Roles of tetrahydrobiopterin in promoting tumor angiogenesis

Photo-Induced Disproportionation-Mediated Photodynamic Therapy: Simultaneous Oxidation of Tetrahydrobiopterin and Generation of Superoxide Radicals

We herein present an approach of photo-induced disproportionation for preparation of Type-I photodynamic agents. As a proof of concept, BODIPY-based photosensitizers were rationally designed and prepared. The photo-induced intermolecular electron transfer between homotypic chromophores leads to the disproportionation reaction, resulting in the formation of charged intermediates, cationic and anionic radicals. The cationic radicals efficiently oxidize the cellularimportant coenzyme, tetrahydrobiopterin (BH4 ), and the anionic radicals transfer electrons to oxygen to produce superoxide radicals (O2 - ⋅). One of our Type-I photodynamic agents not only self-assembles in water but also effectively targets the endoplasmic reticulum. It displayed excellent photocytotoxicity even in highly hypoxic environments (2 % O2 ), with a half-maximal inhibitory concentration (IC50 ) of 0.96 μM, and demonstrated outstanding antitumor efficacy in murine models bearing HeLa tumors.

GTP Cyclohydrolase Drives Breast Cancer Development and Promotes EMT in an Enzyme-Independent Manner

GTP cyclohydrolase (GCH1) is the rate-limiting enzyme for tetrahydrobiopterin (BH4) biosynthesis. The catalysis of BH4 biosynthesis is tightly regulated for physiological neurotransmission, inflammation, and vascular tone. Paradoxically, BH4 has emerged as an oncometabolite regulating tumor growth, but the effects on tumor development remain controversial. Here, we found that GCH1 potentiated the growth of triple-negative breast cancer (TNBC) and HER2+ breast cancer and transformed nontumor breast epithelial cells. Independent of BH4 production, GCH1 protein induced epithelial-to-mesenchymal transition by binding to vimentin (Vim), which was mediated by HSP90. Conversely, GCH1 ablation impaired tumor growth, suppressed Vim in TNBC, and inhibited EGFR/ERK signaling while activating the p53 pathway in estrogen receptor-positive tumor cells. GCH1 deficiency increases tumor cell sensitivity to HSP90 inhibition and endocrine treatments. In addition, high GCH1 correlated with poor breast cancer survival. Together, this study reveals an enzyme-independent oncogenic role of GCH1, presenting it as a potential target for therapeutic development.

SIGNIFICANCE

GTP cyclohydrolase functions as an oncogene in breast cancer and binds vimentin to induce epithelial-to-mesenchymal transition independently of its enzyme activity, which confers targetable vulnerabilities for developing breast cancer treatment strategies.

Possible molecular mechanisms underlying the development of atherosclerosis in cancer survivors

Cancer survivors undergone treatment face an increased risk of developing atherosclerotic cardiovascular disease (CVD), yet the underlying mechanisms remain elusive. Recent studies have revealed that chemotherapy can drive senescent cancer cells to acquire a proliferative phenotype known as senescence-associated stemness (SAS). These SAS cells exhibit enhanced growth and resistance to cancer treatment, thereby contributing to disease progression. Endothelial cell (EC) senescence has been implicated in atherosclerosis and cancer, including among cancer survivors. Treatment modalities for cancer can induce EC senescence, leading to the development of SAS phenotype and subsequent atherosclerosis in cancer survivors. Consequently, targeting senescent ECs displaying the SAS phenotype hold promise as a therapeutic approach for managing atherosclerotic CVD in this population. This review aims to provide a mechanistic understanding of SAS induction in ECs and its contribution to atherosclerosis among cancer survivors. We delve into the mechanisms underlying EC senescence in response to disturbed flow and ionizing radiation, which play pivotal role in atherosclerosis and cancer. Key pathways, including p90RSK/TERF2IP, TGFβR1/SMAD, and BH4 signaling are explored as potential targets for cancer treatment. By comprehending the similarities and distinctions between different types of senescence and the associated pathways, we can pave the way for targeted interventions aim at enhancing the cardiovascular health of this vulnerable population. The insights gained from this review may facilitate the development of novel therapeutic strategies for managing atherosclerotic CVD in cancer survivors.

