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Expression and Functional Significance of Twist1 in Hepatocellular Carcinoma: Its Role in Vasculogenic Mimicry

The up‐regulation and nuclear relocation of epithelial‐mesenchymal transition (EMT) regulator Twist1 have been implicated in the tumor invasion and metastasis of human hepatocellular carcinoma (HCC). The term vasculogenic mimicry (VM) refers to the unique capability of aggressive tumor cells to mimic the pattern of embryonic vasculogenic networks. However, the relationship between Twist1 and VM formation is not clear. In this study, we explored HCC as a VM and EMT model in order to investigate the role of Twist1 in VM formation. We first examined the expression of Twist1 in human HCC samples and cell lines and found that Twist1 was frequently overexpressed in the nuclear relocation occurring in VM‐positive HCCs (13/18 [72%]). Twist1 nuclear expression was likewise significantly associated with VM formation. Clinicopathological analysis revealed that both VM and Twist1 nuclear expressions present shorter survival durations than those without expression. We consistently demonstrated that an overexpression of Twist1 significantly enhanced cell motility, invasiveness, and VM formation in an HepG2 cell. Conversely, a knockdown of Twist1 by the short hairpin RNA approach remarkably reduced Bel7402 cell migration, invasion, and VM formation. Using chromatin immunoprecipitation, we also showed that Twist1 binds to the vascular endothelial (VE)‐cadherin promoter and enhances its activity in a transactivation assay. Conclusion: The results of this study indicate that Twist1 induces HCC cell plasticity in VM cells more through the suppression of E‐cadherin expression and the induction of VE‐cadherin up‐regulation than through the VM pattern in vivo and in a three‐dimensional in vitro system. Our findings also demonstrate a novel cogitation in cancer stem‐like cell differentiation and that related molecular pathways may be used as novel therapeutic targets for the inhibition of HCC angiogenesis and metastasis. (HEPATOLOGY 2009.)

Promotion of tumor cell metastasis and vasculogenic mimicry by way of transcription coactivation by Bcl-2 and Twist1: a study of hepatocellular carcinoma.

The antiapoptotic protein Bcl‐2 plays multiple roles in apoptosis, immunity, and autophagy. Its expression in tumors correlates with tumor grade and malignancy. The recapitulation of the normal developmental process of epithelial‐mesenchymal transition (EMT) contributes to tumor cell plasticity. This process is also a characteristic of metastatic cells and vasculogenic mimicry. In the present study we report functional and structural interactions between Bcl‐2 and the EMT‐regulating transcription factor Twist1 and the relationship with metastasis and vascular mimicry. Bcl‐2 and Twist1 are coexpressed under hypoxia conditions. The Bcl‐2 can bind to Twist1 in vivo and in vitro. This interaction involves basic helix‐loop‐helix DNA binding domain within Twist1 and through two separate domains within Bcl‐2 protein. Formation of the Bcl‐2/Twist1 complex facilitates the nuclear transport of Twist1 and leads to transcriptional activation of wide ranges of genes that can increase the tumor cell plasticity, metastasis, and vasculogenic mimicry. Finally, nuclear expression of Bcl‐2 and Twist1 is correlated with poor survival of these patients in a cohort of 97 cases of human hepatocellular carcinoma. Conclusion: The results describe a novel function of Bcl‐2 in EMT induction, provide insight into tumor progression, and implicate the Bcl‐2/Twist1 complex as a potential target for developing chemotherapeutics. (HEPATOLOGY 2011;)

Promotion of hepatocellular carcinoma metastasis through matrix metalloproteinase activation by epithelial-mesenchymal transition regulator Twist1.

E‐cadherin loss is a key biological mechanism in tumour invasion. As a main regulator of epithelial‐mesenchymal transition (EMT) mechanism‐mediated invasion and metastasis, Twist1 plays an important role through its regulation of E‐cadherin expression. However, whether or not Twist2 has the same function in tumour metastasis remains unclear. The purpose of this study is to investigate the expressions and different roles of Twist1 and Twist2 in human hepatocellular carcinoma (HCC). The expressions of Twist1 and Twist2 in HCC tissue were evaluated by immunohistochemical staining. The role of Twist1 and Twist2 in invasiveness was also evaluated in vitro by using HCC cell lines. Twist1 nuclear overexpression is found to be correlated with HCC metastasis, and its expression is negatively correlated with E‐cadherin expression in human tissue. Twist2, a Twist1 homology protein, only expresses in the cytoplasm and shows no significant correlation with HCC metastasis. By ectopic transfection of Twist1 and Twist2 into the HCC cells, HepG2 and PLC, Twist1 is able to down‐regulate E‐cadherin expression and promote matrix metalloproteinase (MMP) activation, specifically in MMP2 and MMP9. In functional assays, Twist1 is found to promote invasion in HepG2 and PLC cells, but the invasion ability of the groups is not affected Twist2. Our findings indicate that Twist1 induces HCC invasion via increased activity in MMPs, leading to poor clinical prognoses. The results of this study also demonstrate a novel cogitation in Twist2, which has no effect on HCC invasion and metastasis. Twist1 may contribute to HCC invasion and metastasis and may be used as a novel therapeutic target for the inhibition of HCC metastasis.

