Blockage of HGF/c-Met system by gene therapy (adenovirus-mediated NK4 gene) suppresses hepatocellular carcinoma in mice

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Angiogenesis in the Transplanted Donor Graft After Living-Donor Liver Transplantation

BACKGROUND

There is no direct evidence for the role of angiogenesis in liver regeneration in humans. This study aimed to determine whether angiogenesis is involved in the regeneration of transplanted donor grafts in human living-donor liver transplantation (LDLT) and to examine the impact of donor graft volume on angiogenesis.

METHODS

Clinical data and liver tissue characteristics were analyzed in 4 patients who received adult-to-adult LDLT with dual left lobe grafts from 2 living donors. Liver tissues from transplanted donor grafts were obtained and immunohistochemically examined at 3 to 4 weeks after transplantation using the endothelial marker Ki67+ and CD31+.

RESULTS

All recipients showed recovery of normal liver function and a significant increase in the volume of engrafted left lobes after transplantation. Immunohistochemistry showed a remarkable increase in Ki67+ single hepatocyte proliferation, implying the role of hepatocytes in liver reconstitution, and a high density of blood vessels and proliferative endothelium, suggesting in vivo angiogenesis. Furthermore, we found that Ki67+ nuclei in CD31+ sinusoidal endothelial cells were higher in recipients with smaller donor grafts than in those with larger donor grafts.

CONCLUSIONS

Our results suggested that angiogenesis is involved in the regeneration of transplanted liver in humans in inverse proportion to the donor graft volume.

MCU-dependent mitochondrial Ca2+ inhibits NAD+/SIRT3/SOD2 pathway to promote ROS production and metastasis of HCC cells

Mitochondrial Ca²⁺ signaling, which is strongly dependent on the mitochondrial Ca²⁺ uniporter (MCU) complex, has a series of key roles in physiopathological processes, including energy metabolism, reactive oxygen species (ROS) production and cell apoptosis. However, a mechanistic understanding of how the mitochondrial Ca²⁺ signaling is remodeled and its functional roles remains greatly limited in cancers, especially in hepatocellular carcinoma. Here we demonstrated that the MCU complex was dysregulated in hepatocellular carcinoma (HCC) cells and significantly correlated with metastasis and poor prognosis of HCC patients. Upregulation of MCU clearly enhanced the Ca²⁺ uptake into mitochondria, which significantly promoted ROS production by downregulating nicotinamide adenine dinucleotide⁺ (NAD⁺)/reduced form of nicotinamide adenine dinucleotid (NADH) ratio and the NAD⁺-dependent deacetylase activity of sirtuin 3 to inhibit superoxide dismutase 2 (SOD2) activity. Moreover, our data indicated that the MCU-dependent mitochondrial Ca²⁺ uptake promotes matrix metalloproteinase-2 activity and cell motility by ROS-activated c-Jun N-terminal kinase pathway, and thus contributed to the increased ability of invasion and migration in vitro and intrahepatic and distal lung metastasis in vivo of HCC cells. In addition, treatment with the mitochondrial Ca²⁺-buffering protein parvalbumin significantly suppressed ROS production and the ability of HCC metastasis. Our study uncovers a mechanism that links the remodeling of mitochondrial Ca²⁺ homeostasis to ROS production, and provides evidence supporting a metastasis-promoting role for the MCU-dependent mitochondrial Ca²⁺ uptake in HCC. Our findings suggest that the mitochondrial Ca²⁺ uptake machinery may potentially be a novel therapeutic target for HCC metastasis.

The hepatocyte growth factor antagonist NK4 inhibits indoleamine-2,3-dioxygenase expression via the c-Met-phosphatidylinositol 3-kinase-AKT signaling pathway

Indoleamine-2,3-dioxygenase (IDO) is an immunosuppressive enzyme involved in tumor malignancy. However, the regulatory mechanism underlying its involvement remains largely uncharacterized. The present study aimed to investigate the hypothesis that NK4, an antagonist of hepatocyte growth factor (HGF), can regulate IDO and to characterize the signaling mechanism involved. Following successful transfection of the human ovarian cancer cell line SKOV-3 (which constitutively expresses IDO) with an NK4 expression vector, we observed that NK4 expression suppressed IDO expression; furthermore, NK4 expression did not suppress cancer cell growth in vitro [in the absence of natural killer (NK) cells], but did influence tumor growth in vivo. In addition, NK4 enhanced the sensitivity of cancer cells to NK cells in vitro and promoted NK cell accumulation in the tumor stroma in vivo. In an effort to clarify the mechanisms by which NK4 interacts with IDO, we performed investigations utilizing various biochemical inhibitors. The results of these investigations were as follows. First, c-Met (a receptor of HGF) tyrosine kinase inhibitor PHA-665752, and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 both suppress IDO expression. Second, enhanced expression of PTEN (a known tumor suppressor) via negative regulation within a PI3K-AKT pathway, inhibits IDO expression. Conversely, neither the MEK1/2 inhibitor U0126 nor the STAT3 inhibitor WP1066 affects IDO expression. These results suggest that NK4 inhibits IDO expression via a c-Met-PI3K-AKT signaling pathway.

