CC3/TIP30 regulates metabolic adaptation of tumor cells to glucose limitation

Elaboration and validation of a prognostic signature associated with disulfidoptosis in lung adenocarcinoma, consolidated with integration of single-cell RNA sequencing and bulk RNA sequencing techniques

Background

Lung adenocarcinoma (LUAD), the predominant subtype of non-small cell lung cancer (NSCLC), remains a pervasive global public health concern. Disulfidoptosis, a nascent form of regulated cell death (RCD), presents an emerging field of inquiry. Currently, investigations into disulfidoptosis are in their initial stages. Our undertaking sought to integrate single-cell RNA sequencing (scRNA-seq) in conjunction with traditional bulk RNA sequencing (bulk RNA-seq) methodologies, with the objective of delineating genes associated with disulfidoptosis and subsequently prognosticating the clinical outcomes of LUAD patients.

Methods

Initially, we conducted an in-depth examination of the cellular composition disparities existing between LUAD and normal samples using scRNA-seq data sourced from GSE149655. Simultaneously, we scrutinized the expression patterns of disulfidoptosis-associated gene sets across diverse cell types. Subsequently, leveraging the bulk RNA-seq data, we formulated disulfidoptosis-related prognostic risk signatures (DRPS) employing LASSO-Cox regression. This was accomplished by focusing on genes implicated in disulfidoptosis that exhibited differential expression within endothelial cells (ECs). Sequentially, the robustness and precision of the DRPS model were rigorously verified through both internal and external validation datasets. In parallel, we executed single-cell trajectory analysis to delve into the differentiation dynamics of ECs. Concluding our study, we undertook a comprehensive investigation encompassing various facets. These included comparative assessments of enrichment pathways, clinicopathological parameters, immune cell abundance, immune response-associated genes, impacts of immunotherapy, and drug predictions among distinct risk cohorts.

Results

The scrutiny of scRNA-seq data underscored discernible disparities in cellular composition between LUAD and normal samples. Furthermore, disulfidoptosis-associated genes exhibited marked discrepancies within endothelial cells (ECs). Consequently, we formulated the Disulfidoptosis-Related Prognostic Signature (DRPS) to facilitate prognostic prediction. The prognostic nomogram based on the risk score effectively demonstrated DRPS's robust capacity to prognosticate survival outcomes. This assertion was corroborated by rigorous assessments utilizing both internal and external validation sets, thus affirming the commendable predictive accuracy and enduring stability of DRPS. Functional enrichment analysis shed light on the significant correlation of DRPS with pathways intrinsic to the cell cycle. Subsequent analysis unveiled correlations between DRPS and gene mutations characteristic of LUAD, as well as indications of an immunosuppressive status. Through drug prediction, we explored potential therapeutic agents for low-risk patients. Concluding our investigation, qRT-PCR experiments confirmed the heightened expression levels of EPHX1, LDHA, SHC1, MYO6, and TLE1 in lung cancer cell lines.

Genome-wide association study of the age of onset of type 1 diabetes reveals HTATIP2 as a novel T cell regulator

Introduction

Type 1 diabetes, a disorder caused by autoimmune destruction of pancreatic insulin-producing cells, is more difficult to manage when it presents at a younger age. We sought to identify genetic correlates of the age of onset by conducting the first genome-wide association study (GWAS) treating the age of first diagnosis as a quantitative trait.

Methods

We performed GWAS with a discovery cohort of 4,014 cases and a replication cohort of 493 independent cases. Genome-wide significant SNPs were mapped to a causal variant by Bayesian conditional analysis and gel shift assay. The causal protein-coding gene was identified and characterized by RNA interference treatment of primary human pan-CD4+ T cells with RNA-seq of the transcriptome. The candidate gene was evaluated functionally in primary cells by CD69 staining and proliferation assays.

Results

Our GWAS replicated the known association of the age of diagnosis with the human leukocyte antigen complex (HLA-DQB1). The second signal identified was in an intron of the NELL1 gene on chromosome 11 and fine-mapped to variant rs10833518 (P < 1.54 × 10^-9). Homozygosity for the risk allele leads to average age of onset one year earlier. Knock-down of HIV TAT-interacting protein 2 (HTATIP2), but not other genes in the locus, resulted in alterations to gene expression in signal transduction pathways including MAP kinases and PI3-kinase. Higher levels of HTATIP2 expression are associated with increased viability, proliferation, and activation of T cells in the presence of signals from antigen and cytokine receptors.

Discussion

This study implicates HTATIP2 as a new type 1 diabetes gene acting via T cell regulation. Larger population sample sizes are expected to reveal additional loci.

Intermittent fasting induces chronic changes in the hepatic gene expression of Red Jungle Fowl (Gallus gallus)

Background

Intermittent fasting (IF), the implementation of fasting periods of at least 12 consecutive hours on a daily to weekly basis, has received a lot of attention in recent years for imparting the life-prolonging and health-promoting effects of caloric restriction with no or only moderate actual restriction of caloric intake. IF is also widely practiced in the rearing of broiler breeders, the parent stock of meat-type chickens, who require strict feed restriction regimens to prevent the serious health problems associated with their intense appetites. Although intermittent fasting has been extensively used in this context to reduce feed competition and its resulting stress, the potential of IF in chickens as an alternative and complementary model to rodents has received less investigation. In both mammals and birds, the liver is a key component of the metabolic response to IF, responding to variations in energy balance. Here we use a microarray analysis to examine the liver transcriptomics of wild-type Red Jungle Fowl chickens fed either ad libitum, chronically restricted to around 70% of ad libitum daily or intermittently fasted (IF) on a 2:1 (2 days fed, 1 day fasted) schedule without actual caloric restriction. As red junglefowl are ancestral to domestic chicken breeds, these data serve as a baseline to which existing and future transcriptomic results from farmed birds such as broiler breeders can be compared.

