Search

Thioredoxin Related Transmembrane Protein 1 (TMX1) encodes a thiol-disulfide oxidoreductase and regulates cleavage, formation, or isomerization of disulfide bonds among cysteine residues in proteins. Using bioinformatic analysis, we firstly prove TMX1 is significantly upregulated in lower-grade gliomas (LGGs) and associated with poor prognosis of LGG patients. Besides, it's also highly expressed in higher WHO grade, 1p/19q non-co-deleted and isocitrate dehydrogenase (IDH) wildtype LGGs, thus we established a TMX1-based nomogram model, which exhibits a strong and stable predictive ability in the prognosis of LGG patients. Then, we also noticed that TMX1 was significantly associated with the immune cell infiltrations in LGGs, especially in B cell, CD8+ T cell, CD4+T cell, dendritic cell, macrophage and neutrophil. Meanwhile, it was also highly correlated to the expressions of MKI67, PCNA, PROM1 and SOX2 in LGGs, and that higher TMX1 LGGs showed a stronger resistance to temozolomide (TMZ). Finally, in our in vitro and in vivo experiments, we verified that TMX1 is highly expressed in LGG patients clinically, and it not only regulates the proliferative ability of SW1088 and SW1783 cells both in vitro and in vivo, it can also be inhibited to increase the TMZ therapy sensitivity in vivo. These results revealed that TMX1 acts as a strong prognostic biomarker in LGGs, and targeting TMX1 can be an efficient way to increase the TMZ therapy in LGG patients. [ABSTRACT FROM AUTHOR]

Temozolomide (TMZ) stands as the primary chemotherapeutic drug utilized in clinical glioma treatment, particularly for high-grade glioblastoma (GBM). However, the emergence of TMZ resistance in GBM poses a significant hurdle to its clinical efficacy. Our objective was to elucidate the role of deubiquitinating enzymes (DUBs) in GBM cell resistance to TMZ. We employed the broad-spectrum DUBs inhibitor G5 to investigate the function of DUBs in TMZ cytotoxicity against GBM cells. Eighty-two GBM cell lines with specified DUBs knockout were generated and subjected to CCK-8 assays to assess cell proliferation and TMZ resistance. Furthermore, the association between DUBs and TMZ resistance in GBM cells, along with the modulation of autophagic flux, was examined. The pan-DUBs inhibitor G5 demonstrated the ability to induce cell death and enhance TMZ toxicity in GBM cells. Subsequently, we identified potential DUBs involved in regulating GBM cell proliferation and TMZ resistance. The impact of DUBs knockout on TMZ cytotoxicity was found to be associated with their regulation of TMZ-induced autophagy. In summary, our study provides primary insights into the role of DUBs in GBM cell proliferation and TMZ resistance, and contributes to a deeper understanding of the complex function of DUBs genes underlying TMZ resistance in GBM cells. [ABSTRACT FROM AUTHOR]

Glioblastoma (GB) is the most common and most aggressive primary brain tumor in adults, with an overall survival almost 14.6 months. Optimal resection followed by combined temozolomide chemotherapy and radiotherapy, also known as Stupp protocol, remains the standard of treatment; nevertheless, resistance to temozolomide, which can be obtained throughout many molecular pathways, is still an unsurpassed obstacle. Several factors influence the efficacy of temozolomide, including the involvement of other DNA repair systems, aberrant signaling pathways, autophagy, epigenetic modifications, microRNAs, and extracellular vesicle production. The blood–brain barrier, which serves as both a physical and biochemical obstacle, the tumor microenvironment's pro-cancerogenic and immunosuppressive nature, and tumor-specific characteristics such as volume and antigen expression, are the subject of ongoing investigation. In this review, preclinical and clinical data about temozolomide resistance acquisition and possible ways to overcome chemoresistance, or to treat gliomas without restoration of chemosensitinity, are evaluated and presented. The objective is to offer a thorough examination of the clinically significant molecular mechanisms and their intricate interrelationships, with the aim of enhancing understanding to combat resistance to TMZ more effectively. [ABSTRACT FROM AUTHOR]

Temozolomide (TMZ) resistance remains the major obstacle in the treatment of glioblastoma (GBM). Lactylation is a novel post‐translational modification that is involved in various tumors. However, whether lactylation plays a role in GBM TMZ resistance remains unclear. Here it is found that histone H3K9 lactylation (H3K9la) confers TMZ resistance in GBM via LUC7L2‐mediated intron 7 retention of MLH1. Mechanistically, lactylation is upregulated in recurrent GBM tissues and TMZ‐resistant cells, and is mainly concentrated in histone H3K9. Combined multi‐omics analysis, including CUT&Tag, SLAM‐seq, and RNA‐seq, reveals that H3K9 lactylation is significantly enriched in the LUC7L2 promoter and activates LUC7L2 transcription to promote its expression. LUC7L2 mediates intron 7 retention of MLH1 to reduce MLH1 expression, and thereby inhibit mismatch repair (MMR), ultimately leading to GBM TMZ resistance. Of note, it is identified that a clinical anti‐epileptic drug, stiripentol, which can cross the blood–brain barrier and inhibit lactate dehydrogenase A/B (LDHA/B) activity, acts as a lactylation inhibitor and renders GBM cells more sensitive to TMZ in vitro and in vivo. These findings not only shed light on the mechanism of lactylation in GBM TMZ resistance but also provide a potential combined therapeutic strategy for clinical GBM treatment. [ABSTRACT FROM AUTHOR]

Glioblastoma (GBM) is the most common aggressive central nervous system cancer. GBM has a high mortality rate, with a median survival time of 12–15 months after diagnosis. A poor prognosis and a shorter life expectancy may result from resistance to standard treatments such as radiation and chemotherapy. Temozolomide has been the mainstay treatment for GBM, but unfortunately, there are high rates of resistance with GBM bypassing apoptosis. A proposed mechanism for bypassing apoptosis is decreased ceramide levels, and previous research has shown that within GBM cells, B cell lymphoma 2-like 13 (BCL2L13) can inhibit ceramide synthase. This review aims to discuss the causes of resistance in GBM cells, followed by a brief description of BCL2L13 and an explanation of its mechanism of action. Further, lipids, specifically ceramide, will be discussed concerning cancer and GBM cells, focusing on ceramide synthase and its role in developing GBM. By gathering all current information on BCL2L13 and ceramide synthase, this review seeks to enable an understanding of these pieces of GBM in the hope of finding an effective treatment for this disease. [ABSTRACT FROM AUTHOR]

ABSTRACTGlioma is the most common primary malignant brain tumor in adults and accounts for approximately 80% of brain and central nervous system tumors. In 2021, the World Health Organization (WHO) published a new taxonomy for glioma based on its histological features and molecular alterations. Isocitrate dehydrogenase (IDH) catalyzes the decarboxylation of isocitrate, a critical metabolic reaction in energy generation in cells. Mutations in the IDH genes interrupt cell differentiation and serve as molecular biomarkers that can be used to classify gliomas. For example, the mutant IDH is widely detected in low-grade gliomas, whereas the wild type is in high-grade ones, including glioblastomas. Long non-coding RNAs (lncRNAs) are epigenetically involved in gene expression and contribute to glioma development. To investigate the potential use of lncRNAs as biomarkers, we examined lncRNA dysregulation dependent on the IDH mutation status. We found that several lncRNAs, namely, AL606760.2, H19, MALAT1, PVT1 and SBF2-AS1 may function as glioma risk factors, whereas AC068643.1, AC079228.1, DGCR5, FAM13A-AS1, HAR1A and WDFY3-AS2 may have protective effects. Notably, H19, MALAT1, PVT1, and SBF2-AS1 have been associated with temozolomide resistance in glioma patients. This review study suggests that targeting glioma-associated lncRNAs might aid the treatment of glioma.

Backgroud: Glioblastoma multiforme (GBM) is among the most aggressive cancers, with current treatments limited in efficacy. A significant hurdle in the treatment of GBM is the resistance to the chemotherapeutic agent temozolomide (TMZ). The methylation status of the MGMT promoter has been implicated as a critical biomarker of response to TMZ. Methods: To explore the mechanisms underlying resistance, we developed two TMZ‐resistant GBM cell lines through a gradual increase in TMZ exposure. Transcriptome sequencing of TMZ‐resistant cell lines revealed that alterations in histone post‐translational modifications might be instrumental in conferring TMZ resistance. Subsequently, multi‐omics analysis suggests a strong association between histone H3 lysine 9 acetylation (H3K9ac) levels and TMZ resistance. Results: We observed a significant correlation between the expression of H3K9ac and MGMT, particularly in the unmethylated MGMT promoter samples. More importantly, our findings suggest that H3K9ac may enhance MGMT transcription by facilitating the recruitment of the SP1 transcription factor to the MGMT transcription factor binding site. Additionally, by analyzing single‐cell transcriptomics data from matched primary and recurrent GBM tumors treated with TMZ, we modeled the molecular shifts occurring upon tumor recurrence. We also noted a reduction in tumor stem cell characteristics, accompanied by an increase in H3K9ac, SP1, and MGMT levels, underscoring the potential role of H3K9ac in tumor relapse following TMZ therapy. Conclusions: The increase in H3K9ac appears to enhance the recruitment of the transcription factor SP1 to its binding sites within the MGMT locus, consequently upregulating MGMT expression and driving TMZ resistance in GBM. [ABSTRACT FROM AUTHOR]

