SummarySince the discovery of mutations in isocitrate dehydrogenase 1 (IDH1) in gliomas and other tumors, significant efforts have been made to gain a deeper understanding of the consequences of this oncogenic mutation. One aspect of the neomorphic function of the IDH1 R132H enzyme that has received less attention is the perturbation of cellular redox homeostasis. Here, we describe a biosynthetic pathway exhibited by cells expressing mutant IDH1. By virtue of a change in cellular redox homeostasis, IDH1-mutated cells synthesize excess glutamine-derived proline through enhanced activity of pyrroline 5-carboxylate reductase 1 (PYCR1), coupled to NADH oxidation. Enhanced proline biosynthesis partially uncouples the electron transport chain from tricarboxylic acid (TCA) cycle activity through the maintenance of a lower NADH/NAD+ ratio and subsequent reduction in oxygen consumption. Thus, we have uncovered a mechanism by which tumor cell survival may be promoted in conditions associated with perturbed redox homeostasis, as occurs in IDH1-mutated glioma.

Nucleolin is a multifunctional DNA and RNA binding protein involved in regulation of gene transcription, chromatin remodeling, RNA metabolism, and ribosomal RNA synthesis. Nucleolin seems to be over-expressed in highly proliferative cells and is involved in many aspect of gene expression: DNA recombination and replication, RNA transcription by RNA polymerase I and II, rRNA processing, mRNA stabilization, cytokinesis, and apoptosis. Although nucleolin is localized predominantly in the nucleolus, it has also been shown to be localized in a phosphorylated/glycolsilated form on the cell surface of different cells. Numerous articles dealing with surface nucleolin targeting for tumor therapy have been recently published. However, at present, no extensive informations are so far available for the presence of nucleolin in human gliomas. In the present work we investigated on the presence and localization of nucleolin in glioma on glioma specimens at different grade of malignancy and on primary glioma cell cultures derived by surgical resection, trying to correlate the presence of glycosilated membrane nucleolin with the malignancy grade. To this purpose an antibody produced by us against gp273 protein, demonstrated to recognized the glycosilated surface nucleolin, has been used. The results obtained demonstrate that surface nucleolin increase with the malignancy grade thus suggesting that it may constitute a histopathological marker for glioma grading and a possible tool for targeted therapy.

In the early 1920s Otto Warburg observed that cancer cells have altered metabolism and from this, posited that mitochondrial dysfunction underpinned the aetiology of cancers. The more recent identification of mutations of mitochondrial metabolic enzymes in a wide range of human cancers has now provided a direct link between metabolic alterations and cancer. In this review we discuss the consequences of dysfunction of three metabolic enzymes involved in or associated with the tricarboxylic acid (TCA) cycle: succinate dehydrogenase (SDH), fumarate hydratase (FH) and isocitrate dehydrogenase (IDH) focusing on the similarity between the phenotypes of cancers harbouring these mutations.

Glioblastoma multiforme (GBM) represents the most severe type of glioma, the most common brain tumor. Their malignancy shows a relationship with an increased proliferation and a poorly organized tumor vascularization, an event that leads to inadequate blood supply, hypoxic areas and at last to the formation of necrotic areas, a feature of glioblastoma. Hypoxic/necrotic tumors are more resistant to chemotherapy and radiation therapies, thus it is crucial to formulate new therapeutic approaches that can render these tumors more sensitive to the action of conventional therapies. It has been demonstrated that under hypoxia, gliomas accumulate lipid droplets and that this event is positively correlated with the degree of malignancy, glioblastoma being the most endowed with lipid droplets. We have previously demonstrated in ex vivo glioma specimens a grade-dependent lipid metabolism perturbation. Here we studied the lipid pathways and the presence of stemness markers in glioma primary cultures, obtained from surgical specimens of patients affected by glioma at different grade of malignancy, GBM primary cultures cultured under both hypoxic and normoxic conditions, as well as normal human astrocytes. The results obtained demonstrate that hypoxia plays a crucial role in regulating the expression of lipid metabolism peroxisomal enzymes, the lipid droplets accumulation as well as the transcription factor PPARα.

Gliomas are histologically graded by cellularity, cytological atypia, necrosis, mitotic figures, and vascular proliferation, features associated with biologically aggressive behaviour. However, abundant evidence suggests the presence of unrecognized, clinically relevant subclasses of the diffuse gliomas, both in respect to their underlying molecular phenotype and their clinical response to therapy. It is wellknown that patient prognosis and therapeutic decisions rely on accurate pathological grading. Recently, it was reported that human gliomas accumulate lipid droplets during progression, suggesting a lipid metabolism impairment. Considering the crucial role of peroxisomes in lipid metabolism, in the present work we studied the expression profiles of proteins either exclusively localized to peroxisomes, such as peroxin14 (PEX14), peroxisomal membrane protein 70Kda (PMP70), acyl-CoA oxidase, thiolase, or partially associated to peroxisomes such as Hydroxymethylglutaryl-CoA reductase (HMGCoA-red) and peroxisomal-related proteins, namely PPARa, in human glioma specimens at different grades of malignancy. Moreover, Nile red staining of lipid droplets, thin layer chromatography (TLC) and proton nuclear magnetic resonance spectroscopy (NMR) were carried out in order to correlate the biochemical results with the lipid content of tumor tissues. The results obtained indicate that correlating the malignancy grade with the expression of peroxisomal genes and proteins, may constitute a sensitive tool to highlight possible subtypes not recognized by the classical histological techniques.