Results

We find large effects of feeding regimen on liver transcriptomics, with most of the affected genes relating to energy metabolism. A cluster analysis shows that IF is associated with large and reciprocal changes in genes related to lipid and carbohydrate metabolism, but also chronic changes in genes related to amino acid metabolism (generally down-regulated) and cell cycle progression (generally up-regulated). The overall transcription pattern appears to be one of promoting high proliferative plasticity in response to fluctuations in available energy substrates. A small number of inflammation-related genes also show chronically changed expression profiles, as does one circadian rhythm gene.

Conclusions

The increase in proliferative potential suggested by the gene expression changes reported here indicates that birds and mammals respond similarly to intermittent fasting practices. Our findings therefore suggest that the health benefits of periodic caloric restriction are ubiquitous and not restricted to mammals alone. Whether a common fundamental mechanism, for example involving leptin, underpins these benefits remains to be elucidated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08533-5.

Metabolic Constants and Plasticity of Cancer Cells in a Limiting Glucose and Glutamine Microenvironment-A Pyruvate Perspective

The metabolism of cancer cells is an issue of dealing with fluctuating and limiting levels of nutrients in a precarious microenvironment to ensure their vitality and propagation. Glucose and glutamine are central metabolites for catabolic and anabolic metabolism, which is in the limelight of numerous diagnostic methods and therapeutic targeting. Understanding tumor metabolism in conditions of nutrient depletion is important for such applications and for interpreting the readouts. To exemplify the metabolic network of tumor cells in a model system, the fate ¹³C₆-glucose was tracked in a breast cancer cell line growing in variable low glucose/low glutamine conditions. ¹³C-glucose-derived metabolites allowed to deduce the engagement of metabolic pathways, namely glycolysis, the TCA-cycle including glutamine and pyruvate anaplerosis, amino acid synthesis (serine, glycine, aspartate, glutamate), gluconeogenesis, and pyruvate replenishment. While the metabolic program did not change, limiting glucose and glutamine supply reduced cellular metabolite levels and enhanced pyruvate recycling as well as pyruvate carboxylation for entry into the TCA-cycle. Otherwise, the same metabolic pathways, including gluconeogenesis, were similarly engaged with physiologically saturating as with limiting glucose and glutamine. Therefore, the metabolic plasticity in precarious nutritional microenvironment does not require metabolic reprogramming, but is based on dynamic changes in metabolite quantity, reaction rates, and directions of the existing metabolic network.

Absence of HTATIP2 Expression in A549 Lung Adenocarcinoma Cells Promotes Tumor Plasticity in Response to Hypoxic Stress

HIV-1 Tat Interactive Protein 2 (HTATIP2) is a tumor suppressor, of which reduced or absent expression is associated with increased susceptibility to tumorigenesis and enhanced tumor invasion and metastasis. However, whether the absent expression of HTATIP2 is a tumor-promoting factor that acts through improving tumor adaptation to hypoxia is unclear. Here, we established a stable HTATIP2-knockdown A549 human lung adenocarcinoma cell line (A549shHTATIP2) using lentiviral-delivered HTATIP2-targeting short hairpin RNA (shRNA), employed a double subcutaneous xenograft model and incorporated photoacoustic imaging and metabolomics approaches to elucidate the impact of the absent HTATIP2 expression on tumor response to hypoxic stress. Results from the in vivo study showed that A549shHTATIP2 tumors exhibited accelerated growth but decreased intratumoral oxygenation and angiogenesis and reduced sensitivity to sorafenib treatment as compared with their parental counterparts. Moreover, results of the immunoblot and real-time PCR analyses revealed that the HIF2α protein and mRNA levels in vehicle-treated A549shHTATIP2 tumors were significantly increased (p < 0.01 compared with the parental control tumors). Despite the strong HIF2α-c-Myc protein interaction indicated by our co-immunoprecipitation data, the increase in the c-Myc protein and mRNA levels was not significant in the A549shHTATIP2 tumors. Nonetheless, MCL-1 and β-catenin protein levels in A549shHTATIP2 tumors were significantly increased (p < 0.05 compared with the parental control tumors), suggesting an enhanced β-catenin/c-Myc/MCL-1 pathway in the absence of HTATIP2 expression. The finding of significantly decreased E-cadherin (p < 0.01 compared with vehicle-treated A549shHTATIP2 tumors) and increased vimentin (p < 0.05 compared with sorafenib-treated A549 tumors) protein levels in A549shHTATIP2 tumors implicates that the absence of HTATIP2 expression increases the susceptibility of A549 tumors to sorafenib-activated epithelial-mesenchymal transition (EMT) process. Comparison of the metabolomic profiles between A549 and A549shHTATIP2 tumors demonstrated that the absence of HTATIP2 expression resulted in increased tumor metabolic plasticity that enabled tumor cells to exploit alternative metabolic pathways for survival and proliferation rather than relying on glutamine and fatty acids as a carbon source to replenish TCA cycle intermediates. Our data suggest a mechanism by which the absent HTATIP2 expression modulates tumor adaptation to hypoxia and promotes an aggressive tumor phenotype by enhancing the HIF2α-regulated β-catenin/c-Myc/MCL-1 signaling, increasing the susceptibility of tumors to sorafenib treatment-activated EMT process, and improving tumor metabolic plasticity.

Malathion induced cancer-linked gene expression in human lymphocytes

BACKGROUND

Malathion is the most widely used organophosphate pesticide in agriculture. Increasing cancer incidence in agricultural workers and their children links to the exposure of malathion. Identification of genes involved in the process of carcinogenesis is essential for exploring the role of malathion. The alteration in gene expression by malathion in human lymphocytes has not been explored yet, although hematological malignancies are rampant in humans.

