BACH1 Promotes Temozolomide Resistance in Glioblastoma through Antagonizing the Function of p53

Circ_0005015 upregulates BACH1 to promote aggressive behaviors in glioblastoma by sponging microRNA-382-5p

To investigate the potential role and molecular mechanism of circ_0005015 in GBM progression. Circ_0005015, microRNA-382-5p (miR-382-5p), and BTB domain and CNC homolog 1 (BACH1) levels were measured by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation was determined by MTT, colony formation, and EdU assays. Cell apoptosis was analyzed using flow cytometry. Cell migration and invasion were assessed using wound healing and transwell assays. Glucose accumulation and lactate levels were examined by the corresponding kit. RNA pull-down and dual-luciferase reporter assays were performed to confirm the interaction between miR-382-5p and circ_0005015 or BACH1. Protein levels of MMP9, PCNA, and BACH1 were examined using western blot assay. Role of circ_0005015 on tumor growth in vivo was analyzed using a xenograft tumor model. Circ_0005015 content was up-regulated in GBM patients and cells, its knockdown restrained GBM cell proliferation, migration, invasion, glycolysis, and triggered apoptosis. Mechanistically, we found that circ_0005015 could directly interact with miR-382-5p and serve as a miRNA sponge to regulate BACH1 expression. In addition, circ_0005015 knockdown might repress tumor growth in vivo. Circ_0005015 boosted GBM progression via binding to miR-382-5p to up-regulate BACH1, which may offer new effective targets for GBM treatment.

Transcription factor BACH1 in cancer: roles, mechanisms, and prospects for targeted therapy

Transcription factor BTB domain and CNC homology 1 (BACH1) belongs to the Cap 'n' Collar and basic region Leucine Zipper (CNC-bZIP) family. BACH1 is widely expressed in mammalian tissues, where it regulates epigenetic modifications, heme homeostasis, and oxidative stress. Additionally, it is involved in immune system development. More importantly, BACH1 is highly expressed in and plays a key role in numerous malignant tumors, affecting cellular metabolism, tumor invasion and metastasis, proliferation, different cell death pathways, drug resistance, and the tumor microenvironment. However, few articles systematically summarized the roles of BACH1 in cancer. This review aims to highlight the research status of BACH1 in malignant tumor behaviors, and summarize its role in immune regulation in cancer. Moreover, this review focuses on the potential of BACH1 as a novel therapeutic target and prognostic biomarker. Notably, the mechanisms underlying the roles of BACH1 in ferroptosis, oxidative stress and tumor microenvironment remain to be explored. BACH1 has a dual impact on cancer, which affects the accuracy and efficiency of targeted drug delivery. Finally, the promising directions of future BACH1 research are prospected. A systematical and clear understanding of BACH1 would undoubtedly take us one step closer to facilitating its translation from basic research into the clinic.

Gene signatures associated with prognosis and chemotherapy resistance in glioblastoma treated with temozolomide

Background: Glioblastoma (GBM) prognosis remains extremely poor despite standard treatment that includes temozolomide (TMZ) chemotherapy. To discover new GBM drug targets and biomarkers, genes signatures associated with survival and TMZ resistance in GBM patients treated with TMZ were identified. Methods: GBM cases in The Cancer Genome Atlas who received TMZ (n = 221) were stratified into subgroups that differed by median overall survival (mOS) using network-based stratification to cluster patients whose somatic mutations affected genes in similar modules of a gene interaction network. Gene signatures formed from differentially mutated genes in the subgroup with the longest mOS were used to confirm their association with survival and TMZ resistance in independent datasets. Somatic mutations in these genes also were assessed for an association with OS in an independent group of 37 GBM cases. Results: Among the four subgroups identified, subgroup four (n = 71 subjects) exhibited the longest mOS at 18.3 months (95% confidence interval: 16.2, 34.1; p = 0.0324). Subsets of the 86 genes that were differentially mutated in this subgroup formed 20-gene and 8-gene signatures that predicted OS in two independent datasets (Spearman's rho of 0.64 and 0.58 between actual and predicted OS; p < 0.001). Patients with mutations in five of the 86 genes had longer OS in a small, independent sample of 37 GBM cases, but this association did not reach statistical significance (p = 0.07). Thirty-one of the 86 genes formed signatures that distinguished TMZ-resistant GBM samples from controls in three independent datasets (area under the curve ≥ 0.75). The prognostic and TMZ-resistance signatures had eight genes in common (ANG, BACH1, CDKN2C, HMGA1, IFI16, PADI4, SDF4, and TP53INP1). The latter three genes have not been associated with GBM previously. Conclusion: PADI4, SDF4, and TP53INP1 are novel therapy and biomarker candidates for GBM. Further investigation of their oncologic functions may provide new insight into GBM treatment resistance mechanisms.

