Notch1 binds and induces degradation of Snail in hepatocellular carcinoma

Immunotherapy and the Combination with Targeted Therapies for Advanced Hepatocellular Carcinoma

One of the most important abilities of a tumor is to establish a state of immunosuppression inside the tumor microenvironment. This is made possible through numerous mechanisms of tumor immune escape that have been identified in experimental studies during the last decades. In addition, the hepatic microenvironment is commonly oriented towards a state of immune tolerance because the liver receives blood from the hepatic arteries and portal veins containing a variety of endogenous antigens. Therefore, the hepatic microenvironment establishes an autoimmune tolerance, preventing an autoimmune reaction in the liver. On this basis, hepatic tumor cells may escape the immune system, avoiding being recognized and destroyed by immune cells. Moreover, since the etiology of Hepatocellular Carcinoma (HCC) is often related to cirrhosis, and hepatitis B or C, this tumor develops in the context of chronic inflammation. Thus, the HCC microenvironment is characterized by important immune cell infiltration. Given these data and the poor prognosis of advanced HCC, different immunotherapeutic strategies have been developed and evaluated for these patients. In this review, we describe all the clinical applications of immunotherapy for advanced HCC, from the drugs that have already been approved to the ongoing clinical trials.

Autophagy-mediated degradation of NOTCH1 intracellular domain controls the epithelial to mesenchymal transition and cancer metastasis

Backgound

Autophagy controls levels of cellular components during normal and stress conditions; thus, it is a pivotal process for the maintenance of cell homeostasis. In cancer, autophagy protects cells from cancerous transformations that can result from genomic instability induced by reactive oxygen species or other damaged components, but it can also promote cancer survival by providing essential nutrients during the metabolic stress condition of cancer progression. However, the molecular mechanism underlying autophagy-dependent regulation of the epithelial to mesenchymal transition (EMT) and metastasis is still elusive.

Methods

The intracellular level of NOTCH1 intracellular domain (NICD) in several cancer cells was studied under starvation, treatment with chloroquine or ATG7-knockdown. The autophagy activity in these cells was assessed by immunocytochemistry and molecular analyses. Cancer cell migration and invasion under modulation of autophagy were determined by in vitro scratch and Matrigel assays.

Results

In the study, autophagy activation stimulated degradation of NICD, a key transcriptional regulator of the EMT and cancer metastasis. We also found that NICD binds directly to LC3 and that the NICD/LC3 complex associates with SNAI1 and sequestosome 1 (SQSTM1)/p62 proteins. Furthermore, the ATG7 knockdown significantly inhibited degradation of NICD under starvation independent of SQSTM1-associated proteasomal degradation. In addition, NICD degradation by autophagy associated with the cellular level of SNAI1. Indeed, autophagy inhibited nuclear translocation of NICD protein and consequently decreased the transcriptional activity of its target genes. Autophagy activation substantially suppressed in vitro cancer cell migration and invasion. We also observed that NICD and SNAI1 levels in tissues from human cervical and lung cancer patients correlated inversely with expression of autophagy-related proteins.

Conclusions

These findings suggest that the cellular level of NICD is regulated by autophagy during cancer progression and that targeting autophagy-dependent NICD/SNAI1 degradation could be a strategy for the development of cancer therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00752-3.

CCN3 Signaling Is Differently Regulated in Placental Diseases Preeclampsia and Abnormally Invasive Placenta

OBJECTIVES

An adequate development of the placenta includes trophoblast differentiation with the processes of trophoblast migration, invasion, cellular senescence and apoptosis which are all crucial to establishing a successful pregnancy. Altered placental development and function lead to placental diseases such as preeclampsia (PE) which is mainly characterized by insufficient trophoblast invasion and abnormally invasive placenta (AIP) disorders (Placenta accreta, increta, or percreta) which are characterized by excessive trophoblast invasion. Both of them will cause maternal and fetal morbidity/mortality. However, the etiology of these diseases is still unclear. Our previous study has shown that the matricellular protein nephroblastoma overexpressed (NOV, CCN3) induces G0/G1 cell cycle arrest, drives trophoblast cells into senescence and activates FAK and Akt kinases resulting in reduced cell proliferation and enhanced migration capability of the human trophoblast cell line SGHPL-5. The present study focuses on whether CCN3 can alter cell cycle-regulated pathways associated with trophoblast senescence and invasion activity in pathological versus gestational age-matched control placentas.

