Caudatin inhibits human hepatoma cell growth and metastasis through modulation of the Wnt/β-catenin pathway

Natural compounds targeting YAP/TAZ axis in cancer: Current state of art and challenges

Cancer has become a burgeoning global healthcare concern marked by its exponential growth and significant economic ramifications. Though advancements in the treatment modalities have increased the overall survival and quality of life, there are no definite treatments for the advanced stages of this malady. Hence, understanding the diseases etiologies and the underlying molecular complexities, will usher in the development of innovative therapeutics. Recently, YAP/TAZ transcriptional regulation has been of immense interest due to their role in development, tissue homeostasis and oncogenic transformations. YAP/TAZ axis functions as coactivators within the Hippo signaling cascade, exerting pivotal influence on processes such as proliferation, regeneration, development, and tissue renewal. In cancer, YAP is overexpressed in multiple tumor types and is associated with cancer stem cell attributes, chemoresistance, and metastasis. Activation of YAP/TAZ mirrors the cellular "social" behavior, encompassing factors such as cell adhesion and the mechanical signals transmitted to the cell from tissue structure and the surrounding extracellular matrix. Therefore, it presents a significant vulnerability in the clogs of tumors that could provide a wide window of therapeutic effectiveness. Natural compounds have been utilized extensively as successful interventions in the management of diverse chronic illnesses, including cancer. Owing to their capacity to influence multiple genes and pathways, natural compounds exhibit significant potential either as adjuvant therapy or in combination with conventional treatment options. In this review, we delineate the signaling nexus of YAP/TAZ axis, and present natural compounds as an alternate strategy to target cancer.

Five New C21 -Steroidal Sapogenins from the Acid Hydrolysate of Cynanchum otophyllum Roots

Five new C₂₁ -steroidal sapogenins (1-5) named cynotogenins J-N, were isolated from the acid hydrolysate of Cynanchum otophyllum roots. Their structures were established by extensive spectroscopic analysis (UV, IR, HR-ESI-MS, and NMR). Most notably, compounds 1-3 harboring a rare 5β,6β-epoxy group in the C₂₁ -steroidal skeleton of Cynanchum plants. All compounds were evaluated for their cytotoxicities against multiple cancer cell lines, in which compounds 5 showed weak cytotoxicity against HepG2 cancer cells with IC₅₀ values of 44.90 μM.

Caudatin Inhibits the Proliferation, Invasion, and Glycolysis of Osteosarcoma Cells via the Wnt/β- Catenin Pathway

Background

Caudatin is a steroidal glycoside with reported anticancer activity in a variety of studies. Nevertheless, the role and mechanisms of caudatin in osteosarcoma (OS) remain unclear. In this study, we explored the potential anticancer effects of caudatin in OS cells and investigated the underlying mechanisms.

Methods

Both the CCK8 proliferation assay and flow cytometry were employed to evaluate cell proliferation and apoptosis. A transwell assay was applied to determine cell invasion ability. Besides, glycolytic capacity was examined by measuring glucose consumption, lactic acid production, as well as ATP production. A western blot was utilized to assess the protein levels of β-catenin, CyclinD 1, C-myc, HK2 (Hexokinase 2), LDHA (lactate dehydrogenase), as well as epithelial-mesenchymal transition (EMT)-related markers. The inhibitory effect of caudatin on tumor growth was investigated using a xenograft tumorigenesis model.

Results

Caudatin restrained cellular glycolysis, suppressed cell proliferation and invasion by reducing HK2 and LDHA expression and regulating the Wnt/β-Catenin signaling pathway. Caudatin treatment caused the upregulation of E-cadherin and suppressed N-cadherin expression. Further, caudatin treatment impaired cell viability, invasion ability, and intracellular glycolysis level but induced apoptosis. The administration of BML 284 reversed the inhibitory effects of caudatin. Moreover, caudatin suppressed the tumorigenesis of OS cells in the xenograft model of nude mice.

