediated by CDK4 for its oncogenic function in glioma. The growth of glioma xenografts was inhibited in vivo, through combination treatment, and corresponded to enhanced p-RB levels, reduced staining of Ki-67 and enhanced activation of caspase 3. Therefore, CDK4 inhibition may be a favourable strategy for glioma treatment and overcomes TMZ resistance.

Micro-RNA29b enhances the sensitivity of glioblastoma multiforme cells to temozolomide by promoting autophagy

To explore whether or not aberrant expression of miR-29b in glioblastoma multiforme (GBM) cells was associated with temozolomide (TMZ) resistance and to elucidate potential underlying mechanisms. Upregulation of miR-29 in GBM cells was achieved by transfecting miR-29b mimics. Changes in cell viability were measured by using CCK-8 assays. Flow cytometry and TUNEL assays were used to quantify the number of apoptotic cells. The expression levels of apoptosis-related proteins as well as autophagy-associated proteins, and the expression levels of both apoptotic and autophagic genes were determined by Western blotting. Autophagy flux was monitored by transfecting mRFP-GFP-LC3 adenovirus. We halted autophagy by introducing Atg 5-specific siRNA or the autophagy inhibitor Bafilomycin A1 (Baf-A1). We also employed a GBM xenograft mice model to confirm the role of miR-29b in vivo. miR-29b overexpression induced inhibition of cell viability, and also induced apoptosis and autophagy in U251 and U87MG cells. Furthermore, upregulation of miR-29b was able to potentiate the level of antitumor activity of TMZ against tested cells. We also found that autophagy induced by miR-29b, at least partially, contributed to the increase of TMZ sensitivity in GBM cells. As was evidenced by blockade of autophagy, the application of Atg 5 siRNA or Baf-A1 was able to significantly reverse these effects. Consistent with observations in vitro, findings of in vivo assessment also confirmed that overexpression of miR-29b was able to effectively halt tumor growth and enhance the antitumor activity of TMZ. miR-29b potentiates TMZ sensitivity against GBM cells by inducing autophagy and the combined use of miR-29 mimic and TMZ might represent a potential therapeutic strategy for GBM patients.

DNA Methylation and Hydroxymethylation in Cervical Cancer: Diagnosis, Prognosis and Treatment

Recent discoveries have led to the development of novel ideas and techniques that have helped elucidate the correlation between epigenetics and tumor biology. Nowadays, the field of tumor genetics has evolved to include a new type of regulation by epigenetics. An increasing number of studies have demonstrated the importance of DNA methylation and hydroxymethylation in specific genes in the progression of cervical cancer. Determining the methylation and hydroxymethylation profiles of these genes will help in the early prevention and diagnosis, monitoring recurrence, prognosis, and treatment of patients with cervical cancer. In this review, we focus on the significance of aberrant DNA methylation and hydroxymethylation in cervical cancer and the use of these epigenetic signatures in clinical settings.

miR-152-5p suppresses glioma progression and tumorigenesis and potentiates temozolomide sensitivity by targeting FBXL7

A generally used chemotherapeutic drug for glioma, a frequently diagnosed brain tumour, is temozolomide (TMZ). Our study investigated the activity of FBXL7 and miR-152-5p in glioma. Levels of microRNA-152-5p (miR-152-5p) and the transcript and protein of FBXL7 were assessed by real-time PCR and Western blotting, respectively. The migratory and invasive properties of cells were measured by Transwell migration and invasion assay and their viability were examined using CCK-8 assay. Further, the putative interaction between FBXL7 and miR-152-5p were analysed bioinformatically and by luciferase assay. The activities of FBXL7, TMZ and miR-152-5p were analysed in vivo singly or in combination, on mouse xenografts, in glioma tumorigenesis. The expression of FBXL7 in glioma tissue is significantly up-regulated, which is related to the poor prognosis and the grade of glioma. TMZ-induced cytotoxicity, proliferation, migration and invasion in glioma cells were impeded by the knock-down of FBXL7 or overexpressed miR-152-5p. Furthermore, the expression of miR-152-5p reduced remarkably in glioma cells and it exerted its activity through targeted FBXL7. Overexpression of miR-152-5p and knock-down of FBXL7 in glioma xenograft models enhanced TMZ-mediated anti-tumour effect and impeded tumour growth. Thus, the miR-152-5p suppressed the progression of glioma and associated tumorigenesis, targeted FBXL7 and increased the effect of TMZ-induced cytotoxicity in glioma cells, further enhancing our knowledge of FBXL7 activity in glioma.