Prognostic implication of serum hepatocyte growth factor in stage II/III breast cancer patients who received neoadjuvant chemotherapy

PURPOSE

In stage II/III breast cancer, neoadjuvant chemotherapy (NAC) is a standard treatment. Although several biomarkers are used to predict prognosis in breast cancer, there is no reliable predictive biomarker for NAC success. Recently, the hepatocyte growth factor (HGF) and cMet signaling pathway demonstrated to be involved in breast cancer tumor progression, and its potential as a biomarker is under active investigation. In this study, we assessed the potential of serum HGF as a prognostic biomarker for NAC efficacy.

METHODS

Venous blood samples were drawn from patients diagnosed with stage II/III breast cancer and treated with NAC in Seoul National University Hospital from August 2004 to November 2009. Serum HGF level was determined using an ELISA system. We reviewed the medical records of the patients and investigated the association of HGF level with patients' clinicopathologic characteristics.

RESULTS

A total of 121 female patients (median age = 45 years old) were included. Median level of HGF was 934 pg/ml (lower quartile: 772, upper quartile: 1145 pg/ml). Patients with higher HGF level than median value were significantly more likely to have clinically detectable regional node metastasis (p = 0.017, Fisher's exact test). Patients with complete and partial response according to the American Joint Committee on Cancer 7th Edition criteria tended to have higher HGF level (p = 0.105 by t test). Patients with an HGF level higher than the upper quartile value had longer relapse-free survival than the other patients (106 vs. 85 months, p = 0.008).

CONCLUSIONS

High serum HGF levels in breast cancer patients are associated with clinically detectable regional node metastasis and, paradoxically, with longer relapse-free survival in stage II/III breast cancer.

The expression of MACC1 and its role in the proliferation and apoptosis of salivary adenoid cystic carcinoma

BACKGROUND

The objective of this study was to investigate the relationship between metastasis-associated in colon cancer-1 and patient clinical characteristics. We also examined the role of metastasis-associated in colon cancer-1 in the proliferation and apoptosis in adenoid cystic carcinoma.

MATERIAL AND METHODS

Metastasis-associated in colon cancer-1 expression was analysed in 65 paraffin-embedded tissue specimens of salivary adenoid cystic carcinoma and 25 adjacent non-cancerous tissues by immunohistochemistry (IHC). We used RNA interference technology to silence metastasis-associated in colon cancer-1 expression in ACCM cells. Cell Counting Kit-8 tests, transwell experiments and flow cytometry were used to test the proliferation, cisplatin resistance, migration, invasion and apoptosis of ACCM cells.

RESULTS

Metastasis-associated in colon cancer-1 nuclear and cytoplasmic expression in salivary adenoid cystic carcinoma tissue was higher than in the adjacent normal salivary tissue. The expression level was closely associated with tumour histological grading, perineural invasion and surrounding tumour invasion. The downregulation of metastasis-associated in colon cancer-1 expression inhibited proliferation and induced apoptosis in ACCM cells. The knock-down of metastasis-associated in colon cancer-1 expression had no effect on migration, invasion and chemoresistance.

CONCLUSIONS

Metastasis-associated in colon cancer-1 may have an important role in tumour development in adenoid cystic carcinoma. Metastasis-associated in colon cancer-1 is a potential biomarker for adenoid cystic carcinoma.

Hepatic stellate cells: central modulators of hepatic carcinogenesis

Hepatocellular carcinoma (HCC) represents the second most common cause of cancer-related death worldwide, and is increasing in incidence. Currently, our therapeutic repertoire for the treatment of HCC is severely limited, and therefore effective new therapies are urgently required. Recently, there has been increasing interest focusing on the cellular and molecular interactions between cancer cells and their microenvironment. HCC represents a unique opportunity to study the relationship between a diseased stroma and promotion of carcinogenesis, as 90 % of HCCs arise in a cirrhotic liver. Hepatic stellate cells (HSC) are the major source of extracellular proteins during fibrogenesis, and may directly, or via secreted products, contribute to tumour initiation and progression. In this review we explore the complex cellular and molecular interplay between HSC biology and hepatocarcinogenesis. We focus on the molecular mechanisms by which HSC modulate HCC growth, immune cell evasion and angiogenesis. This is followed by a discussion of recent progress in the field in understanding the mechanistic crosstalk between HSC and HCC, and the pathways that are potentially amenable to therapeutic intervention. Furthermore, we summarise the exciting recent developments in strategies to target HSC specifically, and novel techniques to deliver pharmaceutical agents directly to HSC, potentially allowing tailored, cell-specific therapy for HCC.

