Glucose-6-phosphate Dehydrogenase mRNA Research Articles

Inhibition of STAT3 reverses Taxol-resistance in ovarian cancer by down-regulating G6PD expression in vitro

Ovarian cancer is the eminent gynecological malignancy and chemoresistance remains a major reason for poor in ovarian cancer patients. Taxol has been proved as the most effective chemotherapeutic agent against ovarian cancer. However development of Taxol resistance remains a major problem. Here, we report that STAT3, directly activates pentose-phosphate pathway to exert pro-oncogenic effects on Taxol resistance of ovarian cancer. In addition, we found that STAT3, p-STAT3 and glucose-6-phosphate dehydrogenase (G6PD) protein levels are upregulated in Taxol resistant cell lines compared with Taxol sensitive cell lines. Furthermore, inhibition of STAT3 decreased G6PD mRNA expression level and enhanced the sensitivity of Taxol resistant cell to Taxol. Finally, we found that STAT3 directly binds to the G6PD promoter region and promotes the expression of G6PD at transcriptional level. Taken together, our data indicate that activation of STAT3 promotes ovarian cancer cell proliferation, colony formation, and Taxol resistance via augmenting G6PD expression and pentose-phosphate metabolism flux, which provides a potential therapeutic target that may improve prognosis by decreasing G6PD expression and enhancing Taxol-sensitivity.

Effects of miR-335-5p targeting G6PD on proliferation and apoptosis of colon cancer cells

Objective: To investigate the effects of miR-335-5p targeting glucose-6-phosphate dehydrogenase (G6PD) on the proliferation and apoptosis of colon cancer cells. Methods: Normal colon cell group, blank control group, NC group and miRNA-335-5p mimic group were set up. Colonic epithelial cells (IEC) and human colon cancer cells SW480 were cultured in vitro, and the cells in the NC group and miRNA-335-5p mimic group cells were transfected. RT-qPCR was used to detect the expression levels of miR-335-5p and G6PD mRNA in each group of cells. The targeting effect of miR-335-5p on G6PD was verified by Double Luciferase Report experiment. MTT assay was used to detect cell proliferation. Flow cytometry was used to detect the apoptosis rate. The expressions of G6PD, Bax, Bcl-2 and caspase-3 were detected by Western blot. Results: Compared with normal colon cells, the relative expression levels of miR-335-5p in SW480 cells of colon cancer in the blank control group and NC group were decreased, and the relative expression level of G6PD mRNA was increased (P＜0.05); compared with the blank control group and NC group, the expression level of miR-335-5p in miR-335-5p mimic group was increased significantly, and the expression of G6PD mRNA was decreased significantly (P＜0.05). Compared with the blank control group and NC group, the proliferative activity of colon cancer SW480 cells in miR-335-5p mimic group was decreased significantly, and the apoptosis rate was increased significantly (P＜0.05). The relative activity of luciferase in miR-335-5p mimic + WT-G6PD 3 '- UTR group was lower than that in miR-335-5p NC + WT-G6PD 3' - UTR group (P＜0.05). Compared with the blank control group, the relative expression levels of G6PD and bcl-2 protein in miR-335-5p mimic group were decreased significantly, and the expression levels of Bax and caspase-3 protein were increased significantly (P＜0.05). Conclusion: MiR-335-5p may inhibit the proliferation and promote apoptosis of colon cancer cells by targeting G6PD.

Interactions of dietary carbohydrate and vitamin D3 on growth performance, insulin signaling pathway and glucose metabolism in juvenile abalone Haliotis discus hannai