METHODS

Cell cycle regulator proteins were investigated by immunoblotting and qPCR. For localization of CCN3, p16, p21, and Cyclin D1 proteins, co-immunohistochemistry was performed.

RESULTS

In early-onset PE placentas, CCN3 was expressed at a significantly lower level compared to gestational age-matched controls. The decrease of CCN3 level is associated with an increase in p53, Cyclin E1 and pRb protein expression, whereas the level of cleaved Notch-1, p21, Cyclin D1, pFAK, pAKT, and pmTOR protein decreased. In term AIP placentas, the expression of CCN3 was significantly increased compared to matched term controls. This increase was correlated to an increase in p53, p16, p21, Cyclin D1, cleaved Notch-1, pFAK, pAkt, and pmTOR whereas pRb was significantly decreased. However, in late PE and early AIP placentas, no significant differences in CCN3, p16, p21, Cyclin D1, p53, and cleaved Notch-1 expression were found when matched to appropriate controls.

CONCLUSIONS

CCN3 expression levels are correlated to markers of cell cycle arrest oppositely in PE and AIP by activating the FAK/AKT pathway in AIP or down-regulating in PE. This may be one mechanism to explain the different pathological features of placental diseases, PE and AIP.

Notch and breast cancer metastasis: Current knowledge, new sights and targeted therapy

Breast cancer is the most common type of invasive cancer in females and metastasis is one of the major causes of breast cancer-associated mortality. Following detachment from the primary site, disseminated tumor cells (DTCs) enter the bloodstream and establish secondary colonies during the metastatic process. An increasing amount of studies have elucidated the importance of Notch signaling in breast cancer metastasis; therefore, the present review focuses on the mechanisms by which Notch contributes to the occurrence of breast cancer DTCs, increases their motility, establishes interactions with the tumor microenvironment, protects DTCs from host surveillance and finally facilitates secondary colonization. Identification of the underlying mechanisms of Notch-associated breast cancer metastasis will provide additional insights that may contribute towards the development of novel Notch-targeted therapeutic strategies, which may aid in reducing metastasis, culminating in an improved patient prognosis.

Salidroside suppresses the metastasis of hepatocellular carcinoma cells by inhibiting the activation of the Notch1 signaling pathway

Salidroside (SDS) is a phenylpropanoid glycoside isolated from Rhodiola rosea L. It exhibits multiple pharmacological properties in clinical medicine and has been commonly used in traditional Chinese medicine. The present study investigated the inhibitory effects of SDS on tumor invasion and migration, and the expression of metastasis‑related genes in highly metastatic hepatocellular carcinoma (HCC) cells (MHCC97H) in vitro. The underlying mechanisms of SDS on the tumor metastasis were also explored. SDS was found to significantly reduce wound closure areas and inhibit cell migration. In addition, SDS markedly inhibited the invasion of these cells into Matrigel‑coated membranes. SDS markedly downregulated the expression of Notch1, Snail, COX‑2, MMP‑2, MMP‑9 genes and upregulated the expression of E‑cadherin in a dose‑dependent manner. Furthermore, SDS inhibited the expression of the Notch signaling target genes, Hey1, Hes1 and Hes5. On the whole, the findings of this study suggest that SDS inhibits HCC cell metastasis by modulating the activity of the Notch1 signaling pathway.

p73 induction by Abrus agglutinin facilitates Snail ubiquitination to inhibit epithelial to mesenchymal transition in oral cancer

BACKGROUND

Epithelial-to-mesenchymal transition (EMT), a key step in oral cancer progression, is associated with invasion, metastasis, and therapy resistance, thus targeting the EMT represents a critical therapeutic strategy for the treatment of oral cancer metastasis. Our previous study showed that Abrus agglutinin (AGG), a plant lectin, induces both intrinsic and extrinsic apoptosis to activate the tumor inhibitory mechanism.