OBJECTIVE

This study investigates the malathion induced expression of cancer associated genes in human lymphocytes.

METHODS

Human lymphocyte viability and colony-forming ability were analyzed in malathion treated and control groups. Gene expression profile in control and malathion treated human lymphocytes were performed using a microarray platform. The genes which have significant functions and those involved in different pathways were analyzed using the DAVID database. Differential gene expression upon malathion exposure was validated by quantitative real-time (qRT)-PCR.

RESULTS

Malathion caused a concentration-dependent reduction in human lymphocyte viability. At low concentration (50 μg/mL) of malathion treatment, human lymphocytes were viable indicating that low concentration of malathion is not cytotoxic and induces the colony formation. Total of 659 genes (15%) were up regulated and 3729 genes (85%) were down regulated in malathion treated human lymphocytes. About 57 cancer associated genes related to the growth and differentiation of B and T cells, immunoglobulin production, haematopoiesis, tumor suppression, oncogenes and signal transduction pathways like MAPK and RAS were induced by malathion.

CONCLUSION

This study evidences the carcinogenic nature of malathion. Low concentration of this pesticide is not cytotoxic and induces differentially regulated genes in human lymphocytes, which are involved in the initiation, progression, and pathogenesis of cancer.

Diverse Roads Taken by 13C-Glucose-Derived Metabolites in Breast Cancer Cells Exposed to Limiting Glucose and Glutamine Conditions

In cancers, tumor cells are exposed to fluctuating nutrient microenvironments with limiting supplies of glucose and glutamine. While the metabolic program has been related to the expression of oncogenes, only fractional information is available on how variable precarious nutrient concentrations modulate the cellular levels of metabolites and their metabolic pathways. We thus sought to obtain an overview of the metabolic routes taken by ¹³C-glucose-derived metabolites in breast cancer MCF-7 cells growing in combinations of limiting glucose and glutamine concentrations. Isotopologue profiles of key metabolites were obtained by gas chromatography/mass spectrometry (GC/MS). They revealed that in limiting and standard saturating medium conditions, the same metabolic routes were engaged, including glycolysis, gluconeogenesis, as well as the TCA cycle with glutamine and pyruvate anaplerosis. However, the cellular levels of ¹³C-metabolites, for example, serine, alanine, glutamate, malate, and aspartate, were highly sensitive to the available concentrations and the ratios of glucose and glutamine. Notably, intracellular lactate concentrations did not reflect the Warburg effect. Also, isotopologue profiles of ¹³C-serine as well as ¹³C-alanine show that the same glucose-derived metabolites are involved in gluconeogenesis and pyruvate replenishment. Thus, anaplerosis and the bidirectional flow of central metabolic pathways ensure metabolic plasticity for adjusting to precarious nutrient conditions.

mTOR direct crosstalk with STAT5 promotes de novo lipid synthesis and induces hepatocellular carcinoma

Hepatocellular carcinoma (HCC) can be the last step of nonalcoholic fatty liver disease (NAFLD) evolution, and the main characteristic of NAFLD is alteration in lipid metabolism. However, the mechanisms of abnormal lipid metabolism in NAFLD and HCC progression are yet to be identified. Here, we demonstrate that liver-specific activation of mTORC1 promoted the expression of lipid synthesis genes and lead to the development of spontaneous HCC. Genetic mouse models developed spontaneous HCC along with increased expressions of SREBP1, ACC1 and FASN. In addition, high levels of p-STAT5 were observed in the livers and particularly evident in the tumor area. And the synthesis of p-STAT5 was increased in patients along with the increase in SREBP1 synthesis in clinical samples. Moreover, mTORC1 interacts with and phosphorylates the STAT5 in hepatocytes. In conclusion, our data suggested that mTORC1 upregulates SREBP1 transcription via crosstalk with the STAT5 pathway which contributes to the NAFLD-related HCC pathogenesis. And the inhibitor of SREBP1 and mTOR may help to prevent HCC in clinical NAFLD patients.

Subcongenic analysis of a quantitative trait locus affecting body weight and glucose metabolism in zinc transporter 7 (znt7)-knockout mice

Background

A genome-wide mapping study using male F₂zinc transporter 7-knockout mice (znt7-KO) and their wild type littermates in a mixed 129P1/ReJ (129P1) and C57BL/6J (B6) background identified a quantitative trait locus (QTL) on chromosome 7, which had a synergistic effect on body weight gain and fat deposit with the znt7-null mutation.

Results

The genetic segment for body weight on mouse chromosome 7 was investigated by newly created subcongenic znt7-KO mouse strains carrying different lengths of genomic segments of chromosome 7 from the 129P1 donor strain in the B6 background. We mapped the sub-QTL for body weight in the proximal region of the previously mapped QTL, ranging from 47.4 to 64.4 megabases (Mb) on chromosome 7. The 129P1 donor allele conferred lower body weight gain and better glucose handling during intraperitoneal glucose challenge than the B6 allele control. We identified four candidate genes, including Htatip2, E030018B13Rik, Nipa1, and Atp10a, in this sub-QTL using quantitative RT-PCR and cSNP detection (single nucleotide polymorphisms in the protein coding region).

Conclusions

This study dissected the genetic determinates of body weight and glucose metabolism in znt7-KO mice. The study demonstrated that a 17-Mb long 129P1 genomic region on mouse chromosome 7 conferred weight reduction and improved glucose tolerance in znt7-KO male mice. Among the four candidate genes identified, Htatip2 is the most likely candidate gene involved in the control of body weight based on its function in regulation of lipid metabolism. The candidate genes discovered in this study lay a foundation for future studies of their roles in development of metabolic diseases, such as obesity and type 2 diabetes.

Electronic supplementary material

The online version of this article (10.1186/s12863-019-0715-2) contains supplementary material, which is available to authorized users.

