Study on the role of TIGAR in regulating mitochondrial function and inhibiting pyroptosis of breast cancer cells.

Mitochondrial oxidative phosphorylation (OXPHOS) has been exploited as a therapeutic target in cancer treatments because of its crucial role in tumorigenesis. CR6-interacting factor 1 (CRIF1), a mitochondrial ribosomal subunit protein, is essential for the regulation of mitochondrial OXPHOS capacity. However, the mechanism of CRIF1 in triple-negative breast cancer (TNBC) cells remains unclear. We showed that the downregulation of CRIF1 reduced cell proliferation in the TNBC cell lines MDA-MB-468, MDA-MB-231, and, especially, BT549. In addition, wound scratch and Transwell assays showed that CRIF1 deficiency inhibited the migration and invasion of BT549 cells. CRIF1 downregulation resulted in the suppression of mitochondrial bioenergetics in BT549 cells, specifically affecting the inhibition of OXPHOS complexes I and II. This was evidenced by a decrease in the mitochondrial oxygen consumption rate and the depolarization of the mitochondrial membrane potential. Damage to mitochondria resulted in a lower adenosine triphosphate level and an elevated production of mitochondrial reactive oxygen species. In addition, CRIF1 deficiency decreased hypoxia-inducible factor 1α accumulation, NADPH synthesis, and TP53-induced glycolysis and apoptosis regulator (TIGAR) expression in BT549 cells. These events contributed to G0/G1-phase cell cycle inhibition and the upregulation of the cell cycle protein markers p53, p21, and p16. Transfection with a TIGAR overexpression plasmid reversed these effects and prevented CRIF1 downregulation-induced proliferation and migration reduction. These results indicate that blocking mitochondrial OXPHOS synthesis via CRIF1 may have a therapeutic antitumor effect in BT549 TNBC cells.

TIGAR (TP53-induced glycolysis and apoptosis regulator) functions to promote antioxidant defence, with a loss of TIGAR associated with a defect in a cell’s ability to control reactive oxygen species (ROS) and resultant oxidative damage. TIGAR can function as a fructose-2,6-bisphosphatase, lowering the levels of fructose-2,6- bisphosphate, which is an activator of phosphofructokinase-1. As a consequence, TIGAR activity results in a dampening of the glycolytic pathway and, by enhancing the pentose phosphate pathway, increases cellular antioxidant capacity by promoting the generation of NADPH and GSH. Although TIGAR is clearly a transcriptional target of the tumour suppressor p53 in human cells, the activation of TIGAR expression in mouse cells in vitro and in a mouse model of intestinal regeneration was not dependent on p53 or its family member TAp73. However, TIGAR expression was strongly induced in the mouse intestine during proliferation following damage or APC loss, suggesting a role for the Wnt signalling pathway. The increase in TIGAR expression seen in response to APC loss was lost after simultaneous deletion of c-Myc, suggesting that TIGAR responds to c-Myc activation downstream of the Wnt signalling pathway. While TIGAR may be a direct Myc target, Myc was shown to induce ROS, which were also found to regulate the expression of TIGAR. In order to further understand the function of TIGAR, a TIGAR-deficient mouse was generated and TIGAR was found to play a role in supporting intestinal regeneration by lowering oxidative stress in the small intestinal crypts following tissue damage by irradiation or cisplatin treatment. Moreover, TIGAR-null mice showed decreased tumour development in a model of intestinal adenoma. In particular, it was found that TIGAR acts to lower the damaging pool of ROS during oxidative stress. Through this, TIGAR can function to promote tumourigenesis and elevated TIGAR expression has been observed in various cancer types, independently of p53 status. This suggests that a deregulated expression of TIGAR may play a role in supporting rather than inhibiting cancer development. This study reveals p53-independent mechanisms by which TIGAR is regulated and how TIGAR can contribute to promote cell growth and tumourigenesis.