In Silico Investigation of the Human GTP Cyclohydrolase 1 Enzyme Reveals the Potential of Drug Repurposing Approaches towards the Discovery of Effective BH4 Therapeutics

The GTP cyclohydrolase 1 enzyme (GTPCH1) is the rate-limiting enzyme of the tetrahydrobiopterin (BH₄) biosynthetic pathway. Physiologically, BH₄ plays a crucial role as an essential cofactor for the production of catecholamine neurotransmitters, including epinephrine, norepinephrine and dopamine, as well as the gaseous signaling molecule, nitric oxide. Pathological levels of the cofactor have been reported in a number of disease states, such as inflammatory conditions, neuropathic pain and cancer. Targeting the GTPCH1 enzyme has great potential in the management of a number of disease pathologies associated with dysregulated BH₄ physiology. This study is an in silico investigation of the human GTPCH1 enzyme using virtual screening and molecular dynamic simulation to identify molecules that can be repurposed to therapeutically target the enzyme. A three-tier molecular docking protocol was employed in the virtual screening of a comprehensive library of over 7000 approved medications and nutraceuticals in order to identify hit compounds capable of binding to the GTPCH1 binding pocket with the highest affinity. Hit compounds were further verified by molecular dynamic simulation studies to provide a detailed insight regarding the stability and nature of the binding interaction. In this study, we identify a number of drugs and natural compounds with recognized anti-inflammatory, analgesic and cytotoxic effects, including the aminosalicylate olsalazine, the antiepileptic phenytoin catechol, and the phlorotannins phlorofucofuroeckol and eckol. Our results suggest that the therapeutic and clinical effects of hit compounds may be partially attributed to the inhibition of the GTPCH1 enzyme. Notably, this study offers an understanding of the off-target effects of a number of compounds and advocates the potential role of aminosalicylates in the regulation of BH₄ production in inflammatory disease states. It highlights an in silico drug repurposing approach to identify a potential means of safely targeting the BH₄ biosynthetic pathway using established therapeutic agents.

Harnessing oxidative stress for anti-glioma therapy

Glioma cells use intermediate levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) for growth and invasion, and suppressing these reactive molecules thus may compromise processes that are vital for glioma survival. Increased oxidative stress has been identified in glioma cells, in particular in glioma stem-like cells. Studies have shown that these cells harbor potent antioxidant defenses, although endogenous protection against nitrosative stress remains understudied. The enhancement of oxidative or nitrosative stress offers a potential target for triggering glioma cell death, but whether oxidative and nitrosative stresses can be combined for therapeutic effects requires further research. The optimal approach of harnessing oxidative stress for anti-glioma therapy should include the induction of free radical-induced oxidative damage and the suppression of antioxidant defense mechanisms selectively in glioma cells. However, selective induction of oxidative/nitrosative stress in glioma cells remains a therapeutic challenge, and research into selective drug delivery systems is ongoing. Because of multifactorial mechanisms of glioma growth, progression, and invasion, prospective oncological therapies may include not only therapeutic oxidative/nitrosative stress but also inhibition of oncogenic kinases, antioxidant molecules, and programmed cell death mediators.

Ninety-six-hour starved peripheral blood mononuclear cell supernatant inhibited LA7 breast cancer stem cells induced tumor via reduction in angiogenesis and alternations in Gch1 and Spr expressions

Introduction

The microenvironment of solid tumors such as breast cancer is heterogeneous and complex, containing different types of cell, namely, cancer stem cells and immune cells. We previously reported the immunoregulatory behavior of the human immune cell in a solid tumor microenvironment-like culture under serum starvation stress for 96 h. Here, we examined the effect of this culture-derived solution on breast cancer development in rats.