Disease-modifying effects of metabolic perturbations in ALS/FTLD

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are two fatal neurodegenerative disorders with considerable clinical, pathological and genetic overlap. Both disorders are characterized by the accumulation of pathological protein aggregates that contain a number of proteins, most notably TAR DNA binding protein 43 kDa (TDP-43). Surprisingly, recent clinical studies suggest that dyslipidemia, high body mass index, and type 2 diabetes mellitus are associated with better clinical outcomes in ALS. Moreover, ALS and FTLD patients have a significantly lower incidence of cardiovascular disease, supporting the idea that an unfavorable metabolic profile may be beneficial in ALS and FTLD. The two most widely studied ALS/FTLD models, super-oxide dismutase 1 (SOD1) and TAR DNA binding protein of 43 kDA (TDP-43), reveal metabolic dysfunction and a positive effect of metabolic strategies on disease onset and/or progression. In addition, molecular studies reveal a role for ALS/FTLD-associated proteins in the regulation of cellular and whole-body metabolism. Here, we systematically evaluate these observations and discuss how changes in cellular glucose/lipid metabolism may result in abnormal protein aggregations in ALS and FTLD, which may have important implications for new treatment strategies for ALS/FTLD and possibly other neurodegenerative conditions.

Reduction of Tat-interacting Protein 30 Expression Could be a Prognostic Marker in Bladder Urothelial Cancer

Background:

Tat-interacting protein 30 (TIP30) has been reported to be a tumor suppressor, with reduced or absent expression in various tumors. However, its role in bladder urothelial cancer (BUC) has not been investigated. Therefore, herein, we investigated the expression of TIP30 protein in BUC and normal bladder mucosa and the clinical significance of TIP30 expression in the prognosis of BUC.

Methods:

We reviewed data from 79 cases of BUC and 15 adjacent tissue samples from 79 patients treated at our institution between 2004 and 2007. TIP30 expression was examined by immunohistochemistry. The relationship between TIP30 expression and tumor stage, histological grade, and survival was analyzed. Differences between groups were evaluated using the t-test or matched-pairs test, and differences in the survival rates were analyzed with the log-rank test.

Results:

TIP30 protein expression was significantly reduced in BUC tissue (t = −6.91, P < 0.05) compared with normal tissue samples, and in invasive bladder cancer (t = 10.89, P < 0.05) compared with superficial bladder cancer. TIP30 protein expression differed significantly among different differentiated groups classified either according to the World Health Organization (2004, F = 17.48, P < 0.01) or World Health Organization (1973, F = 10.68, P < 0.01). TIP30 protein expression was significantly reduced in high-grade papillary urothelial carcinoma compared with papillary urothelial neoplasm of low malignant potential (P < 0.05) and low-grade papillary urothelial carcinoma (P < 0.05). Meanwhile, TIP30 protein expression was significantly reduced in Grade III BUC, compared with Grade I (P < 0.05) and Grade II (P < 0.05). Patients with low TIP30 expression showed a higher incidence of disease progression than those with high TIP30 expression (t = 2.63, P < 0.05). Kaplan-Meier survival analysis showed a strong positive relationship between TIP30 expression and overall survival (OS) (χ² = 17.29, P < 0.05).

Conclusions:

TIP30 expression was associated with clinical tumor stage in BUC, suggesting that it might play an important role in disease progression. Furthermore, TIP30 might predict postoperative OS. Thus, its evaluation might be useful for predicting prognosis.

TIP30 regulates lipid metabolism in hepatocellular carcinoma by regulating SREBP1 through the Akt/mTOR signaling pathway

Lipid reprogramming has been considered as a crucial characteristic in hepatocellular carcinoma (HCC) initiation and progression. However, detailed molecular mechanisms have yet to be clearly defined. Here, we examined the effects of tumor suppressor TIP30 on the regulation of HCC lipid metabolism. We found that decreased TIP30 expression leads to elevated fatty acid synthesis and enhanced levels of lipogenic enzymes SCD and FASN in HCC cells. Moreover, SREBP1 is one of the key transcription factors regulating liver lipid metabolism, and TIP30 deficiency significantly increased SREBP1 expression and nuclear accumulation. Small interfering RNAs targeting SREBP1 could reverse fatty acid synthesis induced by TIP30 deficiency. Furthermore, downregulating TIP30 activated the Akt/mTOR signaling pathway to upregulate SREBP1 expression, which promoted lipid metabolism by activating gene transcription of lipogenesis, including fasn and scd. We also showed that TIP30 deficiency-regulated lipid metabolism promoted proliferation of HCC cells. Clinically, our data revealed that TIP30 expression significantly correlated with SREBP1 in patients with HCC and that a combination of TIP30 and SREBP1 is a powerful predictor of HCC prognosis. Together, our data suggested a novel function of TIP30 in HCC progression and indicate that TIP30 regulation of SREBP1 may represent a novel target for HCC treatment.

Metabolic Pathway Inhibition in Liver Cancer

Liver cancer is fundamentally physiologically different from the surrounding liver tissue. Despite multiple efforts to target the altered signaling pathways created by oncogenic mutations, not many have focused on targeting the altered metabolism that allows liver cancer to develop and grow. Still to be resolved is the question of whether the altered metabolic pathways in this cancer differ enough from the surrounding noncancerous cells to allow for the development of potent and specific compounds. Clinical studies of metabolic modulators would provide some more information with regard to the feasibility of this approach. Furthermore, as it appears that oncogenic signaling is essential to this cancer's altered metabolism, it stands to reason that targeting this altered signaling may allow the exploitation of specific metabolic vulnerabilities in combination with other drugs for enhanced efficacy. The identification of biomarkers of metabolic sensitivity will also be essential to determine whether these drugs will have the desired effect.