The gene encoding TIGAR (Tp53-induced glycolysis and apoptosis regulator) was identified in a screen for genes whose expression was increased by p53. Bensaad et al . now show that TIGAR plays a role in protecting cells from apoptosis by directing cellular metabolism from the glycolytic pathway to the pentose phosphate pathway (PPP), which decreases reactive oxygen species (ROS) by producing increased NADPH, which is required to increase the abundance of reduced glutathione. Based on the time course of p53-induced expression and its activation by a p53 mutant that fails to stimulate some proapoptotic target genes, the gene encoding TIGAR appears to fall into the class of genes regulated by p53 that promote cell survival under conditions of moderate stress. TIGAR exhibits sequence similarity, especially with regard to conserved catalytic residues, with the bisphosphatase domain of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2), a bifunctional enzyme involved in regulation of glycolysis. Consistent with TIGAR having fructose-2,6-bisphosphatase activity, fructose-2,6-bisphophate (Fru-2,6-P 2 ) concentration was decreased in cells overexpressing TIGAR and was increased in cells in which TIGAR was decreased by siRNA. Fru-2,6-P 2 stimulates glycolysis, and cells overexpressing TIGAR showed decreased glycolytic rates and cells treated with TIGAR siRNA showed increased glycolytic rates. When glycolysis is inhibited, fructose-6-phosphate is converted to glucose-6-phosphate and shunted into the PPP, which can inhibit apoptosis by increasing the abundance of the ROS scavenger glutathione. In various apoptosis-stimulating conditions that proceeded through mechanisms involving ROS, TIGAR overexpression decreased cell death. TIGAR was not effective at preventing cell death induced by stimuli that did not increase ROS. TIGAR also did not protect cells from apoptosis if the PPP was blocked. Although enzymatic activity of TIGAR was not directly demonstrated, protection from ROS-sensitive apoptosis, decreased glycolytic rate, and lower intracellular Fru-2,6-P 2 concentrations were not observed in cells overexpressing TIGAR with mutations in the putative catalytic conserved residues. These results connect p53 to cellular metabolism and provide insight into how p53 can contribute to DNA repair and cell survival by increasing flux through the PPP, which decreases ROS and increases the production of metabolites necessary for DNA repair (see Green and Chipuk). K. Bensaad, A. Tsuruta, M. A. Selak, M. N. C. Vidal, K. Nakano, R. Bartrons, E. Gottlieb, K. H. Vousden, TIGAR, a p53-inducible regulator of glycolysis and apoptosis. Cell 126 , 107-120 (2006). [Online Journal] D. R. Green, J. E. Chipuk, p53 and metabolism: Inside the TIGAR. Cell 126 , 30-32 (2006). [Online Journal]

Yamanaka R, Hoshino A, Fukai K, Urata R, Minami Y, Honda S, Fushimura Y, Hato D, Iwai-Kanai E, Matoba S. TIGAR reduces smooth muscle cell autophagy to prevent pulmonary hypertension. Am J Physiol Heart Circ Physiol 319: H1087-H1096, 2020. First published September 18, 2020; doi:10.1152/ajpheart.00314.2020.-Pulmonary arterial hypertension (PAH) is a refractory disease. Its prognosis remains poor; hence, establishment of novel therapeutic targets is urgent. TP53-induced glycolysis and apoptosis regulator (TIGAR) is a downstream target of p53 and exhibits functions inhibiting autophagy and reactive oxygen species (ROS). Recently, p53 was shown to suppress PAH progression. Because inhibition of autophagy and ROS is known to improve PAH, we examined the effect of TIGAR on PAH progression. We compared pulmonary hypertension (PH) development between TIGAR-deficient knockout (KO) and wild-type (WT) mice using a hypoxia-induced PH model. Human pulmonary artery smooth muscle cells (PASMCs) were used for in vitro experiments with small interfering RNA (siRNA) to investigate the possible molecular mechanisms. From the analysis of right ventricular pressure, right ventricular weight, and mortality rate, we concluded that the hypoxia-induced PH development was remarkably higher in TIGAR KO than in WT mice. Pathological investigation revealed that medial thickening of the pulmonary arterioles and cell proliferation were increased in TIGAR KO mice. Autophagy and ROS activity were also increased in TIGAR KO mice. TIGAR knockdown by siRNA increased cell proliferation and migration, exacerbated autophagy, and increased ROS generation during hypoxia. Autophagy inhibition by chloroquine and ROS inhibition by N-acetylcysteine attenuated the proliferation and migration of PASMCs caused by TIGAR knockdown and hypoxia exposure. TIGAR suppressed the proliferation and migration of PASMCs via inhibiting autophagy and ROS and, therefore, improved hypoxia-induced PH. Thus, TIGAR might be a promising therapeutic target for PAH.NEW & NOTEWORTHY Pulmonary arterial hypertension is a refractory disease. TP53-induced glycolysis and apoptosis regulator (TIGAR) is a downstream target of p53 and exhibits functions inhibiting autophagy and reactive oxygen species (ROS). By using TIGAR-deficient knockout mice and human pulmonary artery smooth muscle cells, we found that TIGAR suppressed the proliferation and migration of PASMCs via inhibiting autophagy and ROS and, therefore, improved hypoxia-induced PH. TIGAR will be a promising therapeutic target for PAH.