Advances in Glioblastoma Therapy: An Update on Current Approaches

Glioblastoma multiforme (GBM) is a primary malignant brain tumor characterized by a high grade of malignancy and an extremely unfavorable prognosis. The current efficacy of established treatments for GBM is insufficient, necessitating the prompt development of novel therapeutic approaches. The progress made in the fundamental scientific understanding of GBM is swiftly translated into more advanced stages of therapeutic studies. Despite extensive efforts to identify new therapeutic approaches, GBM exhibits a high mortality rate. The current efficacy of treatments for GBM patients is insufficient due to factors such as tumor heterogeneity, the blood-brain barrier, glioma stem cells, drug efflux pumps, and DNA damage repair mechanisms. Considering this, pharmacological cocktail therapy has demonstrated a growing efficacy in addressing these challenges. Towards this, various forms of immunotherapy, including the immune checkpoint blockade, chimeric antigen receptor T (CAR T) cell therapy, oncolytic virotherapy, and vaccine therapy have emerged as potential strategies for enhancing the prognosis of GBM. Current investigations are focused on exploring combination therapies to mitigate undesirable side effects and enhance immune responses against tumors. Furthermore, clinical trials are underway to evaluate the efficacy of several strategies to circumvent the blood-brain barrier (BBB) to achieve targeted delivery in patients suffering from recurrent GBM. In this review, we have described the biological and molecular targets for GBM therapy, pharmacologic therapy status, prominent resistance mechanisms, and new treatment approaches. We also discuss these promising therapeutic approaches to assess prospective innovative therapeutic agents and evaluated the present state of preclinical and clinical studies in GBM treatment. Overall, this review attempts to provide comprehensive information on the current status of GBM therapy.

Modulating MGMT expression through interfering with cell signaling pathways

Guanine O6-alkylating agents are widely used as first-line chemotherapeutic drugs due to their ability to induce cytotoxic DNA damage. However, a major hurdle in their effectiveness is the emergence of chemoresistance, largely attributed to the DNA repair pathway mediated by O6-methylguanine-DNA methyltransferase (MGMT). MGMT plays an important role in removing the alkyl groups from lethal O6-alkylguanine (O6-AlkylG) adducts formed by chemotherapeutic alkylating agents. By doing so, MGMT enables tumor cells to evade apoptosis and develop drug resistance toward DNA alkylating agents. Although covalent inhibitors of MGMT, such as O6-benzylguanine (O6-BG) and O6-(4-bromothenyl)guanine (O6-4-BTG or lomeguatrib), have been explored in clinical settings, their utility is limited due to severe delayed hematological toxicity observed in most patients when combined with alkylating agents. Therefore, there is an urgent need to identify new targets and unravel the underlying molecular mechanisms and to develop alternative therapeutic strategies that can overcome MGMT-mediated tumor resistance. In this context, the regulation of MGMT expression via interfering the specific cell signaling pathways (e.g., Wnt/β-catenin, NF-κB, Hedgehog, PI3K/AKT/mTOR, JAK/STAT) emerges as a promising strategy for overcoming tumor resistance, and ultimately enhancing the efficacy of DNA alkylating agents in chemotherapy.

BCAS3 accelerates glioblastoma tumorigenesis by restraining the P53/GADD45α signaling pathway

As in many other cancers, highly malignant proliferation and disordered cell division play irreplaceable roles in the exceedingly easy recurrence and complex progression of glioblastoma multiforme (GBM); however, mechanistic studies of the numerous regulators involved in this process are still insufficiently thorough. The role of BCAS3 has been studied in other cancers, but its role in GBM is unclear. Here, our goal was to investigate the expression pattern of BCAS3 in GBM and its potential mechanism of action. Using TCGA database and human GBM samples, we found that BCAS3 expression was up-regulated in GBM, and its high expression predicted poor prognosis. To further investigate the relationship between BCAS3 and GBM characteristics, we up-regulated and down-regulated BCAS3 expression in GBM to detect its effect on cell proliferation and cell cycle. At the same time, we established U87 cells stably overexpressing BCAS3 and generated an intracranial xenograft model to investigate the Potential role of BCAS3 in vivo. Finally, based on in vitro cell experiments and in vivo GBM xenograft models, we observed that BCAS3 significantly regulates GBM cell proliferation and cell cycle and that this regulation is associated with p53/GADD45α Signaling pathway. Taken together, our findings suggest that BCAS3 is inextricably linked to the progression of GBM and that targeting BCAS3 may have therapeutic effects in GBM patients.

