The regulatory roles and clinical significance of glycolysis in tumor

Metabolic reprogramming has been demonstrated to have a significant impact on the biological behaviors of tumor cells, among which glycolysis is an important form. Recent research has revealed that the heightened glycolysis levels, the abnormal expression of glycolytic enzymes, and the accumulation of glycolytic products could regulate the growth, proliferation, invasion, and metastasis of tumor cells and provide a favorable microenvironment for tumor development and progression. Based on the distinctive glycolytic characteristics of tumor cells, novel imaging tests have been developed to evaluate tumor proliferation and metastasis. In addition, glycolytic enzymes have been found to serve as promising biomarkers in tumor, which could provide assistance in the early diagnosis and prognostic assessment of tumor patients. Numerous glycolytic enzymes have been identified as potential therapeutic targets for tumor treatment, and various small molecule inhibitors targeting glycolytic enzymes have been developed to inhibit tumor development and some of them are already applied in the clinic. In this review, we systematically summarized recent advances of the regulatory roles of glycolysis in tumor progression and highlighted the potential clinical significance of glycolytic enzymes and products as novel biomarkers and therapeutic targets in tumor treatment.

The interaction between apigenin and PKM2 restrains progression of colorectal cancer

Apigenin, a flavonoid that widely existed in vegetables and fruits, possesses anticarcinogenic, low toxicity, and no mutagenic properties, suggesting that apigenin is a potential therapeutic agent for tumors. However, the underlying anti-cancer molecular target of apigenin is still unclear. Therefore, to reveal the direct target and amino acid site of apigenin against colorectal cancer is the focus of this study. In the present study, the results proved that the anti-CRC activity of apigenin was positively correlated with pyruvate kinase M2 (PKM2) expression, characterized by the inhibition of cell proliferation and increase of apoptotic effects induced by apigenin in LS-174T cells of knock down PKM2. Next, pull-down and MALDI-TOF/TOF analysis determined that apigenin might interact directly with PKM2 in HCT-8 cells. Further, the study confirmed that lysine residue 433 (K433) was a key amino acid site for PKM2 binding to apigenin. Apigenin restricted the glycolysis of LS-174T and HCT-8 cells by targeting the K433 site of PKM2, thereby playing an anti-CRC role in vivo and in vitro. Meanwhile, apigenin markedly attenuated tumor growth without any adverse effects. Taken together, these findings reveal that apigenin is worthy of consideration as a promising PKM2 inhibitor for the prevention of CRC.

Hydrolysable tannins as a potential therapeutic drug for the human fibrosis-associated disease

Fibrosis is a pathological change with abnormal tissue regeneration due to a response to persistent injury, which is extensively related to organ damage and failure, leading to high morbidity and mortality worldwide. Although the pathogenesis of fibrosis has been comprehensively elucidated, there are few effective therapies for treating fibrotic diseases. Natural products are increasingly regarded as an effective strategy for fibrosis with numerous favorable functions. Hydrolysable tannins (HT) are a type of natural products that have the potential to treat the fibrotic disease. In this review, we describe some biological activities and the therapeutic prospects of HT in organ fibrosis. Furthermore, the underlying mechanisms of inhibition of HT on fibrotic organs in relation to inflammation, oxidative stress, epithelial-mesenchymal transition, fibroblast activation and proliferation, and extracellular matrix accumulation are discussed. Understanding the mechanism of HT against fibrotic diseases will provide a new strategy for the prevention and attenuation of fibrosis progression.

Tannins in cancer prevention and therapy

Tannins are a heterogenous class of polyphenolic natural products with promising cancer chemopreventive and therapeutic potential. Studies undertaken over the last 30 years have demonstrated their capacity to target many cellular pathways and molecules important in the development of cancer. Recently, new mechanisms that might be important in anti-carcinogenic activity, such as inhibition of epithelial-to-mesenchymal transition, reduction of cancer stem cell creation, and modulation of cancer cells metabolism have been described. Along with the mechanisms underlying the anti-cancer activity of tannins, this review focuses on their possible application as chemosensitizers in adjuvant therapy and countering multidrug resistance. Furthermore, characteristic physicochemical properties of some tannins, particularly tannic acid, are useful in the formation of nanovehicles for anticancer drugs or the isolation of circulating cancer cells. These new potential applications of tannins deserve further studies. Well-designed clinical trials, which are scarce, are needed to assess the therapeutic effects of tannins themselves or as adjuvants in cancer treatment.

Modulation of Acid-Sensing Ion Channels by Tannic Acid and Green Tea via a Membrane-Mediated Mechanism

Acid-sensing ion channels (ASICs) are proton-gated ion channels that contribute to pain perception and neurotransmission. Being involved in sensing inflammation and ischemia, ASIC1a and ASIC3 are promising drug targets. Polyphenol tannic acid (TA) as well as green tea can interact with a variety of ion channels, but their effect on ASICs remains unknown. In addition, it is unknown whether they interact with ion channels via a common mechanism. Here, we show that TA is a potent modulator of ASICs. TA inhibited the transient current of rat ASIC3 expressed in HEK cells with an apparent IC₅₀ of 2.2 ± 0.6 μM; it potentiated the sustained current and induced a slowly declining decay current. In addition, it produced an acidic shift of the pH-dependent activation of ASIC3 and inhibited the window current at pH 7.0. Moreover, TA inhibited the transient current of ASIC1a, ASIC1b, and ASIC2a. Pentagalloylglucose that is chemically identical to the central part of TA and a green tea extract both had effects on ASIC3 comparable to TA. TA and green tea inhibited inward currents generated by gramicidin channels, indicating interaction with the membrane. These results show that TA, pentagalloylglucose, and green tea modulate ASICs and identify alteration of the membrane as the potential common mechanism of this modulation. These properties will limit clinical application of these molecules.