A risk signature with four autophagy-related genes for predicting survival of glioblastoma multiforme

Glioblastoma multiforme (GBM) is a devastating brain tumour without effective treatment. Recent studies have shown that autophagy is a promising therapeutic strategy for GBM. Therefore, it is necessary to identify novel biomarkers associated with autophagy in GBM. In this study, we downloaded autophagy-related genes from Human Autophagy Database (HADb) and Gene Set Enrichment Analysis (GSEA) website. Least absolute shrinkage and selection operator (LASSO) regression and multivariate Cox regression analysis were performed to identify genes for constructing a risk signature. A nomogram was developed by integrating the risk signature with clinicopathological factors. Time-dependent receiver operating characteristic (ROC) curve and calibration plot were used to evaluate the efficiency of the prognostic model. Finally, four autophagy-related genes (DIRAS3, LGALS8, MAPK8 and STAM) were identified and were used for constructing a risk signature, which proved to be an independent risk factor for GBM patients. Furthermore, a nomogram was developed based on the risk signature and clinicopathological factors (IDH1 status, age and history of radiotherapy or chemotherapy). ROC curve and calibration plot suggested the nomogram could accurately predict 1-, 3- and 5-year survival rate of GBM patients. For function analysis, the risk signature was associated with apoptosis, necrosis, immunity, inflammation response and MAPK signalling pathway. In conclusion, the risk signature with 4 autophagy-related genes could serve as an independent prognostic factor for GBM patients. Moreover, we developed a nomogram based on the risk signature and clinical traits which was validated to perform better for predicting 1-, 3- and 5-year survival rate of GBM.

The effect of polysaccharides from Cibotium barometz on enhancing temozolomide-induced glutathione exhausted in human glioblastoma U87 cells, as revealed by 1H NMR metabolomics analysis

Glioblastoma (GBM) is the most malignant central nervous system tumor, with poor prognosis. Temozolomide (TMZ) has been used as a first-line drug for the treatment of GBM for over a decade, but its treatment benefits are limited by acquired resistance. Polysaccharides from Cibotium barometz (CBPs) are polysaccharides purified from the root of Cibotium barometz (L.) J. Sm., possessing sensitizing activity. The purpose of this study was to investigate the anti-cancer effect of CBP from different processing methods on U87 cells using a ¹H NMR-based metabolic approach, complemented with qRT-PCR and flow cytometry, to identify potential markers and discover the targets to explore the underlying mechanism. Cibotium barometz is usually processed under sand heating in clinical applications. Polysaccharides from both the processed (PCBP) and raw (RCBP) C. barometz were prepared, and the effect on enhancing the sensitivity to TMZ was investigated in vitro. CBP can significantly increase the toxicity of TMZ to the U87 cell line, promote apoptosis, enhance cell cycle changes, and arrest cells in S phase, and RCBP demonstrated better activity. Multivariate statistical analyses, such as principal component analysis (PCA) and orthogonal projection to latent structure with discriminant analysis (OPLS-DA), were used to identify metabolic biomarkers, and 12 metabolites in the cell extract samples were clearly identified as altered after RCBP exposure. NMR-based cell metabolomics provided a holistic method for the identification of CBP's apoptosis-enhancing mechanisms and the exploration of its potential applications in preclinical and clinical studies.

Long Non-coding RNA EPIC1 Promotes Cell Proliferation and Motility and Drug Resistance in Glioma

Evidence has revealed that long non-coding RNAs (lncRNAs) are involved in carcinogenesis and tumor progression. lncRNAs play an important role in regulation of numerous cellular processes including cell proliferation, apoptosis, cell cycle, differentiation, and motility. Several studies have demonstrated that lncRNA EPIC1 governs cell growth, cell cycle, migration, invasion, and drug resistance in human malignancies. However, the role of EPIC1 and its underlying molecular mechanisms in glioma have not been investigated. In this study, we determined the function of EPIC1 in glioma cells via upregulation or downregulation of EPIC1. We further dissected the mechanism of EPIC1-mediated tumor progression in glioma. Our results showed that inhibition of EPIC1 suppressed cell viability, induced apoptosis, inhibited cell invasion, and increased cell sensitivity to temozolomide in glioma cells. Consistently, overexpression of EPIC1 exhibited the opposite effects in glioma cells. Moreover, our data suggest that EPIC1 exerts its biological functions via targeting Cdc20 in glioma cells. In line with this, overexpression of Cdc20 reversed the EPIC1-mediated tumor progression in glioma cells. Therefore, targeting EPIC1 might be a useful approach for glioma treatment.