Method

Ninety-six-hour starved PBMCs supernatant (96 h-SPS) was collected after culturing human PBMCs for 96 h under serum starvation condition. Breast cancer stem cells, LA7 cell line, was used for in vitro study by analyzing gene expression status and performing cytotoxicity, proliferation, scratch wound healing assays, followed by in vivo tumor induction in three groups of mature female Sprague Dawley rats. Animals were treated with 96 h-SPS or RPMI and normal saline as control, n = 6 for each group. After biochemical analysis of iron, lactate, and pH levels in the dissected tumors, Ki67 antigen expression, angiogenesis, and necrosis evaluation were carried out. Metabolic-related gene expression was assessed using RT-qPCR. Moreover, 96 h-SPS composition was discovered by Nano-LC-ESI-MS/MS.

Results

96 h-SPS solution reduced the LA7 cell viability, proliferation, and migration and Gch1 and Spr genes expression in vitro (p< 0.05), whereas stemness gene Oct4 was upregulated (p< 0.01). The intracellular lactate was significantly decreased in the 96 h-SPS treated group (p = 0.007). In this group, Gch1 and Spr were significantly downregulated (p< 0.05), whereas the Sox2 and Oct4 expression was not changed significantly. The number of vessels and mitosis (Ki67⁺ cells) in the 96 h-SPS-treated group was significantly reduced (p = 0.024). The increased rate of necrosis in this group was statistically significant (p = 0.04). Last, proteomics analysis revealed candidate effectors' components of 96 h-SPS solution.

Conclusion

96 h-SPS solution may help to prevent cancer stem cell mediated tumor development. This phenomenon could be mediated through direct cytotoxic effects, inhibition of cell proliferation and migration in association with reduction in Gch1 and Spr genes expression, angiogenesis and mitosis rate, and necrosis augmentation. The preliminary data obtained from the present study need to be investigated on a larger scale and can be used as a pilot for further studies on the biology of cancer development.

The Role of the BH4 Cofactor in Nitric Oxide Synthase Activity and Cancer Progression: Two Sides of the Same Coin

Cancer development is associated with abnormal proliferation, genetic instability, cell death resistance, metabolic reprogramming, immunity evasion, and metastasis. These alterations are triggered by genetic and epigenetic alterations in genes that control cell homeostasis. Increased reactive oxygen and nitrogen species (ROS, RNS) induced by different enzymes and reactions with distinct molecules contribute to malignant transformation and tumor progression by modifying DNA, proteins, and lipids, altering their activities. Nitric oxide synthase plays a central role in oncogenic signaling modulation and redox landscape. Overexpression of the three NOS isoforms has been found in innumerous types of cancer contributing to tumor growth and development. Although the main function of NOS is the production of nitric oxide (NO), it can be a source of ROS in some pathological conditions. Decreased tetrahydrobiopterin (BH4) cofactor availability is involved in NOS dysfunction, leading to ROS production and reduced levels of NO. The regulation of NOSs by BH4 in cancer is controversial since BH4 has been reported as a pro-tumoral or an antitumoral molecule. Therefore, in this review, the role of BH4 in the control of NOS activity and its involvement in the capabilities acquired along tumor progression of different cancers was described.

Operative ubiquitin-specific protease 22 deubiquitination confers a more invasive phenotype to cholangiocarcinoma

Oncogenic ubiquitin-specific protease 22 (USP22) is implicated in a variety of tumours; however, evidence of its role and underlying molecular mechanisms in cholangiocarcinoma (CCA) development remains unknown. We collected paired tumour and adjacent non-tumour tissues from 57 intrahepatic CCA (iCCA) patients and evaluated levels of the USP22 gene and protein by qPCR and immunohistochemistry. Both the mRNA and protein were significantly upregulated, correlated with the malignant invasion and worse OS of iCCA. In cell cultures, USP22 overexpression increased CCA cell proliferation and mobility, and induced epithelial-to-mesenchymal transition (EMT). Upon an interaction, USP22 deubiquitinated and stabilized sirtuin-1 (SIRT1), in conjunction with Akt/ERK activation. In implantation xenografts, USP22 overexpression stimulated tumour growth and metastasis to the lungs of mice. Conversely, the knockdown by USP22 shRNA attenuated the tumour growth and invasiveness in vitro and in vivo. Furthermore, SIRT1 overexpression reversed the USP22 functional deficiency, while the knockdown acetylated TGF-β-activated kinase 1 (TAK1) and Akt. Our present study defines USP22 as a poor prognostic predictor in iCCA that cooperates with SIRT1 and facilitates tumour development.

