Transforming growth factor-beta1 triggers hepatocellular carcinoma invasiveness via alpha3beta1 integrin

The inflammatory microenvironment in hepatocellular carcinoma: a pivotal role for tumor-associated macrophages

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human cancers worldwide. HCC is an example of inflammation-related cancer and represents a paradigm of the relation occurring between tumor microenvironment and tumor development. Tumor-associated macrophages (TAMs) are a major component of leukocyte infiltrate of tumors and play a pivotal role in tumor progression of inflammation-related cancer, including HCC. Several studies indicate that, in the tumor microenvironment, TAMs acquire an M2-polarized phenotype and promote angiogenesis, metastasis, and suppression of adaptive immunity through the expression of cytokines, chemokines, growth factors, and matrix metalloproteases. Indeed, an established M2 macrophage population has been associated with poor prognosis in HCC. The molecular links that connect cancer cells and TAMs are not completely known, but recent studies have demonstrated that NF-κB, STAT-3, and HIF-1 signaling pathways play key roles in this crosstalk. In this paper, we discuss the current knowledge about the role of TAMs in HCC development, highlighting the role of TAM-derived cytokines, chemokines, and growth factors in the initiation and progression of liver cancer and outlining the signaling pathways involved in the interplay between cancer cells and TAMs.

The Dual Role of TGFβ in Human Cancer: From Tumor Suppression to Cancer Metastasis

The transforming growth factor-beta (TGFβ) superfamily encompasses widespread and evolutionarily conserved polypeptide growth factors that regulate and orchestrate growth and differentiation in all cell types and tissues. While they regulate asymmetric cell division and cell fate determination during early development and embryogenesis, TGFβ family members play a major regulatory role in hormonal and immune responses, cell growth, cell death and cell immortalization, bone formation, tissue remodeling and repair, and erythropoiesis throughout adult life. The biological and physiological functions of TGFβ, the founding member of this family, and its receptors are of central importance to human diseases, particularly cancer. By regulating cell growth, death, and immortalization, TGFβ signaling pathways exert tumor suppressor effects in normal cells and early carcinomas. Thus, it is not surprising that a high number of human tumors arise due to mutations or deletions in the genes coding for the various TGFβ signaling components. As tumors develop and progress, these protective and cytostatic effects of TGFβ are often lost. TGFβ signaling then switches to promote cancer progression, invasion, and tumor metastasis. The molecular mechanisms underlying this dual role of TGFβ in human cancer will be discussed in depth in this paper, and it will highlight the challenge and importance of developing novel therapeutic strategies specifically aimed at blocking the prometastatic arm of the TGFβ signaling pathway without affecting its tumor suppressive effects.

Role of TGF-β1 and its receptors in malignant progression of hepatocellular carcinoma

Transforming growth factor-beta 1 (TGF-β1) is a cytokine which exerts a wide range of biological activities by initiating downstream signaling. As transmembrane receptors, TGFBRⅠ, TGFBRⅡ and TGFBRⅢ have been shown to play an important role in mediating TGF-β1 signal transduction. Owing to roles in promoting cell growth and development, alterations in TGF-β1 and its receptors may result in many diseases, especially tumors. Hepatocellular carcinoma (HCC) is a common malignant solid tumor with high risk of metastasis and recurrence and is associated with a high fatality. Recent studies point to a close relationship between hepatocellular carcinoma and the dysregulation of TGF-β1 signaling pathway. The changes in the levels of TGF-β1 and its receptors in tumor microenvironment may facilitate the invasive potential of HCC. In this article we mainly summarize the structure and function of TGF-β1 and its receptors and assess their role in metastasis and recurrence of hepatocellular carcinoma.

TGF beta1 and related-Smads contribute to pulmonary metastasis of hepatocellular carcinoma in mice model

Background

Recent studies indicate that Transforming Growth Factor beta (TGF β) correlated with pulmonary metastasis of cancers. However, the correlation between TGF β and pulmonary metastasis of hepatocellular carcinoma (HCC) is till unknown.

Methods

We detected the in vitro and in vivo expression levels of TGF β1/Smads by Real-time PCR and Western blot in MHCC97-H and MHCC97–L cell lines, which are HCC cell lines and have higher and lower pulmonary metastatic potential respectively.

Results

TGF β1 mRNA level in MHCC97-L tumors were higher than that in MHCC97-H tumors, (2.81±1.61 vs. 1.24±0.96, P=0.002), TGF β1 protein level in MHCC97-L tumors were also higher than that in MHCC97-H tumors (1.37±0.95 vs. 0.32±0.22, P<0.001). In addition, the TGF β1 mRNA level positively correlated with pulmonary metastasis, and the relations between TGF β1 and Smads were also found (R²=0.12 and 0.40, respectively).

Conclusions

Our results suggest that TGF β/ Smads promote pulmonary metastasis of HCC.

TGF-β signaling in onset and progression of hepatocellular carcinoma

Transforming growth factor (TGF)-β is a central regulator in chronic liver disease, contributing to all stages of disease progression from initial liver injury through inflammation and fibrosis to cirrhosis and hepatocellular carcinoma. Liver damage-induced levels of active TGF-β enhance hepatocyte destruction and mediate hepatic stellate cell and fibroblast activation resulting in a wound-healing response, including myofibroblast generation and extracellular matrix deposition. Further evidence points to a decisive role of cytostatic and apoptotic functions mediated on hepatocytes, which is critical for the control of liver mass, with loss of TGF-β activities resulting in hyperproliferative disorders and cancer. This concept is based on studies that describe a bipartite role of TGF-β with tumor suppressor functions at early stages of liver damage and regeneration, whereas during cancer progression TGF-β may turn from a tumor suppressor into a tumor promoter that exacerbates invasive and metastatic behavior. We have delineated this molecular switch of the pathway from cytostatic to tumor promoting in further detail and identify activation of survival signaling pathways in hepatocytes as a most critical requirement. Targeting the TGF-β signaling pathway has been explored to inhibit liver disease progression. While interfering with TGF-β signaling in various short-term animal models has demonstrated promising results, liver disease progression in humans is a process of decades with different phases in which TGF-β or its targeting may have both beneficial and adverse outcomes. We emphasize that, in order to achieve therapeutic effects, targeting TGF-β signaling in the right cell type at the right time is required.

Organ microenvironment affects growth and metastasis of hepatocellular carcinoma via the TGF-β/Smad pathway in mice

The interaction between cancer and the organ microenvironment is complex, and the transforming growth factor-β (TGF-β)/Smad pathway plays an important role in this interaction. However, the role of the organ microenvironment in hepatocellular carcinoma (HCC) is not well understood. To evaluate the effect of the organ microenvironment and the role of the TGF-β/Smad pathway, MHCC97-H cells were inoculated subcutaneously into nude mice and the resulting MHCC97-H subcutaneous tumor tissues were implanted into the livers of the mice. We found a higher tumor weight and less pulmonary metastasis for the cancers in liver sites than for those in subcutaneous sites; the TGF-β1 levels were significantly different between the tumor models and correlated with tumor metastasis. Our results suggest that the organ microenvironment affects the growth and invasion of liver cancer cells. The TGF-β/Smad pathway is significant in the interaction between HCC and its microenvironment and affects the progression of HCC.