A 115-day feeding trial was conducted to investigate the effect of dietary carbohydrate and vitamin D3 levels, and their interactions on growth performance, body composition, insulin signaling pathway and glucose metabolism in juvenile abalone Haliotis discus hannai (initial body weight: 2.06 ± 0.01 g). Nine experimental diets in a 3 × 3 two-factor design were formulated with different carbohydrate levels (27.5%, 32% and 36.5%) and vitamin D3 levels (0, 1000 IU/kg and 5000 IU/kg). Results showed that the highest specific growth rate (SGR) of abalone was observed in the treatment with 36.5% of dietary carbohydrate and 1000 IU/kg of vitamin D3. The serum glucose, body crude lipid and muscle glycogen contents of abalone significantly increased with increasing dietary carbohydrate levels (P < 0.05). Diet with 1000 IU/kg of vitamin D3 significantly reduced the serum glucose and body crude lipid content (P < 0.05). Significant interactions between dietary carbohydrate and vitamin D3 were observed in SGR and crude lipid content (P < 0.05). Diet with 36.5% carbohydrate up-regulated the expression of pyruvate kinase, glucose-6-phosphate dehydrogenase (G6PDH), insulin receptor (IR), insulin receptor substrate (IRS), protein kinase B (Akt), glycogen synthase and glycogen phosphorylase (PYG), whereas decreased the phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6P) and glycogen synthesis kinase-3β. Diet with 1000 IU/kg of vitamin D3 significantly up-regulated the hexokinase, IR, IRS, Akt and glucose transporter 1 mRNA levels, whereas decreased the G6PDH (P < 0.05). The interaction between dietary carbohydrate and vitamin D3 were significant on PEPCK, G6P, G6PDH and PYG mRNA levels (P < 0.05). In conclusion, dietary carbohydrates and vitamin D3 could affect glucose metabolism by regulating glycolysis, gluconeogenesis and pentose phosphate pathway in abalone. Besides, they triggered the insulin signaling pathway, and further influence glucose transport and glycogen synthesis, which could promote the utilization of carbohydrate in abalone.

MiR-206-G6PD axis regulates lipogenesis and cell growth in hepatocellular carcinoma cell.

miR-206 plays an essential role in repressing the growth of multiple cancer cells. Glucose-6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme of the pentose phosphate pathway. However, it is mostly unknown whether G6PD is associated with miR-206-mediated growth repression of hepatocellular carcinoma (HCC) cells. In this study, we found that the expression of G6PD was upregulated in HCC patients and cell lines, whereas the expression of miR-206 was negatively associated with the clinical staging criterion of primary liver cancer. Overexpression of G6PD increased lipid accumulation and promoted cell proliferation. Conversely, inhibition of G6PD expression decreased lipid accumulation and suppressed cell proliferation. Moreover, miR-206 could directly bind to G6PD mRNA 3´-UTR and downregulate G6PD level. Overexpression of G6PD significantly attenuated the miR-206 mimic-mediated suppression of lipid accumulation and cell proliferation. In summary, the results demonstrated that miR-206 could inhibit lipid accumulation and growth of HCC cells by targeting G6PD, suggesting that the miR-206-G6PD axis may be a promising target for treating HCC.

Thioredoxin-interacting protein regulates glucose metabolism and improves the intracellular redox state in bovine oocytes during in vitro maturation.

The extent of glucose metabolism during oocyte maturation is closely related to oocyte developmental potential. Thioredoxin-interacting protein (TXNIP) is an α-arrestin family protein that negatively regulates glucose uptake into cells. However, little information is available regarding the function of TXNIP in bovine oocytes. Accordingly, the present study was performed to investigate the influence of TXNIP on glucose metabolism in bovine oocytes during in vitro maturation. Pharmacological inhibition of TXNIP by azaserine enhanced glucose uptake and imparted a specific metabolic effect on glycolysis and pentose phosphate pathway (PPP). RNA interference (RNAi) was adopted to further determine the biological significance of TXNIP in regulating glucose metabolism. The maturation rate and the developmental competence of TXNIP siRNA-treated oocytes were significantly improved. Knockdown of TXNIP in bovine oocytes significantly increased glycolysis by increasing the activities of phosphofructokinase (PFK), pyruvate kinase, and lactate dehydrogenase; pyruvate and lactate production; and intracellular ATP level, as well as mitochondrial activity. Furthermore, glucose metabolism through PPP was also enhanced by TXNIP depletion, as TXNIP siRNA treatment promoted glucose-6-phosphate dehydrogenase (G6PDH) activity and NADPH content, and helped maintain a high level of glutathione and a low level of reactive oxygen species within the oocytes. Further studies revealed that inhibition of TXNIP resulted increases in glucose transporter 1 (GLUT1) expression, as well as PFK1 platelet isoform (PFKP) and G6PDH mRNA levels. These results reveal that TXNIP depletion promotes oocyte maturation by enhancing both glycolysis and the PPP. During in vitro maturation of bovine oocytes, TXNIP serves as a key regulator of glucose uptake by controlling GLUT1 expression.