Conclusions

Our study revealed the anticancer effects of caudatin, including proliferation inhibition, cell invasion suppression, and glycolysis impairment. These effects seem to be executed through targeting the Wnt/β-Catenin signaling pathway. These data indicate that caudatin may be formulated as a potential therapeutic for osteosarcoma.

Caudatin blocks the proliferation, stemness and glycolysis of non-small cell lung cancer cells through the Raf/MEK/ERK pathway

CONTEXT

The antitumor effects of caudatin have been explored in multiple cancers, but the research on lung cancer has not been fully understood.

OBJECTIVE

We explored the effects of caudatin on non-small cell lung cancer (NSCLC) in vitro and in vivo.

MATERIALS AND METHODS

In the in vitro experiments, 0, 25, 50 and 100 μM of caudatin were selected to examine the effects on stemness and glycolysis. Subcutaneous tumour xenografts were constructed by injecting the nude mice (BALB/C) with 5 × 10⁶ H1299 cells. In the in vivo experiments, all nude mice were divided into the caudatin group (50 mg/kg/day, n = 5) and the sham group (equal amount of DMSO, n = 5).

RESULTS

The IC₅₀ of caudatin for H1299 and H520 cells was 44.68 μM and 69.37 μM, respectively. Compared with caudatin 0 μM group, cell apoptosis rate was increased about 10 times and cell stemness was decreased by 75-85% in caudatin 100 μM group. Glucose uptake (65-80% reduction), lactic acid production (75-80% reduction), ATP level (70-80% reduction) and the expression of HK2 and LDHA (75-85% reduction) were decreased in caudatin 100 μM group. The expression of Raf/MEK/ERK pathway related proteins was decreased to 20-25% by caudatin. Tumour weight (about 70% reduction) and the expression of stemness, glycolysis and Raf/MEK/ERK pathway related proteins (about 50-75% reduction) were suppressed by caudatin in vivo.

DISCUSSION AND CONCLUSIONS

We revealed that caudatin blocked stemness and glycolysis in NSCLC for the first time. More experiments about exact dosage of caudatin in vivo should be conducted.

The antitumour activity of C21 steroidal glycosides and their derivatives of Baishouwu: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Baishouwu has been used in China for thousands of years since it was first discovered in the late Tang Dynasty and flourished in the Song and Ming Dynasties. The Chinese herbal medicines named Baishouwu include Cynanchum auriculatum Royle ex Wight., Cynanchum bungei Decne. and Cynanchum wilfordii Hemsl. It is described in the Sign of Materia Medica as "sweet, bitter, reinforce liver and kidney, and non-toxic". It is widely used for nourishing the blood to expel wind, reinforcing liver and kidney, strengthening bones and muscles.

AIM OF THE REVIEW

In this review, the current research status of the C₂₁ steroidal glycosides and their derivatives of Baishouwu for malignant tumours and their anti-tumour mechanisms are discussed. This may lay the ground for potential application of Baishouwu and its active ingredients in the treatment of tumours.

MATERIALS AND METHODS

Scientific databases, including PubMed, Elsevier, Science Direct, Google Scholar, CNKI, WANFANG DATA and VIP were searched to gather data about Baishouwu and its C₂₁ steroidal glycosides and their derivatives.

RESULTS

Prior literature indicates that Baishouwu has important biological activities such as anti-tumour, anti-epileptic, reducing cholesterol, protection of liver and kidney and immunomodulatory, which are of increasing interest, especially its anti-tumour activity. Recent studies demonstrate that the C₂₁ steroidal glycosides of Baishouwu, which have prominent antitumour efficacy, are one of its main active ingredients. Presently, a variety of C₂₁ steroidal glycosides have been isolated from Baishouwu medicinal part, the tuberous root. This review summarizes the various antitumour activities of the C₂₁ steroidal glycosides and their derivatives of Baishouwu.