Mesenchymal stem cell-based NK4 gene therapy in nude mice bearing gastric cancer xenografts

Mesenchymal stem cells (MSCs) have been recognized as promising delivery vehicles for gene therapy of tumors. Gastric cancer is the third leading cause of worldwide cancer mortality, and novel treatment modalities are urgently needed. NK4 is an antagonist of hepatocyte growth factor receptors (Met) which are often aberrantly activated in gastric cancer and thus represent a useful candidate for targeted therapies. This study investigated MSC-delivered NK4 gene therapy in nude mice bearing gastric cancer xenografts. MSCs were transduced with lentiviral vectors carrying NK4 complementary DNA or enhanced green fluorescent protein (GFP). Such transduction did not change the phenotype of MSCs. Gastric cancer xenografts were established in BALB/C nude mice, and the mice were treated with phosphate-buffered saline (PBS), MSCs-GFP, Lenti-NK4, or MSCs-NK4. The tropism of MSCs toward gastric cancer cells was determined by an in vitro migration assay using MKN45 cells, GES-1 cells and human fibroblasts and their presence in tumor xenografts. Tumor growth, tumor cell apoptosis and intratumoral microvessel density of tumor tissue were measured in nude mice bearing gastric cancer xenografts treated with PBS, MSCs-GFP, Lenti-NK4, or MSCs-NK4 via tail vein injection. The results showed that MSCs migrated preferably to gastric cancer cells in vitro. Systemic MSCs-NK4 injection significantly suppressed the growth of gastric cancer xenografts. MSCs-NK4 migrated and accumulated in tumor tissues after systemic injection. The microvessel density of tumor xenografts was decreased, and tumor cellular apoptosis was significantly induced in the mice treated with MSCs-NK4 compared to control mice. These findings demonstrate that MSC-based NK4 gene therapy can obviously inhibit the growth of gastric cancer xenografts, and MSCs are a better vehicle for NK4 gene therapy than lentiviral vectors. Further studies are warranted to explore the efficacy and safety of the MSC-based NK4 gene therapy in animals and cancer patients.

Blockage of CXCR2 suppresses tumor growth of intrahepatic cholangiocellular carcinoma

BACKGROUND/AIMS

Complete operative resection is the only approach to cure for intrahepatic cholangiocellular carcinoma (ICC), but the disease's prognosis is notably poor. A novel therapeutic approach is urgently required. CXC chemokine receptor 2 (CXCR2) has been associated with tumorigenesis and metastasis in human cancers. In this study, we investigated the suppressive effect of ICC growth by blocking CXCR2.

MATERIAL AND METHODS

The role of CXCR2 was estimated using the human ICC cell lines, RBE and SSP25. CXCR2 small interfering RNA (siRNA) and an antagonist (SB225002) were used to block CXCR2. Proliferation assays, migration assays, and invasion assays were performed to confirm the suppressive effect of blocking CXCR2. Subcutaneous SSP25 tumors were established in athymic nude mice, and the mice were given SB225002. The expression of CXCR2 in ICC was determined by immunohistochemical staining of 34 ICC specimens. We investigated the relationship between CXCR2 expression and prognosis in ICC.

RESULTS

The prognosis of patients who had higher CXCR2 expression in ICC was significantly poor (P = .004). CXCR2 siRNA treatment significantly suppressed CXCR2 expression in both RBE and SSP25. Cell proliferation, migration, and invasion were significantly suppressed by both CXCR2 siRNA and SB225002 compared with the control group. SB225002 also suppressed the growth of transplanted subcutaneous tumors (P = .02) CONCLUSION: Our results demonstrated that blocking CXCR2 clearly suppressed the development of ICC. Blocking CXCR2 may be a promising therapeutic approach for ICC.

Liver protective effect of ursodeoxycholic acid includes regulation of ADAM17 activity

BACKGROUND

Ursodeoxycholic acid (UDCA) is used to treat primary biliary cirrhosis, intrahepatic cholestasis, and other cholestatic conditions. Although much has been learned about the molecular basis of the disease pathophysiology, our understanding of the effects of UDCA remains unclear. Possibly underlying its cytoprotective, anti-apoptotic, anti-oxidative effects, UDCA was reported to regulate the expression of TNFα and other inflammatory cytokines. However, it is not known if this effect involves also modulation of ADAM family of metalloproteinases, which are responsible for release of ectodomains of inflammatory cytokines from the cell surface. We hypothesized that UDCA modulates ADAM17 activity, resulting in amelioration of cholestasis in a murine model of bile duct ligation (BDL).