Introduction: TP53-induced glycolysis and apoptosis regulator (TIGAR) is a p53 target protein that has critical roles in glycolysis and redox balance. The reports about the effect of TIGAR on prognosis and its biological role in hepatocellular carcinoma (HCC) are limited. Methods: A total of 386 patients with HCC who had undergone hepatic resection were enrolled. Immunohistochemical staining for TIGAR was performed. Additionally, the regulation of malignant activity and ferroptosis by TIGAR was investigated in vitro. Results: Patients were divided into TIGAR-positive (n = 80, 20.7%) and -negative (n = 306, 79.3%) groups. TIGAR positivity was significantly correlated with lower albumin, higher α-fetoprotein/ des-gamma-carboxyprothrombin, larger tumor size/number of tumors, and greater proportions of BCLC staging C/single nodular type/poor differentiation/microscopic vascular invasion/microscopic intrahepatic metastasis. In multivariate analysis, TIGAR positivity was an independent prognostic factor (p < 0.0001). In addition, TIGAR positivity was significantly associated with a smaller number of cluster of differentiation (CD) 8-positive T cells (p = 0.0450), larger number of CD68-positive macrophages (p = 0.0058), larger number of programmed death-ligand 1-positive cases (p = 0.0002), and larger number of vessels that encapsulate tumor cluster-positive cases (p = 0.0004). In vitro, TIGAR knockdown decreased cell motility and induced ferroptosis. TIGAR knockdown inhibited the phosphorylation of adenosine monophosphate-activated protein kinase and acetyl-CoA carboxylase. Ferroptosis induced by TIGAR knockdown was inhibited by liproxstatin and baicalein treatment. The combination of TIGAR knockdown and lenvatinib further induced ferroptosis. Conclusion: High expression of TIGAR impacted the clinical outcome of HCC patients and TIGAR was associated not only with tumor microenvironment but also with resistance to ferroptosis. Introduction: TP53-induced glycolysis and apoptosis regulator (TIGAR) is a p53 target protein that has critical roles in glycolysis and redox balance. The reports about the effect of TIGAR on prognosis and its biological role in hepatocellular carcinoma (HCC) are limited. Methods: A total of 386 patients with HCC who had undergone hepatic resection were enrolled. Immunohistochemical staining for TIGAR was performed. Additionally, the regulation of malignant activity and ferroptosis by TIGAR was investigated in vitro. Results: Patients were divided into TIGAR-positive (n = 80, 20.7%) and -negative (n = 306, 79.3%) groups. TIGAR positivity was significantly correlated with lower albumin, higher α-fetoprotein/ des-gamma-carboxyprothrombin, larger tumor size/number of tumors, and greater proportions of BCLC staging C/single nodular type/poor differentiation/microscopic vascular invasion/microscopic intrahepatic metastasis. In multivariate analysis, TIGAR positivity was an independent prognostic factor (p < 0.0001). In addition, TIGAR positivity was significantly associated with a smaller number of cluster of differentiation (CD) 8-positive T cells (p = 0.0450), larger number of CD68-positive macrophages (p = 0.0058), larger number of programmed death-ligand 1-positive cases (p = 0.0002), and larger number of vessels that encapsulate tumor cluster-positive cases (p = 0.0004). In vitro, TIGAR knockdown decreased cell motility and induced ferroptosis. TIGAR knockdown inhibited the phosphorylation of adenosine monophosphate-activated protein kinase and acetyl-CoA carboxylase. Ferroptosis induced by TIGAR knockdown was inhibited by liproxstatin and baicalein treatment. The combination of TIGAR knockdown and lenvatinib further induced ferroptosis. Conclusion: High expression of TIGAR impacted the clinical outcome of HCC patients and TIGAR was associated not only with tumor microenvironment but also with resistance to ferroptosis.