High glucose-induced ubiquitination of G6PD leads to the injury of podocytes.

Oxidative stress contributes substantially to podocyte injury, which plays an important role in the development of diabetic kidney disease. The mechanism of hyperglycemia-induced oxidative stress in podocytes is not fully understood. Glucose-6-phosphate dehydrogenase (G6PD) is critical in maintaining NADPH, which is an important cofactor for the antioxidant system. Here, we hypothesized that high glucose induced ubiquitination and degradation of G6PD, which injured podocytes by reactive oxygen species (ROS) accumulation. We found that G6PD protein expression was decreased in kidneys of both diabetic patients and diabetic rodents. G6PD activity was also reduced in diabetic mice. Overexpressing G6PD reversed redox imbalance and podocyte apoptosis induced by high glucose and palmitate. Inhibition of G6PD with small interfering RNA induced podocyte apoptosis. In kidneys of G6PD-deficient mice, podocyte apoptosis was significantly increased. Interestingly, high glucose had no effect on G6PD mRNA expression. Decreased G6PD protein expression was mediated by the ubiquitin proteasome pathway. We found that the von Hippel-Lindau (VHL) protein, an E3 ubiquitin ligase subunit, directly bound to G6PD and degraded G6PD through ubiquitylating G6PD on K366 and K403. In summary, our data suggest that high glucose induces ubiquitination of G6PD by VHL E3 ubiquitin ligase, which leads to ROS accumulation and podocyte injury.-Wang, M., Hu, J., Yan, L., Yang, Y., He, M., Wu, M., Li, Q., Gong, W., Yang, Y., Wang, Y., Handy, D. E., Lu, B., Hao, C., Wang, Q., Li, Y., Hu, R., Stanton, R. C., Zhang, Z. High glucose-induced ubiquitination of G6PD leads to the injury of podocytes.

New cases of Glucose-6-Phosphate Dehydrogenase deficiency in Pulmonary Arterial Hypertension.

Pulmonary Arterial Hypertension (PAH) is a fatal disorder with limited treatment options and reduced life expectancy after diagnosis. Complex genetic backgrounds in PAH complicates identification of causative mutations that is essential for an understanding of the disease diagnostics and etiology especially for idiopathic PAH (iPAH). Hemolysis has been implicated as contributing to the pathobiology of PAH. Glucose-6-Phosphate Dehydrogenase (G6PD) expression and activity define erythrocyte’s antioxidant capacity, and its decrease contributes to erythrocyte fragility. As G6PD deficiency was previously reported in a limited number of PAH cases, we tested whether iPAH patients exhibit underlying G6PD alterations in erythrocytes. A cohort of 22 PAH patients and 8 non-PAH patients were recruited for this study. DNA isolated from Peripheral Blood Mononuclear Cells (PBMC) was used for detection of mutations in the coding region of the G6PD gene. RNA isolated from PBMC was used for determination of G6PD mRNA expression level. G6PD activity was measured in Red Blood Cell (RBC) pellets. Three patients had missense mutations in G6PD (Val291Met, Asn126Asp, Asp194Glu), however, only one mutation (Val291Met) results in a severe G6PD deficiency. A single patient with mutation (Asn126Asp) showed a 21% decrease in G6PD activity, two subjects showed G6PD deficiency without mutations, and one patient had a decreased level of G6PD mRNA and reduced enzyme levels. This study demonstrates that a moderate decrease in G6PD activity is associated with PAH. Screening for G6PD activity and mutations in the G6PD gene may provide early detection of individuals predisposed to PAH.