Unraveling unique and common cell type-specific mechanisms in glioblastoma multiforme

Glioblastoma multiforme persists to be an enigmatic distress in neuro-oncology. Its untethering capacity to thrive in a confined microenvironment, metastasize intracranially, and remain resistant to the systemic treatments, renders this tumour incurable. The glial cell type specificity in GBM remains exploratory. In our study, we aimed to address this problem by studying the GBM at the cell type level in the brain. The cellular makeup of this tumour is composed of genetically altered glial cells which include astrocyte, microglia, oligodendrocyte precursor cell, newly formed oligodendrocyte and myelinating oligodendrocyte. We extracted cell type-specific solid tumour as well as recurrent solid tumour glioma genes, and studied their functional networks and contribution towards gliomagenesis. We identified the principal transcription factors that are found to be regulating vital tumorigenic processes. We also assessed the protein-protein interaction networks at their domain level to get a more microscopic view of the structural and functional operations that transpire in these cells. This yielded the eminent protein regulators exhibiting their regulation in signaling pathways. Overall, our study unveiled regulatory mechanisms in glioma cell types that can be targeted for a more efficient glioma therapy.

BTB and CNC homology 1 (Bach1) induces lung cancer stem cell phenotypes by stimulating CD44 expression

BACKGROUND

Growing evidence suggests that cancer stem cells (CSCs) are responsible for cancer initiation in tumors. Bach1 has been identified to contribute to several tumor progression, including lung cancer. The role of Bach1 in CSCs remains poorly known. Therefore, the function of Bach1 on lung CSCs was focused currently.

METHODS

The expression of Bach1, CD133, CD44, Sox2, Nanog and Oct4 mRNA was assessed using Real-Time Quantitative Reverse Transcription PCR (RT-qPCR). Protein expression of Bach1, CD133, CD44, Sox2, Nanog, Oct4, p53, BCL2, BAX, p-p38, p-AKT1, c-Fos and c-Jun protein was analyzed by western blotting. 5-ethynyl-29-deoxyuridine (EdU), colony formation, Flow cytometry analysis and transwell invasion assay were carried out to analyze lung cancer cell proliferation, apoptosis and invasion respectively. Tumor sphere formation assay was utilized to evaluate spheroid capacity. Flow cytometry analysis was carried out to isolate CD133 or CD44 positive lung cancer cells. The relationship between Bach1 and CD44 was verified using ChIP-qPCR and dual-luciferase reporter assay. Xenograft tumor tissues were collected for hematoxylin and eosin (HE) staining and IHC analysis to evaluate histology and Ki-67.

RESULTS

The ratio of CD44 + CSCs from A549 and SPC-A1 cells were significantly enriched. Tumor growth of CD44 + CSCs was obviously suppressed in vivo compared to CD44- CSCs. Bach1 expression was obviously increased in CD44 + CSCs. Then, via using the in vitro experiment, it was observed that CSCs proliferation and invasion were greatly reduced by the down-regulation of Bach1 while cell apoptosis was triggered by knockdown of Bach1. Loss of Bach1 was able to repress tumor-sphere formation and tumor-initiating CSC markers. A repression of CSCs growth and metastasis of shRNA-Bach1 was confirmed using xenograft models and caudal vein injection. The direct interaction between Bach1 and CD44 was confirmed by ChIP-qPCR and dual-luciferase reporter assay. Furthermore, mitogen-activated protein kinases (MAPK) signaling pathway was selected and we proved the effects of Bach1 on lung CSCs were associated with the activation of the MAPK pathway. As manifested, loss of Bach1 was able to repress p-p38, p-AKT1, c-Fos, c-Jun protein levels in lung CSCs. Inhibition of MAPK signaling remarkably restrained lung CSCs growth and CSCs properties induced by Bach1 overexpression.

CONCLUSION

In summary, we imply that Bach1 demonstrates great potential for the treatment of lung cancer metastasis and recurrence via activating CD44 and MPAK signaling.

BACH1 as a potential target for immunotherapy in glioblastomas

Glioblastoma (GBM, WHO grade 4) is a highly heterogeneous and aggressive primary malignant brain tumor. BTB domain and CNC homology 1 (BACH1) is a transcription factor, and it plays an essential role in regulating tumor metastasis, tumor metabolism, and tumor stem cell self-renewal. However, its role in glioma is still unclear. In this research, we confirmed that BACH1 as an independent prognostic indicator was enriched in GBMs. BACH1 was strongly correlated with immune responses in GBMs, especially the M0 and M2 tumor-associated macrophage (TAM) mediated immune responses. GBMs with high expression of BACH1 express high levels of immune checkpoints (ICs), glioma cell-derived TAM chemokines, and M2 TAM markers. Interestingly, single cell RNA-seq analysis showed that the expression level of BACH1 in TAMs was higher than that in the other cell types in GBM. Transcriptome analysis of U87-MG cells showed that compared with the BACH1-vector U87-MG group, glioma cell-derived TAM chemokines (including monocyte chemotactic protein-1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), and EGF) and ICs (including CD276, TIM-3, LAG3, TIGIT and LGALS9) were enriched in the BACH1-overexpressing U87-MG group. In addition, we constructed a polygenic risk scoring model and compound nomogram model based on BACH1, which might provide a reliable prognosis assessment tool for clinicians and aid in treatment decision-making in the clinic. In conclusion, this research identified that BACH1 might be a potential molecular signature for survival and immunotherapy response. GBMs with high expression of BACH1 have a stronger immunosuppressive tumor microenvironment (TME). Overexpression of BACH1 can upregulate the expression of glioma cell-derived TAM chemokines and ICs in vitro. Moreover, the risk model and nomogram model based on BACH1 can provide a reliable prognosis assessment tool. Therefore, BACH1 is a promising therapeutic target for GBMs.

