Potential Anticancer Effect of Celastrol on Hepatocellular Carcinoma by Suppressing CXCR4-related Signal and Impeding Tumor Growth in Vivo

Celastrol induces ferroptosis by suppressing RRM2 in hepatocellular carcinoma

Introduction and Objectives

Ferroptosis is a novel form of cell death driven by iron dependence and lipid peroxidation, presenting a promising potential as an innovative strategy for cancer treatment. Celastrol (Cel) is particularly effective in inducing ferroptosis, but its molecular mechanism remains unclear. The study aims to elucidate the potential mechanism through both in vitro and in vivo experiments.

Materials and methods

CCK-8 assay, Western blot analysis and measurements of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH) were performed to investigate how Cel inhibits the proliferation of hepatocellular carcinoma (HCC) cells via the ferroptosis mechanism. Bioinformatics analysis based on the TCGA-LIHC and FerrDb databases was performed to identify the target gene RRM2, and molecular docking-simulated binding between RRM2 and Cel. The role of RRM2 in the effects of Cel was determined through lentiviral transfection, Transwell assays, and in vivo experiments.

Results

Cel inhibited HCC cell proliferation via the ferroptosis pathway. Inhibition RRM2 significantly reduces mTOR protein phosphorylation, while overexpressing RRM2 can attenuate theeffects of Cel on the proliferation, migration, invasion, and ferroptosis induction of HCC cells. The result of in vivo experiments in nude mice demonstrated that Cel inhibited tumor growth without adversely affecting liver and kidney function indicators. Immunohistochemistry and Western blot analyses revealed that Cel activated the key proteins in the ferroptosis pathway and affected crucial indicators such as malondialdehyde (MDA) and glutathione (GSH).

Conclusion

In this study, we clarifiy the molecular mechanism of Cel, thus broadening its clinical applications for treating various cancer types, including liver cancer.

The Promising Therapeutic Potential of Celastrol for Fibrotic Diseases: A Systematic Literature Review on Its Mechanism

Celastrol is a pentacyclic tripterine sourced from Tripterygium wilfordii hook root. Celastrol can exert certain biological functions such as antitumor, anti-inflammatory, and antiproliferative properties. Celastrol was shown from the previous literature to be capable of attenuating many fibrotic diseases. As the effects of various fibrotic diseases such as atherosclerosis, cancer, and ischemia affect more people with devastating repercussions, this warrants celastrol to be exploited as a phytotherapeutic drug. The purpose of this study is to review previous research and identify the proposed therapeutic mechanisms of celastrol in fibrotic diseases focusing on both the in vitro and in vivo experimental models.  A systematic literature search on Web of Science (WoS), Scopus, and ScienceDirect that included articles published between 2012 and 2022 was carried out using the keywords "celastrol", "tripterine", "fibrotic disease", and "fibrosis". After screening the initial search yield of 405 articles, 25 articles were included in this review.  The study findings summarize the potential therapeutic mechanism of celastrol in the attenuation of fibrotic diseases in in vivo and in vitro experimental models. It shows that celastrol is useful as a treatment means. However, more studies are needed on the effects of celastrol on humans to carry out clinical trials to verify the long-term benefits of celastrol.

CXC chemokine receptor 4 (CXCR4) blockade in cancer treatment

CXC chemokine receptor type 4 (CXCR4) is a member of the G protein-coupled receptors (GPCRs) superfamily and is specific for CXC chemokine ligand 12 (CXCL12, also known as SDF-1), which makes CXCL12/CXCR4 axis. CXCR4 interacts with its ligand, triggering downstream signaling pathways that influence cell proliferation chemotaxis, migration, and gene expression. The interaction also regulates physiological processes, including hematopoiesis, organogenesis, and tissue repair. Multiple evidence revealed that CXCL12/CXCR4 axis is implicated in several pathways involved in carcinogenesis and plays a key role in tumor growth, survival, angiogenesis, metastasis, and therapeutic resistance. Several CXCR4-targeting compounds have been discovered and used for preclinical and clinical cancer therapy, most of which have shown promising anti-tumor activity. In this review, we summarized the physiological signaling of the CXCL12/CXCR4 axis and described the role of this axis in tumor progression, and focused on the potential therapeutic options and strategies to block CXCR4.

