Invasiveness of hepatocellular carcinoma cell lines: contribution of hepatocyte growth factor, c-met, and transcription factor Ets-1

Correlation between hypoxia and HGF/c-MET expression in the management of pancreatic cancer

Pancreatic cancer (PC) is very deadly and difficult to treat. The presence of hypoxia has been shown to increase the probability of cancer developing and spreading. Pancreatic ductal adenocarcinoma (PDAC/PC) has traditionally viewed a highly lethal form of cancer due to its high occurrence of early metastases. Desmoplasia/stroma is often thick and collagenous, with pancreatic stellate cells as the primary source (PSCs). Cancer cells and other stromal cells interact with PSCs, promoting disease development. The hepatocyte growth factor (HGF)/c-MET pathway have been proposed as a growth factor mechanism mediating this interaction. Human growth factor (HGF) is secreted by pancreatic stellate cells (PSCs), and its receptor, c-MET, is generated by pancreatic cancer cells and endothelial cells. Hypoxia is frequent in malignant tumors, particularly pancreatic (PC). Hypoxia results from limitless tumor development and promotes survival, progression, and invasion. Hypoxic is becoming a critical driver and therapeutic target of pancreatic cancer as its hypoxia microenvironment is defined. Recent breakthroughs in cancer biology show that hypoxia promotes tumor proliferation, aggressiveness, and therapeutic resistance. Hypoxia-inducible factors (HIFs) stabilize hypoxia signaling. Hypoxia cMet is a key component of pancreatic tumor microenvironments, which also have a fibrotic response, that hypoxia, promotes and modulates. c-Met is a tyrosine-protein kinase. As describe it simply, the MET gene in humans' codes for a protein called hepatocyte growth factor receptor (HGFR). Most cancerous tumors and pancreatic cancer in particular, suffer from a lack of oxygen (PC). Due to unrestrained tumor development, hypoxia develops, actively contributing to tumor survival, progression, and invasion. As the processes by which hypoxia signaling promotes invasion and metastasis become clear, c-MET has emerged as an important determinant of pancreatic cancer malignancy and a potential pharmacological target. This manuscript provides the most current findings on the role of hypoxia and HGF/c-MET expression in the treatment of pancreatic cancer.

Targeting HGF/c-MET Axis in Pancreatic Cancer

Pancreatic cancer (pancreatic ductal adenocarcinoma (PDAC/PC)) has been an aggressive disease that is associated with early metastases. It is characterized by dense and collagenous desmoplasia/stroma, predominantly produced by pancreatic stellate cells (PSCs). PSCs interact with cancer cells as well as other stromal cells, facilitating disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells and endothelial cells. The current review discusses the role of the MET/HGF axis in tumour progression and dissemination of pancreatic cancer. Therapeutic approaches that were developed targeting either the ligand (HGF) or the receptor (c-MET) have not been shown to translate well into clinical settings. We discuss a two-pronged approach of targeting both the components of this pathway to interrupt the stromal-tumour interactions, which may represent a potential therapeutic strategy to improve outcomes in PC.

Syndecan-1 Promotes Hepatocyte-Like Differentiation of Hepatoma Cells Targeting Ets-1 and AP-1

Syndecan-1 is a transmembrane heparan sulfate proteoglycan which is indispensable in the structural and functional integrity of epithelia. Normal hepatocytes display strong cell surface expression of syndecan-1; however, upon malignant transformation, they may lose it from their cell surfaces. In this study, we demonstrate that re-expression of full-length or ectodomain-deleted syndecan-1 in hepatocellular carcinoma cells downregulates phosphorylation of ERK1/2 and p38, with the truncated form exerting an even stronger effect than the full-length protein. Furthermore, overexpression of syndecan-1 in hepatoma cells is associated with a shift of heparan sulfate structure toward a highly sulfated type specific for normal liver. As a result, cell proliferation and proteolytic shedding of syndecan-1 from the cell surface are restrained, which facilitates redifferentiation of hepatoma cells to a more hepatocyte-like phenotype. Our results highlight the importance of syndecan-1 in the formation and maintenance of differentiated epithelial characteristics in hepatocytes partly via the HGF/ERK/Ets-1 signal transduction pathway. Downregulation of Ets-1 expression alone, however, was not sufficient to replicate the phenotype of syndecan-1 overexpressing cells, indicating the need for additional molecular mechanisms. Accordingly, a reporter gene assay revealed the inhibition of Ets-1 as well as AP-1 transcription factor-induced promoter activation, presumably an effect of the heparan sulfate switch.

Infusion of Human Mesenchymal Stem Cells Improves Regenerative Niche in Thioacetamide-Injured Mouse Liver

BACKGROUND

This study investigated whether xenotransplantation of human Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) reduces thioacetamide (TAA)-induced mouse liver fibrosis and the underlying molecular mechanism.

METHODS

Recipient NOD/SCID mice were injected intraperitoneally with TAA twice weekly for 6 weeks before initial administration of WJ-MSCs. Expression of regenerative and pro-fibrogenic markers in mouse fibrotic livers were monitored post cytotherapy. A hepatic stallate cell line HSC-T6 and isolated WJ-MSCs were used for in vitro adhesion, migration and mechanistic studies.

RESULTS

WJ-MSCs were isolated from human umbilical cords by an explant method and characterized by flow cytometry. A single infusion of WJ-MSCs to TAA-treated mice significantly reduced collagen deposition and ameliorated liver fibrosis after 2-week therapy. In addition to enhanced expression of hepatic regenerative factor, hepatocyte growth factor, and PCNA proliferative marker, WJ-MSC therapy significantly blunted pro-fibrogenic signals, including Smad2, RhoA, ERK. Intriguingly, reduction of plasma fibronectin (pFN) in fibrotic livers was noted in MSC-treated mice. In vitro studies further demonstrated that suspending MSCs triggered pFN degradation, soluble pFN conversely retarded adhesion of suspending MSCs onto type I collagen-coated surface, whereas pFN coating enhanced WJ-MSC migration across mimicked wound bed. Moreover, pretreatment with soluble pFN and conditioned medium from MSCs with pFN strikingly attenuated the response of HSC-T6 cells to TGF-β1-stimulation in Smad2 phosphorylation and RhoA upregulation.

CONCLUSION

These findings suggest that cytotherapy using WJ-MSCs may modulate hepatic pFN deposition for a better regenerative niche in the fibrotic livers and may constitute a useful anti-fibrogenic intervention in chronic liver diseases.

Down-Regulation of LINC00460 Represses Metastasis of Colorectal Cancer via WWC2

BACKGROUND

Colorectal cancer (CRC) is one of the most prevalent cancers and a common cause of cancer-related death. Long noncoding RNAs have been reported to play an essential role in the development of CRC.

AIMS

This study aimed to investigate the possible function of LINC00460 in CRC.

METHODS

Initially, microarray-based gene expression profiling of CRC was employed to identify differentially expressed genes. Next, the expression of LINC00460 was examined and the cell line presenting with the highest LINC00460 expression was selected for subsequent experimentation. Then, the interaction among LINC00460, ERG, and WWC2 was identified. The effect of LINC00460 on proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT)-related factors as well as tumorigenicity of transfected cells was examined with gain- and loss-of-function experiments.

RESULTS

LINC00460 was robustly induced while WWC2 was poorly expressed in CRC. In addition, LINC00460 could down-regulate WWC2 through interaction with ERG, which led to promoted invasion, migration, and EMT of CRC cells in addition to tumor growth in vivo. Besides, down-regulation of LINC00460 exerted inhibitory effect on these biological activities.

CONCLUSION

Taken together, the key findings of the current study provided evidence suggesting that silencing of LINC00460 could potentially suppress EMT of CRC cells by increasing WWC2 via ERG, and highlighting that knockdown of LINC00460 could serve as a therapeutic target for CRC treatment.

Integrin α6 as an invasiveness marker for hepatitis B viral X-driven hepatocellular carcinoma

BACKGROUND

Hepatitis B virus (HBV) accounts for more than 60% of hepatocellular carcinoma (HCC) cases. However, there is limited information about the features of HBV-driven HCC that differentiate it from other types of HCC.

OBJECTIVE

The aim of this study is to find a gene specific to HBV-driven HCC and understand its role during tumorigenesis.

METHODS

The differences in gene expression patterns were analyzed among patients with hepatitis virus-unrelated liver cirrhosis, and hepatitis C virus- and HBV-driven HCC. Genes expressed only in HBV patients were compared to genes of transgenic mice expressing hepatitis B viral X gene.

