Notch1 promotes hepatitis B virus X protein-induced hepatocarcinogenesis via Wnt/β-catenin pathway

Notch signalling: multifaceted role in development and disease

Notch pathway is an evolutionarily conserved signalling system that operates to influence an astonishing array of cell fate decisions in different developmental contexts. Notch signalling plays important roles in many developmental processes, making it difficult to name a tissue or a developing organ that does not depend on Notch function at one stage or another. Thus, dysregulation of Notch signalling is associated with many developmental defects and various pathological conditions, including cancer. Although many recent advances have been made to reveal different aspects of the Notch signalling mechanism and its intricate regulation, there are still many unanswered questions related to how the Notch signalling pathway functions in so many developmental events. The same pathway can be deployed in numerous cellular contexts to play varied and critical roles in an organism's development and this is only possible because of the complex regulatory mechanisms of the pathway. In this review, we provide an overview of the mechanism and regulation of the Notch signalling pathway along with its multifaceted functions in different aspects of development and disease.

Emerging trends in gastrointestinal cancers: Targeting developmental pathways in carcinogenesis and tumor progression

Gastrointestinal carcinomas are a group of cancers associated with the digestive system and its accessory organs. The most prevalent cancers related to the gastrointestinal tract are colorectal, gall bladder, gastric, hepatocellular, and esophageal cancers, respectively. Molecular aberrations in different signaling pathways, such as signal transduction systems or developmental pathways are the chief triggering mechanisms in different cancers Though a massive advancement in diagnostic and therapeutic interventions results in improved survival of patients with gastrointestinal cancer; the lower malignancy stages of these carcinomas are comparatively asymptomatic. Various gastrointestinal-related cancers are detected at advanced stages, leading to deplorable prognoses and increased rates of recurrence. Recent molecular studies have elucidated the imperative roles of several signaling pathways, namely Wnt, Hedgehog, and Notch signaling pathways, play in the progression, therapeutic responsiveness, and metastasis of gastrointestinal-related cancers. This book chapter gives an interesting update on recent findings on the involvement of developmental signaling pathways their mechanistic insight in gastrointestinalcancer. Subsequently, evidences supporting the exploration of gastrointestinal cancer related molecular mechanisms have also been discussed for developing novel therapeutic strategies against these debilitating carcinomas.

Gambogic acid inhibits HBx-mediated hepatitis B virus replication by targeting the DTX1-Notch signaling pathway

BACKGROUND & AIMS

Current antiviral drugs, including nucleoside analogs and interferon, fail to eliminate the HBV covalently closed circular DNA (cccDNA), which serves as a transcript template in infected hepatocytes. Silencing the HBV X protein, which plays a crucial role in cccDNA transcription, is a promising approach to inhibit HBV replication. Therefore, the identification of novel compounds that can inhibit HBx-mediated cccDNA transcription is critical.

METHODS

Initially, a compound library consisting of 715 monomers derived from traditional Chinese medicines known for their liver-protecting properties was established. Then, MTT assays were used to determine the cytotoxicity of each compound. The effect of candidates on Flag-HBx expression was examined by real-time PCR and western blotting in Flag-HBx transfected HepG2-NTCP cells. Ultimately, the antiviral effect of gambogic acid (GA) on HBV was observed in HBV-infected HepG2-NTCP cells. Mechanistically, the functional role of DTX1 in GA-induced HBV inhibition was examined using RNA-seq. Finally, the antiviral effect of GA was estimated in vivo.

RESULTS

Gambogic acid (GA), a natural bioactive compound with a myriad of biological activities, markedly reduced Flag-HBx expression. Potent and dose-dependent reductions in extracellular HBV RNAs, HBV DNA, HBsAg, HBeAg and HBc protein were discovered three days after GA treatment in HBV-infected cells, accompanied by the absence of significant cytotoxicity. Furthermore, our research revealed that GA exhibited a dose-dependent inhibition of HBx expression, which is a pleiotropic protein required for HBV infection in vivo. We explored the mechanisms underlying GA-mediated inhibition of HBV and confirmed that this inhibition is accomplished by upregulating the expression of the DTX1 gene and boosting the Notch signaling pathway. Finally, the inhibitory effect of GA on HBV replication was tested in vivo using a mouse model of hepatitis B virus recombinant cccDNA.

CONCLUSIONS

Herein, we discovered GA, which is a natural bioactive compound that targets HBx to inhibit hepatitis B virus replication by activating the DTX1-Notch signaling pathway.

HOXB3 promotes trophoblast cell proliferation, invasion, and migration to alleviate preeclampsia via mediating the Notch/Wnt/β-catenin pathway

Preeclampsia (PE) harms a significant number of pregnant women and fetuses. However, because of its complex pathological mechanisms, there is no cure except for delivery. This study identified the impact and mechanisms of action of HOXB3 in PE. The behaviors of HTR-8/SVneo cells were analyzed using a cell counting kit-8, EdU, and transwell assays. The interaction between HOXB3 and Notch1 was assessed using a luciferase reporter and chromatin immunoprecipitation assays. Expression was measured by quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence assays. Additionally, the function of HOXB3 was evaluated in an established rat model of PE. We found that HOXB3 was upregulated in PE. HOXB3 overexpression facilitated trophoblast cell proliferation, migration, and invasion. HOXB3 transcriptionally regulated Notch1 by binding to its promoter. Notch1 knockdown abrogated the functions of HOXB3 and the-catenin pathway in trophoblasts. Suppression of the Wnt/β-catenin pathway abrogated the effects of HOXB3. Additionally, HOXB3 alleviated the symptoms in PE rats. In conclusion, HOXB3 transcriptionally activated Notch1 expression and the-catenin pathway, promoting trophoblast cell proliferation, invasion, and migration, thereby alleviating PE progression. This study provides a novel approach for PE therapy.

Molecular mechanism of albumin in suppressing invasion and metastasis of hepatocellular carcinoma

BACKGROUND & AIMS

Worldwide, hepatocellular carcinoma (HCC) is one of the most common causes of death in people. Albumin (ALB) is considered as an important indicator for HCC prognosis, and evidence has shown HCC cell growth can be regulated by ALB. However, the role of ALB in hepatocarcinogenesis and the mechanism of action is still unknown.

METHODS

The expression of ALB was determined by clinical profiles, immunohistochemistry, and western blot. Wound healing and Transwell assays were conducted to evaluate the effects of ALB during migration and invasion in HCC. We used mass spectrometry coupled isobaric tags for relative and absolute quantitation (iTRAQ)-technology to identify secretory differentially expressed proteins (DEPs) in ALB knockdown HepG2 cells. Western blot, reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay techniques were used for verification.