OBJECTIVE

This study aimed to investigate the role of AGG in modulating invasiveness and stemness through EMT inhibition for the development of antineoplastic agents against oral cancer.

METHODS

The EMT- and stemness-related proteins were studied in oral cancer cells using Western blot analysis and fluorescence microscopy. The potential mechanisms of Snail downregulation through p73 activation in FaDu cells were evaluated using Western blot analysis, immunoprecipitation, confocal microscopy, and molecular docking analysis. Immunohistochemical staining of the tumor samples of AGG-treated FaDu-xenografted nude mice was performed.

RESULTS

At the molecular level, AGG-induced p73 suppressed Snail expression, leading to EMT inhibition in FaDu cells. Notably, AGG promoted the translocation of Snail from the nucleus to the cytoplasm in FaDu cells and triggered its degradation through ubiquitination. In this setting, AGG inhibited the interaction between Snail and p73 in FaDu cells, resulting in p73 activation and EMT inhibition. Moreover, in epidermal growth factor (EGF)-stimulated FaDu cells, AGG abolished the upregulation of extracellular signal-regulated kinase (ERK)1/2 that plays a pivotal role in the upregulation of Snail to regulate the EMT phenotypes. In immunohistochemistry analysis, FaDu xenografts from AGG-treated mice showed decreased expression of Snail, SOX2, and vimentin and increased expression of p73 and E-cadherin compared with the control group, confirming EMT inhibition as part of its anticancer efficacy against oral cancer.

CONCLUSION

In summary, AGG stimulates p73 in restricting EGF-induced EMT, invasiveness, and stemness by inhibiting the ERK/Snail pathway to facilitate the development of alternative therapeutics for oral cancer.

Molecular and proteomic insight into Notch1 characterization in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) ranks fifth in frequency worldwide amongst all human cancers causing one million deaths annually. Despite many promising treatment options, long-term prognosis remains dismal for the majority of patients who develop recurrence or present with advanced disease. Notch signaling is an evolutionarily conserved pathway crucial for the development and homeostasis of many organs including liver. Herein we showed that aberrant Notch1 is linked to HCC development, tumor recurrence and invasion, which might be mediated, at least in part, through the Notch1-E-Cadherin pathway. Collectively, these findings suggest that targeting Notch1 has important therapeutic value in hepatocellular carcinoma. In this regard, comparative analysis of the secretome of HepG2 and HepG2 Notch1 depleted cells identified novel secreted proteins related to Notch1 expression. Soluble E-Cadherin (sE-Cad) and Thrombospondin-1 (Thbs1) were further validated in human serum as potential biomarkers to predict response to Notch1 inhibitors for a tailored individualized therapy.

Targeting Notch3 in Hepatocellular Carcinoma: Molecular Mechanisms and Therapeutic Perspectives

The Notch signaling pathway is a very conserved system that controls embryonic cell fate decisions and the maintenance of adult stem cells through cell to cell communication. Accumulating evidence support the relevance of Notch signaling in different human diseases and it is one of the most commonly activated signaling pathways in cancer. This review focuses mainly on the role of Notch3 signaling in hepatocellular carcinoma and its potential therapeutic applications against this malignancy. In this regard, the crosstalk between Notch and p53 may play an important role.

NOTCH receptors in gastric and other gastrointestinal cancers: oncogenes or tumor suppressors?