Celastrol as an emerging anticancer agent: Current status, challenges and therapeutic strategies

Celastrol is a pentacyclic triterpenoid extracted from the traditional Chinese medicine Tripterygium wilfordii Hook F., which has multiple pharmacological activities. In particular, modern pharmacological studies have demonstrated that celastrol exhibits significant broad-spectrum anticancer activities in the treatment of a variety of cancers, including lung cancer, liver cancer, colorectal cancer, hematological malignancies, gastric cancer, prostate cancer, renal carcinoma, breast cancer, bone tumor, brain tumor, cervical cancer, and ovarian cancer. Therefore, by searching the databases of PubMed, Web of Science, ScienceDirect and CNKI, this review comprehensively summarizes the molecular mechanisms of the anticancer effects of celastrol. According to the data, the anticancer effects of celastrol can be mediated by inhibiting tumor cell proliferation, migration and invasion, inducing cell apoptosis, suppressing autophagy, hindering angiogenesis and inhibiting tumor metastasis. More importantly, PI3K/Akt/mTOR, Bcl-2/Bax-caspase 9/3, EGFR, ROS/JNK, NF-κB, STAT3, JNK/Nrf2/HO-1, VEGF, AR/miR-101, HSF1-LKB1-AMPKα-YAP, Wnt/β-catenin and CIP2A/c-MYC signaling pathways are considered as important molecular targets for the anticancer effects of celastrol. Subsequently, studies of its toxicity and pharmacokinetic properties showed that celastrol has some adverse effects, low oral bioavailability and a narrow therapeutic window. In addition, the current challenges of celastrol and the corresponding therapeutic strategies are also discussed, thus providing a theoretical basis for the development and application of celastrol in the clinic.

A comprehensive review on celastrol, triptolide and triptonide: Insights on their pharmacological activity, toxicity, combination therapy, new dosage form and novel drug delivery routes

Celastrol, triptolide and triptonide are the most significant active ingredients of Tripterygium wilfordii Hook F (TWHF). In 2007, the 'Cell' journal ranked celastrol, triptolide, artemisinin, capsaicin and curcumin as the five natural drugs that can be developed into modern medicinal compounds. In this review, we collected relevant data from the Web of Science, PubMed and China Knowledge Resource Integrated databases. Some information was also acquired from government reports and conference papers. Celastrol, triptolide and triptonide have potent pharmacological activity and evident anti-cancer, anti-tumor, anti-obesity and anti-diabetes effects. Because these compounds have demonstrated unique therapeutic potential for acute and chronic inflammation, brain injury, vascular diseases, immune diseases, renal system diseases, bone diseases and cardiac diseases, they can be used as effective drugs in clinical practice in the future. However, celastrol, triptolide and triptonide have certain toxic effects on the liver, kidney, cholangiocyte heart, ear and reproductive system. These shortcomings limit their clinical application. Suitable combination therapy, new dosage forms and new routes of administration can effectively reduce toxicity and increase the effect. In recent years, the development of different targeted drug delivery formulations and administration routes of celastrol and triptolide to overcome their toxic effects and maximise their efficacy has become a major focus of research. However, in-depth investigation is required to elucidate the mechanisms of action of celastrol, triptolide and triptonide, and more clinical trials are required to assess the safety and clinical value of these compounds.

Celastrol: An Update on Its Hepatoprotective Properties and the Linked Molecular Mechanisms

The liver plays an important role in glucose and lipid homeostasis, drug metabolism, and bile synthesis. Metabolic disorder and inflammation synergistically contribute to the pathogenesis of numerous liver diseases, such as metabolic-associated fatty liver disease (MAFLD), liver injury, and liver cancer. Celastrol, a triterpene derived from Tripterygium wilfordii Hook.f., has been extensively studied in metabolic and inflammatory diseases during the last several decades. Here we comprehensively review the pharmacological activities and the underlying mechanisms of celastrol in the prevention and treatment of liver diseases including MAFLD, liver injury, and liver cancer. In addition, we also discuss the importance of novel methodologies and perspectives for the drug development of celastrol. Although celastrol has been claimed as a promising agent against several metabolic diseases, both preclinical and clinical studies are highly required to accelerate the clinical transformation of celastrol in treating different liver illness. It is foreseeable that celastrol-derived therapeutics is evolving in the field of liver ailments.

Current Perspective of Traditional Chinese Medicines and Active Ingredients in the Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading lethal tumors worldwide, and the treatment remains a great medical challenge. Surgery and chemotherapy are current standard curative methods for patients with HCC, but the prognosis is still dismal. Based on unique medical theories and rich practical experience, traditional Chinese medicine (TCM) has been broadly employed to effectively treat HCC for a long history. Recently, systematic clinical trials have been well designed to study the efficacy of TCMs in the treatment of HCC, and the underlying antitumor mechanisms were also deeply explored. Here, we reviewed the published clinical evaluation of some commonly used TCMs in the treatment of HCC, and the related anti-HCC mechanisms through in vitro and in vivo study, promoting the modernization of TCM study in oncology for achieving a substantial reduction of HCC burden in the future.

