IKBKE enhances TMZ-chemoresistance through upregulation of MGMT expression in glioblastoma

Transcriptomic analysis identifies the neuropeptide cortistatin (CORT) as an inhibitor of temozolomide (TMZ) resistance by suppressing the NF-κB-MGMT signaling axis in human glioma

Glioma is a common tumor originating in the brain that has a high mortality rate. Temozolomide (TMZ) is the first-line treatment for high-grade gliomas. However, a large proportion of gliomas are resistant to TMZ, posing a great challenge to their treatment. In the study, the specific functions and mechanism(s) by which cortistatin (CORT) regulates TMZ resistance and glioma progression were evaluated. The decreased expression of CORT was detected in glioma tissues, and highly expressed CORT was associated with a better survival rate in patients with glioma. CORT overexpression notably decreased the capacity of glioma cells to proliferate and migrate in vitro and to form tumors in vivo. CORT overexpression also markedly suppressed the viability and enhanced the apoptosis of TMZ-resistant U251 cells by regulating MGMT, p21, and Puma expression. Importantly, CORT overexpression reduced the resistance of gliomas to TMZ in vivo. CORT expression was negatively correlated with MGMT expression in both glioma tissues and cells, and it was found that CORT inhibited NF-κB pathway activation in glioma cells, thereby inhibiting MGMT expression. In conclusion, CORT regulates glioma cell growth, migration, apoptosis, and TMZ resistance by weakening the activity of NF-κB/p65 and thereby regulating MGMT expression. The CORT/NF-κB/MGMT axis might be regarded as a molecular mechanism contributing to the resistance of glioma to TMZ. Our data also suggest that CORT regulates the viability and metastatic potential of glioma cells, independent of its effects on TMZ resistance, providing evidence of novel therapeutic targets for glioma that should be evaluated in further studies.

IKBKE promotes the ZEB2-mediated EMT process by phosphorylating HMGA1a in glioblastoma

IKBKE (Inhibitor of Nuclear Factor Kappa-B Kinase Subunit Epsilon) is an important oncogenic protein in a variety of tumors, which can promote tumor growth, proliferation, invasion and drug resistance, and plays a critical regulatory role in the occurrence and progression of malignant tumors. HMGA1a (High Mobility Group AT-hook 1a) functions as a cofactor for proper transcriptional regulation and is highly expressed in multiple types of tumors. ZEB2 (Zinc finger E-box Binding homeobox 2) exerts active functions in epithelial mesenchymal transformation (EMT). In our current study, we confirmed that IKBKE can increase the proliferation, invasion and migration of glioblastoma cells. We then found that IKBKE can phosphorylate HMGA1a at Ser 36 and/or Ser 44 sites and inhibit the degradation process of HMGA1a, and regulate the nuclear translocation of HMGA1a. Crucially, we observed that HMGA1a can regulate ZEB2 gene expression by interacting with ZEB2 promoter region. Hence, HMGA1a was found to promote the ZEB2-related metastasis. Consequently, we demonstrated that IKBKE can exert its oncogenic functions via the IKBKE/HMGA1a/ZEB2 signalling axis, and IKBKE may be a prominent biomarker for the treatment of glioblastoma in the future.

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.

Magnolol and Temozolomide exhibit a synergistic anti-glioma activity through MGMT inhibition

Temozolomide (TMZ) is the leading chemotherapeutic agent used for glioma therapy due to its good oral absorption and blood-brain barrier permeability. However, its anti-glioma efficacy may be limited due to its adverse effects and resistance development. O6-Methylguanine-DNA-methyltransferase (MGMT), an enzyme associated with TMZ resistance, is activated via the NF-κB pathway, which is found to be upregulated in glioma. TMZ also upregulates NF-κB signaling like many other alkylating agents. Magnolol (MGN), a natural anti-cancer agent, has been reported to inhibit NF-κB signaling in multiple myeloma, cholangiocarcinoma, and hepatocellular carcinoma. MGN has already shown promising results in anti-glioma therapy. However, the synergistic action of TMZ and MGN has not been explored. Therefore, we investigated the effect of TMZ and MGN treatment in glioma and observed their synergistic pro-apoptotic action in both in vitro and in vivo glioma models. To explore the mechanism of this synergistic action, we found that MGN inhibits MGMT enzyme both in vitro and in vivo glioma. Next, we established the link between NF-κB signaling and MGN-induced MGMT inhibition in glioma. MGN inhibits the phosphorylation of p65, a subunit of NF-κB, and its nuclear translocation to block NF-κB pathway activation in glioma. MGN-induced NF-κB inhibition results in the transcriptional inhibition of MGMT in glioma. TMZ and MGN combinatorial treatment also impedes p65 nuclear translocation to inhibit MGMT in glioma. We observed a similar effect of TMZ and MGN treatment in the rodent glioma model. Thus, we concluded that MGN potentiates TMZ-induced apoptosis in glioma by inhibiting NF-κB pathway-mediated MGMT activation.

