Glutaminase regulates glutaminolysis to promote cancer cell proliferation. However, the mechanism underlying glutaminase activity regulation is largely unknown. Here, we demonstrate that kidney-type ...glutaminase (GLS) is highly expressed in human pancreatic ductal adenocarcinoma (PDAC) specimens with correspondingly upregulated glutamine dependence for PDAC cell proliferation. Upon oxidative stress, the succinyl-coenzyme A (CoA) synthetase ADP-forming subunit β (SUCLA2) phosphorylated by p38 mitogen-activated protein kinase (MAPK) at S79 dissociates from GLS, resulting in enhanced GLS K311 succinylation, oligomerization, and activity. Activated GLS increases glutaminolysis and the production of nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione, thereby counteracting oxidative stress and promoting tumor cell survival and tumor growth in mice. In addition, the levels of SUCLA2 pS79 and GLS K311 succinylation, which were mutually correlated, were positively associated with advanced stages of PDAC and poor prognosis for patients. Our findings reveal critical regulation of GLS by SUCLA2-coupled GLS succinylation regulation and underscore the regulatory role of metabolites in glutaminolysis and PDAC development.
•GLS is upregulated in human pancreatic ductal adenocarcinoma•GLS K311 succinylation enhances the oligomerization and activity of GLS•p38-phosphorylated SUCLA2 dissociates from GLS and promotes GLS K311 succinylation•GLS succinylation promotes glutaminolysis and tumor growth
Tong et al. demonstrate that oxidative stress removes GLS-associated SUCLA2 to catalyze succinyl-CoA. This dissociation enhances succinyl-CoA-dependent GLS K311 succinylation and activity, leading to increased production of NADPH and GSH against oxidative-stress-induced ROS production and apoptosis and promoting tumor cell proliferation and tumor growth in mice.
One of the biggest hurdles for the development of metabolism-targeted therapies is to identify the responsive tumor subsets. However, the metabolic vulnerabilities for most human cancers remain ...unclear. Establishing the link between metabolic signatures and the oncogenic alterations of receptor tyrosine kinases (RTK), the most well-defined cancer genotypes, may precisely direct metabolic intervention to a broad patient population. By integrating metabolomics and transcriptomics, we herein show that oncogenic RTK activation causes distinct metabolic preference. Specifically, EGFR activation branches glycolysis to the serine synthesis for nucleotide biosynthesis and redox homeostasis, whereas FGFR activation recycles lactate to fuel oxidative phosphorylation for energy generation. Genetic alterations of EGFR and FGFR stratify the responsive tumors to pharmacological inhibitors that target serine synthesis and lactate fluxes, respectively. Together, this study provides the molecular link between cancer genotypes and metabolic dependency, providing basis for patient stratification in metabolism-targeted therapies.
Metastasis accounts for 90% of cancer-related deaths and, currently, there are no effective clinical therapies to block the metastatic cascade. A need to develop novel therapies specifically ...targeting fundamental metastasis processes remains urgent. Here, we demonstrate that Salmonella YB1, an engineered oxygen-sensitive strain, potently inhibits metastasis of a broad range of cancers. This process requires both IFN-γ and NK cells, as the absence of IFN-γ greatly reduces, whilst depletion of NK cells in vivo completely abolishes, the anti-metastatic ability of Salmonella. Mechanistically, we find that IFN-γ is mainly produced by NK cells during early Salmonella infection, and in turn, IFN-γ promotes the accumulation, activation, and cytotoxicity of NK cells, which kill the metastatic cancer cells thus achieving an anti-metastatic effect. Our findings highlight the significance of a self-regulatory feedback loop of NK cells in inhibiting metastasis, pointing a possible approach to develop anti-metastatic therapies by harnessing the power of NK cells.
Cancer cells experience an increase in oxidative stress. The pentose phosphate pathway (PPP) is a major biochemical pathway that generates antioxidant NADPH. Here, we show that transketolase (TKT), ...an enzyme in the PPP, is required for cancer growth because of its ability to affect the production of NAPDH to counteract oxidative stress. We show that TKT expression is tightly regulated by the Nuclear Factor, Erythroid 2-Like 2 (NRF2)/Kelch-Like ECH-Associated Protein 1 (KEAP1)/BTB and CNC Homolog 1 (BACH1) oxidative stress sensor pathway in cancers. Disturbing the redox homeostasis of cancer cells by genetic knockdown or pharmacologic inhibition of TKT sensitizes cancer cells to existing targeted therapy (Sorafenib). Our study strengthens the notion that antioxidants are beneficial to cancer growth and highlights the therapeutic benefits of targeting pathways that generate antioxidants.