METHODS

The effect of UDCA on ADAM17 activity was studied using the human liver hepatocellular carcinoma cell line HepG2. Untransfected cells or cells ectopically expressing human ADAM17 were cultured with or without UDCA and further activated using phorbol-12-myristate-13-acetate (PMA). The expression and release of ADAM17 substrates, TNFα, TGFα, and c-Met receptor (or its soluble form, sMet) were evaluated using ELISA and quantitative real-time (qRT) PCR. Immunoblotting analyses were conducted to evaluate expression and activation of ADAM17 as well as the level of ERK1/2 phosphorylation after UDCA treatment. The regulation of tissue inhibitor of metalloproteinases-1 (TIMP-1) by UDCA was studied using zymography and qRT-PCR. A mouse model of acute cholestasis was induced by common BDL technique, during which mice received daily orogastric gavage with either UDCA or vehicle only. Liver injury was quantified using alkaline phosphatase (ALP), relative liver weight, and confirmed by histological analysis. ADAM17 substrates in sera were assessed using a bead multiplex assay.

RESULTS

UDCA decreases amount of shed TNFα, TGFα, and sMet in cell culture media and the phosphorylation of ERK1/2. These effects are mediated by the reduction of ADAM17 activity in PMA stimulated cells although the expression ADAM17 is not affected. UDCA reduced the level of the mature form of ADAM17. Moreover, UDCA regulates the expression of TIMP-1 and gelatinases activity in PMA stimulated cells. A BDL-induced acute cholangitis model was characterized by increased relative liver weight, serum levels of ALP, sMet, and loss of intracellular glycogen. UDCA administration significantly decreased ALP and sMet levels, and reduced relative liver weight. Furthermore, hepatocytes of UDCA-treated animals retained their metabolic activity as evidenced by the amount of glycogen storage.

CONCLUSIONS

The beneficial effect of UDCA appears to be mediated in part by the inhibition of ADAM17 activation and, thus, the release of TNFα, a strong pro-inflammatory factor. The release of other ADAM17 substrates, TGFα and sMet, are also regulated this way, pointing to a general impact on the release of ADAM17 substrates, which are pivotal for liver regeneration and function. In parallel, UDCA upregulates TIMP-1 that in turn inhibits matrix metalloproteinases, which destroy the hepatic ECM in diseased liver. This control of extracellular matrix turnover represents an additional beneficial path of UDCA treatment.

Epigenetic upregulation of HGF and c-Met drives metastasis in hepatocellular carcinoma

Hepatocyte growth factor (HGF) and its receptor, c-Met, are important regulators of growth and differentiation of healthy hepatocytes. However, upregulation of HGF and c-Met have been associated with tumor progression and metastasis in hepatocellular carcinoma (HCC). Hematogenous dissemination is the most common route for cancer metastasis, but the role of HGF and c-Met in circulating tumor cells (CTCs) is unknown. We have isolated and established a circulating tumor cell line from the peripheral blood of a mouse HCC model. Our studies show that these CTCs have increased expression of HGF and c-Met in comparison to the primary tumor cells. The CTCs display phenotypic evidence of epithelial-mesenchymal transition (EMT) and the EMT appears to be inducible by HGF. Epigenetic analysis of the c-Met promoter identified significant loss of DNA methylation in CTCs which correlated with overexpression of c-Met and increased expression of HGF. Six specific CpG sites of c-Met promoter demethylation were identified. CTCs show significantly increased tumorigenicity and metastatic potential in a novel orthotopic syngeneic model of metastatic HCC. We conclude that during hematogenous dissemination in HCC, CTCs undergo EMT under the influence of increased HGF. This process also involves up regulation of c-Met via promoter demethylation at 6 CpG sites. Consequently, targeting HGF and c-Met expression by CTCs may be a novel non-invasive approach with potential clinical applications in HCC management.

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.

Angiogenesis is crucial for liver regeneration after partial hepatectomy

BACKGROUND

Recent studies of hepatic regeneration have mainly focused on the growth of parenchymal cells. However, remodeling of liver vessels seems to be crucial during hepatic regeneration. In this study, we investigated the influence of antiangiogenesis on hepatic regeneration using sFlt-1, a soluble receptor for vascular endothelial growth factor that acts as a dominant negative receptor, and the hepatocyte growth factor antagonist NK4.

