Kevin Tak-Pan Ng

Suppression of Liver Tumor Growth and Metastasis by Adiponectin in Nude Mice through Inhibition of Tumor Angiogenesis and Downregulation of Rho Kinase/IFN-Inducible Protein 10/Matrix Metalloproteinase 9 Signaling

Purpose: We aimed to investigate the effects of adiponectin on liver cancer growth and metastasis and explore the underlying mechanisms. Experimental Design: An orthotopic liver tumor nude mice model with distant metastatic potential was applied. Either Ad-adiponectin (1 × 108; treatment group) or Ad-luciferase (control group) was injected via portal vein after tumor implantation. Tumor growth and metastasis were monitored by Xenogen In vivo Imaging System. Hepatic stellate cell activation by α-smooth muscle actin staining, microvessel density by CD34 staining, macrophage infiltration in tumor tissue, and cell signaling leading to invasion, migration [Rho kinase (ROCK), IFN-inducible protein 10 (IP10), and matrix metalloproteinase 9], and angiogenesis [vascular endothelial growth factor (VEGF) and angiopoietin 1] were also compared. Tumor-nontumor margin was examined under electron microscopy. Direct effects of adiponectin on liver cancer cells and endothelial cells were further investigated by a series of functional studies. Results: Tumor growth was significantly inhibited by adiponectin treatment, accompanied by a lower incidence of lung metastasis. Hepatic stellate cell activation and macrophage infiltration in the liver tumors were suppressed by adiponectin treatment, along with decreased microvessel density. The treatment group had less Ki-67–positive tumor cells and downregulated protein expression of ROCK1, proline-rich tyrosine kinase 2, and VEGF. Tumor vascular endothelial cell damage was found in the treatment group under electron microscopy. In vitro functional study showed that adiponectin not only downregulated the ROCK/IP10/VEGF signaling pathway but also inhibited the formation of lamellipodia, which contribute to cell migration. Conclusion: Adiponectin treatment significantly inhibited liver tumor growth and metastasis by suppression of tumor angiogenesis and downregulation of the ROCK/IP10/matrix metalloproteinase 9 pathway. Clin Cancer Res; 16(3); 967–77

Signal Transducers and Activators of Transcription 5b Activation Enhances Hepatocellular Carcinoma Aggressiveness through Induction of Epithelial-Mesenchymal Transition

Poor prognosis of hepatocellular carcinoma (HCC) is associated with a high potential of vascular invasion and metastasis. Epithelial-mesenchymal transition (EMT) is a key event in the tumor invasion process. Recently, signal transducers and activators of transcription 5 (STAT5) has been linked to tumor progression by EMT induction. However, the precise roles of STAT5 genes (STAT5a and STAT5b) in human epithelial cancers have not been elucidated clearly. The aim of this study is to analyze the roles of STAT5 isoforms in HCC progression using HCC clinical samples. We showed that activation of STAT5b, but not STAT5a, was found in HCC clinical samples and its expression was significantly associated with younger age (P = 0.037), advanced tumor stages (P = 0.003), venous infiltration (P = 0.016), microsatellite formation (P = 0.024), multiple tumor nodules (P = 0.02), and poor patient survival. To specifically investigate the mechanism underlying constitutive activation of STAT5b in HCC, EGFP-HBX was introduced into Huh-7 cells. STAT5b activation in HCC is at least partially mediated by HBX activation. Ectopic STAT5b transfection conferred increased HCC cell motility and invasiveness by induction of EMT changes. In conclusion, STAT5b activation enhanced HCC aggressiveness by induction of EMT, which was possibly mediated by HBX activation. STAT5b could serve as a novel molecular target for HCC treatment.