Ellagic Acid and Its Metabolites as Potent and Selective Allosteric Inhibitors of Liver Pyruvate Kinase

Liver pyruvate kinase (PKL) has recently emerged as a new target for non-alcoholic fatty liver disease (NAFLD), and inhibitors of this enzyme could represent a new therapeutic option. However, this breakthrough is complicated by selectivity issues since pyruvate kinase exists in four different isoforms. In this work, we report that ellagic acid (EA) and its derivatives, present in numerous fruits and vegetables, can inhibit PKL potently and selectively. Several polyphenolic analogues of EA were synthesized and tested to identify the chemical features responsible for the desired activity. Molecular modelling studies suggested that this inhibition is related to the stabilization of the PKL inactive state. This unique inhibition mechanism could potentially herald the development of new therapeutics for NAFLD.

Natural products targeting glycolysis in cancer

Many energy metabolism pathways exist in cancer, including glycolysis, amino acid metabolism, fatty acid oxidation, and mitochondrial respiration. Tumor cells mainly generate energy through glycolysis to maintain growth and biosynthesis of tumor cells under aerobic conditions. Natural products regulate many steps in glycolysis and targeting glycolysis using natural products is a promising approach to cancer treatment. In this review, we exemplify the relationship between glycolysis and tumors, demonstrate the natural products that have been discovered to target glycolysis for cancer treatment and clarify the mechanisms involved in their actions. Natural products, such as resveratrol mostly found in red grape skin, licochalcone A derived from root of Glycyrrhiza inflate, and brusatol found in Brucea javanica and Brucea mollis, largely derived from plant or animal material, can affect glycolysis pathways in cancer by targeting glycolytic enzymes and related proteins, oncogenes, and numerous glycolytic signal proteins. Knowledge of how natural products regulate aerobic glycolysis will help illuminate the mechanisms by which these products can be used as therapeutics to inhibit cancer cell growth and regulate cellular metabolism. Systematic Review Registration: https://pubmed.ncbi.nlm.nih.gov/, https://clinicaltrials.gov/, http://lib.zzu.edu.cn/.

Characterization of a novel pyruvate kinase from Trichinella spiralis and its participation in sugar metabolism, larval molting and development

Background

Pyruvate kinase widely exists in many parasites and plays an important role in the energy production for the parasites. Pyruvate kinase might be a potential drug target for killing the parasites. The aim of the present study was to evaluate the biological characteristics and roles of T. spiralis pyruvate kinase M (TsPKM) in sugar metabolism, larval molting and development of T. spiralis.

Methodology/Principal findings

TsPKM has two functional domains of pyruvate kinase and the tertiary structure of TsPKM is tetramer which has the enzyme active site constituted by 8 amino-acid residues (Arg71, Asn73, Asp110, Phe241, Lys267, Glu269, Asp293 and Thr325). Recombinant TsPKM (rTsPKM) was expressed and purified. The rTsPKM had good immunogenicity. RT-PCR and Western blot showed that TsPKM was transcribed and expressed at various developmental stages in T. spiralis lifecycle. Immunofluorescence test showed that TsPKM was principally located in the cuticle, muscle, stichosome, intestine and the intrauterine embryos of female adults. rTsPKM catalyzed the reaction of phosphoenolpyruvate (PEP) and adenosine diphosphate (ADP) to produce pyruvic acid and adenosine triphosphate (ATP). TsPKM played an important role in the metabolism and energy production of T. spiralis. After silencing of TsPKM gene by specific dsRNA-TsPKM2, protein expression and enzyme activity of TsPKM decreased by 50.91 and 26.06%, respectively. After treatment with RNAi, natural TsPKM enzyme activity, larval molting, sugar metabolism, growth and development of T. spiralis were significantly reduced.

Conclusions

TsPKM participates in the larval molting, sugar metabolism, growth and development of T. spiralis and it might be a candidate target of therapeutic drug of trichinellosis.

Pyruvate kinases belong to transferases and can transfer the high-energy phosphate bond of phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP) to produce pyruvic acid and adenosine triphosphate (ATP). Pyruvate kinases play a significant biological role in the parasite survival in hosts. Our results revealed that TsPKM was expressed at various T. spiralis developmental stages, and principally located in the cuticle, stichosome, intestine and the intrauterine embryos of female adults. rTsPKM catalyzed the reaction of phosphoenolpyruvate (PEP) and adenosine diphosphate (ADP) to produce pyruvic acid and adenosine triphosphate (ATP). TsPKM played an important role in the metabolism and energy production of T. spiralis. Protein expression and enzyme activity of TsPKM were decreased by 50.91 and 26.06% respectively through silencing of TsPKM gene using specific dsRNA-TsPKM2. After treatment with RNAi and inhibitor tannin, natural TsPKM activity, larval molting, sugar metabolism, growth and development of T. spiralis were obviously inhibited. Our results showed that TsPKM participates in T. spiralis molting, sugar metabolism and development, and it might be a candidate target for anti-Trichinella drugs.