METHODS

A sFlt-1-expressing adenoviral vector, an NK4-expressing adenoviral vector, or both combined were infected into C57BL6 mice via the tail vein. A 70% partial hepatectomy was performed on all of the mice 48 hours after infection. The remnants of the liver were removed after the partial hepatectomy, and hepatic regeneration was assessed by measuring the remnant liver weight and hepatocyte mitosis, bromodeoxyuridine staining, immunohistochemical staining with anti-platelet endothelial cell adhesion molecule-1 antibodies, and real-time polymerase chain reaction studies for angiogenic factors.

RESULTS

The immunohistochemical staining for CD31 showed suppression of sinusoidal endothelial cells growth in sFlt-1-expressing adenoviral vector-and NK4-expressing adenoviral vector-infected mice. Increases in the remnant hepatic weight were significantly lower in the sFlt-1-expressing adenoviral vector-infected mice. The bromodeoxyuridine index and mitotic cell results revealed a significant decrease in hepatic regeneration in the sFlt-1-expressing adenoviral vector-and NK4-expressing adenoviral vector-infected mice. The suppressive effects on hepatic regeneration were significantly enhanced by combined sFlt-1-expressing adenoviral vector and NK4-expressing adenoviral vector infection. Real-time polymerase chain reaction results revealed the significant suppression of angiogenic growth factor receptors Tie-1 and Tie-2.

CONCLUSION

The angiogenesis inhibitor significantly suppressed hepatic regeneration. These results suggest that hepatic regeneration after hepatectomy closely correlates with angiogenesis.

Hepatocyte growth factor upregulation promotes carcinogenesis and epithelial-mesenchymal transition in hepatocellular carcinoma via Akt and COX-2 pathways

Advanced hepatocellular carcinoma (HCC) is an important cause of cancer mortality. Epithelial-mesenchymal transition (EMT) has been shown to be an important biological process in cancer progression and metastasis. We have focused on elucidating factors that induce EMT to promote carcinogenesis and subsequent metastasis in HCC using the BNL CL.2 (BNL) and BNL 1ME A. 7R.1 (1MEA) cell lines. BNL cells are normal hepatocytes whereas the 1MEA cells are HCC cells derived from chemical transformation of the BNL cells. Their morphological characteristics were examined. Expression levels of hepatocyte growth factor (HGF), markers of EMT and mediators of HGF signaling were determined and functional characteristics were compared. BNL cells were treated with HGF and effects on EMT-marker and mediators of HGF signaling were analyzed. BNL cells display characteristic epithelial morphology whereas 1MEA cells display mesenchymal characteristics. 1MEA cells express and secrete more HGF than BNL cells. There was significantly decreased expression of E-cadherin, albumin, AAT and increased expression of fibronectin, collagen-1, vimentin, snail and slug in 1MEA cells. There was also increased expression of cyclooxygenase-2 (COX-2), Akt and phosphorylated Akt (pAkt) in 1MEA cells. Moreover, 1MEA cells had increased migratory capacity inhibited by inhibition of COX-2 and Akt but not extracellular signal regulated kinase (ERK). Molecular mesenchymal characteristics of 1MEA cells were reversed by inhibition of COX-2, Akt and ERK. Treatment of BNL cells with HGF led to decreased expression of E-cadherin and increased expression of fibronectin, vimentin, snail, slug, COX-2, Akt, pAkt and increased migration, invasiveness and clonogenicity. We conclude that development of HCC is associated with upregulation of HGF which promotes EMT and carcinogenesis via upregulation of COX-2 and Akt. Consequently, HGF signaling may be targeted for therapy in advanced and metastatic HCC.

Carbon monoxide enhances early liver regeneration in mice after hepatectomy

Hepatocyte proliferation early after liver resection is critical in restoring liver mass and preserving function as the liver regenerates. Carbon monoxide (CO) generated by heme oxygenase-1 (HO-1) strongly influences cellular proliferation and both HO-1 and CO are accepted hepatoprotective molecules. Mice lacking functional HO-1 were unable to mount an appropriate regenerative response following partial hepatectomy (PHTx) compared to wildtype controls. We therefore hypothesized that exogenous administration of CO at low, nontoxic concentrations would modulate hepatocyte (HC) proliferation and liver regeneration. Animals treated with a low concentration of CO 1 hour prior to 70% hepatectomy demonstrated enhanced expression of hepatocyte growth factor (HGF) in the liver compared to controls that correlated with a more rapid onset of HC proliferation as measured by phospho-histone3 staining, increased expression of cyclins D1 and E, phosphorylated retinoblastoma, and decreased expression of the mitotic inhibitor p21. PHTx also increased activation of the HGF receptor c-Met, which was detected more then 9 hours earlier in the livers of CO-treated mice. Blockade of c-Met resulted in abrogation of the CO effects on HC proliferation. Corresponding with increased HC proliferation, treatment with CO maintained liver function with normal prothrombin times versus a 2-fold prolongation in controls. In a lethal 85% PHTx, CO-treated mice showed a greater survival rate compared to controls. In vitro, CO increased HGF expression in hepatic stellate cells, but not HC, and when cocultured together led to increased HC proliferation. In summary, we demonstrate that administration of exogenous CO enhances rapid and early HC proliferation and, importantly, preserves function following PHTx. Taken together, CO may offer a viable therapeutic option to facilitate rapid recovery following PHTx.