Proline-rich tyrosine kinase 2 (Pyk2) promotes proliferation and invasiveness of hepatocellular carcinoma cells through c-Src/ERK activation

The aim of the current study is to elucidate the mechanism of proline-rich tyrosine kinase 2 (Pyk2)-mediated cell proliferation and invasiveness in hepatocellular carcinoma (HCC) cells. Human HCC cell lines PLC and MHCC97L were stably transfected with either full-length Pyk2 or C-terminal non-kinase region of Pyk2 (PRNK). Functional studies on cell proliferation and invasion were conducted in vitro by colony formation assay, adhesion assay, migration assay and wound-healing assay. For the in vivo study, an orthotopic nude mice liver tumor model was applied to investigate the effects of Pyk2 overexpression on tumor growth and metastasis. Overexpression of Pyk2 in PLC cells resulted in an upregulation of colony formation (P = 0.021) and adhesion toward laminin (P = 0.018). Pyk2 promoted wound recovery by stimulation of actin stress fiber polymerization. In the in vivo study, transfection of PRNK in MHCC97L cells significantly decreased tumor volume (P = 0.001) and the incidence of lung metastasis (P = 0.014). Overexpression of Pyk2 promoted the activation of c-Src, formation of Pyk2/c-Src complex and activated the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK)-signaling pathway. Pyk2 upregulated the activation of ERK1/2 that is insensitive to MAPK/ERK kinase (MEK)1/2 inhibition. On the contrary, PRNK overexpression downregulated the activation of c-Src and ERK/MAPK-signaling pathways. Immunofluorescence staining showed that the focal adhesion localization of Pyk2 is a major determinant for c-Src and ERK/MAPK activation. In conclusion, our results showed that Pyk2 promoted cell proliferation and invasiveness by upregulation of the c-Src and ERK/MAPK-signaling pathways.

Ischemia-reperfusion of small liver remnant promotes liver tumor growth and metastases--activation of cell invasion and migration pathways.

Elucidating the mechanism of liver tumor growth and metastasis after hepatic ischemia‐reperfusion (I/R) injury of a small liver remnant will lay the foundation for the development of therapeutic strategies to target small liver remnant injury, and will reduce the likelihood of tumor recurrence after major hepatectomy or liver transplantation for liver cancer patients. In the current study, we aimed to investigate the effect of hepatic I/R injury of a small liver remnant on liver tumor development and metastases, and to explore the precise molecular mechanisms. A rat liver tumor model that underwent partial hepatic I/R injury with or without major hepatectomy was investigated. Liver tumor growth and metastases were compared among the groups with different surgical stress. An orthotopic liver tumor nude mice model was used to further confirm the invasiveness of the tumor cells from the above rat liver tumor model. Significant tumor growth and intrahepatic metastasis (5 of 6 vs. 0 of 6, P = 0.015), and lung metastasis (5 of 6 vs. 0 of 6, P = 0.015) were found in rats undergoing I/R and major hepatectomy compared with the control group, and was accompanied by upregulation of mRNA levels for Cdc42, ROCK (Rho kinase), and vascular endothelial growth factor, as well as activation of hepatic stellate cells. Most of the nude mice implanted with liver tumor from rats under I/R injury and major hepatectomy developed intrahepatic and lung metastases. In conclusion, hepatic I/R injury of a small liver remnant exacerbated liver tumor growth and metastasis by marked activation of cell adhesion, invasion, and angiogenesis pathways. Liver Transpl 13:1669–1677, 2007.

Attenuation of acute phase shear stress by somatostatin improves small-for-size liver graft survival.

The major concern of living donor liver transplantation is small‐for‐size graft injury at the early phase after transplantation. Novel therapeutic strategies should be developed. To investigate the protective effect of somatostatin related to hemodynamic stress on small‐for‐size liver graft injury, we applied a treatment regimen of low‐dose somatostatin in a rat orthotopic liver transplantation model using small‐for‐size grafts (median, 38.7%; range, 35–42%). Somatostatin was given at 5 minutes before total hepatectomy and immediately after reperfusion in the recipient (20 μg/kg). Graft survival, portal hemodynamics, intragraft gene expression and hepatic ultrastructural changes were compared between the rats with or without somatostatin treatment. Seven‐day graft survival rates in the somatostatin treatment group were significantly improved compared to the control group (66.7% vs. 16.7%, P = 0.036). In the treatment group, portal pressure and hepatic surface blood flow were significantly decreased within the first 30 minutes after reperfusion, whereas in the control group, transient portal hypertension and excessive hepatic blood flow were observed. Intragraft expression (both messenger RNA and protein) of endothelin‐1 was significantly downregulated accompanied with upregulation of heme oxygenase‐1 and A20. Better preservation of liver function was found in the treatment group. Hepatic ultrastructure, especially the integrity of sinusoids, was well protected in the treatment group. In conclusion, low‐dose somatostatin rescues small‐for‐size grafts from acute phase injury in liver transplantation by attenuation of acute‐phase shear stress that resulted from transient portal hypertension. Liver Transpl 12:621–627, 2006.