Slug promoted vasculogenic mimicry in hepatocellular carcinoma.

Vasculogenic mimicry (VM) refers to the unique capability of aggressive tumour cells to mimic the pattern of embryonic vasculogenic networks. Epithelial–mesenchymal transition (EMT) regulator slug have been implicated in the tumour invasion and metastasis of human hepatocellular carcinoma (HCC). However, the relationship between slug and VM formation is not clear. In the study, we demonstrated that slug expression was associated with EMT and cancer stem cell (CSCs) phenotype in HCC patients. Importantly, slug showed statistically correlation with VM formation. We consistently demonstrated that an overexpression of slug in HCC cells significantly increased CSCs subpopulation that was obvious by the increased clone forming efficiency in soft agar and by flowcytometry analysis. Meantime, the VM formation and VM mediator overexpression were also induced by slug induction. Finally, slug overexpression lead to the maintenance of CSCs phenotype and VM formation was demonstrated in vivo. Therefore, the results of this study indicate that slug induced the increase and maintenance of CSCs subpopulation and contributed to VM formation eventually. The related molecular pathways may be used as novel therapeutic targets for the inhibition of HCC angiogenesis and metastasis.

Hypoxia-induced vasculogenic mimicry formation via VE-cadherin regulation by Bcl-2

Vasculogenic mimicry (VM) refers to the unique ability of highly aggressive tumor cells to mimic the pattern of embryonic vasculogenic networks. Hypoxia plays a pivotal role in the formation of VM. Hypoxia-induced Bcl-2 overexpression is observed in many types of tumors including melanoma, in which it is associated with tumorigenicity and angiogenesis. VE-cadherin, the major endothelial adhesion molecule controlling cellular junctions and blood vessel formation, is also overexpressed in melanoma. Despite these connections, whether hypoxia induces VM formation via VE-cadherin regulation by Bcl-2 is not confirmed. We used human melanoma cells to upregulate or knockdown the expression of Bcl-2 to investigate the possible molecular mechanism of VM formation under hypoxia. Bcl-2 overexpression increased VE-cadherin expression and VM formation under normoxia, whereas Bcl-2 siRNA significantly decreased VE-cadherin expression and VM formation under hypoxia. We then demonstrated that Bcl-2 regulated VE-cadherin transcription activity by Western blot, three-dimensional cultures, reporter gene assay, and clinical analysis. Therefore, Bcl-2-dependent VE-cadherin overexpression may be an important mechanism by which hypoxia induces VM.

Basal caspase-3 activity promotes migration, invasion, and vasculogenic mimicry formation of melanoma cells.

Melanoma is the least common but most serious form of skin cancer. The leading cause of death in melanoma patients is widespread metastasis caused by increased cell motility and a rich blood supply for tumor cells. A unique form of microcirculation called vasculogenic mimicry, which efficiently supplies blood to tumor cells, has been reported recently. Apoptosis-related protein performs a nonapoptotic function to promote migration and invasion of tumor cells. This study focuses on the nonapoptotic role of caspase-3 in melanoma and its effects on the migration, invasion, and vasculogenic mimicry formation of melanoma cells. Human melanoma samples were used to detect active caspase-3 expression and determine its relationship with clinicopathologic parameters. In addition, a human melanoma A375 cell line was used to determine the role of caspase-3 in migration and invasion using z-DEVD-fmk, a selective caspase-3 inhibitor, to inhibit caspase-3 activity. The findings suggest that active caspase-3 is expressed in nonapoptotic melanoma cells and is related to metastasis and vasculogenic mimicry formation in patients with melanoma. Low doses of caspase-3 inhibitor reduced caspase-3 activity without affecting cell apoptosis. Inhibition of caspase-3 activity using low-dose z-DEVD-fmk decreased the migration, invasion, and vasculogenic mimicry formation of melanoma cells in vitro. Similarly, downregulation of caspase-3 by specific small interfering RNA also inhibited the migratory, invasive, and tube-forming potential of melanoma cells. The caspase-3-mediated promotion of melanoma cell motility may be because of the cleavage of matrix metalloproteinase-2.

