The Role of Glycyrrhizin, an Inhibitor of HMGB1 Protein, in Anticancer Therapy

Impact of HMGB1 on cancer development and therapeutic insights focused on CNS malignancy

The present study explores the complex roles of High Mobility Group Box 1 (HMGB1) in the context of cancer development, emphasizing glioblastoma (GBM) and other central nervous system (CNS) cancers. HMGB1, primarily known for its involvement in inflammation and angiogenesis, emerges as a multifaceted player in the tumorigenesis of GBM. The overexpression of HMGB1 correlates with glioma malignancy, influencing key pathways like RAGE/MEK/ERK and RAGE/Rac1. Additionally, HMGB1 secretion is linked to the maintenance of glioma stem cells (GSCs) and contributes to the tumor microenvironment's (TME) vascular leakiness. Henceforth, our review discusses the bidirectional impact of HMGB1, acting as both a promoter of tumor progression and a mediator of anti-tumor immune responses. Notably, HMGB1 exhibits tumor-suppressive roles by inducing apoptosis, limiting cellular proliferation, and enhancing the sensitivity of GBM to therapeutic interventions. This dualistic nature of HMGB1 calls for a nuanced understanding of its implications in GBM pathogenesis, offering potential avenues for more effective and personalized treatment strategies. The findings underscore the need to explore HMGB1 as a prognostic marker, therapeutic target, and a promising tool for stimulating anti-tumor immunity in GBM.

Directing in Vitro Selection towards G-quadruplex-forming Aptamers to Inhibit HMGB1 Pathological Activity

In the search for novel, effective inhibitors of High-Mobility Group Box1 (HMGB1)-a protein involved in various inflammatory and autoimmune diseases as well as in cancer-we herein discovered a set of anti-HMGB1 G-quadruplex(G4)-forming aptamers by using an in vitro selection procedure applied to a doped library of guanine-rich oligonucleotides. The selected DNA sequences were then studied in a pseudo-physiological buffer mimicking the extracellular medium, where HMGB1 exerts its pathological activity, using spectroscopic, electrophoretic, and chromatographic techniques. All the oligonucleotides proved to fold into monomeric G4s and in some cases also dimeric species, stable at physiological temperature. Remarkably, the protein preferentially recognized the sequences forming dimeric parallel G4 structures, as evidenced by a properly designed chemiluminescent binding assay which also highlighted a good selectivity of these aptamers for HMGB1. Moreover, all aptamers showed anti-HMGB1 activity, inhibiting protein-induced cell migration. The acquired data allowed identifying L12 as the best anti-HMGB1 aptamer, featured by high thermal and enzymatic stability, no toxicity at least up to 5 μM concentration on healthy cells, along with potent anti-HMGB1 activity (IC50 ca. 28 nM) and good binding affinity for the protein, thus indicating it as a very promising lead candidate for in vivo studies.

Advances in the roles of glycyrrhizic acid in cancer therapy

Since the first 70 years of reporting cancer chemotherapy, malignant tumors have been the second most common cause of death in children and adults. Currently, the commonly used anti-cancer methods include surgery, chemotherapy, radiotherapy, and immunotherapy. Although these treatment methods could alleviate cancer, they lead to different forms of side effects and have no particularly significant effect on prolonging the patients' life span. Glycyrrhizic acid (GL), a native Chinese herbal extract, has a wide range of pharmacological effects, such as anti-cancer, anti-inflammatory, antioxidant, and immune regulation. In this review, the anti-cancer effects and mechanisms of GL are summarized in various cancers. The inhibition of GL on chemotherapy-induced side effects, including hepatotoxicity, nephrotoxicity, genotoxicity, neurotoxicity and pulmonary toxicity, is highlighted. Therefore, GL may be a promising and ideal drug for cancer therapy.

Inhibition of DAMP actions in the tumoral microenvironment using lactoferrin-glycyrrhizin conjugate for glioblastoma therapy

BACKGROUND

High-mobility group box-1 (HMGB1) released from the tumor microenvironment plays a pivotal role in the tumor progression. HMGB1 serves as a damaged-associated molecular pattern (DAMP) that induces tumor angiogenesis and its development. Glycyrrhizin (GL) is an effective intracellular antagonist of tumor released HMGB1, but its pharmacokinetics (PK) and delivery to tumor site is deficient. To address this shortcoming, we developed lactoferrin-glycyrrhizin (Lf-GL) conjugate.

METHODS

Biomolecular interaction between Lf-GL and HMGB1 was evaluated by surface plasmon resonance (SPR) binding affinity assay. Inhibition of tumor angiogenesis and development by Lf-GL attenuating HMGB1 action in the tumor microenvironment was comprehensively evaluated through in vitro, ex vivo, and in vivo. Pharmacokinetic study and anti-tumor effects of Lf-GL were investigated in orthotopic glioblastoma mice model.

RESULTS

Lf-GL interacts with lactoferrin receptor (LfR) expressed on BBB and GBM, therefore, efficiently inhibits HMGB1 in both the cytoplasmic and extracellular regions of tumors. Regarding the tumor microenvironment, Lf-GL inhibits angiogenesis and tumor growth by blocking HMGB1 released from necrotic tumors and preventing recruitment of vascular endothelial cells. In addition, Lf-GL improved the PK properties of GL approximately tenfold in the GBM mouse model and reduced tumor growth by 32%. Concurrently, various biomarkers for tumor were radically diminished.

CONCLUSION

Collectively, our study demonstrates a close association between HMGB1 and tumor progression, suggesting Lf-GL as a potential strategy for coping with DAMP-related tumor microenvironment. HMGB1 is a tumor-promoting DAMP in the tumor microenvironment. The high binding capability of Lf-GL to HMGB1 inhibits tumor progression cascade such as tumor angiogenesis, development, and metastasis. Lf-GL targets GBM through interaction with LfR and allows to arrest HMGB1 released from the tumor microenvironment. Therefore, Lf-GL can be a GBM treatment by modulating HMGB1 activity.

Identification of the Mechanism of Matrine Combined with Glycyrrhizin for Hepatocellular Carcinoma Treatment through Network Pharmacology and Bioinformatics Analysis

Matrine and glycyrrhizin are representative active ingredients of traditional Chinese medicine (TCM) used in clinical practice. Studies have demonstrated that matrine has antitumor pharmacological effects and that glycyrrhizin protects liver function. However, the potential bioactive compounds and mechanisms remain unknown, as well as whether they have synergistic effects in killing cancer cells and protecting liver cells. To investigate the synergistic effects and mechanism of matrine combined with glycyrrhizin in hepatocellular carcinoma (HCC) treatment, we used both network pharmacology and bioinformatics analyses. First, the chemical gene interaction information of matrine and glycyrrhizin was obtained from the PubChem database. The pathogenic genes of HCC were accessed from five public databases. The RNA sequencing data and clinical information of HCC patients were downloaded from The Cancer Genome Atlas (TCGA). Next, the overlapping genes among the potential targets of matrine and glycyrrhizin and HCC-related targets were determined using bioinformatics analysis. We constructed the drug-target interaction network. Prognosis-associated genes were acquired through the univariate Cox regression model and Lasso-Cox regression model. The results were verified by the International Cancer Genome Consortium (ICGC) database. Finally, we predicted the immune function of the samples. The drug-target interaction network consisted of 10 matrine and glycyrrhizin targets. We selected a Lasso-Cox regression model consisting of 3 differentially expressed genes (DEGs) to predict the efficacy of the combination in HCC. Subsequently, we successfully predicted the overall survival of HCC patients using the constructed prognostic model and investigated the correlation of the immune response. Matrine and glycyrrhizin have synergistic effects on HCC. The model we obtained consisted of three drug-target genes by Lasso-Cox regression analysis. The model independently predicted the combined effect of matrine and glycyrrhizin in HCC treatment and OS, which will be helpful for guiding clinical treatment. The prognostic model was correlated with the immune cells and immune checkpoints of patients, which had an adjuvant effect on HCC immunotherapy. Matrine and glycyrrhizin can have therapeutic effects on HCC by promoting the production or enhancing the core gene activity in the drug network and improving the immune system function of patients.