Novel molecular therapies in hepatocellular carcinoma

The approval of sorafenib as the standard of care (SOC) for advanced hepatocellular carcinoma (HCC) fostered interest to further evaluate several other targeted therapies and extend the positioning of sorafenib alone and in combination with other drugs and local therapies at earlier stages and in an adjuvant setting. This review highlights current research using targeted therapies in HCC. Information for this review was compiled by searching PubMed and MEDLINE databases for articles published until September 2010. Several small molecules and humanized antibodies with anti-angiogenic and antiproliferative properties are currently being investigated in preclinical and/or clinical trials. Results are awaited from these clinical trials and offer promise for extending the current treatment options in HCC. Currently published data suggest that substantial progress may be achieved in the treatment of patients with HCC in the next 10 years.

Epithelial-to-mesenchymal transition of murine liver tumor cells promotes invasion

Epithelial-to-mesenchymal transition (EMT) is predicted to play a critical role in metastatic disease in hepatocellular carcinoma. In this study, we used a novel murine model of EMT to elucidate a mechanism of tumor progression and metastasis. A total of 2 x 10(6) liver cells isolated from Pten(loxp/loxp)/Alb-Cre(+) mice, expanded from a single CD133(+)CD45(-) cell clone, passage 0 (P0), were sequentially transplanted to obtain two passages of tumor cells, P1 and P2. Cells were analyzed for gene expression using microarray and real-time polymerase chain reaction. Functional analysis included cell proliferation, migration, and invasion in vitro and orthotopic tumor metastasis assays in vivo. Although P0, P1, and P2 each formed tumors consistent with mixed liver epithelium, within the P2 cells, two distinct cell types were clearly visible: cells with epithelial morphology similar to P0 cells and cells with fibroblastoid morphology. These P2 mesenchymal cells demonstrated increased locomotion on wound healing; increased cell invasion on Matrigel basement membrane; increased EMT-associated gene expression of Snail1, Zeb1, and Zeb2; and down-regulated E-cadherin. P2 mesenchymal cells demonstrated significantly faster tumor growth in vivo compared with P2 epithelial counterparts, with invasion of intestine, pancreas, spleen, and lymph nodes. Furthermore, P2 mesenchymal cells secreted high levels of hepatocyte growth factor (HGF), which we propose acts in a paracrine fashion to drive epithelial cells to undergo EMT. In addition, a second murine liver cancer stem cell line with methionine adenosyltransferase 1a deficiency acquired EMT after sequential transplantations, indicating that EMT was not restricted to Pten-deleted tumors.

CONCLUSION

EMT is associated with a high rate of liver tumor proliferation, invasion, and metastasis in vivo, which is driven by HGF secreted from mesenchymal tumor cells in a feed-forward mechanism.

Hepatocyte growth factor and Met in tumor biology and therapeutic approach with NK4

Hepatocyte growth factor (HGF) and Met/HGF receptor tyrosine kinase play a role in the progression to invasive and metastatic cancers. A variety of cancer cells secrete molecules that enhance HGF expression in stromal fibroblasts, while fibroblast-derived HGF, in turn, is a potent stimulator of the invasion of cancer cells. In addition to the ligand-dependent activation, Met receptor activation is negatively regulated by cell-cell contact and Ser985 phosphorylation in the juxtamembrane of Met. The loss of intercellular junctions may facilitate an escape from the cell-cell contact-dependent suppression of Met-signaling. Significance of juxtamembrane mutations found in human cancers is assumed to be a loss-of-function in the negative regulation of Met. In attempts to block the malignant behavior of cancers, NK4 was isolated as a competitive antagonist against HGF-Met signaling. Independently on its HGF-antagonist action, NK4 inhibited angiogenesis induced by vascular endothelial cell growth factor and basic fibroblast growth factor, as well as HGF. In experimental models of distinct types of cancers, NK4 inhibited Met activation and this was associated with inhibition of tumor invasion and metastasis. NK4 inhibited tumor angiogenesis, thereby suppressing angiogenesis-dependent tumor growth. Cancer treatment with NK4 suppresses malignant tumors to be "static" in both tumor growth and spreading.

