INTRODUCTION
This editorial is a comment on the basic study of Huang et al[1], who concluded that Calculus bovis (CB) inhibits tumor-associated macrophages' M2-type polarization by blocking the Wnt/β-catenin pathway, which in turn inhibits liver cancer progression. Out of the 22 active ingredients in CB, Huang et al[1] found 11 active ingredients in the bloodstream, and CB had an inhibitory effect on tumor-associated macrophages. The Wnt agonist SKL2001 was shown to specifically target the M2-type polarization pathway. We aim to provide context for the above-mentioned basic study through deep insight into the molecular mechanism of hepatocellular carcinoma (HCC) with an emphasis on the Wnt/β-catenin pathway. Further, we explain the protective role of CB in HCC depending on inhibition of the Wnt/β-catenin pathway. Liver cancer, which is the fourth-most common cause of cancer-related deaths globally, continues to pose a threat to global health. HCC is the most prevalent type of primary liver cancer worldwide and represents a major global health-care challenge[2]. HCC is typically caused by long-term viral infections (hepatitis B and C), non-alcoholic steatohepatitis, excessive alcohol consumption, and other conditions that can cause the liver to become chronically inflamed and cirrhotic. In 2020, there were 830180 HCC-associated deaths globally[3-5]. To stop the rise in HCC mortality, improvements in early detection, increased HCC surveillance, and fair access to HCC treatments are required[6]. In China, digestive system cancers accounted for 41.6% of new cases and 49.3% of cancer-related mortality. Liver, as well as esophageal, nasopharyngeal, and stomach cancers in China, accounted for more than 40% of worldwide cases[7].
For a very long time, the well-known traditional remedy in China and Japan CB has been used extensively to treat a variety of diseases, such as high fever, convulsions, and stroke[8]. There has been an increasing focus on traditional Chinese medicine, specifically CB, as a possible liver protection remedy[9]. By blocking the interleukin-17/IL-17RA/Act1 signaling pathway, CB decreases the expression of pro-inflammatory cytokines and chemokines, reducing the inflammatory damage of colon tissues in ulcerative colitis mice and having the effect of dissipating heat and eliminating toxins[10]. Two important anti-inflammatory ingredients (taurochiolic acid and glycoholic acid) in CB are found to treat individuals with bacterial or viral infections who have a hyperactive immune response[11]. CB serves as a remedy to remove toxins and clear heat in ulcerative colitis (an inflammatory intestinal disease)[12].
The aim of the current editorial is to focus on the molecular mechanism of HCC and the protective role of CB in HCC through the inhibition of the Wnt/β-catenin pathway.
HCC MOLECULAR MECHANISM
Interleukin-10 serves as a regulator of liver metastases and is a pro-metastatic factor involved in liver metastasis formation[13]. Because it triggered the DNA repair response, histone methyltransferase was essential in accelerating liver cancer development[14]. Disturbances in lipid metabolism, cholesterol metabolism, bile acid metabolism, alcohol metabolism, and xenobiotic detoxification lead to fatty liver disease and liver cirrhosis[15]. Liver cancer has been linked to genes and pathways associated with ferroptosis[16]. Succinate, which is a tricarboxylic acid cycle intermediate, is vital to energy production and mitochondrial metabolism. It is also thought to be a signaling molecule in metabolism and in the development and spread of liver malignancies. As a result, succinate is crucial in the development of cancer and hepatic fibrosis[17]. Liver cancer growth is accelerated by the transcriptional and post-transcriptional inactivation of C/EBP homologous protein (CHOP), which is mediated by mitogen-activated protein kinase and mTOR activator 5 (LAMTOR5). Thus, LAMTOR5 stimulates the growth of liver cancer[18]. Liver cancer expression, development, and prognosis are all strongly correlated with the KIN17 protein. There is a significant increase in KIN17 concentration in the liver cancer group compared to the healthy group, (1.730 ng/mL vs 0.3897 ng/mL). Thus, serum KIN17 protein levels may serve as a biomarker for liver cancer[19]. 5-Methylcytosine, an mRNA alteration, is linked to the prognosis of HCC in the liver. It increases tumor growth in vivo and HCC cell proliferation, migration, invasion, and epithelial-mesenchymal transition in vitro[20]. MicroRNAs (miRNAs) are known to play an important role in the control of gene expression and have a major role in the prognosis and control of HCC. When combined with appropriate delivery vehicles, miRNA technology offers the capacity to interact directly with these elements, inhibiting the development and spread of liver tumors[21]. miRNAs have a therapeutic role in HCC. Both the safety of miRNAs and their anticancer effectiveness have been demonstrated in the treatment of HCC. Furthermore, because miRNAs have no side effects or only minor ones, they are very helpful in the therapy of HCC[22]. Through the PI3K/Akt signaling pathway, secondary CB ingredients like quercetin, kaempferol, and linarin control the antitumor actions against HCC. These ingredients control the production of proteins and the ability of HepG2 cells to proliferate, migrate, invade, and undergo apoptosis[23]. In patients with advanced liver cancer, molecular targeted therapy has shown good efficacy in raising the body's immune response, decreasing adverse reactions, and increasing the rate of cancer control[24].
