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We have studied the effect of glutamine deprivation on the expression of genes encoding for ubiquitin specific peptidases (USP) and ubiquitin activating enzyme E1-like protein/autophagy related 7 (GSA7/ATG7) in U87 glioma cells in relation to inhibition of inositol requiring enzyme-1 (IRE1). It was shown that exposure of control glioma cells (transfected by empty vector) upon glutamine deprivation led to suppression of USP1 and ATG7 mRNA expression and up-regulated USP25 mRNA. At the same time, glutamine deprivation did not significantly change USP4, USP10, USP14, and USP22 gene expressions in these cells. Inhibition of ІRE1 signaling enzyme function in U87 glioma cells increased effect of glutamine deprivation on the expression of USP1 gene and introduced sensitivity of USP4 and USP14 genes to this condition. Therefore, glutamine deprivation affected the expression level of most studied genes in gene specific manner in relation to the functional activity of IRE1 enzyme, a central mediator of endoplasmic reticulum stress, which controls cell proliferation and tumor growth.

Objective. The aim of the present study was to examine the effect of inhibition of endoplasmic reticulum stress signaling, mediated by IRE1 (inositol requiring enzyme 1), which is a central mediator of the unfolded protein response on the expression of genes encoded estrogen related proteins (NRIP1/RIP140, TRIM16/EBBP, ESRRA/NR3B1, FAM162A/E2IG5, PGRMC2/PMBP, and SLC39A6/LIV-1) and their hypoxic regulation in U87 glioma cells for evaluation of their possible significance in the control of glioma cells proliferation. Methods. The expression of NRIP1, EBBP, ESRRA, E2IG5, PGRMC2, and SLC39A6 genes in U87 glioma cells, transfected by empty vector pcDNA3.1 (control) and cells without IRE1 signaling enzyme function (transfected by dnIRE1) upon hypoxia, was studied by a quantitative polymerase chain reaction. Results. Inhibition of both enzymatic activities (kinase and endoribonuclease) of IRE1 signaling enzyme function up-regulates the expression of EBBP, E2IG5, PGRMC2, and SLC39A6 genes is in U87 glioma cells in comparison with the control glioma cells, with more significant changes for E2IG5 and PGRMC2 genes. At the same time, the expression of NRIP1 and ESRRA genes is strongly down-regulated in glioma cells upon inhibition of IRE1. We also showed that hypoxia increases the expression of E2IG5, PGRMC2, and EBBP genes and decreases NRIP1 and ESRRA genes expression in control glioma cells. Furthermore, the inhibition of IRE1 in U87 glioma cells decreases the eff ect of hypoxia on the expression of E2IG5 and PGRMC2 genes, eliminates hypoxic regulation of NRIP1 gene, and enhances the sensitivity of ESRRA gene to hypoxic condition. Furthermore, the expression of SLC39A6 gene is resistant to hypoxia in both the glioma cells with and without IRE1 signaling enzyme function. Conclusions. Results of this investigation demonstrate that inhibition of IRE1 signaling enzyme function affects the expression of NRIP1, EBBP, ESRRA, E2IG5, PGRMC2, and SLC39A6 genes in U87 glioma cells in gene specific manner and these changes possibly contribute to the suppression of the cell proliferation. Most of these genes are regulated by hypoxia and preferentially through IRE1 signaling pathway of endoplasmic reticulum stress.