Retrospective and Randomized Analysis of Influence and Correlation of Clinical and Molecular Prognostic Factors in a Mono-Operative Series of 122 Patients with Glioblastoma Treated with STR or GTR

Glioblastoma is a solid, infiltrating, and the most frequent highly malignant primary brain tumor. Our aim was to find the correlation between sex, age, preoperative Karnofsky performance status (KPS), presenting with seizures, and extent of resection (EOR) with overall survival (OS), progression-free survival (PFS), and postoperative KPS, along with the prognostic value of IDH1, MGMT, ATRX, EGFR, and TP53 genes mutations and of Ki67 through the analysis of a single-operator series in order to avoid the biases of a multi-operator series, such as the lack of homogeneity in surgical and adjuvant nonsurgical treatments. A randomized retrospective analysis of 122 patients treated by a single first operator at Sapienza University of Rome was carried out. After surgery, patients followed standard Stupp protocol treatment. Exclusion criteria were: (1) patients with primary brainstem and spinal cord gliomas and (2) patients who underwent partial resections (resection < 90%) or a biopsy exclusively for diagnostic purposes. Statistical analysis with a simultaneous regression model was carried out through the use of SPSS 25^® (IBM). Results showed statistically significant survival increase in four groups: (1) patients treated with gross total resection (GTR) (p < 0.030); (2) patients with mutation of IDH1 (p < 0.0161); (3) patients with methylated MGMT promoter (p < 0.005); (4) patients without EGFR amplification or EGFRvIII mutation (p < 0.035). Higher but not statistically significant survival rates were also observed in: patients <75 years, patients presenting with seizures at diagnosis, patients affected by lesions in noneloquent areas, as well as in patients with ATRX gene mutation and Ki-67 < 10%.

The Plant-Derived Compound Resveratrol in Brain Cancer: A Review

Despite intensive research, malignant brain tumors are among the most difficult to treat due to high resistance to conventional therapeutic approaches. High-grade malignant gliomas, including glioblastoma and anaplastic astrocytoma, are among the most devastating and rapidly growing cancers. Despite the ability of standard treatment agents to achieve therapeutic concentrations in the brain, malignant gliomas are often resistant to alkylating agents. Resveratrol is a plant polyphenol occurring in nuts, berries, grapes, and red wine. Resveratrol crosses the blood‒brain barrier and may influence the central nervous system. Moreover, it influences the enzyme isocitrate dehydrogenase and, more importantly, the resistance to standard treatment via various mechanisms, such as O6-methylguanine methyltransferase. This review summarizes the anticancer effects of resveratrol in various types of brain cancer. Several in vitro and in vivo studies have presented promising results; however, further clinical research is necessary to prove the therapeutic efficacy of resveratrol in brain cancer treatment.

Verteporfin-Loaded Anisotropic Poly(Beta-Amino Ester)-Based Micelles Demonstrate Brain Cancer-Selective Cytotoxicity and Enhanced Pharmacokinetics

BACKGROUND

Nanomedicine can improve traditional therapies by enhancing the controlled release of drugs at targeted tissues in the body. However, there still exists disease- and therapy-specific barriers that limit the efficacy of such treatments. A major challenge in developing effective therapies for one of the most aggressive brain tumors, glioblastoma (GBM), is affecting brain cancer cells while avoiding damage to the surrounding healthy brain parenchyma. Here, we developed poly(ethylene glycol) (PEG)-poly(beta-amino ester) (PBAE) (PEG-PBAE)-based micelles encapsulating verteporfin (VP) to increase tumor-specific targeting.

METHODS

Biodegradable, pH-sensitive micelles of different shapes were synthesized via nanoprecipitation using two different triblock PEG-PBAE-PEG copolymers varying in their relative hydrophobicity. The anti-tumor efficacy of verteporfin loaded in these anisotropic and spherical micelles was evaluated in vitro using patient-derived primary GBM cells.