Gastric cancer (GC) ranks the most common cancer types and is one of the leading causes of cancer-related death. Due to delayed diagnosis and high metastatic frequency, 5-year survival rate of GC is rather low. It is a complex disease resulting from the interaction between environmental factors and host genetic alterations that deregulate multiple signaling pathways. The Notch signaling pathway, a highly conserved system in the regulation of the fate in several cell types, plays a pivotal role in cell differentiation, survival and proliferation. Notch is also one of the most commonly activated signaling pathways in tumors and its aberrant activation plays a key role in cancer advancement. Whether Notch cascade exerts oncogenic or tumor suppressive function in different cancer types depends on the cellular context. Mammals have four NOTCH receptors that modulate Notch pathway activity. In this review, we provide a comprehensive summary on the functional role of NOTCH receptors in gastric and other gastrointestinal cancers. Increasing knowledge of NOTCH receptors in gastrointestinal cancers will help us recognize the underlying mechanisms of Notch signaling and develop novel therapeutic strategies for GC.

Escargot and Scratch regulate neural commitment by antagonizing Notch activity in Drosophila sensory organs

During Notch (N)-mediated binary cell fate decisions, cells adopt two different fates according to the levels of N pathway activation: an Noff-dependent or an Non-dependent fate. How cells maintain these N activity levels over time remains largely unknown. We address this question in the cell lineage that gives rise to the Drosophila mechanosensory organs. In this lineage a primary precursor cell undergoes a stereotyped sequence of oriented asymmetric cell divisions and transits through two neural precursor states before acquiring a neuron identity. Using a combination of genetic and cell biology strategies, we show that Escargot and Scratch, two transcription factors belonging to the Snail superfamily, maintain Noff neural commitment by directly blocking the transcription of N target genes. We propose that Snail factors act by displacing proneural transcription activators from DNA binding sites. As such, Snail factors maintain the Noff state in neural precursor cells by buffering any ectopic variation in the level of N activity. Since Escargot and Scratch orthologs are present in other precursor cells, our findings are fundamental for understanding precursor cell fate acquisition in other systems.

Snai2 and Snai3 transcriptionally regulate cellular fitness and functionality of T cell lineages through distinct gene programs

T lymphocytes are essential contributors to the adaptive immune system and consist of multiple lineages that serve various effector and regulatory roles. As such, precise control of gene expression is essential to the proper development and function of these cells. Previously, we identified Snai2 and Snai3 as being essential regulators of immune tolerance partly due to the impaired function of CD4(+) regulatory T cells in Snai2/3 conditional double knockout mice. Here we extend those previous findings using a bone marrow transplantation model to provide an environmentally unbiased view of the molecular changes imparted onto various T lymphocyte populations once Snai2 and Snai3 are deleted. The data presented here demonstrate that Snai2 and Snai3 transcriptionally regulate the cellular fitness and functionality of not only CD4(+) regulatory T cells but effector CD8(α+) and CD4(+) conventional T cells as well. This is achieved through the modulation of gene sets unique to each cell type and includes transcriptional targets relevant to the survival and function of each T cell lineage. As such, Snai2 and Snai3 are essential regulators of T cell immunobiology.

CD24 promotes HCC progression via triggering Notch-related EMT and modulation of tumor microenvironment

CD24 is known as a cell surface molecule in hematopoiesis and also described as a diagnostic marker for tumors. Previous studies suggested the important role of CD24 in hepatocellular carcinoma (HCC) pathogenesis. However, precise functions of CD24 in HCC are still unknown. Here, we found that CD24 is highly expressed in HCC both in mRNA and protein levels. Further, the epithelial-mesenchymal transition (EMT) and Notch1 signaling activations mediated by CD24 were elucidated as potential mechanisms of HCC promotion in Hepa1-6/Hepa1-6-CD24 cell models. Additionally, possible systemic immune reaction was explored through immune cells and Hepa1-6/Hepa1-6-CD24 cell co-culture. We demonstrated that the EMT process of HCC cell was effectively induced by CD24; also, the tumor immune microenvironment was changed by facilitating Notch-related EMT in vivo. These results reveal the underlying link between the HCC processes mediated by CD24. Moreover, as a clear tumor promoter, CD24 is considered a potential new target for HCC treatment.