Natural products targeting glycolytic signaling pathways-an updated review on anti-cancer therapy

Glycolysis is a complex metabolic process that occurs to convert glucose into pyruvate to produce energy for living cells. Normal cells oxidized pyruvate into adenosine triphosphate and carbon dioxide in the presence of oxygen in mitochondria while cancer cells preferentially metabolize pyruvate to lactate even in the presence of oxygen in order to maintain a slightly acidic micro-environment of PH 6.5 and 6.9, which is beneficial for cancer cell growth and metastasis. Therefore targeting glycolytic signaling pathways provided new strategy for anti-cancer therapy. Natural products are important sources for the treatment of diseases with a variety of pharmacologic activities. Accumulated studies suggested that natural products exhibited remarkable anti-cancer properties both in vitro and in vivo. Plenty of studies suggested natural products like flavonoids, terpenoids and quinones played anti-cancer properties via inhibiting glucose metabolism targets in glycolytic pathways. This study provided an updated overview of natural products controlling glycolytic pathways, which also provide insight into druggable mediators discovery targeting cancer glucose metabolism.

Pharmacological effects and mechanisms of tannic acid

In recent years, increasing attention has been paid to the pharmacological efficacy of tannins. Tannic acid (TA), the simplest hydrolysable tannin that has been approved by the FDA as a safe food additive, is one of the most important components of these traditional medicines. Studies have shown that TA displays a wide range of pharmacological activities, such as anti-inflammatory, neuroprotective, antitumor, cardioprotective, and anti-pathogenic effects. Here, we summarize the known pharmacological effects and associated mechanisms of TA. We focus on the effect and mechanism of TA in various animal models of inflammatory disease and organ, brain, and cardiovascular injury. Moreover, we discuss the possible molecular targets and signaling pathways of TA, in addition to the pharmacological effects of TA-based nanoparticles and TA in combination with chemotherapeutic drugs.

Tannic Acid Exhibits Antiangiogenesis Activity in Nonsmall-Cell Lung Cancer Cells

Nonsmall-cell lung cancer (NSCLC) is the most common type of lung cancer, with a dismal prognosis. NSCLC is a highly vascularized tumor, and chemotherapy is often hampered by the development of angiogenesis. Therefore, suppression of angiogenesis is considered a potential treatment approach. Tannic acid (TA), a natural polyphenol, has been demonstrated to have anticancer properties in a variety of cancers; however, its angiogenic properties have yet to be studied. Hence, in the current study, we investigated the antiproliferative and antiangiogenic effects of TA on NSCLC cells. The (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assay revealed that TA induced a dose- and time-dependent decrease in the proliferation of A549 and H1299 cells. However, TA had no significant toxicity effects on human bronchial epithelial cells. Clonogenicity assay revealed that TA suppressed colony formation ability in NSCLC cells in a dose-dependent manner. The anti-invasiveness and antimigratory potential of TA were confirmed by Matrigel and Boyden chamber studies, respectively. Importantly, TA also decreased the ability of human umbilical vein endothelial cells (HUVEC) to form tube-like networks, demonstrating its antiangiogenic properties. Extracellular vascular endothelial growth factor (VEGF) release was reduced in TA-treated cells compared to that in control cells, as measured by the enzyme-linked immunosorbent assay (ELISA). Overall, these results demonstrate that TA can induce antiproliferative and antiangiogenic effects against NSCLC.

Cancer metabolism control by natural products: Pyruvate kinase M2 targeting therapeutics

Glycolysis is the primary source of energy for cancer growth and metastasis. The shift in metabolism from mitochondrial oxidative phosphorylation to aerobic glycolysis is called the Warburg effect. Cancer progression due to aerobic glycolysis is often associated with the activation of oncogenes or the loss of tumor suppressors. Therefore, inhibition of glycolysis is one of the effective strategies in cancer control. Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme overexpressed in breast, prostate, lung, colorectal, and liver cancers. Here, we discuss published studies regarding PKM2 inhibitors from natural products that are promising drug candidates for cancer therapy. We have highlighted the potential of natural PKM2 inhibitors for various cancer types. Moreover, we encourage researchers to evaluate the combinational effects between natural and synthetic PKM2 inhibitors. Also, further high-quality studies are needed to firmly establish the clinical efficacy of natural products.

Predicting the Activities of Drug Excipients on Biological Targets using One-Shot Learning

Excipients are major components of drugs and are used to improve drug attributes such as stability and appearance. Excipients approved by the U.S. Food and Drug Administration (FDA) are regarded as safe for humans in allowed concentrations, but their potential interactions with drug targets have not been investigated systematically, which might influence a drug's efficacy. Deep learning models have been used for the identification of ligands that could bind to the drug targets. However, due to the limited available data, it is challenging to reliably estimate the likelihood of a ligand-protein interaction. One-shot learning techniques provide a potential approach to address this low data problem as these techniques require only one or a few examples to classify the new data. In this study, we apply one-shot learning models to data sets that include ligands binding to G-protein-coupled receptors (GPCRs) and kinases. The predicted results suggest that one-shot learning could be used for predicting ligand-protein interactions, and the models attain better performance when protein targets contain conserved binding pockets. The trained models are also used to predict interactions between excipients and drug targets, which provides a potential efficient strategy to explore the activities of drug excipients. We find that a large number of drug excipients could interact with biological targets and influence their function. The results demonstrate how one-shot learning can be used to make accurate predictions for excipient-protein interactions, and these methods could be used for selecting excipients with limited drug-protein interactions.