Extracellular HMGB1 as Inflammatory Mediator in the Progression of Mycoplasma Gallisepticum Infection

High-mobility group box 1 (HMGB1), a member of damage-associated molecular patterns (DAMPs), is involved in the immune regulation of several infectious diseases. Mycoplasma gallisepticum (MG) infection is proved to cause an abnormal immune response, but the role of HMGB1 in MG-induced chronic respiratory disease (CRD) is unclear. In this study, we found that HMGB1 was released from the nucleus to the extracellular in macrophages upon infection with MG. Extracellular HMGB1 bound to TLR2 activating the NF-κB pathway triggering a severe inflammatory storm and promoting the progression of MG infection. More importantly, TLR4 could be activated by HMGB1 to trigger immune disorders after TLR2 was silenced. This disease process could be interrupted by ethyl pyruvate (EP) inhibition of HMGB1 release or glycyrrhizic acid (GA). Furthermore, treatment of MG-infected chickens with GA significantly alleviated immune organ damage. In conclusion, we demonstrate that HMGB1 is secreted extracellularly to form an inflammatory environment upon MG infection, triggering a further cellular inflammatory storm in a positive feedback approach. Blocking MG-induced HMGB1 release or suppression downstream of the HMGB1-TLR2/TLR4 axis may be a promising novel strategy for the treatment of CRD. Furthermore, this study may provide a theoretical reference for understanding non-LPS-activated TLR4 events.

Inhibition of HMGB1/RAGE Signaling Reduces the Incidence of Medication-Related Osteonecrosis of the Jaw (MRONJ) in Mice

Medication-related osteonecrosis of the jaw (MRONJ) is a severe complication of antiresorptive or antiangiogenic medications, used in the treatment of bone malignancy or osteoporosis. Bone necrosis, mainly represented by osteocytic death, is always present in MRONJ sites; however, the role of osteocyte death in MRONJ pathogenesis is unknown. High mobility group box 1 (HMGB1) is a non-histone nucleoprotein that in its acetylated form accumulates in the cytoplasm, whereas non-acetylated HMGB1 localizes in the nucleus. SIRT1 deacetylase regulates cellular localization of HMGB1. Interestingly, HMGB1 is released during cell necrosis and promotes inflammation through signaling cascades, including activation of the RAGE receptor. Here, we utilized a well-established mouse MRONJ model that utilizes ligature-induced experimental periodontitis (EP) and treatment with either vehicle or zolendronic acid (ZA). Initially, we evaluated HMGB1-SIRT1 expression in osteocytes at 1, 2, and 4 weeks of treatment. Significantly increased cytoplasmic and perilacunar HMGB1 expression was observed at EP sites of ZA versus vehicle (Veh) animals at all time points. SIRT1 colocalized with cytoplasmic HMGB1 and presented a statistically significant increased expression at the EP sites of ZA animals for all time points. RAGE expression was significantly higher in the submucosal tissues EP sites of ZA animals compared with those in vehicle group. To explore the significance of increased cytoplasmic and extracellular HMGB1 and increased RAGE expression in MRONJ pathogenesis, we used pharmacologic inhibitors of these molecules. Combined HMGB1/RAGE inhibition resulted in lower MRONJ incidence with statistically significant decrease in osteonecrotic areas and bone exposure versus non-inhibitor treated ZA animals. Together, our data point to the role of HMGB1 as a central alarmin, overexpressed at early phase of MRONJ pathogenesis during osteocytic death. Moreover, HMGB1-RAGE pathway may represent a new promising therapeutic target in patients at high risk of MRONJ. © 2022 American Society for Bone and Mineral Research (ASBMR).

Large-scale prediction of key dynamic interacting proteins in multiple cancers

Tracking cancer dynamic protein-protein interactions (PPIs) and deciphering their pathogenesis remain a challenge. We presented a dynamic PPIs' hypothesis: permanent and transient interactions might achieve dynamic switchings from normal cells to malignancy, which could cause maintenance functions to be interrupted and transient functions to be sustained. Based on the hypothesis, we first predicted >1400 key cancer genes (KCG) by applying PPI-express we proposed to 18 cancer gene expression datasets. We then further screened out key dynamic interactions (KDI) of cancer based on KCG and transient and permanent interactions under both conditions. Two prominent functional characteristics, "Cell cycle-related" and "Immune-related", were presented for KCG, suggesting that these might be their general characteristics. We found that, compared to permanent to transient KDI pairs (P2T) in the network, transient to permanent (T2P) have significantly higher edge betweenness (EB), and P2T pairs tending to locate intra-functional modules may play roles in maintaining normal biological functions, while T2P KDI pairs tending to locate inter-modules may play roles in biological signal transduction. It was consistent with our hypothesis. Also, we analyzed network characteristics of KDI pairs and their functions. Our findings of KDI may serve to understand and explain a few hallmarks of cancer.

Jieduan–Niwan Formula Ameliorates Oxidative Stress and Apoptosis in Acute-on-Chronic Liver Failure by Suppressing HMGB1/TLR-4/NF-κB Signaling Pathway: A Study In Vivo and In Vitro

Jieduan-Niwan (JDNW) formula is a traditional Chinese medicine compound created by the famous Chinese medicine expert Professor Qian Ying, and has been used clinically for decades to treat acute-on-chronic liver failure (ACLF) and exhibits remarkable efficacy. However, the exact mechanism remains to be discovered. As an important hepatocyte damage-associated molecular patterns (DAMP) factor, high mobility group box 1 (HMGB1) is a potential therapeutic target as an accelerator of ACLF in the pathogenesis. Therefore, the present study investigated whether JDNW inhibits the overexpression and cytoplasmic translocation of HMGB1 in ACLF liver tissue and alleviates its mediated oxidative stress and apoptosis. In vivo, an immune-induced ACLF rat model was established, and then treated with JDNW for 5, 10, and 15 d. The results showed that a large number of cytoplasmic translocations of HMGB1 occurred in the ACLF group. And there was an increase in the expression of HMGB1 in the M-5 d group. After the intervention of JDNW, the overexpression and translocation of HMGB1 were inhibited. In vitro, D-GaLN caused an increase in the expression and translocation of HMGB1 in L02 cells. Similar to the inhibitor of HMGB1, JDNW serum alleviated this kind of increase. Further tests showed that JDNW attenuated ACLF-related oxidative stress and apoptosis, and the inhibition was associated with the regulation of TLR-4/NF-κB signaling pathway. In conclusion, our present findings suggest that the therapeutic effect of JDNW on ACLF was associated with the inhibition of high expression and cytoplasmic translocation of HMGB1 during the acute injury phase, thus, attenuating oxidative stress injury and apoptosis induced by HMGB1/TLR-4/NF-κB pathway.