RESULTS

We suggested that ALB was associated with aggressive metastasis and depleting ALB significantly promoted invasion and migration of HCC. A total of 210 DEPs were identified after silencing of ALB. We observed that a negative correlation between ALB and urokinase plasminogen activator surface receptor (uPAR) expression levels.

CONCLUSIONS

ALB acts as a tumour suppressor and plays a key role in HCC progression, particularly in invasion and metastasis. Suppression of ALB promoted migration and invasion of HCC cells by increasing uPAR, matrix metalloproteinase (MMP2), and MMP9.

When Viruses Cross Developmental Pathways

Aberrant regulation of developmental pathways plays a key role in tumorigenesis. Tumor cells differ from normal cells in their sustained proliferation, replicative immortality, resistance to cell death and growth inhibition, angiogenesis, and metastatic behavior. Often they acquire these features as a consequence of dysregulated Hedgehog, Notch, or WNT signaling pathways. Human tumor viruses affect the cancer cell hallmarks by encoding oncogenic proteins, and/or by modifying the microenvironment, as well as by conveying genomic instability to accelerate cancer development. In addition, viral immune evasion mechanisms may compromise developmental pathways to accelerate tumor growth. Viruses achieve this by influencing both coding and non-coding gene regulatory pathways. Elucidating how oncogenic viruses intersect with and modulate developmental pathways is crucial to understanding viral tumorigenesis. Many currently available antiviral therapies target viral lytic cycle replication but with low efficacy and severe side effects. A greater understanding of the cross-signaling between oncogenic viruses and developmental pathways will improve the efficacy of next-generation inhibitors and pave the way to more targeted antiviral therapies.

Molecular pathways in viral hepatitis-associated liver carcinogenesis: An update

Hepatocellular carcinoma (HCC) is the most common type of cancer among primary malignant tumors of the liver and is a consequential cause of cancer-related deaths worldwide. In recent years, uncovering the molecular mechanisms involved in the development and behavior of this tumor has led to the identification of multiple potential treatment targets. Despite the vast amount of data on this topic, HCC remains a challenging tumor to treat due to its aggressive behavior and complex molecular profile. Therefore, the number of studies aiming to elucidate the mechanisms involved in both carcinogenesis and tumor progression in HCC continues to increase. In this context, the close association of HCC with viral hepatitis has led to numerous studies focusing on the direct or indirect involvement of viruses in the mechanisms contributing to tumor development and behavior. In line with these efforts, this review was undertaken to highlight the current understanding of the molecular mechanisms by which hepatitis B virus (HBV) and hepatitis C virus (HCV) participate in oncogenesis and tumor progression in HCC and summarize new findings. Cumulative evidence indicates that HBV DNA integration promotes genomic instability, resulting in the overexpression of genes related to cancer development, metastasis, and angiogenesis or inactivation of tumor suppressor genes. In addition, genetic variations in HBV itself, especially preS2 deletions, may play a role in malignant transformation. Epigenetic dysregulation caused by both viruses might also contribute to tumor formation and metastasis by modifying the methylation of DNA and histones or altering the expression of microRNAs. Similarly, viral proteins of both HBV and HCV can affect pathways that are important anticancer targets. The effects of these two viruses on the Hippo-Yap-Taz pathway in HCC development and behavior need to be investigated. Additional, comprehensive studies are also needed to determine these viruses' interaction with integrins, farnesoid X, and the apelin system in malignant transformation and tumor progression. Although the relationship of persistent inflammation caused by HBV and HCV hepatitis with carcinogenesis is well defined, further studies are warranted to decipher the relationship among inflammasomes and viruses in carcinogenesis and elucidate the role of virus-microbiota interactions in HCC development and progression.

Notch Signaling Regulation in HCC: From Hepatitis Virus to Non-Coding RNAs

The Notch family includes evolutionary conserved genes that encode for single-pass transmembrane receptors involved in stem cell maintenance, development and cell fate determination of many cell lineages. Upon activation by different ligands, and depending on the cell type, Notch signaling plays pleomorphic roles in hepatocellular carcinoma (HCC) affecting neoplastic growth, invasion capability and stem like properties. A specific knowledge of the deregulated expression of each Notch receptor and ligand, coupled with resultant phenotypic changes, is still lacking in HCC. Therefore, while interfering with Notch signaling might represent a promising therapeutic approach, the complexity of Notch/ligands interactions and the variable consequences of their modulations raises concerns when performed in undefined molecular background. The gamma-secretase inhibitors (GSIs), representing the most utilized approach for Notch inhibition in clinical trials, are characterized by important adverse effects due to the non-specific nature of GSIs themselves and to the lack of molecular criteria guiding patient selection. In this review, we briefly summarize the mechanisms involved in Notch pathway activation in HCC supporting the development of alternatives to the γ-secretase pan-inhibitor for HCC therapy.

Niclosamide-loaded polymeric micelles ameliorate hepatocellular carcinoma in vivo through targeting Wnt and Notch pathways

AIM

Niclosamide (NIC) is an anthelmintic agent repurposed as a potent anticancer agent. However, its use is hindered by its poor solubility. We investigated the underlying mechanisms of NIC anticancer activity employing a novel oral NIC pluronic-based nanoformulation and tested its effect in thioacetamide-induced hepatocellular carcinoma (HCC) in rats. We evaluated its antitumor effect through regulating Wnt/β-catenin and Notch signaling pathways and apoptosis.

MAIN METHODS

Niclosamide-loaded pluronic nanoparticles (NIC-NPs) were optimally developed and characterized with sustained release properties up to 7 days. Sixteen weeks after HCC induction, NIC (70 mg/kg) and an equivalent dose of NIC-NPs were administered orally for 3 consecutive weeks. Hepatocyte integrity was assessed by measuring serum levels of aminotransferases, ALP, GGT, bilirubin, albumin and total protein. HCC development was detected by measuring AFP expression. Necroinflammation and fibrosis were scored by histopathological examination. Wnt/β-catenin and Notch signaling were evaluated by measuring hepatic mRNA levels of Wnt3A, Lrp5 and Lrp6 Co-receptors, Dvl-2, Notch1 and Hes1 and β-catenin protein levels. Apoptosis was assessed by measuring mRNA and protein levels of cyclin D1 and caspase-3.