A Perspective on Medicinal Chemistry Approaches for Targeting Pyruvate Kinase M2

The allosteric regulation of pyruvate kinase M2 (PKM2) affects the switching of the PKM2 protein between the high-activity and low-activity states that allow ATP and lactate production, respectively. PKM2, in its low catalytic state (dimeric form), is chiefly active in metabolically energetic cells, including cancer cells. More recently, PKM2 has emerged as an attractive target due to its role in metabolic dysfunction and other interrelated conditions. PKM2 (dimer) activity can be inhibited by modulating PKM2 dimer-tetramer dynamics using either PKM2 inhibitors that bind at the ATP binding active site of PKM2 (dimer) or PKM2 activators that bind at the allosteric site of PKM2, thus activating PKM2 from the dimer formation to the tetrameric formation. The present perspective focuses on medicinal chemistry approaches to design and discover PKM2 inhibitors and activators and further provides a scope for the future design of compounds targeting PKM2 with better efficacy and selectivity.

Polyphenol-Modified Nanovesicles for Synergistically Enhanced in vitro Tumor Cell Targeting and Apoptosis

Tannic acid (TA) not only prevents drug carriers from sticking to the glycocalyx layer of vascular endothelial cells but also has anti-cancer attributes, thereby improving drug delivery efficiency in cancer...

New Properties and Mitochondrial Targets of Polyphenol Agrimoniin as a Natural Anticancer and Preventive Agent

Agrimoniin is a polyphenol from the group of tannins with antioxidant and anticancer activities. It is assumed that the anticancer action of agrimoniin is associated with the activation of mitochondria-dependent apoptosis, but its mitochondrial targets have not been estimated. We examined the direct influence of agrimoniin on different mitochondrial functions, including the induction of the mitochondrial permeability transition pore (MPTP) as the primary mechanism of mitochondria-dependent apoptosis. Agrimoniin was isolated from Agrimonia pilosa Ledeb by multistep purification. The content of agrimoniin in the resulting substance reached 80%, as determined by NMR spectroscopy. The cytotoxic effect of purified agrimoniin was confirmed on the cultures of K562 and HeLa cancer cells by the MTT assay. When tested on isolated rat liver mitochondria, agrimoniin at a low concentration (10 µM) induced the low-amplitude swelling, which was inhibited by the MPTP inhibitors ADP and cyclosporine A, activated the opening of MPTP by calcium ions and stimulated the respiration supported by succinate oxidation. Also, agrimoniin reduced the electron acceptor DCPIP in a concentration-dependent manner and chelated iron ions. Owing to all these properties, agrimoniin can stimulate apoptosis or activate mitochondrial functions, which can be helpful in the prevention and elimination of stagnant pathological states.

Chitosan-Decorated PLGA-NPs Loaded with Tannic Acid/Vitamin E Mitigate Colon Cancer via the NF-κB/β-Cat/EMT Pathway

Colon cancer is the second highest contributor of cancer-related deaths throughout the world. Treatment strategies with tannic acid and vitamin E are envisaged as desirable and safe owing to their robust antioxidative and anti-inflammatory potential. In the present report, these bioactives have been nanoencapsulated in poly(d,l-lactide-co-glycolic acid) (PLGA) formulations for maintaining sustained release and ensuring enhanced bioavailability. Capping of nanoparticles (NPs) with chitosan was done for enhanced anticancer efficacy and tumor targeting. CS-PLGA-TA-E, administered intraperitoneally, significantly inhibited tumor number and tumor volume and normalized colon histology in the colon cancer. Tissue distribution studies showed that TA/E content from CS-PLGA-TA-E was present in a higher concentration in the tumor tissue than the concentration of TA/E content from PLGA-TA-E or free TA or free E. Also, the TA/E content from all of the treatment groups showed its highest concentration in the tumor compared to other organs. Antioxidant enzymes and proinflammatory cytokines (TNF-α, IL-1β, IL-6) were inhibited by CS-PLGA-TA-E. CS-PLGA-TA-E inhibited markers for tumor growth (EGFR-PI3K-AKT), inflammation (NF-κB/Stat3), β-catenin signaling (β-catenin, c-myc, cyclin D1), EMT (E-cadherin, N-cadherin, vimentin), and apoptosis (Bcl-2) in a significantly greater way as compared with PLGA-TA-E, TA, or E. CS-PLGA-TA-E NPs can be considered promising anticancer drugs for colon cancer.

Potential role of tea extract in oocyte development

Tea is the second most popular beverage in the world and beneficial to health. It has been demonstrated that tea polyphenols can reduce the risk of diseases, such as cancers, diabetes, obesity, Alzheimer's disease, etc. But the knowledge of tea extract on the female germline is limited. Folliculogenesis is a complicated process and prone to be affected by ROS. Tea polyphenols can reduce the accumulation of ROS in folliculogenesis and affect oocyte maturation. Tea extract also influences granulosa cell proliferation and expansion during oocyte growth and maturation. However, the studies about the benefits of tea extract on female germline are few, and the underlying mechanisms are obscure. In the present study, we will mainly discuss the effects of tea extract on ovarian function, oocyte maturation, and the underlying possible mechanisms, and according to the discussion, we suggest that tea extract may have benefits for oocytes at an appropriate dose.