Targeting vessels to treat hepatocellular carcinoma

The process of blood vessel proliferation, known as angiogenesis, is essential during embryonic development and organogenesis. In adult life, it participates in normal tissue repair, wound healing, and cyclical growth of the corpus luteum and the endometrium. Crucial as it is, angiogenesis can become pathological, and abnormal angiogenesis contributes to the pathogenesis of inflammatory and neoplasic diseases. The present review highlights the evidence for the role of angiogenesis in HCC (hepatocellular carcinoma) and discusses the increasing importance of inhibitors of angiogenesis in HCC therapy.

Accelerated orthotopic hepatocellular carcinomas growth is linked to increased expression of pro-angiogenic and prometastatic factors in murine liver fibrosis

BACKGROUND

Most experimental therapy studies are performed in mice that bear subcutaneous or orthotopic hepatoma but are otherwise healthy. We questioned whether a pre-existing fibrosis affects tumour development of implanted syngenic hepatoma cells. To further investigate a selected panel of factors involved in tumour growth, tumour organ samples were characterized for gene expression of vascular endothelial growth factor (VEGF)-A/-C, VEGF receptors Flt1, Flk-1, Flt-4 and for VEGF-A protein levels.

RESULTS

The presented data show that tumour sizes were 3.7-fold increased and fibrotic livers had numerous satellites. Increased tumour sizes were associated with elevated intratumoral VEGF-A protein amounts and intratumoral increased VEGF receptor gene expression levels in tumour tissue from fibrotic livers as compared with non-fibrotic livers. Additionally, intratumoral gene expression levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 were elevated in fibrotic mice.

CONCLUSION

Our results indicate that liver fibrosis stimulates tumour development of implanted syngenic hepatoma cells. Accelerated tumour growth was going along with elevated intratumoral VEGF-A and VEGF-A receptor status, which most probably mediated pro-angiogenic and prometastatic effects in this model. Furthermore, advanced tumour spread was associated with increased MMP-2/-9 expression. These data suggest that the intratumoral VEGF-A proteins levels and VEGF receptor status contribute to accelerated hepatocellular carcinoma development in fibrotic mice and that elevated MMP-2, MMP-9 and VEGF-C levels could promote tumour metastasis in this model.

Translational control plays a prominent role in the hepatocytic differentiation of HepaRG liver progenitor cells

BACKGROUND

We investigated the molecular events associated with the differentiation of liver progenitor cells into functional and polarized hepatocytes, using human HepaRG cells that display potent hepatocytic differentiation-inducible properties and share some features with liver progenitor cells.

RESULTS

Profiling of total and of polysome-bound transcripts isolated from HepaRG cells undergoing hepatocytic differentiation was performed. A group of 3,071 probe sets was reproducibly regulated by at least 2-fold in total or in polysome-bound RNA populations, upon differentiation. The fold changes in the total and the polysome-bound RNA populations for these 3,071 probe sets were poorly correlated (R = 0.38). Moreover, while the majority of the regulated polysome-bound RNA probe sets were up-regulated upon differentiation, the majority of the regulated probe sets selected from the total RNA population was down-regulated. Genes translationally up-regulated were associated with cell cycle inhibition, increased susceptibility to apoptosis and innate immunity. In contrast, genes transcriptionally up-regulated during differentiation corresponded in the majority to liver-enriched transcripts involved in lipid homeostasis and drug metabolism. Finally, several epithelial and hepato-specific transcripts were strongly induced in the total RNA population but were translationally repressed.

CONCLUSION

Translational regulation is the main genomic event associated with hepatocytic differentiation of liver progenitor cells in vitro and targets genes critical for moderating hepatocellular growth, cell death and susceptibility to pathogens. Transcriptional regulation targets specifically liver-enriched transcripts vital for establishing normal hepatic energy homeostasis, cell morphology and polarization. The hepatocytic differentiation is also accompanied by a reduction of the transcript content complexity.

