A purine nucleotide biosynthesis enzyme guanosine monophosphate reductase is a suppressor of melanoma invasion

Nucleocytoplasmic transport rates are regulated by cellular processes that modulate GTP availability

Nucleocytoplasmic transport (NCT), the facilitated diffusion of cargo molecules between the nucleus and cytoplasm through nuclear pore complexes (NPCs), enables numerous fundamental eukaryotic cellular processes. Ran GTPase uses cellular energy in the direct form of GTP to create a gradient across the nuclear envelope (NE) that drives the majority of NCT. We report here that changes in GTP availability resulting from altered cellular physiology modulate the rate of NCT, as monitored using synthetic and natural cargo, and the dynamics of Ran itself. Cell migration, cell spreading, and/or modulation of the cytoskeleton or its connection to the nucleus alter GTP availability and thus rates of NCT, regulating RNA export and protein synthesis. These findings support a model in which changes in cellular physiology that alter GTP availability can regulate the rate of NCT, impacting fundamental cellular processes that extensively utilize NCT.

Exosome-mediated circGMPS facilitates the development of gastric cancer cells through miR-144-3p/PUM1

In recent years, gastric cancer (GC) is still one of the major public health burdens in the world. It is reported that exosome circular RNA (circRNA) is involved in the GC progression. However, the function and potential mechanism of circGMPS in GC remains unclear and needs further exploration. In this study, we isolated and identified exosomes from serum by TEM, NTA analysis and Western blot. RNA expression was evaluated by qRT-PCR. Western blot was employed to examine protein expression. Cell proliferation was measured using CCK-8. Transwell assay was adopted to analyze cell migration and invasion. The relationship between genes was explored through bioinformatics analysis, dual-luciferase reporter gene assay and spearman correlation coefficient. We found that circGMPS was elevated in GC exosomes, tissues and cells. Poor prognosis of GC patients was related to high circGMPS expression. Both exosome co-culture with cells and insertion of circGMPS clearly promoted cell progression. Mechanically, circGMPS sponged miR-144-3p to regulate PUM1. Inhibition of PUM1 or miR-144-3p overexpression inhibited the malignant GC cell progression. Our data confirmed that exosome-derived circGMPS boosted malignant progression by miR-144-3p/PUM1 axis in GC cells, providing strong evidences for circGMPS as a clinical biomarker of GC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-023-00597-9.

Bacterial therapies at the interface of synthetic biology and nanomedicine

Bacteria are emerging as living drugs to treat a broad range of disease indications. However, the inherent advantages of these replicating and immunostimulatory therapies also carry the potential for toxicity. Advances in synthetic biology and the integration of nanomedicine can address this challenge through the engineering of controllable systems that regulate spatial and temporal activation for improved safety and efficacy. Here, we review recent progress in nanobiotechnology-driven engineering of bacteria-based therapies, highlighting limitations and opportunities that will facilitate clinical translation.

Nucleocytoplasmic transport rates are regulated by cellular processes that modulate GTP availability

Nucleocytoplasmic transport (NCT), the facilitated diffusion of cargo molecules between the nucleus and cytoplasm through nuclear pore complexes (NPCs), enables numerous fundamental eukaryotic cellular processes. Ran GTPase uses cellular energy in the direct form of GTP to create a gradient across the nuclear envelope (NE) that drives the majority of NCT. We report here that changes in GTP availability resulting from altered cellular physiology modulate the rate of NCT, as monitored using synthetic and natural cargo, and the dynamics of Ran itself. Cell migration, cell spreading and/or modulation of the cytoskeleton or its connection to the nucleus alter GTP availability and thus rates of NCT, regulating RNA export and protein synthesis. These findings support a model in which changes in cellular physiology that alter GTP availability can regulate the rate of NCT, impacting fundamental cellular processes that extensively utilize NCT.

Chromosome-level Asian elephant genome assembly and comparative genomics of long-lived mammals reveal the common substitutions for cancer resistance

The naked mole rat (Heterocephalus glaber), bats (e.g., genus Myotis), and elephants (family Elephantidae) are known as long-lived mammals and are assumed to be excellent cancer antagonists. However, whether there are common genetic changes underpinning cancer resistance in these long-lived species is yet to be fully established. Here, we newly generated a high-quality chromosome-level Asian elephant (Elephas maximus) genome and identified that the expanded gene families in elephants are involved in Ras-associated and base excision repair pathways. Moreover, we performed comparative genomic analyses of 12 mammals and examined genes with signatures of positive selection in elephants, naked mole rat, and greater horseshoe bat. Residues at positively selected sites of CDR2L and ALDH6A1 in these long-lived mammals enhanced the inhibition of tumor cell migration compared to those in short-lived relatives. Overall, our study provides a new genome resource and a preliminary survey of common genetic changes in long-lived mammals.