Replacing fish oil with palm oil: Effects onmRNAexpression of fatty acid transport genes and signalling factors related to lipid metabolism in Nile tilapia (Oreochromis niloticus)

This study evaluated the effects of replacing fish oil (FO) with palm oil (PO) on enzyme activities and mRNA expression of lipid transport genes and signalling factors in juvenile Nile tilapia. Nile tilapia (9.34 ± 0.14 g) was fed five experimental diets with FO supplemented with PO at 0%, 25%, 50%, 75% and 100%. Liver was sampled from five fish per tank for analysis of fatty acids, enzyme activities and mRNA expression. Glucose 6‐phosphate dehydrogenase (G6PD) was highly expressed in groups fed higher levels of dietary PO, whilst liver X receptor (LXR) was highly expressed in groups fed lower levels of dietary PO. Groups fed 50% PO, 75% PO and 100% PO had significantly higher levels of G6PD mRNA expression whilst group fed 100% PO had significantly higher level of lipoprotein lipase (LPL) mRNA expression. Groups fed 75% PO and 100% PO recorded higher levels of PPAR‐α mRNA expression whilst higher level of malic enzyme mRNA expression was observed in group fed 75% PO. The mRNA expressions of the above stated genes and enzymes activities are predominantly influenced by dietary n‐3 PUFA and n‐6 PUFA levels. Dietary PO inclusion affected enzyme activities of LXR, PPAR‐α,PPAR‐β, LPL and FABP‐3. Activities of PPAR‐α, PPAR‐β and FABP‐3 were increased by PO inclusion whilst LXR and ELOVL 5 were reduced by PO inclusion. In conclusion, it could be inferred that substituting FO with PO could alter the metabolism pathway of genes such as LXR, G6PD, PPAR‐α, LPL and ME that are involved in the transport of fatty acids.

Protective Role of L-Cysteine Against High Glucose Induces G6PD-Deficiency and Endothelial Dysfunction

African Americans have high incidences of diabetes and cardiovascular disease, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. G6PD supplies NADPH, which recycles GSSG to GSH. Clinical studies demonstrate that lower blood GSH/G6PD correlate with excess oxidative stress with vascular inflammation markers which contribute to the development of complications in diabetic patients. However, the contribution of high glucose (HG) on G6PD deficiency to endothelial activation/dysfunction and monocyte recruitment, a forerunner of atherosclerosis, remains unknown. G6PD-normal and G6PD-deficient HUVEC and monocytic cells were silenced with control or G6PD siRNA (100nM) for 24 h, followed by exposure with normal glucose (5.5mM) or HG (25mM) or glutathione precursor L-Cysteine (LC; 300µM) in basal medium for 6 h. HG reduced the G6PD mRNA and its activity along with GSH in both G6PD-normal and G6PD-deficient endothelial and monocytic cells. Conversely, mRNA levels of iNOS, NOX4, and its activity were significantly upregulated but eNOS and nitrate levels were remarkably decreased under HG treated G6PD-deficient cells compared to G6PD-normal cells. The expression of cell adhesion molecules (CAMs) ICAM-1 and VCAM-1 mRNA levels significantly increased in HG-treated G6PD-deficient cells compared to G6PD-normal cells. Elevated MCP-1 was found in G6PD-deficient cells under HG conditions. Enhanced adherence of monocytes to HUVEC was observed in HG-treated G6PD-deficient cells (15.13%; p&amp;lt;0.005) compared to control cells (10%; ns). LC supplementation significantly increased the G6PD activity, GSH, and decreased CAMs reduced adherence to control level. These findings demonstrate that high glucose induces and fuels a GSH/G6PD-deficient phenotype to impair endothelial function; LC supplementation improves vascular reactivity by restoring GSH/G6PD levels. Disclosure R. Parsanathan: None. S.K. Jain: None.

MRNA Expression of SLC5A5 and SLC2A Family Genes in Papillary Thyroid Cancer: An Analysis of The Cancer Genome Atlas.