We have previously demonstrated that metabolic coupling occurs in a subgroup of human breast cancers between fibroblasts and carcinoma cells. In metabolically coupled tumors, cancer associated fibroblasts (CAFs) have low Cav-1 protein expression, are highly glycolytic and generate large amounts of lactate which is then released to the extracellular space via increased expression of monocarboxylate transporter 4 (MCT4) compared to normal fibroblasts (NFs). Conversely, in metabolically coupled tumors, carcinoma cells have low glycolysis with high uptake of lactate via monocarboxylate transporter 1 (MCT1) and high mitochondrial oxidative phosphorylation (OXPHOS) using lactate as a substrate compared to non-carcinoma epithelial cells. We have identified two fibroblast markers of metabolically coupled breast cancer: low caveolin-1 (Cav-1) protein expression and high MCT4 protein expression. Low Cav-1 expression and high MCT4 expression in breast cancer fibroblasts are prognostic biomarkers associated with poor outcomes. However, the mechanisms by which carcinoma cells reprogram CAFs to induce loss of fibroblast Cav-1 or increased expression of MCT4 protein are unknown. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is a p53 regulated protein that inhibits glycolysis and induces OXPHOS. We investigated the role of TIGAR on expression of the fibroblast prognostic biomarkers Cav-1 and MCT4. We immunohistochemically stained 10 human ER+ breast cancer samples for TIGAR. TIGAR protein expression was highest in the carcinoma cells compared to fibroblasts and non-carcinoma epithelial cells in all 10 samples. We then cocultured T47D ER+ breast cancer cells with human fibroblasts (BJ-1) and discovered that the presence of fibroblasts was sufficient to increase TIGAR protein expression in carcinoma cells (1.5 fold, p&amp;lt;0.05). This coculture system was also sufficient to downregulate Cav-1 protein expression in fibroblasts (2.3 fold, p&amp;lt;0.01). We generated fibroblasts with Cav-1 shRNA knockdown and discovered that TIGAR protein expression decreased. We generated TIGAR overexpressing T47D cells and found that they had higher OXPHOS activity. Coculture of TIGAR overexpressing T47D cells with fibroblasts induced further downregulation of Cav-1 protein in fibroblasts (3.2 fold, p&amp;lt;0.05) and increased MCT4 protein in fibroblasts (2 fold, p&amp;lt;0.05) compared to coculture with control T47D cells. Overexpression of TIGAR in T47D cells was sufficient to increase 2-deoxyglucose uptake in fibroblasts by 1.2 fold (p&amp;lt;0.01) and decrease 2-deoxyglucose uptake in T47D cells by 1.3 fold (p&amp;lt;0.05). 2-deoxyglycose uptake is a marker of glycolysis. Finally, resistance to baseline apoptosis (1.6 fold,p&amp;lt;0.001) and with tamoxifen (1.2 fold, p&amp;lt;0.01) was induced by TIGAR overexpression. In summary, TIGAR expression in carcinoma cells is sufficient to induce carcinoma cell resistance to apoptosis, decrease Cav-1 and increase MCT4 protein expression in fibroblasts. TIGAR should be studied as a prognostic and predictive biomarker in breast cancer and a potential drug target. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-01-06.