Targeted bacteria-mediated therapy of mouse colorectal cancer using baicalin, a natural glucuronide compound, and E. coli overexpressing β-glucuronidase

The side effects of common chemotherapeutic drugs that damage healthy tissues account for one of the most important problems in cancer research that needs careful addressing. Bacterial-Directed Enzyme Prodrug Therapy (BDEPT) is a promising strategy that uses bacteria to direct a converting enzyme to the tumor site and activate a systemically injected prodrug selectively within the tumor; so that the side effects of the therapy would significantly decrease. In this study, we evaluated the efficacy of baicalin, a natural compound, as a glucuronide prodrug in association with an engineered strain of Escherichia coli DH5α harboring the pRSETB-lux/βG plasmid in a mouse model of colorectal cancer. E. coli DH5α-lux/βG was designed to emit luminescence and overexpress the β-glucuronidase. Unlike the non-engineered bacteria, E. coli DH5α-lux/βG showed the ability to activate baicalin, and the cytotoxic effects of baicalin on the C26 cell line were increased in the presence of E. coli DH5α-lux/βG. Analyzing the tissue homogenates of mice bearing C26 tumors inoculated with E. coli DH5α-lux/βG indicated the specific accumulation and multiplication of bacteria in the tumor tissues. While both baicalin and E. coli DH5α-lux/βG could inhibit tumor growth as monotherapy, an enhanced inhibition was observed when animals were subjected to combination therapy. Moreover, no significant side effects were observed after histological investigation. The results of this study indicate that baicalin has the capability of being used as a suitable prodrug in the BDEPT, however further research is required before it can be applied in the clinic.

LncRNA UCA1 Participates in De Novo Synthesis of Guanine Nucleotides in Bladder Cancer by Recruiting TWIST1 to Increase IMPDH1/2

Metabolic dysregulation has been identified as one of the hallmarks of cancer biology. Based on metabolic heterogeneity between bladder cancer tissues and adjacent tissues, we discovered several potential driving factors for the bladder cancer occurrence and development. Metabolic genomics showed purine metabolism pathway was mainly accumulated in bladder cancer. Long noncoding RNA urothelial carcinoma-associated 1 (LncRNA UCA1) is a potential tumor biomarker for bladder cancer diagnosis and prognosis, and it increases bladder cancer cell proliferation, migration, and invasion via the glycolysis pathway. However, whether UCA1 plays a role in purine metabolism in bladder cancer is unknown. Our findings showed that UCA1 could increase the transcription activity of guanine nucleotide de novo synthesis rate limiting enzyme inosine monophosphate dehydrogenase 1 (IMPDH1) and inosine monophosphate dehydrogenase 2 (IMPDH2), triggering in guanine nucleotide metabolic reprogramming. This process was achieved by UCA1 recruiting the transcription factor TWIST1 which binds to the IMPDH1and IMPDH2 promoter region. Increased guanine nucleotide synthesis pathway products stimulate RNA polymerase-dependent production of pre-ribosomal RNA and GTPase activity in bladder cancer cells, hence increasing bladder cancer cell proliferation, migration, and invasion. We have demonstrated that UCA1 regulates IMPDH1/2-mediated guanine nucleotide production via TWIST1, providing additional evidence of metabolic reprogramming.

Nucleotide metabolism: a pan-cancer metabolic dependency

Metabolic alterations are a key hallmark of cancer cells, and the augmented synthesis and use of nucleotide triphosphates is a critical and universal metabolic dependency of cancer cells across different cancer types and genetic backgrounds. Many of the aggressive behaviours of cancer cells, including uncontrolled proliferation, chemotherapy resistance, immune evasion and metastasis, rely heavily on augmented nucleotide metabolism. Furthermore, most of the known oncogenic drivers upregulate nucleotide biosynthetic capacity, suggesting that this phenotype is a prerequisite for cancer initiation and progression. Despite the wealth of data demonstrating the efficacy of nucleotide synthesis inhibitors in preclinical cancer models and the well-established clinical use of these drugs in certain cancer settings, the full potential of these agents remains unrealized. In this Review, we discuss recent studies that have generated mechanistic insights into the diverse biological roles of hyperactive cancer cell nucleotide metabolism. We explore opportunities for combination therapies that are highlighted by these recent advances and detail key questions that remain to be answered, with the goal of informing urgently warranted future studies.

Deficiency of gluconeogenic enzyme PCK1 promotes metabolic-associated fatty liver disease through PI3K/AKT/PDGF axis activation in male mice

Metabolic associated fatty liver disease (MAFLD) encompasses a broad spectrum of hepatic disorders, including steatosis, nonalcoholic steatohepatitis (NASH) and fibrosis. We demonstrated that phosphoenolpyruvate carboxykinase 1 (PCK1) plays a central role in MAFLD progression. Male mice with liver Pck1 deficiency fed a normal diet displayed hepatic lipid disorder and liver injury, whereas fibrosis and inflammation were aggravated in mice fed a high-fat diet with drinking water containing fructose and glucose (HFCD-HF/G). Forced expression of hepatic PCK1 by adeno-associated virus ameliorated MAFLD in male mice. PCK1 deficiency stimulated lipogenic gene expression and lipid synthesis. Moreover, loss of hepatic PCK1 activated the RhoA/PI3K/AKT pathway by increasing intracellular GTP levels, increasing secretion of platelet-derived growth factor-AA (PDGF-AA), and promoting hepatic stellate cell activation. Treatment with RhoA and AKT inhibitors or gene silencing of RhoA or AKT1 alleviated MAFLD progression in vivo. Hepatic PCK1 deficiency may be important in hepatic steatosis and fibrosis development through paracrine secretion of PDGF-AA in male mice, highlighting a potential therapeutic strategy for MAFLD.