Tumor stroma as targets for cancer therapy

Cancer is not only composed malignant epithelial component but also stromal components such as fibroblasts, endothelial cells, and inflammatory cells, by which an appropriate tumor microenvironment (TME) is formed to promote tumorigenesis, progression, and metastasis. As the most abundant component in the TME, cancer-associated fibroblasts (CAFs) are involved in multifaceted mechanistic details including remodeling the extracellular matrix, suppressing immune responses, and secreting growth factors and cytokines that mediate signaling pathways to extensively affect tumor cell growth and invasiveness, differentiation, angiogenesis, and chronic inflammatory milieu. Today, more and more therapeutic strategies are purposefully designed to target the TME as well as tumor cells. This review will focus on the role of CAFs in tumor development and the novel strategies to target this component to inhibit the tumor growth.

Transforming growth factor beta 1 overexpression is closely related to invasiveness of hepatocellular carcinoma

OBJECTIVES

The study was aimed to investigate the relationship between plasma transforming growth factor beta 1 (TGF-β(1)) expression and the characteristics of hepatocellular carcinoma (HCC).

METHODS

Five hundred and seventy-one patients with HCC were subjected. Plasma TGF-β(1) levels were measured by enzyme-linked immunosorbent assay at diagnosis and compared in accordance with clinical and radiological characteristics.

RESULTS

Plasma TGF-β(1) levels were significantly higher in the diffuse infiltrative type (n = 159) than in the nodular type of HCC (n = 412; 3.94 ± 0.34 vs. 3.79 ± 0.29 log(10) pg/ml; p < 0.001). They were much higher in patients with portal vein thrombosis or extrahepatic metastasis than in those without (3.88 ± 0.34 vs. 3.81 ± 0.29 log(10) pg/ml, p = 0.008; 3.94 ± 0.35 vs. 3.82 ± 0.30 log(10) pg/ml, p = 0.013, respectively). Also, plasma TGF-β(1) levels showed a positive correlation with the size of HCC (r = 0.014, p < 0.001). Additionally, plasma TGF-β(1) levels were inversely related to the survival periods (p < 0.001).

CONCLUSION

TGF-β(1) was overexpressed in invasive types of HCC and it may be involved in the rapid progression of HCC.

New reagents for improved in vitro and in vivo examination of TGF-β signalling

Transforming growth factor-β (TGF-β) signalling controls many aspects of cell behaviour and is implicated as a key regulator in tumour formation and progression. However, evaluating levels of active TGF-β in culture medium or patient plasma and gaining definitive information regarding the activity of downstream substrates such as Sma- and Mad-related protein 3 (Smad3) in vivo with accuracy and sensitivity has been problematic. Therefore, to overcome these technical issues we have created a NIH3T3 cell line with stable pCAGA(12)-luc expression that can now be utilised to detect TGF-β activity with high sensitivity. In addition, we have created an adenoviral Smad3 luciferase reporter construct pAd.CAGA(12)-luc to successfully infect cells for in vitro assays, or prior to injection into mice and used to measure transcriptional activity in vivo. Thus, the NIH3T3-pCAGA(12)-luc cell line and the pAd.CAGA(12)-luc adenovirus will be extremely useful tools to measure TGF-β signalling activity with far greater efficiency and reliability compared to original and currently used reagents.

Targeting integrins in hepatocellular carcinoma

INTRODUCTION

Integrins, which are heterodimeric membrane glycoproteins, consist of a family of cell-surface receptors mediating cell-matrix and cell-cell adhesion. Analysis of tumor-associated integrins has revealed an important relationship between integrins and tumor development, bringing new insights into integrin-based cancer therapies. Hepatocellular carcinoma (HCC) is one of the most malignant tumors worldwide and integrins appeal to be a novel group of potential therapeutic targets for HCC.

AREAS COVERED

This review summarizes the current knowledge of integrins involved in HCC and the potential of integrin-targeted drugs in HCC therapy. A brief introduction on the structure, biological function and regulatory mechanism of integrins is given. The distinct expression patterns and biological functions of HCC-associated integrins are described. Finally, the current situation of integrin-based therapies in HCC and other tumor types are extensively discussed in the light of their implications in preclinical and clinical trials.

EXPERT OPINION

To date, increasing numbers of integrin-targeted drugs are undergoing development and they exhibit diverse effects in cancer clinical trials. Tumor heterogeneity should be emphasized in developing effective integrin-targeted drugs specific for HCC. A better understanding of how integrins cooperatively function in HCC will assist in designing more successful integrin-targeted therapeutic drugs and corresponding approaches.

Human mesenchymal stem cells inhibit metastasis of a hepatocellular carcinoma model using the MHCC97-H cell line

The effects of mesenchymal stem cells (MSC) on the growth and metastasis of human malignancies including hepatocellular carcinoma (HCC) are controversial, and the underlying mechanisms are not yet understood. The aim of this study was to explore the role of MSC in the progression of HCC. We investigated the effect of MSC on in vitro proliferation and invasion and in vivo tumor growth and pulmonary metastasis of MHCC97-H HCC cells with a high metastatic potential. The mRNA and protein levels of transforming growth factor-beta 1 (TGFβ1) and MMP, and their association with the effects of MSC on HCC cells were also evaluated. Co-culture of MHCC97-H cells with MSC conditioned medium significantly enhanced in vitro proliferation but inhibited invasiveness. Following MSC treatment of a nude mouse model bearing human HCC, the MSC were predominantly located in the HCC tissues. Compared with controls, MSC-treated mice exhibited significantly larger tumors (3080.51 ± 1234.78 mm(3) vs 2223.75 ± 1000.60 mm(3), P = 0.045), but decreased cellular numbers of lung metastases (49.75 ± 18.86 vs 227.22 ± 74.67, P = 0.046). Expression of TGFβ1 and MMP-2 was significantly downregulated in the MSC-treated HCC cells. TGFβ siRNA concurrently downregulated expression of TGFβ and MMP-2 in HCC cells and blocked the MSC-induced proliferation and invasiveness of MHCC97-H cells. The MSC enhanced tumor growth but significantly inhibited the invasiveness and metastasis of HCC, possibly through downregulation of TGFβ1. These findings suggest that MSC could be useful in controlling metastatic recurrence of HCC.

