Pentose phosphate pathway inhibition induce Endoplasmic Reticulum stress and autophagy

Pentose phosphate pathway (PPP) is a major glucose catabolism pathway that supplies the cell with a reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) and ribose-5-phosphate. NADPH is necessary for the detoxification of reactive oxygen species (ROS) and reductive biosynthesis. A key player in this pathway is the enzyme glucose-6-phosphate dehydrogenase (G6PD) that reduces NADP+ to NADPH, oxidizes glucose-6-phosphate and prevents ROS accumulation. Here, we show that the natural molecule 3,4’,5-trihydroxystilbene-3-β-d-glucoside (Polydatin) inhibits glucose-6-phosphate dehydrogenase (G6PD). As expected, G6PD inhibition causes an imbalance in NADP+/NADPH ratio, leading to a redox imbalance, followed by Endoplasmic Reticulum (ER) stress, autophagy, cell cycle block and apoptosis. we have demonstrated a link between G6PD inhibition and ER stress, showing that Unfolded Protein Response mediator such as PERK and IRE-1 have a key role in inducing autophagy and apoptosis after PPP block. Moreover, combination of PPP inhibition with autophagy inhibitors, such as chloroquine, strongly potentiate cytotoxicity on cancer cells, evidencing the role of autophagy as an escaping mechanism. This results shows that double inhibition of PPP and autophagy may be an affective therapeutic strategy against cancer

HDAC2 depletion promotes osteosarcoma's stemness both in vitro and in vivo: a study on a putative new target for CSCs directed therapy

Background: Cancer stem cells (CSCs) play a key role in cancer initiation, progression and chemoresistance. Epigenetic alterations have been identified as prominent factors that contribute to the CSCs phenotype. Here, we investigated the effects of the HDAC inhibitor valproic acid (VPA) and the demethylating agent, 5’azacytidine (DAC) on the stem phenotype of MG63 and Saos2 osteosarcoma cell lines. Methods: Saos2 and MG63 cells were treated with DAC and VPA, alone and in combination. Untreated and treated cells were examined for stemness phenotype by cytometry and real-time PCR. Sarcospheres and colonies formation were also evaluated. Moreover, histone modification and methylation were tested by flow cytomery and western blotting. HDAC2 depleted cells were examined for stemness phenotype and their ability to generate tumors in NOD/SCID IL2R-gamma-0 (NSG) mice. HDAC2 expression on human osteosarcoma tissues was evaluated. Results: We found that DAC and VPA induce an increased expression of stem markers including CD133, OCT4, SOX2 and NANOG, and an increased ability in sarcospheres and colonies formation efficiency. Interestingly, we showed that DAC and VPA treatment decreased repressive histone markers, while increased the active ones. These histone modifications were also associated with an increase of acetylation of histones H3, a decrease of DNA global methylation, HDAC2 and DNMT3a. Furthermore, HDAC2 silenced-MG63 and Saos2 cells acquired a stem phenotype, and promoted in vivo tumorigenesis. In human osteosarcoma tissues, HDAC2 was strongly expressed in nucleus. Conclusions: Collectively, our results suggest that VPA and DAC induce an expansion of osteosarcoma CSCs, and we report for the first time that HDAC2 is a key factor regulating both CSCs phenotype and in vivo cancer growth. In conclusion, we have identified HDAC2 as a potential therapeutic target in human osteosarcoma treatment

Principles of stem cell biology and cancer : future applications and therapeutics/ Edit.: Tarik Regad

xii, 362 p.: tab.; 24 cm

Rôle et devenir des corps nucléaires PML en réponse à l' interféron et lors des infections virales par le HFV et le virus de la rage

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Long non-coding RNAs in cancer stem cells

In recent years, it has been evidenced that the human transcriptome includes several types of non-coding RNAs (ncRNAs) that are mainly involved in the regulation of different cellular processes. Among ncRNAs, long-non-coding RNAs (lncRNAs) are defined as longer than 200 nucleotides and have been shown to be involved in several physiological and pathological events, including immune system regulation and cancer. Cancer stem cells (CSCs) are defined as a population of cancer cells that possess characteristics, such as resistance to standard treatments, cancer initiation, ability to undergo epithelial-to-mesenchymal transition, and the ability to invade, spread, and generate metastases. The cancer microenvironment, together with genetic and epigenetic factors, is fundamental for CSC maintenance and tumor growth and progression. Unsurprisingly, lncRNAs have been involved in both CSC biology and cancer progression, prognosis and recurrence. Here we review the most recent literature on IncRNAs involvement in CSC biology and function