RESULTS

For anisotropic micelles, uptake efficiency was ~100% in GBM cells (GBM1A and JHGBM612) while only 46% in normal human astrocytes (NHA) at 15.6 nM VP (p ≤ 0.0001). Cell killing of GBM1A and JHGBM612 vs NHA was 52% and 77% vs 29%, respectively, at 24 hrs post-treatment of 125 nM VP-encapsulated in anisotropic micelles (p ≤ 0.0001), demonstrating the tumor cell-specific selectivity of VP. Moreover, anisotropic micelles showed an approximately fivefold longer half-life in blood circulation than the analogous spherical micelles in a GBM xenograft model in mice. In this model, micelle accumulation to tumors was significantly greater for anisotropic micelle-treated mice compared to spherical micelle-treated mice at both 8 hrs (~1.8-fold greater, p ≤ 0.001) and 24 hrs (~2.1-fold greater, p ≤ 0.0001).

CONCLUSION

Overall, this work highlights the promise of a biodegradable anisotropic micelle system to overcome multiple drug delivery challenges and enhance efficacy and safety for the treatment of brain cancer.

Combination treatment of berberine and solid lipid curcumin particles increased cell death and inhibited PI3K/Akt/mTOR pathway of human cultured glioblastoma cells more effectively than did individual treatments

The treatment of glioblastoma is challenging for the clinician, due to its chemotherapeutic resistance. Recent findings suggest that targeting glioblastoma using anti-cancer natural polyphenols is a promising strategy. In this context, curcumin and berberine have been shown to have potent anti-cancer and anti-inflammatory effects against several malignancies. Due to the poor solubility and limited bioavailability, these compounds have limited efficacy for treating cancer. However, use of a formulation of curcumin with higher bioavailability or combining it with berberine as a co-treatment may be proving to be more efficacious against cancer. Recently, we demonstrated that solid lipid curcumin particles (SLCPs) provided more bioavailability and anti-cancer effects in cultured glioblastoma cells than did natural curcumin. Interestingly, a combination of curcumin and berberine has proven to be more effective in inhibiting growth and proliferation of cancer in the liver, breast, lung, bone and blood. However, the effect of combining these drugs for treating glioblastoma, especially with respect to its effect on activating the PI3K/Akt/mTOR pathways has not been studied. Therefore, we decided to assess the co-treatment effects of these drugs on two different glioblastoma cell lines (U-87MG and U-251MG) and neuroblastoma cell lines (SH-SY5Y) derived from human tissue. In this study, we compared single and combination (1:5) treatment of SLCP (20 μM) and berberine (100 μM) on measures of cell viability, cell death markers, levels of c-Myc and p53, along with biomarkers of the PI3K/Akt/mTOR pathways after 24–48 h of incubation. We found that co-treatment of SLCP and berberine produced more glioblastoma cell death, more DNA fragmentation, and significantly decreased ATP levels and reduced mitochondrial membrane potential than did single treatments in both glioblastoma cells lines. In addition, we observed that co-treatment inhibited the PI3K/Akt/mTOR pathway more efficiently than their single treatments. Our study suggests that combination treatments of SLCP and berberine may be a promising strategy to reduce or prevent glioblastoma growth in comparison to individual treatments using either compound.

ANGPTL4 Induces TMZ Resistance of Glioblastoma by Promoting Cancer Stemness Enrichment via the EGFR/AKT/4E-BP1 Cascade

Glioblastoma (GBM) is the most aggressive type of brain tumor, with strong invasiveness and a high tolerance to chemotherapy. Despite the current standard treatment combining temozolomide (TMZ) and radiotherapy, glioblastoma can be incurable due to drug resistance. The existence of glioma stem-like cells (GSCs) is considered the major reason for drug resistance. However, the mechanism of GSC enrichment remains unclear. Herein, we found that the expression and secretion of angiopoietin-like 4 protein (ANGPTL4) were clearly increased in GSCs. The overexpression of ANGPTL4 induced GSC enrichment that was characterized by polycomb complex protein BMI-1 and SRY (sex determining region Y)-box 2 (SOX2) expression, resulting in TMZ resistance in GBM. Furthermore, epidermal growth factor receptor (EGFR) phosphorylation induced 4E-BP1 phosphorylation that was required for ANGPTL4-induced GSC enrichment. In particular, ANGPTL4 induced 4E-BP1 phosphorylation by activating phosphoinositide 3-kinase (PI3K)/AKT and extracellular signal–regulated kinase (ERK) cascades for inducing stemness. To elucidate the mechanism contributing to ANGPTL4 upregulation in GSCs, chromatin immunoprecipitation coupled with sequencing (ChIP-Seq) revealed that specificity protein 4 (Sp4) was associated with the promoter region, −979 to −606, and the luciferase reporter assay revealed that Sp4 positively regulated activity of the ANGPTL4 promoter. Moreover, both ANGPTL4 and Sp4 were highly expressed in GBM and resulted in a poor prognosis. Taken together, Sp4-mediated ANGPTL4 upregulation induces GSC enrichment through the EGFR/AKT/4E-BP1 cascade.