Besides the conventional carbon sources, acetyl-CoA has recently been shown to be generated from acetate in various types of cancers, where it promotes lipid synthesis and tumour growth. The ...underlying mechanism, however, remains largely unknown. We find that acetate induces a hyperacetylated state of histone H3 in hypoxic cells. Acetate predominately activates lipogenic genes ACACA and FASN expression by increasing H3K9, H3K27 and H3K56 acetylation levels at their promoter regions, thus enhancing de novo lipid synthesis, which combines with its function as the metabolic precursor for fatty acid synthesis. Acetyl-CoA synthetases (ACSS1, ACSS2) are involved in this acetate-mediated epigenetic regulation. More importantly, human hepatocellular carcinoma with high ACSS1/2 expression exhibit increased histone H3 acetylation and FASN expression. Taken together, this study demonstrates that acetate, in addition to its ability to induce fatty acid synthesis as an immediate metabolic precursor, also functions as an epigenetic metabolite to promote cancer cell survival under hypoxic stress.
Aim
To identify the potential metabolite markers in diabetic retinopathy (DR) by using gas chromatography coupled with time-of-flight mass spectrometry (GC-TOFMS).
Methods
GC-TOFMS spectra were ...acquired from vitreous and aqueous humor (AH) samples of patients with DR and non-diabetic participants. Comparative analysis was used to elucidate the distinct metabolites of DR. Metabolic pathway was employed to explicate the metabolic reprogramming pathways involved in DR. Logistic regression and receiver-operating characteristic analyses were carried out to select and validate the biomarker metabolites and establish a therapeutic model.
Results
Comparative analysis showed a clear separation between disease and control groups. Eight differentiating metabolites from AH and 15 differentiating metabolites from vitreous were highlighted. Out of these 23 metabolites, 11 novel metabolites have not been detected previously. Pathway analysis identified nine pathways (three in AH and six in vitreous) as the major disturbed pathways associated with DR. The abnormal of gluconeogenesis, ascorbate–aldarate metabolism, valine–leucine–isoleucine biosynthesis, and arginine–proline metabolism might weigh the most in the development of DR. The AUC of the logistic regression model established by
d
-2,3-Dihydroxypropanoic acid, isocitric acid, fructose 6-phosphate, and
l
-Lactic acid in AH was 0.965. The AUC established by pyroglutamic acid and pyruvic acid in vitreous was 0.951.
Conclusions
These findings have expanded our understanding of identified metabolites and revealed for the first time some novel metabolites in DR. These results may provide useful information to explore the mechanism and may eventually allow the development of metabolic biomarkers for prognosis and novel therapeutic strategies for the management of DR.
The risk of drug-induced liver injury (DILI) poses a major challenge for development of natural products derived from traditional Chinese medicines (NP-TCMs). It is urgent to find a new method for ...the safety assessment of the NP-TCMs. Recent study has reported an in vitro/in silico method to estimate the acceptable daily intake of hepatotoxic compounds using support vector machine (SVM) classifier and physiologically based pharmacokinetic (PBPK) modeling. However, this method is not suitable for estimating the dosing schedule of compounds which are administered in multiple daily doses. Thus, in this study, the method mentioned above was in particular optimized, and used to estimate the hepatotoxic plasma concentrations of 17 NP-TCMs. Additionally, the oral dosing schedules of the triptolide, emodin, matrine and oxymatrine were also predicted by the SVM classifier and PBPK modeling. The optimization included that: (1) in vitro cytotoxicity data of 28 training set compounds was optimized using benchmark concentrations (BMC) modeling; (2) AUC of the training set compound was used as the in vivo metric instead of
C
max
to better reflect the total daily exposure of compounds which are administered in multiple daily doses; (3) using the mean AUC in plasma as in vivo metric and BMC value as in vitro metric could achieve the better toxicity separation index (0.962 vs. 0.938); (4) The TSI for
C
max
and BMC values was 0.985 calculated in this study, and the results indicated that BMC modeling improved the separation performance. This optimized in vitro–in vivo extrapolation (IVIVE) workflow could extrapolate in vitro BMC to blood concentrations and the oral dosing schedule which are corresponding to certain risk of hepatotoxicity. The estimated safe dosing schedule of oxymatrine by this optimized method was close to the clinical recommended dosing regimen. The results indicate that the optimized method could be used to predict the dosing schedule of compounds administered in multiple daily doses, and our optimized workflow could be helpful for the safety assessment as well as the research and development on NP-TCMs.
Scope
To evaluate the health‐promoting potentials of piceatannol (PIC), a dietary resveratrol derivative, its biotransformation is examined.