PurposeThe present study investigated the dynamics and prognostic role of messenger RNA (mRNA) expression responsible for 18F-fluorodeoxyglucose (FDG) uptake in FDG positron emission tomography (PET) and radioactive iodine (131I) uptake in whole-body radioactive iodine scans (WBS) in papillary thyroid cancer (PTC) patients.Materials and MethodsThe primary and processed data were downloaded from the Genomic Data Commons Data Portal. Expression data for sodium/iodide symporter (solute carrier family 5 member 5, SLC5A5), hexokinase (HK1–3), glucose-6-phosphate dehydrogenase (G6PD), and glucose transporter (solute carrier family 2, SLC2A1–4) mRNA were collected.ResultsExpression of SLC5A5 mRNA were negatively correlated with SLC2A1 mRNA and positively correlated with SLC2A4 mRNA. In PTC with BRAF mutations, expressions of SLC2A1, SLC2A3, HK2, and HK3 mRNA were higher than those in PTC without BRAF mutations. Expression of SLC5A5, SLC2A4, HK1, and G6PD mRNA was lower in PTC without BRAF mutation. PTCs with higher expression of SLC5A5 mRNA had more favorable disease-free survival, but no association with overall survival.ConclusionExpression of SLC5A5 mRNA was negatively correlated with SLC2A1 mRNA. This finding provides a molecular basis for the management of PTC with negative WBS using 18F-FDG PET scans. In addition, higher expression of SLC5A5 mRNA was associated with less PTC recurrence, but not with deaths.

G6PD plays a neuroprotective role in brain ischemia through promoting pentose phosphate pathway

TIGAR-regulated pentose phosphate pathway (PPP) plays a critical role in the neuronal survival during cerebral ischemia/reperfusion. Glucose-6-phosphate dehydrogenase (G6PD) is a rate-limiting enzyme in PPP and thus, we hypothesized that it plays an essential role in anti-oxidative defense through producing NADPH. The present study investigated the regulation and the role of G6PD in ischemia/reperfusion-induced neuronal injury with in vivo and in vitro models of ischemic stroke. The results showed that the levels of G6PD mRNA and protein were increased after ischemia/reperfusion. In vivo, lentivirus-mediated G6PD overexpression in mice markedly reduced neuronal damage after ischemia/reperfusion insult, while lentivirus-mediated G6PD knockdown exacerbated it. In vitro, overexpression of G6PD in cultured primary neurons decreased neuronal injury under oxygen and glucose deprivation/reoxygenation (OGD/R) condition, whereas knockdown of G6PD aggravated it. Overexpression of G6PD increased levels of NADPH and reduced form of glutathione (rGSH), and ameliorated ROS-induced macromolecular damage. On the contrary, knockdown of G6PD executed the opposite effects in mice and in primary neurons. Supplementation of exogenous NADPH alleviated the detrimental effects of G6PD knockdown, whereas further enhanced the beneficial effects of G6PD overexpression in ischemic injury. Therefore, our results suggest that G6PD protects ischemic brain injury through increasing PPP. Thus G6PD may be considered as potential therapeutic target for treatment of ischemic brain injury.

Overexpression of G6PD Represents a Potential Prognostic Factor in Clear Cell Renal Cell Carcinoma.

Glucose-6-phosphate dehydrogenase (G6PD) participates in glucose metabolism and it acts as the rate-limiting enzyme of the pentose phosphate pathway (PPP). Recently, G6PD dysregulation has been found in a variety of human cancers. Through analyzing published data in The Cancer Genome Atlas (TCGA), our pilot study indicated that G6PD mRNA expression was significantly higher in advanced Fuhrman grade in clear cell renal cell carcinoma (ccRCC). These clues promoted us to further evaluate the expression profile of G6PD and its prognostic impact in patients with ccRCC. In this study, G6PD expression levels were analyzed in 149 human ccRCC and normal tissues using immunohistochemistry. The results showed that compared with that in the normal renal samples, G6PD was found highly expressed in 51.0% of ccRCC (p<0.05). High expression of G6PD was significantly correlated to tumor extent, lymph node metastasis, Fuhrman grade, and TNM stage of ccRCC (all p<0.05). Moreover, positive G6PD expression was associated with poorer overall survival in ccRCC (p<0.001). In Cox regression analyses, high expression of G6PD also could be an independent prognostic factor for overall survival in ccRCC (p=0.007). This study suggests that overexpression of G6PD is associated with advanced disease status and therefore may become an important prognosticator for poor outcomes in ccRCC, as well as a potential therapeutic target for developing effective treatment modalities.

