Phosphoribosylpyrophosphate Synthetase Research Articles

Circular RNA circKIF2A Contributes to the Progression of Neuroblastoma Through Regulating PRPS1 Expression by Sponging miR-377-3p.

Neuroblastoma is a malignant tumor originating from the primitive neural crest. Circular RNA (circRNA) KinesinSuperfamily Protein 2A (circKIF2A, also known as hsa_circ_0129276) has been reported to be upregulated in neuroblastoma. However, the molecular mechanism of circKIF2A participated in neuroblastoma is poorly defined. We analyzed the expression levels of circKIF2A, microRNA-377-3p (miR-377-3p), and phosphoribosyl pyrophosphate synthetase 1 (PRPS1) in neuroblastoma tissues and cell lines (SK-N-AS and LAN-6) and explored their roles. The expression levels of CircKIF2A and PRPS1 were increased and that of miR-377-3p were decreased in 21 neuroblastoma tissues and cells. Functionally, the silencing of circKIF2A inhibited cell proliferation, migration, invasion, and glycolysis, boosted apoptosis in neuroblastoma cells in vitro, and blocked the growth of subcutaneously transplanted tumors in nude mice. Mechanically, circKIF2A could work as a sponge of miR-377-3p to enhance PRPS1 expression. CircKIF2A knockdown impedes cell proliferation, metastasis, and glycolysis partly by regulating the miR-377-3p/PRPS1 axis, suggesting that targeting circKIF2A can be a feasible therapeutic strategy for neuroblastoma.

Exploration of the Effect on Genome-Wide DNA Methylation by miR-143 Knock-Out in Mice Liver.

MiR-143 play an important role in hepatocellular carcinoma and liver fibrosis via inhibiting hepatoma cell proliferation. DNA methyltransferase 3 alpha (DNMT3a), as a target of miR-143, regulates the development of primary organic solid tumors through DNA methylation mechanisms. However, the effect of miR-143 on DNA methylation profiles in liver is unclear. In this study, we used Whole-Genome Bisulfite Sequencing (WGBS) to detect the differentially methylated regions (DMRs), and investigated DMR-related genes and their enriched pathways by miR-143. We found that methylated cytosines increased 0.19% in the miR-143 knock-out (KO) liver fed with high-fat diet (HFD), compared with the wild type (WT). Furthermore, compared with the WT group, the CG methylation patterns of the KO group showed lower CG methylation levels in CG islands (CGIs), promoters and hypermethylation in CGI shores, 5′UTRs, exons, introns, 3′UTRs, and repeat regions. A total of 984 DMRs were identified between the WT and KO groups consisting of 559 hypermethylation and 425 hypomethylation DMRs. Furthermore, DMR-related genes were enriched in metabolism pathways such as carbon metabolism (serine hydroxymethyltransferase 2 (Shmt2), acyl-Coenzyme A dehydrogenase medium chain (Acadm)), arginine and proline metabolism (spermine synthase (Sms), proline dehydrogenase (Prodh2)) and purine metabolism (phosphoribosyl pyrophosphate synthetase 2 (Prps2)). In summary, we are the first to report the change in whole-genome methylation levels by miR-143-null through WGBS in mice liver, and provide an experimental basis for clinical diagnosis and treatment in liver diseases, indicating that miR-143 may be a potential therapeutic target and biomarker for liver damage-associated diseases and hepatocellular carcinoma.

A Novel PRPS1 Mutation in a Japanese Patient with CMTX5

The PRPS1 gene encodes phosphoribosyl pyrophosphate synthetase 1 (PRS-1). The phenotypes associated with PRPS1 mutations include DFN2 (mild PRS-1 deficiency), X-linked Charcot-Marie-Tooth disease type 5 (CMTX5) (moderate PRS-1 deficiency), Arts syndrome (severe PRS-1 deficiency), and PRS-1 superactivity1. CMTX5 is a very rare hereditary neuropathy characterized by deafness, optic atrophy, and polyneuropathy. We herein report a Japanese patient with CMTX5 who had a novel hemizygous mutation c.82 G>C in PRPS1. Despite showing a typical clinical picture, the decrease in enzyme activity measured in the patient's erythrocytes was milder than in previously reported cases.

