Opposed Interplay between IDH1 Mutations and the WNT/β-Catenin Pathway: Added Information for Glioma Classification

Immunological processes of enhancers and suppressors of long non-coding RNAs associated with brain tumors and inflammation

Immunological processes, such as inflammation, can both cause tumor suppression and cancer progression. Moreover, deregulated levels of long non-coding RNA (lncRNA) expression in the brain may cause inflammation and lead to the growth of tumors. Like other biological processes, the immune system's role in cancer is complicated, varies, and can help or hurt the cancer's maintenance. According to research, inflammation and brain cancer are correlated via several signaling pathways. A variety of lncRNAs have recently been revealed to influence cancer by modulating inflammatory pathways. As a result, lncRNAs have the potential to influence carcinogenesis, tumor formation, or tumor suppression via an increase or decrease in inflammation functions. Although the study and targeting of lncRNAs have made great progress in the treatment of cancer, there are definitely limitations and challenges. Using new technologies like nanocarriers and cell-penetrating peptides (CPPs) to target treatments without hurting healthy body tissues has shown to be very effective. In this review article, we have collected significantly related lncRNAs and their inhibitory or stimulating roles in inflammation and brain cancer for the first time. However, there are limitations, such as side effects and damage to normal tissues. With the advancement of new targeting technologies, these lncRNAs may be candidates for the specific targeting therapy of brain cancers by limiting inflammation or stimulating the immune system against them in the future.

Catalytically distinct IDH1 mutants tune phenotype severity in tumor models

Mutations in isocitrate dehydrogenase 1 (IDH1) impart a neomorphic reaction that produces the oncometabolite D-2-hydroxyglutarate (D2HG), which can inhibit DNA and histone demethylases to drive tumorigenesis via epigenetic changes. Though heterozygous point mutations in patients primarily affect residue R132, there are myriad D2HG-producing mutants that display unique catalytic efficiency of D2HG production. Here, we show that catalytic efficiency of D2HG production is greater in IDH1 R132Q than R132H mutants, and expression of IDH1 R132Q in cellular and mouse xenograft models leads to higher D2HG concentrations in cells, tumors, and sera compared to R132H-expressing models. Reduced representation bisulfite sequencing (RRBS) analysis of xenograft tumors shows expression of IDH1 R132Q relative to R132H leads to hypermethylation patterns in pathways associated with DNA damage. Transcriptome analysis indicates that the IDH1 R132Q mutation has a more aggressive pro-tumor phenotype, with members of EGFR, Wnt, and PI3K signaling pathways differentially expressed, perhaps through non-epigenetic routes. Together, these data suggest that the catalytic efficiency of IDH1 mutants modulate D2HG levels in cellular and in vivo models, resulting in unique epigenetic and transcriptomic consequences where higher D2HG levels appear to be associated with more aggressive tumors.

DKK3 Expression in Glioblastoma: Correlations with Biomolecular Markers

Glioblastoma is the most common malignant primary tumor of the CNS. The prognosis is dismal, with a median survival of 15 months. Surgical treatment followed by adjuvant therapies such as radiotherapy and chemotherapy characterize the classical strategy. The WNT pathway plays a key role in cellular proliferation, differentiation, and invasion. The DKK3 protein, capable of acting as a tumor suppressor, also appears to be able to modulate the WNT pathway. We performed, in a series of 40 patients, immunohistochemical and Western blot evaluations of DKK3 to better understand how the expression of this protein can influence clinical behavior. We used a statistical analysis, with correlations between the expression of DKK3 and overall survival, age, sex, Ki-67, p53, and MGMT and IDH status. We also correlated our data with information included in the cBioPortal database. In our analyses, DKK3 expression, in both immunohistochemistry and Western blot analyses, was reduced or absent in many cases, showing downregulation. To date, no clinical study exists in the literature that reports a potential correlation between IDH and MGMT status and the WNT pathway through the expression of DKK3. Modulation of this pathway through the expression of DKK3 could represent a new tailored therapeutic strategy in the treatment of glioblastoma.