Glioblastoma multiforme (GBM): An overview of current therapies and mechanisms of resistance

Glioblastoma multiforme (GBM) is a WHO grade IV glioma and the most common malignant, primary brain tumor with a 5-year survival of 7.2%. Its highly infiltrative nature, genetic heterogeneity, and protection by the blood brain barrier (BBB) have posed great treatment challenges. The standard treatment for GBMs is surgical resection followed by chemoradiotherapy. The robust DNA repair and self-renewing capabilities of glioblastoma cells and glioma initiating cells (GICs), respectively, promote resistance against all current treatment modalities. Thus, durable GBM management will require the invention of innovative treatment strategies. In this review, we will describe biological and molecular targets for GBM therapy, the current status of pharmacologic therapy, prominent mechanisms of resistance, and new treatment approaches. To date, medical imaging is primarily used to determine the location, size and macroscopic morphology of GBM before, during, and after therapy. In the future, molecular and cellular imaging approaches will more dynamically monitor the expression of molecular targets and/or immune responses in the tumor, thereby enabling more immediate adaptation of tumor-tailored, targeted therapies.

Identification of glioblastoma immune subtypes and immune landscape based on a large cohort

Glioblastomas (GBM) are the most common primary brain malignancy and also the most aggressive one. In addition, GBM have to date poor treatment options. Therefore, understanding the GBM microenvironment may help to design immunotherapy treatments and rational combination strategies. In this study, the gene expression profiles and clinical follow-up data were downloaded from TCGA-GBM, and the molecular subtypes were identified using ConsensusClusterPlus. Univariate and multivariate Cox regression were used to evaluate the prognostic value of immune subtypes. The Graph Structure Learning method was used for dimension reduction to reveal the internal structure of the immune system. A Weighted Correlation Network Analysis (WGCNA) was used to identify immune-related gene modules. Four immune subtypes (IS1, IS2, IS3, IS4) with significant prognosis differences were obtained. Interestingly, IS4 had the highest mutation rate. We also found significant differences in the distribution of the four subtypes at immune checkpoints, molecular markers, and immune characteristics. WGCNA identified 11 co-expressed module genes, and there were significant differences among the four subtypes. Finally, CD1A, CD1E, and IL23R genes with significant prognostic significance were selected as the final feature genes in the brown module. Overall, this study provided a conceptual framework for understanding the tumor immune microenvironment of GBM.

The transcription factor BACH1 at the crossroads of cancer biology: From epithelial-mesenchymal transition to ferroptosis

The progression of cancer involves not only the gradual evolution of cells by mutations in DNA but also alterations in the gene expression induced by those mutations and input from the surrounding microenvironment. Such alterations contribute to cancer cells' abilities to reprogram metabolic pathways and undergo epithelial-to-mesenchymal transition (EMT), which facilitate the survival of cancer cells and their metastasis to other organs. Recently, BTB and CNC homology 1 (BACH1), a heme-regulated transcription factor that represses genes involved in iron and heme metabolism in normal cells, was shown to shape the metabolism and metastatic potential of cancer cells. The growing list of BACH1 target genes in cancer cells reveals that BACH1 promotes metastasis by regulating various sets of genes beyond iron metabolism. BACH1 represses the expression of genes that mediate cell–cell adhesion and oxidative phosphorylation but activates the expression of genes required for glycolysis, cell motility, and matrix protein degradation. Furthermore, BACH1 represses FOXA1 gene encoding an activator of epithelial genes and activates SNAI2 encoding a repressor of epithelial genes, forming a feedforward loop of EMT. By synthesizing these observations, we propose a “two-faced BACH1 model”, which accounts for the dynamic switching between metastasis and stress resistance along with cancer progression. We discuss here the possibility that BACH1-mediated promotion of cancer also brings increased sensitivity to iron-dependent cell death (ferroptosis) through crosstalk of BACH1 target genes, imposing programmed vulnerability upon cancer cells. We also discuss the future directions of this field, including the dynamics and plasticity of EMT.