FK 409 Ameliorates Small-for-Size Liver Graft Injury by Attenuation of Portal Hypertension and Down-Regulation of Egr-1 Pathway

Objective:To investigate whether low-dose nitric oxide donor FK 409 could attenuate small-for-size graft injury in liver transplantation using small-for-size grafts. Summary Background Data:The major concern of live donor liver transplantation is small-for-size graft injury at the early phase after transplantation. Novel therapeutic strategies should be investigated. Methods:We employed a rat orthotopic liver transplantation model using small-for-size (40%) graft. FK 409 was given at 30 minutes before graft harvesting (2 mg/kg) to the donor and immediately after reperfusion (1 mg/kg) to the recipient (FK group). Graft survival, intragraft genes expression, portal hemodynamics, and hepatic ultrastructural changes were compared between the 2 groups. Results:Seven-day graft survival rates in the FK group were significantly improved compared with those of rats not receiving FK 409 (control group; 80% versus 28.6%, P = 0.018). In the FK group, portal pressure was significantly decreased within the first 60 minutes after reperfusion whereas in the control group, transient portal hypertension was observed. Intragraft expression (both mRNA and protein) of early growth response-1, endothelin-1, endothelin-1 receptor A, tumor necrosis factor-α, macrophage-inflammatory protein-2, and inducible nitric oxide synthase was significantly down-regulated accompanied with up-regulation of heme oxygenase-1, A20, interferon-γ-inducible protein-10, and interleukin-10 during the first 24 hours after reperfusion. Hepatic ultrastructure, especially the integrity of sinusoids was well protected in the FK group. Conclusions:Low-dose FK 409 rescues small-for-size grafts in liver transplantation by attenuation of portal hypertension and amelioration of acute phase inflammatory response by down-regulation of Egr-1, together with prior induction of heat shock proteins.

FTY720 Attenuates Hepatic Ischemia‐Reperfusion Injury in Normal and Cirrhotic Livers

Hepatic ischemia‐reperfusion injury is an inevitable consequence during liver surgery. The outcome is particularly poor in cirrhotic livers, which are more prone to hepatic ischemia‐reperfusion injury. We aim to study whether FTY720 could attenuate hepatic ischemia‐reperfusion injury both in normal and in cirrhotic livers. We applied a 70% liver‐ischemia (60 min) model in rats with normal or cirrhotic livers. FTY720 was given 20 min before ischemia and 10 min before reperfusion (1 mg/kg, i.v.). Liver tissues and blood were sampled at 20 min, 60 min, 90 min, 6 h and 24 h after reperfusion for detection of MAPK‐Egr‐1, Akt pathways and caspase cascade. Hepatic ultrastructure and apoptosis were also compared. FTY720 significantly improved liver function in the rats with normal and cirrhotic livers. Akt pathway was activated at 6 and 24 h after reperfusion. FTY720 significantly down‐regulated Egr‐1, ET‐1, iNOS and MIP‐2 accompanied with up‐regulation of A20, IL‐10, HO‐1 and Hsp70. MAPK (Raf‐MEK‐Erk) pathway was down‐regulated. Hepatic ultrastructure was well maintained and fewer apoptotic liver cells were found in the FTY720 groups. In conclusion, FTY720 attenuates ischemia‐reperfusion injury in both normal and cirrhotic livers by activation of cell survival Akt signaling and down‐regulation of Egr‐1 via Raf‐MEK‐Erk pathway.