NRF2-directed PRPS1 upregulation to promote the progression and metastasis of melanoma

Phosphoribosyl pyrophosphate synthetase 1 (PRPS1) is the first enzyme in the de novo purine nucleotide synthesis pathway and is essential for cell development. However, the effect of PRPS1 on melanoma proliferation and metastasis remains unclear. This study aimed to investigate the regulatory mechanism of PRPS1 in the malignant progression of melanoma. Here, we found PRPS1 was upregulated in melanoma and melanoma cells. In addition, our data indicated that PRPS1 could promote the proliferation and migration and invasion of melanoma both in vitro and in vivo. PRPS1 also could inhibit melanoma cell apoptosis. Furthermore, we found NRF2 is an upstream transcription factor of PRPS1 that drive malignant progression of melanoma.

Compartmentalization and regulation of GTP in control of cellular phenotypes

Genetic or pharmacological inhibition of enzymes involved in GTP biosynthesis has substantial biological effects, underlining the need to better understand the function of GTP levels in regulation of cellular processes and the significance of targeting GTP biosynthesis enzymes for therapeutic intervention. Our current understanding of spatiotemporal regulation of GTP metabolism and its role in physiological and pathological cellular processes is far from complete. Novel methodologies such as genetically encoded sensors of free GTP offered insights into intracellular distribution and function of GTP molecules. In the current Review, we provide analysis of recent discoveries in the field of GTP metabolism and evaluate the key enzymes as molecular targets.

Proteomic Analysis Reveals Molecular Differences in the Development of Gastric Cancer

Gastric cancer (GC) is the 3rd leading cause of death from cancer and the 5th most common cancer worldwide. The detection rate of GC among Tibetans is significantly higher than that in Han Chinese, probably due to differences in their living habits, dietary structure, and environment. Despite such a high disease burden, the epidemiology of gastric cancer has not been studied in this population. Molecular markers are required to aid the diagnosis and treatment of GC. In this study, we collected gastric tissue samples from patients in Tibet with chronic nonatrophic gastritis (CNAG) (n = 6), chronic atrophic gastritis (CAG) (n = 7), gastric intraepithelial neoplasia (GIN) (n = 4), and GC (n = 5). The proteins in each group were analyzed using coupled label-free mass spectrometry. In addition, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein interaction networks were used to analyze the differentially expressed proteins (DEPs) among groups. DEPs were quantified in comparisons of GC versus CNAG (223), GC versus GIN (100), and GIN versus CNAG (341). GO and KEGG analyses showed that the DEPs were mainly associated with immunity (GC versus CNAG) and cancer proliferation and metastasis (GC versus GIN, and GIN versus CNAG). Furthermore, the expression levels of cell proliferation and cytoskeleton-related proteins increased consistently during cancer development, such as ITGA4, DDC, and CPT1A; thus, they are potential diagnostic markers. These results obtained by proteomics analysis could improve our understanding of cancer biology in GC and provide a rich resource for data mining and discovering potential immunotherapy targets.

miRNA-mRNA associations with inosine monophosphate specific deposition in the muscle of Jingyuan chicken

1. Inosine monophosphate (IMP), is an essential component for meat flavour and microRNAs (miRNAs) play a vital role in its post-transcriptional regulation. However, the mechanism of how miRNA expression affects muscle-specific IMP deposition is unclear.2. The following study performed transcriptome sequencing and bioinformatics analysis of breast and leg muscle, which have significantly different IMP content in Jingyuan chicken. The differential miRNA-mRNAs were screened out and correlation analysis with IMP content was performed.3. A total of 39 differentially expressed miRNAs (DE miRNAs) and 666 differentially expressed mRNAs (DE mRNAs) were identified between breast muscles and leg muscles. Using miRNA-mRNA integrated analysis, 29 miRNA-target gene pairs were obtained, composed of 13 DE miRNAs and 28 DE mRNAs. Next, purine metabolism, glycolysis/gluconeogenesis, pyruvate metabolism and the biosynthesis of amino acid pathways as necessary for muscle IMP-specific deposition were identified. The differentially expressed gene PKM2, which was significantly enriched in all four pathways, is involved in IMP anabolism in the form of energy metabolism and enzyme activity regulation. The correlation analysis suggested that the gga-miR-107-3p-KLHDC2 negative interaction may be a key regulator in IMP deposition.4. This study explores the functional mechanism of IMP-specific deposition in Jingyuan chicken muscles at the miRNA and mRNA levels and highlights multiple candidate miRNAs and mRNAs for molecular-assisted breeding.

Phosphorylation of guanosine monophosphate reductase triggers a GTP-dependent switch from pro- to anti-oncogenic function of EPHA4

Signal transduction pathways post-translationally regulating nucleotide metabolism remain largely unknown. Guanosine monophosphate reductase (GMPR) is a nucleotide metabolism enzyme that decreases GTP pools by converting GMP to IMP. We observed that phosphorylation of GMPR at Tyr267 is critical for its activity and found that this phosphorylation by ephrin receptor tyrosine kinase EPHA4 decreases GTP pools in cell protrusions and levels of GTP-bound RAC1. EPHs possess oncogenic and tumor-suppressor activities, although the mechanisms underlying switches between these two modes are poorly understood. We demonstrated that GMPR plays a key role in EPHA4-mediated RAC1 suppression. This supersedes GMPR-independent activation of RAC1 by EPHA4, resulting in a negative overall effect on melanoma cell invasion and tumorigenicity. Accordingly, EPHA4 levels increase during melanoma progression and inversely correlate with GMPR levels in individual melanoma tumors. Therefore, phosphorylation of GMPR at Tyr267 is a metabolic signal transduction switch controlling GTP biosynthesis and transformed phenotypes.