An update on the molecular biology of glioblastoma, with clinical implications and progress in its treatment

Glioblastoma multiforme (GBM) is the most aggressive and common malignant primary brain tumor. Patients with GBM often have poor prognoses, with a median survival of ∼15 months. Enhanced understanding of the molecular biology of central nervous system tumors has led to modifications in their classifications, the most recent of which classified these tumors into new categories and made some changes in their nomenclature and grading system. This review aims to give a panoramic view of the last 3 years' findings in glioblastoma characterization, its heterogeneity, and current advances in its treatment. Several molecular parameters have been used to achieve an accurate and personalized characterization of glioblastoma in patients, including epigenetic, genetic, transcriptomic and metabolic features, as well as age- and sex-related patterns and the involvement of several noncoding RNAs in glioblastoma progression. Astrocyte-like neural stem cells and outer radial glial-like cells from the subventricular zone have been proposed as agents involved in GBM of IDH-wildtype origin, but this remains controversial. Glioblastoma metabolism is characterized by upregulation of the PI3K/Akt/mTOR signaling pathway, promotion of the glycolytic flux, maintenance of lipid storage, and other features. This metabolism also contributes to glioblastoma's resistance to conventional therapies. Tumor heterogeneity, a hallmark of GBM, has been shown to affect the genetic expression, modulation of metabolic pathways, and immune system evasion. GBM's aggressive invasion potential is modulated by cell-to-cell crosstalk within the tumor microenvironment and altered expressions of specific genes, such as ANXA2, GBP2, FN1, PHIP, and GLUT3. Nevertheless, the rising number of active clinical trials illustrates the efforts to identify new targets and drugs to treat this malignancy. Immunotherapy is still relevant for research purposes, given the amount of ongoing clinical trials based on this strategy to treat GBM, and neoantigen and nucleic acid-based vaccines are gaining importance due to their antitumoral activity by inducing the immune response. Furthermore, there are clinical trials focused on the PI3K/Akt/mTOR axis, angiogenesis, and tumor heterogeneity for developing molecular-targeted therapies against GBM. Other strategies, such as nanodelivery and computational models, may improve the drug pharmacokinetics and the prognosis of patients with GBM.

Crosstalk between PI3K/AKT/mTOR and WNT/β-Catenin signaling in GBM - Could combination therapy checkmate the collusion?

Glioblastoma multiforme is one of the calamitous primary glial brain tumors with extensive heterogeneity at cellular and molecular levels. While maximal surgical resection trailed by radio and chemotherapy employing temozolomide remains the gold-standard treatment for malignant glioma patients, the overall prognosis remains dismal and there exists an unmet need for effective therapeutic strategies. In this context, we hypothesize that proper understanding of signaling pathways responsible for glioblastoma multiforme proliferation would be the first trump card while searching for novel targeted therapies. Among the pathways aberrantly activated, PI3K/AKT/mTOR is the most significant pathway, that is clinically implicated in malignancies such as high-grade glioma. Further, the WNT/β-Catenin cascade is well-implicated in several malignancies, while its role in regulating glioma pathogenesis has only emerged recently. Nevertheless, oncogenic activation of both these pathways is a frequent event in malignant glioma that facilitates tumor proliferation, stemness and chemo-resistance. Recently, it has been reported that the cross-talk of PI3K/AKT/mTOR pathway with multiple signaling pathways could promote glioma progression and reduce the sensitivity of glioma cells to the standard therapy. However, very few studies had focused on the relationship between PI3K/AKT/mTOR and WNT/β-Catenin pathways in glioblastoma multiforme. Interestingly, in homeostatic and pathologic circumstances, both these pathways depict fine modulation and are connected at multiple levels by upstream and downstream effectors. Thus, gaining deep insights on the collusion between these pathways would help in discovering unique therapeutic targets for glioblastoma multiforme management. Hence, the current review aims to address, "the importance of inter-play between PI3K/AKT/mTOR and WNT/β-Catenin pathways", and put forward, "the possibility of combinatorially targeting them", for glioblastoma multiforme treatment enhancement.