Targeting HMGB1-NFκb Axis and miR-21 by Glycyrrhizin: Role in Amelioration of Corneal Injury in a Mouse Model of Alkali Burn

Corneal neovascularization (CNV) is a sight-threatening condition usually associated with various inflammatory settings including chemical injury. High mobility group box 1 (HMGB1) is identified as an inflammatory alarmin in diverse tissue damage. Here, we evaluate the expression of HMGB1 and the consequences of its inhibition through its selective inhibitor glycyrrhizin (GLY) in alkali burn-induced corneal inflammation and neovascularization. GLY effectively attenuated alkali burn-induced HMGB1 expression at both mRNA and protein levels. Furthermore, slit-lamp analysis, ink perfusion, H&E staining, and CD31 histochemical staining showed that GLY relieved corneal neovascularization, while GLY attenuated VEGF expression via inhibiting HMGB1/NF-κB/HIF-1α signal pathway. In addition, GLY treatment decreased the cytokine expression of CCL2 and CXCL5, accompanied by the reduction of their receptors of CCR2 and CXCR2. GLY diminished the inflammatory cell infiltration of the cornea, as well as reduced the expression of IL-1β, IL-6, and TNF-α. Moreover, treatment with GLY reduced the degree of cornea opacity through inactivating extracellular HMGB1 function, which otherwise induces TGF-β1 release and myofibroblast differentiation. Furthermore, we found that GLY treatment attenuated the upregulation of miR-21 levels in alkali burned cornea; while inhibition of miR-21in keratocytes in vitro, significantly inhibited TGF-β1-induced myofibroblast differentiation. Collectively, our results suggested that targeting HMGB1-NFκb axis and miR-21 by GLY could introduce a therapeutic approach to counter CNV.

Recent advances in glycyrrhizin metabolism, health benefits, clinical effects and drug delivery systems for efficacy improvement; a comprehensive review

BACKGROUND

Glycyrrhizin (GL) is a major active constituent of licorice root (Glycyrrhiza glabra) that is considered one of the oldest and most frequently employed botanicals in Chinese medicine and worldwide, with most effects attributed to its rich GL content. Structurally, GL a triterpene saponin that is widely used as a flavoring agent in foodstuffs and cosmetics, and also proposed for various clinical applications with a myriad of health benefits. Pharmacological and biological activities of GL include antiviral, anti-inflammatory, antioxidant, and anticancer activities (in vitro and in vivo). Currently, there is no comprehensive review on GL biological effects and its action mechanisms.

PURPOSE

This review summarizes GL pharmacological actions from a molecular biology perception, presented on its metabolism and side effects based on in vitro, in vitro and clinical studies. Moreover, the potential of GL as a nanomedicine delivery system is also summarized. The progress in drug delivery research using GL presented herein is expected to provide a theoretical basis for developing other novel drugs formulations.

METHODS

A systematic review was carried out in several electronic databases (Science Direct, SpringerLink, CNKI, PubMed, Web of Science, Elsevier, and Scopus), using the following key words: glycyrrhizin "AND" bioactivity "OR" clinic "OR" therapeutic "OR" drug delivery. This search included manuscripts published between 1989 and 2021.

RESULTS

126 researches were selected and summarized in this review. The analysis of these studies indicated that GL has antiviral activity against different viruses. Further, GL efficiently suppressed the respiratory manifestations associated with COVID-19 by reducing the expression of angiotensin converting enzyme 2 (ACE2) that employed by the virus as an entry point. Otherwise, GL was found to induce antioxidant, anti-inflammatory, immune-modulatory, and anticancer activity. Besides, diminution the particle size of GL to nanometer size significantly augments their action and biodistribution.

CONCLUSION

This article summarizes the pharmacological actions of GL. The potential of GL as a nanomedicine delivery system is also presented. Nevertheless, most studies reported provide no deep insight of GL health effects warranting for more future studies to elucidate its action mechanism and potential therapeutic benefits through preclinical and clinical trials.

Quercetin Reduces Oxidative Stress and Apoptosis by Inhibiting HMGB1 and Its Translocation, Thereby Alleviating Liver Injury in ACLF Rats

Background

Acute on chronic liver failure (ACLF) is a syndrome of acute liver failure that occurs on the basis of chronic liver disease, which is characterized by a rapid deterioration in a short period and high mortality. High mobility group box 1 (HMGB1) may be involved in the pathological process of ACLF; its specific role remains to be further elucidated. Our previous studies have shown that quercetin (Que) exerts anti-oxidant and anti-apoptotic effects by inhibiting HMGB1 in vitro. The present study aimed to investigate the effect of Que on liver injury in ACLF rats.

Methods

The contents of ALT, AST, TBiL, and PT time of rats in each group were observed. HE staining was used to detect liver pathology. The levels of oxidative stress indicators such as MDA, GSH, and 4-HNE in the rat liver were detected. TUNEL assay was used to detect apoptosis in rat hepatocytes. Immunofluorescence and western blot analysis were performed to explore the protective effect of Que on ACLF rats and the underlying mechanism.

Results

The results showed that Que could reduce the increase of serum biochemical indices, improve liver pathology, and reduce liver damage in ACLF rats. Further results confirmed that Que reduced the occurrence of oxidative stress and apoptosis of hepatocytes, and these reactions may aggravate the progress of ACLF. Meanwhile, the results of immunofluorescence and western blotting also confirmed that the expression of HMGB1 and extranuclear translocation in ACLF rat hepatocytes were significantly increased, which was alleviated by the treatment of Que. In addition, when cotreated with glycyrrhizin (Gly), an inhibitor of HMGB1, the inhibition of Que on HMGB1 and its translocation, apoptosis and oxidative stress, and the related proteins of HMGB1-mediated cellular pathway have been significantly enhanced.

Conclusion

Thus, Que alleviates liver injury in ACLF rats, and its mechanism may be related to oxidative stress and apoptosis caused by HMGB1 and its translocation.

Potential effects of HMGB1 on viral replication and virus infection-induced inflammatory responses: A promising therapeutic target for virus infection-induced inflammatory diseases

Inflammatory responses, characterized by the overproduction of numerous proinflammatory mediators by immune cells, is essential to protect the host against invading pathogens. Excessive production of proinflammatory cytokines is a key pathogenic factor accounting for severe tissue injury and disease progression during the infection of multiple viruses, which are therefore termed as "cytokine storm". High mobility group box 1 (HMGB1), a ubiquitous DNA-binding protein released either over virus-infected cells or activated immune cells, may act as a proinflammatory cytokine with a robust capacity to potentiate inflammatory response and disease severity. Moreover, HMGB1 is a host factor that potentially participates in the regulation of viral replication cycles with complicated mechanisms. Currently, HMGB1 is regarded as a promising therapeutic target against virus infection. Here, we provide an overview of the updated studies on how HMGB1 is differentially manipulated by distinct viruses to regulate viral diseases.

Glycyrrhetinic acid: a promising scaffold for the discovery of anticancer agents

INTRODUCTION

Oleanane-type pentacyclic triterpenes named glycyrrhetinic acids (GAs) featuring a C-30 carboxylic acid group, are extracted from the licorice (Glycyrrhiza uralensis). Numerous biological properties of GA have been reported and have attracted researchers from all over the world in recent years due to the peculiar GA scaffold-based semisynthetic cytotoxic effects.