KEY FINDING

The novel NIC-NPs restored liver integrity, reduced AFP levels and showed improved anticancer and proapoptotic activities compared to drug alone. The inhibitory effect of NIC on Wnt/β-catenin and Notch signaling pathways was potentiated by the NIC-NPs formulation.

SIGNIFICANCE

We conclude that NIC acts by inhibiting Wnt/β-catenin and Notch signaling and inducing apoptosis in HCC. Developing pluronic-based nanoformulations may be a promising approach to improve NIC solubility and offer the possibility of controlled release.

NAP1L1 is a prognostic biomarker and contribute to doxorubicin chemotherapy resistance in human hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is one of the most fatal cancers, and its molecular basis needs to be delineated to identify biomarkers for its potential treatment. The purpose of this study was to identify a novel gene, nucleosome assembly proteins 1-like 1 protein (NAP1L1), associated with aggressive phenotypes of HCC.

Methods

Immunohistochemical staining was used to detect NAP1L1 protein expression in HCC tissues. The prognostic value of NAP1L1 expression was determined using Kaplan–Meier analysis and the Cox proportional hazards model. CCK-8 and apoptosis assays were used to detect the chemosensitivity in vitro. Xenograft tumor models were used to evaluate tumor cell proliferation and chemosensitivity in vivo.

Results

NAP1L1 expression was significantly upregulated in tumor tissues as compared to adjacent non-tumor tissues. High NAP1L1 expression in HCC tissues was associated with aggressive clinicopathologic features, such as serum AFP levels, tumor size and tumor number. Patients with high NAP1L1 expression had poor overall survival in our cohort and in the extra-validation cohort analyzed by TCGA microarray dataset and was further identified as an independent prognostic factor in HCC patients treated with radical resection. Both in vitro and in vivo assays showed that NAP1L1 promoted HCC cell proliferation and contribute to chemotherapy resistance. Further analyses found that some certain stemness associated genes were decreased concurrently with NAP1L1 down-regulation in HCC cell lines.

Conclusions

Our findings support that NAP1L1 is a prognostic biomarker and may contribute to chemotherapy resistance in human hepatocellular carcinoma.

Analysis of head and neck carcinoma progression reveals novel and relevant stage-specific changes associated with immortalisation and malignancy

We report changes in the genomic landscape in the development of head and neck squamous cell carcinomas HNSCC from potentially premalignant lesions (PPOLS) to malignancy and lymph node metastases. Likely pathological mutations predominantly involved a relatively small set of genes reported previously (TP53, KMT2D, CDKN2A, PIK3CA, NOTCH1 and FAT1) but also other predicted cancer drivers (MGA, PABPC3, NR4A2, NCOR1 and MACF1). Notably, all these mutations arise early and are present in PPOLs. The most frequent genetic changes, which follow acquisition of immortality and loss of senescence, are of consistent somatic copy number alterations (SCNAs) involving chromosomal regions enriched for genes in known and previously unreported cancer-related pathways. We mapped the evolution of SCNAs in HNSCC progression. One of the earliest SCNAs involved deletions of CSMD1 (8p23.2). CSMD1 deletions or promoter hypermethylation were present in all of the immortal PPOLs and occurred at high frequency in the immortal HNSCC cell lines. Modulation of CSMD1 in cell lines revealed significant suppression of proliferation and invasion by forced expression, and significant stimulation of invasion by knockdown of expression. Known cancer drivers NOTCH1, PPP6C, RAC1, EIF4G1, PIK3CA showed significant increase in frequency of SCNA in transition from PPOLs to HNSCC that correlated with their expression. In the later stages of progression, HNSCC with and without nodal metastases showed some clear differences including high copy number gains of CCND1, hsa-miR-548k and TP63 in the metastases group.

Wnt3a promotes radioresistance via autophagy in squamous cell carcinoma of the head and neck

The canonical Wnt/β‐catenin signalling pathway and autophagy play critical roles in cancer progression. However, the role of Wnt‐mediated autophagy in cancer radioresistance remains unclear. In this study, we found that irradiation activated the Wnt/β‐catenin and autophagic signalling pathways in squamous cell carcinoma of the head and neck (SCCHN). Wnt3a is a classical ligand that activated the Wnt/β‐catenin signalling pathway, induced autophagy and decreased the sensitivity of SCCHN to irradiation both in vitro and in vivo. Further mechanistic analysis revealed that Wnt3a promoted SCCHN radioresistance via protective autophagy. Finally, expression of the Wnt3a protein was elevated in both SCCHN tissues and patients' serum. Patients showing high expression of Wnt3a displayed a worse prognosis. Taken together, our study indicates that both the canonical Wnt and autophagic signalling pathways are valuable targets for sensitizing SCCHN to irradiation.

The Carcinogenic Role of the Notch Signaling Pathway in the Development of Hepatocellular Carcinoma

The Notch signaling pathway, known to be a highly conserved signaling pathway in embryonic development and adult tissue homeostasis, participates in cell fate decisions that include cellular differentiation, cell survival and cell death. However, other studies have shown that aberrant in Notch signaling is pro-tumorigenic, particularly in hepatocellular carcinoma (HCC). HCC is one of the most common malignant tumors in the world and has a high mortality rate. Growing evidence supports that Notch signaling plays a critical role in the development of HCC by regulating the tumor microenvironment, tumorigenesis, progression, angiogenesis, invasion and metastasis. Accordingly, overexpression of Notch is closely associated with poor prognosis in HCC. In this review, we focus on the pro-tumorigenic role of Notch signaling in HCC, summarize the current knowledge of Notch signaling and its role in HCC development, and outline the therapeutic potential of targeting Notch signaling in HCC.

