Heparanase and hepatocellular carcinoma:Promoter or inhibitor?

Heparan sulphate proteoglycans (HSPGs) consist of a core protein and several heparan sulphate (HS) side chains covalently linked. HS also binds a great deal of growth factors, chemokines, cytokines and enzymes to the extracellular matrix and cell surface. Heparanase can specially cleave HS side chains from HSPGs. There are a lot of conflicting reports about the role of heparanase in hepatocellular carcinoma (HCC). Heparanase is involved in hepatitis B virus infection and hepatitis C virus infection, the activation of signal pathways, metastasis and apoptosis of HCC. Heparanase is synthesized as an inactive precursor within late endosomes and lysosomes. Then heparanase undergoes proteolytic cleavage to form an active enzyme in lysosomes. Active heparanase translocates to the nucleus, cell surface or extracellular matrix. Different locations of heparanase may exert different activities on tumor progression. Furthermore, enzymatic activities and non-enzymatic activities of heparanase may play different roles during HCC development. The expression level of heparanase may also contribute to the discrepant effects of heparanase. Growth promoting as well as growth inhibiting sequences are contained within the tumor cell surface heparan sulfate. Degrading different HSPGs by heparanase may play different roles in HCC. Systemic studies examining the processing, expression, localization and function of heparanase should shed a light on the role of heparanase in HCC.

Increased expression of chondroitin sulphate proteoglycans in rat hepatocellular carcinoma tissues

AIM:To investigate the expression of chondroitin sulphate proteoglycans(CSPGs)in rat liver tissues of hepatocellular carcinoma(HCC).METHODS:Thirty male Sprague Dawley rats were randomly divided into two groups:control group(n=10) and HCC model group(n=20).Rats in the HCC model groups were intragastrically administrated with 0.2%(w/v)N-diethylnitrosamine(DEN)every 5 d for 16 wk,whereas 0.9%(w/v)normal saline was administered to rats in the control group.After 16 wk from the initiation of experiment,all rats were killed and livers were collected and fixed in 4%(w/v)paraformaldehyde.All tissues were embedded in paraffin and sectioned.Histological staining(hematoxylin and eosin and Toluidine blue)was performed to demonstrate the onset of HCC and the content of sulphated glycosaminoglycan(sGAG).Immunohistochemical staining was performed to investigate the expression of chondroitin sulphate(CS)/dermatan sulphate(DS)-GAG,heparan sulphate(HS)-GAG,keratan sulphate(KS)-GAG in liver tissues.Furthermore,expression and distribution of CSPG family members,including aggrecan,versican,biglycan and decorin in liver tissues,were also immunohistochemically determined.RESULTS:After 16 wk administration of DEN,malignant nodules were observed on the surface of livers from the HCC model group,and their hepatic lobule structures appeared largely disrupted under microscope.Toluidine blue staining demonstrated that there was an significant increase in sGAG content in HCC tissues when compared with that in the normal liver tissues from the control group[0.37±0.05 integrated optical density per stained area(IOD/area)and 0.21± 0.01 IOD/area,P<0.05].Immunohistochemical studies demonstrated that this increased sGAG in HCC tissues was induced by an elevated expression of CS/DS(0.28±0.02 IOD/area and 0.18±0.02 IOD/area,P< 0.05)and HS(0.30±0.03 IOD/area and 0.17±0.02 IOD/area,P<0.01)but not KS GAGs in HCC tissues.Further studies thereby were performed to investigate the expression and distribution of several CSPG components in HCC tissues,including aggrecan,versican,biglycan and decorin.Interestingly,there was a distinct distribution pattern for these CSPG components between HCC tissues and the normal tissues.Positive staining of aggrecan,biglycan and decorin was localized in hepatic membrane and/or pericellular matrix in normal liver tissues;however,their expression was mainly observed in the cytoplasm,cell membranes in hepatoma cells and/or pericellular matrix within HCC tissues.Semi-quantitative analysis indicated that there was a higher level of expression of aggrecan(0.43± 0.01 and 0.35±0.03,P<0.05),biglycan(0.32±0.01 and 0.25±0.01,P<0.001)and decorin(0.29±0.01 and 0.26±0.01,P<0.05)in HCC tissues compared with that in the normal liver tissues.Very weak versican positive staining was observed in hepatocytes near central vein in normal liver tissues;however there was an intensive versican distribution in fibrosis septa between the hepatoma nodules.Semi-quantitative analysis indicated that the positive rate of versican in hepatoma tissues from the HCC model group was much higher than that in the control group(33.61%and 21.28%,P <0.05).There was no positive staining in lumican and keratocan,two major KSPGs,in either normal or HCC liver tissues.CONCLUSION:CSPGs play important roles in the onset and progression of HCC,and may provide potential therapeutic targets and clinical biomarkers for this prevalent tumor in humans.

Expression of human hepatic lipase negatively impacts apolipoprotein A-Ⅰ production in primary hepatocytes from Lipc-null mice

This study aimed to examine whether expression of human hepatic lipase（hHL） exerted an intracellular effect on hepatic production of apolipoprotein（apo） A-I.The levels of secreted and cell-associated apoA-I were contrasted between primary hepatocytes isolated from Lipc-nuW and C57BL/6 mice,and between Lipc-nuW hepatocytes transfected with either hHL-encoding or control adenovirus.An HSPG-binding deficient hHL protein（hHLmt） was used to determine the impact of cell surface binding on HL action.Accumulation of apoA-I in conditioned media of primary hepatocytes isolated from Lipc-nuW mice was increased as compared to that from C57BL/6 mice.Metabolic labeling experiments showed that secretion of ＇＇S-apoA-I from Lipc-nuW cells was significantly higher than that from C57BL/6 cells.Expression of hHL in Lipc-nuW hepatocytes,through adenovirus-mediated gene transfer,resulted in decreased synthesis and secretion of ＇S-apoA-I,but not S-apoE,as compared with cells transfected with control adenovirus.Expression of HSPG-binding deficient hHLmt in Lipc-nuW cells also exerted an inhibitory effect on apoA-I production,even though hHLmt displayed impaired exit from the endoplasmic reticulum as compared with hHL.Subcellular fractionation revealed that expression of hHL or hHLmt led to increased microsome-association of apoA-I relative to non-transfected control.Expression of hHL negatively impacts hepatic production of apoA-I.