Kinetic Characterization and Inhibitor Screening of Pyruvate Kinase I From Babesia microti

The apicomplexan Babesia microti is a main pathogenic parasite causing human babesiosis, which is one of the most widely distributed tick-borne diseases in humans. Pyruvate kinase (PYK) plays a central metabolic regulatory role in most living organisms and catalyzes the essentially irreversible step in glycolysis that converts phosphoenolpyruvate (PEP) to pyruvate. Hence, PYK is recognized as an attractive therapeutic target in cancer and human pathogens such as apicomplexans. In this study, we cloned, expressed, and purified B. microti PYK I (BmPYKI). Western blotting illustrated that anti-rBmPYKI antibody could specifically recognize the native BmPYKI protein in the lysate of B. microti with a 54-kDa band, which is consistent with the predicted size. In addition, the enzymatic activity of the purified recombinant PYKI (rPYKI) was tested under a range of pH values. The results showed that the maximum catalytic activity could be achieved at pH 7.0. The saturation curves for substrates demonstrated that the K_m value for PEP was 0.655 ± 0.117 mM and that for ADP was 0.388 ± 0.087 mM. We further investigated the effect of 13 compounds on rBmPYKI. Kinetic analysis indicated that six inhibitors (tannic acid, shikonin, apigenin, PKM2 inhibitor, rosiglitazone, and pioglitazone) could significantly inhibit the catalytic activity of PYKI, among which tannic acid is the most efficient inhibitor with an IC₅₀ value 0.49 μM. Besides, four inhibitors (tannic acid, apigenin, shikonin, and PKM2 inhibitor) could significantly decrease the growth of in vitro-cultured B. microti with IC₅₀ values of 0.77, 2.10, 1.73, and 1.15 μM. Overall, the present study provides a theoretical basis for the design and development of new anti-Babesia drugs.

Discovery and development of tumor glycolysis rate-limiting enzyme inhibitors

Tumor cells mainly provide necessary energy and substances for rapid cell growth through aerobic perglycolysis rather than oxidative phosphorylation. This phenomenon is called the "Warburg effect". The mechanism of glycolysis in tumor cells is more complicated, which is caused by the comprehensive regulation of multiple factors. Abnormal enzyme metabolism is one of the main influencing factors and inhibiting the three main rate-limiting enzymes in glycolysis is thought to be important strategy for cancer treatment. Therefore, numerous inhibitors of glycolysis rate-limiting enzyme have been developed in recent years, such as the latest HKII inhibitor and PKM2 inhibitor Pachymic acid (PA) and N-(4-(3-(3-(methylamino)-3-oxopropyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-1-yl)phenyl)propiolamide. The review focuses on source, structure-activity relationship, bioecological activity and mechanism of the three main rate-limiting enzymes inhibitors, and hopes to guide the future research on the design and synthesis of rate-limiting enzyme inhibitors.

WDR45 Mutation Impairs the Autophagic Degradation of Transferrin Receptor and Promotes Ferroptosis

WDR45 is an autophagy-related protein that involves in the formation of autophagosome. Mutations in WDR45 lead to the impairment of autophagy which is associated with the human β-propeller protein-associated neurodegeneration (BPAN). However, the relationship between autophagy and brain iron accumulation in patients with BPAN remains unclear. Here, we demonstrated that transferrin receptor (TfRC) which is critical for the iron import of cells was degraded via autophagy. TfRC was accumulated after the inhibition of autophagy by treatment with autophagic inhibitor chloroquine or knockdown of ATG2A. The intracellular iron content was increased in cells overexpressing TfRC or mutant WDR45, however, ferritin H (FTH) chain was decreased. Increased TfRC and simultaneously decreased FTH consequently resulted in an elevated level of ferrous iron (Fe²⁺) which further promoted cell ferroptosis, demonstrated by the increased lipid peroxidation and reactive oxygen species (ROS) and the decreased glutathione peroxidase 4 (GPX4) and cell viability. Taken together, these findings provide a piece of important evidence that WDR45 deficiency impairs autophagic degradation of TfRC, therefore leading to iron accumulation, and the elevated iron promotes ferroptosis which may contribute to the progression of BPAN.

Elkasabgy N, Shao P, A. Farag M. Recent Advances in Tannic Acid (Gallotannin) Anticancer Activities and Drug Delivery Systems for Efficacy Improvement; A Comprehensive Review

Tannic acid is a chief gallo-tannin belonging to the hydrolysable tannins extracted from gall nuts and other plant sources. A myriad of pharmaceutical and biological applications in the medical field has been well recognized to tannic acid. Among these effects, potential anticancer activities against several solid malignancies such as liver, breast, lung, pancreatic, colorectal and ovarian cancers have been reported. Tannic acid was found to play a maestro-role in tuning several oncological signaling pathways including JAK/STAT, RAS/RAF/mTOR, TGF-β1/TGF-β1R axis, VEGF/VEGFR and CXCL12/CXCR4 axes. The combinational beneficial effects of tannic acid with other conventional chemotherapeutic drugs have been clearly demonstrated in literature such as a synergistic anticancer effect and enhancement of the chemo-sensitivity in several resistant cases. Yet, clinical applications of tannic acid have been limited owing to its poor lipid solubility, low bioavailability, off-taste, and short half-life. To overcome such obstacles, novel drug delivery systems have been employed to deliver tannic acid with the aim of improving its applications and/or efficacy against cancer cells. Among these drug delivery systems are several types of organic and metallic nanoparticles. In this review, the authors focus on the molecular mechanisms of tannic acid in tuning several neoplastic diseases as well as novel drug delivery systems that can be used for its clinical applications with an attempt to provide a systemic reference to promote the development of tannic acid as a cheap drug and/or drug delivery system in cancer management.