RESULTS

Integrin α6 was commonly overexpressed in both HBV-driven HCC patients and transgenic mice expressing viral X. This gene's activation induced overexpression of integrin α6, as well as formation of integrins α6β1 and α6β4, without changing the expression of non-integrin laminin receptors. Suppression of integrin α6 caused significant inhibition of tumor migration in vitro.

CONCLUSIONS

This study found a significant association between HBV and integrin α6, which may be responsible for early migration and invasion of HCC. Thus, integrin α6 is a predictive marker for tumor recurrence and invasiveness of HBV-driven HCC.

Oxidation of heat shock protein 60 and protein disulfide isomerase activates ERK and migration of human hepatocellular carcinoma HepG2

Hepatocyte growth factor (HGF) and its receptor c-Met were frequently deregulated in hepatocellular carcinoma (HCC). Signaling pathways activated by HGF-c-Met are promising targets for preventing HCC progression. HGF can induce the reactive oxygen species (ROS) signaling for cell adhesion, migration and invasion of tumors including HCC. On the other hand, extracellular signal-regulated kinases (ERK), member of mitogen activated kinase, can be activated by ROS for a lot of cellular processes. As expected, HGF-induced phosphorylation of ERK and progression of HCC cell HepG2 were suppressed by ROS scavengers. By N-(biotinoyl)-N'-(iodoacetyl)-ethylenediamine (BIAM) labeling method, a lot of cysteine (-SH)-containing proteins with M.W. 50-75 kD were decreased in HepG2 treated with HGF or two other ROS generators, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and phenazine methosulfate. These redox sensitive proteins were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Among them, two chaperones, heat shock protein 60 (HSP60) and protein disulfide isomerase (PDI), were found to be the most common redox sensitive proteins in responding to all three agonists. Affinity blot of BIAM-labeled, immunoprecipitated HSP60 and PDI verified that HGF can decrease the cysteine (-SH) containing HSP60 and PDI. On the other hand, HGF and TPA increased cysteinyl glutathione-containing HSP60, consistent with the decrease of cysteine (-SH)-containing HSP60. Moreover, depletion of HSP60 and PDI or expression of dominant negative mutant of HSP60 with alteration of Cys, effectively prevented HGF-induced ERK phosphorylation and HepG2 migration.In conclusion, the redox sensitive HSP60 and PDI are required for HGF-induced ROS signaling and potential targets for preventing HCC progressions.

The Therapeutic Targeting of HGF/c-Met Signaling in Hepatocellular Carcinoma: Alternative Approaches

The poor prognosis of hepatocellular carcinoma (HCC), one of the most devastating cancers worldwide, is due to frequent recurrence and metastasis. Among the metastatic factors in the tumor microenvironment, hepatocyte growth factor (HGF) has been well known to play critical roles in tumor progression, including HCC. Therefore, c-Met is now regarded as the most promising therapeutic target for the treatment of HCC. However, there are still concerns about resistance and the side effects of using conventional inhibitors of c-Met, such as tyrosine kinase inhibitors. Recently, many alternative strategies of c-Met targeting have been emerging. These include targeting the downstream effectors of c-Met, such as hydrogen peroxide-inducible clone 5 (Hic-5), to block the reactive oxygen species (ROS)-mediated signaling for HCC progression. Also, inhibition of endosomal regulators, such as PKCε and GGA3, may perturb the c-Met endosomal signaling for HCC cell migration. On the other hand, many herbal antagonists of c-Met-dependent signaling, such as saponin, resveratrol, and LZ-8, were identified. Taken together, it can be anticipated that more effective and safer c-Met targeting strategies for preventing HCC progression can be established in the future.

ETS-1: A potential target of glycolysis for metabolic therapy by regulating glucose metabolism in pancreatic cancer

Pancreatic cancer is one of the most lethal malignancies of all types of cancer due to lack of early symptoms and its resistance to conventional therapy. In our previous study, we have shown that v‑ets erythroblastosis virus E26 oncogene homolog‑1 (ETS‑1) promote cell migration and invasion in pancreatic cancer cells. However, the function of ETS‑1 in regulation of glycolysis and autophagy during progression of pancreatic cancer has not been defined yet. In this study, we sought to identify the potential role for silencing ETS‑1 in reducing the expression of glucose transporter‑1 (GLUT‑1) to disturb glycolysis through alteration of 'Warburg effect', by which could result in AMP‑activated protein kinase (AMPK) activation, autophagy induction and reduction of cell viability. MTT assay was applied to assess the cell viability in ETS‑1 silencing cells and control groups. Glucose absorption rate, lactate production rate and cellular ATP level were measured by standard colorimetric assay kits. The levels of mRNAs of ETS‑1, GLUT‑1, autophagy‑related gene 5 (ATG5) and ATG7 were analyzed by qRT‑PCR. The expression of ETS‑1, GLUT‑1, ATG5, ATG7, p‑AMPK, and LC3II proteins were evaluated by western blot analysis. GraphPad Prism 5.0 was used for all statistical analysis. We found that cell viability was obviously attenuated after silencing ETS‑1. Besides, our results also showed that the expression of GLUT‑1 significantly declined in ETS‑1 silencing cell lines which resulted in a lower glucose utilization and lactate production. Furthermore, the inhibition of glycolysis, which depends on glucose utilization and lactate production, reduced the generation of energy in the form of ATP. Moreover, the reduction of cellular ATP was associated with stimulation of AMP‑activated protein kinase (AMPK) and induction of autophagy. Our results indicated that ETS‑1 induced autophagy after inhibition of glycolysis, and thus led to comparative decrease of cell viability. These results implied that ETS‑1 could be a potential target for tumor metabolic therapy.

Erratum to: Negative feedback of miR-29 family TET1 involves in hepatocellular cancer

Primary hepatocellular carcinoma (HCC) is the most common form of liver cancer and is one of the most common malignancies worldwide. Tumor suppressor gene silencing through DNA methylation contributes to cancer formation. The ten-eleven translocations (TET) family of α-ketogluta-rate-dependent dioxygenases catalyzes the sequential oxidation of 5-methylcytosine to 5-hydroxymethyl-cytosine, 5-formylcytosine and 5-carboxylcytosine, leading to eventual DNA demethylation. MicroRNAs are an abundant class of 17-25 nucleotides small noncoding RNAs, identified as important regulators of many diverse biological processes. In this study, we showed that TET1 expression was obviously reduced in the majority of examined HCC tissues. And we further investigated the expression and functional involvement of TET1 in proliferation, migration and invasion and determined that TET1 may function as a tumor suppressor. miR-29b was proved to inhibit metastasis through the targeting of TET1, indicating that downregulation of miR-29 may involve in HCC carcinogenesis and progression through potentiation of TET1 expression. Thus, we elucidated the roles of feedback of miR-29-TET1 downregulation in HCC development and suggested a potential target in identification of the prognosis and application of cancer therapy for HCC patients.

The role of the transcription factor Ets1 in carcinoma

Ets1 belongs to the large family of the ETS domain family of transcription factors and is involved in cancer progression. In most carcinomas, Ets1 expression is linked to poor survival. In breast cancer, Ets1 is primarily expressed in the triple-negative subtype, which is associated with unfavorable prognosis. Ets1 contributes to the acquisition of cancer cell invasiveness, to EMT (epithelial-to-mesenchymal transition), to the development of drug resistance and neo-angiogenesis. The aim of this review is to summarize the current knowledge on the functions of Ets1 in carcinoma progression and on the mechanisms that regulate Ets1 activity in cancer.

Hepatocyte Growth Factor from a Clinical Perspective: A Pancreatic Cancer Challenge

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the United States and incidence rates are rising. Both detection and treatment options for pancreatic cancer are limited, providing a less than 5% five-year survival advantage. The need for new biomarkers for early detection and treatment of pancreatic cancer demands the efficient translation of bench knowledge to provide clinical benefit. One source of therapeutic resistance is the pancreatic tumor microenvironment, which is characterized by desmoplasia and hypoxia making it less conducive to current therapies. A major factor regulating desmoplasia and subsequently promoting chemoresistance in pancreatic cancer is hepatocyte growth factor (HGF), the sole ligand for c-MET (mesenchymal-epithelial transition), an epithelial tyrosine kinase receptor. Binding of HGF to c-MET leads to receptor dimerization and autophosphorylation resulting in the activation of multiple cellular processes that support cancer progression. Inhibiting activation of c-MET in cancer cells, in combination with other approaches for reducing desmoplasia in the tumor microenvironment, might significantly improve the success of chemotherapy. Therefore, HGF makes a potent novel target for developing therapeutic strategies in combination with existing drugs for treating pancreatic adenocarcinoma. This review provides a comprehensive analysis of HGF and its promising potential as a chemotherapeutic target for pancreatic cancer.