The tumor microenvironment in hepatocellular carcinoma: current status and therapeutic targets

A growing body of literature highlights the cross-talk between tumor cells and the surrounding peri-tumoral stroma as a key modulator of the processes of hepatocarcinogenesis, epithelial mesenchymal transition (EMT), tumor invasion and metastasis. The tumor microenvironment can be broadly classified into cellular and non-cellular components. The major cellular components include hepatic stellate cells, fibroblasts, immune, and endothelial cells. These cell types produce the non-cellular components of the tumor stroma, including extracellular matrix (ECM) proteins, proteolytic enzymes, growth factors and inflammatory cytokines. The non-cellular component of the tumor stroma modulates hepatocellular carcinoma (HCC) biology by effects on cancer signaling pathways in tumor cells and on tumor invasion and metastasis. Global gene expression profiling of HCC has revealed that the tumor microenvironment is an important component in the biologic and prognostic classification of HCC. There are substantial efforts underway to develop novel drugs targeting tumor-stromal interactions. In this review, we discuss the current knowledge about the role of the tumor microenvironment in pathogenesis of HCC, the role of the tumor microenvironment in the classification of HCC and efforts to develop treatments targeting the tumor microenvironment.

Increased liver-infiltrating CD8+FoxP3+ regulatory T cells are associated with tumor stage in hepatocellular carcinoma patients

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver, and patients who are diagnosed with this tumor typically have a poor prognosis. The suppressive effects of CD4(+)FoxP3(+) regulatory T cells on antitumor immune response in HCC have been studied in great detail. CD8(+)FoxP3(+) regulatory T cells have recently been detected in tumors; however, the role of CD8(+)FoxP3(+) regulatory T cells in HCC is still unknown. Here, the frequency and phenotype of CD8(+)FoxP3(+) regulatory T cells were analyzed by multicolor flow cytometry in liver of HCC patients and healthy donors. We observed that the percentage of these cells in HCC patients was significantly higher than that observed in healthy control donors (p = 0.0155); their phenotype was close to that of CD4(+) regulatory T cells. Furthermore, we show that CD8(+)FoxP3(+) regulatory T cells are activated and act as effector memory cells (EM, CD45RA(-)CCR7(-)CD27(+/-)CD28(+)). Most importantly, a higher percentage of intrahepatic CD8(+)FoxP3(+) regulatory T cells was found in patients with advanced HCC than in those with early HCC in terms of tumor-node-metastasis (TNM) stage (stage I vs III, p = 0.0007). These data suggest that CD8(+)FoxP3(+) regulatory T cells may contribute to HCC immune escape and disease progression.

Association between integrin expression and prognosis in localized prostate cancer

BACKGROUND

Integrins and other adhesion molecules are essential for maintaining the epithelial phenotype. Some studies have reported correlations between abnormalities in their expression and carcinogenesis, but their role in prostate cancer is unclear. Our aim was to study the expression profile of integrins in surgical specimens of prostate cancer and associate their expression patterns with patient outcomes.

METHODS

We selected 111 patients with localized prostate cancer who had undergone radical prostatectomy. Of these patients, 60 had no tumor recurrence after a median follow-up of 123 months. Integrin expression was evaluated by immunohistochemistry in a tissue microarray containing two tumor samples per patient. A semiquantitative analysis was employed. We measured the association between the expression of eight integrins and tumor recurrence.

RESULTS

Multivariate analysis showed that expression of alpha3 and alpha3beta1 was related to worse outcome. When alpha3 expression was strong and alpha3beta1 expression was positive, the odds of recurrence were 3.0- and 2.5-fold higher, respectively. Only 19% and 28% of patients were recurrence-free in a mean period of 123 months of follow up when their tumors showed strong alpha3 or positive alpha3beta1 immuno-expression, respectively.

CONCLUSIONS

We have shown that the expression of integrin alpha3beta1 was independently associated with tumor recurrence after radical prostatectomy, suggesting that this integrin is a potential prognostic marker.

Immunotherapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the third most common cause of cancer-related death worldwide and efficient treatment options are urgently needed. Based on its pathogenesis, in addition to a number of correlative studies, immunotherapy represents a potential therapeutic option for patients with HCC. However, tumors have also evolved numerous immune escape mechanisms, including the generation of cells with immune suppressor functions, such as Tregs and myeloid-derived suppressor cells. It has been shown that these suppressor cells mask tumor-specific immune responses in patients with HCC. Different immunotherapeutic approaches including peptide- and dendritic cell-based therapies have demonstrated promising results in patients with HCC. However, we propose that any of these immunotherapeutic approaches needs to be combined with a therapy specifically targeting suppressor cells in HCC.

Dermatopontin is expressed in human liver and is downregulated in hepatocellular carcinoma

Dermatopontin (DPT) was recently found as a downstream target of vitamin D receptor, which is a key molecule in the 1,25-dihydroxy-vitamin D(3) anti-hepatoma proliferation pathway. MCTx-1 from Millepora, a homolog of DPT, is identified as a cytotoxin towards leukemia cells. The aim of this study was to analyze DPT expression in hepatocellular carcinoma (HCC) based on the analysis for DPT gene in normal tissues in order to estimate its function in the progression of HCC. DPT mRNA expression was analyzed in normal tissues and HCC cell lines by RT-PCR, and in HCC tissue by RT-PCR and real-time PCR. Its protein was examined in HCC tissues by Western blot and immunohistochemistry assays. Meanwhile, transforming growth factor-beta1 (TGF-beta1) that is closely associated with HCC and DPT was observed by immunohistochemistry in HCC tissues. The results showed that DPT mRNA was strongly expressed in human fetal and adult liver, kidney, and spleen, weakly in ovary and heart, and absent in other tissues and HCC cell lines examined. Its mRNA was significantly downregulated in HCC tissues, while its protein was weakly expressed in tumor compared with non-tumor. DPT is located mainly in the cytoplasm of several cell types in the liver; it has been identified also in the extracellular matrix of the skin. TGF-beta1 was observed in extensive tumor tissue of HCC. This fact suggests that DPT can play various roles in different tissues and might be a molecule related to carcinogenesis and the progression of HCC via possible interaction with TGF-beta1 and other potential mechanisms.

Mechanisms of the epithelial-mesenchymal transition by TGF-beta

The formation of epithelial cell barriers results from the defined spatiotemporal differentiation of stem cells into a specialized and polarized epithelium, a process termed mesenchymal-epithelial transition. The reverse process, epithelial-mesenchymal transition (EMT), is a metastable process that enables polarized epithelial cells to acquire a motile fibroblastoid phenotype. Physiological EMT also plays an essential role in promoting tissue healing, remodeling or repair in response to a variety of pathological insults. On the other hand, pathophysiological EMT is a critical step in mediating the acquisition of metastatic phenotypes by localized carcinomas. Although metastasis clearly is the most lethal aspect of cancer, our knowledge of the molecular events that govern its development, including those underlying EMT, remain relatively undefined. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that oversees and directs all aspects of cell development, differentiation and homeostasis, as well as suppresses their uncontrolled proliferation and transformation. Quite dichotomously, tumorigenesis subverts the tumor suppressing function of TGF-beta, and in doing so, converts TGF-beta to a tumor promoter that stimulates pathophysiological EMT and metastasis. It therefore stands to reason that determining how TGF-beta induces EMT in developing neoplasms will enable science and medicine to produce novel pharmacological agents capable of preventing its ability to do so, thereby improving the clinical course of cancer patients. Here we review the cellular, molecular and microenvironmental mechanisms used by TGF-beta to mediate its stimulation of EMT in normal and malignant cells.