Objective. The aim of the present study was to investigate the effect of hypoxia on the expression of genes encoding insulin-like growth factors (IGF1 and IGF2), their receptor (IGF1R), binding protein-4 (IGFBP4), and stanniocalcin 2 (STC2) in U87 glioma cells in relation to inhibition of endoplasmic reticulum stress signaling mediated by IRE1 (inositol requiring enzyme 1) for evaluation of their possible significance in the control of tumor growth. Methods. The expression of IGF1, IGF2, IGF1R, IGFBP4, and STC2 genes in U87 glioma cells transfected by empty vector pcDNA3.1 (control) and cells without IRE1 signaling enzyme function (transfected by dnIRE1) upon hypoxia was studied by qPCR. Results. The expression of IGF1 and IGF2 genes is down-regulated in glioma cells without IRE1 signaling enzyme function in comparison with the control cells. At the same time, the expression of IGF1R, IGFBP4, and STC2 genes was up-regulated in glioma cells upon inhibition of IRE1, with more significant changes for IGFBP4 and STC2 genes. We also showed that hypoxia does not change significantly the expression of IGF1, IGF2, and IGF1R genes but up-regulated IGFBP4 and STC2 genes expression in control glioma cells. Moreover, the inhibition of both enzymatic activities (kinase and endoribonuclease) of IRE1 in glioma cells does not change significantly the effect of hypoxia on the expression of IGF1, IGF1R, and IGFBP4 genes but introduces sensitivity of IGF2 gene to hypoxic condition. Thus, the expression of IGF2 gene is resistant to hypoxia only in control glioma cells and significantly down-regulated in cells without functional activity of IRE1 signaling enzyme, which is central mediator of the unfolded protein response and an important component of the tumor growth as well as metabolic diseases. Conclusions. Results of this study demonstrate that the expression of IGF1 and IGF1R genes is resistant to hypoxic condition both in control U87 glioma cells and cells without IRE1 signaling enzyme function. However, hypoxia significantly up-regulates the expression of IGFBP4 gene independently on the inhibition of IRE1 enzyme. These data show that proteins encoded by these genes are resistant to hypoxia except IGFBP4 and participate in the regulation of metabolic and proliferative processes through IRE1 signaling.

We have studied the glucose and glutamine deprivation effect on the expression of nuclear genes encoding mitochondrial proteins in U87 glioma cells in relation to inhibition of inositol requiring enzyme-1 (IRE1). It was shown that glutamine deprivation down-regulated the expression of mitochondrial (NADP+)-dependent isocitrate dehydrogenase 2 (IDH2), malic enzyme 2 (ME2), mitochondrial aspartate aminotransferase (GOT2), and subunit B of succinate dehydrogenase (SDHB) genes in control glioma cells in gene specific manner. At the same time, the expression level of malate dehydrogenase 2 (MDH2) and subunit D of succinate dehydrogenase (SDHD) genes in these cells was not changed upon glutamine deprivation. It was also shown that inhibition of ІRE1 signaling enzyme function in U87 glioma cells modified the glutamine deprivation effect on the expression of all studied genes. Furthermore, the expression of the majority of studied genes was resistant to glucose deprivation, except IDH2 and SDHB genes, which expression levels were slightly down-regulated. Inhibition of IRE1 modified the effect of glucose deprivation on ME2, SDHB, SDHD, and GOT2 genes expression. Therefore, glucose and glutamine deprivation affected the expression level of the majority of nuclear genes encoding mitochondrial proteins in relation to the functional activity of IRE1 enzyme, which is a central mediator of endoplasmic reticulum stress and controls cell proliferation and tumor growth., Целью работы было изучить влияние дефицита глюкозы и глютамина на экспрессию ядерных генов, кодирующих митохондриальные протеины, в клетках глиомы линии U87 при угнетении inositol requiring enzyme-1 — IRE1. Показано, что дефицит глютамина снижает экспрессию генов митохондриальной NADP+зависимой изоцитратдегидрогеназы 2 — IDH2, малик энзима 2 — ME2, митохондриальной аспартатаминотрансферазы GOT2 и субъединицы В сукцинатдегидрогеназы — SDHB в контрольных трансфецированных вектором без вставки клетках глиомы геноспецифически. В то же время уровень экспрессии генов малатдегидрогеназы 2 –MDH2 и субъединицы D сукцинатдегидрогеназы в этих клетках при дефиците глютамина существенно не изменяется. Установлено также, что угнетение функции сигнального энзима IRE1 в клетках глиомы линии U87 модифицирует эффект дефицита глютамина на экспрессию всех изученных генов. Экспрессия большинства исследованных генов является резистентной к дефициту глюкозы, за исключением генов IDH2 и SDHB, для которых она несколько снижается. Угнетение IRE1 в клетках глиомы линии U87 модифицирует эффект дефицита глюкозы на экспрессию генов ME2, SDHB, SDHD и GOT2. Таким образом, дефицит глюкозы и глютамина изменяет уровень экспрессии большинства ядерных генов, кодирующих митохондриальные протеины, в зависимости от функциональной активности энзима IRE1, который является центральным медиатором стресса эндоплазматического ретикулума и контролирует процессы пролиферации и роста опухолей.