AREAS COVERED

This review represents the applications of semisynthetic derivatives of GA for the development of future cancer treatments. Included in the review are important structural features of the semisynthetic GAs crucial for cytotoxic effects.

EXPERT OPINION

Numerous semisynthetic GA derivatives illustrated excellent cytotoxic effects toward various cancer cells. Notably the C-₃(OH) at ring A along with C_30-CO₂H at ring E as vital structural features, make GA very appealing as a lead scaffold for medicinal chemistry, since these two groups permit the creation of further chemical diversity geared toward improved cytotoxic effects. Furthermore, numerous GA derivatives have been synthesized and indicate that compounds featuring cyanoenone moieties in ring A, or compounds having the amino group or nitrogen comprising heterocycles and hybrids thereof, illustrate more potent cytotoxicity. Furthermore, GA has a great capability to be conjugated with other anticancer molecules to synergistically enhance their combined cytotoxicity.

Glycyrrhizin Attenuates Portal Hypertension and Collateral Shunting via Inhibition of Extrahepatic Angiogenesis in Cirrhotic Rats

Portal hypertension develops along with liver cirrhosis then induces the formation of portal-systemic collaterals and lethal complications. Extrahepatic angiogenesis plays an important role. Glycyrrhizin has been found to exhibit anti-angiogenic features, which leads to its extensive use. However, the relevant effects of glycyrrhizin on liver cirrhosis and portal hypertension have not been evaluated. This study thus aimed to investigate the impact of glycyrrhizin on portal hypertension-related derangements in cirrhotic rats. Male Sprague-Dawley rats received bile duct ligation (BDL) to induce cirrhosis or sham operation as control. The rats were subdivided to receive glycyrrhizin (150 mg/kg/day, oral gavage) or vehicle beginning on the 15th day post operation, when BDL-induced liver fibrosis developed. The effects of glycyrrhizin were determined on the 28th day, the typical timing of BDL-induced cirrhosis. Glycyrrhizin significantly reduced portal pressure (p = 0.004). The splanchnic inflow as measured by superior mesenteric arterial flow decreased by 22% (p = 0.029). The portal-systemic collateral shunting degree reduced by 30% (p = 0.024). The mesenteric angiogenesis and phospho-VEGFR2 protein expression were also downregulated (p = 0.038 and 0.031, respectively). Glycyrrhizin did not significantly influence the liver biochemistry data. Although glycyrrhizin tended to reverse liver fibrosis, statistical significance was not reached (p = 0.069). Consistently, hepatic inflow from portal side, hepatic vascular resistance, and liver fibrosis-related protein expressions were not affected. Glycyrrhizin treatment at the stage of hepatic fibrosis still effectively attenuated portal hypertension and portosystemic collateral shunting. These beneficial effects were attributed to, at least in part, the suppression of mesenteric angiogenesis by VEGF signaling pathway downregulation.

Preclinical Evidence for the Pharmacological Actions of Glycyrrhizic Acid: A Comprehensive Review

Glycyrrhiza glabra L. (Family: Fabaceae) is one of the important traditional medicinal plant used extensively in folk medicine. It is known for its ethnopharmacological value in curing a wide variety of ailments. Glycyrrhizin, an active compound of G. glabra, possesses anti-inflammatory activity due to which it is mostly used in traditional herbal medicine for the treatment and management of chronic diseases. The present review is focused extensively on the pharmacology, pharmacokinetics, toxicology, and potential effects of Glycyrrhizic Acid (GA). A thorough literature survey was conducted to identify various studies that reported on the GA on PubMed, Science Direct and Google Scholar.

Could Targeting HMGB1 be Useful for the Clinical Management of COVID-19 Infection?

Since the high mobility group box-1 (HMGB1) molecule had been recognized as a proinflammatory cytokine, which mediates endotoxin lethality of mice, there have been lots of papers about targeting the HMGB1 within the contexts of infection, inflammation, and cancer. The pathogenic impact of HMGB1 to the severe acute respiratory syndrome (SARS) and disease management with herbal formulations targeting this unique protein have already been proposed. However, the failure of the numerous current anti-viral therapies on the ongoing viral infections casts reappraisal of the possible interrelationships regarding the HMGB1 and SARS-CoV-2. COVID-19 pandemic due to the SARS-CoV-2 virus is a currently ongoing challenging global health crisis. There is still not any proven exact treatment of COVID-19 with high level of evidence. In this paper, we focused on the potential usage of external and/or inhalation preparation of antiviral/antibacterial herbal products capable of targeting HMGB1 for the clinical management candidates of the ongoing COVID-19 infection.

Glycyrrhizin Attenuates Carcinogenesis by Inhibiting the Inflammatory Response in a Murine Model of Colorectal Cancer

Glycyrrhizin (GL), an important active ingredient of licorice root, which weakens the proinflammatory effects of high-mobility group box 1 (HMGB1) by blocking HMGB1 signaling. In this study, we investigated whether GL could suppress inflammation and carcinogenesis in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced murine model of colorectal cancer. ICR mice were divided into four groups (n = 5, each)—control group, GL group, colon cancer (CC) group, and GL-treated CC (CC + GL) group, and sacrificed after 20 weeks. Plasma levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were measured using an enzyme-linked immunosorbent assay. The colonic tissue samples were immunohistochemically stained with DNA damage markers (8-nitroguanine and 8-oxo-7,8-dihydro-2′-deoxy-guanosine), inflammatory markers (COX-2 and HMGB1), and stem cell markers (YAP1 and SOX9). The average number of colonic tumors and the levels of IL-6 and TNF-α in the CC + GL group were significantly lower than those in the CC group. The levels of all inflammatory and cancer markers were significantly reduced in the CC + GL group. These results suggest that GL inhibits the inflammatory response by binding HMGB1, thereby inhibiting DNA damage and cancer stem cell proliferation and dedifferentiation. In conclusion, GL significantly attenuates the pathogenesis of AOM/DSS-induced colorectal cancer by inhibiting HMGB1-TLR4-NF-κB signaling.

Advances in Pharmacological Activities and Mechanisms of Glycyrrhizic Acid

Licorice (Glycyrrhiza glabra L.) is widely regarded as an important medicinal plant and has been used for centuries in traditional medicine because of its therapeutic properties. Studies have shown that metabolites isolated from licorice have many pharmacological activities, such as antiinflammatory, anti-viral, participation in immune regulation, anti-tumor and other activities. This article gives an overview of the pharmacological activities and mechanisms of licorice metabolites and the adverse reactions that need attention. This review helps to further investigate the possibility of licorice as a potential drug for various diseases. It is hoped that this review can provide a relevant theoretical basis for relevant scholars' research and their own learning.