Objective: To discuss the effect of general transcription factor 2I (GTF2I) on the chemotherapeutic resistance to temozolomide in the glioblastoma multiforme (GBM), and to clarify its mechanism. Methods: Bioinformatics analysis was used to identify the common transcription factors for DNA methyltransferase 1 (DNMT1), damage-specific DNA binding protein 1 (DDB1), chromobox protein homolog 5 (CBX5), and xeroderma pigmentosum complementation group C (XPC) in GBM tissue using the transcription factor prediction website (PROMO website); correlation analysis and survival analysis for DDB1, CBX5, XPC, and DNMT1 with GTF2I and methylguanine methyltransferase (MGMT) were conducted based on The Cancer Genome Atlas (TCGA) Database; small interfering RNAs (siRNAs) were used to transfect and silence the gene expression of MGMT and GTF2I in the human T98 GBM cells and LN229 glioma cells; real-time fluorescence quantitative PCR (RT-qPCR) method was used to detect the expression level of the gene mRNA. After silencing the GTF2I gene, plate clone formation assay was used to detect the colon forming ability of the tumor cells, and CCK-8 assay was used to detect the sensitivity of the cells to temozolomide. Results: The bioinformatics analysis results showed that the expression levels of DDB1, CBX5, XPC, and DNMT1 were significantly positively correlated with the expression level of GTF2I in GBM tissue (P<0. 05), and were negatively correlated with the expression level of MGMT (P<0. 05). The expression level of GTF2I was significantly negatively correlated with the expression level of MGMT (P<0. 05). Excluding the GBM patients who did not receive temozolomide treatment, the survival analysis results indicated that the patients with high expression of GTF2I had a decreased overall survival time. After silencing the MGMT gene, the expression levels of GTF2I, DDB1, CBX5, and XPC mRNA in the human brain glioma T98 cells were increased (P<0. 001); after silencing the GTF2I gene, the expression level of MGMT mRNA in the human brain glioma LN229 cells was increased (P<0. 05), while the expression levels of DDB1, CBX5, XPC, and DNMT1 mRNA were significantly decreased (P<0. 05 or P<0. 001). The plate clone formation assay results showed that there was no significant difference in the clone formation ability of the cells before and after silencing the GTF2I gene (P=0. 138). The CCK-8 assay results showed that compared with control group，the viability of the cells in observation group was decreased (P<0. 05). Conclusion: The transcription factor GTF2I regulates the expressions of key DNA damage repair protein mRNA, including MGMT, DDB1, CBX5, and XPC, and is involved in the chemotherapeutic resistance of the GBM cells to temozolomide; GTF2I may represent a potential new therapeutic target for the GBM. [ABSTRACT FROM AUTHOR]

Protein phosphatase magnesium‐dependent 1B (PPM1B) functions as IKKβ phosphatases to terminate nuclear factor kappa B (NF‐κB) signaling. NF‐κB signaling was constitutively activated in glioma cells. At present, little is known about the role of PPM1B in glioma. In the current study, we found that the expression of PPM1B was reduced in glioma tissues and cells, and decreased expression of PPM1B was related to poor overall survival of patients. Overexpression of PPM1B inhibited the proliferation and promoted apoptosis of glioma cells. Moreover, PPM1B overexpression reduced the phosphorylation of IKKβ and inhibited the nuclear localization of NF‐κBp65. PDTC, an inhibitor of NF‐κB signaling, reversed PPM1B‐knockdown‐induced cell proliferation. Furthermore, overexpression of PPM1B enhanced the sensitivity of glioma cells to temozolomide. In vivo experiments showed that overexpression of PPM1B could inhibit tumor growth, improve the survival rate of nude mice, and enhance the sensitivity to temozolomide. In conclusion, PPM1B suppressed glioma cell proliferation and the IKKβ‐NF‐κB signaling pathway, and enhanced temozolomide sensitivity of glioma cells. [ABSTRACT FROM AUTHOR]

Exosomally transferred circular RNAs (circRNAs) are critical in cancer. However, the study of exosomal circRNAs in glioma resistance remains limited. Here, we further investigated the function and mechanism of exosomal circular RNA NT5E (circNT5E) in temozolomide-resistant glioma cells (TMZ-GCs). Exosomes were isolated from TMZ-GCs and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting. CircNT5E, microRNA-153 (miR-153), and heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) levels were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in TMZ-sensitive and TMZ-resistant GCs and in treated TMZ-GCs. In addition, the colocalization of circNT5E and miR-153 was confirmed by fluorescence in situ hybridization (FISH) and dual-luciferase reporter assays. Internalization of exosomes was observed by immunofluorescence staining. TMZ resistance, proliferation, and pAKTser473 protein levels were evaluated by a Cell Counting Kit-8 (CCK-8) assay, an EdU incorporation assay, and Western blotting, respectively. In addition, tumor growth was examined using a xenograft tumor model in nude mice. We first proved that circNT5E was highly abundant in exosomes derived from TMZ-GCs. Then, we discovered that circNT5E could serve as a miR-153 sponge. Finally, knockdown of circNT5E reduced TMZ resistance and cell proliferation and downregulated AKTser473 phosphorylation by targeting miR-153 in TMZ-GCs. Moreover, our data revealed that exosomes derived from TMZ-GCs also had obvious effects on inducing the TMZ resistance and proliferation of GCs. Moreover, we revealed that the packaging of circNT5E into exosomes can be driven by hnRNP A1. Collectively, our findings proved that exosomal circNT5E transferred in a manner mediated by hnRNPA1 could accelerate TMZ resistance by targeting miR-153 in GCs, indicating that exosomal circNT5E is a therapeutic target for TMZ-resistant glioma. [ABSTRACT FROM AUTHOR]

Temozolomide resistance is a major cause of recurrence and poor prognosis in neuroglioma. Recently, growing evidence has suggested that mitophagy is involved in drug resistance in various tumor types. However, the role and molecular mechanisms of mitophagy in temozolomide resistance in glioma remain unclear. In this study, mitophagy levels in temozolomide-resistant and -sensitive cell lines were evaluated. The mechanisms underlying the regulation of mitophagy were explored through RNA sequencing, and the roles of differentially expressed genes in mitophagy and temozolomide resistance were investigated. We found that mitophagy promotes temozolomide resistance in glioma. Specifically, small ubiquitin-like modifier specific protease 6 (SENP6) promoted temozolomide resistance in glioma by inducing mitophagy. Protein-protein interactions between SENP6 and the mitophagy executive protein PTEN-induced kinase 1 (PINK1) resulted in a reduction in small ubiquitin-like modifier 2 (SUMO2)ylation of PINK1, thereby enhancing mitophagy. Our study demonstrates that by inducing mitophagy, the interaction of SENP6 with PINK1 promotes temozolomide resistance in glioblastoma. Therefore, targeting SENP6 or directly regulating mitophagy could be a potential and novel therapeutic target for reversing temozolomide resistance in glioma. [ABSTRACT FROM AUTHOR]

Chemotherapy using temozolomide is the standard treatment for patients with glioblastoma. Despite treatment, prognosis is still poor largely due to the emergence of temozolomide resistance. This resistance is closely linked to the widely recognized inter- and intra-tumoral heterogeneity in glioblastoma, although the underlying mechanisms are not yet fully understood. To induce temozolomide resistance, we subjected 21 patient-derived glioblastoma cell cultures to Temozolomide treatment for a period of up to 90 days. Prior to treatment, the cells' molecular characteristics were analyzed using bulk RNA sequencing. Additionally, we performed single-cell RNA sequencing on four of the cell cultures to track the evolution of temozolomide resistance. The induced temozolomide resistance was associated with two distinct phenotypic behaviors, classified as "adaptive" (ADA) or "non-adaptive" (N-ADA) to temozolomide. The ADA phenotype displayed neurodevelopmental and metabolic gene signatures, whereas the N-ADA phenotype expressed genes related to cell cycle regulation, DNA repair, and protein synthesis. Single-cell RNA sequencing revealed that in ADA cell cultures, one or more subpopulations emerged as dominant in the resistant samples, whereas N-ADA cell cultures remained relatively stable. The adaptability and heterogeneity of glioblastoma cells play pivotal roles in temozolomide treatment and contribute to the tumor's ability to survive. Depending on the tumor's adaptability potential, subpopulations with acquired resistance mechanisms may arise. [ABSTRACT FROM AUTHOR]

Abstract Background Glioblastoma multiforme (GBM) is characterized by an unfavorable prognosis for patients affected. During standard-of-care chemotherapy using temozolomide (TMZ), tumors acquire resistance thereby causing tumor recurrence. Thus, deciphering essential molecular pathways causing TMZ resistance are of high therapeutic relevance. Methods Mass spectrometry based proteomics were used to study the GBM proteome. Immunohistochemistry staining of human GBM tissue for either calpain-1 or -2 was performed to locate expression of proteases. In vitro cell based assays were used to measure cell viability and survival of primary patient-derived GBM cells and established GBM cell lines after TMZ ± calpain inhibitor administration. shRNA expression knockdowns of either calpain-1 or calpain-2 were generated to study TMZ sensitivity of the specific subunits. The Comet assay and ɣH2AX signal measurements were performed in order to assess the DNA damage amount and recognition. Finally, quantitative real-time PCR of target proteins was applied to differentiate between transcriptional and post-translational regulation. Results Calcium-dependent calpain proteases, in particular calpain-2, are more abundant in glioblastoma compared to normal brain and increased in patient-matched initial and recurrent glioblastomas. On the cellular level, pharmacological calpain inhibition increased the sensitivities of primary glioblastoma cells towards TMZ. A genetic knockdown of calpain-2 in U251 cells led to increased caspase-3 cleavage and sensitivity to neocarzinostatin, which rapidly induces DNA strand breakage. We hypothesize that calpain-2 causes desensitization of tumor cells against TMZ by preventing strong DNA damage and subsequent apoptosis via post-translational TP53 inhibition. Indeed, proteomic comparison of U251 control vs. U251 calpain-2 knockdown cells highlights perturbed levels of numerous proteins involved in DNA damage response and downstream pathways affecting TP53 and NF-κB signaling. TP53 showed increased protein abundance, but no transcriptional regulation. Conclusion TMZ-induced cell death in the presence of calpain-2 expression appears to favor DNA repair and promote cell survival. We conclude from our experiments that calpain-2 expression represents a proteomic mode that is associated with higher resistance via “priming” GBM cells to TMZ chemotherapy. Thus, calpain-2 could serve as a prognostic factor for GBM outcome.