Laminin-binding integrins and their tetraspanin partners as potential antimetastatic targets

Within the integrin family of cell adhesion receptors, integrins alpha3beta1, alpha6beta1, alpha6beta4 and alpha7beta1 make up a laminin-binding subfamily. The literature is divided on the role of these laminin-binding integrins in metastasis, with different studies indicating either pro- or antimetastatic functions. The opposing roles of the laminin-binding integrins in different settings might derive in part from their unusually robust associations with tetraspanin proteins. Tetraspanins organise integrins into multiprotein complexes within discrete plasma membrane domains termed tetraspanin-enriched microdomains (TEMs). TEM association is crucial to the strikingly rapid cell migration mediated by some of the laminin-binding integrins. However, emerging data suggest that laminin-binding integrins also promote the stability of E-cadherin-based cell-cell junctions, and that tetraspanins are essential for this function as well. Thus, TEM association endows the laminin-binding integrins with both pro-invasive functions (rapid migration) and anti-invasive functions (stable cell junctions), and the composition of TEMs in different cell types might help determine the balance between these opposing activities. Unravelling the tetraspanin control mechanisms that regulate laminin-binding integrins will help to define the settings where inhibiting the function of these integrins would be helpful rather than harmful, and may create opportunities to modulate integrin activity in more sophisticated ways than simple functional blockade.

Inhibition of transforming growth factor beta receptor I kinase blocks hepatocellular carcinoma growth through neo-angiogenesis regulation

Curative therapies for patients with hepatocellular carcinoma (HCC) are mainly invasive, and with the exception of sorafenib, no medical treatments are available for advanced or metastatic stages of HCC. We investigated the antitumoral effect of blocking the transforming growth factor beta (TGF-beta) signaling pathway in HCC with LY2109761, a kinase inhibitor of TGF-beta receptor I kinase. The antitumor activity of LY2109761 was associated with inhibition of molecular pathways involved in neo-angiogenesis and tumor growth of HCC. This anti-angiogenic effect is more effective than that of bevacizumab, which specifically targets vascular endothelial growth factor (VEGF). We found that the paracrine cross-talk between HCC and endothelial cells is blocked by LY210976, inhibiting blood vessel formation. This effect was mediated by SMAD2/3 and affected the secretion of VEGF. Finally, LY2109761 does not show significant effects on physiological angiogenetic development.

CONCLUSION

These data support the rationale for targeting TGF-beta signaling in patients with HCC.

Inhibition of TGF-beta receptor I by siRNA suppresses the motility and invasiveness of T24 bladder cancer cells via modulation of integrins and matrix metalloproteinase

BACKGROUND

Urinary bladder transitional-cell carcinoma is still challenging because the mechanisms underlying the tumor progression are still largely unknown. Transforming growth factor beta1 (TGF-beta1) is considered a crucial molecule in the tumorigenesis of urinary bladder carcinoma. Many studies have indicated that it is also associated with epithelial-mesenchymal transition, angiogenesis, migration and metastases in many types of malignant tumors.

MATERIALS AND METHODS

We blocked the TGF-beta signal pathway in T24 human bladder cancer cells with a siRNA (TsiRNA), which targets the TGF-beta type I receptor and evaluated the effects of TGF-beta1 and TsiRNA on the cell motility and invasiveness by Matrigel migration assay, wound-healing assay and Matrigel invasion assay. RT-PCR and Western blotting analysis were used to examine the effects of TGF-beta1 and TsiRNA on the expression of TGFBRI and genes, which are related to tumor migration and invasion.

RESULTS

While exogenous TGF-beta1 enhanced the migration and invasion of T24 cells, TsiRNA significantly suppressed them. RT-PCR and Western blotting analysis revealed that TsiRNA could downregulate both the expression of alpha3, beta1 and alpha2 integrin subunits and the activity of matrix metalloproteinase 9 enhanced by exogenous TGF-beta1.

CONCLUSION

Our study suggested that inhibition of TGF-beta1 signaling pathway by siRNA could be beneficial in the treatment of patients with metastatic bladder cancer.

Targeting transforming growth factor (TGF)-betaRI inhibits activation of beta1 integrin and blocks vascular invasion in hepatocellular carcinoma

Vascular invasion is one of the major negative prognostic factors in patients with hepatocellular carcinoma (HCC), leading to cancer recurrence. To invade, HCC cells must penetrate the vessel wall, consisting of endothelial cells and extracellular matrix components, including fibronectin and fibrinogen. Employing invasive and noninvasive HCC cells, we studied the mechanism underlying vascular invasion. We show that HCC cells invade blood vessels via alpha5beta1, that is equally expressed in invasive and noninvasive cells. However, in the former, the intracytoplasmic tail of beta1 integrin is constitutively phosphorylated at threonine 788-789 and the extracellular part is conformationally activated. In noninvasive cells, beta1 integrin is not activated. Transforming growth factor (TGF)-beta1 specifically phosphorylates beta1 integrin (threonine 788-789) via Smad-2 and Smad-3, causing a conformational change of the extracellular component with an inside-out mechanism. This leads noninvasive HCC cells to behave like invasive cells. A selective TGF-betaRI inhibitor inhibits phosphorylation of the beta1 integrin intracytoplasmic tail, and blocks invasion of HCC cells, both constitutively invasive and with acquired invasive properties. In human HCC tissues with microvascular invasion, phospho-beta1 integrin was detected as well as TGF-beta1, p-Smad-2, and E-cadherin.

CONCLUSION

TGF-beta1 promotes vascular invasion by activating beta1 integrin. This suggests a rationale for targeting TGF-betaRI in future clinical trials.

MicroRNAs: target recognition and regulatory functions

MicroRNAs (miRNAs) are endogenous approximately 23 nt RNAs that play important gene-regulatory roles in animals and plants by pairing to the mRNAs of protein-coding genes to direct their posttranscriptional repression. This review outlines the current understanding of miRNA target recognition in animals and discusses the widespread impact of miRNAs on both the expression and evolution of protein-coding genes.

Integrin alpha V polymorphisms and haplotypes in a Korean population are associated with susceptibility to chronic hepatitis and hepatocellular carcinoma

BACKGROUND/AIMS

Integrins are cell surface receptors for extracellular matrix (ECM) proteins that initiate signalling pathways that modulate proliferation, survival, invasion or metastasis. Consequently, integrins are potential targets for the treatment of cancer. In this study, we investigated whether single nucleotide polymorphisms (SNPs) in integrin alpha(V) (ITGAV) in a Korean population were associated with chronic hepatitis B virus (HBV) infection and HBV-infected hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Thirteen ITGAV SNPs in 111 cases of chronic HBV infection, 86 cases of HBV-infected HCC and 107 cases of acute self-limited HBV infection were genotyped using Illumina's Sentrix array matrix (SAM) chip.