Preclinical trials for prevention of tumor progression of hepatocellular carcinoma by LZ-8 targeting c-Met dependent and independent pathways

Hepatocellular carcinoma (HCC) is among the most lethal cancers. Mounting studies highlighted the essential role of the HGF/c-MET axis in driving HCC tumor progression. Therefore, c-Met is a potential therapeutic target for HCC. However, several concerns remain unresolved in c-Met targeting. First, the status of active c-Met in HCC must be screened to determine patients suitable for therapy. Second, resistance and side effects have been observed frequently when using conventional c-Met inhibitors. Thus, a preclinical system for screening the status of c-Met signaling and identifying efficient and safe anti-HCC agents is urgently required. In this study, immunohistochemical staining of phosphorylated c-Met (Tyr1234) on tissue sections indicated that HCCs with positive c-Met signaling accounted for approximately 46% in 26 cases. Second, many patient-derived HCC cell lines were established and characterized according to motility and c-Met signaling status. Moreover, LZ8, a medicinal peptide purified from the herb Lingzhi, featuring immunomodulatory and anticancer properties, was capable of suppressing cell migration and slightly reducing the survival rate of both c-Met positive and negative HCCs, HCC372, and HCC329, respectively. LZ8 also suppressed the intrahepatic metastasis of HCC329 in SCID mice. On the molecular level, LZ8 suppressed the expression of c-Met and phosphorylation of c-Met, ERK and AKT in HCC372, and suppressed the phosphorylation of JNK, ERK, and AKT in HCC329. According to receptor array screening, the major receptor tyrosine kinase activated in HCC329 was found to be the epidermal growth factor receptor (EGFR). Moreover, tyrosine-phosphorylated EGFR (the active EGFR) was greatly suppressed in HCC329 by LZ8 treatment. In addition, LZ8 blocked HGF-induced cell migration and c-Met-dependent signaling in HepG2. In summary, we designed a preclinical trial using LZ8 to prevent the tumor progression of patient-derived HCCs with c-Met-positive or -negative signaling.

PAX3 and ETS1 synergistically activate MET expression in melanoma cells

Melanoma is a highly aggressive disease that is difficult to treat due to rapid tumor growth, apoptotic resistance, and high metastatic potential. The MET tyrosine kinase receptor promotes many of these cellular processes, and while MET is often overexpressed in melanoma, the mechanism driving this overexpression is unknown. Since the MET gene is rarely mutated or amplified in melanoma, MET overexpression may be driven by to increased activation through promoter elements. In this report, we find that transcription factors PAX3 and ETS1 directly interact to synergistically activate MET expression. Inhibition of PAX3 and ETS1 expression in melanoma cells leads to a significant reduction of MET receptor levels. The 300 bp 5′ proximal MET promoter contains a PAX3 response element and two ETS1 consensus motifs. While ETS1 can moderately activate both of these sites without cofactors, robust MET promoter activation of the first site is PAX-dependent and requires the presence of PAX3, while the second site is PAX-independent. The induction of MET by ETS1 via this second site is enhanced by HGF-dependent ETS1 activation, thereby MET indirectly promotes its own expression. We further find that expression of a dominant negative ETS1 reduces the ability of melanoma cells to grow both in culture and in vivo. Thus, we discover a pathway where ETS1 advances melanoma through the expression of MET via PAX-dependent and independent mechanisms.

Negative feedback of miR-29 family TET1 involves in hepatocellular cancer

Primary hepatocellular carcinoma (HCC) is the most common form of liver cancer and is one of the most common malignancies worldwide. Tumor suppressor gene silencing through DNA methylation contributes to cancer formation. The ten-eleven translocations (TET) family of α-ketogluta-rate-dependent dioxygenases catalyzes the sequential oxidation of 5-methylcytosine to 5-hydroxymethyl-cytosine, 5-formylcytosine and 5-carboxylcytosine, leading to eventual DNA demethylation. MicroRNAs are an abundant class of 17-25 nucleotides small noncoding RNAs, identified as important regulators of many diverse biological processes. In this study, we showed that TET1 expression was obviously reduced in the majority of examined HCC tissues. And we further investigated the expression and functional involvement of TET1 in proliferation, migration and invasion, and determined that TET1 may function as a tumor suppressor. MiR-29b was proved to inhibit metastasis through the targeting of TET1, indicating that downregulation of miR-29 may involve in HCC carcinogenesis and progression through potentiation of TET1 expression. Thus, we elucidated the roles of feedback of miR-29-TET1 downregulation in HCC development and suggested a potential target in identification of the prognosis and application of cancer therapy for HCC patients.

Negative feedback of miR-29 family TET1 involves in hepatocellular cancer

Primary hepatocellular carcinoma (HCC) is the most common form of liver cancer and is one of the most common malignancies worldwide. Tumor suppressor gene silencing through DNA methylation contributes to cancer formation. The ten-eleven translocations (TET) family of α-ketogluta-rate-dependent dioxygenases catalyzes the sequential oxidation of 5-methylcytosine to 5-hydroxymethyl-cytosine, 5-formylcytosine and 5-carboxylcytosine, leading to eventual DNA demethylation. MicroRNAs are an abundant class of 17-25 nucleotides small noncoding RNAs, identified as important regulators of many diverse biological processes. In this study, we showed that TET1 expression was obviously reduced in the majority of examined HCC tissues. And we further investigated the expression and functional involvement of TET1 in proliferation, migration and invasion, and determined that TET1 may function as a tumor suppressor. MiR-29b was proved to inhibit metastasis through the targeting of TET1, indicating that downregulation of miR-29 may involve in HCC carcinogenesis and progression through potentiation of TET1 expression. Thus, we elucidated the roles of feedback of miR-29-TET1 downregulation in HCC development and suggested a potential target in identification of the prognosis and application of cancer therapy for HCC patients.

Gelatinase B/MMP-9 in Tumour Pathogenesis and Progression

Since its original identification as a leukocyte gelatinase/type V collagenase and tumour type IV collagenase, gelatinase B/matrix metalloproteinase (MMP)-9 is now recognised as playing a central role in many aspects of tumour progression. In this review, we relate current concepts concerning the many ways in which gelatinase B/MMP-9 influences tumour biology. Following a brief outline of the gelatinase B/MMP-9 gene and protein, we analyse the role(s) of gelatinase B/MMP-9 in different phases of the tumorigenic process, and compare the importance of gelatinase B/MMP-9 source in the carcinogenic process. What becomes apparent is the importance of inflammatory cell-derived gelatinase B/MMP-9 in tumour promotion, early progression and triggering of the "angiogenic switch", the integral relationship between inflammatory, stromal and tumour components with respect to gelatinase B/MMP-9 production and activation, and the fundamental role for gelatinase B/MMP-9 in the formation and maintenance of tumour stem cell and metastatic niches. It is also apparent that gelatinase B/MMP-9 plays important tumour suppressing functions, producing endogenous angiogenesis inhibitors, promoting inflammatory anti-tumour activity, and inducing apoptosis. The fundamental roles of gelatinase B/MMP-9 in cancer biology underpins the need for specific therapeutic inhibitors of gelatinase B/MMP-9 function, the use of which must take into account and substitute for tumour-suppressing gelatinase B/MMP-9 activity and also limit inhibition of physiological gelatinase B/MMP-9 function.

Molecular mechanisms of ETS transcription factor-mediated tumorigenesis

The E26 transformation-specific (ETS) family of transcription factors is critical for development, differentiation, proliferation and also has a role in apoptosis and tissue remodeling. Changes in expression of ETS proteins therefore have a significant impact on normal physiology of the cell. Transcriptional consequences of ETS protein deregulation by overexpression, gene fusion, and modulation by RAS/MAPK signaling are linked to alterations in normal cell functions, and lead to unlimited increased proliferation, sustained angiogenesis, invasion and metastasis. Existing data show that ETS proteins control pathways in epithelial cells as well as stromal compartments, and the crosstalk between the two is essential for normal development and cancer. In this review, we have focused on ETS factors with a known contribution in cancer development. Instead of focusing on a prototype, we address cancer associated ETS proteins and have highlighted the diverse mechanisms by which they affect carcinogenesis. Finally, we discuss strategies for ETS factor targeting as a potential means for cancer therapeutics.