Integrative Bioinformatics Analysis of iNOS/NOS2 in gastric and colorectal cancer

Objective The aim of the present work was to investigate the expression of nitric oxide synthase 2 (iNOS/ NOS2) in colorectal and gastric cancers and evaluate its association with patient’s prognosis by integrated bioinformatics analysis.

Methods The data for present study was obtained from the TCGA, GTEx, and STRING database. iNOS/NOS2 mRNA expression in normal tissue and colorectal, and gastric cancer tissuea were investigated through the GTEx and TCGA database. iNOS/NOS2 gene mutations and frequency were analyzed in the TCGA database using the cBioPortal online data analysis tool. The protein-protein interaction (PPI) network of iNOS/NOS2 was constructed by STRING database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway of iNOS/NOS2 and relevant proteins involved in the PPI network were enriched and demonstrated by the bubble plot. Comparison of the overall survival(OS) and disease free survival(DFS) between samples expressing high and low levels of iNOS/NOS2 was analysis based on the TCGA databases through the GEPIA online data analysis tool.

Results For colon adenocarcinoma (COAD) and rectal adenocarcinoma(READ) iNOS/NOS2 mRNA expression levels in tumor tissue were significant higher than those of corresponding normal colorectal tissue (p<0.05). iNOS/NOS2 mutations were identified in both colorectal cancer and gastric cancer. Missense substitutions and synonymous substitution were the top two mutation types for colorectal and gastric cancer. The top positive and negative co-expressed genes correlated with iNOS/ NOS2 were TRIM40 (rpearson=0.56, p<0.05) and GDPD5 (rpearson=-0.41, p<0.05) in colorectal cancer respectively andCASP5 (rpearson=0.63,p<0.05) and PIAS3 (rpearson=-0.43,p<0.05) in gastric cancer. Twenty one proteins were included in the PPI network with 51 nodes and 345 edges which indicated the PPI enrichment wassignificant (p=1.0e-16). The KEGG of the included genes were mainly enriched in metabolic pathway and Jak-STAT signaling pathway. There was a significant difference indisease free survival (DFS) between samples expressing high and low iNOS/NOS2 (HR=0.37, p=0.044) in rectal cancer. The difference was not statistical between iNOS/NOS2 high and low expressing groups for overall survival(OS) or DFS in the colon cancer or gastric cancer(p>0.05).

Conclusions iNOS/NOS2 mRNA isup-regulated in tumor tissue compared to corresponding normal tissue in colorectal and gastric cancer which implement it in the development of colorectal and gastric cancers.

Sepiapterin reductase: Characteristics and role in diseases

Sepiapterin reductase, a homodimer composed of two subunits, plays an important role in the biosynthesis of tetrahydrobiopterin. Furthermore, sepiapterin reductase exhibits a wide distribution in different tissues and is associated with many diseases, including brain dysfunction, chronic pain, cardiovascular disease and cancer. With regard to drugs targeting sepiapterin reductase, many compounds have been identified and provide potential methods to treat various diseases. However, the underlying mechanism of sepiapterin reductase in many biological processes is unclear. Therefore, this article summarized the structure, distribution and function of sepiapterin reductase, as well as the relationship between sepiapterin reductase and different diseases, with the aim of finding evidence to guide further studies on the molecular mechanisms and the potential clinical value of sepiapterin reductase. In particular, the different effects induced by the depletion of sepiapterin reductase or the inhibition of the enzyme suggest that the non-enzymatic activity of sepiapterin reductase could function in certain biological processes, which also provides a possible direction for sepiapterin reductase research.

The knockdown of the sepiapterin reductase gene suppresses the proliferation of breast cancer by inducing ROS-mediated apoptosis

BACKGROUND

Sepiapterin reductase (SPR) is an important regulator of the biosynthesis of tetrahydrobiopterin (BH₄), which has been shown to be a promoter of different kinds of tumors. This study aims to investigate the role of SPR in breast cancer and to explore its molecular mechanism.