RESULTS

The ITGAV intron SNPs rs9333289 and rs11685758, the 3'-untranslated region SNP rs1839123 and haplotype 3 (T-T-A) were associated with enhanced susceptibility to HBV-infected HCC (OR=1.75-2.42; P=0.02-0.05), while the intron SNP rs2290083 was associated with both chronic infection and HBV-infected HCC (OR=1.73-2.01; P=0.01-0.04). In addition, both rs2290083 and ht1 (C-C-G) were associated with the age at which chronic infection occurred, as determined by Cox relative hazard analysis (RH=1.39-1.62, P=0.04-0.01)

CONCLUSION

ITGAV SNPs and haplotypes may be genetic factors that increase the susceptibility of Koreans to chronic HBV infection and HBV-infected HCC.

Betaig-h3 interacts with alpha3beta1 integrin to promote adhesion and migration of human hepatoma cells

betaig-h3 is a TGF-induced extracellular matrix (ECM) protein. Our previous evidence suggests that beta ig-h3 may promote adhesion and invasion potential of human hepatoma cells, but the mechanism underlying this process is still unknown. The present study identifies a pivotal role for molecules of the beta ig-h3 signal transduction pathway. We demonstrated that beta ig-h3 co-immunoprecipitated with alpha 3beta 1 integrin in human 7721 hepatoma cells. The addition of alpha 3beta 1 integrin antibodies inhibited the elevated adhesion and migration in beta ig-h3-over-expressing 7721 cells, but not in beta ig-h3 siRNA transfected 7721 cells. The expression and activity of integrin downstream molecules FAK and paxillin show a positive correlation with beta ig-h3 expression in different human hepatoma cells. Levels of focal adhesions and stress fibers were decreased in beta ig-h3 siRNA transfected 7721 cells. We suggest that by interaction with alpha 3beta 1 integrin, beta ig-h3 activates FAK-paxillin signaling linkage, leads to cytoskeleton reorganization, and thus enhances the metastatic potentials of human hepatoma cells.

Immunoexpression of integrins in ameloblastoma, adenomatoid odontogenic tumor, and human tooth germs

The expression of integrins alpha2beta1, alpha3beta1, and alpha5beta1 in 30 ameloblastomas (20 solid and 10 unicystic tumors), 12 adenomatoid odontogenic tumors (AOTs), and 5 human tooth germs in different stages of odontogenesis was analyzed. The distribution, location, pattern, and intensity of immunohistochemical expression were evaluated. Intensity was analyzed using scores (0 = absence, 1 = weak staining, and 2 = strong staining). No difference in the immunoexpression of the integrins was observed between solid and unicystic ameloblastomas. When these two ameloblastoma types were pooled into a single group, the following significant differences were found: immunoexpression of integrin alpha2beta1 was stronger in ameloblastomas than in AOTs and tooth germs, and the expression of integrin alpha5beta1 was stronger in ameloblastomas than in AOTs. The lack of detection of integrin alpha3beta1 in tooth germs and its detection in the odontogenic tumors studied suggest that this integrin might be used as a marker of neoplastic transformation in odontogenic tissues.

Functional and clinical evidence for NDRG2 as a candidate suppressor of liver cancer metastasis

We searched for potential suppressors of tumor metastasis by identifying the genes that are frequently down-regulated in hepatocellular carcinomas (HCC) while being negatively correlated with clinical parameters relevant to tumor metastasis, and we report here on the identification of N-myc downstream regulated gene 2 (NDRG2) as a promising candidate. NDRG2 expression was significantly reduced in HCC compared with nontumor or normal liver tissues [87.5% (35 of 40) and 62% (62 of 100) at RNA and protein levels, respectively]. Reduction of NDRG2 expression was intimately associated with promoter hypermethylation because its promoter region was found to carry extensively methylated CpG sites in HCC cell lines and primary tumors. Immunohistochemical analysis of NDRG2 protein in 100 HCC patient tissues indicated that NDRG2 expression loss is significantly correlated with aggressive tumor behaviors such as late tumor-node-metastasis (TNM) stage (P = 0.012), differentiation grade (P = 0.024), portal vein thrombi (P = 0.011), infiltrative growth pattern (P = 0.015), nodal/distant metastasis (P = 0.027), and recurrent tumor (P = 0.021), as well as shorter patient survival rates. Ectopically expressed NDRG2 suppressed invasion and migration of a highly invasive cell line, SK-Hep-1, and experimental tumor metastasis in vivo, whereas small interfering RNA-mediated knockdown resulted in increased invasion and migration of a weakly invasive cell line, PLC/PRF/5. In addition, NDRG2 could antagonize transforming growth factor beta1-mediated tumor cell invasion by specifically down-regulating the expression of matrix metalloproteinase 2 and laminin 332 pathway components, with concomitant suppression of Rho GTPase activity. These results suggest that NDRG2 can inhibit extracellular matrix-based, Rho-driven tumor cell invasion and migration and thereby play important roles in suppressing tumor metastasis in HCC.

Lysyl oxidase like 4, a novel target gene of TGF-beta1 signaling, can negatively regulate TGF-beta1-induced cell motility in PLC/PRF/5 hepatoma cells

Transforming growth factor-beta1 (TGF-beta1) is a multi-functional cytokine involved in the regulation of cell proliferation, differentiation and extracellular matrix formation. In search for novel genes mediating the TGF-beta1 function at downstream signaling, we performed a cDNA microarray analysis and identified 60 genes whose expression is regulated by TGF-beta1 in the liver cancer cell line PLC/PRF/5. Among them, we report here lysyl oxidase like 4 (LOXL4) as a novel target of TGF-beta1 signaling, and provide experimental evidence for its expression regulation and function. LOXL4 was found to be the only member of LOX family whose expression is induced by TGF-beta1 in hepatoma cells. Deletion mapping of the LOXL4 promoter indicated that the TGF-beta1 regulation of LOXL4 expression is mediated through the binding of AP1 transcription factor to a conserved region of the promoter. This was confirmed by the chromatin immunoprecipitation assay that captured c-Fos-bound chromatin from TGF-beta1-treated cells. Forced expression of LOXL4 in PLC/PRF/5 cells resulted in inhibition of cell motility through Matrigel in the presence of TGF-beta1 treatment. In parallel, LOXL4 suppressed the expression of laminins and alpha3 integrin and the activity of MMP2. These results suggest that LOXL4 may function as a negative feedback regulator of TGF-beta1 in cell invasion by inhibiting the metabolism of extracellular matrix (ECM) components.