LINE-1 ORF-1p functions as a novel HGF/ETS-1 signaling pathway co-activator and promotes the growth of MDA-MB-231 cell

Long interspersed nucleotide element (LINE)-1 ORF-1p is encoded by the human pro-oncogene LINE-1. It is involved in the development and progression of several human carcinomas, such as hepatocellular carcinoma and lung and breast cancers. The hepatocyte growth factor (HGF)/ETS-1 signaling pathway is involved in regulation of cancer cell proliferation, metastasis and invasion. The biological function of the interaction between LINE-1 ORF-1p and the HGF/ETS-1 signaling pathway in regulation of human breast cancer proliferation remains largely unknown. Here, we showed that LINE-1 ORF-1p enhanced ETS-1 transcriptional activity and increased expression of downstream genes of ETS-1. Interaction between ETS-1 and LINE-1 ORF-1p was identified by immunoprecipitation assays. LINE-1 ORF-1p modulated ETS-1 activity through cytoplasm/nucleus translocation and recruitment to the ETS-1 binding element in the MMP1 gene promoter. We also showed that LINE-1 ORF-1p promoted proliferation and anchorage-independent growth of MDA-MB-231 breast cancer cells. By investigating a novel role of the LINE-1 ORF-1p in the HGF/ETS-1 signaling pathway and MDA-MB-231 cells, we demonstrated that LINE-1 ORF-1p may be a novel ETS-1 coactivator and molecular target for therapy of human triple negative breast cancer.

MicroRNA-200c modulates epithelial-to-mesenchymal transition (EMT) in human colorectal cancer metastasis

OBJECTIVE

Distant metastasis is the major cause of cancer-related death in patients with colorectal cancer (CRC). Although the microRNA-200 (miR-200) family is a crucial inhibitor of epithelial-to-mesenchymal transition (EMT) in human cancer, the role of miR-200 members in the pathogenesis of metastatic CRC has not been investigated.

DESIGN

Fifty-four pairs of primary CRC and corresponding matched liver metastasis tissue specimens were analysed for expression and methylation status of the miR-200 family members. Functional analysis of miR-200c overexpression was investigated in CRC cell lines, and cells were analysed for proliferation, invasion and migration. Expression of several miR-200c target genes (ZEB1, ETS1 and FLT1) and EMT markers (E-cadherin and vimentin) in CRC cell lines and tissue specimens was validated.

RESULTS

Liver metastasis tissues showed higher expression of miR-200c (primary CRC = 1.31 vs. liver metastasis = 1.59; p = 0.0014) and miR-141 (primary CRC = 0.14 vs. liver metastasis = 0.17; p = 0.0234) than did primary CRCs, which was significantly associated with hypomethylation of the promoter region of these miRNAs (primary CRC = 61.2% vs. liver metastasis = 46.7%; p < 0.0001). The invasive front in primary CRC tissues revealed low miR-200c expression by in situ hybridization analysis. Transfection of miR-200c precursors resulted in enhanced cell proliferation but reduced invasion and migration behaviours in CRC cell lines. Overexpression of miR-200c in CRC cell lines caused reduced expression of putative gene targets, and resulted in increased E-cadherin and reduced vimentin expression. The associations between miR-200c, target genes and EMT markers were validated in primary CRCs and matching liver metastasis tissues.

CONCLUSIONS

miR-200c plays an important role in mediating EMT and metastatic behaviour in the colon. Its expression is epigenetically regulated, and miR-200c may serve as a potential diagnostic marker and therapeutic target for patients with CRC.

HGF-MET signals via the MLL-ETS2 complex in hepatocellular carcinoma

HGF signals through its cognate receptor, MET, to orchestrate diverse biological processes, including cell proliferation, cell fate specification, organogenesis, and epithelial-mesenchymal transition. Mixed-lineage leukemia (MLL), an epigenetic regulator, plays critical roles in cell fate, stem cell, and cell cycle decisions. Here, we describe a role for MLL in the HGF-MET signaling pathway. We found a shared phenotype among Mll(-/-), Hgf(-/-), and Met(-/-) mice with common cranial nerve XII (CNXII) outgrowth and myoblast migration defects. Phenotypic analysis demonstrated that MLL was required for HGF-induced invasion and metastatic growth of hepatocellular carcinoma cell lines. HGF-MET signaling resulted in the accumulation of ETS2, which interacted with MLL to transactivate MMP1 and MMP3. ChIP assays demonstrated that activation of the HGF-MET pathway resulted in increased occupancy of the MLL-ETS2 complex on MMP1 and MMP3 promoters, where MLL trimethylated histone H3 lysine 4 (H3K4), activating transcription. Our results present an epigenetic link between MLL and the HGF-MET signaling pathway, which may suggest new strategies for therapeutic intervention.

PKC mediates fluctuant ERK-paxillin signaling for hepatocyte growth factor-induced migration of hepatoma cell HepG2

Hepatocyte growth factor (HGF) is critical for triggering metastasis of hepatocellular carcinoma cell (HCC). Extracellular signal-regulated kinase (ERK) mediates HGF-induced cell migration via focal adhesion signaling. Protein kinase C (PKC) is a negative regulator of ERK activation, however, both PKC and ERK were required for HGF-induced cell migration. To address this intriguing issue, the signal mechanisms for HGF-induced HepG2 cell migration were investigated in a long-term fashion. HGF-induced phosphorylations of ERK, Src (at Tyr 416) and paxillin (at Ser178 and Tyr31) were up and down for 3 times within 24h. HGF also induced fluctuant PKC activation and Rac degradation. Consistently, HGF induced intermittent actin polarization within 24h, which can be blocked by the inhibitors of PKC (Bisindolymaleimide) and ERK. Inhibitor studies revealed that ERK was required for HGF-induced paxillin phosphorylation at Ser178, whereas PKC and Rac-1 may suppress HGF-induced phosphorylation of ERK and paxillin (at Ser178) and upregulate phosphorylation of paxillin at Tyr31. Based on shRNA technique, PKCα and δ were responsible for suppressing HGF-induced phosphorylation of ERK and paxillin (at Ser178), whereas PKC ε and ζ were required for phosphorylation of paxillin at Tyr31. The HGF-induced fluctuant signaling is reminiscent of c-Met endocytosis. Using Concanavalin A, an inhibitor of endocytosis, we found that c-Met endocytosis was required for PKC to suppress ERK phosphorylation. Moreover, HGF-induced c-Met degradation was also fluctuant, which can be prevented by Bisindolymaleimide. In conclusion, PKC is critical for mediating HGF-induced fluctuant ERK-paxillin signaling during cell migration, probably via triggering endosomal degradation of c-Met.

HGF-MET cascade, a key target for inhibiting cancer metastasis: the impact of NK4 discovery on cancer biology and therapeutics

Hepatocyte growth factor (HGF) was discovered in 1984 as a mitogen of rat hepatocytes in a primary culture system. In the mid-1980s, MET was identified as an oncogenic mutant protein that induces malignant phenotypes in a human cell line. In the early 1990s, wild-type MET was shown to be a functional receptor of HGF. Indeed, HGF exerts multiple functions, such as proliferation, morphogenesis and anti-apoptosis, in various cells via MET tyrosine kinase phosphorylation. During the past 20 years, we have accumulated evidence that HGF is an essential conductor for embryogenesis and tissue regeneration in various types of organs. Furthermore, we found in the mid-1990s that stroma-derived HGF is a major contributor to cancer invasion at least in vitro. Based on this background, we prepared NK4 as an antagonist of HGF: NK4 inhibits HGF-mediated MET tyrosine phosphorylation by competing with HGF for binding to MET. In vivo, NK4 treatments produced the anti-tumor outcomes in mice bearing distinct types of malignant cancers, associated with the loss in MET activation. There are now numerous reports showing that HGF-antagonists and MET-inhibitors are logical for inhibiting tumor growth and metastasis. Additionally, NK4 exerts anti-angiogenic effects, partly through perlecan-dependent cascades. This paper focuses on the chronology and significance of HGF-antagonisms in anti-tumor researches, with an interest in NK4 discovery. Tumor HGF–MET axis is now critical for drug resistance and cancer stem cell maintenance. Thus, oncologists cannot ignore this cascade for the future success of anti-metastatic therapy.

MicroRNA-1 and microRNA-499 downregulate the expression of the ets1 proto-oncogene in HepG2 cells

MicroRNAs may function to promote or suppress tumor development, depending on the cellular context. The important role of microRNAs in regulating molecular pathways underlying tumorigenesis has been emphasized in hepatocellular carcinoma (HCC). MicroRNAs regulate gene expression via post-transcriptional mechanisms by inhibiting translation or by degrading mRNA. In this study, we show that microRNA-1 (miR-1) and microRNA-499 (miR-499) are capable of repressing the expression of the ets1 proto-oncogene, which plays a fundamental role in the extracellular matrix (ECM) degradation, a process required for tumor cell invasion and migration. We used luciferase reporter assays to demonstrate that miR-1 and miR-499 target the 3' untranslated region (UTR) of ets1. Overexpression of miR-1 and miR-499 in HepG2 cells led to downregulation of ets1 mRNA and protein as assessed by quantitative reverse transcription PCR and western blot analysis. Furthermore, overexpression of miR-1 and miR-499 inhibited the invasion and migration of HepG2 cells in matrigel invasion and transwell migration assays, respectively. These results suggest that miR-1 and miR-499 may play an important role in the pathogenesis of HCC by regulating ets1.