METHODS

SPR expressions in breast cancer tissues with different pathological stages were compared with the corresponding pericarcinomatous tissues and were analyzed using immunohistochemical staining and western blot. SPR knockdown was performed in MDA-MB-231 and MDA-MB-468 triple-negative breast cancer cells using specific siRNAs. Quantitative real-time PCR and western blot were used to determine the efficiency of the SPR knockdown. The intracellular BH₄ levels were measured using HPLC, and the intracellular ROS levels were measured using an ROS detection kit. Clone formation and cell proliferation assays were used to study the effect of the SPR knockdown on cell proliferation. Annexin V/PI double staining, cell mitochondria isolation, and western blot were performed to study the effect of the SPR knockdown on cell apoptosis. ROS scavenger NAC was used to inhibit increased ROS caused by the SPR knockdown.

RESULTS

SPR is highly expressed in breast cancer tissues compared with the pericarcinomatous tissues and positively correlated with the pathological stages. The knockdown of SPR causes decreased intracellular BH₄ and increased intracellular ROS and inhibits the proliferation of MDA-MB-231 and MDA-MB-468 cells. The knockdown of SPR also induces mitochondrial pathway-mediated apoptosis. NAC suppresses the SPR knockdown-caused cell apoptosis and cell death.

CONCLUSIONS

SPR promotes the proliferation of breast cancer cells. The knockdown of SPR suppresses the proliferation of breast cancer cells by inducing ROS-mediated apoptosis.

Proteomic analysis enables distinction of early- versus advanced-stage lung adenocarcinomas

Background

A gel‐free proteomic approach was utilized to perform in‐depth tissue protein profiling of lung adenocarcinoma (ADC) and normal lung tissues from early and advanced stages of the disease. The long‐term goal of this study is to generate a large‐scale, label‐free proteomics dataset from histologically well‐classified lung ADC that can be used to increase further our understanding of disease progression and aid in identifying novel biomarkers.

Methods and results

Cases of early‐stage (I‐II) and advanced‐stage (III‐IV) lung ADCs were selected and paired with normal lung tissues from 22 patients. The histologically and clinically stratified human primary lung ADCs were analyzed by liquid chromatography‐tandem mass spectrometry. From the analysis of ADC and normal specimens, 4863 protein groups were identified. To examine the protein expression profile of ADC, a peak area‐based quantitation method was used. In early‐ and advanced‐stage ADC, 365 and 366 proteins were differentially expressed, respectively, between normal and tumor tissues (adjusted P‐value < .01, fold change ≥ 4). A total of 155 proteins were dysregulated between early‐ and advanced‐stage ADCs and 18 were suggested as early‐specific stage ADC. In silico functional analysis of the upregulated proteins in both tumor groups revealed that most of the enriched pathways are involved in mRNA metabolism. Furthermore, the most overrepresented pathways in the proteins that were unique to ADC are related to mRNA metabolic processes.

Conclusions

Further analysis of these data may provide an insight into the molecular pathways involved in disease etiology and may lead to the identification of biomarker candidates and potential targets for therapy. Our study provides potential diagnostic biomarkers for lung ADC and novel stage‐specific drug targets for rational intervention.

Sapropterin reduces coronary artery malformation in offspring of pregestational diabetes mice