CONCLUSIONS

In this review, the antitumour effects and mechanisms of total C₂₁ steroidal glycosides and monomers and derivatives of Baishouwu in vitro and in vivo were summarized. Baishouwu can inhibit tumourigenesis by blocking tumour cell cycle progression, regulating numerous signaling pathways, promoting apoptosis, inhibiting tumour cells proliferation and metastasis, improving immunity and so on. This review provides a theoretical basis for inheriting and developing the medical heritage of the motherland, exploring the resources of traditional Chinese medicine for ethnic minorities and clinical rational drug use.

Hsa_circ_0060927 participates in the regulation of Caudatin on colorectal cancer malignant progression by sponging miR-421/miR-195-5p

BACKGROUND

Caudatin is extracted from radix cynanchi bungei and has an inhibitory effect on cancer progression. The study aims to reveal the impacts of hsa_circ_0060927 on Caudatin-mediated colorectal cancer (CRC) development and the underneath mechanism.

METHODS

The expression levels of hsa_circ_0060927, microRNA-421 (miR-421) and miR-195-5p were detected by quantitative real-time reverse transcription-polymerase chain reaction. The protein expression was analyzed by Western blot or immunohistochemistry assay. Cell viability and proliferation were analyzed by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide or 5-Ethynyl-29-deoxyuridine assay. Cell apoptosis was quantified by flow cytometry analysis. Cell migration and invasion were investigated by transwell assay. The putative associations among hsa_circ_0060927, miR-421 and miR-195-5p were predicted by the starbase online database, and identified by dual-luciferase reporter, RNA pull-down and RNA immunoprecipitation (RIP) assays. The impacts of Caudatin treatment on tumor growth in vivo were revealed by a xenograft tumor model assay.

RESULTS

Hsa_circ_0060927 expression was significantly upregulated, whereas miR-421 and miR-195-5p were downregulated in CRC tissues and cells compared with control groups. Hsa_circ_0060927 expression was closely associated with lymph node metastasis and tumor-node-metastasis stage. Caudatin treatment significantly decreased hsa_circ_0060927 expression but increased miR-421 and miR-195-5p expression. Caudatin exposure suppressed CRC cell proliferation, migration and invasion, and induced cell apoptosis; however, hsa_circ_0060927 overexpression hindered these impacts. Additionally, hsa_circ_0060927 was associated with miR-421/miR-195-5p. Depletion of miR-421 or miR-195-5p attenuated the influences of hsa_circ_0060927 silencing on CRC development. Furthermore, Caudatin treatment repressed tumor growth in vivo.

CONCLUSION

Caudatin inhibited CRC cell malignancy through the hsa_circ_0060927/miR-421/miR-195-5p pathway, which provided a potential therapeutic agent for CRC.

Synthesis and biological evaluation of 3β-O-neoglycosides of caudatin and its analogues as potential anticancer agents

In order to study the structure-activity relationship (SAR) of C₂₁-steroidal glycosides toward human cancer cell lines and explore more potential anticancer agents, a series of 3β-O-neoglycosides of caudatin and its analogues were synthesized. The results revealed that most of peracetylated 3β-O-monoglycosides demonstrated moderate to significant antiproliferative activities against four human cancer cell lines (MCF-7, HCT-116, HeLa, and HepG2). Among them, 3β-O-(2,3,4-tri-O-acetyl-β-L-glucopyranosyl)-caudatin (2k) exhibited the highest antiproliferative activity aganist HepG2 cells with an IC₅₀ value of 3.11 μM. Mechanical studies showed that compound 2k induced both apoptosis and cell cycle arrest at S phase in a dose dependent manner. Overall, these present findings suggested that glycosylation is a promising scaffold to improve anticancer activity for naturally occurring C₂₁-steroidal aglycones, and compound 2k represents a potential anticancer agent deserved further investigation.