We have studied the expression of genes encoding proliferation related factors and enzymes such as IL13RA2, KRT18, CD24, ING1, ING2, MYL9, BET1, TRAPPC3, ENDOG, POLG, TSFM, and MTIF2 in U87 glioma cells upon glucose and glutamine deprivation in relation to inhibition of inositol requiring enzyme 1, a central mediator of endoplasmic reticulum stress. It was shown that glutamine deprivation leads to up-regulation of the expression of BET1, MYL9, and MTIF2 genes and down-regulation of CD24, ING2, ENDOG, POLG, and TSFM genes in control (with native IRE1) glioma cells. At the same time, glucose deprivation enhances the expression of MYL9 gene only and decreases – ING1, ING2, and MTIF2 genes in control glioma cells. Thus, effect of glucose and glutamine deprivation on gene expressions in glioma cells is gene-specific. Inhibition of inositol requiring enzyme 1 by dnIRE1 significantly modifies the effect of both glutamine and glucose deprivation on the expression of most studied genes with different direction and magnitude, especially for ING2, CD24, and MTIF2 genes. Present study demonstrates that IRE1 knockdown modifies glucose and glutamine deprivation effects on the expression of proliferation related genes and possibly contributes to slower tumor growth of these glioma cells after inhibition of IRE1 signaling enzyme.

Метою роботи було вивчення впливу дефіциту глюкози на експресію генів, що кодують LONP1/PRSS15 та катепсини у клітинах гліоми лінії U87 за умов пригнічення IRE1 inositol requiring enzyme-1. Показано, що дефіцит глюкози посилював експресію генів CTSA, CTSB, CTSD, CTSK, CTSL, CTSO та LONP1, але не впливав на експресію генів CTSC, CTSF та CTSS у контрольних (трансфікованих порожнім вектором) клітинах гліоми. Пригнічення функції сигнального ензиму IRE1 у клітинах гліоми лінії U87 змінювало ефект дефіциту глюкози на експресію більшості досліджених генів: нівелювало ефект дефіциту глюкози на гени CTSA та CTSO, індукувало на гени CTSC та CTSS, зменшувало на ген CTSK і посилювало на ген CTSL. Таким чином, дефіцит глюкози змінював рівень експресії більшості досліджених генів залежно від функціональної активності ензиму IRE1, центрального медіатора стресу ендоплазматичного ретикулума, що контролює процеси проліферації та росту пухлин.Целью работы было изучение влияния дефицита глюкозы на экспрессию генов, которые кодируют LONP1/PRSS15 и катепсины в клетках глиомы линии U87 при угнетении 1IRE1 inositol requiring enzyme-1. Показано, что дефицит глюкозы усиливал экспрессию генов CTSA, CTSB, CTSD, CTSK, CTSL, CTSO и LONP1/PRSS15, но не влиял на экспрессию генов CTSC, CTSF и CTSS в контрольных (трансфецированных пустым вектором) клетках глиомы. Угнетение функции сигнального энзима IRE1 в клетках глиомы линии U87 изменяло эффект дефицита глюкозы на экспрессию большинства изученных генов: нивелировало эффект дефицита глюкозы на гены CTSA и CTSO, индуцировало на гены CTSC та CTSS, уменьшало на ген CTSK и усиливало на ген CTSL. Таким образом, дефицит глюкозы изменял уровень экспрессии большинства изученных генов в зависимости от функциональной активности энзима IRE1, центрального медиатора стресса эндоплазматического ретикулума, который контролирует процессы пролиферации и роста опухолей.To study the effect of glucose deprivation on the expression of genes encoding for LONP1/PRSS15 and cathepsins in U87 glioma cells in relation to inhibition of inositol requiring enzyme-1 (IRE1) was the aim of the research. It was shown that glucose deprivation up-regulated the expression of CTSA, CTSB, CTSD, CTSK, CTSL, CTSO, and LONP1 genes and did not change the expression of CTSC, CTSF, and CTSS genes in control glioma cells (transfected by empty vector). Inhibition of ІRE1 signaling enzyme function in U87 glioma cells modified effect of glucose deprivation on the expression of most studied genes: removed the effect of glucose deprivation on CTSA and CTSO genes, introduces on CTSC and CTSS genes, reduced on CTSK gene, and enhanced on CTSL gene. Therefore, glucose deprivation affect the expression level of most studied genes in relation to the functional activity of IRE1 enzyme, a central mediator of endoplasmic reticulum stress, which control cell proliferation and tumor growth.