PML mediates the interferon-induced antiviral state against a complex retrovirus via its association with the viral transactivator

The promyelocytic leukaemia (PML) protein localizes in the nucleus both in the nucleoplasm and in matrix-associated multiprotein complexes known as nuclear bodies (NBs). The number and the intensity of PML NBs increase in response to interferon (IFN). Overexpression of PML affects the replication of vesicular stomatitis virus and influenza virus. However, PML has a less powerful antiviral activity against these viruses than the IFN mediator MxA. Here, we show that overexpression of PML, but not that of Mx1 or MxA, leads to a drastic decrease of a complex retrovirus, the human foamy virus (HFV), gene expression. PML represses HFV transcription by complexing the HFV transactivator, Tas, preventing its direct binding to viral DNA. This physical interaction requires the N-terminal region of Tas and the RING finger of PML, but does not necessitate PML localization in NBs. Finally, we show that IFN treatment inhibits HFV replication in wild-type but not in PML–/– cells. These findings point to a role for PML in transcriptional repression and suggest that PML could play a key role in mediating an IFN-induced antiviral state against a complex retrovirus

SUMOylation Promotes PML Degradation during Encephalomyocarditis Virus Infection▿

The promyelocytic leukemia (PML) protein is expressed in the diffuse nuclear fraction of the nucleoplasm and in matrix-associated structures, known as nuclear bodies (NBs). PML NB formation requires the covalent modification of PML to SUMO. The noncovalent interactions of SUMO with PML based on the identification of a SUMO-interacting motif within PML seem to be required for further recruitment within PML NBs of SUMOylated proteins. RNA viruses whose replication takes place in the cytoplasm and is inhibited by PML have developed various strategies to counteract the antiviral defense mediated by PML NBs. We show here that primary fibroblasts derived from PML knockout mice are more sensitive to infection with encephalomyocarditis virus (EMCV), suggesting that the absence of PML results in an increase in EMCV replication. Also, we found that EMCV induces a decrease in PML protein levels both in interferon-treated cells and in PMLIII-expressing cells. Reduction of PML was carried out by the EMCV 3C protease. Indeed, at early times postinfection, EMCV induced PML transfer from the nucleoplasm to the nuclear matrix and PML conjugation to SUMO-1, SUMO-2, and SUMO-3, leading to an increase in PML body size where the viral protease 3C and the proteasome component were found colocalizing with PML within the NBs. This process was followed by PML degradation occurring in a proteasome- and SUMO-dependent manner and did not involve the SUMO-interacting motif of PML. Together, these findings reveal a new mechanism evolved by EMCV to antagonize the PML pathway in the interferon-induced antiviral defense

A Proteomic Approach Reveals That miR-423-5p Modulates Glucidic and Amino Acid Metabolism in Prostate Cancer Cells

Recently, we have demonstrated that miR-423-5p modulates the growth and metastases of prostate cancer (PCa) cells both in vitro and in vivo. Here, we have studied the effects of miR-423-5p on the proteomic profile in order to identify its intracellular targets and the affected pathways. Applying a quantitative proteomic approach, we analyzed the effects on the protein expression profile of miR-423-5p-transduced PCa cells. Moreover, a computational analysis of predicted targets of miR-423-5p was carried out by using several target prediction tools. Proteomic analysis showed that 63 proteins were differentially expressed in miR-423-5-p-transfected LNCaP cells if compared to controls. Pathway enrichment analysis revealed that stable overexpression of miR-423-5p in LNCaP PCa cells induced inhibition of glycolysis and the metabolism of several amino acids and a parallel downregulation of proteins involved in transcription and hypoxia, the immune response through Th17-derived cytokines, inflammation via amphorin signaling, and ion transport. Moreover, upregulated proteins were related to the S phase of cell cycle, chromatin modifications, apoptosis, blood coagulation, and calcium transport. We identified seven proteins commonly represented in miR-423-5p targets and differentially expressed proteins (DEPs) and analyzed their expression and influence on the survival of PCa patients from publicly accessible datasets. Overall, our findings suggest that miR-423-5p induces alterations in glucose and amino acid metabolism in PCa cells paralleled by modulation of several tumor-associated processes