SENP2 exerts an anti‑tumor effect on chronic lymphocytic leukemia cells through the inhibition of the Notch and NF‑κB signaling pathways

Chronic lymphocytic leukemia (CLL) is one of the most often diagnosed hematological malignant tumors in the Western world and a type of inert B-cell lymphoma that commonly attacks the elderly. Small ubiquitin related modifier (SUMO)-specific protease 2 (SENP2) can act as a suppressor in various types of cancer by regulating the stability of β-catenin to affect the Notch signaling pathway; however, it has a low expression level in CLL cells. In this study, we firstly used western blot analysis and RT-qPCR to detect the protein and mRNA expression levels of SENP2 in the peripheral blood of patients with CLL and healthy volunteers. Secondly, we overexpressed or knocked down the expression of SENP2 in CLL cells and then determined the cell invasive and chemotactic ability in a Transwell assay and chemotaxis assay. We examined the sensitivity of the cells to cytarabine and dexamethasone via a CCK-8 assay and determined the cell apoptotic condition and the expression of the Notch signaling pathway using flow cytometry and western blot analysis. The results demonstrated that the patients with CLL had relatively low expression levels of SENP2. The overexpression of SENP2 in the CLL cells decreased their invasive and proliferative ability, as well as their chemotactic response and enhanced their sensitivity to cytarabine and dexamethasone, while it promoted cell apoptosis. The silencing of SENP2 in the CLL cells generally produced the opposite results. We thus hypothesized that the overexpression of SENP2 downregulated β-catenin expression, thus inhibiting the Notch signaling pathway in CLL cells. Moreover, the nuclear factor (NF)-κB signaling pathway was also regulated by the overexpression of SENP2. On the whole, the findings of this study indicate tha SENP2 can act as a tumor suppressor in CLL cells, and may thus prove to be a novel target for CLL treatment in clinical practice.

iNOS promotes CD24+CD133+ liver cancer stem cell phenotype through a TACE/ADAM17-dependent Notch signaling pathway

CD24⁺CD133⁺ liver cancer stem cells (LCSCs) express higher levels of the inducible nitric oxide synthase (iNOS) and possess self-renewal and tumor growth properties. iNOS is associated with more aggressive hepatocellular carcinoma (HCC), leading to the upregulation of Notch1 signaling. The activation of Notch1 by iNOS/NO is dependent on cGMP/PKG-mediated activation of TACE and upregulation of iRhom-2. The expression of iNOS, CD24, and CD133 correlates with the expression of activated TACE and Notch signaling in more aggressive human HCC. These findings have implications for understanding how LCSCs are regulated in the setting of chronic inflammation, where signals to upregulate iNOS are often present. Targeting iNOS could have therapeutic benefit in HCC.

The inducible nitric oxide synthase (iNOS) is associated with more aggressive solid tumors, including hepatocellular carcinoma (HCC). Notch signaling in cancer stem cells promotes cancer progression and requires Notch cleavage by ADAM (a disintegrin and metalloprotease) proteases. We hypothesized that iNOS/NO promotes Notch1 activation through TACE/ADAM17 activation in liver cancer stem cells (LCSCs), leading to a more aggressive cancer phenotype. Expression of the stem cell markers CD24 and CD133 in the tumors of patients with HCC was associated with greater iNOS expression and worse outcomes. The expression of iNOS in CD24⁺CD133⁺ LCSCs, but not CD24⁻CD133⁻ LCSCs, promoted Notch1 signaling and stemness characteristics in vitro and in vivo, as well as accelerating HCC initiation and tumor formation in the mouse xenograft tumor model. iNOS/NO led to Notch1 signaling through a pathway involving the soluble guanylyl cyclase/cGMP/PKG-dependent activation of TACE/ADAM17 and up-regulation of iRhom2 in LCSCs. In patients with HCC, higher TACE/ADAM17 expression and Notch1 activation correlated with poor prognosis. These findings link iNOS to Notch1 signaling in CD24⁺CD133⁺ LCSCs through the activation of TACE/ADAM17 and identify a mechanism for how iNOS contributes to progression of CD24⁺CD133⁺ HCC.

Delta-like ligand 4 in hepatocellular carcinoma intrinsically promotes tumour growth and suppresses hepatitis B virus replication

AIM

To investigate the role of Delta-like ligand 4 (DLL4) on tumour growth in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) in vivo.

METHODS

We suppressed DLL4 expression in an HBV expressing HCC cell line, HepG2.2.15 and analysed the growth ability of cells as subcutaneous tumours in nude mice. The expression of tumour angiogenesis regulators, VEGF-A and VEGF-R2 in tumour xenografts were examined by western blotting. The tumour proliferation and neovasculature were examined by immunohistochemistry. The viral replication and viral protein expression were measured by quantitative PCR and western blotting, respectively.

RESULTS

Eighteen days after implantation, tumour volume in mice implanted with shDLL4 HepG2.2.15 was significantly smaller than in mice implanted with control HepG2.2.15 (P < 0.0001). The levels of angiogenesis regulators, VEGF-A and VEGF-R2 were significantly decreased in implanted tumours with suppressed DLL4 compared with the control group (P < 0.001 and P < 0.05, respectively). Furthermore, the suppression of DLL4 expression in tumour cells reduced cell proliferation and the formation of new blood vessels in tumours. Unexpectedly, increased viral replication was observed after suppression of DLL4 in the tumours.

CONCLUSION

This study demonstrates that DLL4 is important in regulating the tumour growth of HBV-associated HCC as well as the neovascularization and suppression of HBV replication.

HBx promotes the proliferative ability of HL‑7702 cells via the COX‑2/Wnt/β‑catenin pathway

Hepatitis B virus X protein (HBx) has been termed a viral oncoprotein, and is involved in the initiation and progression of hepatocellular carcinoma (HCC). Cyclooxygenase‑2 (COX‑2) and β‑catenin have been attributed to the oncogenic activity of HBx in HBV‑associated HCC. The present study aimed to determine whether there is crosstalk between COX‑2 and the Wnt/β‑catenin signaling pathway during HL‑7702‑HBx cell proliferation, and to investigate the associated underlying molecular mechanism.  In the present study, cell proliferation assay, colony formation assay and flow cytometric analysis were used to detect the proliferative ability of cells. Reverse transcription‑quantitative polymerase chain reaction and western blotting were performed to examine the mRNA and protein expression of COX‑2, β‑catenin, cyclin‑D1 and c‑myc. The results demonstrated that HL‑7702‑HBx exhibited increased cell proliferation, higher colony formation efficiency and a shortened G1 period of the cell cycle. In addition, the mRNA and protein expression levels of COX‑2 were increased, and this was associated with HL‑7702‑HBx cell growth. Furthermore, the expression of β‑catenin and its target genes, cyclin‑D1 and c‑myc proto‑oncogene protein, was upregulated by HBx via COX‑2. Finally, HBx promoted HL‑7702 cell proliferation through the Wnt/β‑catenin signaling pathway. In conclusion, the primary finding of the present study was that HBx may promote HL‑7702 cell proliferation via the COX‑2/Wnt/β‑catenin pathway. Thus, it may be helpful to further investigate the molecular mechanism of HBV‑associated hepatocellular carcinoma.