Role of Sonic hedgehog signaling in cell cycle, oxidative stress, and autophagy of temozolomide resistant glioblastoma

The first-line chemotherapy treatment for Glioblastoma (GBM) - the most aggressive and frequent brain tumor - is temozolomide (TMZ). The Sonic hedgehog (SHH) pathway is involved with GBM tumorigenesis and TMZ chemoresistance. The role of SHH pathway inhibition in the potentiation of TMZ's effects using T98G, U251, and GBM11 cell lines is investigated herein. The combination of GANT-61 and TMZ over 72 hr suggested a synergistic effect. All TMZ-resistant cell lines displayed a significant decrease in cell viability, increased DNA fragmentation and loss of membrane integrity. For T98G cells, G₂ /M arrest was observed, while U251 cells presented a significant increase in reactive oxygen species production and catalase activity. All the cell lines presented acidic vesicles formation correlated to Beclin-1 overexpression. The combined treatment also enhanced GLI1 expression, indicating the presence of select resistant cells. The selective inhibition of the SHH pathway potentiated the cytotoxic effect of TMZ, thus becoming a promising in vitro strategy for GBM treatment.

A Novel Multi-Target Small Molecule, LCC-09, Inhibits Stemness and Therapy-Resistant Phenotypes of Glioblastoma Cells by Increasing miR-34a and Deregulating the DRD4/Akt/mTOR Signaling Axis

The management of glioblastomas (GBMs) is challenged by the development of therapeutic resistance and early disease recurrence, despite multi-modal therapy. This may be attributed to the presence of glioma stem cells (GSCs) which are known to survive radio- and chemotherapy, by circumventing death signals and inducing cell re-population. Recent findings suggest GSCs may be enriched by certain treatment modality. These necessitate the development of novel therapeutics capable of targeting GBM cell plasticity and therapy-resistant GSCs. Here, aided by computer-assisted structure characterization and target identification, we predicted that a novel 5-(2′,4′-difluorophenyl)-salicylanilide derivative, LCC-09, could target dopamine receptors and oncogenic markers implicated in GBMs. Bioinformatics data have indicated that dopamine receptor (DRD) 2, DRD4, CD133 and Nestin were elevated in GBM clinical samples and correlated to TMZ (Temozolomide) resistance and increased ALDH (Aldehyde dehydrogenase) activity (3.5–8.9%) as well as enhanced (2.1–2.4-fold) neurosphere formation efficiency in U87MG and D54MG GBM cell lines. In addition, TMZ-resistant GSC phenotype was associated with up-regulated DRD4, Akt, mTOR, β-catenin, CDK6, NF-κB and Erk1/2 expression. LCC-09 alone, or combined with TMZ, suppressed the tumorigenic and stemness traits of TMZ-resistant GBM cells while concomitantly down-regulating DRD4, Akt, mTOR, β-catenin, Erk1/2, NF-κB, and CDK6 expression. Notably, LCC-09-mediated anti-GBM/GSC activities were associated with the re-expression of tumor suppressor miR-34a and reversal of TMZ-resistance, in vitro and in vivo. Collectively, these data lay the foundation for further exploration of the clinical feasibility of administering LCC-09 as single-agent or combinatorial therapy for patients with TMZ-resistant GBMs.