Zinc finger protein 267 is up-regulated in hepatocellular carcinoma and promotes tumor cell proliferation and migration

Zinc finger protein 267 (ZNF267) belongs to the family of Kruppel-like transcription factors, which regulates diverse biological processes that include development, proliferation, and differentiation. We have previously demonstrated that ZNF267 mRNA is up-regulated in liver cirrhosis, which is the main risk factor for hepatocellular carcinoma (HCC). Here, we analyzed the expression of ZNF267 in human HCC cells and tissue specimens and found a significant up-regulation compared to primary human hepatocytes and corresponding non-tumorous liver tissue. Over-expression of the transcription factor Ets-1 further enhanced ZNF267 expression, and reporter gene assays revealed that mutation of the Ets-1 binding site to the ZNF267 promotor markedly inhibited ZNF267 promotor activity. Hypoxic conditions induced Ets-1 in HCC cells via HIF1alpha activation, and hypoxia induced ZNF267 expression while HIF1alpha inhibition significantly reduced both hypoxia-induced as well as basal ZNF267 expression in HCC cells. It is known that hypoxic conditions in tumorous tissues induce the formation of reactive oxygen species (ROS), and ROS have been identified as important factor in the regulation of Ets-1 expression in tumor cells. Here, we found that ROS induction induced and ROS scavenging reduced ZNF267 expression in HCC cells, respectively. Loss and gain of function analysis applying siRNA directed against ZNF267 or transient transfection revealed that ZNF267 promotes proliferation and migration of HCC cells in vitro. These findings indicate Ets-1 and HIF1alpha as critical regulators of basal and hypoxia- or ROS-induced ZNF267 expression in HCC, and further suggest that the pro-tumorigenic effect of these factors is at least in part mediated via increased ZNF267 expression in HCC. Since ZNF267 is already elevated in cirrhosis, ZNF267 appears as promising target for both prevention as well as treatment of HCC in patients with chronic liver disease.

Molecular magnetic resonance imaging approaches used to aid in the understanding of the tissue regeneration marker Met in vivo: implications for tissue engineering

The levels of Met, a tyrosine kinase receptor for the hepatocyte growth factor or scatter factor, are elevated during tissue regeneration, and can be used to assess tissue regeneration associated with engineered tissue grafts. This study involved the development and assessment of a novel magnetic resonance imaging (MRI) molecular probe for the in vivo detection of Met in an experimental rodent (rat) model of disease (C6 glioma). The implication of using these probes in tissue engineering is discussed. The molecular targeting agent we used in our study incorporated a magnetite-based dextran-coated nanoparticle backbone covalently bound to an anti-Met antibody. We used molecular MRI with an anti-Met probe to detect in vivo Met levels as a molecular marker for gliomas. Tumor regions were compared to normal tissue, and found to significantly (p < 0.05) decrease MR signal intensity and T(2) relaxation in tumors. Nonimmune nonspecific normal rat IgG coupled to the dextran-coated nanoparticles was used as a control. Met levels in tumor tissues were confirmed in Western blots. Based on our results, in vivo evaluation of tissue regeneration using molecular MRI is possible in tissue engineering applications.

MicroRNA-193b regulates proliferation, migration and invasion in human hepatocellular carcinoma cells

BACKGROUND AND AIMS

Recently, some miRNAs have been reported to be connected closely with the development of human hepatocellular carcinoma. However, the functions of these miRNAs in HCC remain largely undefined.

METHODS

The expression profiles of miR-193b were compared between HCC tissues and adjacent normal liver tissues using qRT-PCR method. This method was also be used to screen the potential target genes of miR-193b. A luciferase reporter assay was conducted to confirm target association. Finally, the functional effect of miR-193b in hepatoma cells was examined further.

RESULTS

miR-193b was significantly down-regulated in most of the HCC tissues compared to the matching non-tumoural liver tissues. Furthermore, ectopic expression of miR-193b dramatically suppressed the ability of hepatoma cells to form colonies in vitro and to develop tumours in nude mice. CCND1 and ETS1 were revealed to be regulated by miR-193b directly. By regulating the expressions of these oncogenes, miR-193b induced cell cycle arrest and inhibited the invasion and migration of hepatoma cells.

CONCLUSIONS

miR-193b may function as a tumour suppressor in the development of HCC by acting on multiple tumourigenic pathways.

Challenge and hope in radiotherapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most critical global health issues. With frequent association of viral liver disease, HCC is highly complex, harboring both cancer and chronic liver disease. The tumor stage and underlying liver function are both major determinants of the treatment selection as well as prognosis in HCC patients, thus allowing no more than a 20% chance for potentially curative therapies. Radiotherapy technology has been evolved remarkably during the past decade, and radiation can be precisely delivered, thereby permitting higher doses to the tumour and reduced doses to surrounding normal tissues. There has been increasing interest in the merits of radiotherapy in HCC over the past few years, as indicated by a Pub Med search. Radiotherapy has been used as the definitive therapy with curative intent in early stage tumours. It has been used also in combination with TACE for intermediate stage tumours. In locally advanced tumours, radiotherapy has been combined with systemic agents. Despite its efficacy, radiotherapy has not yet been incorporated into the standard management guidelines of HCC. The lack of high evidence level data, especially randomized controlled trials, has posed an obstacle in including radiotherapy into the routine treatment schema of HCC. Therefore, well-designed prospective studies are strongly recommended using developing technology for radiotherapy alone or combination therapies. Also, many issues such as the optimal dose-fractionation, intra- or extrahepatic metastasis after radiotherapy, and radiation-induced hepatic dysfunction remain to be solved. In this review, current status of radiotherapy for HCC will be discussed with regard to technical consideration and combination strategy. The limitation and future perspectives will also be discussed.

c-Met-targeted RNA interference inhibits growth and metastasis of glioma U251 cells in vitro

Angiogenesis plays an essential role in tumor growth and metastasis and is a promising target for cancer therapy. c-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor (HGF), are critical in cellular proliferation, motility, invasion, and angiogenesis. The present study was designed to determine the role of c-Met in growth and metastasis of glioma U251 cells using RNA interference (RNAi) technology in vitro. We constructed three kinds of shRNA expression vectors aiming at the c-Met gene, then transfected them into glioma U251 cells by lipofectamine(TM) 2000. The level of c-Met mRNA was investigated by real-time polymerse chain reaction (RT-PCR). The protein expression of c-Met was observed by immunofluoresence staining and western blotting. U251 cell growth and adherence was detected by methyl thiazole tetrazolium assay. The apoptosis of U251 cells was examined with a flow cytometer. The adherence, invasion, and in vitro angiogenesis assays of U251 cells were done. We got three kinds of c-Met specific shRNA expression vectors which could efficiently inhibit the growth and metastasis of U251 cells and the expression of c-Met in U251 cells. RT-PCR, immunofluoresence staining and western blotting showed that inhibition rate for c-Met expression was up to 90%, 79% and 85%, respectively. The expression of c-Met can be inhibited by RNA interference in U251 cells, which can inhibit the growth and metastasis of U251 cell and induce cell apoptosis. These results indicate that RNAi of c-Met can be an effective antiangiogenic strategy for glioma.

KAI1/CD82 suppresses hepatocyte growth factor-induced migration of hepatoma cells via upregulation of Sprouty2

We conducted a study concerning the suppressive mechanism of KAI1/CD82 on hepatoma cell metastasis. Hepatocyte growth factor (HGF) induces the migration of hepatoma cells through activation of cellular sphingosine kinase 1 (SphK1). Adenovirus-mediated gene transfer of KAI1 (Ad-KAI1) downregulates the SphK1 expression and suppresses the HGF-induced migration of SMMC-7721 human hepatocellcular carcinoma cells. Overexpression of KAI1/CD82 significantly elevates Sprouty2 at the protein level. Ablation of Sprouty2 with RNA interference can block the KAI1/CD82-induced suppression of hepatoma cell migration and downregulation of SphK1 expression. It is demonstrated that KAI1/CD82 suppresses HGF-induced migration of hepatoma cells via upregulation of Sprouty2.