LINC00511 facilitates Temozolomide resistance of glioblastoma cells via sponging miR-126-5p and activating Wnt/β-catenin signaling

Temozolomide (TMZ) is the first-line chemotherapy drug for glioblastoma (GBM) but acquired TMZ resistance is frequently observed. Thus, a TMZ resistant GBM cell line U87-R was established to search for potential long noncoding RNAs (lncRNAs) used in TMZ resistance. In our study, LINC00511 was identified as a TMZ resistance-associated lncRNA in U87-R cells by transcriptome RNA sequencing. The potential functions of LINC00511 were evaluated by quantitative real-time polymerase chain reaction, cell viability assay, colony formation assay, western blot, soft agar assay, flow cytometry, tumor xenograft model, immunofluorescence, sphere formation assay, fluorescent in situ hybridization, luciferase reporter assay, and RNA pull-down assay. We found that LINC00511 was upregulated in U87-R cells and GBM samples, and correlated with poor prognosis of GBM patients. Silencing LINC00511 impaired TMZ tolerance of U87-R cells, while LINC00511 overexpression increased TMZ resistance of sensitive GBM cells. Wnt/β-catenin signaling was activated in U87-R cells, and inhibiting Wnt/β-catenin signaling enhanced TMZ sensitivity. Furthermore, LINC00511 was mainly distributed in the cytoplasm of GBM cells and regulated Wnt/β-catenin activation by acting as a molecular sponge for miR-126-5p. Multiple genes of Wnt/β-catenin signaling such as DVL3, WISP1, and WISP2 were targeted by miR-126-5p. MiR-126-5p restoration impaired TMZ resistance of GBM cells. In conclusion, our results provided a novel insight into acquired TMZ resistance of GBM cells and suggested LINC00511 as a potential biomarker or therapeutic target for GBM patients.

BACH1 is transcriptionally inhibited by TET1 in hepatocellular carcinoma in a microRNA-34a-dependent manner to regulate autophagy and inflammation

Hepatocellular carcinoma (HCC), one of the main contributors to cancer-associated deaths globally, is characterized by high invasiveness. Herein, we studied the molecular mechanisms underlying ten-eleven translocation 1 (TET1)-mediated autophagy in HCC. Following data mining using GSE101728, GSE14520 and GSE138178, TET1 was screened out, and the differential expression of TET1 was verified by bioinformatics analysis. TET1, one of the prognostic markers in HCC, was poorly expressed in HCC. Through functional experiments, we determined that upregulation of TET1 inhibited the proliferation, migration, invasion, tumorigenesis, metastasis and inflammatory factors of HCC cells, and promoted cell autophagy and apoptosis. Mechanistically, TET1 activated miR-34a by demethylating miR-34a. BTB domain and CNC homology 1 (BACH1) was identified as the target gene of miR-34a. Notably, Downregulation of miR-34a increased cellular inflammatory factors and decreased autophagy in the presence of TET1, while declines in BACH1 suppressed cellular inflammatory factors and enhanced autophagy in the presence of miR-34a inhibitor. BACH1 negatively regulated the p53 pathway. In conclusion, TET1 is a tumor suppressor in the progression of HCC by regulating the miR-34a/BACH1/p53 axis, and may contribute to the improvement of HCC prognosis and therapy.

High-resolution melting effectively pre-screens for TP53 mutations before direct sequencing in patients with diffuse glioma

TP53 mutations are important molecular markers in diffuse astrocytic tumors and medulloblastomas. We examined the efficacy of a pre-screening method for high-resolution melting (HRM) analysis of TP53 mutation before direct sequencing using samples from patients with diffuse glioma. Surgical samples from 64 diffuse gliomas were classified based on the 2016 World Health Organization (WHO) histopathological grading system and the cIMPACT-NOW (consortium to inform molecular and practical approaches to CNS tumor taxonomy-not official WHO) update. TP53 mutations from exon 5 to exon 8 were assessed by direct sequencing. The results of HRM and p53 immunohistochemistry (IHC) analysis were compared by recording the sensitivity, specificity, and false negative and false positive rates. Direct sequencing detected TP53 mutations in 18 of 64 samples (28.1%): diffuse astrocytoma, IDH-mutant (n = 3); diffuse astrocytoma, IDH-wild type (n = 1); anaplastic astrocytoma, IDH-mutant (n = 3); anaplastic astrocytoma, IDH-wild type (n = 4); and glioblastoma, IDH-wild type (n = 7). A total of 22 mutations was detected in the 18 samples; 4 samples exhibited duplicate missense mutations. Sensitivity and specificity were 0.96 and 0.96, respectively, for HRM analysis; they were 0.89 and 0.52, respectively, for p53 IHC. Overall accuracy was 0.98 for HRM and 0.63 for IHC. HRM analysis is a good pre-screening method for the detection of TP53 mutation before direct sequencing.