Biosynthesis of a Therapeutically Important Nicotinamide Mononucleotide through a Phosphoribosyl Pyrophosphate Synthetase 1 and 2 Engineered Strain of Escherichia coli.

Nicotinamide mononucleotide (NMN), a precursor of NAD+, can be synthesized by the conversion of nicotinamide with the help of nicotinamide phosphoribosyl transferase (NAMPT) via the salvage pathway. NMN has recently gained great attention as an excellent therapeutic option due to its long-term effective pharmacological activities. In this study, we constructed a recombinant strain of Escherichia coli by inserting NAMPT and phosphoribosyl pyrophosphate synthetase 1 (PRPS1) and PRPS2 (from Homo sapiens) genes to investigate the effect of PRPS1 and PRPS2 on NMN synthesis. The metabolically engineered strain of E. coli BL21 (DE3) exhibited 1.57 mM NMN production in the presence of Mg2+ and phosphates in batch fermentation studies. For further improvement in NMN production levels, effects of different variables were studied using a response surface methodology approach. A significant increment was achieved with a maximum of 2.31 mM NMN production when supplemented with 1% ribose, 1 mM Mg2+ and phosphate, and 0.5% nicotinamide in the presence of a lactose (1%) inducer. Additionally, insertion of the PRPS1 and PRPS2 genes in the phosphoribosyl pyrophosphate synthesis pathway and individual gene expression studies facilitated a higher NMN production at the intracellular level than the reported studies. The strain exhibited intracellular production of NMN from cheap substrates such as glucose, lactose, and nicotinamide. Hence, the overall optimized process can be further scaled up for the economical production of NMN using a recombinant strain of E. coli BL21 (DE3), which is the future perspective of the current study.

Eurycomanol alleviates hyperuricemia by promoting uric acid excretion and reducing purine synthesis

BackgroundAn elevated level of blood uric acid (UA) leads to serious damages to human health. In clinic, xanthine oxidase inhibitor is commonly used to reduce uric acid production. However, UA excretion promotion drug is rare. Our previous study demonstrated that the 70% ethanolic extract of stem of Eurycoma longifolia could effectively increase UA excretion and decrease blood level of UA in hyperuricemia animal model. In this paper, we tried to find active substance on UA regulation from E. longifolia. MethodsThe constituents of stem from E. longifolia were isolated and analyzed by chemical and spectral methods. Ultra Performance Liquid Chromatography was applied to measure the concentrations of UA in serum and urine. H&E staining was used to characterize renal histopathological changes. The protein and mRNA expressions of UA transporters were measured by western blot and quantitative real-time PCR analysis. ResultsTen kinds of quassinoids were isolated from stem of E. longifolia, and the structures were identified. Pharmacological research revealed the major component, eurycomanol (5–20 mg/kg, p.o.) significantly decreased serum UA level and increased 24 h clearance of uric acid in potassium oxonate and adenine induced hyperuricemic mice. Eurycomanol ameliorated UA induced kidney histological injury, inhibited hepatic purine synthesis through decreasing phosphoribosyl pyrophosphate synthetase, promoted UA excretion by modulation of renal and intestinal urate transporters, such as GLUT9, ABCG2, OAT1, and NPT1. ConclusionThe results showed eurycomanol from E. longifolia can promote UA excretion through kidney and intestine, decrease hepatic purine synthesis and further keep UA homeostasis, suggesting that eurycomanol has the potential to be developed into a novel drug for the treatment of under-excretion type hyperuricemia.

Comparison of Spatial Structures and Packaging of Phosphorybosil Pyrophosphate Synthetase 2 from Thermus thermophilus HB27 in Rhombohedral and Tetragonal Crystals

We report the spatial structure of phosphoribosyl pyrophosphate synthetase 2 from the thermophilic bacterium Thermus thermophilus HB27 (TthPRPPS2) obtained at a 1.85 Å resolution using a diffraction set collected from rhombohedral crystals (space group R32-h), grown with lithium sulfate as a precipitant. This crystal structure was compared with the structure of TthPRPPS2, previously obtained at a 2.2 Å resolution using diffraction sets from the tetragonal crystals (space group P41212), grown with ammonium sulfate as a precipitant. The comparison of these structures allows the study of the differences between protein molecules in both crystalline structures, as well as the packaging of enzyme molecules in crystals of both spatial groups. Our results may contribute to the research of the structural basis of catalytic activity and substrate specificity of this enzyme.