Blocking transforming growth factor-beta up-regulates E-cadherin and reduces migration and invasion of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) treatment is challenging because the mechanisms underlying tumor progression are still largely unknown. Transforming growth factor (TGF)-beta1 is considered a crucial molecule in HCC tumorigenesis because increased levels of patients' serum and urine are associated with disease progression. The aim of the present study was to investigate the inhibition of TGF-beta signaling and its impact on HCC progression. Human HCC cell lines were treated with a TGF-beta receptor kinase inhibitor (LY2109761) whose selectivity was determined in a kinase assay. Exogenous TGF-beta1 phosphorylates the TGF-beta receptor, consequently activating Smad-2, whereas the drug selectively blocks this effect and dephosphorylates autocrine p-Smad-2 at concentrations ranging from 0.001 to 0.1 microM. A cytotoxic effect documented by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), trypan blue, and propidium iodide staining assays was observed at 10microM, whereas the drug inhibits (P < 0.001) the migration of HCC cells on fibronectin, laminin-5, and vitronectin and invasion through Matrigel (P < 0.001) at concentrations up to 0.1 microM. LY2109761 up-regulates (P < 0.001) E-cadherin mRNA and protein levels. This increase was localized at the cellular membrane where E-cadherin mediates anchorage that is cell-cell dependent. Consistently, a functional monoclonal antibody that inhibits E-cadherin-dependent cell-cell contact restores the migratory and invasive activity. Finally, nonmetastatic HCC tissues from 7 patients were cultured with TGF-beta1 in the presence or absence of LY2109761. E-cadherin expression was reduced by TGF-beta1 and was significantly (P < 0.0001) increased by LY2109761 treatment, measured by quantitative real-time PCR on microdissected tissues and by immunohistochemistry on serial sections. In 72 patients, E-cadherin tissue expression was more weakly expressed in metastatic than in nonmetastatic HCC (P < 0.0001).

CONCLUSION

LY2109761 blocks migration and invasion of HCC cells by up-regulating E-cadherin, suggesting that there could be a mechanistic use for this molecule in clinical trials.

Epithelial-mesenchymal transition and the invasive potential of tumors

The development of metastasis requires the movement and invasion of cancer cells from the primary tumor into the surrounding tissue. To acquire such invasive abilities, epithelial cancer cells must undergo several phenotypic changes. Some of these, including alterations in cell adhesion and migration, are reminiscent of those observed during the developmental process termed epithelial-mesenchymal transition (EMT). Several master gene regulatory programs known to promote EMT during development have recently been discovered to play key roles in cancer progression. In particular, the regulation of cell adhesion molecules and the signaling pathways linking them to mechanisms of gene regulation has emerged as an important determinant of tumor cell invasion and metastasis. A deeper understanding of these mechanisms should allow both better diagnosis and the development of specific treatments for invasive cancer.

Integrins as antimetastatic targets of RGD-independent snake venom components in liver metastasis [corrected]

Metastasis comprises several subsequent steps including local invasion and intravasation at the primary site, then their adhesion/arrest within the vessels of host organs followed by their extravasation and infiltration into the target organ stroma. In contrast to previous studies which have used aspartate-glycine-arginine (RGD) peptides and antibodies against integrins, we used rare collagen- and laminin-antagonizing integrin inhibitors from snake venoms to analyze the colonization of the liver by tumor cells both by intravital microscopy and in vitro. Adhesion of liver-targeting tumor cells to the sinusoid wall components, laminin-1 and fibronectin, is essential for liver metastasis. This step is inhibited by lebein-1, but not by lebein-2 or rhodocetin. Both lebeins from the Vipera lebetina venom block integrin interactions with laminins in an RGD-independent manner. Rhodocetin is an antagonist of alpha2beta1 integrin, a collagen receptor on many tumor cells. Subsequent to tumor cell arrest, extravasation into the liver stroma and micrometastasis are efficiently delayed by rhodocetin. This underlines the importance of alpha2beta1 integrin interaction with the reticular collagen I-rich fibers in liver stroma. Antagonists of laminin- and collagen-binding integrins could be valuable tools to individually block the direct interactions of tumor cells with distinct matrix components of the Disse space, thereby reducing liver metastasis.

Signaling networks guiding epithelial-mesenchymal transitions during embryogenesis and cancer progression

Epithelial-mesenchymal transition (EMT) describes the differentiation switch between polarized epithelial cells and contractile and motile mesenchymal cells, and facilitates cell movements and generation of new tissue types during embryogenesis. Many secreted polypeptides are implicated in the EMT process and their corresponding intracellular transduction pathways form highly interconnected networks. Transforming growth factor-beta, Wnt, Notch and growth factors acting through tyrosine kinase receptors induce EMT and often act in a sequential manner. Such growth factors orchestrate the concerted regulation of an elaborate gene program and a complex protein network, needed for establishment of new mesenchymal phenotypes after disassembly of the main elements of epithelial architecture, such as desmosomes, as well as tight, adherens and gap junctions. EMT of tumor cells occurs during cancer progression and possibly generates cell types of the tumor stroma, such as cancer-associated myofibroblasts. EMT contributes to new tumor cell properties required for invasiveness and vascular intravasation during metastasis. Here we present some of the current mechanisms that mediate the process of EMT and discuss their relevance to cancer progression.

Molecular classification of nodal metastasis in primary larynx squamous cell carcinoma

Classification and prognosis of larynx squamous cell carcinoma (LSCC) depends on clinical and histopathological examination. Currently, expression profiling harbors the potential to investigate, classify, and better manage cancer. Gene expression profiles of 22 primary LSCCs were analyzed by microarrays containing 19,200 cDNAs. GOAL functionally classified differentially expressed genes, and a novel "in silico" procedure identified physical gene clusters differentially transcribed. A signature of 158 genes differentiated tumors with nodal metastasis. A novel statistical method allowed categorization of metastatic tumors into 2 distinct subgroups of differential gene expression patterns. Among genes correlated to nodal metastatic progression, we verified in vitro that NM23-H3 reduced cell motility and TRIM8 were a growth suppressor. Six chromosomal regions were specifically downregulated in metastatic tumors. This large-scale gene expression analysis in LSCC provides information on changes in genomic activity associated with lymphonodal metastasis and identifies molecules that might prove useful as novel therapeutic targets.

Changes in adhesive and migratory characteristics of hepatocellular carcinoma (HCC) cells induced by expression of alpha3beta1 integrin

The invasive and metastatic potentials of hepatocellular carcinoma are positively correlated with the expression level of alpha3beta1 integrin, a high-affinity adhesion receptor for laminin isoforms including laminin-5. In this study, we investigated changes in the adhesive and invasive behaviors of human HCC HepG2 cells after transfection with cDNA for alpha3 integrin in order to elucidate the direct involvement of this integrin in these cellular processes. We introduced cDNA for splice variants of alpha3 integrin (alpha3A and alpha3B) into the cells, and selected two transfectant clones (HepG2-3A and HepG2-3B), which express the alpha3A and alpha3B integrins, respectively. Both transfectant cells adhered almost equally to laminin-5-coated plates in an alpha3 integrin-dependent manner, indicating that transfected alpha3Abeta1 and alpha3Bbeta1 integrins were functionally active in these cells. The migratory and invasive potentials of the transfectant cells were assessed by scratch wound assay and in vitro chemoinvasion assay. The results demonstrated that the migration of HepG2-3A and HepG2-3B cells but not of mock transfectant (HepG2-M) cells was stimulated on the plates coated with laminin-5. Furthermore, HepG2-3A and HepG2-3B cells were found to be more invasive into laminin-5-containing matrices than were HepG2-M cells. These results strongly suggest that enhanced expression of alpha3beta1 integrin on HCC cells is directly involved in their malignant phenotypes such as invasion and metastasis.