Abstract Although temozolomide (TMZ) provides significant clinical benefit for glioblastoma (GBM), responses are limited by the emergence of acquired resistance. Here, we demonstrate that exosomal circCABIN1 secreted from TMZ-resistant cells was packaged into exosomes and then disseminated TMZ resistance of receipt cells. CircCABIN1 could be cyclized by eukaryotic translation initiation factor 4A3 (EIF4A3) and is highly expressed in GBM tissues and glioma stem cells (GSCs). CircCABIN1 is required for the self-renewal maintenance of GSCs to initiate acquired resistance. Mechanistically, circCABIN1 regulated the expression of olfactomedin-like 3 (OLFML3) by sponging miR-637. Moreover, upregulation of OLFML3 activating the ErbB signaling pathway and ultimately contributing to stemness reprogramming and TMZ resistance. Treatment of GBM orthotopic mice xenografts with engineered exosomes targeting circCABIN1 and OLFML3 provided prominent targetability and had significantly improved antitumor activity of TMZ. In summary, our work proposed a novel mechanism for drug resistance transmission in GBM and provided evidence that engineered exosomes are a promising clinical tool for cancer prevention and therapy. Graphical Abstract

Treatment for the deadly brain tumor glioblastoma (GBM) has been improved through the non-invasive addition of alternating electric fields, called tumor treating fields (TTFields). Improving both progression-free and overall survival, TTFields are currently approved for treatment of recurrent GBMs as a monotherapy and in the adjuvant setting alongside TMZ for newly diagnosed GBMs. These TTFields are known to inhibit mitosis, but the full molecular impact of TTFields remains undetermined. Therefore, we sought to understand the ability of TTFields to disrupt the growth patterns of and induce kinomic landscape shifts in TMZ-sensitive and -resistant GBM cells. We determined that TTFields significantly decreased the growth of TMZ-sensitive and -resistant cells. Kinomic profiling predicted kinases that were induced or repressed by TTFields, suggesting possible therapy-specific vulnerabilities. Serving as a potential pro-survival mechanism for TTFields, kinomics predicted the increased activity of platelet-derived growth-factor receptor alpha (PDGFRα). We demonstrated that the addition of the PDGFR inhibitor, crenolanib, to TTFields further reduced cell growth in comparison to either treatment alone. Collectively, our data suggest the efficacy of TTFields in vitro and identify common signaling responses to TTFields in TMZ-sensitive and -resistant populations, which may support more personalized medicine approaches. [ABSTRACT FROM AUTHOR]

Objective To explore the effect of C1QBP on the resistance of glioblastoma (GBM) to temozolomide (TMZ) through regulating mitochondrial function. Methods The semi-inhibitory index of GBM cell line U251 and TMZ-resistance cell line U251 (U251/TMZ) were detected by MTT assay. Expression of C1QBP in U251 and U251/ TMZ cells were detected by immunofluorescence and Western Blot. U251/TMZ + OE-C1QBP group was constructed by CIQBP overexpression transfection. The mRNA expression level of C1QBP in each group was detected by real-time fluorescence quantitative PCR (qRT-PCR). The semi-inhibitory index of U251/TMZ + OE-C1QBP group was detected by MTT assay. The apoptosis level of cells in each group were detected by flow cytometry. The changes of mitochondrial membrane potential were observed under fluorescence microscope. Results Compared with U251 cell line, U251/TMZ cell line had a higher semi-inhibitory index and protein expression level of C1QBP. The semi- inhibitory index of U251/TMZ + OE-C1QBP cell line was the highest. The mRNA expression level of C1QBP in U251, U251/TMZ and U251/TMZ + OE-C1QBP cells increased in turn. The level of apoptosis decreased in turn, and the expression of mitochondrial membrane potential increased. Conclusions The expression level of CIQBP is related to the resistance of GBM to TMZ. With the increase of CIQBP expression level, the function of mitochondrial membrane potential is enhanced, and the resistance of GBM to TMZ is also increasing. [ABSTRACT FROM AUTHOR]

Aim: To investigate the use of nanoparticle (NP)-encapsulated injectable thermosensitive hydrogel-formed nanogel for inhibition of postsurgical residual temozolomide (TMZ)-resistant glioblastoma (GBM) recurrence. Materials & methods: Curcumin (Cur) was coloaded with TMZ into PEG-PLGA NPs, then NPs were further encapsulated into a thermosensitive hydrogel to form a nanogel, which was injected into the resection cavity of the GBM postsurgery. Results: The prepared nanogel displayed excellent drug-loading capacity and long-term drug release. Estimated survival characteristics demonstrated that the nanogel could play a significant role in TMZ-resistant tumor inhibition with low drug-induced toxicity. The originally designed ratio of Cur/TMZ was sustained, making it an effective therapeutic outcome. Conclusion: Cur-combined TMZ-formed nanogels can be a promising candidate for the local inhibition of GBM recurrence. In this study, the animal model used was rats suffering residual brain tumor after resection. The selected drugs were temozolomide, a first-line chemotherapeutic drug for the clinical treatment of glioma, and curcumin, an extract from the ginger plant. With the use of temozolomide, brain glioma cells gradually develop resistance, resulting in poor efficacy of temozolomide. Therefore, the purpose of this study was to construct a drug-delivery system for temozolomide-resistant brain glioma residual tumor after surgery, namely, a temperature-sensitive gel containing drug-carrying nanopreparations – the so-called nanogels. This drug-delivery system can directly deliver drugs to residual tumor cells in situ after surgery. In situ drug-delivery systems can reduce the dose of drugs consumed and increase their potency compared to oral or intravenous administration. [ABSTRACT FROM AUTHOR]

Temozolomide (TMZ)-based chemotherapy plays a central part in glioma treatment. However, prominent resistance to TMZ is a major change by now. In this study, expression and prognosis of SRSF4 were analyzed using multiple public datasets. Therapeutic efficacy against TMZ resistance was determined by assessing colony formation, flow cytometry, and western blot assays. Bio-informational analysis, immunofluorescence (IF), and western blot assays were performed to evaluate double strand break repair. An orthotopic xenograft model was used to exam the functional role of SRSF4. Here, we found that SRSF4 expression was associated with histological grade, IDH1 status, 1p/19q codeletion, molecular subtype, tumor recurrence, and poor prognosis. SRSF4 promotes TMZ resistance through positively regulating MDC1, thereby accelerating double strand break repair. Targeting SRSF4 could significantly improve chemosensitivity. Taken together, our collective findings highlight an important role of SRSF4 in the regulation of TMZ resistance by modulation of double strand break repair. [ABSTRACT FROM AUTHOR]

Adiponectin (ADN) regulates DNA synthesis, cell apoptosis and cell cycle to participate in the pathology and progression of glioblastoma. The present study aimed to further explore the effect of ADN on temozolomide (TMZ) resistance in glioblastoma and the underlying mechanism of action. Glioblastoma cell lines (U251 and U87-MG cells) were treated with ADN and TMZ at different concentrations; subsequently, 3.0 µg/ml ADN and 1.0 mM TMZ were selected as the optimal concentrations for the experimental conditions. LY294002 (a PI3K inhibitor) was added to ADN or ADN + TMZ-treated glioblastoma cell lines. Cell growth rate was determined using the Cell Counting Kit-8 assay, the apoptotic rate and cell cycle were evaluated using Annexin V/propidium iodide and cell cycle assays, and p-Akt (Thr308), p-Akt (Ser473), Akt, p-mTOR, c-caspase 3, caspase 3, Bax, cyclin B1 and cyclin D1 expression was determined by western blotting. Adiponectin receptor (ADIPOR) 1 and ADIPOR2 were expressed in glioblastoma cell lines. The glioblastoma cell line growth rate was increased by ADN in a concentration- and time-dependent manner. ADN inhibited glioblastoma cell line apoptosis and facilitated cell cycle. Of note, ADN activated the Akt/mTOR pathway and the addition of LY294002 reversed the effect of ADN, indicating that ADN activated the Akt/mTOR pathway to suppress apoptosis and promote cell cycle in glioblastoma cell lines. Notably, TMZ inhibited glioblastoma cell line growth, promoted apoptosis and increased G2 phase cell cycle arrest. However, the addition of ADN reversed the effect of TMZ in glioblastoma cell lines, disclosing that ADN induced TMZ resistance. Markedly, ADN-mediated TMZ resistance was further attenuated by LY294002, suggesting that ADN activated the Akt/mTOR pathway to induce TMZ resistance in glioblastoma cell lines. In conclusion, ADN activated the Akt/mTOR pathway to facilitate cell cycle, inhibit cell apoptosis and induce TMZ resistance in glioblastoma. [ABSTRACT FROM AUTHOR]