Mechanosensitive turnover of phosphoribosyl pyrophosphate synthetases regulates nucleotide metabolism.

Cells coordinate their behaviors with the mechanical properties of the extracellular matrix (ECM). Tumor cells frequently harbor an enhanced nucleotide synthesis, presumably to meet the increased demands for rapid proliferation. Nevertheless, how ECM rigidity regulates nucleotide metabolism remains elusive. Here we show that shift from stiff to soft matrix blunts glycolysis-derived nucleotide synthesis in tumor cells. Soft ECM results in TNF receptor-associated factor 2 (TRAF2)-dependent K29 ubiquitination and degradation of phosphoribosyl pyrophosphate synthetase (PRPS)1/2. Recruitment of TRAF2 to PRPS1/2 requires phosphorylation of PRPS1 S285 or PRPS2 T285, which is mediated by low stiffness-activated large tumor suppressor (LATS)1/2 kinases. Further, non-phosphoryable or non-ubiquitinatable PRPS1/2 mutations maintain PRPS1/2 expression and nucleotide synthesis at low stiffness, and promote tumor growth and metastasis. Our findings demonstrate that PRPS1/2 stability and nucleotide metabolism is ECM rigidity-sensitive, and thereby highlight a regulatory cascade underlying mechanics-guided tumor metabolism reprogramming.

Innate immune response orchestrates phosphoribosyl pyrophosphate synthetases to support DNA repair

Ionizing radiation-induced DNA damages cause genome instability and are highly cytotoxic. Deoxyribonucleotide metabolism provides building blocks for DNA repair. Nevertheless, how deoxyribonucleotide metabolism is timely regulated to coordinate with DNA repair remains elusive. Here, we show that ionizing radiation results in TBK1-mediated phosphorylation of phosphoribosyl pyrophosphate synthetase (PRPS)1/2 at T228, thereby enhancing PRPS1/2 catalytic activity and promoting deoxyribonucleotide synthesis. DNA damage-elicited activation of cGAS/STING axis and ATM-mediated PRPS1/2 S16 phosphorylation are required for PRPS1/2 T228 phosphorylation under ionizing radiation. Furthermore, T228 phosphorylation overrides allosteric regulator-mediated effects and preserves PRPS1/2 with high activity. The expression of non-phosphorylatable PRPS1/2 mutants or inhibition of cGAS/STING axis counteracts ionizing radiation-induced PRPS1/2 activation, deoxyribonucleotide synthesis, and DNA repair, and further impairs cell viability. This study highlights a novel and important mechanism underlying an innate immune response-guided deoxyribonucleotide metabolism, which supports DNA repair.

PRPS2 Enhances Resistance to Cisplatin via Facilitating Exosomes-mediated Macrophage M2 Polarization in Non-small Cell Lung Cancer

ABSTRACT Background: Phosphoribosyl pyrophosphate synthetases 2 (PRPS2) is reported as an oncogene in various cancers. However, the role of PRPS2 in cisplatin (DDP) resistance of non-small cell lung cancer (NSCLC) remains unclear. The present study aimed to explore the effect of PRPS2 in DDP resistance of NSCLC. Methods: mRNA expression levels of genes were detected by RT-PCR. Enzyme-linked immunosorbent assay (ELISA) and Western blot were used to detect protein expression levels. Cell viability was determined by the MTT assay and colony formation assay. Cell apoptosis was detected using nucleosome ELISA assay and caspase-3 activity assay. PRPS2 silencing was achieved using siRNA transfection. Exosomes of cultured cells were isolated through ultracentrifugation. Results: Elevated PRPS2 was correlated with DDP resistance and poor prognosis in NSCLC patients. PRPS2 silencing enhanced sensitivity of DDP-resistant cells to DDP treatment. NSCLC cell-derived exosome induced M2 macrophage polarization. PRPS2 was enriched in the exosomes of NSCLC cells. Exosomal PRPS2 mediated M2 macrophage polarization to promote DDP resistance of NSCLC cells. Conclusions: In conclusion, PRPS2 potentiates resistance to DDP by promoting exosome-mediated macrophage M2 polarization in NSCLC.