Endothelial nitric oxide synthase (eNOS) and oxidative stress are critical to embryonic coronary artery development. Maternal diabetes increases oxidative stress and reduces eNOS activity in the fetal heart. Sapropterin (Kuvan®) is an orally active, synthetic form of tetrahydrobiopterin (BH4) and a co-factor for eNOS with antioxidant properties. The aim of the present study was to examine the effects of sapropterin on fetal coronary artery development during pregestational diabetes in mice. Diabetes was induced by streptozotocin to adult female C57BL/6 mice. Sapropterin (10 mg/kg/day) was orally administered to pregnant mice from E0.5 to E18.5. Fetal hearts were collected at E18.5 for coronary artery morphological analysis. Sapropterin treatment to diabetic dams reduced the incidence of coronary artery malformation in offspring from 50.0% to 20.6%. Decreases in coronary artery luminal diameter, volume and abundance in fetal hearts from diabetic mothers, were prevented by sapropterin treatment. Maternal diabetes reduced epicardial epithelial-to-mesenchymal transition (EMT) and expression of transcription and growth factors critical to coronary artery development including hypoxia-inducible factor 1a (Hif1a), Snail1, Slug, β-catenin, retinaldehyde dehydrogenase 2 (Aldh1a2), basic fibroblast growth factor (bFGF) and vascular endothelial group factor receptor 2 (Vegfr2) in E12.5 hearts. Additionally, eNOS phosphorylation was lower while oxidative stress was higher in E12.5 hearts from maternal diabetes. Notably, these abnormalities were all restored to normal levels after sapropterin treatment. In conclusion, sapropterin treatment increases eNOS activity, lowers oxidative stress and reduces coronary artery malformation in offspring of pregestational diabetes. Sapropterin may have therapeutic potential in preventing coronary artery malformation in maternal diabetes.

Epigenetic modifications induced by exercise: Drug-free intervention to improve cognitive deficits associated with obesity

Obesity and metabolic disorders are increasing worldwide and are associated with brain atrophy and dysfunction, which are risk factors for late-onset dementia and Alzheimer's disease. Epidemiological studies demonstrated that changes in lifestyle, including the frequent practice of physical exercise are able to prevent and treat not only obesity/metabolic disorders, but also to improve cognitive function and dementia. Several biochemical pathways and epigenetic mechanisms have been proposed to understand the beneficial effects of physical exercise on cognition. This manuscript revised central ongoing research on epigenetic mechanisms induced by exercise and the beneficial effects on obesity-associated cognitive decline, highlighting potential mechanistic mediators.

Navy Beans Impact the Stool Metabolome and Metabolic Pathways for Colon Health in Cancer Survivors

Colorectal cancer (CRC) is the third leading cause of cancer-related death in the United States and emerging evidence supports that increased consumption of legumes, such as navy beans, can reduce risk. Navy bean consumption was previously shown to modulate host and microbiome metabolism, and this investigation was performed to assess the impact on the human stool metabolome, which includes the presence of navy bean metabolites. This 4-week, randomized-controlled trial with overweight and obese CRC survivors involved consumption of 1 meal and 1 snack daily. The intervention contained 35 g of cooked navy bean or macronutrient matched meals and snacks with 0 g of navy beans for the control group (n = 18). There were 30 statistically significant metabolite differences in the stool of participants that consumed navy bean at day 28 compared to the participants’ baseline (p ≤ 0.05) and 26 significantly different metabolites when compared to the control group. Of the 560 total metabolites identified from the cooked navy beans, there were 237 possible navy bean-derived metabolites that were identified in the stool of participants consuming navy beans, such as N-methylpipecolate, 2-aminoadipate, piperidine, and vanillate. The microbial metabolism of amino acids and fatty acids were also identified in stool after 4 weeks of navy bean intake including cadaverine, hydantoin-5 propionic acid, 4-hydroxyphenylacetate, and caprylate. The stool relative abundance of ophthalmate increased 5.25-fold for navy bean consumers that can indicate glutathione regulation, and involving cancer control mechanisms such as detoxification of xenobiotics, antioxidant defense, proliferation, and apoptosis. Metabolic pathways involving lysine, and phytochemicals were also modulated by navy bean intake in CRC survivors. These metabolites and metabolic pathways represent an acute response to increased navy bean intake, which merit further investigation for improving colonic health after long-term consumption.

Secondary BH4 deficiency links protein homeostasis to regulation of phenylalanine metabolism

Metabolic control of phenylalanine concentrations in body fluids is essential for cognitive development and executive function. The hepatic phenylalanine hydroxylating system is regulated by the ratio of l-phenylalanine, which is substrate of phenylalanine hydroxylase (PAH), to the PAH cofactor tetrahydrobiopterin (BH4). Physiologically, phenylalanine availability is governed by nutrient intake, whereas liver BH4 is kept at constant level. In phenylketonuria, PAH deficiency leads to elevated blood phenylalanine and is often caused by PAH protein misfolding with loss of function. Here, we report secondary hepatic BH4 deficiency in Pah-deficient mice. Alterations in de novo synthesis and turnover of BH4 were ruled out as molecular causes. We demonstrate that kinetically instable and aggregation-prone variant Pah proteins trap BH4, shifting the pool of free BH4 towards bound BH4. Interference of PAH protein misfolding with metabolite-based control of l-phenylalanine turnover suggests a mechanistic link between perturbation of protein homeostasis and disturbed regulation of metabolic pathways.