High mobility group box 1 (HMGB1): a pivotal regulator of hematopoietic malignancies

High mobility group box 1 (HMGB1) is a nonhistone chromatin-associated protein that has been widely reported to play a pivotal role in the pathogenesis of hematopoietic malignancies. As a representative damage-associated molecular pattern (DAMP), HMGB1 normally exists inside cells but can be secreted into the extracellular environment through passive or active release. Extracellular HMGB1 binds with several different receptors and interactors to mediate the proliferation, differentiation, mobilization, and senescence of hematopoietic stem cells (HSCs). HMGB1 is also involved in the formation of the inflammatory bone marrow (BM) microenvironment by activating proinflammatory signaling pathways. Moreover, HMGB1-dependent autophagy induces chemotherapy resistance in leukemia and multiple myeloma. In this review, we systematically summarize the emerging roles of HMGB1 in carcinogenesis, progression, prognosis, and potential clinical applications in different hematopoietic malignancies. In summary, targeting the regulation of HMGB1 activity in HSCs and the BM microenvironment is highly beneficial in the diagnosis and treatment of various hematopoietic malignancies.

Antifibrotic Effects of High-Mobility Group Box 1 Protein Inhibitor (Glycyrrhizin) on Keloid Fibroblasts and Keloid Spheroids through Reduction of Autophagy and Induction of Apoptosis

Overabundance of extracellular matrix resulting from hyperproliferation of keloid fibroblasts (KFs) and dysregulation of apoptosis represents the main pathophysiology underlying keloids. High-mobility group box 1 (HMGB1) plays important roles in the regulation of cellular death. Suppression of HMGB1 inhibits autophagy while increasing apoptosis. Suppression of HMGB1 with glycyrrhizin has therapeutic benefits in fibrotic diseases. In this study, we explored the possible involvement of autophagy and HMGB1 as a cell death regulator in keloid pathogenesis. We have highlighted the potential utility of glycyrrhizin as an antifibrotic agent via regulation of the aberrant balance between autophagy and apoptosis in keloids. Higher HMGB1 expression and enhanced autophagy were observed in keloids. The proliferation of KFs was decreased following glycyrrhizin treatment. While apoptosis was enhanced in keloids after glycyrrhizin treatment, autophagy was significantly reduced. The expressions of ERK1/2, Akt, and NF-κB, were enhanced in HMGB1-teated fibroblasts, but decreased following glycyrrhizin treatment. The expression of extracellular matrix (ECM) components was reduced in glycyrrhizin-treated keloids. TGF-β, Smad2/3, ERK1/2, and HMGB1 were decreased in glycyrrhizin-treated keloids. Treatment with the autophagy inhibitor 3-MA resulted in a decrease of autophagy markers and collagen in the TGF-β-treated fibroblasts. The results indicated that autophagy plays an important role in the pathogenesis of keloids. Because glycyrrhizin appears to reduce ECM and downregulate autophagy in keloids, its potential use for treatment of keloids is indicated.

Polyamine-stimulation of arsenic-transformed keratinocytes

Tumor promotion is strongly associated with inflammation and increased polyamine levels. Our understanding of relevant mechanisms responsible for arsenic-induced cancer remains limited. Previous studies suggest that arsenic targets and dysregulates stem cell populations that remain dormant in the skin until promoted to be recruited out of the bulge stem cell region, thus giving rise to skin tumors. In this study, we explored a possible mechanism by which increased keratinocyte polyamine biosynthesis promotes tumorsphere formation and invasiveness of arsenic-transformed HaCaT keratinocytes (As-HaCaT). Unlike parental HaCaT cells, As-HaCaT cells were tumorigenic in athymic nude mice, and the CD45negative epithelial tumor cells had enriched expression of Toll-Like Receptor 4 (TLR4), CD34 and CXCR4 as did As-HaCaT tumorsphere cultures compared to As-HaCaT monolayer cultures. Ornithine decarboxylase (ODC) overexpressing keratinocytes (Ker/ODC) release increased levels of the alarmin high mobility group box 1 (HMGB1). Ker/ODC conditioned medium (CM) stimulated As-HaCaT but not parental HaCaT tumorsphere formation, and this was inhibited by glycyrrhizin, an inhibitor of HMGB1, and by TAK242, an inhibitor of the HMGB1 receptor TLR4. Compared to parental HaCaT cells, As-HaCaT cells demonstrated greater invasiveness across a Matrigel-coated filter using either fibroblast CM or SDF-1α as chemoattractants. Addition of Ker/ODC CM or HMGB1 dramatically increased As-HaCaT invasiveness. Glycyrrhizin and TAK242 inhibited this Ker/ODC CM-stimulated invasion of As-HaCaT cells but not HaCaT cells. These results show that polyamine-dependent release of HMGB1 promotes the expansion of stem cell-like subpopulations in arsenic-transformed keratinocytes while also increasing their invasiveness, suggesting that polyamines may be a potential therapeutic target for the prevention and treatment of arsenic-initiated skin cancers.

Impaired dendritic cell functions in lung cancer: a review of recent advances and future perspectives

Lung cancer is the leading cause of cancer mortality worldwide. Dendritic cells (DCs) are the key factors providing protective immunity against lung tumors and clinical trials have proven that DC function is reduced in lung cancer patients. It is evident that the immunoregulatory network may play a key role in the failure of the immune response to terminate tumors. Lung tumors likely employ numerous strategies to suppress DC-based anti-tumor immunity. Here, we summarize the recent advances in our understanding on lung tumor-induced immunosuppression in DCs, which affects the initiation and development of T-cell responses. We also describe which existing measures to restore DC function may be useful for clinical treatment of lung tumors. Furthering our knowledge of how lung cancer cells alter DC function to generate a tumor-supportive environment will be essential in order to guide the design of new immunotherapy strategies for clinical use.

The immune mediated role of extracellular HMGB1 in a heterotopic model of bladder cancer radioresistance

Radical cystectomy (RC) together with bilateral pelvic lymph node dissection remains the standard treatment for muscle invasive bladder cancer (MIBC). However, radiation-based treatments such as tri-modal therapy (TMT) involving maximally performed transurethral resection of bladder tumor (TURBT), radiotherapy (XRT), and a chemosensitizer represent an attractive, less invasive alternative. Nevertheless, 25–30% of MIBC patients will experience local recurrence after TMT and half will develop metastasis. Radioresistance of tumor cells could potentially be one of the causes for local recurrence post treatment. High mobility group box-1 (HMGB1) was shown to play a role in bladder cancer radioresistance through its intracellular functions in promoting DNA damage repair and autophagy. Recently, HMGB1 was found to be passively released from irradiated tumor cells. However, less is known about the involvement of extracellular HMGB1 in impairing radiation response and its exact role in modulating the tumor immune microenvironment after XRT. We identified a novel mechanism of bladder cancer radioresistance mediated by the immunological functions of HMGB1. The combination of radiation plus extracellular HMGB1 inhibition markedly improved the radiation response of tumors and resulted in marked changes in the immune landscape. Moreover, combining radiation and HMGB1 inhibition significantly impaired tumor infiltrating MDSCs and TAMs -but not Tregs- and shifted the overall tumor immune balance towards anti-tumoral response. We conclude that extracellular HMGB1 is involved in bladder cancer radioresistance through promoting pro-tumor immune mechanisms.