Matrix metalloproteinase-1 promotes breast cancer angiogenesis and osteolysis in a novel in vivo model

Matrix metalloproteinase-1 (MMP-1) is critical for mediating breast cancer metastasis to bone. We investigated the role of MMP-1 in breast cancer invasion of soft tissues and bone using human MDA MB-231 breast cancer cells stably transfected with shRNAs against MMP-1 and a novel murine model of bone invasion. MMP-1 produced by breast cancer cells with control shRNA facilitated invasion of tumors into soft tissue in vivo, which correlated with enhanced blood vessel formation at the invasive edge, compared to tumors with silenced MMP-1 expression. Tumors expressing MMP-1 were also associated with osteolysis in vivo, whereas tumors with inhibited MMP-1 levels were not. Additionally, tumor-secreted MMP-1 activated bone-resorbing osteoclasts in vitro. Together, these data suggest a mechanism for MMP-1 in the activation of osteoclasts in vivo. We conclude that breast cancer-derived MMP-1 mediates invasion through soft tissues and bone via mechanisms involving matrix degradation, angiogenesis, and osteoclast activation.

Involvement of Egr-1 in HGF-induced elevation of the human 5alpha-R1 gene in human hepatocellular carcinoma cells

Steroid 5alpha-reductase 1 (5alpha-R1), a key enzyme in the conversion of steroids into their respective 5alpha-reduced derivatives, plays a key role in some hormone-dependent tumours and is abundant in the liver, although it is also widely distributed throughout the body. HGF (hepatocyte growth factor) is a pleiotropic cytokine/growth factor involved in the progression of hepatocellular carcinoma. In the present paper, we report the stimulatory effect of HGF on human 5alpha-R1 transcription in hepatocellular carcinoma cells. Pre-treatment with actinomycin D or cycloheximide blocked the up-regulation of 5alpha-R1 mRNA expression by HGF, indicating that the increased level of 5alpha-R1 mRNA expression is regulated by transcriptional activation and was dependent on de novo protein synthesis. Functional analysis of the 5'-flanking region of the 5alpha-R1 gene by transfection analysis showed that the -79 to -50 region functioned as the HGF-responsive region. Mutagenesis and electrophoretic mobility-shift assays demonstrated that induction of 5a-R1 by HGF is mediated by an Egr-1 (early growth-response gene 1)-binding site at -60/-54. In addition, overexpression of Egr-1 was sufficient to transactivate 5alpha-R1 promoter activity, and knockdown of Egr-1 with gene-specific small interfering RNA resulted in inhibition of HGF-induced up-regulation of endogenous 5alpha-R1 expression. These data provide the first evidence that HGF stimulates 5alpha-R1 expression through up-regulation of the transcription factor Egr-1, thus suggesting the possibility that regulation of steroid metabolism by HGF represents a mechanism for high risk of hepatocellular carcinogenesis in males.

Deletion of the Met tyrosine kinase in liver progenitor oval cells increases sensitivity to apoptosis in vitro

The hepatocyte growth factor (HGF)/Met signaling system is essential for liver development, homeostasis, and function. In this study, we took advantage of a liver-specific, Met-conditional knockout mouse generated in our laboratory to address the molecular mechanisms of HGF/Met signaling in adult liver progenitor cell (oval cell) biology. For this purpose, we isolated oval cells from 3,5-diethoxycarbonyl-1,4-dihydro-collidine-treated Met(flx/flx) mice and established oval cell-derived cell lines that carried either functional (Met(flx/flx)) or a nonfunctional (Met(-/-)) met gene using virus-mediated Cre-loxP recombination. Oval cells lacking Met tyrosine kinase activity displayed neither Met phosphorylation nor activation of downstream targets and were refractory to HGF stimulation. Although Met(-/-) and Met(flx/flx) cells proliferated at similar rates under 10% serum, Met-deficient cells demonstrated decreased cell viability and were more prone to apoptosis when challenged with either serum starvation or the pro-apoptotic cytokine transforming growth factor-beta. Treatment with HGF reduced transforming growth factor-beta-mediated cell death in Met(flx/flx) but not Met(-/-) cells. Importantly, Met(flx/flx) and Met(-/-) cells both constitutively expressed hgf, and conditioned medium from serum-starved oval cells exhibited anti-apoptotic activity in Met(flx/flx) cells. Furthermore, serum-starved Met(flx/flx) cells showed persistent activation of the Met tyrosine kinase, suggesting HGF/Met autocrine regulation. In conclusion, these data reveal a critical, functional role for Met in oval cell survival through an autocrine mechanism.

Extravasation and homing mechanisms in multiple myeloma

Multiple myeloma (MM) is a malignant B-cell disorder characterized by a monoclonal expansion of plasma cells (PC) in the bone marrow (BM). During the main course of disease evolution, MM cells depend on the BM microenvironment for their growth and survival. Reciprocal interactions between MM cells and the BM mediate not only MM cell growth, but also protect them against apoptosis and cause bone disease and angiogenesis. A striking feature of MM represents the predominant localization and retention of MM cells in the BM. Although BM PC indeed represent the main neoplastic cell type, small numbers of MM cells can also be detected in the peripheral blood circulation. It can be assumed that these circulating cells represent the tumour-spreading component of the disease. This implicates that MM cells have the capacity to (re)circulate, to extravasate and to migrate to the BM (homing). In analogy to the migration and homing of normal leucocytes, the BM homing of MM cells is mediated by a multistep process of extravasation with adhesion to the endothelium, invasion of the subendothelial basement membrane, followed by further migration within the stroma, mediated by chemotactic factors. At the end stage of disease, MM cells are thought to develop autocrine growth supporting loops that enable them to survive and proliferate in the absence of the BM microenvironment and to become stroma-independent. In this stage, the number of circulating cells increases and growth at extramedullary sites can occur, associated with alteration in adhesion molecule and chemokine receptor expression. This review summarizes the recent progress in the study of the extravasation and homing mechanisms of MM cells.

Effects of hepatocyte growth factor on glutathione synthesis, growth, and apoptosis is cell density-dependent

Hepatocyte growth factor (HGF) is a potent hepatocyte mitogen that exerts opposing effects depending on cell density. Glutathione (GSH) is the main non-protein thiol in mammalian cells that modulates growth and apoptosis. We previously showed that GSH level is inversely related to cell density of hepatocytes and is positively related to growth. Our current work examined whether HGF can modulate GSH synthesis in a cell density-dependent manner and how GSH in turn influence HGF's effects. We found HGF treatment of H4IIE cells increased cell GSH levels only under subconfluent density. The increase in cell GSH under low density was due to increased transcription of GSH synthetic enzymes. This correlated with increased protein levels and nuclear binding activities of c-Jun, c-Fos, p65, p50, Nrf1 and Nrf2 to the promoter region of these genes. HGF acts as a mitogen in H4IIE cells under low cell density and protects against tumor necrosis factor alpha (TNFalpha)-induced apoptosis by limiting JNK activation. However, HGF is pro-apoptotic under high cell density and exacerbates TNFalpha-induced apoptosis by potentiating JNK activation. The increase in cell GSH under low cell density allows HGF to exert its full mitogenic effect but is not necessary for its anti-apoptotic effect.

Osteoblasts promote migration and invasion of myeloma cells through upregulation of matrix metalloproteinases, urokinase plasminogen activator, hepatocyte growth factor and activation of p38 MAPK

Formation of osteolytic lesions is a key pathophysiological feature in multiple myeloma and results from the interaction of myeloma cells with the bone marrow microenvironment. Matrix metalloproteinases (MMPs) and plasmin may be involved in bone destruction, but their precise roles have not been clarified. Furthermore, the impact of osteoblast-related alterations on myeloma bone disease is not well understood. We addressed this complex phenomenon by applying a coculture system between myeloma cells and osteoblasts. Osteoblasts induced expression of MMP-1 and upregulated the expression of MMP-2, urokinase plasminogen activator (uPA) and hepatocyte growth factor (HGF) in myeloma cells. In turn, interaction with myeloma cells led to abundant MMP-1 expression in osteoblasts. Because MMP-1 degrades collagen, its upregulation might represent an essential mechanism contributing to bone destruction. Cocultures using primary myeloma cells confirmed the results obtained with cell lines. The mechanisms responsible for MMP-1 upregulation are mediated by both membrane-bound and soluble factors, and involve the p38 mitogen-activated protein kinase (MAPK) pathway. The interaction with osteoblasts enhances the capability of myeloma cells to transmigrate and invade through Matrigel or type I collagen. Using appropriate inhibitors, we provide evidence that these processes involve MMPs, uPA, HGF and activation of p38 MAPK.