lncRNA MIR503HG inhibits cell proliferation and promotes apoptosis in TNBC cells via the miR-224-5p/HOXA9 axis

A subgroup of breast cancers has several metabolic compartments. The mechanisms by which metabolic compartmentalization develop in tumors are poorly characterized. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is a bisphosphatase that reduces glycolysis and is highly expressed in carcinoma cells in the majority of human breast cancers. Hence we set out to determine the effects of TIGAR expression on breast carcinoma and fibroblast glycolytic phenotype and tumor growth. The overexpression of this bisphosphatase in carcinoma cells induces expression of enzymes and transporters involved in the catabolism of lactate and glutamine. Carcinoma cells overexpressing TIGAR have higher oxygen consumption rates and ATP levels when exposed to glutamine, lactate, or the combination of glutamine and lactate. Coculture of TIGAR overexpressing carcinoma cells and fibroblasts compared with control cocultures induce more pronounced glycolytic differences between carcinoma and fibroblast cells. Carcinoma cells overexpressing TIGAR have reduced glucose uptake and lactate production. Conversely, fibroblasts in coculture with TIGAR overexpressing carcinoma cells induce HIF (hypoxia-inducible factor) activation with increased glucose uptake, increased 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3), and lactate dehydrogenase-A expression. We also studied the effect of this enzyme on tumor growth. TIGAR overexpression in carcinoma cells increases tumor growth in vivo with increased proliferation rates. However, a catalytically inactive variant of TIGAR did not induce tumor growth. Therefore, TIGAR expression in breast carcinoma cells promotes metabolic compartmentalization and tumor growth with a mitochondrial metabolic phenotype with lactate and glutamine catabolism. Targeting TIGAR warrants consideration as a potential therapy for breast cancer.

TIGAR mediates the inhibitory role of hypoxia on ROS production and apoptosis in rat nucleus pulposus cells.

Cancer cells adopt glycolysis to facilitate the generation of biosynthetic substrates demanded by cell proliferation and growth, and to adapt to stress conditions such as excessive reactive oxygen species (ROS) accumulation. TIGAR (TP53-induced glycolysis and apoptosis regulator) is a fructose-2,6-bisphosphatase that is regulated by p53. TIGAR functions to inhibit glycolysis and promote antioxidative activities, which assists the generation of NADPH to maintain the levels of GSH and thus reduces intracellular ROS. However, the functions of TIGAR in gastric cancer (GC) remain unclear. TIGAR expression levels were detected by immunoblotting and immunohistochemistry in gastric cancer samples, along with four established cell lines of GC. The functions of TIGAR were determined by utilizing shRNA-mediated knockdown experiments. The NADPH/NADP+ ratio, ROS, mitochondrial ATP production, and phosphorus oxygen ratios were determined in TIGAR-depleted cells. Xenograft experiment was conducted with BALB/c nude mice. TIGAR was up-regulated compared with corresponding non-cancerous tissues in primary GCs. TIGAR knockdown significantly reduced cell proliferation and increased apoptosis. TIGAR protected cancer cells from oxidative stress-caused damages, but also glycolysis defects. TIGAR also increased the production of NADPH in gastric cancer cells. TIGAR knockdown led to increased ROS production, elevated mitochondrial ATP production, and phosphorus oxygen ratios. The prognosis of high TIGAR expression patients was significantly poorer than those with low TIGAR expression. Taken together, TIGAR exhibits oncogenic features in GC, which can be evaluated as a target for intervention in the treatment of GC.