Glycyrrhizin Attenuates the Process of Epithelial-to-Mesenchymal Transition by Modulating HMGB1 Initiated Novel Signaling Pathway in Prostate Cancer Cells

High mobility group box 1 (HMGB1) is upregulated in nearly every tumor type. Importantly, clinical evidence also proposed that HMGB1 is particularly increased in metastatic prostate cancer patients. Besides, a growing number of studies highlighted that HMGB1 could be a successful therapeutic target for prostate cancer patients. Glycyrrhizin is a novel pharmacological inhibitor of HMGB1 that may repress prostate cancer metastasis. This research was aimed to investigate the effect of glycyrrhizin on inhibition of HMGB1-induced epithelial-to-mesenchymal transition (EMT), a key step of tumor metastasis, in prostate cancer cells. In this study, HMGB1 knock-downed DU145 prostate cancer cells were used. Silencing the HMGB1 gene expression triggered a change of cell morphology to a more epithelial-like shape, which was accompanied by a reduction of Cdc42/GSK-3β/Snail and induction of E-cadherin levels estimated by immunoblotting. Furthermore, HMGB1 facilitated cell migration and invasion via downstream signaling, whereas HMGB1 targeting by 10 mM ethyl pyruvate effectively inhibited EMT characteristics. Interestingly, cell migration capacity induced by HMGB1 in DU145 cells was abolished in a dose-dependent effect of 25-200 μM glycyrrhizin treatment. In conclusion, glycyrrhizin successfully inhibited HMGB1-induced EMT phenomenon, which suggested that glycyrrhizin may serves as a therapeutic agent for metastatic prostate cancer.

Glycyrrhizin Suppresses the Growth of Human NSCLC Cell Line HCC827 by Downregulating HMGB1 Level

Lung cancer has very high mortality and glycyrrhizin was found to significantly inhibit the growth of lung cancer cells in vitro and tissues in mice. However, the detailed inhibitory role of glycyrrhizin in the growth of lung cancer is still unclear. In this study, we first found that glycyrrhizin inhibited the growth of lung tumor in PDX mice. And high level of HMGB1 promoted the migration and invasion of lung cancer cells, which was suppressed by glycyrrhizin. Moreover, glycyrrhizin reduced the activity of JAK/STAT signaling pathway, which is the upstream regulator of HMGB1. Therefore, this study revealed a potential mechanism by which glycyrrhizin can inhibit the progression of lung cancer.

Intestinal Absorption of Triterpenoids and Flavonoids from Glycyrrhizae radix et rhizoma in the Human Caco-2 Monolayer Cell Model

Glycyrrhizae radix et rhizoma has been used as a traditional Chinese medicine for the treatment of various diseases. Triterpenoids and flavonoids from the plant have many beneficial effects and their chemical structures are modified in the gastrointestinal tract after oral administration. However, absorption of these triterpenoids and flavonoids still needs to be defined. Here, the uptake and transepithelial transport of the selected major triterpenoids, glycyrrhizin (1), glycyrrhetic acid-3-O-mono-β-d-glucuronide (2), and glycyrrhetinic acid (3); and the selected major flavonoids, licochalcone A (4), licochalcone B (5), licochalcone C (6), echinatin (7), isoliquiritin apioside (8), liquiritigenin (9), liquiritin apioside (10) isolated from Glycyrrhizae radix et rhizoma, were investigated in the human intestinal epithelium-like Caco-2 cell monolayer model. Compounds 3, 5–7, and 9 were designated as well-absorbed compounds, 2 and 4 were designated as moderately absorbed ones, and 1, 8, and 10 were assigned for the poorly absorbed ones. The absorption mechanism of well and moderately absorbed compound was mainly passive diffusion to pass through the human intestinal Caco-2 cell monolayer. These findings provided useful information for predicting their oral bioavailability and the clinical application.

Glycyrrhizic acid: A promising carrier material for anticancer therapy

Drug delivery systems have become an integral part of anticancer drugs today. Design of novel drug carriers may lead to significant enhancement in antineoplastic therapy. Glycyrrhizic acid (GL), which is the most important active ingredient extracted from the licorice root shows great potential as a carrier material in this field. Recent studies have indicated that the combination of GL and first-line drugs had better therapeutic effects on cancers. GL showed a series of anti-cancer-related pharmacological activities, such as broad-spectrum anti-cancer ability, resistance to the tissue toxicity caused by chemotherapy and radiation, drug absorption enhancing effects and anti-multidrug resistance (MDR) mechanisms, as a carrier material in drug delivery systems. This review introduced the current research progress on pharmacological mechanisms of GL and development of GL-based drug carriers in anti-cancer field to provide basis for the application prospects of GL. The design of novel GL-based drug delivery systems will bring new opportunities and challenges to anti-cancer therapy.

The dual role and therapeutic potential of high-mobility group box 1 in cancer

High-mobility group box 1 (HMGB1) is an abundant protein in most eukaryocytes. It can bind to several receptors such as advanced glycation end products (RAGE) and Toll-like receptors (TLRs), in direct or indirect way. The biological effects of HMGB1 depend on its expression and subcellular location. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription, telomere maintenance, and genome stability. While outside the nucleus, it possesses more complicated functions, including regulating cell proliferation, autophagy, inflammation and immunity. During tumor development, HMGB1 has been characterized as both a pro- and anti-tumoral protein by either promoting or suppressing tumor growth, proliferation, angiogenesis, invasion and metastasis. However, the current knowledge concerning the positive and negative effects of HMGB1 on tumor development is not explicit. Here, we evaluate the role of HMGB1 in tumor development and attempt to reconcile the dual effects of HMGB1 in carcinogenesis. Furthermore, we would like to present current strategies targeting against HMGB1, its receptor or release, which have shown potentially therapeutic value in cancer intervention.

HMGB1 Protein: A Therapeutic Target Inside and Outside the Cell

High-mobility group box 1 protein (HMGB1) is a nonhistone chromosomal protein discovered more than 30 years ago. It is an abundant nuclear protein that has a dual function-in the nucleus, it binds DNA and participates in practically all DNA-dependent processes serving as an architectural factor. Outside the cell, HMGB1 plays a different role-it acts as an alarmine that activates a large number of HMGB1-"competent" cells and mediates a broad range of physiological and pathological responses. This universality makes it an attractive target for innovative therapeutic strategies in the treatment of various diseases. Here we present an overview of the major nuclear and extracellular properties of HMGB1 and describe its interaction with different molecular partners as specific receptors or inhibitors, which are important for its role as a target in multiple diseases. We highlight its pivotal role as a target for cancer treatment at two aspects: first in terms of its substantial impact on the repair capacity of cancer cells, thus affecting the effectiveness of chemotherapy with the antitumor drug cis-platinum and, second, the possibility to be targeted by microRNAs influencing different pathways of human diseases, thus making it a promising candidate for a new strategy for therapeutic interventions against various pathological conditions but mainly cancer.

Glycyrrhetinic acid and its derivatives in infectious diseases

Introduction. Licorice or liquorice (Glycyrrhiza glabra, Leguminosae) is a perennial plant naturally occurring or cultivated in Europe and Asia. It was appreciated by many ancient cultures, and was employed within Arabic medicine and (beginning in the Middle Ages) in Europe folk medicine as a remedy for many diseases. Currently, the sweet flavoured root of this plant – Radix Glycyrrhizae (Liquirtiae), is widely taken for the treating of various upper respiratory tract diseases, as well as for gastric ulcer disease. It is also utilized as a sweetening and flavouring agent in the food, tobacco and pharmacy industries. The main active ingredient of liquorice is the triterpenoid saponin, glycyrrhizin, which is a mixture of calcium, magnesium and potassium salts of glycyrrhizic acid (GA). Glycyrrhizic acid is composed of an aglycone, that is 18β-glycyrrhetinic acid (GE), and a D-glucuronic acid dimer. The aim of this review is to discuss some aspects of the activity of glycyrrhetinic acid and its derivatives in infectious diseases.