Sequential action of Ets-1 and Sp1 in the activation of the human beta-1,4-galactosyltransferase V gene involved in abnormal glycosylation characteristic of cancer cells

Malignant transformation is associated with increased gene expression of beta-1,4-galactosyltransferase (beta-1,4-GalT) V, which contributes to the biosynthesis of highly branched N-linked oligosaccharides characteristic of cancer cells. Our previous study showed that expression of the human beta-1,4-GalT V gene is regulated by Sp1 (Sato, T., and Furukawa, K. (2004) J. Biol. Chem. 279, 39574-39583), and a subsequent study showed that the gene expression is also activated by Ets-1, a product of the oncogene (Sato, T., and Furukawa, K. (2005) Glycoconj. J. 22, 365). Herein we report the mechanism of beta-1,4-GalT V gene activation by these transcription factors. The gene expression and promoter activity of beta-1,4-GalT V increased when the ets-1 cDNA was transfected into A549 cells, which contain a small amount of Ets-1, but decreased dramatically when the dominant-negative ets-1 cDNA was transfected into HepG2 cells, which contain a large amount of Ets-1. Luciferase assays using deletion constructs of the beta-1,4-GalT V gene promoter showed that promoter region -116 to +22 is critical for the transcriptional activation of the gene by Ets-1. Despite the presence of one Ets-1-binding site, which overlapped the Sp1-binding site, electrophoretic mobility shift assays showed that the region bound preferentially to Sp1 rather than to Ets-1. To solve this problem, we examined the transcriptional regulation of the human Sp1 gene by Ets-1 and found that the gene expression and promoter activity of Sp1 are regulated by Ets-1 in cancer cells. Functional analyses of two Ets-1-binding sites in the Sp1 gene promoter showed that only Ets-1-binding site -413 to -404 is involved in the activation of the gene by Ets-1. These results indicate that Ets-1 enhances expression of the beta-1,4-GalT V gene through activation of the Sp1 gene in cancer cells.

c-Met antisense oligodeoxynucleotides as a novel therapeutic agent for glioma: in vitro and in vivo studies of uptake, effects, and toxicity

BACKGROUND

c-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor, are critical in cellular proliferation, motility, and invasion and are known to be overexpressed in gliomas. The aim of our study was to investigate the uptake and effects of c-Met antisense oligodeoxynucleotides (ASODNs) on rat and human glioma cells in vitro and the uptake and toxicity of these nucleotides in rat carcinomatosis and brain tumor models.

MATERIALS AND METHODS

The three human cell lines (U87, BT325, SHG44) and the C6 rat glioma cell line were cultured. To study the uptake of oligodeoxynucleotides (ODNs) by glioma cells in vitro, cultured glioma cells readily incorporated caroboxyfluorescein-5-succimidyl ester (FAM) labeled phosphorothioate oligodeoxynucleotides, as demonstrated by immunofluorescence microscopy and flow cytometry. To study the effect of ASODNs treatment on c-Met expression in vitro, Expression of c-Met was assessed by immunofluorescence microscopy and reverse transcriptase polymerase chain reaction (RT-PCR) analysis. For animal studies of ODNs toxicity and uptake, eight rats underwent placement of cisternal catheters, under general anesthesia. Four rats were given 24 mug FAM-labeled ASODNs while the others were given a saline control injection. After a 24 h observation period, rats were sacrificed by barbiturate overdose, and their brains were studied.

RESULTS

For all cell lines, fluorescence was seen to increase with increasing ASODNs concentration. Cells treated in similar fashion were also analyzed by flow cytometry to graphically illustrate the differing fluorescence. Multiple glioma cell lines were tested, with similar results. c-Met ASODNs was found to be successfully incorporated from the media into cultured human glioma cells, even at concentrations as low as 2 muM. In addition, maintenance of the pH-dependent green fluorescence color, as seen by immunofluorescence microscopy and by using flow cytometry, indicated that the FAM was not contained within lysosomes. Immunofluorescence microscopy and RT-PCR analysis showed decreases in c-Met expression with oligodeoxynucleotides treatment. Uptake into tumor cells was also demonstrated in vivo, with no detectable toxicity at concentrations exceeding expected therapeutic levels.

CONCLUSION

These data are encouraging for further study of c-Met antisense oligodeoxynucleotides as a therapeutic modality for glioma.

Effect of hepatocyte growth factor on methionine adenosyltransferase genes and growth is cell density-dependent in HepG2 cells

Hepatocyte growth factor (HGF) is a potent hepatocyte mitogen but its effect in liver cancer is conflicting. Methionine adenosyltransferase (MAT) is an essential enzyme encoded by two genes (MAT1A and MAT2A), while a third gene (MAT2beta) encodes for a subunit that regulates the MAT2A-encoded isoenzyme. MAT1A is silenced while MAT2A and MAT2beta are induced in hepatocellular carcinoma (HCC). The current work examined expression of HGF/c-met in HCC and whether HGF regulates MAT genes and growth in HepG2 cells. We found the mRNA levels of HGF and c-met are markedly increased in HCC. To study the influence of cell density, HepG2 cells were plated under high-density (HD) or low-density (LD) and treated with HGF (10 ng/ml). Cell density had a dramatic effect on MAT1A expression, being nearly undetectable at LD to a ninefold induction under HD. Cell density also determined the effect of HGF. At HD, HGF increased the mRNA levels of p21 and p27, while lowering the levels of MAT genes, cyclin A, and c-met. At LD, HGF increased the mRNA levels of cyclin A, MAT2A, MAT2beta, and c-met. Consistently, HGF inhibits growth under HD but stimulates growth under LD. HGF induced sustained high ERK activation under HD as compared to LD. In summary, HGF induces genes favoring growth and is mitogenic when HepG2 cells are plated under LD; however, the opposite occurs under HD. This involves cell density-dependent differences in HGF-induced ERK activation. This may explain why HGF is mitogenic only when there is loss of cell-cell contact in vivo.

C-Met antisense oligodeoxynucleotide inhibits growth of glioma cells

BACKGROUND

C-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor, are critical in cellular proliferation, motility, and invasion and are known to be overexpressed in gliomas. The aim of our study was therefore to investigate the effect of transfected caroboxyfluorescein-5-succimidyl ester (FAM)-labeled c-Met antisense oligonucleotide (ASODN) on growth of glioma cells.

METHODS

Conjugated FAM-labeled c-Met ASODN was encapsulated by LIPOFECTAMINE PLUS Reagent and then added into the human glioma cell line U251. Cultured cells were divided into 5 groups: control group, 500 nmol/L nonsense oligonucleotide (NSODN) group, 250 nmol/L ASODN group, 500 nmol/L ASODN group, and 750 nmol/L ASODN group. The intracellular distribution of c-Met ASODN was observed with fluorescence microscopy; cell growth was detected by methyl thiazole tetrazolium assay. The apoptosis of U251 cells was also examined with a flow cytometer. Semiquantitative reverse transcriptase polymerase chain reaction and Western blot examinations were carried for expression of c-Met messenger RNA (mRNA) and protein.

RESULTS

The blue fluorescence was seen in the cytoplast and nuclei of cells of FAM-labeled c-Met ASODN groups with fluorescence microscopy after the cells were treated with FAM-labeled c-Met ASODN-LIPOFECTAMINE PLUS Reagent complex for 3 hours. Antisense (AS) oligonucleotide caused a statistically significant reduction of cell viability (P < .05), whereas NSODN had no such changes. The cell growth was also significantly inhibited by ASODN (P < .05). After transfection, 250, 500, and 750 nmol/L ASODN induced significant apoptotic response, about 4.67% +/- 2.86%, 8.65% +/- 3.18%, and 12.76% +/- 3.15% for 24 hours (P < .05) and 7.79% +/- 1.92%, 11.43% +/- 1.54%, and 15.78% +/- 1.86% for 48 hours (P < .01), respectively. However, 500 nmol/L NSODN did not induce any significant apoptotic response until 48 hours after transfection (P > .05). A significant loss of c-Met mRNA was presented in ASODN-treated cells, and this was not seen in treatment with NSODN. Protein level was significantly decreased 48 hours after c-Met ASODN transfected.

CONCLUSIONS

Antisense oligonucleotide targeting c-Met can be identified as a most potent AS compound, which can inhibit cell growth and induce cell apoptosis. This provides evidence that c-Met plays a role in tumor progression of glioma by acting as an oncogene and suggests that c-Met ASODN may provide a novel approach to therapy for human glioma.