The dual role of DNA repair protein MGMT in cancer prevention and treatment

Alkylating agents are genotoxic chemicals that can induce and treat various types of cancer. This occurs through covalent bonding with cellular macromolecules, in particular DNA, leading to the loss of functional integrity under the persistence of modifications upon replication. O6-alkylguanine (O6-AlkylG) adducts are proposed to be the most potent DNA lesions induced by alkylating agents. If not repaired correctly, these adducts can result, at the molecular level, in DNA point mutations, chromosome aberrations, recombination, crosslinking, and single- and double-strand breaks (SSB/DSBs). At the cellular level, these lesions can result in malignant transformation, senescence, or cell death. O6-methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein capable of removing the alkyl groups from O6-AlkylG adducts in a damage reversal process that can prevent the adverse biological effects of DNA damage caused by guanine O6-alkylation. MGMT can thereby defend normal cells against tumor initiation, however it can also protect tumor cells against the beneficial effects of chemotherapy. Hence, MGMT can play an important role in both the prevention and treatment of cancer; thus, it can be considered as a double-edged sword. From a clinical perspective, MGMT is a therapeutic target, and it is important to explore the rational development of its clinical exploitation.

The PYK2 inhibitor PF-562271 enhances the effect of temozolomide on tumor growth in a C57Bl/6-Gl261 mouse glioma model

BACKGROUND

The development of resistance to temozolomide (TMZ), a standard chemotherapeutic, limits the effective treatment of glioblastoma (GBM). Focal adhesion kinase (FAK) and proline rich tyrosine kinase 2 (Pyk2) regulate proliferation and invasion of GBM cells. We found that TMZ activates FAK and Pyk2 signaling in GBM. We hypothesized that pharmacological inhibitors of Pyk2/FAK together with TMZ can enhance the inhibitory effect of TMZ on tumor growth and dispersal and improve the treatment outcome.

METHODS

Primary human GBM cell cultures and a C57Bl/6-GL261 mouse glioma implantation model were used. Pyk2 (Tyr579/580) and FAK (Tyr925) phosphorylation was analyzed by western blotting. Viability, cell cycle, migration, invasion and invadopodia formation were investigated in vitro. Animal survival, tumor size and invasion, TUNEL apoptotic cell death and the Ki67 proliferation index were evaluated in vivo upon treatment with TMZ (50 mg/kg, once/day, orally) and the Pyk2/FAK inhibitor PF-562271 (once/daily, 50 mg/kg, orally) vs. TMZ monotherapy.

RESULTS

In vitro studies revealed significantly reduced viability, cell cycle progression, invasion and invadopodia with TMZ (100 µM) + PF-562271 (16 nM) compared with TMZ alone. In vivo studies demonstrated that combinatorial treatment led to prominent reductions in tumor size and invasive margins, extensive signs of apoptosis and a reduced proliferation index, together with a 15% increase in the survival rate in animals, compared with TMZ monotherapy.

CONCLUSION

TMZ + PF-562271 eliminates TMZ-related Pyk2/FAK activation in GBM and improves the treatment efficacy.

Spermidine/Spermine N1-Acetyltransferase 1 (SAT1)-A Potential Gene Target for Selective Sensitization of Glioblastoma Cells Using an Ionizable Lipid Nanoparticle to Deliver siRNA

Spermidine/spermine N1-acetyltransferase 1 (SAT1) responsible for cell polyamine catabolism is overexpressed in glioblastoma multiforme (GB). Its role in tumor survival and promoting resistance towards radiation therapy has made it an interesting target for therapy. In this study, we prepared a lipid nanoparticle-based siRNA delivery system (LNP-siSAT1) to selectively knockdown (KD) SAT1 enzyme in a human glioblastoma cell line. The LNP-siSAT1 containing ionizable DODAP lipid was prepared following a microfluidics mixing method and the resulting nanoparticles had a hydrodynamic size of around 80 nm and a neutral surface charge. The LNP-siSAT1 effectively knocked down the SAT1 expression in U251, LN229, and 42MGBA GB cells, and other brain-relevant endothelial (hCMEC/D3), astrocyte (HA) and macrophage (ANA-1) cells at the mRNA and protein levels. SAT1 KD in U251 cells resulted in a 40% loss in cell viability. Furthermore, SAT1 KD in U251, LN229 and 42MGBA cells sensitized them towards radiation and chemotherapy treatments. In contrast, despite similar SAT1 KD in other brain-relevant cells no significant effect on cytotoxic response, either alone or in combination, was observed. A major roadblock for brain therapeutics is their ability to cross the highly restrictive blood-brain barrier (BBB) presented by the brain microcapillary endothelial cells. Here, we used the BBB circumventing approach to enhance the delivery of LNP-siSAT1 across a BBB cell culture model. A cadherin binding peptide (ADTC5) was used to transiently open the BBB tight junctions to promote paracellular diffusion of LNP-siSAT1. These results suggest LNP-siSAT1 may provide a safe and effective method for reducing SAT1 and sensitizing GB cells to radiation and chemotherapeutic agents.

