GBM Cells Exhibit Susceptibility to Metformin Treatment According to TLR4 Pathway Activation and Metabolic and Antioxidant Status.

Glioblastoma (GBM) is an aggressive brain cancer associated with poor overall survival. The metabolic status and tumor microenvironment of GBM cells have been targeted to improve therapeutic strategies. TLR4 is an important innate immune receptor capable of recognizing pathogens and danger-associated molecules. We have previously demonstrated the presence of TLR4 in GBM tumors and the decreased viability of the GBM tumor cell line after lipopolysaccharide (LPS) (TLR4 agonist) stimulation. In the present study, metformin (MET) treatment, used in combination with temozolomide (TMZ) in two GBM cell lines (U87MG and A172) and stimulated with LPS was analyzed. MET is a drug widely used for the treatment of diabetes and has been repurposed for cancer treatment owing to its anti-proliferative and anti-inflammatory actions. The aim of the study was to investigate MET and LPS treatment in two GBM cell lines with different metabolic statuses. MET treatment led to mitochondrial respiration blunting and oxidative stress with superoxide production in both cell lines, more markedly in U87MG cells. Decreased cell viability after MET + TMZ and MET + LPS + TMZ treatment was observed in both cell lines. U87MG cells exhibited apoptosis after MET + LPS + TMZ treatment, promoting increased ER stress, unfolded protein response, and BLC2 downregulation. LPS stimulation of U87MG cells led to upregulation of SOD2 and genes related to the TLR4 signaling pathway, including IL1B and CXCL8. A172 cells attained upregulated antioxidant gene expression, particularly SOD1, TXN and PRDX1-5, while MET treatment led to cell-cycle arrest. In silico analysis of the TCGA-GBM-RNASeq dataset indicated that the glycolytic plurimetabolic (GPM)-GBM subtype had a transcriptomic profile which overlapped with U87MG cells, suggesting GBM cases exhibiting this metabolic background with an activated inflammatory TLR4 pathway may respond to MET treatment. For cases with upregulated CXCL8, coding for IL8 (a pro-angiogenic factor), combination treatment with an IL8 inhibitor may improve tumor growth control. The A172 cell line corresponded to the mitochondrial (MTC)-GBM subtype, where MET plus an antioxidant inhibitor, such as anti-SOD1, may be indicated as a combinatory therapy.

Glutaminolysis dynamics during astrocytoma progression correlates with tumor aggressiveness.

BACKGROUND: Glioblastoma is the most frequent and high-grade adult malignant central nervous system tumor. The prognosis is still poor despite the use of combined therapy involving maximal surgical resection, radiotherapy, and chemotherapy. Metabolic reprogramming currently is recognized as one of the hallmarks of cancer. Glutamine metabolism through glutaminolysis has been associated with tumor cell maintenance and survival, and with antioxidative stress through glutathione (GSH) synthesis. METHODS: In the present study, we analyzed the glutaminolysis-related gene expression levels in our cohort of 153 astrocytomas of different malignant grades and 22 non-neoplastic brain samples through qRT-PCR. Additionally, we investigated the protein expression profile of the key regulator of glutaminolysis (GLS), glutamate dehydrogenase (GLUD1), and glutamate pyruvate transaminase (GPT2) in these samples. We also investigated the glutathione synthase (GS) protein profile and the GSH levels in different grades of astrocytomas. The differential gene expressions were validated in silico on the TCGA database. RESULTS: We found an increase of glutaminase isoform 2 gene (GLSiso2) expression in all grades of astrocytoma compared to non-neoplastic brain tissue, with a gradual expression increment in parallel to malignancy. Genes coding for GLUD1 and GPT2 expression levels varied according to the grade of malignancy, being downregulated in glioblastoma, and upregulated in lower grades of astrocytoma (AGII-AGIII). Significant low GLUD1 and GPT2 protein levels were observed in the mesenchymal subtype of GBM. CONCLUSIONS: In glioblastoma, particularly in the mesenchymal subtype, the downregulation of both genes and proteins (GLUD1 and GPT2) increases the source of glutamate for GSH synthesis and enhances tumor cell fitness due to increased antioxidative capacity. In contrast, in lower-grade astrocytoma, mainly in those harboring the IDH1 mutation, the gene expression profile indicates that tumor cells might be sensitized to oxidative stress due to reduced GSH synthesis. The measurement of GLUD1 and GPT2 metabolic substrates, ammonia, and alanine, by noninvasive MR spectroscopy, may potentially allow the identification of IDH1mut AGII and AGIII progression towards secondary GBM.

Coenzyme A levels influence protein acetylation, CoAlation and 4'-phosphopantetheinylation: Expanding the impact of a metabolic nexus molecule.

Coenzyme A (CoA) is a key molecule in cellular metabolism including the tricarboxylic acid cycle, fatty acid synthesis, amino acid synthesis and lipid metabolism. Moreover, CoA is required for biological processes like protein post-translational modifications (PTMs) including acylation. CoA levels affect the amount of histone acetylation and thereby modulate gene expression. A direct influence of CoA levels on other PTMs, like CoAlation and 4'-phosphopantetheinylation has been relatively less addressed and will be discussed here. Increased CoA levels are associated with increased CoAlation, whereas decreased 4'-phosphopantetheinylation is observed under circumstances of decreased CoA levels. We discuss how these two PTMs can positively or negatively influence target proteins depending on CoA levels. This review highlights the impact of CoA levels on post-translational modifications, their counteractive interplay and the far-reaching consequences thereof.