Dysregulation of growth factor signaling in human hepatocellular carcinoma

Dysregulation of pleiotropic growth factors, receptors and their downstream signaling pathway components represent a central protumorigenic principle in human hepatocarcinogenesis. Especially the Insulin-like Growth Factor/IGF-1 receptor (IGF/IGF-1R), Hepatocyte Growth Factor (HGF/MET), Wingless (Wnt/beta-catenin/FZD), Transforming Growth Factor alpha/Epidermal Growth Factor receptor (TGFalpha/EGFR) and Transforming Growth Factor beta (TGFbeta/TbetaR) pathways contribute to proliferation, antiapoptosis and invasive behavior of tumor cells. This review focuses on the relevant alterations in these pathways identified in human human hepatocellular carcinomas (HCCs). Resultant functional effects are modulated by multiple cross-talks between the different signaling pathways and additional tumor-relevant factors, such as cyclooxygenase-2 and p53. Several specific strategies are currently under development such as receptor kinase inhibitors, neutralizing antibodies and antagonistic proteins, which may improve the systemic treatment of human HCCs.

Arsenic trioxide reduces the invasive and metastatic properties of nasopharyngeal carcinoma cells in vitro

Nasopharyngeal carcinoma (NPC) is notorious for the metastases, which are in close association with Epstein-Barr virus-encoded latent membrane protein 1 (LMP1). Arsenic trioxide (As2O3) has been shown to induce apoptosis and differentiation in NPC xenografts. Then, can it repress the cancer cells' metastasis potential? To elucidate this issue, the present study was performed. LMP1-negative cell line HNE1 and LMP1-positive cell line HNE1-LMP1 were used as in vitro model. Cells (1 x 10(5)/mL) were cultured with or without 3 microM As2O3 for 48 h. Then the survival cells were collected to investigate their potential of colony formation, attachment, invasion, and migration. Both confocal immunofluorescence staining and Western blot were used to detect the changes of LMP1 expression. The changes of MMP-9 were examined by RT-PCR assay and Western blot. The results were as follow: i) the colony formation inhibition rate (75.41 +/- 3.9% in HNE1-LMP1 cells vs 37.89 +/- 4.9% in HNE1 cells), the rate of attachment (HNE1-LMP1 vs HNE1: 56.40 +/- 3.5 vs 65.87 +/- 5.9%), the invasion inhibitory rate (HNE1-LMP1 vs HNE1: 56.50 +/- 3.7 and 27.91 +/- 2.1%), and the migration inhibitory rate (HNE1-LMP1 vs HNE1: 48.70 +/- 3.9 vs 29.19 +/- 6.27%) were all significantly different between the two cell lines (P < 0.01). ii) LMP1 was down-regulated in As2O3-treated HNE1-LMP1 cells. iii) The reduction of MMP-9 was found in As2O3-treated groups, more evident in HNE1-LMP1 cells. Thus, we conclude that As2O3 can reduce metastasis potential of NPC cells, involving inhibition of MMP-9 expression. LMP1 were also reduced in this process and seemed to enhance anti-metastasis activity of As2O3.

In vitro and in vivo potentiating the cytotoxic effect of radiation on human U251 gliomas by the c-Met antisense oligodeoxynucleotides

C-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor (HGF), are critical in cellular proliferation, motility, and invasion, and are known to be overexpressed in gliomas, which are related to the repair of damaged DNA. In this study, we investigated both in vitro and in vivo whether inhibition of the c-Met gene by antisense oligonucleotides (ODNs) enhances the cytotoxic effect of radiation on human U251 gliomas. A volume of 100 nM of c-Met antisense ODNs inhibited the level of mRNA by more than 95% and reduced the protein expression by about 70%. Treatment of human U251 glioma cells with 100 nM of c-Met antisense ODNs significantly enhanced the radiation-induced cell kill compared to control cells, and cells treated with nonsense ODNs. When the glioma cells were implanted in the cisterna magna of nude mice followed by treatment with c-Met antisense ODNs, the survival time of the nude mice was markedly prolonged compared to that of the untreated group (P < 0.001, logrank test). In addition, the combination of antisense ODNs and irradiation extended the survival time of the glioma-bearing nude mice much longer than could be achieved with radiation alone (P < 0.0001, logrank test). These results suggest that inhibition of c-Met can be expected to serve as a novel potentiator for radiation therapy in human U251 gliomas.

Hepatocyte growth factor and inducible nitric oxide synthase are involved in multidrug resistance-induced angiogenesis in hepatocellular carcinoma cell lines

Based on literature, it is possible to hypothesize that multidrug resistance (MDR) and angiogenic phenotypes are linked to each other in human liver cancer cells. Our goal is to assess whether MDR cells trigger angiogenesis and to study the possible molecular mechanisms involved. Conditioned medium from parental drug-sensitive P5 cells (P5-CM) and MDR-positive P1(0.5) cells [P1(0.5)-CM] stimulated human umbilical vein endothelial cells (HUVEC) survival, proliferation, migration, and microtubular structure formation, but P1(0.5)-CM had a significantly greater effect than P5-CM. Cell implants were done in the rabbit avascular cornea to measure angiogenesis in vivo: P1(0.5) cells induced an important neovascular response in rabbit cornea after 1 week, whereas P5 cells had no effect. P1(0.5) and P5 cells produced vascular endothelial growth factor, but only P1(0.5) secreted hepatocyte growth factor (HGF) into the medium, and small interfering RNA specific for MDR1 clearly reduced HGF production in P1(0.5) cells. The transcription factor Ets-1 and the HGF receptor c-Met were up-regulated in P1(0.5) cells and in HUVEC cultured in P1(0.5)-CM. Inducible nitric oxide synthase (iNOS) seemed to play a major role in the proangiogenic effect of P1(0.5), and its inhibition by 1400W blunted the capacity of P1(0.5) cells to stimulate HUVEC proliferation, migration, and Ets-1 expression. In conclusion, these data show that development of MDR and angiogenic phenotypes are linked to each other in MDR cells. HGF production, Ets-1 and c-Met up-regulation, and iNOS expression can be part of the molecular mechanisms that enhance the angiogenic activity of the MDR-positive hepatocellular carcinoma cell line.

Inhibitory effect of luteolin on hepatocyte growth factor/scatter factor-induced HepG2 cell invasion involving both MAPK/ERKs and PI3K–Akt pathways

Hepatocyte growth factor (HGF), also known as scatter factor (SF), and its receptor, the c-Met tyrosine kinase, play roles in cancer invasion and metastasis in a wide variety of tumor cells. Clinical observations suggest that HGF can promote metastasis of hepatoma cells while stimulating tumor invasiveness. We use HGF as an invasive inducer of human hepatoma HepG2 cells to investigate the effect of flavonoids on anti-invasion. In our preliminary study, we investigated the effect of flavonoids including luteolin, quercetin, baicalein, genistein, taxifolin and catechin on HGF-mediated migration and invasion of HepG2 cells. We found that luteolin presented the most potent potential on anti-migration and anti-invasion by Boyden chamber assay. Furthermore, luteolin inhibited HGF-induced cell scattering and cytoskeleton change such as filopodia and lamellipodia was determined by both phase-contrast and fluorescence microscopy studies. In addition, Western blotting and immunoprecipitation were performed to confirm luteolin suppressed the phosphorylation of c-Met, the membrane receptor of HGF, as well as ERK1/2 and Akt, but not JNK1/2, which is activated by HGF. Our investigation demonstrated that luteolin similar to PD98059, which acts as a specific inhibitor of MEK, an up stream kinase regulating ERK1/2, and wortmannin, a PI3K inhibitor, inhibited the invasiveness induced by HGF. In conclusion, the luteolin inhibited HGF-induced HepG2 cell invasion involving both MAPK/ERKs and PI3K-Akt pathways.

Extracellular matrix remodeling in hepatocellular carcinoma: effects of soil on seed?

Extracellular matrix plays two-edged roles, inhibitor and promoter, in the carcinogenesis and progression of hepatocellular carcinoma. On the one hand, extracellular matrix provides the survival signals, and controls the proliferation, differentiation and metastasis of hepatocellular carcinoma. On the other hand, hepatocarcinoma cells create a permissive soil by extracellular matrix remodeling, result in high proliferation, low differentiation, apoptosis block, invasion and metastasis. These malignant phenotypes are related with the change of the capsule around hepatocarcinoma cells that composed by collagens I and IV, the cell-extracellular matrix interaction induced by laminin and its receptor-integrins, and the degradation of ECM which is regulated by proteolytic enzymes and their inhibitor. Thus, normalization of ECM may represent a novel therapeutic strategy for hepatocarcinoma cells.