Inhibition of canonical WNT/β-catenin signaling is involved in leflunomide (LEF)-mediated cytotoxic effects on renal carcinoma cells

Leflunomide (LEF), an inhibitor of dihydroorotate dehydrogenase (DHODH) in pyrimidine biosynthetic pathway, is an immunomodulatory agent approved for the treatment of rheumatoid arthritis. In this study, we show that LEF significantly reduced cell proliferation of renal carcinoma cells in a concentration-dependent manner. LEF at 50 μM induced S-phase arrest and autophagy. Higher doses of LEF (>50 μM) effectively induced cell apoptosis. Modulating the concentration of LEF resulted in distinct effects on the expression of regulatory proteins associated with cell cycle, apoptosis, and autophagy. In particular, high concentrations of LEF inhibited canonical WNT signaling by promoting nucleo-cytoplasmic shuttling and proteasome-dependent degradation of β-catenin. Mechanistic studies showed that the repression of AKT activation partly accounted for LEF-mediated WNT inhibition. Gene expression microarray revealed that LEF treatment greatly inhibited the expression of FZD10 gene, a receptor mediating WNT/β-catenin activation. In vivo xenograft study in NOD/SCID mice further validated the inhibitory effects of LEF on tumor growth and Wnt/β-catenin signaling. However, LEF treatment also triggered cell autophagy and elevated the expression of WNT3a, which ameliorated its cytotoxic effects. The combination of LEF with a WNT inhibitor IWP-2 or autophagy inhibitor HCQ could yield an enhanced anti-tumor outcome. Taken together, these results identify the potential utility and pharmacological feature of LEF in the chemotherapy of renal cell carcinoma (RCC).

Deubiquitinase inhibitor b-AP15 activates endoplasmic reticulum (ER) stress and inhibits Wnt/Notch1 signaling pathway leading to the reduction of cell survival in hepatocellular carcinoma cells

b-AP15, a potent and selective inhibitor of the ubiquitin-specific peptidase 14 (USP14), displays in vitro and in vivo antitumor abilities on some types of cancer cells. However, the mechanism underlying its action is not well elucidated. The purposes of the present study are to observe the potential impacts of b-AP15 on cell survival of hepatocellular carcinoma cells and to investigate whether and how this compound inhibits some survival-promoting signaling pathways. We found that b-AP15 significantly decreased cell viability and increased cell apoptosis in a dose-dependent manner in hepatocellular carcinoma cells, along with the perturbation of cell cycle and the decreased expressions of cell cycle-related proteins. We also demonstrated that the endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) were enhanced by b-AP15 supplementation. The inhibition of ER stress/UPR only partly attenuated the cytotoxicity of b-AP15 on hepatocellular carcinoma cells. In addition, b-AP15 treatment inhibited Wnt/β-catenin and Notch1 signaling pathways, and suppressed phosphorylation of STAT3, Akt, and Erk1/2, which were not restored by the inhibition of ER stress/UPR. Furthermore, the expression levels of signaling molecules in Notch1 were reduced by specific inhibitor of Wnt/β-catenin pathway. Notably, either Wnt or Notch1 signaling inhibitor mitigated phosphorylation of STAT3, Akt, and Erk1/2, and mimicked the cytotoxicity of b-AP15 on hepatocellular carcinoma cells. These results clearly indicate that b-AP15 induced cytotoxic response to hepatocellular carcinoma cells by augmenting ER stress/UPR and inhibiting Wnt/Notch1 signaling pathways. This new finding provides a novel mechanism by which b-AP15 produces its antitumor therapeutic effects.

Deregulation of Frizzled Receptors in Hepatocellular Carcinoma

G protein-coupled receptors (GPCRs) have a substantial role in tumorigenesis and are described as a “cancer driver”. Aberrant expression or activation of GPCRs leads to the deregulation of downstream signaling pathways, thereby promoting cancer progression. In hepatocellular carcinoma (HCC), the Wnt signaling pathway is frequently activated and it is associated with an aggressive HCC phenotype. Frizzled (FZD) receptors, a family member of GPCRs, are known to mediate Wnt signaling. Accumulating findings have revealed the deregulation of FZD receptors in HCC and their functional roles have been implicated in HCC progression. Given the important role of FZD receptors in HCC, we summarize here the expression pattern of FZD receptors in HCC and their corresponding functional roles during HCC progression. We also further review and highlight the potential targeting of FZD receptors as an alternative therapeutic strategy in HCC.

Analysis of microarrays of miR-34a and its identification of prospective target gene signature in hepatocellular carcinoma

BACKGROUND

Currently, some studies have demonstrated that miR-34a could serve as a suppressor of several cancers including hepatocellular carcinoma (HCC). Previously, we discovered that miR-34a was downregulated in HCC and involved in the tumorigenesis and progression of HCC; however, the mechanism remains unclear. The purpose of this study was to estimate the expression of miR-34a in HCC by applying the microarray profiles and analyzing the predicted targets of miR-34a and their related biological pathways of HCC.

METHODS

Gene expression omnibus (GEO) datasets were conducted to identify the difference of miR-34a expression between HCC and corresponding normal tissues and to explore its relationship with HCC clinicopathologic features. The natural language processing (NLP), gene ontology (GO), pathway and network analyses were performed to analyze the genes associated with the carcinogenesis and progression of HCC and the targets of miR-34a predicted in silico. In addition, the integrative analysis was performed to explore the targets of miR-34a which were also relevant to HCC.

RESULTS

The analysis of GEO datasets demonstrated that miR-34a was downregulated in HCC tissues, and no heterogeneity was observed (Std. Mean Difference(SMD) = 0.63, 95% confidence intervals(95%CI):[0.38, 0.88], P < 0.00001; P_{heterogeneity} = 0.08 I² = 41%). However, no association was found between the expression value of miR-34a and any clinicopathologic characteristics. In the NLP analysis of HCC, we obtained 25 significant HCC-associated signaling pathways. Besides, we explored 1000 miR-34a-related genes and 5 significant signaling pathways in which CCND1 and Bcl-2 served as necessary hub genes. In the integrative analysis, we found 61 hub genes and 5 significant pathways, including cell cycle, cytokine-cytokine receptor interaction, notching pathway, p53 pathway and focal adhesion, which proposed the relevant functions of miR-34a in HCC.

CONCLUSION

Our results may lead researchers to understand the molecular mechanism of miR-34a in the diagnosis, prognosis and therapy of HCC. Therefore, the interaction between miR-34a and its targets may promise better prediction and treatment for HCC. And the experiments in vivo and vitro will be conducted by our group to identify the specific mechanism of miR-34a in the progress and deterioration of HCC.