We have studied the effect of hypoxia on the expression level of mRNA of the basic enzymes of pentose-phosphate cycle (G6PD, TKT, TALDO1, PGLS and RPIA) and glucose-6-phosphate isomerase (GPI) in U87 glioma cells in relation to inhibition of IRE1 (inositol requiring enzyme 1). It was shown that hypoxia leads to up-regulation of the expression of GPI and PGLS genes and to down-regulation of TALDO1 and RPIA genes in control glioma cells. Changes for GPI gene were more significant than for other genes. At the same time, inhibition of IRE1 modified the effect of hypoxia on the expression of all studied genes. In particular, it increased sensitivity to hypoxia of G6PD and TKT genes expression and suppressed the effect of hypoxia on the expression of GPI and RPIA genes. Additionally, inhibition of IRE1 eliminated hypoxic regulation of PGLS gene and did not change significantly effect of hypoxia on the expression of TALDO1 gene in glioma cells. Present study demonstrated that hypoxia, which often contributes to tumor growth, affects the expression of most studied genes and inhibition of IRE1 modified the hypoxic regulation of pentose-phosphate cycle gene expressions in a gene specific manner and thus possibly contributes to slower glioma growth, but several aspects of this regulation warrant further investigation.

Tumor necrosis factor (TNF) superfamily receptors and TNF apoptosis inducing ligands play an important role in the realization of TNF function and control tumor growth. The TNF-related pathways are controlled by endoplasmic reticulum stress signaling, which has a crucial role in the control of cell proliferation and tumor growth. Furthermore, the inhibition of IRE1 (inositol requiring enzyme-1), which is a central mediator of endoplasmic reticulum stress sand mainly responsible for cell proliferation and apoptosis, leads to suppression of tumor growth through specific changes in the expression of genes encoding transcription factors, tumor suppressors, angiogenesis and apoptosis related proteins, including TNF superfamily receptors and TNF apoptosis inducing ligands. Therefore, changes in the expression level of TNF-related genes encoding TNF superfamily receptors and apoptosis inducing ligands possibly reflect metabolic reprogramming of cancer cells upon inhibition of IRE1-mediated endoplasmic reticulum stress signaling and correlate with suppression of glioma cell proliferation.

