The interplay mechanism between IDH mutation, MGMT-promoter methylation, and PRMT5 activity in the progression of grade 4 astrocytoma: unraveling the complex triad theory

Background:The dysregulation of Isocitrate dehydrogenase(IDH)and the subsequent production of 2-Hydroxyglutrate(2HG)may alter the expression of epigenetic proteins in Grade 4 astrocytoma.The interplay mechanism between IDH,O-6-methylguanine-DNA methyltransferase(MGMT)-promoter methylation,and protein methyltransferase proteins-5(PRMT5)activity,with tumor progression has never been described.Methods:A retrospective cohort of 34 patients with G4 astrocytoma is classified into IDH-mutant and IDH-wildtype tumors.Both groups were tested for MGMT-promoter methylation and PRMT5 through methylation-specific and gene expression PCR analysis.Inter-cohort statistical significance was evaluated.Results:Both IDH-mutant WHO grade 4 astrocytomas(n=22,64.7%)and IDH-wildtype glioblastomas(n=12,35.3%)had upregulated PRMT5 gene expression except in one case.Out of the 22 IDH-mutant tumors,10(45.5%)tumors showed MGMT-promoter methylation and 12(54.5%)tumors had unmethylated MGMT.All IDH-wildtype tumors had unmethylated MGMT.There was a statistically significant relationship between MGMT-promoter methylation and IDH in G4 astrocytoma(p-value=0.006).Statistically significant differences in progression-free survival(PFS)were also observed among all G4 astrocytomas that expressed PRMT5 and received either temozolomide(TMZ)or TMZ plus other chemotherapies,regardless of their IDH or MGMT-methylation status(p-value=0.0014).Specifically,IDH-mutant tumors that had upregulated PRMT5 activity and MGMT-promoter methylation,who received only TMZ,have exhibited longer PFS.Conclusions:The relationship between PRMT5,MGMT-promoter,and IDH is not tridirectional.However,accumulation of D2-hydroxyglutarate(2-HG),which partially activates 2-OG-dependent deoxygenase,may not affect their activities.In IDH-wildtype glioblastomas,the 2HG-2OG pathway is typically inactive,leading to PRMT5 upregulation.TMZ alone,compared to TMZ-plus,can increase PFS in upregulated PRMT5 tumors.Thus,using a PRMT5 inhibitor in G4 astrocytomas may help in tumor regression.

Immune microenvironment of medulloblastoma:The association between its molecular subgroups and potential targeted immunotherapeutic receptors

Medulloblastoma(MB)is considered the commonest malignant brain tumor in children.Multimodal treatments consisting of surgery,radiation,and chemotherapy have improved patients’survival.Nevertheless,the recurrence occurs in 30%of cases.The persistent mortality rates,the failure of current therapies to extend life expectancy,and the serious complications of non-targeted cytotoxic treatment indicate the need for more refined therapeutic approaches.Most MBs originating from the neurons of external granular layer line the outer surface of neocerebellum and responsible for the afferent and efferent connections.Recently,MBs have been segregated into four molecular subgroups:Wingless-activated(WNT-MB)(Group 1);Sonichedgehog-activated(SHH-MB)(Group 2);Group 3 and 4 MBs.These molecular alterations follow specific gene mutations and disease-risk stratifications.The current treatment protocols and ongoing clinical trials against these molecular subgroups are still using common chemotherapeutic agents by which their efficacy have improved the progression-free survival but did not change the overall survival.However,the need to explore new therapies targeting specific receptors in MB microenvironment became essential.The immune microenvironment of MBs consists of distinctive cellular heterogeneities including immune cells and none-immune cells.Tumour associate macrophage and tumour infiltrating lymphocyte are considered the main principal cells in tumour microenvironment,and their role are still under investigation.In this review,we discuss the mechanism of interaction between MB cells and immune cells in the microenvironment,with an overview of the recent investigations and clinical trials.

Simple approach for the histomolecular diagnosis of central nervous system gliomas based on 2021 World Health Organization Classification

The classification of central nervous system(CNS)glioma went through a sequence of developments,between 2006 and 2021,started with only histological approach then has been aided with a major emphasis on molecular signatures in the 4^(th) and 5^(th) editions of the World Health Organization(WHO).The recent reformation in the 5th edition of the WHO classification has focused more on the molecularly defined entities with better characterized natural histories as well as new tumor types and subtypes in the adult and pediatric populations.These new subclassified entities have been incorporated in the 5^(th) edition after the continuous exploration of new genomic,epigenomic and transcriptomic discovery.Indeed,the current guidelines of 2021 WHO classification of CNS tumors and European Association of Neuro-Oncology(EANO)exploited the molecular signatures in the diagnostic approach of CNS gliomas.Our current review presents a practical diagnostic approach for diffuse CNS gliomas and circumscribed astrocytomas using histomolecular criteria adopted by the recent WHO classification.We also describe the treatment strategies for these tumors based on EANO guidelines.