Plasmatic membrane toll-like receptor expressions in human astrocytomas.

Toll-like receptors (TLRs) are the first to identify disturbances in the immune system, recognizing pathogens such as bacteria, fungi, and viruses. Since the inflammation process plays an important role in several diseases, TLRs have been considered potential therapeutic targets, including treatment for cancer. However, TLRs' role in cancer remains ambiguous. This study aims to analyze the expression levels of plasmatic cell membrane TLRs (TLR1, TLR2, TLR4, TLR5, and TLR6) in human astrocytomas the most prevalent tumors of CNS different grades (II-IV). We demonstrated that TLR expressions were higher in astrocytoma samples compared to non-neoplastic brain tissue. The gene and protein expressions were observed in GBM cell lines U87MG and A172, proving their presence in the tumor cells. Associated expressions between the known heterodimers TLR1-TLR2 were found in all astrocytoma grades. In GBMs, the mesenchymal subtype showed higher levels of TLR expressions in relation to classical and proneural subtypes. A strong association of TLRs with the activation of cell cycle process and signaling through canonical, inflammasome and ripoptosome pathways was observed by in silico analysis, further highlighting TLRs as interesting targets for cancer treatment.

The impact of interleukin-13 receptor expressions in cell migration of astrocytomas / O impacto da expressão dos receptores de interleucina-13 na migração celular em astrocitomas

INTRODUCTION: Astrocytomas are common brain tumors. Increased expression levels of Interleukin-13 Receptor α2 (IL-13RA2) have been reported in astrocytomas. The Interleukin-13 signaling pathway may be associated with cell migration when binding to Interleukin-13 Receptor α1. OBJECTIVE: To investigate Interleukin-13 Receptor α1 (IL-13RA1) and IL13RA2 expression levels in human diffusely infiltrative astrocytomas and test the involvement of Interleukin-13 levels in cell migration in two glioblastoma cell lines. METHODS: IL13RA expression levels were accessed by quantitative real time PCR in 128 samples of astrocytomas and 18 samples of non-neoplastic brain tissues from temporal lobe epilepsy surgery. The impact of IL-13 levels (10 and 20 ng/mL) on cell migration was analyzed by the wound assay in U87MG and A172 cells. RESULTS: Glioblastoma presented higher IL13RA1 and IL13RA2 expression levels compared to lower grades astrocytomas and to non-neoplastic cases. U87MG and A172 cells presented higher expression levels of IL-13RA1 vs. IL-13RA2. A significant difference in migration rate was observed in A172 cells treated with 10 ng/mL of IL-13 vs. control: treated cells presented slower migration than non-treated cells. U87MG cells treated with IL-13 20ng/mL presented slower migration than non-treated cells. This indicates that the IL13Rα1 signaling pathway was not activated, indeed inhibited by the decoy IL-13Rα2, slowing cell migration. This impact occurred with a lesser concentration of IL-13 on the A172 than on the U87MG cell line, because A172 cells have a higher IL-13RA2/A1 ratio. CONCLUSION: The present results suggest IL-13 receptors as possible targets to decrease tumor cell migration.

INTRODUÇÃO Astrocitomas são os tumores cerebrais mais frequentes. Nestes tumores foi observada maior expressão do receptor de Interleucina-13 α2 (IL13RA2). A cascata de sinalização da Interleucina-13 pode estar associada com a migração celular, após sua ligação com o receptor de Interleucina-13 α1 (IL13Rα1). OBJETIVO: Investigar os níveis de expressão dos receptores de Interleucina-13 (IL13RA1 e IL13RA2) em astrocitomas difusamente infiltrativos e avaliar o envolvimento da Interleucina-13 na migração celular de duas linhagens de glioblastoma. MÉTODOS: A expressão dos receptores IL13RA foi analisada por PCR em tempo real, em 128 amostras de astrocitomas e 18 amostras de tecido cerebral não neoplásico, provenientes de cirurgia de epilepsia do lobo temporal. E o impacto da quantidade de IL-13 (10ng/ml e 20ng/ml) em ensaio de migração celular. RESULTADOS: As amostras de Glioblastoma apresentaram maior expressão de IL13RA1 and IL13RA2 comparados com astrocitomas de baixo grau e os casos não-neoplásicos. Nas células U87MG e A172 foi observado maior nível de expressão de IL-13RA1 do que IL-13RA2. Uma diferença significativa na taxa de migração foi obtida em células A172 tratadas com 10 ng/mL comparadas com o controle: as células tratadas apresentaram menor migração que as células não tratadas. As células U87MG tratadas com 20ng/mL de IL-13 apresentaram menor migração celular que as células não tratadas. A diferença na migração celular indica que o caminho de sinalização de IL13Rα1 não foi ativado e foi inibido pelo IL-13Rα2, diminuindo a migração celular. Esse impacto ocorreu com uma concentração menor de IL-13 nas células A172 ao contrário da U87MG, porque as células A172 possuem uma razão IL-13RA2/A1 maior. CONCLUSÃO: os resultados sugerem que os receptores de IL-13 podem ser utilizados como possíveis alvos para a diminuição da migração celular tumoral.