State of knowledge. The pentacyclic system of glycyrrhetinic acid consists of condensed six-membered rings with a hydroxyl group at C-3, a carboxyl moiety at C-30 and a ketone functional group at C-11. Considering the presence of the above mentioned functional groups, many structural transformations have been proposed, including those by way of esterification, alkylation and reduction reactions. The introduction of various chemical residues into its structure, as well as the modification of the glycyrrhetinic acid in its pentacyclic triterpene skeleton, has led to the generation of compounds with many valuable antimicrobial, anti-parasitic, antiviral properties and modified lipophilic parameters.

Summary. In summary, glycyrrhetinic acid derivatives appear to have promise as active pharmaceutical ingredients that contain a wide range of biological and pharmacological properties.

The Neuroprotective Effect of Glycyrrhizic Acid on an Experimental Model of Focal Cerebral Ischemia in Rats

Cerebral ischemia is still one of the most important topics in neurosciences. Our study aimed to investigate the neuroprotective and anti-oxidant effects of glycyrrhizic acid on focal cerebral ischemia in rats. Twenty-four rats were divided equally into three groups. A middle cerebral artery occlusion model was performed in this study where sham and glycyrrhizic acid were administered intraperitoneally following middle cerebral artery occlusion. Group I was evaluated as control. Malondialdehyde (MDA), superoxide dismutase (SOD), and nuclear respiratory factor-1 (NRF1) levels were analyzed biochemically on the right cerebral hemisphere, while ischemic histopathological studies were completed to investigate the anti-oxidant status. Biochemical results showed that SOD and NRF1 levels were significantly increased in the glycyrrhizic acid group compared with the sham group while MDA levels were significantly decreased. On histopathological examination, cerebral edema, vacuolization, degeneration, and destruction of neurons were decreased in the glycyrrhizic acid group compared with the sham group. Cerebral ischemia was attenuated by glycyrrhizic acid administration. These observations indicate that glycyrrhizic acid may have potential as a therapeutic agent in cerebral ischemia by preventing oxidative stress.

Inhibition effect of glycyrrhizin in lipopolysaccharide-induced high-mobility group box 1 releasing and expression from RAW264.7 cells

INTRODUCTION

High-mobility group box 1 (HMGB1) is a therapeutic target for sepsis. Glycyrrhizin (GL) is the aglycone of glycyrrhizin derived from licorice. We clarified the anti-inflammatory effects of GL. We explored the anti-HMGB1 effect of GL and elucidated its molecular mechanism, which will be of benefit for sepsis treatment.

METHODS

We stimulated murine macrophage-like RAW 264.7 cells with lipopolysaccharide (LPS) and LPS + GL, then measured the expression and release of HMGB1. The expression of related signal transduction factors was detected.

RESULTS

High-mobility group box 1 was distributed mainly in the nucleus with lower cytoplasmic levels in RAW 264.7 cells before LPS stimulation. After stimulation, cytoplasmic HMGB1 levels increased gradually, whereas in nuclear fluctuation a trend of HMGB1 expression was observed. Significant upregulation of HMGB1 mRNA occurred 12 h after LPS stimulation. Glycyrrhizin prevented the transfer of HMGB1 from the nucleus to the cytoplasm and inhibited upregulation of HMGB1 mRNA induced by LPS. Phospho-p38 mitogen-activated protein kinase and activated activating protein 1 increased significantly 8 h after LPS stimulation. Tumor necrosis factor α and interleukin 6 increased 4 h after LPS stimulation and peaked at 48 h, and HMGB1 increased at 8 h. The Toll-like receptor 4/MD2/nuclear factor κB signaling pathway was activated 4 h after LPS stimulation. Glycyrrhizin inhibited this pathway.

CONCLUSIONS

Glycyrrhizin inhibited the expression and release of HMGB1 through blocking the p38 mitogen-activated protein kinase/activating protein 1 signaling pathway then inhibited the massive release of tumor necrosis factor α and interleukin 6.

Combined Tumor Cell-Based Vaccination and Interleukin-12 Gene Therapy Polarizes the Tumor Microenvironment in Mice

Tumor progression depends on tumor milieu, which influences neovasculature formation and immunosuppression. Combining immunotherapy with antiangiogenic/antivascular therapy might be an effective therapeutic approach. The aim of our study was to elaborate an anticancer therapeutic strategy based on the induction of immune response which leads to polarization of tumor milieu. To achieve this, we developed a tumor cell-based vaccine. CAMEL peptide was used as a B16-F10 cell death-inducing agent. The lysates were used as a vaccine to immunize mice bearing B16-F10 melanoma tumors. To further improve the therapeutic effect of the vaccine, we combined it with interleukin (IL)-12 gene therapy. IL-12, a cytokine with antiangiogenic properties, activates nonspecific and specific immune responses. We observed that combined therapy is significantly more effective (as compared with monotherapies) in inhibiting tumor growth. Furthermore, the tested combination polarizes the tumor microenvironment, which results in a switch from a proangiogenic/immunosuppressive to an antiangiogenic/immunostimulatory one. The switch manifests itself as a decreased number of tumor blood vessels, increased levels of tumor-infiltrating CD4⁺, CD8⁺ and NK cells, as well as lower level of suppressor lymphocytes (Treg). Our results suggest that polarizing tumor milieu by such combined therapy does inhibit tumor growth and seems to be a promising therapeutic strategy.

Autophagy-mediated HMGB1 release promotes gastric cancer cell survival via RAGE activation of extracellular signal-regulated kinases 1/2

High mobility group box-B1 (HMGB1), an autophagy activator, is crucial in tumorigenesis. However, its extracellular role and signaling in gastric cancer remain unclear. Samples were collected from gastric cancer patients and healthy controls. Immunohistochemistry and immunocytochemistry were used to determine the localization of HMGB1 in gastric cancer tissues, four gastric carcinoma cell lines (BGC-823, SGC-7901, MKN-28 and MKN-45) and a gastric epithelial cell line GES-1. Western blot analysis and ELISA were used to assess the effects of gefitinib, an epidermal growth factor receptor inhibitor, on autophagy and HMGB1 release in BGC-823 cells. MTT assay and western blot analysis assessed the effects of extracellular HMGB1 on cell proliferation and signaling transduction. Released HMGB1 promoted proliferation through activation of ERK1/2 MAPK. HMGB1 expression in gastric cancer tissues and serum was significantly increased compared to the controls and healthy serum. Gastric carcinoma cells showed an increased HMGB1 in the nuclei and cytoplasm, whereas GES-1 cells exhibited a lower HMGB1 with nuclear localization. Gefitinib increased autophagy and cytoplasmic HMGB1 release from the BGC-823 cells. Extracellular HMGB1 in autophagic cell supernatant promoted proliferation that was abolished by glycyrrhizic acid, an HMGB1 inhibitor. BGC-823 cells incubated with HMGB1 had increased ERK1/2 phosphorylation, while levels of JNK, p38 or AKT were not affected. Blocking RAGE-HMGB1 interaction with antibody or siRNA suppressed the ERK1/2 activation and gastric cancer cell growth, indicating that RAGE-mediated ERK1/2 signaling was necessary for tumor progression.