Glioma stem cell signature predicts the prognosis and the response to tumor treating fields treatment

INTRODUCTION

Glioma stem cells (GSCs) play an important role in glioma recurrence and chemo-radiotherapy (CRT) resistance. Currently, there is a lack of efficient treatment approaches targeting GSCs. This study aimed to explore the potential personalized treatment of patients with GSC-enriched gliomas.

METHODS

Single-cell RNA sequencing (scRNA-seq) was used to identify the GSC-related genes. Then, machine learning methods were applied for clustering and validation. The least absolute shrinkage and selection operator (LASSO) and COX regression were used to construct the risk scores. Survival analysis was performed. Additionally, the incidence of chemo-radiotherapy resistance, immunotherapy status, and tumor treating field (TTF) therapy response were evaluated in high- and low-risk scores groups.

RESULTS

Two GSC clusters exhibited significantly different stemness indices, immune microenvironments, and genomic alterations. Based on GSC clusters, 11-gene GSC risk scores were constructed, which exhibited a high predictive value for prognosis. In terms of therapy, patients with high GSC risk scores had a higher risk of resistance to chemotherapy. TTF therapy can comprehensively inhibit the malignant biological characteristics of the high GSC-risk-score gliomas.

CONCLUSION

Our study constructed a GSC signature consisting of 11 GSC-specific genes and identified its prognostic value in gliomas. TTF is a promising therapeutic approach for patients with GSC-enriched glioma.

YTHDF2 promotes temozolomide resistance in glioblastoma by activation of the Akt and NF-κB signalling pathways via inhibiting EPHB3 and TNFAIP3

Objectives

Temozolomide (TMZ) resistance is a key factor that restricts the therapeutic effect of glioblastoma (GBM). YTH‐domain family member 2 (YTHDF2) is highly expressed in GBM tissues, while the mechanism of YTHDF2 in TMZ resistance in GBM remains not fully elucidated.

Methods

The YTHDF2 expression in TMZ‐resistant tissues and cells was detected. Kaplan–Meier analysis was employed to evaluate the prognostic value of YTHDF2 in GBM. Effect of YTHDF2 in TMZ resistance in GBM was explored via corresponding experiments. RNA sequence, FISH in conjugation with fluorescent immunostaining, RNA immunoprecipitation, dual‐luciferase reporter gene and immunofluorescence were applied to investigate the mechanism of YTHDF2 that boosted TMZ resistance in GBM.

Results

YTHDF2 was up‐regulated in TMZ‐resistant tissues and cells, and patients with high expression of YTHDF2 showed lower survival rate than the patients with low expression of YTHDF2. The elevated YTHDF2 expression boosted TMZ resistance in GBM cells, and the decreased YTHDF2 expression enhanced TMZ sensitivity in TMZ‐resistant GBM cells. Mechanically, YTHDF2 bound to the N6‐methyladenosine (m⁶A) sites in the 3′UTR of EPHB3 and TNFAIP3 to decrease the mRNA stability. YTHDF2 activated the PI3K/Akt and NF‐κB signals through inhibiting expression of EPHB3 and TNFAIP3, and the inhibition of the two pathways attenuated YTHDF2‐mediated TMZ resistance.

Conclusion

YTHDF2 enhanced TMZ resistance in GBM by activation of the PI3K/Akt and NF‐κB signalling pathways via inhibition of EPHB3 and TNFAIP3.

An updated review on the potential antineoplastic actions of oleuropein

Oleuropein is an ester of elenolic acid and hydroxytyrosol (3, 4-dihydroxyphenylethanol). It is a phenolic compound and the most luxuriant in olives. The detailed information related to the anticancer effects of oleuropein was collected from the internet database PubMed/Medline, ResearchGate, Web of Science, Wiley Online Library, and Cnki using appropriate keywords until the end of October 2021. Oleuropein has been shown to have antioxidant, anticancer, antiinflammatory, cardioprotective, neuroprotective, and hepatoprotective effects. Previous studies also revealed that oleuropein could effectively inhibit the malignant progression of esophageal cancer, gastric cancer, breast cancer, lung cancer, liver cancer, pancreatic cancer, ovarian cancer, prostate cancer, and cervical cancer. Recently, the role of oleuropein in inhibiting tumor cell proliferation, invasion, and migration and inducing tumor cell apoptosis has gained extensive attention. In this review, we have summarized the latest research progress related to the antioncogenic mechanisms and the potential role of oleuropein in targeting different human malignancies. Based on these findings, it can be concluded that oleuropein can function as a promising chemopreventive and chemotherapeutic agent against cancer, but its more detailed anticancer effects and underlying mechanisms need to be further validated in future preclinical as well as clinical studies.