Upregulation of AUF1 is involved in the proliferation of esophageal squamous cell carcinoma through GCH1

Esophageal squamous cell carcinoma (ESCC) has one of the highest mortality rates worldwide. AU-rich element RNA-binding factor 1 (AUF1) is an established RNA-binding protein. AUF1 influences the process of development, apoptosis and tumorigenesis via interacting with adenylate-uridylate rich elements (AREs) bearing mRNAs. However, the clinical relevance of AUF1 and its biological function in ESCC progression have not been reported. In the present study, we first investigated the expression of AUF1 in the ESCC tissue samles and normal samples. We found a significantly higher expression of AUF1 in ESCC tissues than that in normal tissues and tumor adjacent tissues. The expression of AUF1 correlated with ESCC stage (P=0.011) and marginally correlated with lymph node metastasis (P=0.055) of ESCC patients. Silencing of AUF1 by an siRNA inhibited the proliferation and enhanced the apoptosis of ESCC cells. mRNA profiling by microarray analysis revealed that AUF1 knockdown affected 285 genes (fold change ≥2) that function in multiple pathways. GTP cyclohydrolase I (GCH1), the rate limiting enzyme for BH4 synthesis, was found to be downregulated. One of the AU-rich elements in the 3'UTR of GCH1 was found to be responsive to AUF1 expression by luciferase assay. Knockdown of GCH1 suppressed cell proliferation and colony formation of ESCC cells. The expression of AUF1 significantly correlated with that of GCH1 in ESCC tissues. Taken together, we demonstrated the overexpression of AUF1 in esophageal carcinoma and identified GCH1 as AUF1's effector for the proliferation of ESCC cells.

Downregulation of tetrahydrobiopterin inhibits tumor angiogenesis in BALB/c-nu mice with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly vascular tumor, and treatment options for patients of advanced-stage are limited. Nitric oxide (NO), which is derived from endothelial nitric oxide synthase (eNOS), provides crucial signals for angiogenesis in the tumor microenvironment. Tetrahydrobiopterin (BH4) is an essential cofactor eNOS and represents a critical determinant of NO production. To examine whether treatment of 2,4-diamino-6-hydroxypyrimidine (DAHP) inhibits angiogenesis of HCC, BALB/c-nu mice were injected with HepG-2 cells with DAHP. Supplemental DAHP treatment decreased K-ras mRNA transcripts, inhibition of phosphorylation of eNOS and Akt, inhibition of guanosine triphosphate cyclohydrolase (GTPCH), and decreased significantly NO synthesis, and then inhibited angiogenesis, compared with the results observed in the saline group. Histopathology demonstrated angiogenesis and tumor formation were significantly inhibited in HCC. DAHP downregulates GTPCH protein expression, corresponding to decreased levels of BH4 and the contents of NO. In addition, DAHP downregulates eNOS and Akt protein expression, corresponding to decreased eNOS phosphorylation at Ser1177 and Akt phosphorylation, compared with the saline control. We suggest that DAHP, recognized as a specific competitive inhibitor of GTPCH, can decrease tumor BH4 and NO by the inhibition of the wild-type Ras-PI3K/Akt pathway, and then inhibiting angiogenesis, and may provide a novel and promising way to target BH4 synthetic pathways to inhibit angiogenesis and to control potential progression of HCC. Whether DAHP has a therapeutic potential will require more direct testing in humans.