Cancer-associated fibroblasts induce high mobility group box 1 and contribute to resistance to doxorubicin in breast cancer cells

Background

Cancer-associated fibroblasts and high mobility group box 1 (HMGB1) protein have been suggested to mediate cancer progression and chemotherapy resistance. The role of such fibroblasts in HMGB1 production in breast cancer is unclear. This study aimed to investigate the effects of cancer-associated fibroblasts on HMGB1 expression in breast cancer cells and its role in chemotherapeutic response.

Methods

Breast cancer-associated fibroblasts (BCFs) and non-tumor-associated fibroblasts (NTFs) were isolated from human breast cancers or adjacent normal tissues and established as primary cultures in vitro. After confirmation of the activated status of these fibroblasts, conditioned-media (CM) were collected and applied to MDA-MB-231 human triple negative breast cancer cells. The levels of intracellular and extracellular HMGB1 were measured by real-time PCR and/or Western blot. The response of BCF-CM-pre-treated cancer cells to doxorubicin (Dox) was compared with those pre-treated with NTF-CM or control cultures. The effect of an HMGB1 neutralizing antibody on Dox resistance induced by extracellular HMGB1 from non-viable Dox-treated cancer cells or recombinant HMGB1 was also investigated.

Results

Immunocytochemical analysis revealed that BCFs and NTFs were alpha-smooth muscle actin (ASMA) positive and cytokeratin 19 (CK19) negative cells: a phenotype consistent with that of activated fibroblasts. We confirmed that the CM from BCFs (but not NTFs), could significantly induce breast cancer cell migration. Intracellular HMGB1 expression was induced in BCF-CM-treated breast cancer cells and also in Dox-treated cells. Extracellular HMGB1 was strongly expressed in the CM after Dox-induced MDA-MB-231 cell death and was higher in cells pre-treated with BCF-CM than NTF-CM. Pre-treatment of breast cancer cells with BCF-CM induced a degree of resistance to Dox in accordance with the increased level of secreted HMGB1. Recombinant HMGB1 was shown to increase Dox resistance and this was associated with evidence of autophagy. Anti-HMGB1 neutralizing antibody significantly reduced the effect of extracellular HMGB1 released from dying cancer cells or of recombinant HMGB1 on Dox resistance.

Conclusions

These findings highlight the potential of stromal fibroblasts to contribute to chemoresistance in breast cancer cells in part through fibroblast-induced HMGB1 production.

Growth inhibitory in vitro effects of glycyrrhizic acid in U251 glioblastoma cell line

Despite dramatic advances in cancer therapy, the overall prognosis of glioblastoma (GBM) remains dismal. Nuclear factor kappa-B (NF-κB) has been previously demonstrated to be constitutively activated in glioblastoma, and it was suggested as a potential therapeutic target. Glycyrrhizic acid (GA) has been proved to have cytotoxic effects in many cancer cell lines. However, its role in glioblastoma has not yet been addressed. Therefore, this study aimed to investigate the effects of GA on human glioblastoma U251 cell line. The effects of GA on proliferation of U251 cells were measured by CCK-8 assay and plate colony-forming test. Cellular apoptosis was detected by Hoechst 33258 fluorescent staining and flow cytometry with annexin V-FITC/PI dual staining. The expression of nuclear p65 protein, the active subunit of NF-κB, was determined by Western blot and immunofluorescence. Our results demonstrated that the survival rate and colony formation of U251 cells significantly decreased in a time- and dose-dependent manner after GA addition, and the apoptotic ratio of GA-treated groups was significantly higher than that of control groups. Furthermore, the expression of NF-κB-p65 in the nucleus was remarkably reduced after GA treatment. In conclusion, our findings suggest that GA treatment can confer inhibitory effects on human glioblastoma U251 cell line including inhibiting proliferation and inducing apoptosis, which is possibly related to the NF-κB mediated pathway.

HMGB1 in hormone-related cancer: a potential therapeutic target

High-mobility group box 1 (HMGB1) is a dynamic nuclear protein participating in transcription, chromatin remodelling, and DNA recombination and repair processes. Accumulating evidence indicates that its function now extends beyond the nucleus, notably its extracellular role in inflammation. HMGB1 is implicated as a late mediator of sepsis and is also believed to promote atherosclerosis and other inflammatory diseases such as rheumatoid arthritis and systemic lupus erythematosus. Interestingly, deregulation of HMGB1 is shown to be associated with the hallmarks of cancer development. Moreover, several clinical studies have shown that HMGB1 is a promising biomarker for a variety of cancer types. In this review, we provide novel insights into the role and mechanisms of HMGB1, in particular, to hormone-related cancers and its potential to serve as a therapeutic target.

Apoptotic response through a high mobility box 1 protein-dependent mechanism in LPS/GalN-induced mouse liver failure and glycyrrhizin-mediated inhibition

HMGB1 is a nuclear component involved in nucleosome stabilization and transcription regulation, but extracellularly it is able to serve as a potential late mediator of lethality. In the present study, we explored inflammation-promoting activity of HMGB1 and blockade of extracellular release of HMGB1 by glycyrrhizin (GL) in LPS/GalN-triggered mouse liver injury. At 1 to 10 h after LPS/GalN-treatment, mice were anesthetized to collect blood from heart puncture, and serum transaminase and HMGB1 were evaluated. Administration of LPS/GalN precipitated tissue injury associated with time-dependent alteration in HMGB1 serum levels. At 8 h nuclear immunoreactive products were remarkably reduced and extracellular HMGB1 expression was found exclusively in the pericentral foci. The treatment with GL significantly down-regulated the serum levels of ALT, AST, and HMGB1 in addition to the strong inhibition of tissue injury and extracellular immunoreactivity to HMGB1 and to acetylated-lysine. Furthermore, GL brought about a significant decrease in the number of apoptotic hepatocytes labeled with TUNEL-method. On the basis of these results, three apoptosis-associated genes were identified with microarray analysis and real-time PCR. The ChIP-assay revealed the binding of HMGB1 protein to Gsto1 promoter sequence in LPS/GalN-treated mice and the remarkable decrease in combined HMGB1 protein by GL. The current findings claim that a single injection of LPS/GalN might stimulate apoptosis of hepatocytes through the binding of HMGB1 protein to Gsto1 promoter region and that GL-treatment might prevent the apoptosis and inflammatory infiltrates caused with LPS/GalN-injection by disturbing the binding of HMGB1 protein to Gsto1 promoter sequence.

D-K6L 9 peptide combination with IL-12 inhibits the recurrence of tumors in mice

D-K6L9 peptide is bound by phosphatidylserine and induces necrosis in cancer cells. In our therapeutic experience, this peptide, when administered directly into B16-F10 murine melanoma tumors, inhibited their growth. Cessation of therapy results, however, in tumor relapse. We aimed at developing a combined therapy involving D-K6L9 and additional factors that would yield complete elimination of tumor cells in experimental animals. To this purpose, we employed glycyrrhizin, an inhibitor of HMGB1 protein, BP1 peptide and interleukin (IL)-12. Glycyrrhizin or BP1, when combined with D-K6L9, inhibits growth of primary tumors only during the period of their administration. A long-term tumor growth inhibitory effect was obtained only in combining D-K6L9 with IL-12. At 2 months following therapy cessation, 60 % of animals were alive. Prolonged survival was noted in mice bearing B16-F10 tumors as well as in mice bearing C26 colon carcinoma tumors.