Background: Glioblastoma multiforme (GBM) is characterized by an unfavorable prognosis for patients affected. During standard-of-care chemotherapy using temozolomide (TMZ), tumors acquire resistance thereby causing tumor recurrence. Thus, deciphering essential molecular pathways causing TMZ resistance are of high therapeutic relevance. Methods: Mass spectrometry based proteomics were used to study the GBM proteome. Immunohistochemistry staining of human GBM tissue for either calpain-1 or -2 was performed to locate expression of proteases. In vitro cell based assays were used to measure cell viability and survival of primary patient-derived GBM cells and established GBM cell lines after TMZ ± calpain inhibitor administration. shRNA expression knockdowns of either calpain-1 or calpain-2 were generated to study TMZ sensitivity of the specific subunits. The Comet assay and ɣH2AX signal measurements were performed in order to assess the DNA damage amount and recognition. Finally, quantitative real-time PCR of target proteins was applied to differentiate between transcriptional and post-translational regulation. Results: Calcium-dependent calpain proteases, in particular calpain-2, are more abundant in glioblastoma compared to normal brain and increased in patient-matched initial and recurrent glioblastomas. On the cellular level, pharmacological calpain inhibition increased the sensitivities of primary glioblastoma cells towards TMZ. A genetic knockdown of calpain-2 in U251 cells led to increased caspase-3 cleavage and sensitivity to neocarzinostatin, which rapidly induces DNA strand breakage. We hypothesize that calpain-2 causes desensitization of tumor cells against TMZ by preventing strong DNA damage and subsequent apoptosis via post-translational TP53 inhibition. Indeed, proteomic comparison of U251 control vs. U251 calpain-2 knockdown cells highlights perturbed levels of numerous proteins involved in DNA damage response and downstream pathways affecting TP53 and NF-κB signaling. TP53 showed increased protein abundance, but no transcriptional regulation. Conclusion: TMZ-induced cell death in the presence of calpain-2 expression appears to favor DNA repair and promote cell survival. We conclude from our experiments that calpain-2 expression represents a proteomic mode that is associated with higher resistance via "priming" GBM cells to TMZ chemotherapy. Thus, calpain-2 could serve as a prognostic factor for GBM outcome. [ABSTRACT FROM AUTHOR]

Although temozolomide (TMZ) provides significant clinical benefit for glioblastoma (GBM), responses are limited by the emergence of acquired resistance. Here, we demonstrate that exosomal circCABIN1 secreted from TMZ-resistant cells was packaged into exosomes and then disseminated TMZ resistance of receipt cells. CircCABIN1 could be cyclized by eukaryotic translation initiation factor 4A3 (EIF4A3) and is highly expressed in GBM tissues and glioma stem cells (GSCs). CircCABIN1 is required for the self-renewal maintenance of GSCs to initiate acquired resistance. Mechanistically, circCABIN1 regulated the expression of olfactomedin-like 3 (OLFML3) by sponging miR-637. Moreover, upregulation of OLFML3 activating the ErbB signaling pathway and ultimately contributing to stemness reprogramming and TMZ resistance. Treatment of GBM orthotopic mice xenografts with engineered exosomes targeting circCABIN1 and OLFML3 provided prominent targetability and had significantly improved antitumor activity of TMZ. In summary, our work proposed a novel mechanism for drug resistance transmission in GBM and provided evidence that engineered exosomes are a promising clinical tool for cancer prevention and therapy. [ABSTRACT FROM AUTHOR]

Simple Summary: We compared gene expression in matched primary and recurrent glioblastoma samples, with a focus on those harbouring extra copies of the gene called EGFR (amplified samples). Our results show that in the setting of newly diagnosed glioblastoma, EGFR-amplified compared to EGFR non-amplified tumours display altered gene expression in the EGFR pathway, but this distinction is lost in the setting of recurrent disease. We validated this finding in an independent dataset. EGFR pathway overexpression may be a common mechanism underlying glioblastoma recurrence. Background: Glioblastoma mortality is driven by tumour progression or recurrence despite administering a therapeutic arsenal consisting of surgical resection, radiation, and alkylating chemotherapy. The genetic changes underlying tumour progression and chemotherapy resistance are poorly understood. Methods: In this study, we sought to define the relationship between EGFR amplification status, EGFR mRNA expression, and EGFR pathway activity. We compared RNA-sequencing data from matched primary and recurrent tumour samples (n = 40 patients, 20 with EGFR amplification). Results: In the setting of glioblastoma recurrence, the EGFR pathway was overexpressed regardless of EGFR-amplification status, suggesting a common genomic endpoint in recurrent glioblastoma, although EGFR amplification did associate with higher EGFR mRNA expression. Three of forty patients in the study cohort had EGFR-amplified tumours and received targeted EGFR therapy. Their molecular subtypes and clinical outcomes did not significantly differ from patients who received conventional chemotherapy. Conclusion: Our findings suggest that while the EGFR amplification may confer a unique molecular profile in primary glioblastoma, pathway analysis reveals upregulation of the EGFR pathway in recurrence, regardless of amplification status. As such, the EGFR pathway may be a key mediator of glioblastoma progression. [ABSTRACT FROM AUTHOR]

Glioma is the most common primary malignant brain tumor in adults and accounts for approximately 80% of brain and central nervous system tumors. In 2021, the World Health Organization (WHO) published a new taxonomy for glioma based on its histological features and molecular alterations. Isocitrate dehydrogenase (IDH) catalyzes the decarboxylation of isocitrate, a critical metabolic reaction in energy generation in cells. Mutations in the IDH genes interrupt cell differentiation and serve as molecular biomarkers that can be used to classify gliomas. For example, the mutant IDH is widely detected in low-grade gliomas, whereas the wild type is in high-grade ones, including glioblastomas. Long non-coding RNAs (lncRNAs) are epigenetically involved in gene expression and contribute to glioma development. To investigate the potential use of lncRNAs as biomarkers, we examined lncRNA dysregulation dependent on the IDH mutation status. We found that several lncRNAs, namely, AL606760.2, H19, MALAT1, PVT1 and SBF2-AS1 may function as glioma risk factors, whereas AC068643.1, AC079228.1, DGCR5, FAM13A-AS1, HAR1A and WDFY3-AS2 may have protective effects. Notably, H19, MALAT1, PVT1, and SBF2-AS1 have been associated with temozolomide resistance in glioma patients. This review study suggests that targeting glioma-associated lncRNAs might aid the treatment of glioma. [ABSTRACT FROM AUTHOR]

Autophagy is a critical cellular process involved in the degradation and recycling of cytoplasmic components, playing a dual role in cancer by either promoting cell survival or facilitating cell death. In glioblastoma (GB), autophagy has been implicated in resistance to the chemotherapeutic agent temozolomide (TMZ). This study presents a novel method to accurately measure autophagy flux in TMZ-resistant glioblastoma cells, combining advanced imaging techniques with biochemical assays. By quantifying key autophagy markers such as LC3-II and SQSTM1, our approach provides detailed insights into the dynamic processes of autophagosome formation and clearance under therapeutic stress. This method advances our understanding of autophagy in GB chemoresistance and has significant implications for the development of autophagy-targeted therapies. The ability to monitor and manipulate autophagy flux in real time offers a promising avenue for monitoring and understanding TMZ resistance and improving patient outcomes in glioblastoma treatment., (© 2024. Springer Science+Business Media, LLC.)

Glioma is the most common malignant tumor in the central nervous system and has a high mortality rate. Temozolomide (TMZ) is a widely used chemotherapeutic drug for glioma. NDC80 kinetochore complex (NUF2) is suggested to play a regulatory role in different cancers, but its specific function and mechanism in glioblastoma TMZ resistance remain unknown. NUF2, assessed by reverse transcription quantitative polymerase chain reaction (RT‐qPCR), was highly expressed in glioma cell lines. TMZ was used to treat cells to establish a TMZ‐resistant cell line. The potential functions of NUF2 in glioma were assessed using cell counting kit‐8 (CCK‐8) assays, colony formation assays, 5‐Ethynyl‐2'‐deoxyuridine (EdU) assays, flow cytometry, Western blotting, and a tumor xenograft model. The results showed that NUF2 knockdown attenuated malignant phenotypes of TMZ‐resistant cells and prevented tumor growth. Mechanistically, as luciferase reporter assays and chromatin immunoprecipitation (ChIP) as showed, Fox transcription factor M1 (FOXM1) had binding sites on the NUF2 promoter. Rescue assays demonstrated that FOXM1 upregulation counteracted the inhibitory effects of NUF2 depletion on the malignancies of TMZ‐resistant cells. This study demonstrates that FOXM1‐activated NUF2 promotes TMZ to human glioma cells by regulating proliferation, apoptosis, and autophagy. [ABSTRACT FROM AUTHOR]