Natural Polyphenols as Targeted Modulators in Colon Cancer: Molecular Mechanisms and Applications

Colon cancer commonly develops from long-term chronic inflammation in the intestine and seriously threatens human health. Natural polyphenols have been valued as a crucial regulator of nutrient metabolism and metabolic diseases, owing to their anti-inflammatory and antioxidant functions and the ability to maintain a balance between gut microbes and their hosts. Notably, experimental and clinical evidence has shown that natural polyphenols could act as a targeted modulator to play a key role in the prevention or treatment of colon cancer. Thus, in this review, we summarized recent advances in the possible regulatory mechanism and the potential application of natural polyphenols in colon cancer, which might be regarded as a novel platform for the colon cancer management.

Tannic Acid (TA)-Functionalized Magnetic Nanoparticles for EpCAM-Independent Circulating Tumor Cell (CTC) Isolation from Patients with Different Cancers

The majority of current methods of isolating circulating tumor cells (CTCs) rely on a biomarker. However, the isolation efficiency may be compromised due to the heterogeneity of CTCs. In this work, a simple and broad-spectrum method is established to efficiently isolate the heterogeneous CTCs from patient blood samples using tannic acid (TA)-functionalized magnetic nanoparticles (MNPs). The TA-functionalized MNPs (MNPs-TA) inhibit the nonspecific adhesion of peripheral blood mononuclear cell (PBMC) and enhance cancer cell capture, resulting from the unique interaction between TA and glycocalyx on cancer cells. The MNPs-TA was demonstrated to effectively capture seven kinds of cancer cells (HeLa, PC-3, T24, MAD-MB-231, MCF-7, HT1080, A549) from artificial samples (62.3-93.7%). Moreover, this epithelial cell adhesion molecule (EpCAM)-independent CTC isolation method was also tested using clinical blood samples from patients with different cancers (21 patients), which may provide a universal tool to detect CTCs in the clinic.

Cucurbitacin E Chemosensitizes Colorectal Cancer Cells via Mitigating TFAP4/Wnt/β-Catenin Signaling

Chemoresistance and toxicity are the main obstacles that limit the efficacy of 5-fluorouracil (5-FU) in colorectal cancer (CRC) therapy. Hence, it is urgent to identify new adjuvants that can sensitize CRC cells to conventional chemotherapeutic approaches. Cucurbitacin E (CE) is a natural triterpenoid, widely distributed in dietary plants, and shows antitumor effects. Here, we report that CE enhances the sensitivity of CRC cells to chemotherapy via attenuating the expression of adenosine 5'-triphosphate (ATP)-binding cassette transporters ABCC1 and MDR1. Combined with CE-functionalized magnetite nanoparticles and gene ontology analysis, we found that CE-binding proteins may involve Wnt/β-catenin signaling. To validate the findings, β-catenin was upregulated in drug-resistant cell lines, and the synergistic effects of CE and chemotherapeutics were accompanied by the downregulation of β-catenin. Moreover, TFAP4 was identified as an intracellular target of CE. Remarkably, the combination of CE and 5-FU treatment attenuated β-catenin, MDR1, and ABCC1 expressions, while TFAP4 overexpression reversed their expressions by 2.68 ± 0.46-, 0.72 ± 0.44-, and 0.93 ± 0.21-fold, respectively. Thus, our results indicate that CE sensitizes CRC cells to chemotherapy by decreasing the TFAP4/Wnt/β-catenin signaling, suggesting that the dietary compound CE can be used as a chemosensitizing adjuvant for CRC treatment.

A novel miR-206/hnRNPA1/PKM2 axis reshapes the Warburg effect to suppress colon cancer growth

Alternative splicing of pyruvate kinase gene (PKM) results in a higher PKM2/PKM1 ratio that contributes to the Warburg effect and reversing the Warburg effect has opened novel avenues for cancer treatment. miR-206 functions as a tumor suppressor in several types of cancer. However, the effect and underlying mechanisms of miR-206 on the Warburg effect are not yet elucidated. Here, we showed that miR-206 expression was obviously decreased in CRC tissues based on LinkedOmics. A significant decrease in miR-206 expression was negatively correlated with advanced tumor stage, while inversely correlated with overall survival in CRC patients. Ectopic overexpression of miR-206 has dramatically restricted the cell proliferation, glucose consumption and lactate production in CRC cells, whereas transfection of miR-206 inhibitor exhibited the opposite results. Furthermore, miR-206 overexpression induced switching from PKM2 to PKM1 via modulating alternative splicing of PKM gene. The alternative splicing factor hnRNPA1 is identified as the direct functional target of miR-206. Mechanistically, miR-206 overexpression directly targeted hnRNPA1 to suppress PKM2 expression to attenuate Warburg effect and cell proliferation of CRC. Importantly, the restoration of hnRNPA1 expression mostly abrogated the miR-206-meditated Warburg effect. Collectively, these results revealed that the novel miR-206/hnRNPA1/PKM2 axis plays a pivotal role in the Warburg effect to modulate CRC progression.