LncRNA DLEU1 Contributes to the Growth and Invasion of Colorectal Cancer via Targeting miR-320b/PRPS1.

Growing evidences suggest that long non-coding RNAs (lncRNAs) are closely correlated to the development of human cancer, such as colorectal cancer (CRC). A previous report suggested that DLEU1 accelerated CRC development. However, DLEU1’s underlying mechanism in CRC remains unclear. In our study, the level of DLEU1 in CRC tissues is investigated by qRT-PCR. Our data exhibited that DLEU1 level was observably increased in CRC tissues and CRC cell lines and was closely associated with bad prognosis of CRC patients. CRC cell proliferation was repressed by sh-LncRNA DLEU1, whereas cell apoptosis was markedly stimulated. Moreover, knockdown of DLEU1 inhibited cell migration and invasion. Mechanistically, through interacting with miR-320b in CRC, DLEU1 promoted the level of PRPS1 which was a target of miR-320b. The rescue experiment confirmed that knockdown of DLEU1 repressed cell proliferation, migration and invasion while stimulated cell apoptosis via miR-320b/phosphoribosyl pyrophosphate synthetase 1 (PRPS1) axis. Meanwhile, the data of xenograft model exhibited that inhibition of DLEU1 suppressed tumor growth in vivo. In summary, DLEU1 knockdown may repress PRPS1 expression via miR-320b, and then repress cell proliferation, migration and invasion while stimulate cell apoptosis. Our research may provide a novel target for the treatment of CRC.

Metabolic supervision by PPIP5K, an inositol pyrophosphate kinase/phosphatase, controls proliferation of the HCT116 tumor cell line

Identification of common patterns of cancer metabolic reprogramming could assist the development of new therapeutic strategies. Recent attention in this field has focused on identifying and targeting signal transduction pathways that interface directly with major metabolic control processes. In the current study we demonstrate the importance of signaling by the diphosphoinositol pentakisphosphate kinases (PPIP5Ks) to the metabolism and proliferation of the HCT116 colonic tumor cell line. We observed reciprocal cross talk between PPIP5K catalytic activity and glucose metabolism, and we show that CRISPR-mediated PPIP5K deletion suppresses HCT116 cell proliferation in glucose-limited culture conditions that mimic the tumor cell microenvironment. We conducted detailed, global metabolomic analyses of wild-type and PPIP5K knockout (KO) cells by measuring both steady-state metabolite levels and by performing isotope tracing experiments. We attribute the growth-impaired phenotype to a specific reduction in the supply of precursor material for de novo nucleotide biosynthesis from the one carbon serine/glycine pathway and the pentose phosphate pathway. We identify two enzymatic control points that are inhibited in the PPIP5K KO cells: serine hydroxymethyltransferase and phosphoribosyl pyrophosphate synthetase, a known downstream target of AMP-regulated protein kinase, which we show is noncanonically activated independently of adenine nucleotide status. Finally, we show the proliferative defect in PPIP5K KO cells can be significantly rescued either by addition of inosine monophosphate or a nucleoside mixture or by stable expression of PPIP5K activity. Overall, our data describe multiple, far-reaching metabolic consequences for metabolic supervision by PPIP5Ks in a tumor cell line.

Role of PRPS2 as a prognostic and therapeutic target in osteosarcoma

AimsOsteosarcoma (OS) is the most common primary malignant tumour of the bone. However, further improvement in survival has not been achieved due to a lack of well-validated prognostic markers and...

TOR coordinates nucleotide availability with ribosome biogenesis in plants.