This study plans to investigate whether miR-214-3p could bind CPLX2 to regulate temozolomide (TMZ) resistance in glioma. The differential expression of miR-214-3p and CPLX2 was determined by qRT-PCR and Western blotting in TMZ-resistant glioma tissues. Then, TMZ-resistant glioma cells (U87/TMZ and U251/TMZ) were established and transfected with miR-214-3p mimic, miR-214-3p inhibitor, pcDNA3.1-CPLX2 or pcDNA3.1-CPLX2 plus miR-214-3p mimic to evaluate the impact of miR-214-3p and CPLX2 on the proliferation, apoptosis and TMZ resistance in U87/TMZ and U251/TMZ cells. The binding relationship between miR-214-3p and CPLX2 was reported by dual-luciferase reporter assay. Higher miR-214-3p and lower CPLX2 expression levels were revealed in TMZ-sensitive glioma tissues. The alterations in miR-214-3p and CPLX2 expression were more significant in TMZ-resistant tissues compared with TMZ-sensitive tissues. In cellular experiments, TMZ-resistant cells expressed higher miR-214-3p expression and lower CPLX2 expression than TMZ-sensitive cells. Transfection of miR-214-3p mimic elevated the proliferation and half maximal inhibitory concentration (IC50) and decreased the apoptosis in U87/TMZ and U251/TMZ cells. Introduction of miR-214-3p inhibitor or pcDNA3.1-CPLX2 reduced the proliferation and IC50 value and prompted the apoptosis in TMZ-resistant glioma cells. The effects of pcDNA3.1-CPLX2 on inhibiting the proliferation and IC50 value and enhancing the apoptosis in TMZ-resistant glioma cells were hindered by the transfection of miR-214-3p mimic. In addition, CPLX2 was a target gene of miR-214-3p. Downregulation of miR-214-3p inhibits TMZ resistance in glioma by promoting CPLX2. [ABSTRACT FROM AUTHOR]

Temozolomide (TMZ) resistance is an important cause of clinical treatment failure and poor prognosis in gliomas. Increasing evidence indicates that cancer-derived exosomes contribute to chemoresistance; however, the specific contribution of glioma-derived exosomes remains unclear. The aim of this study was to explore the role and underlying mechanisms of exosomal macrophage migration inhibitory factor (MIF) on TMZ resistance in gliomas. We first demonstrated that MIF was upregulated in the exosomes of TMZ-resistant cells, engendering the transfer of TMZ resistance to sensitive cells. Our results indicated that exosomal MIF conferred TMZ resistance to sensitive cells through the enhancement of cell proliferation and the repression of cell apoptosis upon TMZ exposure. MIF knockdown enhanced TMZ sensitivity in resistant glioma cells by upregulating Metalloproteinase Inhibitor 3 (TIMP3) and subsequently suppressing the PI3K/AKT signaling pathway. Additionally, exosomal MIF promoted tumor growth and TMZ resistance of glioma cells in vivo, while IOS-1 (MIF inhibitor) promotes glioma TMZ sensitive in vivo. Taken together, our study demonstrated that exosome-mediated transfer of MIF enhanced TMZ resistance in glioma through downregulating TIMP3 and further activating the PI3K/AKT signaling pathway, highlighting a prognostic biomarker and promising therapeutic target for TMZ treatment in gliomas.

Abstract Background Glioblastoma multiforme (GBM) is one of the most daunting issues to modern therapeutics, with a higher mortality rate post-diagnosis. Temozolomide (TMZ) is the only available treatment; however, the frequent resistance leaves the oncologists at a dead end. Therefore, new approaches to circumvent the GBM are highly desired. We have employed TiO2 nanosticks loaded with TMZ as nanomedicine for TMZ-resistant GBM resection in this contribution. Results The ultrasonication triple-action effect could greatly facilitate tumor ablation by enhancing the TiO2 nanosticks traversing across BBB, releasing the TMZ payload from TiO2 nanosticks and reactive oxygen species (ROS) generation from TiO2 nanosticks within the GBM milieu. The tumor ablation was confirmed by MTT and Annexin(v)-PI assays, apoptotic proteins expression via western blot and ROS level detection in vitro, whereas tumor volume, weight, survival rate, and relative photon flux in the xenograft and orthoptic TMZ-resistant GBM murine models as in vivo. Conclusion We found this nanomedicine-based ultrasound modality highly efficient in GBM treatment and is of future clinical application value due to the employment of already FDA-approved techniques and nanomedicine.

Abstract Glioblastoma is the most common primary malignant brain tumor that is usually considered fatal even with treatment. This is often a result for tumor to develop resistance. Regarding the standard chemotherapy, the alkylating agent temozolomide is effective in disease control but the recurrence will still occur eventually. The mechanism of the resistance is various, and differs in terms of innate or acquired. To date, aberrations in O6-methylguanine-DNA methyltransferase are the clear factor that determines drug susceptibility. Alterations of the other DNA damage repair genes such as DNA mismatch repair genes are also known to affect the drug effect. Together these genes have roles in the innate resistance, but are not sufficient for explaining the mechanism leading to acquired resistance. Recent identification of specific cellular subsets with features of stem-like cells may have role in this process. The glioma stem-like cells are known for its superior ability in withstanding the drug-induced cytotoxicity, and giving the chance to repopulate the tumor. The mechanism is complicated to administrate cellular protection, such as the enhancing ability against reactive oxygen species and altering energy metabolism, the important steps to survive. In this review, we discuss the possible mechanism for these specific cellular subsets to evade cancer treatment, and the possible impact to the following treatment courses. In addition, we also discuss the possibility that can overcome this obstacle.

Abstract Background Glioblastoma is the most common primary brain tumor and remains uniformly fatal, highlighting the dire need for developing effective therapeutics. Significant intra- and inter-tumor heterogeneity and inadequate delivery of therapeutics across blood–brain barrier continue to be significant impediments towards developing therapies which can significantly enhance survival. We hypothesize that microRNAs have the potential to serve as effective therapeutics for glioblastoma as they modulate the activity of multiple signaling pathways, and hence can counteract heterogeneity if successfully delivered. Methods Using a computational approach, we identified microRNA-34a as a microRNA that maximally reduces the activation status of the three core signaling networks (the receptor tyrosine kinase, p53 and Rb networks) that have been found to be deregulated in most glioblastoma tumors. Glioblastoma cultures were transfected with microRNA-34a or control microRNA to assess biological function and therapeutic potential in vitro. Nanocells were derived from genetically modified bacteria and loaded with microRNA-34a for intravenous administration to orthotopic patient-derived glioblastoma xenografts in mice. Results Overexpression of microRNA-34a strongly reduced the activation status of the three core signaling networks. microRNA-34a transfection also inhibited the survival of multiple established glioblastoma cell lines, as well as primary patient-derived xenograft cultures representing the proneural, mesenchymal and classical subtypes. Transfection of microRNA-34a enhanced temozolomide (TMZ) response in in vitro cultures of glioblastoma cells with primary TMZ sensitivity, primary TMZ resistance and acquired TMZ resistance. Mechanistically, microRNA-34a downregulated multiple therapeutic resistance genes which are associated with worse survival in glioblastoma patients and are enriched in specific tumor spatial compartments. Importantly, intravenous administration of nanocells carrying miR-34a and targeted to epidermal growth factor receptor (EGFR) strongly enhanced TMZ sensitivity in an orthotopic patient-derived xenograft mouse model of glioblastoma. Conclusions Targeted bacterially-derived nanocells are an effective vehicle for the delivery of microRNA-34a to glioblastoma tumors. microRNA-34a inhibits survival and strongly sensitizes a wide range of glioblastoma cell cultures to TMZ, suggesting that combination therapy of TMZ with microRNA-34a loaded nanocells may serve as a novel therapeutic approach for the treatment of glioblastoma tumors.

Ferroptosis-related genes (FRGs) have been identified as potential targets involved in oncogenesis and cancer therapeutic response. Nevertheless, the specific roles and underlying mechanisms of FRGs in GBM and temozolomide (TMZ) resistance remain unclear. Through comprehensive bioinformatics, we found that ferroptosis-related Fanconi anemia complementation group D2 (FANCD2) was significantly up-regulated in GBM tissues, and the high expression level of FANCD2 was related to the poor prognosis in primary and recurrent GBM patients. Furthermore, FANCD2 could promote TMZ resistance by attenuating ferroptosis in GBM cells. Knockdown of FANCD2 could increase reactive oxygen species (ROS) levels and inhibit cell survival. The two characteristics were associated with ferroptosis in TMZ-resistant GBM cells T98G-R and U118-R. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that aberrantly expressed FANCD2 was potentially linked with several cancer-associated signaling pathways, including chromosome segregation, DNA replication, and cell cycle transition. In addition, we demonstrated that FANCD2 expression was positively correlated with several tumor-infiltrating lymphocytes (TILs) and multiple immune-associated signatures in GBM. Therefore, up-regulated FANCD2 could protect GBM cells from ferroptosis and promote TMZ resistance. FANCD2 may be a novel therapeutic target in GBM. [ABSTRACT FROM AUTHOR]

Glioblastoma (GBM) is a highly fatal and recurrent brain cancer without a complete prevailing remedy. Although the synthetic nanotechnology-based approaches exhibit excellent therapeutic potential, the associated cytotoxic effects and organ clearance failure rest major obstacles from bench to clinics. Here, we explored allogeneic bone marrow mesenchymal stem cells isolated exosomes (BMSC Exo) decorated with heme oxygenase-1 (HMOX1) specific short peptide (HSSP) as temozolomide (TMZ) and small interfering RNA (siRNA) nanocarrier for TMZ resistant glioblastoma therapy. The BMSC Exo had excellent TMZ and siRNA loading ability and could traverse the blood-brain barrier (BBB) by leveraging its intrinsic brain accumulation property. Notably, with HSSP decoration, the TMZ or siRNA encapsulated BMSC Exo exhibited excellent TMZ resistant GBM targeting ability both in vitro and in vivo due to the overexpression of HMOX1 in TMZ resistant GBM cells. Further, the HSSP decorated BMSC Exo delivered the STAT3 targeted siRNA to the TMZ resistant glioma and restore the TMZ sensitivity, consequently achieved the synergistically drug resistant GBM treatment with TMZ. Our results showed this biomimetic nanoplatform can serve as a flexible, robust and inert system for GBM treatment, especially emphasizing the drug resistant challenge • Surface engineered with HMOX1 targeting peptide empowered the exosome specifically navigating to temozolomide resistant GBM (GBM-TR). • A biocompatible exosomal nano-delivery system for drug and siRNA has been developed and the drug delivery potential was evaluated towards translation medicine. • The GBM-TR targeting exosomal delivery system loaded with STAT3 targeted siRNA achieved the tumour proliferation inhibition, decreased the MGMT expression in GBM-TR and achieved synergistic therapy with TMZ loaded exosomes in vivo. [ABSTRACT FROM AUTHOR]