Alteration of cellular metabolism in cancer cells and its therapeutic prospects

Transformation of a normal cell into a cancerous phenotype is essentially backed by genetic mutations that trigger several oncogenic signaling pathways. These signaling pathways rewire the cellular metabolism to meet the bioenergetic and biomass requirement of proliferating cell, which is different from a quiescent cell. Although the change of metabolism in a cancer cell was observed and studied in the mid-20^th century, it was not adequate to explain oncogenesis. Now, equipped with a revolution of oncogenes, we have a genetic basis to explain the transformation. Through several studies, it is clear now that such metabolic alterations not only promote cancer progression but also contribute to the chemoresistance of cancer. Targeting specific enzymes and combinations of enzymes can improve the efficacy of cancer therapy and help to overcome the therapeutic resistance.

Tat-Interacting Protein 30 (TIP30) Expression Serves as a New Biomarker for Tumor Prognosis: A Systematic Review and Meta-Analysis

BACKGROUND

Tat-interacting protein 30 (TIP30) is a tumor suppressor protein that has been found to be expressed in a wide variety of tumor tissues. TIP30 is involved in the control of cell apoptosis, growth, metastasis, angiogenesis, DNA repair, and tumor cell metabolism. The methylation of the TIP30 promoter is also associated with tumor prognosis. To evaluate this topic further, we conducted a systematic meta-analysis to explore the clinicopathological and prognostic significance of TIP30 for tumor patients.

METHODS

We searched PubMed and EMBASE for eligible studies. We manually searched for printed journals and relevant textbooks. Subgroup analyses were performed based on the region, manuscript quality, methods of vasculogenic mimicry identification, pathology, and number of patients.

RESULTS

Fourteen studies with 1705 patients were included in this meta-analysis. A significant association was observed between high expression of TIP30 in patients with cancer with a good overall survival (hazard ratio = 0.53, 95% confidence interval: 0.41-0.69), and good recurrence-free survival or disease free survival (hazard ratio = 0.49, 95% confidence interval: 0.37-0.66). Lack of expression of TIP30 had an association with lymph node metastasis (odds ratio = 3.90, 95% confidence interval: 2.21-6.89) and high tumor node metastasis clinical stage (odds ratio = 2.10, 95% confidence interval: 1.68-2.62). The methylation of the TIP30 promoter did not significantly influence the overall survival (hazard ratio = 0.99, 95% confidence interval: 0.88-1.13) or disease free survival (hazard ratio = 0.62, 95% confidence interval: 0.19-2.02).

CONCLUSIONS

TIP30 expression is associated with a good prognosis in patients with tumors. Clinical studies with large samples are needed worldwide and standardized protocols should be adopted in the future to achieve a better understanding of the relationship between tumor prognosis and TIP30.

Hypoglycemia Enhances Epithelial-Mesenchymal Transition and Invasiveness, and Restrains the Warburg Phenotype, in Hypoxic HeLa Cell Cultures and Microspheroids

The accelerated growth of solid tumors leads to episodes of both hypoxia and hypoglycemia (HH) affecting their intermediary metabolism, signal transduction, and transcriptional activity. A previous study showed that normoxia (20% O₂ ) plus 24 h hypoglycemia (2.5 mM glucose) increased glycolytic flux whereas oxidative phosphorylation (OxPhos) was unchanged versus normoglycemia in HeLa cells. However, the simultaneous effect of HH on energy metabolism has not been yet examined. Therefore, the effect of hypoxia (0.1-1% O₂ ) plus hypoglycemia on the energy metabolism of HeLa cells was analyzed by evaluating protein content and activity, along with fluxes of both glycolysis and OxPhos. Under hypoxia, in which cell growth ceased and OxPhos enzyme activities, ΔΨm and flux were depressed, hypoglycemia did not stimulate glycolytic flux despite increasing H-RAS, p-AMPK, GLUT1, GLUT3, and HKI levels, and further decreasing mitochondrial enzyme content. The impaired mitochondrial function in HH cells correlated with mitophagy activation. The depressed OxPhos and unchanged glycolysis pattern was also observed in quiescent cells from mature multicellular tumor spheroids, suggesting that these inner cell layers are similarly subjected to HH. The principal ATP supplier was glycolysis for HH 2D monolayer and 3D quiescent spheroid cells. Accordingly, the glycolytic inhibitors iodoacetate and gossypol were more effective than mitochondrial inhibitors in decreasing HH-cancer cell viability. Under HH, stem cell-, angiogenic-, and EMT-biomarkers, as well as glycoprotein-P content and invasiveness, were also enhanced. These observations indicate that HH cancer cells develop an attenuated Warburg and pronounced EMT- and invasive-phenotype. J. Cell. Physiol. 232: 1346-1359, 2017. © 2016 Wiley Periodicals, Inc.

TIP30: A Novel Tumor-Suppressor Gene

TIP30/CC3 was first identified and characterized as a "candidate" tumor-suppressor gene in 1997. Recently, the TIP30 tumor-suppressor status has been fully established since several studies have described that TIP30 protein expression is frequently downregulated in diverse types of human tumors, and the downregulation is often associated with tumor progression. TIP30 is involved in the control of cell apoptosis, growth, metastasis, angiogenesis, DNA repair, and tumor cell metabolism. Moreover, TIP30(-/-) mice spontaneously develop hepatocellular carcinoma and other tumors at a higher incidence than that of wild-type mice. In this review, we provide an overview of current knowledge concerning the role of TIP30 in tumor development and progression. To our knowledge, this is the first review about the role of novel tumor-suppressor gene TIP30 in tumor development and progression.