Identification of Potential Biomarkers and Small Molecule Drugs for Cutaneous Melanoma Using Integrated Bioinformatic Analysis

Background: Cutaneous melanoma (CM) is a type of skin cancer with a high fatality rate, and its pathogenesis has not yet been fully elucidated.

Methods: We obtained the gene expression datasets of CM through the Gene Expression Omnibus (GEO) database. Subsequently, robust rank aggregation (RRA) method was used to identify differentially expressed genes (DEGs) between CM cases and normal skin controls. Gene functional annotation was performed to explore the potential function of the DEGs. We built the protein–protein interaction (PPI) network by the Interactive Gene database retrieval tool (STRING) and selected hub modules by Molecular Complexity Detection (MCODE). We furthered and validated our results using the TCGA-GTEX dataset. Finally, potential small molecule drugs were predicted by CMap database and verified by molecular docking method.

Results: A total of 135 DEGs were obtained by RRA synthesis analysis. GMPR, EMP3, SLC45A2, PDZD2, NPY1R, DLG5 and ADH1B were screened as potential targets for CM. Furazolidone was screened as a potential small molecule drug for the treatment of CM, and its mechanism may be related to the inhibition of CM cell proliferation by acting on GMPR.

Conclusion: We identified seven prognostic therapeutic targets associated with CM and furazolidone could be used as a potential drug for CM treatment, providing new prognostic markers, potential therapeutic targets and small molecule drugs for the treatment and prevention of CM.

Assessment of Intracellular GTP Levels Using Genetically Encoded Fluorescent Sensors

Changes in intracellular GTP levels, even incremental ones, profoundly affect the activity of several GTP-binding proteins ultimately resulting in alteration of several basal cellular phenotypes including cell motility, invasion, and tumorigenesis. However, until recently, no tools were available for GTP quantification in live cells. Therefore, in the current chapter, we describe the methodology for the quantitative assessment of spatiotemporal changes in GTP levels in the cells using genetically encoded fluorescent ratiometric GTP sensors termed GEVALs for GTP evaluators.

Regulation of local GTP availability controls RAC1 activity and cell invasion

Physiological changes in GTP levels in live cells have never been considered a regulatory step of RAC1 activation because intracellular GTP concentration (determined by chromatography or mass spectrometry) was shown to be substantially higher than the in vitro RAC1 GTP dissociation constant (RAC1-GTP Kd). Here, by combining genetically encoded GTP biosensors and a RAC1 activity biosensor, we demonstrated that GTP levels fluctuating around RAC1-GTP Kd correlated with changes in RAC1 activity in live cells. Furthermore, RAC1 co-localized in protrusions of invading cells with several guanylate metabolism enzymes, including rate-limiting inosine monophosphate dehydrogenase 2 (IMPDH2), which was partially due to direct RAC1-IMPDH2 interaction. Substitution of endogenous IMPDH2 with IMPDH2 mutants incapable of binding RAC1 did not affect total intracellular GTP levels but suppressed RAC1 activity. Targeting IMPDH2 away from the plasma membrane did not alter total intracellular GTP pools but decreased GTP levels in cell protrusions, RAC1 activity, and cell invasion. These data provide a mechanism of regulation of RAC1 activity by local GTP pools in live cells.

Changes in intracellular GTP levels are not considered as a regulatory event in RAC1 activation in live cells since total GTP levels are substantially higher than the RAC1 GTP dissociation constant determined in vitro. Here, the authors demonstrate that the availability of free GTP in live cells controls the activity of RAC1 and cell invasion.

Guanosine monophosphate synthase upregulation mediates cervical cancer progression by inhibiting the apoptosis of cervical cancer cells via the Stat3/P53 pathway

Guanosine monophosphate synthase (GMPS) participates in chromatin and gene regulation in multiple types of organisms, and is highly expressed in a variety of human malignancies. The purpose of the present study was to explore the expression of GMPS and its role in cervical cancer (CC), and to provide ideas for improving the clinical efficacy of CC treatment. In the present study, immunohistochemistry, reverse transcription-quantitative PCR analysis, Cell Counting Kit-8 assay, 5-ethynyl-2′-deoxyuridine assay, flow cytometry, western blotting and immunofluorescence assays were conducted to detect the expression of GMPS in normal cervical tissues, CC tissues, para-cancerous tissues and CC cell lines. Moreover, the present study detected the effect of GMPS knockdown on CC cell proliferation, clonal formation ability, aging and apoptosis, as well as on the expression levels of apoptosis-related proteins in tumor cells. The present results demonstrated that the expression level of GMPS in CC was significantly higher compared with that of adjacent tissues; the expression rate of GMPS in CC was 57.36%. GMPS expression was found to successively and gradually increase from that in normal cervical tissues, to that in cervical intraepithelial neoplasia and CC tissues. The abnormal expression of GMPS was positively associated with the degree of CC differentiation and the depth of early invasion. Small interfering (si) RNA knockdown of GMPS inhibited proliferation and colony formation, and promoted aging and apoptosis of CC cells. Furthermore, subcutaneous injection of GMPS-knockdown tumor cells in nude mice resulted in a decrease in the proliferative ability of the tumor. The animal experimental results showed that the tumor growth rate of the short hairpin (sh) RNA-GMPS group was significantly slower than that of the HeLa sh-negative control group. It was identified that GMPS may inhibit CC cell senescence and apoptosis via the Stat3/P53 molecular pathway. Collectively, the present results suggested that GMPS may be a marker of unfavorable prognosis of CC, and it may also be a potential therapeutic target for CC.