The dual roles of autophagy in gliomagenesis and clinical therapy strategies based on autophagic regulation mechanisms

Autophagy, a self-digestion intracellular catabolic process, plays a crucial role in cellular homeostasis under conditions of starvation, oxidative stress and genotoxic stress. The capability of maintaining homeostasis contributes to preventing malignant behavior in normal cells. Many studies have provided compelling evidence that autophagy is involved in brain tumor recurrence and chemotherapy and radiotherapy resistance. Gliomas, as the primary central nervous system (CNS) tumors, are characterized by rapid, aggressive growth and recurrence and have a poor prognosis and bleak outlook even with modern multimodality strategies involving maximal surgical resection, radiotherapy and alkylating agent-based chemotherapy. Autophagy-associated signaling pathways, such as the extracellular signal-regulated kinase1/2 (ERK1/2) pathway, class I phosphatidylinositol 3-phosphate kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway and nuclear factor kappa-B (NF-κB) pathway, act as tumor suppressors or protect tumor cells against chemotherapy/radiotherapy-induced cytotoxicity in gliomagenesis. Through these pathways, both lethal autophagy and protective autophagy play crucial roles in tumor initiation, chemoresistance and glioma stem cell differentiation. Moreover, lethal autophagy and protective autophagy have been identified as novel therapeutic targets in glioma according to the mechanisms described above. Here, we discuss the multiple impacts of the autophagic response on distinct phases of gliomagenesis and the advanced progress of therapies based on this concept.

MicroRNA-302c enhances the chemosensitivity of human glioma cells to temozolomide by suppressing P-gp expression

Increasing evidence indicates that microRNAs (miRNAs) participate in the regulation of chemoresistance in a variety of cancers including glioma. However, the molecular mechanism underlying the development of chemoresistance in glioma is not well understood. The aim of the present study was to explore the role of miRNAs in the chemosensitivity of glioma cells and the underlying mechanism. By microarray and qRT-PCR, we observed significant down-regulation of microRNA-302c (miR-302c) in the temozolomide (TMZ)-resistant human glioma tissues/cells. The low expression of miR-302c was closely associated with poor prognosis and chemotherapy resistant in patients. miR-302c up-regulation re-sensitized U251MG-TMZ cells and LN229-TMZ cells to TMZ treatment, as evidenced by inhibition of the cell viability, cell migration, and invasion capacity, and promotion of the apoptosis after TMZ treatment. Furthermore, P-glycoprotein (P-gp) was identified as a functional target of miR-302c and this was validated using a luciferase reporter assay. In addition, P-gp was found to be highly expressed in U251MG-TMZ cells and there was an inverse correlation between P-gp and miR-302c expression levels in clinical glioma specimens. Most importantly, we further confirmed that overexpression of P-gp reversed the enhanced TMZ-sensitivity induced by miR-302c overexpression in U251MG-TMZ and LN229-TMZ cells. Our finding showed that up-regulation of miR-302c enhanced TMZ-sensitivity by targeting P-gp in TMZ-resistant human glioma cells, which suggests that miR-302c would be potential therapeutic targets for chemotherapy-resistant glioma patients.

TOPK inhibits autophagy by phosphorylating ULK1 and promotes glioma resistance to TMZ

ULK1, the upper-most protein of the ULK1 complex, is emerging as a crucial node in autophagy induction. However, the regulation of ULK1 is not fully understood. In this study, we identified TOPK (T-LAK cell-originated protein kinase), an oncokinase, as a novel upstream kinase to phosphorylate ULK1. We found that TOPK could directly bind with and phosphorylate ULK1 at Ser469, Ser495, and Ser533. The phosphorylation of ULK1 at Ser469, Ser495, and Ser533 by TOPK decreased the activity and stability of ULK1. In addition, we want to examine the initiation of autophagy because the reduction activity of ULK1 reduces the occurrence of autophagy. We demonstrated that TOPK could inhibit the initiation and progression of autophagy in glioma cells. Furthermore, TOPK inhibition increased the sensitivity of glioma cells to temozolomide (TMZ). This discovery provides insight into the problem of TMZ-resistance in GBM treatment.