Gene promoter methylation in glucose-6-phosphate dehydrogenase deficiency

To investigate the features of methylation in the promoter region of glucose-6-phosphate dehydrogenase (G6PD) gene and the association between gene promoter methylation and G6PD deficiency. Fluorescent quantitative PCR was used to measure the mRNA expression of G6PD in 130 children with G6PD deficiency. Sixty-five children without G6PD deficiency served as the control group. The methylation-sensitive high-resolution melting curve analysis and bisulfite PCR sequencing were used to analyze gene promoter methylation in 22 children with G6PD deficiency and low G6PD mRNA expression. The G6PD gene promoter methylation was analyzed in 44 girls with normal G6PD mRNA expression (7 from G6PD deficiency group and 37 from control group). Twenty-two (16.9%) children with G6PD deficiency had relatively low mRNA expression of G6PD; among whom, 16 boys showed no methylation, and 6 girls showed partial methylation. Among the 44 girls with normal G6PD mRNA expression, 40 showed partial methylation, and 4 showed no methylation (1 case in the G6PD group and 3 cases in the control group). Gene promoter methylation is not associated with G6PD deficiency in boys. Girls have partial methylation or no methylation in the G6PD gene, suggesting that the methylation may be related to G6PD deficiency in girls.

Histone deacetylase inhibitor-induced cancer stem cells exhibit high pentose phosphate pathway metabolism

PurposeWe recently demonstrated that histone deacetylase (HDAC) inhibitors can “reprogram” differentiated triple-negative breast cancer cells to become quiescent stem-like cancer cells. We hypothesized that the metabolic state of such cells differs from that of their differentiated progeny.ResultsIn untreated cells, glucose uptake was higher in ALDH+ cells than in ALDH− cells (p = 0.01) but lactate production was not different; treating ALDH− or ALDH+ cells with VA or SAHA similarly increased glucose uptake without changing lactate production but upregulated G6PD, a rate-limiting enzyme in pentose phosphate pathway metabolism. NADPH production was higher in HDAC inhibitor-treated stem-like cells than in vehicle-treated cells (p < 0.05). Two G6PD inhibitors, 6-aminonicotinamide and dehydroepiandrosterone, decreased mammosphere formation efficiency and ALDH activity and 6-aminonicotinamide reduced the VA-induced increase in ALDH+ cells. Finally, patients expressing high G6PD mRNA had significantly worse overall survival (p < 0.001), and patients with high G6PD protein showed a similar trend towards worse disease-specific survival (p = 0.06).MethodsGlucose consumption, lactate and NADPH production, and reactive oxygen species generation were compared in aldehyde dehydrogenase (ALDH)-positive and –negative cells in the presence or absence of the HDAC inhibitors valproic acid (VA) or suberoylanilide hydroxamic acid (SAHA). Glucose-6-phosphate dehydrogenase (G6PD) expression was evaluated in a tissue microarray from 94 patients with node-positive invasive breast carcinoma and in two publically available databases and correlated with overall survival.ConclusionsEnergy metabolism in HDAC inhibitor-induced stem-like cancer cells differed sharply from that of differentiated cell types. HDAC inhibitor-induced dedifferentiation promoted metabolic reprogramming into the pentose phosphate pathway, which is targeted effectively by G6PD inhibition. These findings highlight a potential dual-therapy approach to targeting bulk differentiated cells with HDAC inhibitors and CSCs with G6PD inhibitors.