Simple Summary: Temozolomide (TMZ) is the first-line drug for chemotherapy of GBM, the most aggressive and incurable brain tumor. Acquired chemoresistance is a hallmark that causes the poor prognosis of GBM. Therefore, understanding the underlying mechanisms by using a proper model becomes emergent. Previous models usually take weeks/months and are often not fully representative of characteristics of TMZ resistance. We established an acute acquired TMZ resistance model using GBM cell lines with different genomic backgrounds. In response to TMZ, the resistant cells showed less susceptibility and sustained regrowth, high clonogenicity, reduced DNA damage accompanied by attenuated MMR, shortened G2/M arrest, uncontrolled DNA replication, and evasion of apoptosis. Moreover, these TMZ resistant cells presented stem cell properties that are critical for chemoresistance. Thus, our model recapitulates all key features of TMZ resistance and is believed to be a promising model to study the underlying mechanisms and define therapeutics for GBM in the future. Temozolomide (TMZ) is the first line of standard therapy in glioblastoma (GBM). However, relapse occurs due to TMZ resistance. We attempted to establish an acquired TMZ resistance model that recapitulates the TMZ resistance phenotype and the relevant gene signature. Two GBM cell lines received two cycles of TMZ (150 µM) treatment for 72 h each. Regrown cells (RG2) were defined as TMZ resistant cells. MTT assay revealed significantly less susceptibility and sustained growth of RG2 compared with parental cells after TMZ challenge. TMZ-induced DNA damage significantly decreased in 53BP1-foci reporter transduced-RG2 cells compared with parental cells, associated with downregulation of MSH2 and MSH6. Flow cytometry revealed reduced G2/M arrest, increased EdU incorporation and suppressed apoptosis in RG2 cells after TMZ treatment. Colony formation and neurosphere assay demonstrated enhanced clonogenicity and neurosphere formation capacity in RG2 cells, accompanied by upregulation of stem markers. Collectively, we established an acute TMZ resistance model that recapitulated key features of TMZ resistance involving impaired mismatch repair, redistribution of cell cycle phases, increased DNA replication, reduced apoptosis and enhanced self-renewal. Therefore, this model may serve as a promising research tool for studying mechanisms of TMZ resistance and for defining therapeutic approaches to GBM in the future. [ABSTRACT FROM AUTHOR]

Many studies have found that the dysregulation of long noncoding RNA (lncRNA) contributed to cancer initiation, progression, and recurrence via multiple signaling pathways. However, the underlying mechanisms of lncRNA in temozolomide (TMZ)-resistant gliomas were not well understood, hindering the improvement of TMZ-based therapies. The present study demonstrated that the lncRNA KCNQ1OT1 increased in TMZ-resistant glioma cells compared to the TMZ-sensitive cells. The introduction of KCNQ1OT1 promoted cell viability, clonogenicity, and rhodamine 123 efflux while hampering TMZ-induced apoptosis. Moreover, KCNQ1OT1 directly sponged miR-761, which decreased in TMZ-resistant sublines. The overexpression of miR-761 attenuated cell viability and clonogenicity, while triggering apoptosis and rhodamine 123 accumulation post-TMZ exposure, leading to a response to TMZ. The interaction between miR-761 and 3′-untranslated region of PIM1 attenuated PIM1-mediated signaling cascades. Furthermore, the knockdown of KCNQ1OT1 augmented the TMZ-induced tumor regression in TMZ-resistant U251 mouse models. Briefly, the present study evaluated that KCNQ1OT1 conferred TMZ resistance by releasing PIM1 expression from miR-761, resulting in the upregulation of PIM-mediated MDR1, c-Myc, and Survivin. The present findings demonstrated that the interplay of KCNQ1OT1: miR-761: PIM1 regulated chemoresistance in gliomas and provided a promising therapeutic target for TMZ-resistant glioma patients. [ABSTRACT FROM AUTHOR]

Ferroptosis-related genes (FRGs) have been identified as potential targets involved in oncogenesis and cancer therapeutic response. Nevertheless, the specific roles and underlying mechanisms of FRGs in GBM and temozolomide (TMZ) resistance remain unclear. Through comprehensive bioinformatics, we found that ferroptosis-related Fanconi anemia complementation group D2 (FANCD2) was significantly up-regulated in GBM tissues, and the high expression level of FANCD2 was related to the poor prognosis in primary and recurrent GBM patients. Furthermore, FANCD2 could promote TMZ resistance by attenuating ferroptosis in GBM cells. Knockdown of FANCD2 could increase reactive oxygen species (ROS) levels and inhibit cell survival. The two characteristics were associated with ferroptosis in TMZ-resistant GBM cells T98G-R and U118-R. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that aberrantly expressed FANCD2 was potentially linked with several cancer-associated signaling pathways, including chromosome segregation, DNA replication, and cell cycle transition. In addition, we demonstrated that FANCD2 expression was positively correlated with several tumor-infiltrating lymphocytes (TILs) and multiple immune-associated signatures in GBM. Therefore, up-regulated FANCD2 could protect GBM cells from ferroptosis and promote TMZ resistance. FANCD2 may be a novel therapeutic target in GBM.

Background: Temozolomide (TMZ) is used in the treatment of glioblastoma (GBM). However, the primary obstacle remains the emergence of TMZ chemotherapy resistance. NONO and SFPQ are multifunctional nuclear proteins involved in genome stability and gene regulation. However, the specific role of NONO and SFPQ in TMZ resistance of GBM remains to be explored., Methods: RIP-chip and RNA microarray of TMZ-resistant and parental cells were performed for the gain of HSD52. The effects of HSD52 on TMZ resistance were investigated through in vitro assays, intracranial xenograft and GBM organoid models. The underlying mechanisms were explored by DNA methylation chip, RIP, RNA pulldown assays, among others. GBM clinical samples were rolled in to investigate the clinical significance of HSD52., Results: We identified a novel non-coding RNA, HSD52, that was highly expressed in TMZ-resistant GBM and facilitated the interaction between NONO and SFPQ. H3 ubiquitination attenuation and reduced DNMT1 recruitment increased HSD52 transcription via DNA hypo-methylation. HSD52 formed an RNA duplex with UFL1 mRNA, thereby promoting NONO/SFPQ complex binding to UFL1 mRNA and enhancing its stability, and then contributed to TMZ resistance through activating ATM signaling pathway. In vivo xenograft and GBM organoid models showed significant repression in tumor growth after HSD52 knockout with TMZ treatment. In GBM clinical samples, HSD52 was responsible for the malignant progression and TMZ resistance., Conclusions: Our results revealed that HSD52 could serve as a promising therapeutic target to overcome TMZ resistance, improving the clinical efficacy of TMZ chemotherapy in GBM., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Glioblastoma (GBM) is the most prevalent and deadly primary brain tumor. The current treatment for GBM includes adjuvant chemotherapy with temozolomide (TMZ), radiation therapy, and surgical tumor excision. There is still an issue because 50% of patients with GBM who get TMZ have low survival rates due to TMZ resistance. The activation of several DNA repair mechanisms, such as Base Excision Repair (BER), DNA Mismatch Repair (MMR), and O-6- Methylguanine-DNA Methyltransferase (MGMT), is the main mechanism via which TMZ resistance develops. The zinc-finger DNA-binding enzyme poly (ADP-ribose) polymerase-1 (PARP1), which is activated by binding to DNA breaks, affects the activation of the MGMT, BER, and MMR pathway deficiency, which results in TMZ resistance in GBM. PARP inhibitors have been studied recently as sensitizing medications to increase TMZ potency. The first member of the PARP inhibitor family to be identified was Olaparib. It inhibits PARP1 and PARP2, which causes apoptosis in cancer cells and DNA strand break. Olaparib is currently investigated as a radio- and/or chemo-sensitizer in addition to being used as a single agent because it may increase the cytotoxic effects of other treatments. This review addresses Olaparib and its significance in treating TMZ resistance in GBM., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Context Temozolomide (TMZ) is endorsed as the treatment of choice in aggressive or malignant pituitary adenomas. Objective Herein we describe a case of an aggressive prolactinoma that was resistant to TMZ. We performed a literature review of similar nonresponsive, aggressive prolactinomas. Methods A 40-year-old woman presented with a giant prolactinoma that required cabergoline, transsphenoidal surgery, and radiotherapy to achieve near-normal prolactin and apparently no residual tumor. A year later, she presented with multiple cranial nerve involvement due to a recurrent tumor extending to the infratemporal fossa. She underwent transfrontal surgery, second radiotherapy, and was started on TMZ. Despite 8 cycles of temozolomide (200 mg/m2, 5/28-day cycle), she had progressive disease and ultimately succumbed to the disease. PubMed/MEDLINE, Google Scholar, and prior review articles were searched for manuscripts about patients with aggressive prolactinomas who had been treated with TMZ. Data on demography, duration of therapy, and management outcomes were analyzed in those with progressive disease. Results We identified 94 cases of patients with aggressive/malignant prolactinomas in the literature who had received TMZ. Progressive disease despite TMZ was present in 36 cases (38%). There was a male preponderance (65%) among these and 40% had aggressive prolactinomas, whereas the rest had carcinomas. Patients received a median of 8 cycles (interquartile range, 3.5-11.5) of TMZ. O6‐methylguanine‐DNA‐methyltransferase (MGMT) immunostaining was negative in 35%. Overall mortality at the time of publication was 40%, at a duration varying from 2 to 20 years from diagnosis. Conclusion TMZ resistance in aggressive/malignant prolactinomas is challenging. Progressive disease on optimal TMZ treatment entails the use of newer agents. [ABSTRACT FROM AUTHOR]