Modulation of Wnt signaling pathway by hepatitis B virus

Hepatitis B virus (HBV) has a global distribution and is one of the leading causes of hepatocellular carcinoma. The precise mechanism of pathogenicity of HBV-associated hepatocellular carcinoma (HCC) is not yet fully understood. Viral-related proteins are known to take control of several cellular pathways like Wnt/β-catenin, TGF-β, Raf/MAPK and ROS for the virus's own replication. This affects cellular persistence, multiplication, migration, alteration and genomic instability. The Wnt/FZD/β-catenin signaling pathway plays a significant role in the pathology and physiology of the liver and has been identified as a main factor in HCC development. The role of β-catenin is linked mainly to the canonical pathway of the signaling system. Progression of liver diseases is known to be accompanied by disturbances in β-catenin expression (mainly overexpression), with its cytoplasmic or nuclear translocation. In recent years, studies have documented that the HBV X protein and hepatitis B surface antigen (HBsAg) can act as pathogenic factors that are involved in the modulation and induction of canonical Wnt signaling pathway. In the present review we explore the interaction of HBV genome products with components of the Wnt/β-catenin signaling pathway that results in the enhancement of the pathway and leads to hepatocarcinogenesis.

Expression of Wnt3a in hepatocellular carcinoma and its effects on cell cycle and metastasis

Invasion and metastasis are the primary causes of mortality from hepatocellular carcinoma (HCC). Effective inhibition against participants in the tumourigenesis and metastasis process is critical for treatment of HCC. Wnt3a is involved in the development and metastasis of many malignant tumours. However, the specific mechanisms of Wnt3a-mediated cell proliferation, invasion and metastasis in HCC remain unclear. In this study, we found that Wnt3a and its target gene c-Myc showed higher expression in tumour tissues than normal liver tissues in HCC patients; 71.8% of the cases studied had high Wnt3a and c-Myc expression levels (n=32); Wnt3a expression positively correlated with its target genes MMP-7 and c-Myc. Intriguingly, the expression of Wnt3a, MMP-7 and c-Myc is significantly correlated with Notch3 and Hes1 expression. In vitro experiments showed that Wnt3a was highly expressed in MHcc97H and SK-Hep-1 cells. Therefore, Wnt3a expression was silenced with siRNA, and then, MTT, flow cytometry, wound healing and Transwell assays were performed to analyse cell proliferation, cycle, migration and invasion. The results demonstrated that downregulation of Wnt3a expression inhibited cell viability and induced G₀/G₁ cell cycle arrest via decreased expression of cyclin D1 and c-Myc and increased expression of p21 and p27. In addition, deletion of Wnt3a significantly inhibited migration and invasion by downregulating MMP-2/-7/-9 expression via the MAPK (p38, ERK1/2 and JNK) pathway. In conclusion, our data show that Wnt3a is involved in HCC development. Wnt3a may be an effective target for treatment of HCC.

The regulation of proteins associated with the cytoskeleton by hepatitis B virus X protein during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is a major malignant disease worldwide, and chronic hepatitis B virus (HBV) infection is one of the primary causes for this type of cancer. Hepatitis B virus X protein (HBx) is a non-structural protein encoded by the viral genome that has significant effects on the pathogenesis of HCC. With the development of high-throughput assays and technologies, the abnormal HBx-induced expression of certain cellular proteins with assorted biological functions has been investigated. These target proteins identified by various methods include specific proteins associated with the cellular cytoskeleton, which contribute to HBx-induced hepatocarcinogenesis. In addition, the cytoskeletal proteins deregulated by HBx are involved in cell morphogenesis, adhesion, migration and proliferation. This review aims to summarize the current understanding of the expression profiles of HBx-associated cytoskeletal proteins, as well as their complex functions and underlying mechanisms in hepatocarcinogenesis. Considering that the potential therapeutics for various types of tumors may function through the stabilization of cytoskeletal proteins in order to restrict cellular movement and limit intracellular processes, clarifying the mechanisms underlying protein-associated cytoskeleton dysregulation by HBx may provide novel possibilities and potent therapeutic targets for HBV-associated HCC.

The Notch pathway promotes the cancer stem cell characteristics of CD90+ cells in hepatocellular carcinoma

CD90 has been identified as a marker for liver cancer stem cells (CSCs) that are responsible for tumorigenic activity, but it is not known how CD90⁺ cells contribute to tumor initiation and progression. Our data demonstrated that high expression of CD90 in Hepatocellular Carcinoma (HCC) tissues correlated with venous filtration in HCC patients. CD90⁺ cells isolated from HCC cell lines exhibited increased tumorigenicity, chemoresistance, tumor invasion and metastasis. Notch pathway was activated in CD90⁺ cells and we found that inhibition of Notch pathway in CD90⁺ CSCs decreased tumorigenicity, cell invasion, migration and expression of stem cell related genes. Activation of Notch pathway in CD90⁻ cells induced self-renewal, invasion and migration. Furthermore, we observed that cancer stem cell features were facilitated by stimulating G1-S transition in the cell cycle phase and inhibiting apoptosis mediated by Notch pathway. Our findings suggested CD90 could be used as a potential biomarker for HCC CSCs, and that cancer stem cell activity was elevated through up activated Notch pathway in CD90⁺ CSCs.

Hepatitis B virus X protein and hypoxia‑inducible factor-1α stimulate Notch gene expression in liver cancer cells

Increasing evidence has demonstrated that Notch genes, including Notch1, Notch2, Notch3 and Notch4, are involved in carcinogenesis. However, the expression and regulation of Notch genes in hepatocellular carcinoma (HCC) tissues have not been fully investigated. In the present study, immunohistochemical and quantitative real-time PCR (qPCR) analyses were performed to examine the expression of Notch genes in normal human liver, HBV-related HCC and paired peritumoral tissues. Additionally, qPCR and western blotting were utilized to investigate the impact of hepatitis B virus X protein (HBx) and hypoxia‑inducible factor-1α (HIF-1α) on the regulation of Notch gene expression. The immunohistochemical and qPCR results showed that the expression levels of Notch1, Notch3 and Notch4 were significantly higher in HCC tissues than the levels in peritumoral and normal liver tissues. However, no significant difference in Notch2 expression was found between HCC and peritumoral tissues. Among the four Notch genes, immunohistochemical analyses found that only the increased level of Notch3 in HCC tissues was positively correlated with vascular invasion of liver cancer (P<0.05). Moreover, we found that overexpression of both HBx and HIF-1α increased the expression of Notch1, Notch3 and Notch4 in HepG2 and Bel-7404 cell lines. In summary, the present study demonstrated that Notch1, Notch3 and Notch4 were upregulated in HCC tissues and that HBx and HIF-1α may be the factors that cause the overexpression of Notch genes. Furthermore, the increased expression of Notch3 was closely related to the vascular invasiveness of HCC.