Aryl Hydrocarbon Receptor Role in Co-Ordinating SARS-CoV-2 Entry and Symptomatology: Linking Cytotoxicity Changes in COVID-19 and Cancers; Modulation by Racial Discrimination Stress

There is an under-recognized role of the aryl hydrocarbon receptor (AhR) in co-ordinating the entry and pathophysiology of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) that underpins the COVID-19 pandemic. The rise in pro-inflammatory cytokines during the 'cytokine storm' induce indoleamine 2,3-dioxygenase (IDO), leading to an increase in kynurenine that activates the AhR, thereby heightening the initial pro-inflammatory cytokine phase and suppressing the endogenous anti-viral response. Such AhR-driven changes underpin the heightened severity and fatality associated with pre-existent high-risk medical conditions, such as type II diabetes, as well as to how racial discrimination stress contributes to the raised severity/fatality in people from the Black Asian and Minority Ethnic (BAME) communities. The AhR is pivotal in modulating mitochondrial metabolism and co-ordinating specialized, pro-resolving mediators (SPMs), the melatonergic pathways, acetyl-coenzyme A, and the cyclooxygenase (COX) 2-prostaglandin (PG) E2 pathway that underpin 'exhaustion' in the endogenous anti-viral cells, paralleling similar metabolic suppression in cytolytic immune cells that is evident across all cancers. The pro-inflammatory cytokine induced gut permeability/dysbiosis and suppression of pineal melatonin are aspects of the wider pathophysiological underpinnings regulated by the AhR. This has a number of prophylactic and treatment implications for SARS-CoV-2 infection and cancers and future research directions that better investigate the biological underpinnings of social processes and how these may drive health disparities.

Tannic Acid: Specific Form of Tannins in Cancer Chemoprevention and Therapy-Old and New Applications

Purpose of Review

This short review is aimed at providing an updated and comprehensive report on tannic acid biological activities and molecular mechanisms of action most important for cancer prevention and adjuvant therapy.

Recent Findings

Tannic acid (TA), a mixture of digallic acid esters of glucose, is a common ingredient of many foods. The early studies of its anti-mutagenic and anti-tumorigenic activity were mostly demonstrated in the mouse skin model. This activity has been explained by its ability to inhibit carcinogens activation, as well as antioxidant and anti-inflammatory properties. Recently, the cell cycle arrest, apoptosis induction, reduced rate of proliferation, and cell migration and adhesion of several cancer cell lines as a result of TA treatment were described. The underlining mechanisms include modulation of signaling pathways such as EGFR/Jak2/STATs, or inhibition of PKM2 glycolytic enzyme. Moreover, epithelial-to-mesenchymal transition prevention and decrease of cancer stem cells formation by TA were also reported. Besides, TA was found to be potent chemosensitizer overcoming multidrug resistance. Eventually, its specific physicochemical features were found useful for generation of drug-loaded nanoparticles.

Summary

TA was shown to be a very versatile molecule with possible application not only in cancer prophylaxis, as was initially thought, but also in adjuvant cancer therapy. The latter may refer to chemosensitization and its application as a part of drug delivery systems. More studies are required to better explore this subject. In addition, the effect of TA on normal cells and its bioavailability have to better characterized.

Streptococcus gallolyticus abrogates anti-carcinogenic properties of tannic acid on low-passage colorectal carcinomas

The tannase-producing Gram-positive bacterial species Streptococcus gallolyticus subsp. gallolyticus (Sgg) is an opportunistic pathogen of the human gut and strongly associated with colorectal cancer (CRC). A unique feature of Sgg is its ability to degrade tannic acids (TA). TA constitute an important part of the human diet with known anti-tumorigenic properties. Here, we examined whether Sgg is able to protect tumor cells from the toxic effect of TA and thus drive tumorigenesis indirectly. Human CRC cell lines (n = 8) were treated with increasing concentrations of TA. We confirmed the cytotoxic activity of TA in a dose-dependent manner. In virtually all cell lines, viability decreased significantly (>60% inhibition). Moreover, pyrogallol, the degradation product of TA, had no effect on the tested cell lines. This suggests a specific effect of TA. Cytotoxicity was due to necrosis and induction of senescence in residual cells. Finally, when TA was degraded by Sgg, the cytotoxic effect could be abolished. Tumor cells even responded with boosted cell proliferation, highlighting the impact of Sgg on CRC progression. We here provide another piece of evidence for the active interplay between Sgg and cancer preventive components. These data will help to move forward in designing concepts for therapeutic and eventually also prophylactic approaches to combat gastrointestinal malignancies.

Tannic acid inhibits electrogenic Na+/HCO3- co-transporter activity in embryonic neural stem cell-derived radial glial-like cells

Self-renewing neural stem cells and progenitor cells are cell populations that generate radial glial cells and neurons through asymmetric division. Regulation of intracellular pH in stem cells with high metabolic activity is critical for both cell signaling and proliferation. We have recently found that a S0859-inhibitable electrogenic Na⁺/HCO₃⁻ co-transporter (NBCe1, Slc4a4), is the primary pH_i regulatory mechanism in stem cell-derived radial glial-like cells. Here we show, by using the voltage-sensitive fluorescent dye DiBAC₄(3) and BCECF, a pH-sensitive dye, that an antioxidant, tannic acid (100 µM), can inhibit potassium- and calcium-dependent rapid changes in membrane potential and NBCe1 mediated pH_i regulation in brain-derived glial-like cells in vitro. Furthermore, neural stem cell differentiation and neurosphere formation (proliferation) were completely inhibited by tannic acid. The present study provides evidence that tannic acid is a natural inhibitor of NBCe1. It is tempting to speculate that tannic acid or related compounds that inhibits NBCe1-mediated pHi regulation in glial-like cells may also have bearing on the treatment of glial neoplasms.