Glioma is the most common malignancy of the central nervous system. Although advances in surgical resection, adjuvant radiotherapy, and chemotherapy have been achieved in the last decades, the prognosis of gliomas is still dismal. COL5A1 is one of the collagen members with minor content but prominent functions. The present study examined the biological functions, prognostic value, and gene-associated tumor-infiltrating immune cells of COL5A1 through experiments and bioinformatics analysis. We found that the overexpression of COL5A1 was positively correlated with the increasing tumor malignancies and indicated poor prognosis in gliomas. Moreover, downregulation of COL5A1 could inhibit proliferation and migration of glioma cells and enhance their temozolomide sensitivities in vitro. Further bioinformatic analysis revealed that COL5A1 and its co-expressed genes participated in a number of pathways and biological processes involved in glioma progression. Finally, we evaluated the tumor-infiltrating immune cells of gliomas depending on COL5A1 and found that the percentages of the dendritic cells, which were known as the central mediator of tumor microenvironment in gliomas, were positively associated with the expression levels of COL5A1. Taken together, COL5A1 is an important biomarker and potential therapeutic target of gliomas.

Glioma is the most common malignancy of the central nervous system. Although advances in surgical resection, adjuvant radiotherapy, and chemotherapy have been achieved in the last decades, the prognosis of gliomas is still dismal. COL5A1 is one of the collagen members with minor content but prominent functions. The present study examined the biological functions, prognostic value, and gene-associated tumor-infiltrating immune cells of COL5A1 through experiments and bioinformatics analysis. We found that the overexpression of COL5A1 was positively correlated with the increasing tumor malignancies and indicated poor prognosis in gliomas. Moreover, downregulation of COL5A1 could inhibit proliferation and migration of glioma cells and enhance their temozolomide sensitivities in vitro. Further bioinformatic analysis revealed that COL5A1 and its co-expressed genes participated in a number of pathways and biological processes involved in glioma progression. Finally, we evaluated the tumor-infiltrating immune cells of gliomas depending on COL5A1 and found that the percentages of the dendritic cells, which were known as the central mediator of tumor microenvironment in gliomas, were positively associated with the expression levels of COL5A1. Taken together, COL5A1 is an important biomarker and potential therapeutic target of gliomas. [ABSTRACT FROM AUTHOR]

Glioblastomas (GBM) often acquire resistance against temozolomide (TMZ) after continuous treatment and recur as TMZ-resistant GBM (TMZ-R-GBM). Lomustine (CCNU) and nimustine (ACNU), which were previously used as standard therapeutic agents against GBM before TMZ, have occasionally been used for the salvage therapy of TMZ-R-GBM; however, their efficacy has not yet been thoroughly examined. Therefore, we investigated the antitumor effects of CCNU and ACNU against TMZ-R-GBM. As a model of TMZ-R-GBM, TMZ resistant clones of human GBM cell lines (U87, U251MG, and U343MG) were established (TMZ-R-cells) by the culture of each GBM cells under continuous TMZ treatment, and the antitumor effects of TMZ, CCNU, or ACNU against these cells were analyzed in vitro and in vivo. As a result, although growth arrest and apoptosis were triggered in all TMZ-R-cells after the administration of each drug, the antitumor effects of TMZ against TMZ-R-cells were significantly reduced compared to those of parental cells, whereas CCNU and ACNU demonstrated efficient antitumor effects on TMZ-R-cells as well as parental cells. It was also demonstrated that TMZ resistance of TMZ-R-cells was regulated at the initiation of DNA damage response. Furthermore, survival in mice was significantly prolonged by systemic treatment with CCNU or ACNU but not TMZ after implantation of TMZ-R-cells. These findings suggest that CCNU or ACNU may serve as a therapeutic agent in salvage treatment against TMZ-R-GBM. [ABSTRACT FROM AUTHOR]

Glioblastoma (GBM) presents a daunting challenge due to its resistance to temozolomide (TMZ), a hurdle exacerbated by the proneural-to-mesenchymal transition (PMT) from a proneural (PN) to a mesenchymal (MES) phenotype. TAGLN2 is prominently expressed in GBM, particularly in the MES subtype compared to low-grade glioma (LGG) and the PN subtype. Our research reveals TAGLN2's involvement in PMT and TMZ resistance through a series of in vitro and in vivo experiments. TAGLN2 knockdown can restrain proliferation and invasion, trigger DNA damage and apoptosis, and heighten TMZ sensitivity in GBM cells. Conversely, elevating TAGLN2 levels amplifies resistance to TMZ in cellular and intracranial xenograft mouse models. We demonstrate the interaction relationship between TAGLN2 and ERK1/2 through co-immunoprecipitation (Co-IP) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) spectrometry analysis. Knockdown of TAGLN2 results in a decrease in the expression of p-ERK1/2, whereas overexpression of TAGLN2 leads to an increase in p-ERK1/2 expression within the nucleus. Subsequently, the regulatory role of TAGLN2 in the expression and control of MGMT has been demonstrated. Finally, the regulation of TAGLN2 by NF-κB has been validated through chromatin immunoprecipitation and ChIP-PCR assays. In conclusion, our results confirm that TAGLN2 exerts its biological functions by interacting with the ERK/MGMT axis and being regulated by NF-κB, thereby facilitating the acquisition of promoting PMT and increased resistance to TMZ therapy in glioblastoma. These results provide valuable insights for the advancement of targeted therapeutic approaches to overcome TMZ resistance in clinical treatments. • TAGLN2 overexpressed in GBMs is associated with poor prognosis. • TAGLN2 advances proneural-mesenchymal transition (PMT). • TAGLN2 promotes GBM resistance to TMZ. • TAGLN2 regulated by NF-κB drives TMZ resistance. • TAGLN2 regulates ERK/MGMT to form TMZ resistance. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is an aggressive brain cancer that occurs more frequently than other brain tumors. The present study aimed to reveal a novel mechanism of temozolomide resistance in GBM using bioinformatics and wet lab analyses, including meta-Z analysis, Kaplan-Meier survival analysis, protein-protein interaction (PPI) network establishment, cluster analysis of co-expressed gene networks, and hierarchical clustering of upregulated and downregulated genes. Next-generation sequencing and quantitative PCR analyses revealed downregulated [tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 1 (TIE1), calcium voltage-gated channel auxiliary subunit α2Δ1 (CACNA2D1), calpain 6 (CAPN6) and a disintegrin and metalloproteinase with thrombospondin motifs 6 (ADAMTS6)] and upregulated [serum amyloid (SA)A1, SAA2, growth differentiation factor 15 (GDF15) and ubiquitin specific peptidase 26 (USP26)] genes. Different statistical models were developed for these genes using the Z-score for P-value conversion, and Kaplan-Meier plots were constructed using several patient cohorts with brain tumors. The highest number of nodes was observed in the PPI network was for ADAMTS6 and TIE1. The PPI network model for all genes contained 35 nodes and 241 edges. Immunohistochemical staining was performed using isocitrate dehydrogenase (IDH)-wild-type or IDH-mutant GBM samples from patients and a significant upregulation of TIE1 (P<0.001) and CAPN6 (P<0.05) protein expression was demonstrated in IDH-mutant GBM in comparison with IDH-wild-type GBM. Structural analysis revealed an IDH-mutant model demonstrating the mutant residues (R132, R140 and R172). The findings of the present study will help the future development of novel biomarkers and therapeutics for brain tumors. [ABSTRACT FROM AUTHOR]