Notch and Wnt/β-catenin signaling pathway play important roles in activating liver cancer stem cells

Human hepatocellular carcinoma (HCC) is driven and maintained by liver cancer stem cells (LCSCs) that display stem cell properties. These LCSCs are promoted by the intersecting of Notch and Wnt/β-Catenin signaling pathways. In this study, we demonstrate that LCSCs with markers CD90, CD24, CD13, and CD133 possess stem properties of self-renewal and tumorigenicity in NOD/SCID mice. The increased expression of these markers was correlated with advanced disease stage, larger tumors, and worse overall survival in 61 HCC cases. We also found that both Notch and Wnt/β-catenin signaling pathways played important roles in increasing the stem-ness characteristics of LCSCs. Our data suggested that Notch1 was downstream of Wnt/β-catenin. The active form of Notch1 intracellular domain (NICD) expression depended on Wnt/β-catenin pathway activation. Moreover, Notch1 negatively contributed to Wnt/β-catenin signaling modulation. Knock down of Notch1 with lentivirus N1ShRNA up-regulated the active form of β-catenin. Ectopic expression of NICD with LV-Notch1 in LCSCs attenuated β-catenin/TCF dependent luciferase activity significantly. In addition, there was a non-proteasome mediated feedback loop between Notch1 and Wnt/β-catenin signaling in LCSCs. The central role of Notch and the Wnt/β-catenin signaling pathway in LCSCs may provide an attractive therapeutic strategy against HCC.

Co-regulation of the Notch and Wnt signaling pathways promotes supporting cell proliferation and hair cell regeneration in mouse utricles

This work sought to determine the crosstalk between the Notch and Wnt signaling pathways in regulating supporting cell (SC) proliferation and hair cell (HC) regeneration in mouse utricles. We cultured postnatal day (P)3 and P60 mouse utricles, damaged the HCs with gentamicin, and treated the utricles with the γ-secretase inhibitor DAPT to inhibit the Notch pathway and with the Wnt agonist QS11 to active the Wnt pathway. We also used Sox2-CreER, Notch1-flox (exon 1), and Catnb-flox (exon 3) transgenic mice to knock out the Notch pathway and activate the Wnt pathway in Sox2+ SCs. Notch inhibition alone increased SC proliferation and HC number in both undamaged and damaged utricles. Wnt activation alone promoted SC proliferation, but the HC number was not significantly increased. Here we demonstrated the cumulative effects of Notch inhibition and Wnt activation in regulating SC proliferation and HC regeneration. Simultaneously inhibiting Notch and overexpressing Wnt led to significantly greater SC proliferation and greater numbers of HCs than manipulating either pathway alone. Similar results were observed in the transgenic mice. This study suggests that the combination of Notch inhibition and Wnt activation can significantly promote SC proliferation and increase the number of regenerated HCs in mouse utricle.

Hepatitis B Virus X Protein Driven Alpha Fetoprotein Expression to Promote Malignant Behaviors of Normal Liver Cells and Hepatoma Cells

Background: The infection of Hepatitis B virus (HBV) is closely associated with the development of hepatocellular carcinoma(HCC), HBV-X protein(HBx) is able to induce expression of alpha-fetoprotein(AFP) in normal liver cells, and AFP harbors a function to promote malignant transformation of normal liver cells, but the role AFP playing in malignant behaviors of HCC cells is still unclear.

Methods: Fifty-six liver tissue samples were collected from the clinical patients through hepatectomy(include normal liver tissues, HBV-related hepatitis liver tissues and HBV-related HCC tissues), and diagnosis of these tissues by pathology section, expression of AFP, Ras and CXCR4 were evidenced by immunohisochemical staining and Western blotting; The proliferation of human normal liver cells line L-02 cells and human hepatoma cells line, HLE cells(non AFP-producing) were performed by MTT method; Repaired capacity of L-02 and HLE cells were compared by wound healing assay; Migration and invasion of these cells were analyzed by Transwell chamber assay; HBx expressed vectors(pcDNA3.1-HBx) were constructed and transfected into L-02 and HLE cells, effects of pcDNA3.1-HBx on the malignant behaviors were also detected by MTT, Transwell chamber assay and the expression of AFP, Ras and CXCR4 were evidenced by Western blotting.

Results: we found that expression of AFP, Ras and CXCR4 in HBV-related HCC and lymph nodes metastasis tissues were significantly elevated compared with HBV-related HCC, non metastasis tissues and HBV-related hepatitis tissues; Expression of AFP, Ras and CXCR4 in HBV-related hepatitis tissues were significantly enhanced compared with normal liver tissues; The growth ratio, migratory and invasive ability, expression of AFP, Ras and CXCR4 of the cells were outstanding promoted while L-02 and HLE cells were transfected with pcDNA3.1-HBx vectors. The proliferation ratio, migration and invasion ability, and expression of Ras and CXCR4 were significantly inhibited while L-02-X and HLE-X cells(stably transfected with pcDNA3.1-HBx) were silenced AFP expression by AFP-siRNA.

Conclusions: HBx through stimulating expression of AFP to promote malignant behaviors of human normal liver cells and HCC cells; AFP maybe used as a novel biotarget for therapeutics of HCC patients.