Metabolic Compartmentalization at the Leading Edge of Metastatic Cancer Cells

Despite advances in targeted therapeutics and understanding in molecular mechanisms, metastasis remains a substantial obstacle for cancer treatment. Acquired genetic mutations and transcriptional changes can promote the spread of primary tumor cells to distant tissues. Additionally, recent studies have uncovered that metabolic reprogramming of cancer cells is tightly associated with cancer metastasis. However, whether intracellular metabolism is spatially and temporally regulated for cancer cell migration and invasion is understudied. In this review, we highlight the emergence of a concept, termed “membraneless metabolic compartmentalization,” as one of the critical mechanisms that determines the metastatic capacity of cancer cells. In particular, we focus on the compartmentalization of purine nucleotide metabolism (e.g., ATP and GTP) at the leading edge of migrating cancer cells through the uniquely phase-separated microdomains where dynamic exchange of nucleotide metabolic enzymes takes place. We will discuss how future insights may usher in a novel class of therapeutics specifically targeting the metabolic compartmentalization that drives tumor metastasis.

A Prognostic Model Based on Six Metabolism-Related Genes in Colorectal Cancer

An increasing number of studies have shown that abnormal metabolism processes are closely correlated with the genesis and progression of colorectal cancer (CRC). In this study, we systematically explored the prognostic value of metabolism-related genes (MRGs) for CRC patients. A total of 289 differentially expressed MRGs were screened based on The Cancer Genome Atlas (TCGA) and the Molecular Signatures Database (MSigDB), and 72 differentially expressed transcription factors (TFs) were obtained from TCGA and the Cistrome Project database. The clinical samples obtained from TCGA were randomly divided at a ratio of 7 : 3 to obtain the training group (n = 306) and the test group (n = 128). After univariate and multivariate Cox regression analyses, we constructed a prognostic model based on 6 MRGs (AOC2, ENPP2, ADA, GPD1L, ACADL, and CPT2). Kaplan–Meier survival analysis of the training group, validation group, and overall samples proved that the model had statistical significance in predicting the outcomes of patients. Independent prognosis analysis suggested that this risk score might serve as an independent prognosis factor for CRC patients. Moreover, we combined the prognostic model and the clinical characteristics in a nomogram to predict the overall survival of CRC patients. Furthermore, gene set enrichment analysis (GSEA) was conducted to identify the enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in the high- and low-risk groups, which might provide novel therapeutic targets for CRC patients. We discovered through the protein-protein interaction (PPI) network and TF-MRG regulatory network that 7 hub genes were retrieved from the PPI network and 4 kinds of differentially expressed TFs (NR3C1, MYH11, MAF, and CBX7) positively regulated 4 prognosis-associated MRGs (GSTM5, PTGIS, ENPP2, and P4HA3).

Metabolic Traits in Cutaneous Melanoma

Tumor microenvironment is a network of complex cellular and molecular systems where cells will gain specific phenotypes and specific functions that would drive tumorigenesis. In skin cancers, tumor microenvironment is characterized by tumor infiltrating immune cells that sustain immune suppression, mainly lymphocytes. Melanoma cellular heterogeneity can be described on genetic, proteomic, transcriptomic and metabolomic levels. Melanoma cells display a metabolic reprogramming triggered by both genetic alterations and adaptation to a microenvironment that lacks nutrients and oxygen supply. Tumor cells present clear metabolic adaptations and identifying deregulated glycolysis pathway could offer new therapy targets. Moreover, the immune cells (T lymphocytes, macrophages, NK cells, neutrophils and so on) that infiltrate melanoma tumors have metabolic particularities that, upon interaction within tumor microenvironment, would favor tumorigenesis. Analyzing both tumor cell metabolism and the metabolic outline of immune cells can offer innovative insights in new therapy targets and cancer therapeutical approaches. In addition to already approved immune- and targeted therapy in melanoma, approaching metabolic check-points could improve therapy efficacy and hinder resistance to therapy.

A co-expressed gene status of adenylate kinase 1/4 reveals prognostic gene signature associated with prognosis and sensitivity to EGFR targeted therapy in lung adenocarcinoma

Cancer cells utilize altered bioenergetics to fuel uncontrolled proliferation and progression. At the core of bioenergetics, adenine nucleotides are the building blocks for nucleotide synthesis, energy transfer and diverse metabolic processes. Adenylate kinases (AK) are ubiquitous phosphotransferases that catalyze the conversion of adenine nucleotides and regulate the homeostasis of nucleotide ratios within cellular compartments. Recently, different isoforms of AK have been shown to induce metabolic reprograming in cancer and were identified as biomarkers for predicting disease progression. Here we aim to systemically analyze the impact of all AK-associated gene signatures on lung adenocarcinoma patient survival and decipher the value for therapeutic interventions. By analyzing TCGA Lung Adenocarcinoma (LUAD) RNA Seq data, we found gene signatures from AK4 and AK1 have higher percentage of prognostic genes compared to other AK-gene signatures. A 118-gene signature was identified from consensus gene expression in AK1 and AK4 prognostic gene signatures. Immunohistochemistry (IHC) analyses in 140 lung adenocarcinoma patients showed overexpression of AK4 significantly correlated with worse overall survival (P = 0.001) whereas overexpression of AK1 significantly associated with good prognosis (P = 0.009). Furthermore, reduced AK4 expression by shRNA reduced the EGFR protein expression in EGFR mutation cells. The inhibition of AK4-AK1 signal might provide a potential target for synergistic effect in target therapy in lung cancer patients.