Objective. The aim of the present investigation was to examine the effect of inhibition of endoplasmic reticulum stress signaling, mediated by IRE1 (inositol requiring enzyme 1), which is a central mediator of the unfolded protein response on the expression of genes encoding glucocorticoid receptor (NR3C1) and some related proteins (SGK1, SGK3, NCOA1, NCOA2, ARHGAP35, NNT) and their hypoxic regulation in U87 glioma cells for evaluation of their possible significance in the control of the glioma growth. Methods. The expression of NR3C1,SGK1,SGK3, NCOA1, NCOA2, ARHGAP35, and NNT genes in U87 glioma cells, transfected by empty vector pcDNA3.1 (control) and cells without IRE1 signaling enzyme function (transfected by dnIRE1) upon hypoxia, was studied by quantitative polymerase chain reaction. Results. Inhibition of IRE1 signaling enzyme function up-regulates the expression of NR3C1, SGK1, NCOA1, NCOA2, ARHGAP35, and NNT genes in U87 glioma cells in comparison with the control glioma cells, with more significant changes for NR3C1, SGK1, and NNT genes. At the same time, the expression of SGK3 gene is strongly down-regulated in glioma cells upon inhibition of IRE1. We have also shown that hypoxia increases the expression of NR3C1, SGK1, NCOA2, ARHGAP35, and NNT genes but decreases SGK3 and NCOA1 genes expression in control glioma cells. Moreover, the inhibition of both enzymatic activities (kinase and endoribonuclease) of IRE1 in U87 glioma cells enhances the eff ect of hypoxia on the expression of SGK1, SGK3, and NNT genes, but decreases the sensitivity of NR3C1 gene to hypoxic condition. Furthermore, the expression of NCOA1 gene is resistant to hypoxia in control glioma cells, but NCOA2 and ARHGAP35 genes are resistant to this condition in glioma cells without functional activity of IRE1 signaling enzyme. Conclusions. Results of this investigation demonstrate that inhibition of IRE1 signaling enzyme function affects the expression of NR3C1, SGK1, SGK3, NCOA1, NCOA2, ARHGAP35, and NNT genes in U87 glioma cells in gene specific manner and that all these genes are regulated by hypoxia preferentially through IRE1 signaling pathway of the endoplasmic reticulum stress.

Inhibition of IRE1 (inositol requiring enzyme-1), the major signaling pathway of endoplasmic reticulm stress, significantly decreases glioma cell proliferation and tumor growth. We have studied the expression of TNFα-related genes and effect of glucose deprivation on these gene expressions in U87 glioma cells over-expressing dominant-negative IRE1 defective in both kinase and endonuclease (dn-IRE1) activity of IRE1 with hopes of elucidating its contribution to IRE1 mediated glioma growth. We have demonstrated that glucose deprivation condition leads to down-regulation of the expression of TNFRSF11B, TNFRSF1A, TNFRSF10D/TRAILR4, and LITAF genes and up-regulation of TNFRSF10B/TRAILR2/DR5 gene at the mRNA level in control glioma cells. At the same time, the expression of TNFRSF21/DR6, TNFAIP1, TNFAIP3, TRADD, and CD70/TNFSF7 genes in control glioma cells is resistant to glucose deprivation condition. The inhibition of IRE1 modifies the effect of glucose deprivation on LITAF, TNFRSF21, TNFRSF11B, and TRADD gene expressions and induces sensitivity to glucose deprivation condition the expression of TNFRSF10B, TNFRSF1A, and CD70 genes. We have also demonstrated that the expression of all studied genes is affected in glioma cells by inhibition of IRE1, except TNFRSF1A gene, as compared to control glioma cells. Moreover, the changes in the expression of TNFRSF1A, TNFRSF10D/TRAILR4, and LITAF genes induced by glucose deprivation condition have opposite orientation to that induced by inhibition of IRE1. The present study demonstrates that fine-tuning of the expression of TNFα-induced proteins and TNF receptor superfamily genes, which related to cell death and proliferation, is regulated by IRE1, an effector of endoplasmic reticulum stress, as well as depends on glucose deprivation in gene specific manner. Thus, the inhibition of kinase and endoribonuclease activity of IRE1 correlates with deregulation of TNFα-induced protein genes and TNF receptor superfamily genes in gene specific manner and thus slower the tumor growth.