Evaluation of frequency magnetic field, static field, and Temozolomide on viability, free radical production and gene expression (p53) in the human glioblastoma cell line (A172)

Thirteen million cancer deaths and 21.7 million new cancer cases are expected in the world by 2030. Glioblastoma is the most common primary malignant tumor of the central nervous system which is the most lethal type of primary brain tumor in adults with the survival time of 12-15 months after the initial diagnosis. Glioblastoma is the most common and most malignant type of brain tumor, and despite surgery, chemotherapy and radiation treatment, the average survival of patients is about 14 months. The current research showed that the frequency magnetic field (FMF) and static magnetic field (SMF) can influence cancer cell proliferation and coupled with anticancer drugs may provide a new strategy for cancer therapy. At the present study, we investigated the effects of FMF (10 Hz, 50 G), SMF (50 G) and Temozolomide (200 μm) on viability, free radical production, and p53 followed by p53 protein expression in the human glioblastoma cell line (A172) by MTT, NBT, RT-PCR and Western blot. Results showed that the effect of Temozolomide (TMZ) with SMF and FMF together increased the cytotoxicity, free radical production, and p53 followed by p53 protein expression in the human glioblastoma cell line (A172).

Considering the Experimental use of Temozolomide in Glioblastoma Research

Temozolomide (TMZ) currently remains the only chemotherapeutic component in the approved treatment scheme for Glioblastoma (GB), the most common primary brain tumour with a dismal patient's survival prognosis of only ~15 months. While frequently described as an alkylating agent that causes DNA damage and thus-ultimately-cell death, a recent debate has been initiated to re-evaluate the therapeutic role of TMZ in GB. Here, we discuss the experimental use of TMZ and highlight how it differs from its clinical role. Four areas could be identified in which the experimental data is particularly limited in its translational potential: 1. transferring clinical dosing and scheduling to an experimental system and vice versa; 2. the different use of (non-inert) solvent in clinic and laboratory; 3. the limitations of established GB cell lines which only poorly mimic GB tumours; and 4. the limitations of animal models lacking an immune response. Discussing these limitations in a broader biomedical context, we offer suggestions as to how to improve transferability of data. Finally, we highlight an underexplored function of TMZ in modulating the immune system, as an example of where the aforementioned limitations impede the progression of our knowledge.

Combined elevation of TRIB2 and MAP3K1 indicates poor prognosis and chemoresistance to temozolomide in glioblastoma

Introduction

Glioblastoma (GBM) is the most lethal primary malignant brain tumor in adults with poor survival due to acquired therapeutic resistance and rapid recurrence. Currently, the standard clinical strategy for glioma includes maximum surgical resection, radiotherapy, and temozolomide (TMZ) chemotherapy; however, the median survival of patients with GBM remains poor despite these comprehensive therapies. Therefore, the identification of new prognostic biomarkers is urgently needed to evaluate the malignancy and long‐term outcome of glioma.

Aims

To further investigate prognostic biomarkers and potential therapeutic targets for GBM.

Results

In this study, we identified tribbles pseudokinase 2 (TRIB2) as one of the genes that is most correlated with pathological classification, radioresistance, and TMZ resistance in glioma. Additionally, the expression of mitogen‐activated protein kinase kinase kinase 1 (MAP3K1) showed a strong correlation with TRIB2. Moreover, a combined increase in TRIB2 and MAP3K1 was observed in GBM and indicated a poor prognosis of patients with glioma. Finally, enriched TRIB2 expression and MAP3K1 expression were shown to be associated with resistance to TMZ and radiotherapy.

Conclusion

Combined elevation of TRIB2 and MAP3K1 could be novel prognostic biomarkers and potential therapeutic targets to evaluate the malignancy and long‐term outcomes of GBM.

HMGA2 and Bach-1 cooperate to promote breast cancer cell malignancy

During breast cancer progression, tumor cells acquire multiple malignant features. The transcription factors and cell cycle regulators high mobility group A2 (HMGA2) and BTB and CNC homology 1 (Bach-1) are overexpressed in several cancers, but the mechanistic understanding of how HMGA2 and Bach-1 promote cancer development has been limited. We found that HMGA2 and Bach-1 are overexpressed in breast cancer tissues and their expression correlates positively in tumors but not in normal tissues. Individual HMGA2 or Bach-1 knockdown downregulates expression of both proteins, suggesting a mutual stabilizing effect between the two proteins. Importantly, combined HMGA2 and Bach-1 knockdown additively decrease cell proliferation, migration, epithelial-to-mesenchymal transition, and colony formation, while promoting apoptotic cell death via upregulation of caspase-3 and caspase-9. First the first time, we show that HMGA2 and Bach-1 overexpression in tumors correlate positively and that the proteins cooperatively suppress a broad range of malignant cellular properties, such as proliferation, migration, clonogenicity, and evasion of apoptotic cell death. Thus, our observations suggest that combined targeting of HMGA2 and Bach1 may be an effective therapeutic strategy to treat breast cancer.