The Mechanism of the Selective Antiproliferation Effect of Guanine-Based Biomolecules and Its Compensation

As endogenous biomolecules, guanine, guanine-based nucleosides, and nucleotides are essential for cellular DNA/RNA synthesis, energy metabolism, and signal transduction. However, these biomolecules have been found to have a cell-specific antiproliferation effect at higher concentrations, and the mechanism is unclear. In this study, we demonstrate that guanine deaminase (GDA) is a major factor in determining the cell-type selectivity to the antiproliferation effect of guanine-based biomolecules. GDA catalyzes the deamination of guanine to xanthine, which is an essential part of the guanine degradation pathway. GDA deficient cells could not efficiently remove the excess guanine-based biomolecules. These excess molecules disturb the metabolism of adenine-, cytosine-, and thymine-based nucleotides; subsequently inhibit the DNA synthesis and cell growth; and eventually result in the apoptosis/death of GDA deficient cells. The inhibition of DNA synthesis could be relieved by simultaneous addition of adenine- and cytosine-based nucleosides, and the inhibited DNA synthesis could be restarted by post addition of them, which subsequently reduces the antiproliferation effect of guanine-based biomolecules or even totally restores the cell proliferation. These results provide important information for the development of guanine-based drugs or guanine-rich oligonucleotide drugs, as well as for the safety evaluation of food with a high level of guanine-based compounds.

Network-based integrated analysis of omics data reveal novel players of TGF-β1-induced EMT in human peritoneal mesothelial cells

Long-term peritoneal dialysis is associated with progressive fibrosis of the peritoneum. Epithelial-mesenchymal transition (EMT) of mesothelial cells is an important mechanism involved in peritoneal fibrosis, and TGF-β1 is considered central in this process. However, targeting currently known TGF-β1-associated pathways has not proven effective to date. Therefore, there are still gaps in understanding the mechanisms underlying TGF-β1-associated EMT and peritoneal fibrosis. We conducted network-based integrated analysis of transcriptomic and proteomic data to systemically characterize the molecular signature of TGF-β1-stimulated human peritoneal mesothelial cells (HPMCs). To increase the power of the data, multiple expression datasets of TGF-β1-stimulated human cells were employed, and extended based on a human functional gene network. Dense network sub-modules enriched with differentially expressed genes by TGF-β1 stimulation were prioritized and genes of interest were selected for functional analysis in HPMCs. Through integrated analysis, ECM constituents and oxidative stress-related genes were shown to be the top-ranked genes as expected. Among top-ranked sub-modules, TNFAIP6, ZC3H12A, and NNT were validated in HPMCs to be involved in regulation of E-cadherin, ZO-1, fibronectin, and αSMA expression. The present data shows the validity of network-based integrated analysis in discovery of novel players in TGF-β1-induced EMT in peritoneal mesothelial cells, which may serve as new prognostic markers and therapeutic targets for peritoneal dialysis patients.

Inducibly decreased MITF levels do not affect proliferation and phenotype switching but reduce differentiation of melanoma cells

Melanoma arises from neural crest-derived melanocytes which reside mostly in the skin in an adult organism. Epithelial-mesenchymal transition (EMT) is a tumorigenic programme through which cells acquire mesenchymal, more pro-oncogenic phenotype. The reversible phenotype switching is an event still not completely understood in melanoma. The EMT features and increased invasiveness are associated with lower levels of the pivotal lineage identity maintaining and melanoma-specific transcription factor MITF (microphthalmia-associated transcription factor), whereas increased proliferation is linked to higher MITF levels. However, the precise role of MITF in phenotype switching is still loosely characterized. To exclude the changes occurring upstream of MITF during MITF regulation in vivo, we employed a model whereby MITF expression was inducibly regulated by shRNA in melanoma cell lines. We found that the decrease in MITF caused only moderate attenuation of proliferation of the whole cell line population. Proliferation was decreased in five of 15 isolated clones, in three of them profoundly. Reduction in MITF levels alone did not generally produce EMT-like characteristics. The stem cell marker levels also did not change appreciably, only a sharp increase in SOX2 accompanied MITF down-regulation. Oppositely, the downstream differentiation markers and the MITF transcriptional targets melastatin and tyrosinase were profoundly decreased, as well as the downstream target livin. Surprisingly, after the MITF decline, invasiveness was not appreciably affected, independently of proliferation. The results suggest that low levels of MITF may still maintain relatively high proliferation and might reflect, rather than cause, the EMT-like changes occurring in melanoma.

Control of Nucleotide Metabolism Enables Mutant p53's Oncogenic Gain-of-Function Activity

Since its discovery as an oncoprotein in 1979, investigation into p53's many identities has completed a full circle and today it is inarguably the most extensively studied tumor suppressor (wild-type p53 form or WTp53) and oncogene (mutant p53 form or mtp53) in cancer research. After the p53 protein was declared "Molecule of the Year" by Science in 1993, the p53 field exploded and a plethora of excellent reviews is now available on every aspect of p53 genetics and functional repertoire in a cell. Nevertheless, new functions of p53 continue to emerge. Here, we discuss a novel mechanism that contributes to mtp53's Gain of Functions GOF (gain-of-function) activities and involves the upregulation of both nucleotide de novo synthesis and nucleoside salvage pathways.