Cynanchum auriculatum Royle ex Wight., Cynanchum bungei Decne. and Cynanchum wilfordii (Maxim.) Hemsl.: Current Research and Prospects

Cynanchum auriculatum Royle ex Wight. (CA), Cynanchum bungei Decne. (CB) and Cynanchum wilfordii (Maxim.) Hemsl. (CW) are three close species belonging to the Asclepiadaceous family, and their dry roots as the bioactive part have been revealed to exhibit anti-tumor, neuroprotection, organ protection, reducing liver lipid and blood lipid, immunomodulatory, anti-inflammatory, and other activities. Until 2021, phytochemistry investigations have uncovered 232 compounds isolated from three species, which could be classified into C21-steroids, acetophenones, terpenoids, and alkaloids. In this review, the morphology characteristics, species identification, and the relationship of botany, extraction, and the separation of chemical constituents, along with the molecular mechanism and pharmacokinetics of bioactive constituents of three species, are summarized for the first time, and their phytochemistry, pharmacology, and clinical safety are also updated. Moreover, the direction and limitation of current research on three species is also discussed.

Anticancer properties of caudatin and related C-21 steroidal glycosides from Cynanchum plants

Numerous C-21 steroidal glycosides have been isolated from Cynanchum plants. Many of them derive from the aglycone caudatin (CDT) which includes a tetracyclic deacylmetaplexigenin unit and an ikemaoyl ester side chain. CDT can be found in diverse traditional medicines, such as Baishouwu radix used to treat gastro-intestinal disorders. The compound has revealed marked anticancer properties, reviewed here. CDT and its mono-glycoside analogue CDMC display antiproliferative activities against different cancer cell lines in vitro and have revealed significant anticancer effects in tumor xenograft models in vivo. Their mechanism of action is multifactorial, implicating several signaling pathways (Wnt/GSK3/β-catenin, TRAIL/DR5/ER and TNFAIP1/NFκB) which contribute to the antiproliferative, antiangiogenic, antimetastatic and proapoptotic effects of the natural products. CDT also modulates DNA replication, is antioxidant and targets some cancer stem cells. CDT and CDMC are interesting anticancer products, while other CDT glycoside derivatives display antiviral and antifungal activities. Altogether, the present review provides a survey of the pharmacological profiles of CDT and derivatives. The lack of knowledge about the molecular targets of CDT currently limits drug development but the natural product, orally active, warrants further pharmacology and toxicology studies.

New C21-steroidal aglycones from the roots of Cynanchum otophyllum and their anticancer activity

Naturally occurring C₂₁-steroidal aglycones from Cynanchum exhibit significant antitumor effects. To expand the chemical diversity and get large scale C₂₁-steroidal aglycones, the extracts of the roots of Cynanchum otophyllum were treated with 5% HCl in aqueous and the resulting hydrolysate was investigated. Nine new C₂₁-steroidal aglycones (1-9) namely cynotogenins A-I, along with seventeen known analogous (10-26), were isolated from the hydrolysate. The structures of compounds 1-9 were elucidated by spectroscopic analysis (IR, HR-ESI-MS, 1D and 2D NMR) and comparison of observed spectroscopic data with those of reported in the literature. Aglycones 2-5 with rare cis-cinnamoyl group as well as 8 and 9 with 5β,6β-epoxy group were found from the genus of Cynanchum for the first time. The cytotoxicities of compounds 1-26 toward human cancer HeLa, H1299, HepG2, and MCF-7 cells were evaluated and preliminary structure-activity relationship (SAR) was discussed. Moreover, compound 20 inhibits HepG2 cell apoptosis and induces of G0/G1 phase arrest in a dose dependent manner.