MicroRNAs in skin tissue engineering

35.2 million annual cases in the U.S. require clinical intervention for major skin loss. To meet this demand, the field of skin tissue engineering has grown rapidly over the past 40 years. Traditionally, skin tissue engineering relies on the "cell-scaffold-signal" approach, whereby isolated cells are formulated into a three-dimensional substrate matrix, or scaffold, and exposed to the proper molecular, physical, and/or electrical signals to encourage growth and differentiation. However, clinically available bioengineered skin equivalents (BSEs) suffer from a number of drawbacks, including time required to generate autologous BSEs, poor allogeneic BSE survival, and physical limitations such as mass transfer issues. Additionally, different types of skin wounds require different BSE designs. MicroRNA has recently emerged as a new and exciting field of RNA interference that can overcome the barriers of BSE design. MicroRNA can regulate cellular behavior, change the bioactive milieu of the skin, and be delivered to skin tissue in a number of ways. While it is still in its infancy, the use of microRNAs in skin tissue engineering offers the opportunity to both enhance and expand a field for which there is still a vast unmet clinical need. Here we give a review of skin tissue engineering, focusing on the important cellular processes, bioactive mediators, and scaffolds. We further discuss potential microRNA targets for each individual component, and we conclude with possible future applications.

Notch1 increases Snail expression under high reactive oxygen species conditions in hepatocellular carcinoma cells

Notch1 and reactive oxygen species (ROS) modulate important pathways associated with tumor development and progression. Notably, Notch1 expression is upregulated in 41.8% of hepatocellular carcinoma (HCC) patients and ROS levels increases as HCC progresses from Grade I to Grade III. It has been established that Notch1 and ROS modulate Snail expression in malignant tumors; however, the mechanism regulating Snail protein expression is not yet known. In this study, we observed that Notch1 and ROS cooperatively increase the levels of Snail protein in Huh7 (hepatoma) cells. On its own, signaling through Notch1 increases transcription of Snail without changing protein levels. In contrast, the combined activation of the Notch1 and ROS-induced phosphoinositide 3-kinase/Akt (PI3K/Akt) signaling pathways resulted in the high expression of Snail protein. This increase in Snail expression was associated with increased Huh7 cells invasiveness. Furthermore, we observed that correlation between Snail and Notch1 expression was the strongest in advanced grade HCC tissue. In conclusion, Notch1 and ROS-induced PI3K/Akt signals cooperatively increase Snail expression and may induce malignancy in HCC.

From fly wings to targeted cancer therapies: a centennial for notch signaling

Since Notch phenotypes in Drosophila melanogaster were first identified 100 years ago, Notch signaling has been extensively characterized as a regulator of cell-fate decisions in a variety of organisms and tissues. However, in the past 20 years, accumulating evidence has linked alterations in the Notch pathway to tumorigenesis. In this review, we discuss the protumorigenic and tumor-suppressive functions of Notch signaling, and dissect the molecular mechanisms that underlie these functions in hematopoietic cancers and solid tumors. Finally, we link these mechanisms and observations to possible therapeutic strategies targeting the Notch pathway in human cancers.

The roles of transforming growth factor-β, Wnt, Notch and hypoxia on liver progenitor cells in primary liver tumours (Review)

Primary liver tumours have a high incidence and mortality. The most important forms are hepatocellular carcinoma and intrahepatic cholangiocarcinoma, both can occur together in the mixed phenotype hepatocellular-cholangiocarcinoma. Liver progenitor cells (LPCs) are bipotential stem cells activated in case of severe liver damage and are capable of forming both cholangiocytes and hepatocytes. Possibly, alterations in Wnt, transforming growth factor-β, Notch and hypoxia pathways in these LPCs can cause them to give rise to cancer stem cells, capable of driving tumourigenesis. In this review, we summarize and discuss current knowledge on the role of these pathways in LPC activation and differentiation during hepatocarcinogenesis.

Common and complex Notch1 mutations in Chinese oral squamous cell carcinoma

PURPOSE

To determine Notch1 mutation status in oral squamous cell carcinoma (OSCC) from Chinese population and its potential clinical implications.