Alternatively activated (M2) macrophages promote tumour growth and invasiveness in hepatocellular carcinoma

BACKGROUND & AIMS The roles of alternatively activated (M2) macrophages on pro-tumour phenotypes have been well documented in many cancers except hepatocellular carcinoma (HCC). Considering their close relationship with chronic tissue injuries as well as enhanced tumour invasiveness and growth, we aimed to investigate the direct effects of M2 macrophages on HCC. METHODS M2 macrophages in 95 HCC clinical specimens were quantified using immunohistochemistry and quantitative PCR. The pro-tumour functions and the underlying molecular mechanisms of M2 macrophages in HCC were investigated in vivo and in an in vitro co-culture system. RESULTS In the clinical study, high M2-specific CD163 (hazard ratio=2.693; p=0.043) and scavenger receptor A (hazard ratio=3.563; p=0.044) levels indicated poor prognosis and correlated with increased tumour nodules and venous infiltration in HCC patients. In an orthotopic model, the liver tumour volume was increased 3.26-fold (1.27 cm3±0.36) after M2 macrophage injection compared with the control (0.39 cm3±0.05) (p=0.032). An increased rate of lung metastasis was also found in the treatment group. In vitro, co-cultivation with M2 macrophages elevated the number of HCC cells (MHCC97L) and migration events by 1.3-fold and 3.2-fold, respectively (p<0.05). Strongly induced by MHCC97L, M2 macrophage-derived CCL22 was proven to enhance tumour migration capacities and correlate with venous infiltration in HCC patients. Increased epithelial-mesenchymal transition (EMT) via Snail activation in MHCC97L was found to be promoted by M2 macrophages and CCL22. CONCLUSIONS M2 macrophages contribute to poor prognosis in HCC and promote tumour invasiveness through CCL22-induced EMT.

Clinicopathological significance of homeoprotein Six1 in hepatocellular carcinoma

Tumour recurrence and metastases of hepatocellular carcinoma (HCC) after hepatectomy are the major obstacles of long-term survival. The present study investigated the clinicopathological significance of a possible metastasis regulator Six1 in HCC patients who were undergone hepatectomy. Seventy-two pairs of RNA and 103 pairs of protein from tumour and adjacent nontumour liver tissues of HCC patients were examined. About 85 and 60% of HCC tumour tissues were found to overexpress Six1 mRNA and protein, respectively, compared with nontumour liver tissues. No Six1 protein was detected in HCC nontumour liver tissues and normal liver tissues. Increased Six1 protein expression in HCC patients was significantly correlated with pathologic tumour-node-metastasis (pTNM) stage (P=0.002), venous infiltration (P=0.004) and poor overall survival (P=0.0423). We concluded that Six1 is frequently overexpressed in HCC patients and elevated Six1 protein in HCC patients may be an indication of advanced stage and poor overall survival after hepatectomy.

The significance of proline-rich tyrosine kinase2 (Pyk2) on hepatocellular carcinoma progression and recurrence

Understanding the precise molecular mechanisms that trigger liver cancer cell migration and invasion could develop novel therapeutic strategies targeting cancer cell invasion to increase the sensitivity to current treatment modalities. In the current study, 49 patients with hepatocellular carcinoma (HCC) were included prospectively. Liver tumour and adjacent non-tumour tissues were detected for the expression of Proline-rich tyrosine kinase 2 (Pyk2), focal adhesion kinase (FAK), ezrin and fibronectin at protein and/or gene levels. Correlation between the expressions of Pyk2/FAK with the clinical pathological data was analysed. Protein expression of Pyk2 was also examined in a nude mice orthotopic liver tumour model with higher metastatic potential. There were 59% (29 out of 49) and 57% (28 out of 49) of HCC patients with higher levels of Pyk2 and FAK protein/gene expression, respectively. We observed a positive correlation between the protein and gene expression levels of Pyk2 and FAK (P=0.000, r=0.875). Overexpression of Pyk2 and FAK was significantly correlated with shorter disease-free survival. Patients with higher levels of Pyk2/FAK had larger tumour size and advanced Edmonson grading. In the animal studies, Pyk2 overexpression was found in infiltrative tumour cells and lung metastatic nodules. In conclusion, overexpression of Pyk2 and FAK was found in nearly 60% of HCC patients and was significantly correlated with poor prognosis. The significance of Pyk2 in HCC invasiveness was confirmed by animal studies.