Phosphofructokinase and glucose-6-phosphate dehydrogenase in response to drought and bicarbonate stress at transcriptional and functional levels in mulberry

Drought and bicarbonate stress are the most common abiotic stresses limiting plant growth and crop production all over the world. Glycolytic and pentose phosphate pathways have important effects on the resistance response of plants to abiotic stress. Phosphofructokinase (PFK) and glucose-6-phosphate dehydrogenase (G6PDH) are the rate limiting enzymes of the two pathways which control carbon flow through the two pathways, respectively. In Morus alba L. leaves, the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the proline content increased under drought and bicarbonate stress at first, and then decreased. At the functional level, drought and bicarbonate stress exert an activating effect on the G6PDH activity and an inhibitory effect on the PFK activity in M. alba leaves. At the transcriptional level ATP-PFK, PPi-PFK and G6PDH genes showed no significant change under 80 g/L PEG 6000 treatment. The changes were observed at the ATP-PFK, PPi-PFK and G6PDH mRNA levels under 30 mM NaHCO3 treatment. Although M. alba stopped growing under two different treatments and the changes of G6PDH and PFK are different suggesting that may be additional factors playing important roles in glucose and energy metabolism in plant responses to stresses.

Glucose-6-phosphate dehydrogenase expression is correlated with poor clinical prognosis in esophageal squamous cell carcinoma

Increasing evidence has demonstrated that glucose-6-phosphate dehydrogenase (G6PD), a key metabolic enzyme, participating in pentose phosphate pathway (PPP), is tightly associated with development and progression of a variety of tumors. Here, we reported expression of G6PD and its association with the prognosis of the patients with esophageal squamous cell carcinoma (ESCC). The results revealed significantly elevated G6PD mRNA and protein expressions in ESCC tissues compared with normal tissues (P < 0.05). Furthermore, high G6PD expression was tightly associated with histological grade, TNM staging and lymph node metastasis (P < 0.05), but not related to the patients' age and gender (P > 0.05). Importantly, the survival time of G6PD-positive patients was markedly lower than that of G6PD-negative patients (P < 0.05). Most notably, Cox multivariate assay demonstrated that G6PD was an independent prognostic factor for the patients with ESCC. In conclusion, G6PD may be a novel predictor for the prognosis of the patients with ESCC.

G6PD downregulation triggered growth inhibition and induced apoptosis by regulating STAT3 signaling pathway in esophageal squamous cell carcinoma.

There is growing evidence that glucose-6-phosphate dehydrogenase (G6PD) is tightly associated with development and progression of many human tumors. However, its precise molecular mechanisms in esophageal squamous cell carcinoma (ESCC) remain unknown. In the current study, we found that G6PD messenger RNA (mRNA) and protein levels in ESCC cell lines (Eca109, EC1, and EC9706 cells) were significantly higher than that in normal esophageal epithelial cell line Het-1A (P < 0.05) and specific small interfering RNA (siRNA) against G6PD significantly reduced the levels of G6PD mRNA and protein in EC1 cells with highest G6PD levels (P < 0.05). Further investigation revealed that G6PD depletion contributed to the growth suppression in EC1 cells in vitro and EC1 cells xenografted nude mice in vivo, which was associated with the reduces of tumor weight and Ki-67 proliferation index, triggered cell cycle arrest at G0/G1 phase coupled with obvious decreases of cyclin D1 and CDK4 protein levels, and induced cell apoptosis accompanied by the increases of caspase-3 activity and Bax protein expression as well as the decrease of Bcl-2 protein expression in EC1 cells. More importantly, G6PD depletion significantly reduced the level of p-STAT3 protein but did not alter total STAT3 protein level. Taken altogether, our data presented herein suggest that G6PD may function as an important regulator in development and progression of ESCC by manipulating STAT3 signaling pathway and thus may be an underlying molecular target for therapy of the patients with ESCC.