The role of Twist1 in hepatocellular carcinoma angiogenesis: a clinical study

The epithelial-mesenchymal transition regulator Twist1 has been implicated in tumor invasion, metastasis, and vasculogenic mimicry formation of human hepatocellular carcinoma. However, the relationship between Twist1 expression and endothelium-dependent angiogenesis is not clear. In this study, to investigate the role of Twist1 in hepatocellular carcinoma angiogenesis, we measured the microvessel density by CD31 immunohistochemistry stain and explored the microvessel density as an angiogenesis indicator. The microvessel density in paraffin sections from 97 patients was correlated with Twist1 expression up-regulation. Nuclear relocation was also identified based on immunohistochemistry stain, presenting a significant clinical pattern in hepatocellular carcinoma metastasis and prognosis. Twist1 expression, which is both located in the cytoplasm and relocated into the nucleus, was associated with matrix metalloproteinase 9 up-regulation; matrix metalloproteinase 2 did not appear to present these effects in hepatocellular carcinoma. An assessment of microvessel density could provide an estimate of the degree of angiogenic activity in tissues, as well as its association with Twist1 up-regulated expression. To the best of our knowledge, not only is Twist1 related to metastasis by tumor cells, but vasculogenic mimicry is also significantly related to microvessel density; this process is also associated with matrix metalloproteinase 9 up-regulated expression. This work provides a better understanding of the role of Twist1 in hepatocellular carcinoma angiogenesis and metastasis, suggesting that our findings could represent tumor cell epithelial-mesenchymal transition and endothelium-dependent angiogenesis, as can be seen in hepatocellular carcinoma.

Dickkopf-1-promoted vasculogenic mimicry in non-small cell lung cancer is associated with EMT and development of a cancer stem-like cell phenotype

To characterize the contributions of Dickkopf‐1 (DKK1) towards the induction of vasculogenic mimicry (VM) in non‐small cell lung cancer (NSCLC), we evaluated cohorts of primary tumours, performed in vitro functional studies and generated xenograft mouse models. Vasculogenic mimicry was observed in 28 of 205 NSCLC tumours, while DKK1 was detected in 133 cases. Notably, DKK1 was positively associated with VM. Statistical analysis showed that VM and DKK1 were both related to aggressive clinical course and thus were indicators of a poor prognosis. Moreover, expression of epithelial‐mesenchymal transition (EMT)‐related proteins (vimentin, Slug, and Twist), cancer stem‐like cell (CSC)‐related proteins (nestin and CD44), VM‐related proteins (MMP2, MMP9, and vascular endothelial‐cadherin), and β‐catenin‐nu were all elevated in VM‐positive and DKK1‐positive tumours, whereas the epithelial marker (E‐cadherin) was reduced in the VM‐positive and DKK1‐positive groups. Non‐small cell lung cancer cell lines with overexpressed or silenced DKK1 highlighted its role in the restoration of mesenchymal phenotypes and development of CSC characteristics. Moreover, DKK1 significantly promotes NSCLC tumour cells to migrate, invade and proliferate. In vivo animal studies demonstrated that DKK1 enhances the growth of transplanted human tumours cells, as well as increased VM formation, mesenthymal phenotypes and CSC properties. Our results suggest that DKK1 can promote VM formation via induction of the expression of EMT and CSC‐related proteins. As such, we feel that DKK1 may represent a novel target of NSCLC therapy.

Slug promotes hepatocellular cancer cell progression by increasing sox2 and nanog expression

Transcription factor Slug plays an important role in the tumor invasion and metastasis of human hepatocellular carcinoma (HCC). This study aimed to explore the mechanism involved in the promotion of HCC progression by Slug. In the precent study, we demonstrated that Slug expression was significantly associated with metastasis and shorter survival time of HCC patients. Using ChIP-on-chip and microarray analysis, we identified the molecular profile of Slug downstream targets in HCC cells with Slug overexpression. The Wnt, Notch and Hedgehog pathways were identified to promote pluripotency maintaining overexpression factors sox2 and nanog. Importantly, Slug showed a close relationship with sox2 and nanog expression in HCC patients and in HCC xenografts in vivo. Notably, the DNA damaging reagent hydroxyurea had no effect on Slug, sox2 and nanog expression in HCC cells with Slug overexpression; however knockdown of Slug by the short hairpin RNA approach markedly reduced sox2 and nanog expression and inhibited HCC cell migration in vitro. The results of this study indicate that Slug promotes progression of HCC by promoting sox2 and nanog overexpression. The related molecular pathways may be used as novel therapeutic targets for HCC.

HMGA2 promotes vasculogenic mimicry and tumor aggressiveness by upregulating Twist1 in gastric carcinoma

High mobility group protein A2 (HMGA2) is a transcription factor that plays an important role in the invasion and metastasis of gastric carcinoma (GC). The term vasculogenic mimicry (VM) refers to the unique ability of aggressive tumour cells to mimic the pattern of embryonic vasculogenic networks. However, the relationship between HMGA2 and VM formation remains unclear. In the present study, we examined concomitant HMGA2 expression and VM in 228 human GC samples and 4 GC cell lines. Our data indicate that HMGA2 is not only significantly associated with VM formation but also influences the prognosis of patients with gastric carcinoma. Overexpression of HMGA2 significantly increased cell motility, invasiveness, and VM formation both in vitro and in vivo. A luciferase reporter assay, Co-IP and ChIP demonstrated that HMGA2 induced the expression of Twist1 and VE-cadherin by binding to the Twist1 promoter. Moreover, we observed a decrease in VE-cadherin following Twist1 knockdown in cells overexpressing HMGA2. This study indicates that HMGA2 promotes VM in GC via Twist1-VE-cadherin signalling and influences the prognosis of patients with GC.