TARGET OF RAPAMYCIN (TOR) is a conserved eukaryotic Ser/Thr protein kinase that coordinates growth and metabolism with nutrient availability. We conducted a medium-throughput functional genetic screen to discover essential genes that promote TOR activity in plants, and identified a critical regulatory enzyme, cytosolic phosphoribosyl pyrophosphate (PRPP) synthetase (PRS4). PRS4 synthesizes cytosolic PRPP, a key upstream metabolite in nucleotide synthesis and salvage pathways. We found that prs4 knockouts are embryo-lethal in Arabidopsis thaliana, and that silencing PRS4 expression in Nicotiana benthamiana causes pleiotropic developmental phenotypes, including dwarfism, aberrant leaf shape, and delayed flowering. Transcriptomic analysis revealed that ribosome biogenesis is among the most strongly repressed processes in prs4 knockdowns. Building on these results, we discovered that TOR activity is inhibited by chemical or genetic disruption of nucleotide biosynthesis, but that this effect can be reversed by supplying plants with nucleobases. Finally, we show that TOR transcriptionally promotes nucleotide biosynthesis to support the demands of ribosomal RNA synthesis. We propose that TOR coordinates ribosome biogenesis with nucleotide availability in plants to maintain metabolic homeostasis and support growth.

PRPS1-mediated purine biosynthesis is critical for pluripotent stem cell survival and stemness.

Pluripotent stem cells (PSCs) have a unique energetic and biosynthetic metabolism compared with typically differentiated cells. However, the metabolism profiling of PSCs and its underlying mechanism are still unclear. Here, we report PSCs metabolism profiling and identify the purine synthesis enzymes, phosphoribosyl pyrophosphate synthetase 1/2 (PRPS1/2), are critical for PSCs stemness and survival. Ultra-high performance liquid chromatography/mass spectroscopy (UHPLC-MS) analysis revealed that purine synthesis intermediate metabolite levels in PSCs are higher than that in somatic cells. Ectopic expression of PRPS1/2 did not improve purine biosynthesis, drug resistance, or stemness in PSCs. However, knockout of PRPS1 caused PSCs DNA damage and apoptosis. Depletion of PRPS2 attenuated PSCs stemness and assisted PSCs differentiation. Our finding demonstrates that PRPS1/2-mediated purine biosynthesis is critical for pluripotent stem cell stemness and survival.

Recent Advances in Construction of the Efficient Producers of Riboflavin and Flavin Nucleotides (FMN, FAD) in the Yeast Candida famata.

The approaches used by the authors to design the Candida famata strains capable to overproduce riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD) are described. The metabolic engineering approaches include overexpression of SEF1 gene encoding positive regulator of riboflavin biosynthesis, IMH3 (coding for IMP dehydrogenase) orthologs from another species of flavinogenic yeast Debaryomyces hansenii, and the homologous genes RIB1 and RIB7 encoding GTP cyclohydrolase II and riboflavin synthase, the first and the last enzymes of riboflavin biosynthesis pathway, respectively. Overexpression of the abovementioned genes in the genetically stable riboflavin overproducer AF-4 obtained by classical selection resulted in fourfold increase of riboflavin production in shake flask experiments.Overexpression of engineered enzymes phosphoribosyl pyrophosphate synthetase and phosphoribosyl pyrophosphate amidotransferase catalyzing the initial steps of purine nucleotide biosynthesis enhances riboflavin synthesis in the flavinogenic yeast C. famata even more.Recombinant strains of C. famata containing FMN1 gene from D. hansenii encoding riboflavin kinase under control of the strong constitutive TEF1 promoter were constructed. Overexpression of the FMN1 gene in the riboflavin-producing mutant led to the 30-fold increase of the riboflavin kinase activity and 400-fold increase of FMN production in the resulting recombinant strains which reached maximally 318.2mg/L.FAD overproducing strains of C. famata were also constructed. This was achieved by overexpression of FAD1 gene from D. hansenii in C. famata FMN overproducing strain. The 7- to 15-fold increase in FAD synthetase activity as compared to the wild-type strain and FAD accumulation into cultural medium were observed. The maximal FAD titer 451.5mg/L was achieved.