Internally ratiometric fluorescent sensors for evaluation of intracellular GTP levels and distribution

GTP is a major regulator of multiple cellular processes, but tools for quantitative evaluation of GTP levels in live cells have not been available. We report the development and characterization of genetically encoded GTP sensors, which we constructed by inserting a circularly permuted yellow fluorescent protein (cpYFP) into a region of the bacterial G protein FeoB that undergoes a GTP-driven conformational change. GTP binding to these sensors results in a ratiometric change in their fluorescence, thereby providing an internally normalized response to changes in GTP levels while minimally perturbing those levels. Mutations introduced into FeoB to alter its affinity for GTP created a series of sensors with a wide dynamic range. Critically, in mammalian cells the sensors showed consistent changes in ratiometric signal upon depletion or restoration of GTP pools. We show that these GTP evaluators (GEVALs) are suitable for detection of spatiotemporal changes in GTP levels in living cells and for high-throughput screening of molecules that modulate GTP levels.

Solid tumors provide niche-specific conditions that lead to preferential growth of Salmonella

Therapeutic attenuated strains of Salmonella Typhimurium target and eradicate tumors in mouse models. However, the mechanism of S. Typhimurium for tumor targeting is still poorly understood. We performed a high-throughput screening of single-gene deletion mutants of S. Typhimurium in an orthotopic, syngeneic murine mammary model of breast cancer. The mutants under selection in this system were classified into functional categories to identify bacterial processes involved in Salmonella accumulation within tumors. Niche-specific genes involved in preferential tumor colonization were identified and exemplars were confirmed by competitive infection assays. Our results show that the chemotaxis gene cheY and the motility genes motAB confer an advantage for colonization of Salmonella within orthotopic syngeneic breast tumors. In addition, eutC, a gene belonging to the ethanolamine metabolic pathway, also confers an advantage for Salmonella within tumors, perhaps by exploiting either ethanolamine or an alternative nutrient in the inflamed tumor environment.

Metabolic rewiring in melanoma

Oncogene-driven metabolic rewiring is an adaptation to low nutrient and oxygen conditions in the tumor microenvironment that enables cancer cells of diverse origin to hyperproliferate. Aerobic glycolysis and enhanced reliance on glutamine utilization are prime examples of such rewiring. However, tissue of origin as well as specific genetic and epigenetic changes determines gene expression profiles underlying these metabolic alterations in specific cancers. In melanoma, activation of the mitogen-activated protein kinase (MAPK) pathway driven by mutant BRAF or NRAS is a primary cause of malignant transformation. Activity of the MAPK pathway, as well as other factors, such as HIF1α, Myc and MITF, are among those that control the balance between non-oxidative and oxidative branches of central carbon metabolism. Here, we discuss the nature of metabolic alterations that underlie melanoma development and affect its response to therapy.

Microphthalmia-associated transcription factor suppresses invasion by reducing intracellular GTP pools

Melanoma progression is associated with increased invasion and, often, decreased levels of microphthalmia-associated transcription factor (MITF). Accordingly, downregulation of MITF induces invasion in melanoma cells, however little is known about the underlying mechanisms. Here, we report for the first time that depletion of MITF results in elevation of intracellular GTP levels and increased amounts of active (GTP-bound) RAC1, RHO-A and RHO-C. Concomitantly, MITF-depleted cells display larger number of invadopodia and increased invasion. We further demonstrate that the gene for guanosine monophosphate reductase (GMPR) is a direct MITF target, and that the partial repression of GMPR accounts mostly for the above phenotypes in MITF-depleted cells. Reciprocally, transactivation of GMPR is required for MITF-dependent suppression of melanoma cell invasion, tumorigenicity, and lung colonization. Moreover, loss of GMPR accompanies downregulation of MITF in vemurafenib-resistant BRAF^V600E-melanoma cells and underlies the increased invasion in these cells. Our data uncover novel mechanisms linking MITF-dependent inhibition of invasion to suppression of guanylate metabolism.

The raspberry Gene Is Involved in the Regulation of the Cellular Immune Response in Drosophila melanogaster

Drosophila is an extremely useful model organism for understanding how innate immune mechanisms defend against microbes and parasitoids. Large foreign objects trigger a potent cellular immune response in Drosophila larva. In the case of endoparasitoid wasp eggs, this response includes hemocyte proliferation, lamellocyte differentiation and eventual encapsulation of the egg. The encapsulation reaction involves the attachment and spreading of hemocytes around the egg, which requires cytoskeletal rearrangements, changes in adhesion properties and cell shape, as well as melanization of the capsule. Guanine nucleotide metabolism has an essential role in the regulation of pathways necessary for this encapsulation response. Here, we show that the Drosophila inosine 5'-monophosphate dehydrogenase (IMPDH), encoded by raspberry (ras), is centrally important for a proper cellular immune response against eggs from the parasitoid wasp Leptopilina boulardi. Notably, hemocyte attachment to the egg and subsequent melanization of the capsule are deficient in hypomorphic ras mutant larvae, which results in a compromised cellular immune response and increased survival of the parasitoid.