Mechanism of a Novel Camptothecin-Deoxycholic Acid Derivate Induced Apoptosis against Human Liver Cancer HepG2 Cells and Human Colon Cancer HCT116 Cells

BACKGROUND

Camptothecin (CPT) is known as an anticancer drug in traditional Chinese medicine. However, due to the lack of targeting, low solubility, and instability of CPT, its therapeutic applications are hampered. Therefore, we synthesized a series of CPT-bile acid analogues that obtained a national patent to improve their tumour-targeting chemotherapeutic effects on liver or colon cancers. Among these analogues, the compound G2 shows high antitumor activity with enhanced liver targeting and improved oral absorption. It is significant to further investigate the possible anticancer mechanism of G2 for its further clinical research and application.

OBJECTIVE

We aimed to unearth the anticancer mechanism of G2 in HepG2 and HCT116 cells.

METHODS

Cell viability was measured using MTT assay; cell cycle, Mitochondrial Membrane Potential (MMP), and cell apoptosis were detected by flow cytometer; ROS was measured by Fluorescent Microplate Reader; the mRNA and protein levels of cell cycle-related and apoptosis-associated proteins were examined by RT-PCR and western blot, respectively.

RESULTS

We found that G2 inhibited cells proliferation of HepG2 and HCT116 remarkably in a dosedependent manner. Moreover, G2-treatment led to S and G2/M phase arrest in both cells, which could be elucidated by the change of mRNA levels of p21, p27 and Cyclin E and the increased protein level of p21. G2 also induced dramatically ROS accumulated and MMP decreased, which contributed to the apoptosis through activation of both the extrinsic and intrinsic pathways via changing the genes and proteins expression involved in apoptosis pathway in both of HepG2 and HCT116 cells.

CONCLUSION

These findings suggested that the apoptosis in both cell lines induced by G2 was related to the extrinsic and intrinsic pathways.

Avenanthramide A triggers potent ROS-mediated anti-tumor effects in colorectal cancer by directly targeting DDX3

Colorectal cancer (CRC) is a common malignant gastrointestinal tumor with high mortality worldwide. Drug resistance and cytotoxicity to normal cells are the main causes of chemotherapeutic treatment failure in CRC. Therefore, extracting the bioactive compounds from natural products with anti-carcinogenic activity and minimal side-effects is a promising strategy against CRC. The present study aims to evaluate the anti-carcinogenic properties of avenanthramides (AVNs) extracted from oats bran and clarify the underlying molecular mechanisms. We demonstrated that AVNs treatment suppressed mitochondrial bioenergetic generation, resulting in mitochondrial swelling and increased reactive oxygen species (ROS) production. Further study indicated that AVNs treatment significantly reduced DDX3 expression, an oncogenic RNA helicase highly expressed in human CRC tissues. DDX3 overexpression reversed the ROS-mediated CRC apoptosis induced by AVNs. Of note, we identified Avenanthramide A (AVN A) as the effective ingredient in AVNs extracts. AVN A blocked the ATPase activity of DDX3 and induced its degradation by directly binding to the Arg287 and Arg294 residues in DDX3. In conclusion, these innovative findings highlight that AVNs extracts, in particular its bioactive compound AVN A may crack the current hurdles in the way of CRC treatment.

PKM2 is the target of proanthocyanidin B2 during the inhibition of hepatocellular carcinoma

BACKGROUND

The treatment for advanced primary hepatocellular carcinoma (HCC) is sorafenib (SORA), while HCC has become increasingly drug resistant with enhanced aerobic glycolysis. The present study aimed to examine the chemotherapeutic effects of a flavonoid proanthocyanidin B2 (PB2) on HCC.

METHODS

Five kinds of HCC cell lines and LO2 were used to test the effect of PB2 on aerobic glycolysis. The proliferation, cell cycle, apoptosis and a xenograft mouse model were analyzed. Lentivirus overexpressed pyruvate kinase M2 (PKM2) or sh-PKM2 was used to verify the target of PB2. The detailed mechanism was investigated by immunofluorescence, co-immunoprecipitation, and western blotting.

RESULTS

PB2 inhibited the proliferation, induced cell cycle arrest, and triggered apoptosis of HCC cells in vivo and in vitro. PB2 also suppressed glucose uptake and lactate levels via the direct inhibition of the key glycolytic enzyme, PKM2. In addition, PKM2 inhibited the nuclear translocation of PKM2 and co-localization of PKM2/HIF-1α in the nucleus, leading to the inhibition of aerobic glycolysis. Co-treatment with PB2 was also effective in enhancing the chemosensitivity of SORA.

CONCLUSIONS

PB2 inhibited the expression and nuclear translocation of PKM2, therefore disrupting the interaction between PKM2/HSP90/HIF-1α, to suppress aerobic glycolysis and proliferation, and trigger apoptosis in HCC via HIF-1α-mediated transcription suppression.