CXCR4 promotes gefitinib resistance of Huh7 cells by activating the c-Met signaling pathway

C-X-C chemokine receptor type 4 (CXCR4) expression is associated with poor prognosis of hepatocellular carcinoma (HCC). The aim of this study was to explore the biological role of CXCR4 in gefitinib resistance of HCC. Compared with a normal, non-gefitinib-resistant, human HCC cell line (Huh7), CXCR4 mRNA and protein were highly expressed in gefitinib-resistant Huh7 cells (Huh7-R). Cell proliferation was decreased, and apoptosis was enhanced in Huh7 cells in the presence of gefitinib. These influences conferred by gefitinib treatment on proliferation and apoptosis of Huh7 cells were abolished by CXCR4 overexpression. CXCR4 knockdown reduced the proliferation ability of HuH-7R cells after gefitinib treatment. Importantly, CXCR4 overexpression had no influence on caveolin 1 (Cav-1) expression; similarly, Cav-1 silencing did not cause a substantive change in CXCR4 expression. However, CXCR4 activated Cav-1, c-Met, and Raf-1 in Huh7 cells, whereas Cav-1 silencing repressed the expression of Raf-1 and phosphorylated c-Met in Huh7 cells. CXCR4 overexpression promoted proliferation and repressed apoptosis in gefitinib-treated Huh7 cells, which was partly rescued by PHA-665752 (a c-Met inhibitor) treatment or c-Met deficiency. Finally, we constructed a tumor xenograft model to determine the influence of CXCR4 overexpression on tumor growth of HCC. CXCR4 overexpression accelerated tumor growth of HCC, which was abrogated by c-Met deficiency. These findings demonstrate that CXCR4 overexpression activates c-Met via the Cav-1 signaling pathway, thereby promoting gefitinib resistance of Huh7 cells. Thus, this study highlights novel insights into the mechanism of gefitinib resistance of HCC and CXCR4 may become a potential target for HCC treatment.

Improved delivery system for celastrol-loaded magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods: HIF-1α-related apoptotic effects on SMMC-7721 cell

Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods were prepared by a rapid combustion method with α-FeOOH nanorods as precursors. Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods with a saturation magnetization of 33.2 emu·g^-1 were obtained using 30 mL of absolute ethanol at a calcination temperature of 300 °C. Their average length was around 140 nm, and average diameter was about 20 nm. To improve the dispersion characteristics of the Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods in aqueous solution, citric acid and PEG were applied to modify the nanorod surface via the Mitsunobu reaction. The results showed that the hydrodynamic size range of Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol was 250-500 nm, the surface potential was -15 mV, and the saturation magnetization was approximately 23 emu·g^-1. The drug loading capacity of Fe₃O₄/α-Fe₂O₃/CA-PEG was larger than the non-PEG modified version. Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol had slow-release characteristics and was sensitive to changes in pH. Application of a magnetic field significantly promoted the inhibition of SMMC-7721 human liver cancer cell growth after treatment with Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol. Celastrol and Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol increased the production of reactive oxygen species in SMMC-7721 cells and promoted apoptosis and apoptosis-related proteins (p53, Bax, Bcl-2) were also changed. In addition, the expression of hypoxia-inducible factor 1α (HIF-1α) was enhanced. We may conclude that celastrol-loaded magnetic Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods may be applied in the chemotherapy of human cancer with good biocompatibility and delivery.

Anti-Tumor Effect of Celastrol on Hepatocellular Carcinoma by the circ_SLIT3/miR-223-3p/CXCR4 Axis

Background

Celastrol is a potential anti-tumor agent in hepatocellular carcinoma (HCC). Identifying the molecular determinants of the anti-HCC effect of celastrol is still challenging. In this study, we undertook to associate circular RNAs (circRNAs) with the anti-HCC molecular determinants of celastrol.

Methods

Cell colony formation, proliferation, migration, invasion and apoptosis were determined using the colony formation, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide (MTS), transwell and flow cytometry assays, respectively. The levels of circRNA slit guidance ligand 3 (circ_SLIT3), miR-223-3p and C-X-C motif chemokine receptor 4 (CXCR4) were gauged by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Ribonuclease R (RNase R) and actinomycin D assays were performed to assess the stability of circ_SLIT3. Targeted relationships among circ_SLIT3, miR-223-3p and CXCR4 were confirmed by the dual-luciferase reporter assay. In vivo assays were performed to detect the roles of celastrol and circ_SLIT3 on tumor growth in vivo.

Results

Celastrol repressed HCC cell proliferation, migration, invasion, and enhanced apoptosis in vitro and suppressed tumor growth in vivo. Celastrol down-regulated circ_SLIT3 expression in HCC cells, and celastrol exerted an anti-tumor effect on HCC in vitro and in vivo by down-regulating circ_SLIT3. Mechanistically, circ_SLIT3 directly interacted with miR-223-3p, and circ_SLIT3 controlled CXCR4 expression by sponging miR-223-3p. Moreover, miR-223-3p was involved in the celastrol/circ_SLIT3-mediated regulation on HCC progression. Furthermore, celastrol exerted the anti-HCC effect in vitro through the miR-223-3p/CXCR4 axis.

Conclusion

Our present work first identified the circ_SLIT3/miR-223-3p/CXCR4 axis as a novel mechanism of the anti-HCC effect of celastrol, providing a new insight into the involvement of circRNAs in the anti-tumor molecular determinants of celastrol.