Caudatin Isolated from Cynanchum auriculatum Inhibits Breast Cancer Stem Cell Formation via a GR/YAP Signaling

In the complex tumor microenvironment, cancer stem cells (CSCs), a rare population of cells, are responsible for malignant tumor initiation, metastasis, drug resistance and recurrence. Controlling breast CSCs (BCSCs) using natural compounds is a novel potential therapeutic strategy for clinical cancer treatment. In this study, a mammosphere assay-guided isolation protocol including silica gel, a C18 column, gel filtration, and high-pressure liquid chromatography was used to isolate an inhibitory compound from Cynanchum auriculatum extracts. The isolated inhibitory compound was identified as caudatin. Caudatin inhibited breast cancer cell proliferation, mammosphere formation and tumor growth. Caudatin decreased the CD44⁺/CD24⁻ and aldehyde dehydrogenase⁺ cell proportions and the levels of c-Myc, Oct4, Sox2, and CD44. Caudatin induced ubiquitin (Ub)-dependent glucocorticoid receptor (GR) degradation and blocked subsequent Yes-associated protein (YAP) nuclear accumulation and target gene transcription signals in BCSCs. These results show that the GR/YAP signaling pathway regulates BCSC formation and that caudatin may be a potential chemopreventive agent that targets breast cancer cells and CSCs.

Anticancer effect of caudatin in diethylnitrosamine‑induced hepatocarcinogenesis in rats

An overwhelming endoplasmic reticulum stress (ERS) and the following unfolded protein response (UPR) can induce hepatic inflammation, fibrosis and hepatocellular carcinoma (HCC). Caudatin, one of the species of C-21 steroidal glycosides mainly isolated from the roots of Cynanchum bungei Decne, exhibits potent anticancer activities in vivo. However, the effect of caudatin on HCC remains unclear. In the present study, a diethylnitrosamine (DEN)-induced HCC model was established. Nodules and tumors in rat livers were monitored by T2-/T1-weighted-magnetic resonance imaging (MRI) using a 1.5 T scanner. Caudatin reduced the number and size of nodules and alleviated the inflammatory foci in the liver. In addition, the hepatic pro-inflammatory levels of interleukin (IL) 6, monocyte chemoattractant protein 1 and IL-1β were decreased in caudatin-treated rats. The DEN-induced surge in malondialdehyde, aspartate aminotransferase, alanine transaminase and TBIL were alleviated following caudatin treatment. The expression of ERS chaperones glucose-regulated protein, 94 kDa, glucose-regulated protein, 78 kDa and protein disulfide-isomerase A4 and the proliferation marker Ki-67 in liver nodules were all downregulated by caudatin as demonstrated by immunohistochemistry, reverse transcription-quantitative PCR and western blot analysis. Caudatin reduced the cytoprotective ERS sensor activating transcription factor 6-mediated signal transduction and inhibited the PKR-like endoplasmic reticulum kinase/eukaryotic initiation factor 2α/activating transcription factor 4 pathway. However, the effect of caudatin on inositol requiring enzyme 1 signaling was negligible. In conclusion, restoration of the dysregulated UPR program was involved in the antitumor efficacy of caudatin without inducing cumulative hepatotoxicity.

Cleistanthin A inhibits the invasion of MDA-MB-231 human breast cancer cells: involvement of the β-catenin pathway

BACKGROUND

Cleistanthin A (CleA), a natural diphyllin glycoside, has been shown to suppress the invasion of cancer cells, but the underlying mechanisms remain unclear. Here, the inhibitory effect of CleA on the invasion of MDA-MB-231 human breast cancer cells was investigated, and the mechanisms involved were clarified.

METHODS

Cell viability was studied by MTT assay. The migration and invasion of MDA-MB-231 cells were assessed by wound healing assay and transwell assay, respectively. The enzymatic activity of matrix metalloproteinases (MMPs) was detected by gelatin zymography. mRNA and protein levels were detected by qRT-PCR and Western blotting, respectively. Nuclear translocation of β-catenin was observed by immunofluorescence and detected by Western blotting.