Background/Aim. CHI3L1 (chitinase 3-like protein 1) is a secretory glycoprotein highly upregulated in glioblastoma (GBM) and is recognized as a molecular marker of tumor mesenchymal subtype. However the gene’s short transcriptional isoform (CHI3L1Δ8) is poorly studied regarding its biological role in GBM. O6-methylguanineDNA methyltransferase (MGMT) promoter methylation is considered a prognostic marker for temozolomide (TMZ) resistance in GBM patients, though some conflicting data exist. We aimed to analyze methylation of the MGMT promoter and CHI3L1/CHI3L1Δ8 expression in cells of the panel of U-251 MG (U251) glioblastoma cell lines, sensitive and resistant to TMZ. Methods. Transgenic cell lines U251-GFP, U251-CHI3L1 and U251-CHI3L2 have been generated previously by lentiviral transduction. TMZresistant derivates of transgenic and parental U251 (tmzU251, tmzU251-GFP, tmzU251-CHI3L1 and tmzU251-CHI3L2) have been obtained by cells selection with augmenting concentrations of TMZ. Methyl-specific (MS) PCR and MS-sequencing were used for MGMT promoter methylation determination. qPCR with isoformspecific primers was carried out for the analysis of CHI3L1/ CHI3L1Δ8 expression. Results. Both MS-PCR and MSsequencing demonstrated an increase in MGMT promoter methylation in all the transgenic and the TMZ-resistant cell lines comparing to intact U251. MS-sequencing showed the most significant increase of methylation level in the tmzU251 cell line comparing to the original U251 (p < 0.001 by Kolmogorov-Smirnov test). TMZ also leads to an increase in methylation level of the MGMT promoter region in all the transgenic cell lines compared to the original U251 (p < 0.01). Transgenic cell lines except the U251-CHI3L1 demonstrated reduced expression of both CHI3L1 isoforms. On the contrary, TMZ long-term treatment leads to an increase of both CHI3L1 isoforms expression. Surprisingly the most significant rising was revealed in tmzU251-CHI3L2 with the isoforms ratio retention contrary to tmzU251 and tmzU251-GFP cells. Both these sublines showed bias towards CHI3L1 full isoform expression whereas tmzU251-CHI3L1 possessed balance shifting in favor of short CHI3L1Δ8 isoform. Conclusions. The obtained data indicate involvement of cellular mechanisms other than the reparative activity of MGMT in the evolution and maintenance of the TMZ-resistant phenotype. This is consistent with other studies on the decreasing of the prognostic role of the MGMT promoter methylation status for the assessment of therapeutic effect of TMZ in the treatment of glioblastoma. Balance alteration between the two CHI3L1 transcripts could be a part of the glioblastoma chemoresistance mechanism in response to TMZ treatment. [ABSTRACT FROM AUTHOR]

• Muscone caused TMZ-resistant glioblastoma cells to undergo anoikis, G2/M phase arrest, and DNA damage. • Muscone decreased anoikis resistance in U251-TR cells by downregulating TOP2A expression. • Muscone restored the anoikis sensitivity of TMZ-resistant GBM cells by reducing TOP2A expression via blocking the EGFR/Integrin β1/FAK signaling pathway. Temozolomide (TMZ) resistance is the main obstacle faced by glioblastoma multiforme (GBM) treatment. Muscone, one of the primary active pharmacological ingredients of Shexiang (Moschus), can cross the blood-brain barrier (BBB) and is being investigated as an antineoplastic medication. However, muscone treatment for GBM has received little research, and its possible mechanisms are still unclear. This study aims to evaluate the effect and the potential molecular mechanism of muscone on TMZ-resistant GBM cells. The differentially expressed genes (DEGs) between TMZ-resistant GBM cells and TMZ-sensitive GBM cells were screened using GEO2R. By progressively raising the TMZ concentration, a relatively stable TMZ-resistant human GBM cell line was established. The drug-resistance traits of U251-TR cells were assessed via the CCK-8 assay and Western Blot analysis of MGMT and TOP2A expression. Cell viability, cell proliferation, cell migration ability, and drug synergism were detected by the CCK-8 assay, colony formation assay, wound healing assay, and drug interaction relationship test, respectively. Anoikis was quantified by Calcein-AM/EthD-1 staining, MTT assay, and flow cytometry. Measurements of cell cycle arrest, apoptosis, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) were performed using cell cycle staining, Annexin V-FITC/PI labeling, JC-1 assay, and ROS assay, respectively. DNA damage was measured by TUNEL assay, alkaline comet assay, and γ-H2AX foci assay. GEPIA was used to investigate the link between the anoikis marker (FAK)/drug resistance gene and critical proteins in the EGFR/Integrin β1 signaling pathway. Molecular docking was used to anticipate the probable targets of muscone. The intracellular co-localization and expression of EGFR and FAK were shown using immunofluorescence. The U251-TR cell line stably overexpressing EGFR was constructed using lentiviral transduction to assess the involvement of EGFR-related signaling in anoikis resistance. Western Blot was employed to detect the expression of migration-related proteins, cyclins, anoikis-related proteins, DNA damage/repair-related proteins, and associated pathway proteins. DEGs analysis identified 97 deregulated chemotherapy-resistant genes and 3779 upregulated genes in TMZ-resistant GBM cells. Subsequent experiments verified TMZ resistance and the hyper-expression of DNA repair-related genes (TOP2A and MGMT) in continuously low-dose TMZ-induced U251-TR cells. Muscone exhibited dose-dependent inhibition of U251-TR cell migration and proliferation, and its co-administration with TMZ showed the potential for enhanced therapeutic efficacy. By downregulating FAK, muscone reduced anoikis resistance in anchorage-independent U251-TR cells. It also caused cell cycle arrest in the G2/M phase by upregulating p21 and downregulating CDK1, CDK2, and Cyclin E1. Muscone-induced anoikis was accompanied by mitochondrial membrane potential collapse, ROS production, an increase in the BAX/Bcl-2 ratio, as well as elevated levels of Cytochrome c (Cyt c), cleaved caspase-9, and cleaved caspase-3. These findings indicated that muscone might trigger mitochondrial-dependent anoikis via ROS generation. Moreover, significant DNA damage, DNA double-strand breaks (DSBs), the formation of γ-H2AX foci, and a reduction in TOP2A expression are also associated with muscone-induced anoikis. Overexpression of EGFR in U251-TR cells boosted the expression of Integrin β1, FAK, β-Catenin, and TOP2A, whereas muscone suppressed the expression levels of EGFR, Integrin β1, β-Catenin, FAK, and TOP2A. Muscone may influence the expression of the key DNA repair enzyme, TOP2A, by suppressing the EGFR/Integrin β1/FAK pathway. We first demonstrated that muscone suppressed TOP2A expression through the EGFR/Integrin β1/FAK pathway, hence restoring anoikis sensitivity in TMZ-resistant GBM cells. These data suggest that muscone may be a promising co-therapeutic agent for enhancing GBM treatment, particularly in cases of TMZ-resistant GBM with elevated TOP2A expression. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Background Accumulating evidence demonstrates the oncogenic roles of lncRNA (long non-coding RNA) molecules in a wide variety of cancer types including glioma. Equally important, However, tumorigenic functions of lncRNA in glioma remain largely unclear. A recent study suggested lncRNA SNHG15 played a role for regulating angiogenesis in glioma but its role in the tumor microenvironment (TME) was not investigated. Methods First, we showed that SNHG15 was upregulated in GBM cells and associated with a poor prognosis for the patients of GBM using public databases. Next, we collected temozolomide sensitive (TMZ-S) and resistant (TMZ-R) clinical samples and demonstrated that co-culturing TMZ-R cells with HMC3 (microglial) cells promoted M2-polarization of HMC3 and the secretion of pro-GBM cytokines TGF-β and IL-6. Results Comparative qPCR analysis of TMZ-S and TMZ-R cells showed that a significantly higher level of SNHG15, coincidental with a higher level of Sox2, β-catenin, EGFR, and CDK6 in TMZ-R cells. Subsequently, using bioinformatics tool, a potential mechanistic route for SNHG15 to promote GBM tumorigenesis was by inhibiting tumor suppressor, miR-627-5p which leads to activation of CDK6. Gene-silencing technique was employed to demonstrate that suppression of SNHG15 indeed led to the suppression of GBM tumorigenesis, accompanied by an increase miR-627-5p and decreased its two oncogenic targets, CDK6 and SOX-2. In addition, SNHG15-silenced TMZ-R cells became significantly sensitive towards TMZ treatment and less capable of promoting M2-phenotype in the HMC3 microglial cells. We then evaluated the potential anti-GBM activity of CDK6 inhibitor, palbociclib, using TMZ-R PDX mouse models. Palbociclib treatment significantly reduced tumorigenesis in TMZ-R/HMC3 bearing mice and SNHG15 and CDK6 expression was significantly reduced while miR-627-5p level was increased. Additionally, palbociclib treatment appeared to overcome TMZ resistance as well as reduced M2 markers in HMC3 cells. Conclusion Together, we provided evidence supporting the usage of CDK6 inhibitor for TMZ-resistant GBM cases. Further investigation is warranted for the consideration of clinical trials. Graphical abstract

Background: Glioblastoma is a malignant and very aggressive brain tumor with a poor prognosis. Despite having chemotherapy concomitant with surgery and/or radiation therapy, the median survival of glioblastoma-affected people is less than 1 year. Temozolomide (TMZ) is a chemotherapeutic used as a first line treatment of glioblastoma. Several studies have reported that resistance to TMZ due to overexpression of O6-methylguanine-DNA methyltransferase (MGMT) is the main reason for treatment failure. Several studies described that pulsed-electromagnetic field (EMF) exposure could induce cell death and influence gene expression. Materials and Methods: In this study the authors assessed the effects of EMF (50 Hz, 70 G) on cytotoxicity, cell migration, gene expression, and protein levels in TMZ-treated T98 and A172 cell lines. Results: In this study, the authors show that treatment with a combination of TMZ and EMF enhanced cell death and decreased the migration potential of T98 and A172 cells. The authors also observed overexpression of the p53 gene and downregulation of cyclin-D1 protein in comparison to controls. In addition, T98 cells expressed the MGMT protein following treatment, while the A172 cells did not express MGMT. Conclusion: Their data indicate that EMF exposure improved the cytotoxicity of TMZ on T98 and A172 cells and could partially affect resistance to TMZ in T98 cells. [ABSTRACT FROM AUTHOR]