Metformin inhibits the prometastatic effect of sorafenib in hepatocellular carcinoma by upregulating the expression of TIP30

We previously found that a low dose of sorafenib had a prometastatic effect on hepatocellular carcinoma (HCC), which was caused by downregulation of TIP30 expression. More recently, metformin has been shown to have potential as a preventive and therapeutic agent for different cancers, including HCC. This study evaluated whether the combination of sorafenib and metformin is sufficient to revert the expression of TIP30, thereby simultaneously reducing lung metastasis and improving survival. Our data show that the combination of sorafenib and metformin inhibits proliferation and invasion in vitro, prolongs median survival, and reduces lung metastasis of HCC in vivo. This effect is closely associated with the upregulation of TIP30, partly through activating AMP‐activated protein kinase. Thioredoxin, a prometastasis factor, is negatively regulated by TIP30 and plays an essential role during the process of HCC metastasis. Overall, our results suggest that metformin might be a potent enhancer for the treatment of HCC by using sorafenib.

Novel therapeutic targets of tumor metabolism

The study of tumor metabolism has resulted in new understandings of how cancer cells modify metabolic pathways that control cellular energetics to allow increased proliferation and survival. Tumor cells have been shown to alter metabolic pathways involved in glucose, glutamine, and mitochondrial metabolism to generate raw materials needed for rapid cellular proliferation, maintain favorable cellular redox environments, modify cellular epigenetics, and even promote and maintain oncogenic transformation. As a consequence, there has been intense scientific and clinical interest in targeting metabolic alterations that are commonly adopted by tumor cells for therapeutic purposes. In this review, we describe common metabolic alterations seen in tumor cells and discuss how these alterations are being investigated as potential targets for pharmacological intervention in preclinical and clinical settings. We also discuss some of the challenges associated with using tumor metabolism as a therapeutic target in cancer therapy, along with potential avenues to overcome these challenges.

NADH-linked metabolic plasticity of MCF-7 breast cancer cells surviving in a nutrient-deprived microenvironment

Characteristic of the tumor microenvironment are fluctuating gradients of reduced nutrient levels and released lactate. A fundamental issue is how tumor cells modulate their metabolic activity when both glucose and glutamine levels become limiting in the presence of high exogenous lactate. For functional analyses, the activities of pyruvate kinase, lactate dehydrogenase (LDH) and plasma membrane NADH oxidase (NOX) as well as cell growth were measured in breast cancer MCF-7 cells cultured in medium containing various concentrations of these metabolites. After 3 days at glucose concentrations below 2.5 mM, cell number was higher with 0.1 mM than with 1.0 mM glutamine, indicating that the glucose/glutamine balance is important for growth. On the other hand, NOX activity increased with increasing glucose >2.5 mM, but only with low glutamine (0.1 mM). Pyruvate kinase activity also increased, with LDH activity remaining 2-3-fold lower. Here NOX could have a complementary role in reoxidizing NADH for glycolysis. Exogenous lactate supported cell survival at limiting concentrations of glucose and glutamine while increasing NOX and pyruvate kinase activities as well as NADH levels. It is proposed that lactate supports cell survival by fuelling gluconeogenesis and/or the TCA cycle in mitochondria, from where NADH could be shuttled to the cytosol and reoxidized by NOX. Cell survival and the metabolic phenotype are thus interrelated to the dynamics of NADH and plasma membrane NOX activity, which are regulated by the balance of glucose/glutamine levels, in conjunction with lactate in a precarious tumor microenvironment.

Proteomic analysis of livers from fat-fed mice deficient in either PKCδ or PKCε identifies Htatip2 as a regulator of lipid metabolism

Insulin resistance contributes to the development of Type 2 diabetes, and is associated with lipid oversupply. Deletion of isoforms of the lipid-activated protein kinase C (PKC) family, PKCδ or PKCε, improves insulin action in fat-fed mice, but differentially affects hepatic lipid metabolism. To investigate the mechanisms involved, we employed an in vivo adaptation of SILAC to examine the effects of a fat diet together with deletion of PKCδ or PKCε on the expression of liver proteins. We identified a total of 3359 and 3488 proteins from the PKCδ and PKCε knockout study groups, respectively, and showed that several enzymes of lipid metabolism were affected by the fat diet. In fat-fed mice, 23 proteins showed changes upon PKCδ deletion while 19 proteins were affected by PKCε deletion. Enzymes of retinol metabolism were affected by the absence of either PKC. Pathway analysis indicated that monosaccharide metabolism was affected only upon PKCδ deletion, while isoprenoid biosynthesis was affected in a PKCε-specific manner. Certain proteins were regulated inversely, including HIV-1 tat interactive protein 2 (Htatip2). Overexpression or knockdown of Htatip2 in hepatocytes affected fatty acid storage and oxidation, consistent with a novel role in mediating the differential effects of PKC isoforms on lipid metabolism. All MS data have been deposited in the ProteomeXchange with identifier PXD000971 (http://proteomecentral.proteomexchange.org/dataset/PXD000971).

Ectopic NGAL expression can alter sensitivity of breast cancer cells to EGFR, Bcl-2, CaM-K inhibitors and the plant natural product berberine