SNHG16 knockdown inhibits tumorigenicity of neuroblastoma in children via miR-15b-5p/PRPS1 axis

Neuroblastoma is an important problem in children. Long noncoding RNAs (lncRNAs) exhibit important roles in tumorigenicity of neuroblastoma. However, the role and mechanism of lncRNA small nucleolar RNA host gene 16 (SNHG16) in neuroblastoma tumorigenicity remain poorly understood. Forty-six neuroblastoma samples and 28 normal tissues were harvested. The levels of SNHG16, microRNA-15b-5p (miR-15b-5p), and phosphoribosyl pyrophosphate synthetase 1 (PRPS1) were detected via quantitative reverse transcription PCR or western blot. Cell proliferation as well as cycle distribution were measured via 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide or flow cytometry. Cell metastasis was investigated via epithelial-mesenchymal transition or transwell assay. The target relationship of miR-15b-5p and SNHG16 or PRPS1 was explored via starBase and dual-luciferase reporter assay. The role of SNHG16 in neuroblastoma in vivo was analyzed using a xenograft model. We found SNHG16 and PRPS1 levels were increased in neuroblastoma tissues and cells. SNHG16 knockdown inhibited cell proliferation, increased the cell cycle distribution at G0/G1 phase, and decreased the cells at S phase. SNHG16 overexpression caused an opposite effect. SNHG16 silence suppressed neuroblastoma cell metastasis. PRPS1 knockdown constrained cell proliferation and metastasis and regulated cell cycle distribution. miR-15b-5p was sponged by SNHG16 and directly targeted PRPS1. miR-15b-5p knockdown or PRPS1 overexpression mitigated the influence of SNHG16 silence on cell cycle, proliferation, and metastasis. SNHG16 knockdown reduced xenograft tumor growth. In conclusion, SNHG16 downregulation suppressed neuroblastoma tumorigenicity by regulating cell cycle, proliferation, and metastasis via miR-15b-5p/PRPS1 axis.

Metabolic interaction between amino acid deprivation and cisplatin synergistically reduces phosphoribosyl-pyrophosphate and augments cisplatin cytotoxicity

Cisplatin is a mainstay of cancer chemotherapy. It forms DNA adducts, thereby activating poly(ADP-ribose) polymerases (PARPs) to initiate DNA repair. The PARP substrate NAD+ is synthesized from 5-phosphoribose-1-pyrophosphate (PRPP), and we found that treating cells for 6 h with cisplatin reduced intracellular PRPP availability. The decrease in PRPP was likely from (1) increased PRPP consumption, because cisplatin increased protein PARylation and PARP1 shRNA knock-down returned PRPP towards normal, and (2) decreased intracellular phosphate, which down-regulated PRPP synthetase activity. Depriving cells of a single essential amino acid decreased PRPP synthetase activity with a half-life of ~ 8 h, and combining cisplatin and amino acid deprivation synergistically reduced intracellular PRPP. PRPP is a rate-limiting substrate for purine nucleotide synthesis, and cisplatin inhibited de novo purine synthesis and DNA synthesis, with amino acid deprivation augmenting cisplatin’s effects. Amino acid deprivation enhanced cisplatin’s cytotoxicity, increasing cellular apoptosis and DNA strand breaks in vitro, and intermittent deprivation of lysine combined with a sub-therapeutic dose of cisplatin inhibited growth of ectopic hepatomas in mice. Augmentation of cisplatin’s biochemical and cytotoxic effects by amino acid deprivation suggest that intermittent deprivation of an essential amino acid could allow dose reduction of cisplatin; this could reduce the drug’s side effects, and allow its use in cisplatin-resistant tumors.

Nucleotide de novo synthesis increases breast cancer stemness and metastasis via cGMP-PKG-MAPK signaling pathway.