Paracrine effect of GTP cyclohydrolase and angiopoietin-1 interaction in stromal fibroblasts on tumor Tie2 activation and breast cancer growth

Cancer-associated fibroblasts (CAFs) play a key role in promoting tumor growth, acting through complex paracrine regulation. GTP cyclohydrolase (GTPCH) expression for tetrahydrobiopterin synthesis in tumor stroma is implicated in angiogenesis and tumor development. However, the clinical significance of GTPCH expression in breast cancer is still elusive and how GTPCH regulates stromal fibroblast and tumor cell communication remains unknown. We found that GTPCH was upregulated in breast CAFs and epithelia, and high GTPCH RNA was significantly correlated with larger high grade tumors and worse prognosis. In cocultures, GTPCH expressing fibroblasts stimulated breast cancer cell proliferation and motility, cancer cell Tie2 phosphorylation and consequent downstream pathway activation. GTPCH interacted with Ang-1 in stromal fibroblasts and enhanced Ang-1 expression and function, which in turn phosphorylated tumor Tie2 and induced cell proliferation. In coimplantation xenografts, GTPCH in fibroblasts enhanced tumor growth, upregulating Ang-1 and alpha-smooth muscle actin mainly in fibroblast-like cells. GTPCH inhibition resulted in the attenuation of tumor growth and angiogenesis. GTPCH/Ang-1 interaction in stromal fibroblasts and activation of Tie2 on breast tumor cells could play an important role in supporting breast cancer growth. GTPCH may be an important mechanism of paracrine tumor growth and hence a target for therapy in breast cancer.

Identification of anticancer drugs for hepatocellular carcinoma through personalized genome-scale metabolic modeling

Genome-scale metabolic models (GEMs) have proven useful as scaffolds for the integration of omics data for understanding the genotype-phenotype relationship in a mechanistic manner. Here, we evaluated the presence/absence of proteins encoded by 15,841 genes in 27 hepatocellular carcinoma (HCC) patients using immunohistochemistry. We used this information to reconstruct personalized GEMs for six HCC patients based on the proteomics data, HMR 2.0, and a task-driven model reconstruction algorithm (tINIT). The personalized GEMs were employed to identify anticancer drugs using the concept of antimetabolites; i.e., drugs that are structural analogs to metabolites. The toxicity of each antimetabolite was predicted by assessing the in silico functionality of 83 healthy cell type-specific GEMs, which were also reconstructed with the tINIT algorithm. We predicted 101 antimetabolites that could be effective in preventing tumor growth in all HCC patients, and 46 antimetabolites which were specific to individual patients. Twenty-two of the 101 predicted antimetabolites have already been used in different cancer treatment strategies, while the remaining antimetabolites represent new potential drugs. Finally, one of the identified targets was validated experimentally, and it was confirmed to attenuate growth of the HepG2 cell line.

Inhibition of GTP cyclohydrolase attenuates tumor growth by reducing angiogenesis and M2-like polarization of tumor associated macrophages

GTP cyclohydrolase (GCH1) is the key-enzyme to produce the essential enzyme cofactor, tetrahydrobiopterin. The byproduct, neopterin is increased in advanced human cancer and used as cancer-biomarker, suggesting that pathologically increased GCH1 activity may promote tumor growth. We found that inhibition or silencing of GCH1 reduced tumor cell proliferation and survival and the tube formation of human umbilical vein endothelial cells, which upon hypoxia increased GCH1 and endothelial NOS expression, the latter prevented by inhibition of GCH1. In nude mice xenografted with HT29-Luc colon cancer cells GCH1 inhibition reduced tumor growth and angiogenesis, determined by in vivo luciferase and near-infrared imaging of newly formed blood vessels. The treatment with the GCH1 inhibitor shifted the phenotype of tumor associated macrophages from the proangiogenic M2 towards M1, accompanied with a shift of plasma chemokine profiles towards tumor-attacking chemokines including CXCL10 and RANTES. GCH1 expression was increased in mouse AOM/DSS-induced colon tumors and in high grade human colon and skin cancer and oppositely, the growth of GCH1-deficient HT29-Luc tumor cells in mice was strongly reduced. The data suggest that GCH1 inhibition reduces tumor growth by (i) direct killing of tumor cells, (ii) by inhibiting angiogenesis, and (iii) by enhancing the antitumoral immune response.