RESULTS

CleA effectively inhibited the migration and invasion of MDA-MB-231 cells and suppressed the expression and activation of MMP-2/9. Moreover, the expression and nuclear translocation of β-catenin were reduced by CleA treatment, as well as transcription of the Cyclin D1 and c-myc genes. In addition, the inhibitory effect of CleA on the β-catenin pathway was attributed to the promotion of β-catenin degradation by inhibition of GSK3β phosphorylation. When the phosphorylation of GSK3β was induced by LiCl, the inhibitory effect of CleA on the β-catenin pathway and the invasion of MDA-MB-231 cells were almost reversed.

CONCLUSION

CleA suppressed the invasion of MDA-MB-231 cells, likely through the β-catenin pathway.

Antiangiogenic properties of caudatin in vitro and in vivo by suppression of VEGF‑VEGFR2‑AKT/FAK signal axis

Tumor angiogenesis provides essential nutrients and oxygen to the tumor microenvironment, which is important in tumor growth, progression and metastasis. Inhibition of tumor angiogenesis represents one of the most promising strategies in tumor therapy. The authors previously demonstrated that caudatin, one species of C‑21 steroidal from Cynanchum auriculatum (C. auriculatum), effectively inhibits human glioma growth in vitro and in vivo through triggering cell cycle arrest and apoptosis. However, little information regarding the antiangiogenic properties of caudatin in human glioma is available. Based on the author's previous study, the antiangiogenic effect of caudatin against human glioma was explored, and the underlying mechanism was investigated. The results suggested that caudatin treatment significantly inhibited HUVEC human umbilical vein endothelial cell proliferation, blocked the HUVECs migration, invasion and capillary‑like tube formation by disturbing the vascular endothelial growth factor (VEGF)‑VEGFR2‑protein kinase B (AKT)/focal adhesion kinase (FAK) signal axis. Notably, caudatin treatment abolished the glioma cell growth by suppression of the in vivo angiogenesis, which involved FAK and AKT dephosphorylation and inhibition of VEGF expression. The findings validated the antiangiogenic potential of caudatin in hunting human glioma.

Expression and purification of the recombinant porcine NK-lysin in Pichia pastoris and observation of anticancer activity in vitro

Natural killer (NK)-lysin, a broad-spectrum antimicrobial peptide, has antitumor and antibactericidal activities against both gram-positive and gram-negative bacteria. In this study the recombinant porcine NK-lysin was expressed and purified in the Pichia pastoris system, and then 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to assess its anticancer activity in vitro. The results showed that the recombinant porcine NK-lysin possesses potent antitumor activity against the human hepatocellular carcinoma cell line SMMC-7721 in a time- and dose-dependent manner, but has negligible hemolysis activity against human erythrocytes. Scanning electronic microscopy was used to directly observe the ultrastructure of SMMC-7721 cells treated with NK-lysin; untreated cells showed lamellipodia and filopodia scattered with the cell surface, with good cell-cell contacts among neighboring cells. In contrast, treated tumor cells exhibited marked alterations in cell morphology, and cell-cell contacts disappeared among neighboring cells. Compared with the untreated tumor cells, the tumor cells treated with NK-lysin for 12 and 24 hr were suppressed for the expression of fascin 1. Thus, the recombinant porcine NK-lysin potentially could be developed as a therapeutic agent for inhibiting tumor growth.

Shikonin Inhibits the Migration and Invasion of Human Glioblastoma Cells by Targeting Phosphorylated β-Catenin and Phosphorylated PI3K/Akt: A Potential Mechanism for the Anti-Glioma Efficacy of a Traditional Chinese Herbal Medicine