Integrin alpha3beta1 potentiates TGFbeta-mediated induction of MMP-9 in immortalized keratinocytes

Transforming growth factor-beta (TGFbeta) signaling pathways regulate a number of keratinocyte functions during epidermal carcinogenesis and wound healing, including proliferation, survival, and migration. TGFbeta can induce expression of the matrix metalloproteinase-9 (MMP-9), which has critical roles in promoting extracellular matrix remodeling and angiogenesis during tumorigenesis and tissue repair. Integrin alpha3beta1 is a cell adhesion receptor for laminin-332/laminin-5 with important roles in the survival and motility of epidermal keratinocytes. We previously reported that alpha3beta1 induces the expression of MMP-9 in immortalized keratinocytes. In this study, we show that endogenous TGFbeta is required for maximal MMP-9 expression, and that alpha3beta1 is required for full induction of MMP-9 protein and mRNA in response to TGFbeta. This regulation was not observed in non-immortalized, primary keratinocytes, indicating that coordinate regulation of MMP-9 by alpha3beta1 and TGFbeta is a property of immortalized cells. Alpha3beta1 did not regulate endogenous TGFbeta gene expression, TGFbeta bioavailability, or TGFbeta-Smad signaling. However, the combined inductive effects of TGFbeta and alpha3beta1 on MMP-9 were suppressed by a Src family kinase (SFK) inhibitor, indicating involvement of a SFK pathway. These findings provide early evidence of a role for alpha3beta1 in augmenting TGFbeta-mediated induction of MMP-9 in immortalized or transformed keratinocytes during skin carcinogenesis.

Pleomorphic adenoma and adenoid cystic carcinoma: in vitro study of the impact of TGFbeta1 on the expression of integrins and cytoskeleton markers of cell differentiation

Pleomorphic adenoma (PA) and adenoid cystic carcinoma (ACC) are the commonest benign and malignant salivary gland tumours respectively. Interactions between cells and extracellular matrix of PA and ACC, partially mediated by integrins, are important in their biology. The expression of integrins is regulated by numerous factors, amongst them, transforming growth factor beta1 (TGFbeta1). Our study investigated the effects of TGFbeta1 on the expression of integrin beta subunits in vitro and on the expression of cytoskeletal proteins of cells derived from PA and ACC. The expression of cytoskeletal differentiation markers and integrins was assessed using immunofluorescence. ELISA assays were employed to quantitate the expression integrins and MTT assays evaluated the mitochondrial activity of cells stimulated with TGFbeta1. PA cells showed increased expression of integrins and de novo expression of differentiation markers upon TGFbeta1 stimulation. ACC cells were less responsive to such stimulation. This may reflect important differences in the biological behaviour of benign and malignant cells.

Novel concepts in hepatocellular carcinoma: from molecular research to clinical practice

Hepatocellular carcinoma (HCC) is one of the most common malignancies in the world, burdened by a constantly increasing frequency. Therapy is currently restricted to invasive techniques but prognosis and survival are still unsatisfactory, mainly because of HCC recurrence and metastasis diffusion. This review will focus on the problem of tumor recurrence and/or metastasis, pointing out the role of the tissue microenvironment in affecting HCC behavior; new experimental findings will also be discussed in the light of their implications in medical care. Finally, new therapeutic approaches will be considered, paying particular attention to the tissue microenvironment as a potential target. In conclusion, this review will attempt to stimulate debate on translational research into HCC biology, in the field of clinical applications.

Actions of TGF-beta as tumor suppressor and pro-metastatic factor in human cancer

Transforming growth factor-beta (TGF-beta) is a secreted polypeptide that signals via receptor serine/threonine kinases and intracellular Smad effectors. TGF-beta inhibits proliferation and induces apoptosis in various cell types, and accumulation of loss-of-function mutations in the TGF-beta receptor or Smad genes classify the pathway as a tumor suppressor in humans. In addition, various oncogenic pathways directly inactivate the TGF-beta receptor-Smad pathway, thus favoring tumor growth. On the other hand, all human tumors overproduce TGF-beta whose autocrine and paracrine actions promote tumor cell invasiveness and metastasis. Accordingly, TGF-beta induces epithelial-mesenchymal transition, a differentiation switch that is required for transitory invasiveness of carcinoma cells. Tumor-derived TGF-beta acting on stromal fibroblasts remodels the tumor matrix and induces expression of mitogenic signals towards the carcinoma cells, and upon acting on endothelial cells and pericytes, TGF-beta regulates angiogenesis. Finally, TGF-beta suppresses proliferation and differentiation of lymphocytes including cytolytic T cells, natural killer cells and macrophages, thus preventing immune surveillance of the developing tumor. Current clinical approaches aim at establishing novel cancer drugs whose mechanisms target the TGF-beta pathway. In conclusion, TGF-beta signaling is intimately implicated in tumor development and contributes to all cardinal features of tumor cell biology.

RhoC is essential for TGF-beta1-induced invasive capacity of rat ascites hepatoma cells

Transforming growth factor-beta1 (TGF-beta1) is a multifunctional growth factor that plays a role in cell proliferation, differentiation, extracellular matrix production, apoptosis, and cell motility. We show here that TGF-beta1 increased the invasiveness of MM1 cells, which are a highly invasive clone of rat ascites hepatoma cells. Both mRNA and protein levels of RhoC but not RhoA in TGF-beta1-treated MM1 cells increased. In parallel with this increase in expression, RhoC activity was induced by TGF-beta1 treatment. When RhoC was overexpressed in MM1 cells, the invasive capacity increased. The RhoC-overexpressing cells formed more nodules than did mock cells when injected into rat peritoneum. Furthermore, when RhoC expression was reduced by transfection with shRNA/RhoC, the invasiveness of MM1 cells decreased with concomitant suppression of RhoC expression. Thus, the induced expression of RhoC by TGF-beta1 in MM1 cells plays a critical role in TGF-beta1-induced cell migration.