MECHANISM OF THE Wnt/β-catenin PATHWAY IN HCC
The Wnt/β-catenin pathway is made up of a group of proteins that are essential for both adult tissue homeostasis and embryonic development. A number of severe diseases, including cancer, are frequently brought on by the inhibition of the Wnt/β-catenin signaling pathway. The down-regulation of the Wnt/β-catenin signaling pathway in liver cancer results in the suppression of the pathway, particularly when β-catenin is absent. This leads to steatosis and steatohepatitis through lipid accumulation, lipid peroxidation, liver injury, increased oxidative stress, and hepatocyte apoptosis[25]. The most common type of liver cancer in children, hepatoblastoma, is often linked to β-catenin mutations that trigger Wnt/β-catenin signaling. Wnt/β-catenin pathway activation in HCC also modifies immune cell behavior, leading to "immune evasion" and the development of resistance to immune checkpoint inhibitors. Wnt/β-catenin signaling is triggered by HCC in liver carcinogenesis by expressing downstream target genes[26]. A network of Wnt/β-catenin, NF-κB, and transforming growth factor beta controls human hepatocyte regeneration. This network also revealed novel regulators of hepatocyte proliferation[27]. A new circular RNA "Circ-CCT2" recruits and upregulates TATA-binding protein-associated factor 2N "TAF15 protein" to activate Wnt/β-catenin signaling, accelerating the evolution of hepatoblastoma[28]. Cavin1, a cell membrane caveolin, inhibits the activation of the Wnt/β-catenin axis to modulate HCC proliferation and migration, therefore suppressing the progression of HCC[29]. One of the main factors contributing to the development, progression, and treatment resistance of HCC is abnormal activation of the Wnt/β-Catenin signaling pathway. Therefore, understanding this pathway is essential to treating HCC[30]. In order to stop tumor cell progress in HCC, the therapeutic action relies on blocking the transport of β-catenin from the nucleus to the cytoplasm, which therefore activates the inactivation of the Wnt/β-catenin pathway[31]. Human cancer, especially liver cancer, is linked to the inhibition of the Wnt/β-catenin system. In liver cancer cells, the β-catenin/TCF complex inhibited the transcription of histidine ammonia lyase. In liver cancer cells, activated Wnt signaling raises the intracellular concentrations of arginine, histidine, and lactic acid. Wnt signaling also reduces the quantities of metabolites in the urea cycle and its gene-related enzymes, which in turn alter cellular metabolism in the liver through the Wnt/β-catenin pathway[32].
PROTECTION MECHANISM OF CB IN HCC
Eleven ingredients in CB, particularly oleanolic acid, ergosterol, and ursolic acid, have been shown to have anti-primary liver cancer properties. Furthermore, CB promotes the apoptosis of Cellosaurus cell line SMMC-7721[33]. In addition to preventing tumor invasion and angiogenesis, CB also inhibits cancer stem cell and tumor cell proliferation and controls the tumor microenvironment[34]. CB exhibits superior efficacy against a range of inflammatory conditions, as well as liver cancer[35]. In the rat model of cholestasis, CB reduced bile flow, which improved hepatobiliary disorders. Treatment with CB also relieved the tissue lesions. Western blot analyses revealed that, in comparison to the control group, cholestasis markedly increased P-glycoprotein (P-gp) protein and markedly decreased the protein expression of breast cancer resistance protein (Bcrp) and multidrug resistance-associated protein 2 (Mrp2). In a cholestasis rat model treated with CB, P-gp, Mrp2, and Bcrp, protein expression significantly increased. Bcrp was transcriptionally down-regulated in cholestasis. In contrast to the cholestasis group, CB increased the mRNA expression of P-gp, Mrp2, and Bcrp[36]. Rats with hepatic cholestasis showed markedly higher levels of mRNA and protein expression, as well as cumulative biliary excretions. Therefore, by reestablishing biliary transport function, CB had a beneficial effect on hepatic cholestasis rats[37]. By controlling oxidative stress, apoptosis, inflammation, and bile acid profiles, CB decreases the hepatic and intestinal damage caused by estrogen-induced cholestasis. As a result, CB acts as an effective treatment agent for cholestasis by targeting the gut-liver axis[38]. Treatment for liver cancer involves both steroid hormone production pathways and protein kinase regulator activities[39].