Hepatitis B Virus HBx Activates Notch Signaling via Delta-Like 4/Notch1 in Hepatocellular Carcinoma

Hepatitis virus B (HBV) infection is one of the major causes of hepatocellular carcinomas (HCC). HBx protein encoded in HBV genome is one of the key viral factors leading to malignant transformation of infected cells. HBx functions by interfering with cellular functions, causing aberration in cellular behaviour and transformation. Notch signalling is a well-conserved pathway involved in cellular differentiation, cell survival and cell death operating in various types of cells. Aberration in the Notch signalling pathways is linked to various tumors, including HCC. The role of HBx on the Notch signalling in HCC, however, is still controversial. In this study, we reported that HBV genome-containing HCC cell line HepG2 (HepG2.2.15) expressed higher Notch1 and Delta-like 4 (Dll4), compared to the control HepG2 without HBV genome. This upregulation coincided with increased appearance of the cleavage of Notch1, indicating constitutively activated Notch signalling. Silencing of HBx specifically reduced the level of Dll4 and cleaved Notch1. The increase in Dll4 level was confirmed in clinical specimens of HCC lesion, in comparison with non-tumor lesions. Using specific signalling pathway inhibitors, we found that MEK1/2, PI3K/AKT and NF-κB pathways are critical for HBx-mediated Dll4 upregulation. Silencing of HBx clearly decreased the level of phosphorylation of Akt and Erk1/2. Upon silencing of Dll4 in HepG2.2.15, decreased cleaved Notch1, increased apoptosis and cell cycle arrest were observed, suggesting a critical role of HBx-Dll4-Notch1 axis in regulating cell survival in HCC. Furthermore, clonogenic assay confirmed the important role of Dll4 in regulating cell survival of HBV-genome containing HCC cell line. Taken together, we reported a link between HBx and the Notch signalling in HCC that affects cell survival of HCC, which can be a potential target for therapy.

The enhanced expression of death receptor 5 (DR5) mediated by HBV X protein through NF-kappaB pathway is associated with cell apoptosis induced by (TNF-α related apoptosis inducing ligand) TRAIL in hepatoma cells

Background

HBV X protein (HBX) is associated with cell apoptosis mediated by TNF-α related apoptosis inducing ligand (TRAIL), while the role of HBX on the expressions of TRAIL receptors death receptor 4 (DR4) and DR5 are unclear. In this study, we detected the cell apoptosis induced by TRAIL as well as gene and protein expressions of DR4 and DR5 in Huh-7 cells steadily transfected with HBX (Huh-7-HBX cells). In addition, we investigated the activation of different pathways associated with the expressions of TRAIL receptors in Huh-7-HBX cells.

Methods

The apoptosis of Huh-7-HBX cells induced by TRAIL was evaluated by flow cytometry analysis. The levels of DR4 and DR5 expression in cells were determined by real-time PCR and western blotting analysis. The activities of JNK pathway and NF-kappaB (NF-κB) pathway were demonstrated by western blotting assay.

Results

Compared to control cells, the percentage of cell apoptosis was increased in Huh-7-HBX cells. The increased expressions of DR4 and DR5 on gene and protein levels were observed in Huh-7-HBX cells. Further researches suggested that activation of JNK pathway was increased but not involved in the expression of TRAIL receptors in HBX positive cells. The activation of NF-κB pathway increased and was responsible for DR5 expression and cell apoptosis in HBX positive cells.

Conclusions

These results demonstrate that increased apoptosis induced by TRAIL is associated with increased expression of DR5 that mediated by HBX through NF-κB pathway. This finding provides a critical insight into the mechanism of hepatocyte apoptosis mediated by HBX in HBV infection.

Xanthohumol inhibits Notch signaling and induces apoptosis in hepatocellular carcinoma

Despite improvement in therapeutic strategies, median survival in advanced hepatocellular carcinoma (HCC) remains less than one year. Therefore, molecularly targeted compounds with less toxic profiles are needed. Xanthohumol (XN), a prenylated chalcone has been shown to have anti-proliferative effects in various cancers types in vitro. XN treatment in healthy mice and humans yielded favorable pharmacokinetics and bioavailability. Therefore, we determined to study the effects of XN and understand the mechanism of its action in HCC. The effects of XN on a panel of HCC cell lines were assessed for cell viability, colony forming ability, and cellular proliferation. Cell lysates were analyzed for pro-apoptotic (c-PARP and cleaved caspase-3) and anti-apoptotic markers (survivin, cyclin D1, and Mcl-1). XN concentrations of 5μM and above significantly reduced the cell viability, colony forming ability and also confluency of all four HCC cell lines studied. Furthermore, growth suppression due to apoptosis was evidenced by increased expression of pro-apoptotic and reduced expression of anti-apoptotic proteins. Importantly, XN treatment inhibited the Notch signaling pathway as evidenced by the decrease in the expression of Notch1 and HES-1 proteins. Ectopic expression of Notch1 in HCC cells reverses the anti-proliferative effect of XN as evidenced by reduced growth suppression compared to control. Taken together these results suggested that XN mediated growth suppression is appeared to be mediated by the inhibition of the Notch signaling pathway. Therefore, our findings warrants further studies on XN as a potential agent for the treatment for HCC.

Influence of overexpression of hepatitis B virus X gene on proliferation and migration of hepatoma cells

AIM: To explore the influence of overexpression of hepatitis B virus X (HBX) on the proliferation and migration of hepatoma cells.

METHODS: Human hepatic carcinoma cell line Huh7 was cultured and infected with a recombinant adenovirus vector expressing HBX to establish an Huh7-HBX cell line. Colony forming assay, MTS assay and crystal violet staining were performed to assess cell proliferation. Cell migration assay was also performed.

RESULTS: The Huh7-HBX cell line was established successfully. HBX overexpression could promote cell proliferation. The number of cell colonies formed for Huh7-HBX cells was significantly higher than that for Huh7 cells (P < 0.05). Restoration of secreted frizzled-related protein 1 (SFRP1) and SFRP5 expression or knockdown of DNA methyltransferase 1 (Dnmt1) could significantly inhibit liver cancer cell proliferation and migration (P < 0.05).

CONCLUSION: Overexpression of HBX significantly inhibits the proliferation and migration of hepatoma cells.

Notch4 promotes gastric cancer growth through activation of Wnt1/β-catenin signaling

Gastric cancer (GC) is one of the most common cancers and lethal malignancies in the world. Discovering novel biomarkers that correlate with GC may provide opportunities to reduce the severity of GC. As one of Notch receptor family members in mammals, Notch4 plays an important role in carcinogenesis of several tumors. However, the precise function and mechanism of Notch4 in GC remain undefined. To address this question, we investigated whether Notch4 could be involved in GC progression. We found that Notch4 was activated by overexpressing exogenous intracellular domain of Notch4 (ICN4), and Notch4 activation promoted GC growth in vitro and in vivo, while Notch4 inhibition using ICN4 siRNA had opposite effects. In addition, Notch4 activation induced expression and activation of Wnt1, β-catenin and downstream target genes, c-Myc and cyclin D1, in GC cells, while Notch4 inhibition had opposite effects. Moreover, β-catenin depletion by siRNA attenuated cell proliferation induced by Notch4 activation. Therefore, our results revealed that Notch4 activates Wnt1/β-catenin signaling to regulate GC growth.