HTPAP gene on chromosome 8p is a candidate metastasis suppressor for human hepatocellular carcinoma

Our previous studies suggested that chromosome 8p deletion is associated with metastasis of hepatocellular carcinoma (HCC), in which some novel metastasis suppressor genes might be harbored. The present study aimed to identify the metastatic suppressor gene(s). A cDNA chip was constructed with the expressed sequence tags (ESTs) from chromosome 8p and used to compare the difference of expression profiling between the MHCC97-H and MHCC97-L cell lines with different metastatic potentials and similar genetic backgrounds. In all, 10 ESTs were significantly downregulated in MHCC97-H cell line with higher metastatic potential. One full-length gene, HTPAP (phosphatidic acid phosphatase type 2 domain containing 1B), was identified at chromosome 8p12. Sequencing and bioinformatic analyses revealed that HTPAP has 826 bp and encodes a putative protein of 175 amino acids with a transmembrane segment at the NH2 terminus, two protein kinase C phosphorylation site and one tyrosine kinase phosphorylation site. Its expression level in metastatic tumor tissues was much lower than that of primary HCC tissues. Both in vitro and in vivo assays suggested that HTPAP could suppress the invasion and metastasis of HCC. These suggested that HTPAP is a novel metastatic suppressor gene for HCC. The mechanism of the effect of HTPAP on HCC metastasis is not clear yet and deserves further investigation.

Transforming growth factor-beta1 upregulates transcription of alpha3 integrin gene in hepatocellular carcinoma cells via Ets-transcription factor-binding motif in the promoter region

The invasive and metastatic potentials of hepatocellular carcinoma (HCC) are positively correlated with the expression level of alpha3beta1 integrin, a high-affinity adhesion receptor for laminin isoforms. Transforming growth factor (TGF)-beta1 stimulates non-invasive HCC cells to acquire invasive phenotypes in association with the enhanced expression of alpha3 integrin. In this study, we investigated the molecular mechanism underlying the upregulation of alpha3beta1 integrin by TGF-beta1 in non-invasive HepG2 HCC cells. The treatment of HepG2 cells with TGF-beta1 induced the expression of alpha3 integrin and potentiated these cells to adhere to laminin-5 and to migrate through laminin-5-coated membranes. The promoter activity was measured by luciferase assay with a series of deletion constructs of the 5'-flanking region of the mouse alpha3 integrin gene, and the results showed that the -260/-119 region (relative to the major transcription start site) contained elements responsive to TGF-beta1 stimulation. The introduction of mutations into the putative consensus binding sequence for the Ets-family of transcription factors located at -133 greatly decreased the promoter activity responding to TGF-beta1 stimulation. The nuclear proteins extracted from TGF-beta1-stimulated HepG2 cells yielded a larger amount of DNA-nuclear protein complexes than did those extracted from unstimulated cells, as determined by an electrophoretic mobility shift assay using an oligonucleotide containing the Ets-site as a probe. These results suggest that TGF-beta1 stimulates HepG2 cells to express a higher level of alpha3 integrin by transcriptional upregulation via Ets transcription factors and to exhibit a more invasive phenotype.

Role of transforming growth factor-beta1-smad signal transduction pathway in patients with hepatocellular carcinoma

AIM: To explore the role of transforming growth factor-beta1 (TGF-β1)-smad signal transduction pathway in patients with hepatocellular carcinoma.

METHODS: Thirty-six hepatocellular carcinoma specimens were obtained from Qidong Liver Cancer Institute and Department of Pathology of the Second Affiliated Hospital of Nanjing Medical University. All primary antibodies (polyclonal antibodies) to TGF-β1, type II Transforming growth factor-beta receptor (TβR-II), nuclear factor-kappaB (NF-κB), CD34, smad4 and smad7,secondary antibodies and immunohistochemical kit were purchased from Zhongshan Biotechnology Limited Company (Beijing, China). The expressions of TGF-β1, TβR-II, NF-κB, smad4 and smad7 proteins in 36 specimens of hepatocellular carcinoma (HCC) and its adjacent tissue were separately detected by immunohistochemistry to observe the relationship between TGF-β1 and TβR-II, between NF-κB and TGF-β1, between smad4 and smad7 and between TGF-β1 or TβR-IIand microvessel density (MVD). MVD was determined by labelling the vessel endothelial cells with CD34.

RESULTS: The expression of TGF-β1, smad7 and MVD was higher in HCC tissue than in adjacent HCC tissue (P<0.01, P <0.05, P <0.01 respectively). The expression of TβR-IIand smad4 was lower in HCC tissue than in its adjacent tissue (P <0.01, P <0.05 respectively). The expression of TGF-β1 protein and NF-κB protein was consistent in HCC tissue. The expression of TGF-β1 and MVD was also consistent in HCC tissue. The expression of TβR-IIwas negatively correlated with that of MVD in HCC tissue.

CONCLUSION: The expressions of TGF-β1, TβR-II, NF-κB, smad4 and smad7 in HCC tissue, which are major up and down stream factors of TGF-β1-smad signal transduction pathway , are abnormal. These factors are closely related with MVD and may play an important role in HCC angiogenesis. The inhibitory action of TGF-β1 is weakened in hepatic carcinoma cells because of abnormality of TGF-β1 receptors (such as TβR-II) and postreceptors (such as smad4 and smad7). NF-κB may cause activation and production of TGF-β1.

Overexpression of platelet-derived growth factor receptor alpha in endothelial cells of hepatocellular carcinoma associated with high metastatic potential

PURPOSE

Little information is available on the heterogeneity of the vascular endothelium in hepatocellular carcinoma. The aim of this study was to identify the differentially expressed genes in tumor endothelial cells from highly metastatic hepatocellular carcinoma.

EXPERIMENTAL DESIGN

Magnetic beads conjugated with anti-CD31 antibody were used to isolate vascular endothelial cells from hepatocellular carcinoma xenografts with different metastatic potentials in nude mice. Gene expression profiles for different endothelial cells were compared by use of cDNA microarray. The up-regulated gene was confirmed by reverse transcription-PCR, real-time PCR, and immunohistochemistry.

RESULTS

cDNA microarray analysis revealed differential expression patterns in seven genes consistently presented in endothelial cells isolated from hepatocellular carcinoma with different metastatic potentials. Overexpression of platelet-derived growth factor receptor alpha was found only in the endothelium of highly metastatic hepatocellular carcinoma, which was confirmed by reverse transcription-PCR, real-time PCR, and immunohistochemistry. Oral administration of STI571 (imatinib mesylate or Glivec), a protein tyrosine kinase inhibitor of platelet-derived growth factor receptor, combined with s.c. injection of IFN-alpha not only effectively reduced tumor weight (by 81.8%) and microvessel density (by 70.2%) but also inhibited lung metastasis (by 100%). Furthermore, immunohistochemical analysis of platelet-derived growth factor receptor alpha in human hepatocellular carcinoma tissues revealed its correlation with postoperative recurrence, especially in patients without microvessel invasion.

CONCLUSIONS

The gene expression of hepatocellular carcinoma vascular endothelium is different between tumors with different metastatic potential. Platelet-derived growth factor receptor alpha, which is overexpressed in endothelium of highly metastatic hepatocellular carcinoma, may serve as a biomarker for predicting metastasis and a therapeutic target for highly metastatic hepatocellular carcinoma.