EXPERIMENTAL DESIGN

Surgically resected OSCC tissues from 51 Chinese patients and 13 head and neck squamous cell carcinoma (HNSCC) cell lines were sequenced for mutations in the entire coding regions of Notch1 and TP53 using a next-generation sequencing platform. Sequences of the genes were also determined in corresponding normal tissues from 46 of the 51 patients. Mutations and their association with clinical parameters were analyzed.

RESULTS

Six mutations in Notch1 and 11 mutations in TP53 coding regions were detected in 4 (31%) and 10 (77%) of the 13 HNSCC cell lines, respectively. Forty-two somatic Notch1 mutations, including 7 nonsense mutations and 11 mutations within the domain commonly harboring potential activating mutations in acute lymphoblastic leukemia, were detected in 22 (43%) of the 51 Chinese OSCC tumors. In comparison, 25 somatic TP53 mutations were observed in 21 (41%) of the 51 tumors. Patients whose tumors carried Notch1 mutation had significantly shorter overall and disease-free survivals (P = 0.004 and P = 0.001, respectively, by log-rank test) compared with those whose tumors carried no Notch1 mutation. Multivariate analysis showed that both Notch1 mutation and lymph node metastasis are independent prognostic factors in the patient population (P = 0.001). All 15 patients with both Notch1 mutation and nodal metastasis recurred or metastasized within 2 years after surgery.

CONCLUSIONS

Notch1 mutation is common in Chinese OSCC and associates with clinical outcomes. The complexity of the mutation spectrum warrants further investigation of Notch1 in Chinese patients with OSCC.

Architecture of a lymphomyeloid developmental switch controlled by PU.1, Notch and Gata3

Hematopoiesis is a classic system with which to study developmental potentials and to investigate gene regulatory networks that control choices among alternate lineages. T-cell progenitors seeding the thymus retain several lineage potentials. The transcription factor PU.1 is involved in the decision to become a T cell or a myeloid cell, and the developmental outcome of expressing PU.1 is dependent on exposure to Notch signaling. PU.1-expressing T-cell progenitors without Notch signaling often adopt a myeloid program, whereas those exposed to Notch signals remain in a T-lineage pathway. Here, we show that Notch signaling does not alter PU.1 transcriptional activity by degradation/alteration of PU.1 protein. Instead, Notch signaling protects against the downregulation of T-cell factors so that a T-cell transcriptional network is maintained. Using an early T-cell line, we describe two branches of this network. The first involves inhibition of E-proteins by PU.1 and the resulting inhibition of Notch signaling target genes. Effects of E-protein inhibition can be reversed by exposure to Notch signaling. The second network is dependent on the ability of PU.1 to inhibit important T-cell transcription factor genes such as Myb, Tcf7 and Gata3 in the absence of Notch signaling. We show that maintenance of Gata3 protein levels by Myb and Notch signaling is linked to the ability to retain T-cell identity in response to PU.1.

DDX3 loss by p53 inactivation promotes tumor malignancy via the MDM2/Slug/E-cadherin pathway and poor patient outcome in non-small-cell lung cancer

P53 inactivation by p53 mutation and E6 oncoprotein has a crucial role in human carcinogenesis. DDX3 has been shown to be a target of p53. In this study, we hypothesized that DDX3 loss by p53 inactivation may promote tumor malignancy and poor patients' outcome. Mechanically, DDX3 loss by p53 knockdown and E6 overexpression was observed in A549 lung cancer cells. Conversely, DDX3 expression was markedly elevated by wild-type (WT) p53 ectopic expression in p53-null H1299 cells, E6-knockdown TL-1 lung cancer and SiHa cervical cancer cells. Interestingly, DDX3 loss promotes soft-agar growth and invasive capability; however, both capabilities were suppressed by DDX3 overexpression. We next expected that DDX3 loss might result in Slug-suppressed E-cadherin expression via decreased MDM2-mediated Slug degradation. As expected, MDM2 transcription is suppressed by DDX3 loss via decreased SP1 binding activity to the MDM2 promoter. Consequently, Slug expression was elevated by the reduction of MDM2 because of DDX3 loss, and E-cadherin expression was suppressed by Slug. Consistent observations in the correlation of DDX3 loss with MDM2, Slug and E-cadherin were seen in lung tumors from lung cancer patients. In addition, patients with low-DDX3 tumors had poorer survival and relapse than patients with high-DDX3 tumors. In conclusion, we suggest that DDX3 loss by p53 inactivation via MDM2/Slug/E-cadherin pathway promotes tumor malignancy and poor patient outcome.