Nuclear factor erythroid 2-related factors 1 and 2 are able to define the worst prognosis group among high-risk diffuse large B cell lymphomas treated with R-CHOEP

AIMS

Oxidative stress markers and antioxidant enzymes have previously been shown to have prognostic value and associate with adverse outcome in patients with diffuse large B cell lymphoma (DLBCL). Nuclear factor erythroid 2-related factor 1 (Nrf1) and factor 2 (Nrf2) are among the principal inducers of antioxidant enzyme production. Kelch ECH associating protein 1 (Keap1) is a negative regulator of Nrf2, and BTB (BR-C, ttk and bab) domain and CNC homolog 1 (Bach1) represses the function of both factors. Their significance in DLBCL prognosis is unknown.

METHODS

Diagnostic biopsy samples of 76 patients with high-risk DLBCL were retrospectively stained with immunohistochemistry for Nrf1, Nrf2, Keap1 and Bach1, and correlated with clinical data and outcome.

RESULTS

Nuclear Nrf2 and nuclear Bach1 expression were associated with adverse clinical features (anaemia, advanced stage, high IPI, high risk of neutropaenic infections), whereas cytoplasmic Nrf1 and Nrf2 were associated with favourable clinical presentation (normal haemoglobin level, no B symptoms, limited stage). None of the evaluated factors could predict survival alone. However, when two of the following parameters were combined: high nuclear score of Nrf2, low nuclear score of Nrf1, high cytoplasmic score of Nrf1 and low cytoplasmic score of Keap1 were associated with significantly worse overall survival.

CONCLUSIONS

Nrf1 and Nrf2 are relevant in disease presentation and overall survival in high-risk DLBCL. Low nuclear expression of Nrf1, high cytoplasmic expression of Nrf1, high nuclear expression of Nrf2 and low cytoplasmic expression of Keap1 are associated with adverse outcome in this patient group.

Fstl1/DIP2A/MGMT signaling pathway plays important roles in temozolomide resistance in glioblastoma

Temozolomide was recognized as the first-line therapy for glioblastoma to prolong the survival of patients noticeably, while recent clinical studies found that some patients were not sensitive to temozolomide treatment. The possible mechanisms seemed to be methylguanine-DNA-methyltransferase (MGMT), mismatch repair, PARP, etc. And the abnormal expression of MGMT might be the most direct factor. In this study, we provide evidence that Fstl1 plays a vital role in temozolomide resistance by sequentially regulating DIP2A protein distribution, H3K9 acetylation (H3K9Ac), and MGMT transcription. As a multifunctional protein widely distributed in cells, DIP2A cooperates with the HDAC2-DMAP1 complex to enhance H3K9Ac deacetylation, prevent MGMT transcription, and increase temozolomide sensitivity. Fstl1, a glycoprotein highly expressed in glioblastoma, competitively binds DIP2A to block DIP2A nuclear translocation, so as to hinder DIP2A from binding the HDAC2-DMAP1 complex. The overexpression of Fstl1 promoted the expression of MGMT in association with increased promoter H3K9Ac. Upregulation of Fstl1 enhanced temozolomide resistance, whereas Fstl1 silencing obviously sensitized GBM cells to temozolomide both in vivo and in vitro. Moreover, DIP2A depletion abolished the effects of Fstl1 on MGMT expression and temozolomide resistance. These findings highlight an important role of Fstl1 in the regulation of temozolomide resistance by modulation of DIP2A/MGMT signaling.

Deubiquitinating enzyme 4 facilitates chemoresistance in glioblastoma by inhibiting P53 activity

Glioblastoma is a malignant primary brain tumor with poor prognosis with a median survival of only 12–15 months. The high mortality rate of this disease is mainly due to the chemoresistance resulting from various reasons. Ubiquitin-specific protease 4 (USP4) has recently been found to be elevated in various types of cancer through regulating P53 activity. However, whether USP4 is responsible for chemoresistance in glioblastoma is not clear. In the present study, the expression of USP4 in glioblastoma tissues and cell lines, as well as its association with temozolomide (TMZ) chemoresistance was analyzed. The results demonstrated that USP4 was significantly upregulated in glioblastoma tissues and cell lines at the mRNA and protein levels. Notably, USP4 knockdown alone did not affect glioblastoma cell viability; however, when USP4 knockdown cells were treated with TMZ, the cell viability was decreased significantly. In addition, the results revealed that cleaved poly(ADP-ribose) polymerase level increased when USP4 was knocked down in glioblastoma cells treated with TMZ. It was also observed that P53 was increased in U251 and U87 cells with USP4 knockdown. Following treatment with a P53 specific inhibitor, the results suggested that USP4 mediated chemoresistance through inhibiting apoptosis in a P53-dependent manner. In conclusion, the data revealed the critical role of USP4 in TMZ resistance in glioblastoma and provided new insight for future drug development for the treatment of this disease.