DETERMINATION OF MOLECULAR GENETIC MARKERS IN PROGNOSIS OF THE EFFECTIVENESS OF TREATMENT OF MALIGNANT INTRACEREBRAL BRAIN TUMORS

Intracerebral malignant brain tumors remain one of the most complex problems of neuro-oncology. Today, promising results of the use of targeted drugs have been received, which determine the important diagnostic and predictive value of molecular genetic markers of glial and metastatic brain tumors. Aim: The study of the prevalence of MGMT (O6-methylguanine-DNA methyltransferase) and PTEN (phosphatase and tensin homologue deleted on chromosome 10) gene expression by real time polymerase chain reaction in tumor tissue of gliomas and brain metastases. Materials and methods: From thirty patients were received tumor material (29 cases of glioma III-IV degree of anaplasia and one case of metastatic brain lesion of adenocarcinoma). The normalized expression of MGMT and PTEN genes was determined by real-time polymerase chain reaction. Results: In all 30 (100 %) patients with tumor fragments, we determined normalized expression of MGMT and PTEN genes. In most cases, 53 % of the observations (16 out of 30 patients) showed a low normalized expression of MGMT gene (<40 c. u.) and a low normalized PTEN expression rate of 73 % (22 out of 30 patients) (<40 c. u.). The average expression level of the MGMT gene in the range from 40 to 100 c. u. (6/20 % of patients) was considered prognostic favourable for the response to temozolomide chemotherapy. Conclusions: The study of MGMT gene expression, a chemotherapy marker for temozolomide, indicates a trend toward correlation between expression levels and therapeutic efficacy. The study of the expression of the PTEN gene, the blocker of the PI3K / AKT signal pathway, indicates a different degree of expression of this enzyme in the tumour samples studied. The predictive value of the indicator for target therapy is appropriate in comparison with the EGFR mutation. Further profound analysis of the results is required with increasing number of sampling and observation period.

microRNA-181d associated with the methylation status of the MGMT gene in Glioblastoma multiforme cancer stem cells submitted to treatments with ionizing radiation and temozolomide

Despite the increased understanding of the oncological mechanisms underlying Glioblastoma multiforme (GBM) pathophysiology, and recent advances in therapeutic strategies such as maximal surgical resection and post-operative radiotherapy with concomitant and adjuvant temozolomide chemotherapy, the prognosis for patients with brain tumors remains limited. Evidences indicate that the assessment of DNA methylation status in cancer stem cells would allow identifying molecules expressed in these cells, to lead to targeted elimination of this critical population from brain tumors, making the glioblastoma treatment more effective. This study aimed to analyze the role of microRNA-181d associated with the methylation status of the O₆-methylguanine methyl transferase (MGMT) gene in Glioblastoma multiforme cancer stem cells subjected to treatment with temozolomide and ionizing radiation. Such responses were analyzed in terms of cell survival, evaluation of the MGMT gene methylation status by MS-HRM (Methylation-Sensitive High Resolution Melting), and analysis of miRNA-181d and MGMT gene expression by relative quantification of mRNA levels in cancer stem cells subjected to treatment with temozolomide and ionizing radiation, isolated or combined. We showed that ionizing radiation and temozolomide reduced the viability of cancer stem cells from GBM patients, as well as modified MGMT gene and miRNA-181d expression in cancer stem cells, suggesting that miRNA-181d interferes in the glioblastoma cancer stem cell response to treatment with temozolomide and ionizing radiation.

miR-222/GAS5 is involved in DNA damage and cytotoxic effects induced by temozolomide in T98G cell line

Temozolomide (TMZ), a therapeutic DNA alkylator that can cause lethal DNA damage in cancer cells, is widely used for the standard chemotherapy against glioblastoma. However, long-term treatment with TMZ often causes drug resistance and poor prognosis, the mechanism of which remains largely unclear. This study aimed to investigate the possible role of miR-222/GAS5 axis on DNA damage and cytotoxic effects induced by TMZ in glioblastoma cells (T98G). Data suggest that the DNA comet tail length of T98G is positively correlated with the levels of miR-222 (R²  = 0.9808, P < 0.05), and negatively correlated with the levels of GAS5 (R²  = 0.8903, P < 0.05). The optical density value of T98G is negatively correlated with the levels of miR-222 (R²  = 0.7848, P < 0.05), and positively correlated with the levels of GAS5 (R²  = 0.6886, P < 0.05). Furthermore, comet tail length and optical density value are negatively and positively correlated with the levels of O-6-methylguanine-DNA methyltransferase, respectively (R²  = 0.8462, P < 0.05; R²  = 0.7018, P < 0.05). In conclusion, miR-222/GAS5 is involved in DNA damage and cytotoxic effects induced by TMZ, which means that miR-222/GAS5 may have great potential of being used as a biomarker for screening of chemotherapeutic alkylators.