Neutrophil gelatinase-associated lipocalin (NGAL, a.k.a Lnc2) is a member of the lipocalin family and has diverse roles. NGAL can stabilize matrix metalloproteinase-9 from autodegradation. NGAL is considered as a siderocalin that is important in the transport of iron. NGAL expression has also been associated with certain neoplasias and is implicated in the metastasis of breast cancer. In a previous study, we examined whether ectopic NGAL expression would alter the sensitivity of breast epithelial, breast and colorectal cancer cells to the effects of the chemotherapeutic drug doxorubicin. While abundant NGAL expression was detected in all the cells infected with a retrovirus encoding NGAL, this expression did not alter the sensitivity of these cells to doxorubicin as compared with empty vector-transduced cells. We were also interested in determining the effects of ectopic NGAL expression on the sensitivity to small-molecule inhibitors targeting key signaling molecules. Ectopic NGAL expression increased the sensitivity of MCF-7 breast cancer cells to EGFR, Bcl-2 and calmodulin kinase inhibitors as well as the natural plant product berberine. Furthermore, when suboptimal concentrations of certain inhibitors were combined with doxorubicin, a reduction in the doxorubicin IC 50 was frequently observed. An exception was observed when doxorubicin was combined with rapamycin, as doxorubicin suppressed the sensitivity of the NGAL-transduced MCF-7 cells to rapamycin when compared with the empty vector controls. In contrast, changes in the sensitivities of the NGAL-transduced HT-29 colorectal cancer cell line and the breast epithelial MCF-10A cell line were not detected compared with empty vector-transduced cells. Doxorubicin-resistant MCF-7/Dox (R) cells were examined in these experiments as a control drug-resistant line; it displayed increased sensitivity to EGFR and Bcl-2 inhibitors compared with empty vector transduced MCF-7 cells. These results indicate that NGAL expression can alter the sensitivity of certain cancer cells to small-molecule inhibitors, suggesting that patients whose tumors exhibit elevated NGAL expression or have become drug-resistant may display altered responses to certain small-molecule inhibitors.

Sorafenib down-regulates expression of HTATIP2 to promote invasiveness and metastasis of orthotopic hepatocellular carcinoma tumors in mice

BACKGROUND & AIMS

Antiangiogenic agents can sometimes promote tumor invasiveness and metastasis, but little is known about the effects of the antiangiogenic drug sorafenib on progression of hepatocellular carcinoma (HCC).

METHODS

Sorafenib was administered orally (30 mg · kg(-1) · day(-1)) to mice with orthotopic tumors grown from HCC-LM3, SMMC7721, or HepG2 cells. We analyzed survival times of mice, along with tumor growth, metastasis within liver and to lung, and induction of the epithelial-mesenchymal transition. Polymerase chain reaction arrays were used to determine the effects of sorafenib on gene expression patterns in HCC cells. We analyzed regulation of HIV-1 Tat interactive protein 2 (HTATIP2) by sorafenib and compared levels of this protein in tumor samples from 75 patients with HCC (21 who received sorafenib after resection and 54 who did not).

RESULTS

Sorafenib promoted invasiveness and the metastatic potential of orthotopic tumors grown from SMMC7721 and HCC-LM3 cells but not from HepG2 cells. In gene expression analysis, HTATIP2 was down-regulated by sorafenib. HCC-LM3 cells that expressed small hairpin RNAs against HTATIP2 (knockdown) formed less invasive tumors in mice following administration of sorafenib than HCC-LM3 without HTATIP2 knockdown. Alternatively, HepG2 cells that expressed transgenic HTATIP2 formed more invasive tumors in mice following administration of sorafenib. Sorafenib induced the epithelial-mesenchymal transition in HCC cell lines, which was associated with expression of HTATIP2. Sorafenib regulated expression of HTATIP2 via Jun-activated kinase (JAK) and signal transducer and activator of transcription (STAT)3 signaling. Sorafenib therapy prolonged recurrence-free survival in patients who expressed lower levels of HTATIP2 compared with higher levels.

CONCLUSIONS

Sorafenib promotes invasiveness and the metastatic potential of orthotopic tumors from HCC cells in mice, down-regulating expression of HTATIP2 via JAK-STAT3 signaling.

Cancer cell growth and survival as a system-level property sustained by enhanced glycolysis and mitochondrial metabolic remodeling

Systems Biology holds that complex cellular functions are generated as system-level properties endowed with robustness, each involving large networks of molecular determinants, generally identified by “omics” analyses. In this paper we describe four basic cancer cell properties that can easily be investigated in vitro: enhanced proliferation, evasion from apoptosis, genomic instability, and inability to undergo oncogene-induced senescence. Focusing our analysis on a K-ras dependent transformation system, we show that enhanced proliferation and evasion from apoptosis are closely linked, and present findings that indicate how a large metabolic remodeling sustains the enhanced growth ability. Network analysis of transcriptional profiling gives the first indication on this remodeling, further supported by biochemical investigations and metabolic flux analysis (MFA). Enhanced glycolysis, down-regulation of TCA cycle, decoupling of glucose and glutamine utilization, with increased reductive carboxylation of glutamine, so to yield a sustained production of growth building blocks and glutathione, are the hallmarks of enhanced proliferation. Low glucose availability specifically induces cell death in K-ras transformed cells, while PKA activation reverts this effect, possibly through at least two mitochondrial targets. The central role of mitochondria in determining the two investigated cancer cell properties is finally discussed. Taken together the findings reported herein indicate that a system-level property is sustained by a cascade of interconnected biochemical pathways that behave differently in normal and in transformed cells.

Mutations and deregulation of Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades which alter therapy response

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors.

The P2X7 receptor is a key modulator of aerobic glycolysis

Ability to adapt to conditions of limited nutrient supply requires a reorganization of the metabolic pathways to balance energy generation and production of biosynthetic intermediates. Several fast-growing cells overexpress the P2X7 receptor (P2X7R) for extracellular ATP. A feature of this receptor is to allow growth in the absence of serum. We show here that transfection of P2X7R allows proliferation of P2X7R-transfected HEK293 (HEK293-P2X7) cells not only in the absence of serum but also in low (4 mM) glucose, and increases lactate output compared with mock-transfected HEK293 (HEK293-mock) cells. In HEK293-P2X7, lactate output is further stimulated upon addition of exogenous ATP or the mitochondrial uncoupler carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP). In the human neuroblastoma cell line ACN, lactate output is also dependent on P2X7R function. P2X7R-expressing cells upregulate (a) the glucose transporter Glut1, (b) the glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenase (G3PDH), (c) phosphofructokinase (PFK), (d) pyruvate kinase M2 (PKM2) and (e) pyruvate dehydrogenase kinase 1 (PDHK1); furthermore, P2X7R expression (a) inhibits pyruvate dehydrogenase (PDH) activity, (b) increases phosphorylated Akt/PKB and hypoxia-inducible factor 1α (HIF-1α) expression and (c) enhances intracellular glycogen stores. In HEK293-P2X7 cells, glucose deprivation increases lactate production, expression of glycolytic enzymes and ph-Akt/PKB level. These data show that the P2X7R has an intrinsic ability to reprogram cell metabolism to meet the needs imposed by adverse environmental conditions.