Tumor-initiating cells with reprogramming plasticity or stem-progenitor cell properties (stemness) are thought to be essential for cancer development and metastatic regeneration in many cancers; however, elucidation of the underlying molecular network and pathways remains demanding. Combining machine learning and experimental investigation, here we report CD81, a tetraspanin transmembrane protein known to be enriched in extracellular vesicles (EVs), as a newly identified driver of breast cancer stemness and metastasis. Using protein structure modeling and interface prediction-guided mutagenesis, we demonstrate that membrane CD81 interacts with CD44 through their extracellular regions in promoting tumor cell cluster formation and lung metastasis of triple negative breast cancer (TNBC) in human and mouse models. In-depth global and phosphoproteomic analyses of tumor cells deficient with CD81 or CD44 unveils endocytosis-related pathway alterations, leading to further identification of a quality-keeping role of CD44 and CD81 in EV secretion as well as in EV-associated stemness-promoting function. CD81 is coexpressed along with CD44 in human circulating tumor cells (CTCs) and enriched in clustered CTCs that promote cancer stemness and metastasis, supporting the clinical significance of CD81 in association with patient outcomes. Our study highlights machine learning as a powerful tool in facilitating the molecular understanding of new molecular targets in regulating stemness and metastasis of TNBC.

TIGAR (TP53-induced glycolysis and apoptosis regulator) is a novel dual regulator of glycolysis and apoptosis regulated by p53. TIGAR was first found to protect normal cells from oxidative stress by inducing cellular production of NADPH, a powerful reducing agent in the cell, via the pentose phosphate shunt. Nasopharyngeal carcinoma (NPC) is a highly metastatic head and neck cancer prevalent in Southeast Asia. Our previous studies demonstrated that overexpression of TIGAR rescued NPC cells from growth inhibition induced by c-Met kinase inhibitors and an RNA anti-metabolite (ECyd), suggesting an anti-apoptotic function of TIGAR in NPC. Here, we demonstrated by Western blotting and immunohistochemistry that TIGAR was expressed in primary tumor biopsies of NPC. Moreover, NPC cell lines from various differentiation status also expressed TIGAR. Using an Epstein-Barr virus-associated NPC cell line, HONE-1-LMP1 cells, we showed that specific knockdown of TIGAR by siRNA inhibited cell proliferation (∼45%) at 48 hrs. Moreover, TIGAR overexpression markedly increased NPC cell proliferation (&amp;gt;300%), which was accompanied by significant induction of cellular NADPH production (&amp;gt;200%). This indicates that TIGAR-induced generation of NADPH, which is an important building block for major cellular metabolites for proliferation (including DNA, RNA and fatty acids, etc), may be involved in NPC carcinogenesis. Furthermore, TIGAR overexpression induced the expression of a pro-survival protein, Mcl-1 in NPC cells, which supports an anti-apoptotic function of TIGAR in NPC. Our results implicate that TIGAR may confer survival benefits to NPC cells via metabolic alteration. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1006. doi:10.1158/1538-7445.AM2011-1006

TP53-induced glycolysis and apoptosis regulator (TIGAR) is an important gene that encodes a regulatory enzyme of glycolysis and reactive oxygen species (ROS) detoxification and is associated with worse prognosis in various cancers. Ferroptosis is a recently identified type of programmed cell death that is triggered by iron-dependent lipid peroxidation. There are no reports on the prognostic impact of TIGAR on intrahepatic cholangiocarcinoma (ICC), and its role in ferroptosis is unclear. Ninety ICC patients who had undergone hepatic resection were enrolled. Immunohistochemical staining for TIGAR was performed. The regulation of malignant activity by TIGAR and the association between ferroptosis and TIGAR were investigated in vitro. Twenty-two (24.4%) patients were categorized into TIGAR-high and -low groups by immunohistochemical staining. There were no noticeable differences in background factors between the two groups, but TIGAR positivity was an independent prognostic factor in disease-free survival (hazard ratio [HR], 2.00; 95% confidence interval [CI], 1.04-3.85, p = 0.0378) and overall survival (HR, 2.10; 95% CI, 1.03-4.30, p = 0.00422) in a multivariate analysis. In vitro, TIGAR knockdown (KD) decreased cell motility (cell proliferation/migration/invasion/colony-forming capabilities) and elevated ROS and lipid peroxidation. This indicated that TIGAR KD induced ferroptosis. TIGAR KD-induced ferroptosis was suppressed using liproxstatin. TIGAR KD decreased the expression of glutathione peroxidase 4, known as factor-suppressing ferroptosis. The combination of TIGAR KD with cisplatin significantly induced more ferroptosis. In conclusion, TIGAR is associated with poor outcomes in ICC patients and resistance to ferroptosis.