Bach1: Function, Regulation, and Involvement in Disease

The transcription factor BTB and CNC homology 1 (Bach1) is widely expressed in most mammalian tissues and functions primarily as a transcriptional suppressor by heterodimerizing with small Maf proteins and binding to Maf recognition elements in the promoters of targeted genes. It has a key regulatory role in the production of reactive oxygen species, cell cycle, heme homeostasis, hematopoiesis, and immunity and has been shown to suppress ischemic angiogenesis and promote breast cancer metastasis. This review summarizes how Bach1 controls these and other cellular and physiological and pathological processes. Bach1 expression and function differ between different cell types. Thus, therapies designed to manipulate Bach1 expression will need to be tightly controlled and tailored for each specific disease state or cell type.

Identification of WISP1 as a novel oncogene in glioblastoma

Glioblastoma is the most common and aggressive primary brain tumor and has a high mortality in humans. However, mechanisms and factors involved in the progression of glioblastoma remain elusive. WISP1 (WNT1 inducible signaling pathway protein 1), has been suggested to be a critical regulator of cancer development. The aim of this study was to investigate the role of WISP1 in regulating the progression of glioblastoma. Clinicopathological characteristics of glioblastoma were assessed, and higher levels of WISP1 were positively associated with advanced clinical stage and a poor prognosis. Consistently, WISP1 expression was significantly upregulated in glioblastoma tissue and cell lines compared with normal tissue and cells. Additionally, inhibition of WISP1 greatly suppressed cell proliferation, migration, and invasion and promoted apoptosis and cell cycle arrest of glioblastoma cells. Further study indicated that downregulation of WISP1 suppressed cell proliferation associated with the gene expression of c‑myc and cyclin D1 and cellular signaling such as through the ERK pathway, while inhibiting epithelial-mesenchymal transition and MMP9. Finally, knockdown of WISP1 markedly suppressed in vivo tumor growth and sensitized glioblastoma cells to temozolomide. This study identified WISP1 as an oncogene in glioblastoma and suggests that WISP1 may serve as a potential molecular marker and treatment target for glioblastoma.

MicroRNA-141-3p promotes glioma cell growth and temozolomide resistance by directly targeting p53

Glioblastoma multiforme is the most common primary malignancy in the brain and confers a uniformly poor prognosis. MicroRNAs have been shown to activate or inhibit tumorigenesis. Abnormalities in the p53 signaling pathway are found in various cancers and correlate with tumor formation. We examined the expression of microRNA-141-3p (miR-141-3p) in glioma of different grades by analysis of expression profiling databases and clinical specimens. Cell proliferation and flow cytometry assays were performed to evaluate the promotion of miR-141-3p in proliferation, cell cycle, apoptosis, and temozolomide resistance of glioblastoma cells in vitro. Bioinformatics analyses, luciferase reporter assays, and immunoblotting showed that p53 is a target gene of miR-141-3p. A significant inverse correlation was observed between expression of miR-141-3p and p53 in glioma and normal brain tissues (R²=0.506, P<0.0001). Rescue experiments indicated that overexpression of p53 significantly reversed the alterations in proliferation, cell cycle distribution, and temozolomide resistance measured by cell apoptosis induced by miR-141-3p overexpression. In an orthotopic mouse model of human glioma, inhibition of miRNA-141-3p reduced the proliferation and growth of glioma cells in the brain and significantly prolonged the survival of glioma-bearing mice. We suggest that miR-141-3p promotes glioblastoma progression and temozolomide resistance by altering p53 expression and therefore may serve as a new diagnostic marker and therapeutic target for glioma in the future.

Dysregulation of Fra1 expression by Wnt/β-catenin signalling promotes glioma aggressiveness through epithelial-mesenchymal transition

Aberrant expression of Fos-related antigen-1 (Fra1) is commonly elevated in various malignant cancers and is strongly implicated in invasion and metastasis. However, the molecular mechanisms underlying its dysregulation in human glioma remain poorly understood. In the present study, we demonstrate that up-regulation of Fra1 plays a crucial role in the glioma aggressiveness and epithelial–mesenchymal transition (EMT) activated by Wnt/β-catenin signal pathway. In glioma cells, activation of Wnt/β-catenin signalling by Wnt3a administration obviously induced EMT and directly activated the transcription of Fra1. Phenotype experiments revealed that up-regulation of Fra1 induced by Wnt/β-catenin signalling drove the EMT of glioma cells. Furthermore, it was found that the cisplatin resistance acquired by Wnt/β-catenin signalling activation depended on increased expression of Fra1. Analysis of clinical specimens verified a positive correlation between Fra1 and β-catenin as well as a poor prognosis in glioma patients with double-high expressions of them. These findings indicate that an aberrant Wnt/β-catenin signalling leads to the EMT and drug resistance of glioma via Fra1 induction, which suggests novel therapeutic strategies for the malignant disease.