Elucidating the mechanisms of Temozolomide resistance in gliomas and the strategies to overcome the resistance

Temozolomide (TMZ) is a first-choice alkylating agent inducted as a gold standard therapy for glioblastoma multiforme (GBM) and astrocytoma. A majority of patients do not respond to TMZ during the course of their treatment. Activation of DNA repair pathways is the principal mechanism for this phenomenon that detaches TMZ-induced O-6-methylguanine adducts and restores genomic integrity. Current understanding in the domain of oncology adds several other novel mechanisms of resistance such as the involvement of miRNAs, drug efflux transporters, gap junction's activity, the advent of glioma stem cells as well as upregulation of cell survival autophagy. This review describes a multifaceted account of different mechanisms responsible for the intrinsic and acquired TMZ-resistance. Here, we summarize different strategies that intensify the TMZ effect such as MGMT inhibition, development of novel imidazotetrazine analog, and combination therapy; with an aim to incorporate a successful treatment and increased overall survival in GBM patients.

Mechanisms of temozolomide resistance in glioblastoma - a comprehensive review

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and has an exceedingly low median overall survival of only 15 months. Current standard-of-care for GBM consists of gross total surgical resection followed by radiation with concurrent and adjuvant chemotherapy. Temozolomide (TMZ) is the first-choice chemotherapeutic agent in GBM; however, the development of resistance to TMZ often becomes the limiting factor in effective treatment. While O6-methylguanine-DNA methyltransferase repair activity and uniquely resistant populations of glioma stem cells are the most well-known contributors to TMZ resistance, many other molecular mechanisms have come to light in recent years. Key emerging mechanisms include the involvement of other DNA repair systems, aberrant signaling pathways, autophagy, epigenetic modifications, microRNAs, and extracellular vesicle production. This review aims to provide a comprehensive overview of the clinically relevant molecular mechanisms and their extensive interconnections to better inform efforts to combat TMZ resistance.

A Review of Newly Diagnosed Glioblastoma

Glioblastoma is an aggressive and inevitably recurrent primary intra-axial brain tumor with a dismal prognosis. The current mainstay of treatment involves maximally safe surgical resection followed by radiotherapy over a 6-week period with concomitant temozolomide chemotherapy followed by temozolomide maintenance. This review provides a summary of the epidemiological, clinical, histologic and genetic characteristics of newly diagnosed disease as well as the current standard of care and potential future therapeutic prospects.

Tim-3 Expression and MGMT Methylation Status Association With Survival in Glioblastoma

BACKGROUND

A profound understanding of the molecular landscape of glioblastoma multiforme (GBM) will make it possible to develop better and more intelligent therapies directed toward specific molecular targets and may one day yield better prognostic capabilities. Immune checkpoint molecules have inspired the emergence of immune checkpoint-targeting therapeutic strategies. However, the prognostic significance of the immune checkpoint molecule T cell immunoglobulin mucin-3 (Tim-3) on tumor-infiltrating immune cells (TIICs) and O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status has not yet been fully elucidated. We aimed to develop an MGMT promoter methylation status-associated immune prognostic signature for GBM.

PATIENTS AND METHODS

A total of 84 patients with newly diagnosed GBM were included in this study. MGMT promoter methylation status was retrospectively analyzed, and the expression level of Tim-3 was investigated using immunohistochemistry (IHC). The correlation between Tim-3 expression combined with MGMT promoter methylation status and prognosis was explored.

RESULTS

Tim-3 expression varied in GBM patients. Mesenchymal expression of Tim-3 in GBM tissues was present 73.81% (62/84) of patients, and these were subdivided into groups based on low 15.48% (13/84), moderate 7.14% (6/84), or strong expression 51.19% (43/84). Forty-eight patients had tumors that tested positive for MGMT promoter methylation, while the remaining 36 patients tested negative.

CONCLUSIONS

We profiled the immune status of MGMT promoter methylation in GBM and established a local immune signature for GBM that could independently identify patients with a favorable prognosis, indicating a relationship between prognosis and GBM immune signature. MGMT promoter methylation with lower Tim-3 expression was significantly associated with better survival.