Cortisol 유발 세포독성에 대한 아연 관련 항산화 유전자 발현 증가에 의한 세포보호 효과

The protective effect of zinc against cortisol-induced cell injury was examined in rainbow trout gill epithelial cells. Cells exposed to cortisol for 24 h showed increased leakage of lactate dehydrogenase (LDH) as well as decreased cell viability in a dose-dependent manner. Treatment with zinc (100 μM ZnSO₄) reduced the severity of both LDH release and cell death as well as protected cells against cortisol-induced caspase-3 activation, indicating reduction of apoptosis. Cortisol-induced cell death, leakage of LDH, and caspase-3 activation were blocked by the glucocorticoid receptor antagonist Mifepristone (RU-486), suggesting that cell injury was cortisol-dependent. In addition, we studied the effect of zinc on the expression of antioxidant genes such as metallothionein A (MTA), metallothionein B (MTB), glutathione-S-transferase (GST), and glucose-6-phosphate dehydrogenase (G6PD) during cortisol-induced cell injury. MTA, MTB, GST, and G6PD mRNA levels increased after treatment with zinc or cortisol, separately or in combination. Higher mRNA levels of MTA, MTB, GST, and G6PD were detected when cells were treated with 100 μM ZnSO₄ and 1 μM cortisol in combination at the same time compared to treatment with zinc or cortisol separately. Cells treated with zinc showed increased intracellular free zinc concentrations, and this response was significantly enhanced in cells treated with cortisol and zinc. In conclusion, zinc treatment inhibited cortisol-induced cytotoxicity and apoptosis through indirect antioxidant action.

Starvation actively inhibits splicing of glucose-6-phosphate dehydrogenase mRNA via a bifunctional ESE/ESS element bound by hnRNP K

Regulated expression of glucose-6-phosphate dehydrogenase (G6PD) is due to changes in the rate of pre-mRNA splicing and not changes in its transcription. Starvation alters pre-mRNA splicing by decreasing the rate of intron removal, leading to intron retention and a decrease in the accumulation of mature mRNA. A regulatory element within exon 12 of G6PD pre-mRNA controls splicing efficiency. Starvation caused an increase in the expression of heterogeneous nuclear ribonucleoprotein (hnRNP) K protein and this increase coincided with the increase in the binding of hnRNP K to the regulatory element and a decrease in the expression of G6PD mRNA. HnRNP K bound to two C-rich motifs forming an ESS within exon 12. Overexpression of hnRNP K decreased the splicing and expression of G6PD mRNA, while siRNA-mediated depletion of hnRNP K caused an increase in the splicing and expression of G6PD mRNA. Binding of hnRNP K to the regulatory element was enhanced in vivo by starvation coinciding with a decrease in G6PD mRNA. HnRNP K binding to the C-rich motifs blocked binding of serine-arginine rich, splicing factor 3 (SRSF3), a splicing enhancer. Thus hnRNP K is a nutrient regulated splicing factor responsible for the inhibition of the splicing of G6PD during starvation.

3′-UTR variations and G6PD deficiency

The combination of two silent mutations, c.1311C>T in exon 11 and IVS11 T93C (glucose-6-phosphate dehydrogenase (G6PD) 1311T/93C), with unknown mechanism, have been reported in G6PD-deficient individuals in Asian populations including Malaysian aboriginal group, Negrito. Here, we report the screening of G6PD gene in 103 Negrito volunteers using denaturing high-performance liquid chromatography (dHPLC) and direct sequencing. A total of 48 individuals (46.6%) were G6PD deficient, 83.3% of these carried G6PD 1311T/93C with enzyme activity ranging from 1.8 to 4.8 U gHb(-1). Three novel single-nucleotide polymorphisms (SNPs), rs112950723, rs111485003 and rs1050757, were found in the G6PD 3'-untranslated region (UTR). Strong association was observed between haplotype 1311T/93C and rs1050757G, which is located inside the 35 bp AG-rich region. In silico analysis revealed that the transition of A to G at position rs1050757 makes significant changes in the G6PD mRNA secondary structure. Moreover, putative micro (mi)RNA target sites were identified in 3'-UTR of G6PD gene, two of these in the region encompassing rs1050757. It could be speculated that rs1050757 have a potential functional effect on the downregulation of mRNA and consequently G6PD deficiency either by affecting mRNA stability and translation or mirRNA regulation process. This is the first report of biochemical association of an SNP in 3'-UTR of G6PD gene and the possible role of mRNA secondary structure.