The down-regulation of Notch1 inhibits the invasion and migration of hepatocellular carcinoma cells by inactivating the cyclooxygenase-2/Snail/E-cadherin pathway in vitro

BACKGROUND

The Notch signaling pathway plays an important role in cancer, but the mechanism by which Notch1 participates in invasion and migration of hepatocellular carcinoma (HCC) cells is unclear.

AIMS

Our purpose is to confirm the anti-invasion and anti-migration effects of the down-regulation of Notch1 in HCC cells.

METHODS

The invasion and migration capacities of HCC cells were detected with Transwell cell culture chambers. The expressions of Notch1, Notch1 intracellular domain (N1ICD), E-cadherin, Snail, and cyclooxygenase-2 (COX-2) were analyzed by RT-PCR and/or western blotting. Notch1 and Snail were down-regulated by RNA interference, and COX-2 was inhibited by NS-398. Cell apoptosis was analyzed by MTT and flow cytometry.

RESULTS

In HCC cells, Snail, Notch1, and COX-2 were up-regulated, and E-cadherin was down-regulated in mRNA and/or protein levels. The down-regulation of Snail or Notch1 or the inhibition of COX-2, respectively, can increase the mRNA and protein expressions of E-cadherin and decrease the invasion and migration capabilities of HCC cell. Down-regulated Notch1 or inhibited COX-2 can reduce the mRNA and protein expressions of Snail. The down-regulation of Notch1 can also reduce the protein expression of COX-2. However, exogenous PGE2 can reverse the role of down-regulated Notch1. The results of MTT and flow cytometry showed that down-regulated Notch1 did not affect HCC cell viability.

CONCLUSIONS

Down-regulated Notch1 may be an effective approach to inactivating Snail/E-cadherin by regulating COX-2, which results in inhibiting the invasion and migration of HCC cells. The inhibitory effects of down-regulated Notch1 on cell invasion and migration were independent of apoptosis.

The significance of Notch1 compared with Notch3 in high metastasis and poor overall survival in hepatocellular carcinoma

BACKGROUND

The prognosis for patients with hepatocellular carcinoma (HCC) is poor, and the mechanisms underlying the development of HCC remain unclear. Notch1 and Notch3 may be involved in malignant transformation, although their roles remain unknown.

MATERIALS AND METHODS

HCC tissues were stained with anti-Notch1 or -Notch3 antibody. The migration and invasion capacities of the cells were measured with transwell cell culture chambers. RT-PCR was used to measure the expression of Notch1 and Notch3 mRNA. Additionally, western blot analysis was used to assess the protein expression of Notch1, Notch3, CD44v6, E-cadherin, matrix metalloproteinase-2 (MMP-2), MMP-9, and urokinase-type plasminogen activator (uPA). RNA interference was used to down-regulate the expression of Notch1 and Notch3. Cell viability was assessed using MTT.

RESULTS

Based on immunohistochemistry, high Notch1 expression was correlated with tumor size, tumor grade, metastasis, venous invasion and AJCC TNM stage. High Notch3 expression was only strongly correlated with metastasis, venous invasion and satellite lesions. Kaplan-Meier curves demonstrated that patients with high Notch1 or Notch3 expression were at a significantly increased risk for shortened survival time. In vitro, the down-regulation of Notch1 decreased the migration and invasion capacities of HCC cells by regulating CD44v6, E-cadherin, MMP-2, MMP-9, and uPA via the COX-2 and ERK1/2 pathways. Down-regulation of Notch3 only decreased the invasion capacity of HCC cells by regulating MMP-2 and MMP-9 via the ERK1/2 pathway.