DESCRIPTION OF CB’S ROLE IN Wnt/β-catenin PATHWAY IN HCC
The Wnt/β-catenin pathway is an essential mediator of liver development and is highly conserved. In the majority of differentiated adult cells, it remains inactive. β-catenin's involvement in Wnt pathway activation determines whether it is considered canonical or non-canonical. When extracellular Wnt ligands are not present, the canonical Wnt pathway is inactivated. In this state, the β-catenin destruction complex controls the turnover of β-catenin. The human Wnt ligand family consists of 19 members that bind to the heterodimeric receptor complex made up of co-receptors, low-density lipoprotein receptor-related protein 5 or 6 (LPR5 or LPR6), and Frizzled (FZD)[40]. The Frizzled receptor increases with the co-receptor LPR when a Wnt ligand binds to it[41]. This causes LPR to become phosphorylated, which stops β-catenin from becoming phosphorylated and being broken down by proteases. As a result, β-catenin builds up in the cytoplasm and moves into the nucleus, where it interacts with various co-activators and/or transcription factors to control the expression of certain genes[42]. The Wnt-β-catenin pathway can be abnormally activated in a number of ways, such as AXIN1/2 mutations in 5%-10% of HCC cases[43] and β-catenin gene (CTNNB1) mutations in 30% of HCC cases[44]. Changes in this location lead to inappropriate activation of the Wnt pathway by preventing β-catenin from being phosphorylated and/or degraded. In 220 cases of hepatic adenomas and 373 cases of HCC, CTNNB1 mutations are present; however, HCC has an enrichment of high-activating CTNNB1 mutations (56% of HCC cases). In HCC, the Wnt/β-catenin pathway is essential for cell differentiation. In order to anticipate how HCC patients would respond to particular therapies, aberrant pathway activity has also been investigated as a biomarker[45].
However, through mechanisms connected to apoptosis and the functioning of the immune system, CB plays a significant role in the therapy of primary liver cancer[33]. By increasing ferroptosis in tumor cells and blocking the SLC7A11-GSH-GPX4 axis, CB significantly improves the hepatic fibrosis milieu and prevents the occurrence of HCC[46]. As a result, CB may be a possible agent for the protection and treatment of HCC at an early stage. Tumor necrosis factor receptor-1, tumor necrosis factor receptor-2, interleukin-6, and the G2/M check point (which stops tumor cells from proliferating and allows for DNA repair when cells are damaged) were all downregulated by CB to achieve this protective effect[47]. Furthermore, by controlling the levels of Bcl2/Bax, cyclin D1, cyclin dependent kinase 4, miR-483-5p, and cyclin dependent kinase inhibitor 1A, CB enhanced its protective role in liver cancer stem cells.
CONCLUSION
HCC is the most common type of primary liver cancer. HCC occurs in people with chronic liver diseases, such as cirrhosis caused by hepatitis B or hepatitis C infection. Cancer causes inhibition of the Wnt/β-catenin signaling pathway. This leads to steatosis and steatohepatitis through lipid accumulation, lipid peroxidation, liver injury, increased oxidative stress, and hepatocyte apoptosis. Oleanolic acid, ergosterol, and ursolic acid are CB ingredients that have anti-primary liver cancer properties. Therefore, CB is important in the treatment of primary liver cancer through Wnt/β-catenin signaling linked to immune system function and apoptosis. The recommendation of this editorial is as follows: (1) Studying the HCC molecular mechanism provides more details on the tumor microenvironment and helps to choose suitable treatments; (2) Hyperactivity of the Wnt/β-catenin signaling pathway occurs in HCC; and (3) Using CB as a protective agent against HCC, where its mechanism depends on the inhibition of the Wnt/β-catenin signaling pathway. The future direction of this editorial will be a clinical study of the therapeutic effect of CB on HCC patients to establish its treatment, and it will be interesting to see whether CB can treat HCC in real-life scenarios. The choice of CB in HCC treatment is preferable as a complementary and integrative medicine that is available, cheap, and without any side effects, like other cancer treatments such as chemotherapy.
Provenance and peer review: Invited article; Externally peer reviewed.
Peer-review model: Single blind
Specialty type: Gastroenterology and hepatology
Country of origin: Egypt
Peer-review report’s classification
Scientific Quality: Grade C
Novelty: Grade B
Creativity or Innovation: Grade C
Scientific Significance: Grade B
P-Reviewer: Li M S-Editor: Qu XL L-Editor: Filipodia P-Editor: Zheng XM