Methods and results
The biotransformation is tested in ...human/rat hepatic microsomes and cytosols; its pharmacokinetic profiles are assessed in rats. Although limited phase I metabolism exists in microsomes, PIC is rapidly converted to two pharmacologically active metabolites, namely rhapontigenin (RHA) and isorhapontigenin (ISO) in cytosols. Such biotransformation is completely blocked by entacapone, a well‐known catechol‐O‐methyltransferase (COMT) inhibitor, demonstrating that the O‐methylation is mediated by COMT. Moreover, PIC is identified as a substrate inhibitor of COMT, suggesting its potential benefits in Alzheimer's disease. Due to extensive phase II metabolism including glucuronidation, sulfation, and O‐methylation, PIC displays rapid clearance and at least 4.02% ± 0.61% and 17.70% ± 0.91% of PIC is converted to RHA and ISO, respectively, in rats after intravenous administration. Similarly, PIC serves as an effective precursor of ISO upon oral administration.
Conclusion
Since PIC and its metabolites possess pleiotropic health‐promoting activities, it has emerged as a promising nutraceutical candidate for further development. This study also reinforces the importance of in vivo testing in nutritional researches as the active metabolite(s) may be absent from the in vitro system.
Piceatannol is substantially O‐methylated to rhapontigenin and isorhapontigenin by catechol‐O‐methyltransferase (COMT). As a COMT substrate inhibitor, piceatannol displays health potential for Alzheimer's disease. Piceatannol, rhapontigenin, and isorhapontigenin are extensively metabolized by glucuronosyltransferase (UGT) and/or sulfotransferase (SULT), which can be reversed by glucuronidase (GLU) and sulfatase (STS). Clearly, active metabolites and reversed metabolism contribute to the health‐promoting effects of piceatannol.
Artemether, an artemisinin derivative, is used in the management of life-threatening severe malaria. This study aimed to develop an intravenous dosage form of artemether using nanotechnology. ...Artemether-loaded zein nanoparticles were prepared by modified antisolvent precipitation using sodium caseinate as a stabilizer. Subsequently, the physicochemical properties of the nanoparticles were characterized; the in vitro hemolytic property was examined with red blood cells, while the pharmacokinetic profile was evaluated in Sprague-Dawley rats after intravenous administration. The artemether-loaded zein nanoparticles were found to display good encapsulation efficiency, excellent physical stability and offer an in vitro extended-release property. Interestingly, encapsulation of artemether into zein nanoparticles substantially suppressed hemolysis, a common clinical phenomenon occurring after artemisinin-based antimalarial therapy. Upon intravenous administration, artemether-loaded zein nanoparticles extended the mean residence time of artemether by ~80% in comparison to the free artemether formulation (82.9 ± 15.2 versus 45.6 ± 16.4 min,
< 0.01), suggesting that the nanoparticles may prolong the therapeutic duration and reduce the dosing frequency in a clinical setting. In conclusion, intravenous delivery of artemether by artemether-loaded zein nanoparticles appears to be a promising therapeutic option for severe malaria.
Cancer cells need to generate large amounts of glutathione (GSH) to buffer oxidative stress during tumor development. A rate-limiting step for GSH biosynthesis is cystine uptake via a ...cystine/glutamate antiporter Xc
. Xc
is a sodium-independent antiporter passively driven by concentration gradients from extracellular cystine and intracellular glutamate across the cell membrane. Increased uptake of cystine via Xc
in cancer cells increases the level of extracellular glutamate, which would subsequently restrain cystine uptake via Xc
. Cancer cells must therefore evolve a mechanism to overcome this negative feedback regulation. In this study, we report that glutamate transporters, in particular SLC1A1, are tightly intertwined with cystine uptake and GSH biosynthesis in lung cancer cells. Dysregulated SLC1A1, a sodium-dependent glutamate carrier, actively recycled extracellular glutamate into cells, which enhanced the efficiency of cystine uptake via Xc
and GSH biosynthesis as measured by stable isotope-assisted metabolomics. Conversely, depletion of glutamate transporter SLC1A1 increased extracellular glutamate, which inhibited cystine uptake, blocked GSH synthesis, and induced oxidative stress-mediated cell death or growth inhibition. Moreover, glutamate transporters were frequently upregulated in tissue samples of patients with non-small cell lung cancer. Taken together, active uptake of glutamate via SLC1A1 propels cystine uptake via Xc
for GSH biosynthesis in lung tumorigenesis. SIGNIFICANCE: Cellular GSH in cancer cells is not only determined by upregulated Xc
but also by dysregulated glutamate transporters, which provide additional targets for therapeutic intervention.
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