The involvement of mutant Rac1 in the formation of invadopodia in cultured melanoma cells

In this article, we discuss the complex involvement of a Rho-family GTPase, Rac1, in cell migration and in invadopodia-mediated matrix degradation. We discuss the involvement of invadopodia in invasive cell migration, and their capacity to promote cancer metastasis. Considering the regulation of invadopodia formation, we describe studies that demonstrate the role of Rac1 in the metastatic process, and the suggestion that this effect is attributable to the capacity of Rac1 to promote invadopodia formation. This notion is demonstrated here by showing that knockdown of Rac1 in melanoma cells expressing a wild-type form of this GTPase, reduces invadopodia-dependent matrix degradation. Interestingly, we also show that excessive activity of Rac1, displayed by the P29S, hyperactive, "fast cycling" mutant of Rac1, which is present in 5-10% of melanoma tumors, inhibits invadopodia function. Moreover, knockdown of this hyperactive mutant enhanced matrix degradation, indicating that excessive Rac1 activity by this mutant can negatively regulate invadopodia formation and function.

Slowing down the Grand Touring Prototype speed of cancer cells

Enzymes involved in de novo production of guanosine triphosphate (GTP) have been recently revealed as integral components of melanoma progression through modulation of the activity of small GTPases. Here, we discuss the biology and therapeutic implications of these findings.

Pharmacological targeting of guanosine monophosphate synthase suppresses melanoma cell invasion and tumorigenicity

Malignant melanoma possesses one of the highest metastatic potentials among human cancers. Acquisition of invasive phenotypes is a prerequisite for melanoma metastases. Elucidation of the molecular mechanisms underlying melanoma invasion will greatly enhance the design of novel agents for melanoma therapeutic intervention. Here, we report that guanosine monophosphate synthase (GMPS), an enzyme required for the de novo biosynthesis of GMP, has a major role in invasion and tumorigenicity of cells derived from either BRAF(V600E) or NRAS(Q61R) human metastatic melanomas. Moreover, GMPS levels are increased in metastatic human melanoma specimens compared with primary melanomas arguing that GMPS is an attractive candidate for anti-melanoma therapy. Accordingly, for the first time we demonstrate that angustmycin A, a nucleoside-analog inhibitor of GMPS produced by Streptomyces hygroscopius efficiently suppresses melanoma cell invasion in vitro and tumorigenicity in immunocompromised mice. Our data identify GMPS as a powerful driver of melanoma cell invasion and warrant further investigation of angustmycin A as a novel anti-melanoma agent.

Regulation of nucleotide metabolism by mutant p53 contributes to its gain-of-function activities

Mutant p53 (mtp53) is an oncogene that drives cancer cell proliferation. Here we report that mtp53 associates with the promoters of numerous nucleotide metabolism genes (NMG). Mtp53 knockdown reduces NMG expression and substantially depletes nucleotide pools, which attenuates GTP dependent protein (GTPase) activity and cell invasion. Addition of exogenous guanosine or GTP restores the invasiveness of mtp53 knockdown cells, suggesting that mtp53 promotes invasion by increasing GTP. Additionally, mtp53 creates a dependency on the nucleoside salvage pathway enzyme deoxycytidine kinase (dCK) for the maintenance of a proper balance in dNTP pools required for proliferation. These data indicate that mtp53 harboring cells have acquired a synthetic sick or lethal phenotype relationship with the nucleoside salvage pathway. Finally, elevated expression of NMG correlates with mutant p53 status and poor prognosis in breast cancer patients. Thus, mtp53’s control of nucleotide biosynthesis has both a driving and sustaining role in cancer development.

A mitochondrial RNAi screen defines cellular bioenergetic determinants and identifies an adenylate kinase as a key regulator of ATP levels

Altered cellular bioenergetics and mitochondrial function are major features of several diseases, including cancer, diabetes, and neurodegenerative disorders. Given this important link to human health, we sought to define proteins within mitochondria that are critical for maintaining homeostatic ATP levels. We screened an RNAi library targeting >1,000 nuclear-encoded genes whose protein products localize to the mitochondria in multiple metabolic conditions in order to examine their effects on cellular ATP levels. We identified a mechanism by which electron transport chain (ETC) perturbation under glycolytic conditions increased ATP production through enhanced glycolytic flux, thereby highlighting the cellular potential for metabolic plasticity. Additionally, we identified a mitochondrial adenylate kinase (AK4) that regulates cellular ATP levels and AMPK signaling and whose expression significantly correlates with glioma patient survival. This study maps the bioenergetic landscape of >1,000 mitochondrial proteins in the context of varied metabolic substrates and begins to link key metabolic genes with clinical outcome.

Pathways and therapeutic targets in melanoma

This review aims to summarize the current knowledge of molecular pathways and their clinical relevance in melanoma. Metastatic melanoma was a grim diagnosis, but in recent years tremendous advances have been made in treatments. Chemotherapy provided little benefit in these patients, but development of targeted and new immune approaches made radical changes in prognosis. This would not have happened without remarkable advances in understanding the biology of disease and tremendous progress in the genomic (and other "omics") scale analyses of tumors. The big problems facing the field are no longer focused exclusively on the development of new treatment modalities, though this is a very busy area of clinical research. The focus shifted now to understanding and overcoming resistance to targeted therapies, and understanding the underlying causes of the heterogeneous responses to immune therapy.