CONCLUSIONS

Based on the migration and invasion of HCC, we hypothesize that targeting Notch1 may be more useful than Notch3 for designing novel preventive and therapeutic strategies for HCC in the near future.

Snail inhibits Notch1 intracellular domain mediated transcriptional activation via competing with MAML1

Notch1 intracellular domain (NICD) is the transcription factor which controls cell fate and differentiation in embryonic and tumor cells. Snail has a critical role which increases invasion and metastasis of cancer cell as a transcription factor and epigenetic regulator. Recently, we discovered NICD induced Snail degradation by direct binding interaction with Snail. In this experiment, we found that Snail suppressed transcriptional activity of the protein complex formed with NICD and RBPJk in nucleus. Moreover, Snail decreased transcription of NICD target genes via competing with MAML1, co-activator, in NICD complex. In conclusion, Snail inhibited NICD-mediated transcriptional activation of target genes by physical interaction with NICD.

Regulatory networks defining EMT during cancer initiation and progression

Epithelial to mesenchymal transition (EMT) is essential for driving plasticity during development, but is an unintentional behaviour of cells during cancer progression. The EMT-associated reprogramming of cells not only suggests that fundamental changes may occur to several regulatory networks but also that an intimate interplay exists between them. Disturbance of a controlled epithelial balance is triggered by altering several layers of regulation, including the transcriptional and translational machinery, expression of non-coding RNAs, alternative splicing and protein stability.

The Notch1/cyclooxygenase-2/Snail/E-cadherin pathway is associated with hypoxia-induced hepatocellular carcinoma cell invasion and migration

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide; however, the prognosis of HCC patients remains poor. This poor prognosis is mainly attributed to the high rate of intrahepatic and distant metastasis. HCC often occurs in a hypoxic environment and hypoxia can activate metastatic programs, ultimately leading to tumor recurrence or metastasis. Thus, the discovery and subsequent development of novel agents to block HCC invasion and migration are the primary objectives of hepatic cancer research. The Notch1 signaling pathway might be involved in hypoxia-induced carcinoma metastasis. However, the mechanisms by which Notch1 mediates cell metastasis, particularly in hepatocellular carcinoma, are not yet entirely clear. The results of the present study show that hypoxia increases the invasion and migration capacities of different HCC cells. Activation of the Notch1 signaling pathway contributes to hypoxia-induced invasion and migration in HCC cells. The activated Notch1 signaling pathway can regulate Snail/E-cadherin through cyclooxygenase-2 (COX-2) under hypoxic conditions. The above results suggest that the Notch1/COX-2/Snail/E-cadherin pathway is possibly associated with hypoxia-induced invasion and migration in HCC cells. Thus, targeting Notch1 may be useful for devising novel preventive and therapeutic strategies for HCC.

Functional genomic studies: insights into the pathogenesis of liver cancer

Liver cancer is the sixth-most-common cancer overall but the third-most-frequent cause of cancer death. Among primary liver cancers, hepatocellular carcinoma (HCC), the major histological subtype, is associated with multiple risk factors, including hepatitis B and C virus infection, alcohol consumption, obesity, and diet contamination. Although previous studies have revealed that certain genetic and epigenetic changes, such as TP53 and β-catenin mutations, occur in HCC cells, the pathogenesis of this cancer remains obscure. Functional genomic approaches-including genome-wide association studies, whole-genome and whole-exome sequencing, array-based comparative genomic hybridization, global DNA methylome mapping, and gene or noncoding RNA expression profiling-have recently been applied to HCC patients with different clinical features to uncover the genetic risk factors and underlying molecular mechanisms involved in this cancer's initiation and progression. The genome-wide analysis of germline and somatic genetic and epigenetic events facilitates understanding of the pathogenesis and molecular classification of liver cancer as well as the identification of novel diagnostic biomarkers and therapeutic targets for cancer.