TIP30 loss enhances cytoplasmic and nuclear EGFR signaling and promotes lung adenocarcinogenesis in mice

Lung adenocarcinoma, the most common type of human non-small cell lung cancer (NSCLC), frequently overexpresses EGFR. However, the mechanisms underlying EGFR overexpression are not completely understood. Recent studies have identified that decreased expression of TIP30 is associated with the metastasis of human NSCLCs, but a causative relationship between TIP30 deficiency and NSCLC development remains unclear. We show here that Tip30 deletion leads to spontaneous development of lung adenomas and adenocarcinomas in mice. Lung tumor development was preceded by aberrant expansion of bronchioalveolar stem/progenitor and alveolar type II cells, as well as increased expression of EGFR and its downstream signaling factors in the lung of Tip30^−/− mice. Moreover, TIP30 knockdown in human lung adenocarcinoma cells resulted in prolonged EGFR activity in early endosomes, delayed EGFR degradation, increased EGFR nuclear localization, leading to up-regulated pAKT and pERK1/2 expression. Importantly, in human lung adenocarcinomas, low TIP30 expression correlates with prolonged patient overall and post-progression survival times. Together, these results suggest that TIP30 functions as a tumor suppressor to inhibit EGFR cytoplasmic and nuclear signaling and suppress adenocarcinogenesis in the lung and highlight the potential of therapeutic strategies aiming at inhibiting EGFR signaling for patients with low TIP30 expression lung adenocarcinoma.

Ketones and lactate increase cancer cell "stemness," driving recurrence, metastasis and poor clinical outcome in breast cancer: achieving personalized medicine via Metabolo-Genomics

Previously, we showed that high-energy metabolites (lactate and ketones) "fuel" tumor growth and experimental metastasis in an in vivo xenograft model, most likely by driving oxidative mitochondrial metabolism in breast cancer cells. To mechanistically understand how these metabolites affect tumor cell behavior, here we used genome-wide transcriptional profiling. Briefly, human breast cancer cells (MCF7) were cultured with lactate or ketones, and then subjected to transcriptional analysis (exon-array). Interestingly, our results show that treatment with these high-energy metabolites increases the transcriptional expression of gene profiles normally associated with "stemness," including genes upregulated in embryonic stem (ES) cells. Similarly, we observe that lactate and ketones promote the growth of bonafide ES cells, providing functional validation. The lactate- and ketone-induced "gene signatures" were able to predict poor clinical outcome (including recurrence and metastasis) in a cohort of human breast cancer patients. Taken together, our results are consistent with the idea that lactate and ketone utilization in cancer cells promotes the "cancer stem cell" phenotype, resulting in significant decreases in patient survival. One possible mechanism by which these high-energy metabolites might induce stemness is by increasing the pool of Acetyl-CoA, leading to increased histone acetylation, and elevated gene expression. Thus, our results mechanistically imply that clinical outcome in breast cancer could simply be determined by epigenetics and energy metabolism, rather than by the accumulation of specific "classical" gene mutations. We also suggest that high-risk cancer patients (identified by the lactate/ketone gene signatures) could be treated with new therapeutics that target oxidative mitochondrial metabolism, such as the anti-oxidant and "mitochondrial poison" metformin. Finally, we propose that this new approach to personalized cancer medicine be termed "Metabolo-Genomics," which incorporates features of both 1) cell metabolism and 2) gene transcriptional profiling. Importantly, this powerful new approach directly links cancer cell metabolism with clinical outcome, and new therapeutic strategies for inhibiting the TCA cycle and mitochondrial oxidative phosphorylation in cancer cells.

Metabolic imaging: a link between lactate dehydrogenase A, lactate, and tumor phenotype

PURPOSE

We compared the metabolic profiles and the association between LDH-A expression and lactate production in two isogenic murine breast cancer cell lines and tumors (67NR and 4T1). These cell lines were derived from a single mammary tumor and have different growth and metabolic phenotypes.

EXPERIMENTAL DESIGN

LDH-A expression, lactate concentration, glucose utilization, and oxygen consumption were measured in cells, and the potential relationship between tumor lactate levels [measured by magnetic resonance spectroscopic imaging (MRSI)] and tumor glucose utilization [measured by [(18)F]2-deoxy-2-fluoro-D-glucose positron emission tomography ([(18)F]FDG-PET)] was assessed in orthotopic breast tumors derived from these cell lines.

RESULTS

We show a substantial difference in LDH-A expression between 67NR and 4T1 cells under normoxia and hypoxia. We also show that small orthotopic 4T1 tumors generate 10-fold more lactate than corresponding 67NR tumors. The high lactate levels in small primary 4T1 tumors are associated with intense pimonidazole staining (a hypoxia indicator). Less-intense hypoxia staining was observed in the larger 67NR tumors and is consistent with the gradual increase and plateau of lactate concentration in enlarging 67NR tumors.

CONCLUSIONS

Lactate-MRSI has a greater dynamic range than [(18)F]FDG-PET and may be a more sensitive measure with which to evaluate the aggressive and metastatic potential of primary breast tumors.