Mammalian target of rapamycin activation impairs hepatocytic differentiation and targets genes moderating lipid homeostasis and hepatocellular growth

The mammalian target of rapamycin (mTOR) pathway, a major regulator of translation, is frequently activated in hepatocellular carcinomas. We investigated the effects of mTOR activation in the human HepaRG cells, which possess potent hepatocytic differentiation capability. Differentiation of HepaRG cells into functional and polarized hepatocyte-like cells correlated with a decrease in mTOR and Akt activities. Stable cell lines expressing an activated mutant of mTOR were generated. Sustained activation of mTOR impaired the hepatocytic differentiation capability of these cells as shown by impaired formation of bile canaliculi, absence of polarity, and reduced secretion of alpha1-antitrypsin. An inhibitor of mTOR, rapamycin, was able to revert this phenotype. Furthermore, increased mTOR activity in HepaRG cells resulted in their resistance to the antiproliferative effects of transforming growth factor-beta1. Profiling of polysome-bound transcripts indicated that activated mTOR specifically targeted genes posttranscriptionally regulated on hepatocytic differentiation. Three major biological networks targeted by activated mTOR were identified: (a) cell death associated with tumor necrosis factor superfamily members, IFNs and caspases; (b) lipid homeostasis associated with the transcription factors PPARalpha, PPARdelta, and retinoid X receptor beta; and (c) liver development associated with CCAAT/enhancer binding protein alpha and hepatic mitogens. In conclusion, increased mTOR activity conferred a preneoplastic phenotype to the HepaRG cells by altering the translation of genes vital for establishing normal hepatic energy homeostasis and moderating hepatocellular growth.

Suppression of human colon tumor growth by adenoviral vector-mediated NK4 expression in an athymic mouse model

AIM: To investigate the suppressive effects of adenoviral vector-mediated expression of NK4, an antagonist of hepatocyte growth factor (HGF), on human colon cancer in an athymic mouse model to explore the possibility of applying NK4 to cancer gene therapy.

METHODS: A human colon tumor model was developed by subcutaneous implantation of tumor tissue formed by LS174T cells grown in athymic mice. Fifteen tumor-bearing mice were randomized into three groups (n = 5 in each group) at d 3 after tumor implantation and mice were injected intratumorally with phosphate-buffered saline (PBS) or with recombinant adenovirus expressing β-galactosidase (Ad-LacZ) or NK4 (rvAdCMV/NK4) at a 6-d interval for total 5 injections in each mouse. Tumor sizes were measured during treatment to draw a tumor growth curve. At d 26 after the first treatment, all animals were sacrificed and the tumors were removed to immunohistochemically examine proliferating cell nuclear antigen (PCNA), microvessel density (represented by CD31), and apoptotic cells. In a separate experiment, 15 additional athymic mice were employed to develop a tumor metastasis model by intraperitoneal injection (ip) of LS174T cells. These mice were randomized into 3 groups (n = 5 in each group) at d 1 after injection and were treated by ip injection of PBS, or Ad-LacZ, or rvAdCMV/NK4 at a 6-d interval for total two injections in each mouse. All animals were sacrificed at d 14 and the numbers and weights of disseminated tumors within the abdominal cavity were measured.

RESULTS: Growth of human colon tumors were significantly suppressed in the athymic mice treated with rvAdCMV/NK4 (2537.4 ± 892.3 mm³) compared to those treated by either PBS (5175.2 ± 1228.6 mm³) or Ad-LacZ (5578.8 ± 1955.7 mm³) (P < 0.05). The tumor growth inhibition rate was as high as 51%. Immunohistochemical staining revealed a similar PCNA labeling index (75.1% ± 11.2% in PBS group vs 72.8% ± 7.6% in Ad-LacZ group vs 69.3% ± 9.4% in rvAdCMV/NK4 group) in all groups, but significantly lower microvessel density (10.7 ± 2.4 in rvAdCMV/NK4 group vs 25.6 ± 3.8 in PBS group or 21.3 ± 3.5 in Ad-LacZ group, P < 0.05), and a markedly higher apoptotic index (7.3% ± 2.4% in rvAdCMV/NK4 group vs 2.6 ± 1.1% in PBS group or 2.1% ± 1.5% in Ad-LacZ group, P < 0.05) in the rvAdCMV/NK4 group compared to the two control groups. In the tumor metastasis model, the number and weight of disseminated tumors of mice treated with rvAdCMV/NK4 were much lower than those of the control groups (tumor number: 6.2 ± 3.3 in rvAdCMV/NK4 group vs 22.9 ± 7.6 in PBS group or 19.8 ± 8.5 in Ad-LacZ group, P < 0.05; tumor weight: 324 ± 176 mg in rvAdCMV/NK4 group vs 962 ± 382 mg in PBS group or 1116 ± 484 mg in Ad-LacZ group, P < 0.05).

CONCLUSION: The recombinant adenovirus, rvAdCMV/NK4, can attenuate the growth of colon cancer in vivo, probably by suppressing angiogenesis and inducing tumor cell apoptosis, but not by direct suppression of tumor cell proliferation. Moreover, rvAdCMV/NK4 may inhibit peritoneal dissemination of colon cancer cells in a murine tumor metastasis model. These findings indicate that NK4 gene transfer may be an effective tool for the treatment of colon cancer.