Shikonin is an anthraquinone derivative extracted from the root of lithospermum. Shikonin is traditionally used in the treatment of inflammatory and infectious diseases such as hepatitis. Shikonin also inhibits proliferation and induces apoptosis in various tumors. However, the effect of shikonin on gliomas has not been fully elucidated. In the present study, we aimed to investigate the effects of shikonin on the migration and invasion of human glioblastoma cells as well as the underlying mechanisms. U87 and U251 human glioblastoma cells were treated with shikonin at 2.5, 5, and 7.5 μmol/L and cell viability, migration and invasiveness were assessed with CCK8, scratch wound healing, in vitro Transwell migration, and invasion assays. The expression and activity of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) and the expression of phosphorylated β-catenin (p-β-catenin) and phosphorylated PI3K/Akt were also checked. Results showed that shikonin significantly inhibited the cell proliferation, migration, invasion, and expression of MMP-2 and MMP-9 in U87 and U251 cells. The expression of p-β-catenin showed contrary trends in two cell lines. It was significantly inhibited in U87 cells and promoted in U251 cells. Results in this work indicated that shikonin displayed an inhibitory effect on the migration and invasion of glioma cells by inhibiting the expression and activity of MMP-2 and -9. In addition, shikonin also inhibited the expression of p-PI3K and p-Akt to attenuate cell migration and invasion and MMP-2 and MMP-9 expression in both cell lines, which could be reversed by the PI3K/Akt pathway agonist, insulin-like growth factor-1 (IGF-1).

CLDN3 inhibits cancer aggressiveness via Wnt-EMT signaling and is a potential prognostic biomarker for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common fatal malignancies but the molecular genetic basis of this disease remains unclear. By using genome-wide methylation profiling analysis, we identified CLDN3 as an epigenetically regulated gene in cancer. Here, we investigated its function and clinical relevance in human HCC. CLDN3 downregulation occurred in 87/114 (76.3%) of primary HCCs, where it was correlated significantly with shorter survival of HCC patients (P=0.021). Moreover, multivariate cyclooxygenase regression analysis showed that CLDN3 was an independent prognostic factor for overall survival (P=0.014). Absent expression of CLDN3 was also detected in 67% of HCC cell lines, which was significantly associated with its promoter hypermethylation. Ectopic expression of CLDN3 in HCC cells could inhibit cell motility, cell invasiveness, and tumor formation in nude mice. Mechanistic investigations suggested through downregulation of GSK3B, CTNNB1, SNAI2, and CDH2, CLDN3 could significantly suppress metastasis by inactivating the Wnt/β-catenin-epithelial mesenchymal transition (EMT) axis in HCC cells. Collectively, our findings demonstrated that CLDN3 is an epigenetically silenced metastasis suppressor gene in HCC. A better understanding of the molecular mechanism of CLDN3 in inhibiting liver cancer cell metastasis may lead to a more effective management of HCC patients with the inactivation of CLDN3.

CLDN3 inhibits cancer aggressiveness via Wnt-EMT signaling and is a potential prognostic biomarker for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common fatal malignancies but the molecular genetic basis of this disease remains unclear. By using genome-wide methylation profiling analysis, we identified CLDN3 as an epigenetically regulated gene in cancer. Here, we investigated its function and clinical relevance in human HCC. CLDN3 downregulation occurred in 87/114 (76.3%) of primary HCCs, where it was correlated significantly with shorter survival of HCC patients (P=0.021). Moreover, multivariate cyclooxygenase regression analysis showed that CLDN3 was an independent prognostic factor for overall survival (P=0.014). Absent expression of CLDN3 was also detected in 67% of HCC cell lines, which was significantly associated with its promoter hypermethylation. Ectopic expression of CLDN3 in HCC cells could inhibit cell motility, cell invasiveness, and tumor formation in nude mice. Mechanistic investigations suggested through downregulation of GSK3B, CTNNB1, SNAI2, and CDH2, CLDN3 could significantly suppress metastasis by inactivating the Wnt/β-catenin-epithelial mesenchymal transition (EMT) axis in HCC cells. Collectively, our findings demonstrated that CLDN3 is an epigenetically silenced metastasis suppressor gene in HCC. A better understanding of the molecular mechanism of CLDN3 in inhibiting liver cancer cell metastasis may lead to a more effective management of HCC patients with the inactivation of CLDN3.