Metabolic reprogramming to fulfill the biosynthetic and bioenergetic demands of cancer cells has aroused great interest in recent years. However, metabolic reprogramming for cancer metastasis has not been well elucidated. Here, we screened a subpopulation of breast cancer cells with highly metastatic capacity to the lung in mice and investigated the metabolic alternations by analyzing the metabolome and the transcriptome, which were confirmed in breast cancer cells, mouse models, and patients’ tissues. The effects and the mechanisms of nucleotide de novo synthesis in cancer metastasis were further evaluated in vitro and in vivo. In our study, we report an increased nucleotide de novo synthesis as a key metabolic hallmark in metastatic breast cancer cells and revealed that enforced nucleotide de novo synthesis was enough to drive the metastasis of breast cancer cells. An increased key metabolite of de novo synthesis, guanosine-5'-triphosphate (GTP), is able to generate more cyclic guanosine monophosphate (cGMP) to activate cGMP-dependent protein kinases PKG and downstream MAPK pathway, resulting in the increased tumor cell stemness and metastasis. Blocking de novo synthesis by silencing phosphoribosylpyrophosphate synthetase 2 (PRPS2) can effectively decrease the stemness of breast cancer cells and reduce the lung metastasis. More interestingly, in breast cancer patients, the level of plasma uric acid (UA), a downstream metabolite of purine, is tightly correlated with patient’s survival. Our study uncovered that increased de novo synthesis is a metabolic hallmark of metastatic breast cancer cells and its metabolites can regulate the signaling pathway to promote the stemness and metastasis of breast cancer.

KHK-A promotes the proliferation of oesophageal squamous cell carcinoma through the up-regulation of PRPS1

Background and study aimsThe metabolism of dietary fructose by ketohexokinase (KHK) is an important step in glucose metabolism in various tumour types. However, the expression, function and underlying mechanisms of KHK in oesophageal squamous cell carcinoma (ESCC) remain largely unclear. The objective of this study was to investigate the effects of KHK-A, a peripheral isoform of KHK, on the proliferation of ESCC cell lines. Material and methodsThe function and mechanism of KHK-A in ESCC cells were investigated by constructing stable KHK-A-knockdown and -overexpressing ESCC cell lines (KYSE410 and KYSE150, respectively). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry and colony formation assays were used to analyse the effects of KHK-A on cell proliferation, cell cycle and colony formation, respectively. KHK-A and phosphoribosyl pyrophosphate synthetase isoform 1 (PRPS1) mRNA and protein expressions in several ESCC cell lines were determined using routine reverse transcription-polymerase chain reaction and immunoblotting, respectively. KHK and PRPS1 expressions in ESCC tumour tissues and corresponding adjacent non-tumour tissues were evaluated according to the gene expression omnibus (GEO) database (GSE20347). ResultsIn vitro experiments showed that KHK-A significantly promoted cell proliferation by modulating the G1/S phase transition in the cell cycle, which was probably regulated by PRPS1 expression. GEO database-based analysis showed that KHK levels were significantly higher in the ESCC tissues than in the corresponding adjacent non-tumour tissues. Pearson’s correlation coefficient analysis showed that KHK expression in ESCC cell lines and tissues was significantly positively associated with the up-regulation of PRPS1, suggesting that KHK-A levels regulate PRPS1 expression in ESCC. ConclusionKHK-A may serve as a driving gene in ESCC for the activation of PRPS1, resulting in the up-regulation of PRPS1. This could lead to enhanced nucleic acid synthesis for tumourigenesis. Our study showed that KHK-A is a potential target for ESCC diagnosis and therapy.

PRPS1 loss-of-function variants, from isolated hearing loss to severe congenital encephalopathy: New cases and literature review

We describe two sporadic and two familial cases with loss-of-function variants in PRPS1, which is located on the X chromosome and encodes phosphoribosyl pyrophosphate synthetase 1 (PRS-1). We illustrate the clinical variability associated with decreased PRS-1 activity, ranging from mild isolated hearing loss to severe encephalopathy. One of the variants we identified has already been reported with a phenotype similar to our patient's, whereas the other three were unknown. The clinical and biochemical information we provide will hopefully contribute to gain insight into the correlation between genotype and phenotype of this rare condition, both in females and in males. Moreover, our observation of a new family in which hemizygous males display hearing loss without any neurological or ophthalmological symptoms prompts us to suggest analysing PRPS1 in cases of isolated hearing loss. Eventually, PRPS1 variants should be considered as a differential diagnosis of mitochondrial disorders.