BackgroundCancer cells show increased glycolysis and take advantage of this metabolic pathway to generate ATP. The TP53-induced glycolysis and apoptosis regulator (TIGAR) inhibits aerobic glycolysis and protects tumor cells from intracellular reactive oxygen species (ROS)-associated apoptosis. However, the function of TIGAR in glycolysis and survival of acute myeloid leukemia cells remains unclear.MethodsWe analyzed TIGAR expression in cytogenetically normal (CN-) AML patients and the correlations with clinical and biological parameters. In vivo and in vitro, we tested whether glycolysis may induce TIGAR expression and evaluated the combination effect of glycolysis inhibitor and TIGAR knockdown on human leukemia cell proliferation.ResultsHigh TIGAR expression was an independent predictor of poor survival and high incidence of relapse in adult patients with CN-AML. TIGAR also showed high expression in multiple human leukemia cell lines and knockdown of TIGAR activated glycolysis through PFKFB3 upregulation in human leukemia cells. Knockdown of TIGAR inhibited the proliferation of human leukemia cells and sensitized leukemia cells to glycolysis inhibitor both in vitro and in vivo. Furthermore, TIGAR knockdown in combination with glycolysis inhibitor 2-DG led leukemia cells to apoptosis. In addition, the p53 activator Nutlin-3α showed a significant combinational effect with TIGAR knockdown in leukemia cells. However, TIGAR expression and its anti-apoptotic effects were uncoupled from overexpression of exogenous p53 in leukemia cells.ConclusionsTIGAR might be a predictor of poor survival and high incidence of relapse in AML patients, and the combination of TIGAR inhibitors with anti-glycolytic agents may be novel therapies for the future clinical use in AML patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-016-0360-4) contains supplementary material, which is available to authorized users.

Background: Although metabolic alterations were observed in heart failure (HF), only recently have the mechanisms underlying these changes been identified. Tumor suppressor p53 responds to metabolic changes thorough several mechanisms. One of the p53 targets, TIGAR (TP53-induced glycolysis and apoptosis regulator) reduces glycolysis and suppresses autophagy, which augments ischemic damage, however its role on HF is unclear. Method and Results: In order to investigate TIGAR’s function in HF, we compared myocardial metabolic and functional outcomes between TIGAR deficient (TIGAR–/–) mice and wild-type (TIGAR+/+) mice subjected to chronic thoracic transverse aortic constriction (TAC), a pressure-overload HF model. In wild-type mice hearts, p53 and TIGAR increased markedly during HF development. Eight weeks after TAC surgery, the left ventricular (LV) dysfunction, fibrosis, oxidative damage, and myocyte apoptosis were significantly advanced in wild-type than in TIGAR–/– mouse heart. Further, myocardial high-energy phosphates in wild-type hearts were significantly decreased compared to those of TIGAR–/– mouse heart. Glucose oxidation and glycolysis rates were also reduced in isolated perfused wild-type hearts following TAC than those in TIGAR–/– hearts, which suggest that the upregulation of TIGAR in HF causes impaired myocardial energetics and function. The effects of TIGAR knockout on LV function were also replicated in tamoxifen (TAM)-inducible cardiac-specific TIGAR knockout mice (TIGARflox/flox/ Tg(Myh6-cre/Esr1) mice). Conclusion: The ablation of TIGAR during pressure-overload HF preserves myocardial function and energetics. Thus, cardiac TIGAR targeted therapy to increase glucose metabolism will be a novel strategy for HF.