Signal transduction of gap junctional genes,connexin32,connexin43 in human hepatocarcinogenesis

AIM: To investigate gap junctional intercellular communication (GJIC) in hepatocellular carcinoma cell lines, and signal transduction mechanism of gap junction genes connexin32(cx32),connexin43(cx43) in human hepatocarcinogenesis.METHODS: Scarped loading and dye transfer (SLDT) was employed with Lucifer Yellow (LY) to detect GJIC function in hepatocellular carcinoma cell lines HHCC, SMMC-7721and normal control liver cell line QZG. After Fluo-3AM loading, laser scanning confocal microscope (LSCM) was used to measure concentrations of intracellular calcium [Ca2+]i in the cells. The phosphorylation on tyrosine of connexin proteins was examined by immunoblot.RESULTS: SLDT showed that ability of GJIC function was higher in QZG cell than that in HHCC and SMMC-7721 cell lines. By laser scanning confocal microscopy, concentrations of intracellular free calcium [Ca2+]i was much higher in QZG cell line (108.37 nmol/L) than those in HHCC (35.13nmol/L) and SMMC-7721 (47.08 nmol/L) cells. Western blot suggested that only QZG cells had unphosphorylated tyrosine in Cx32 protein of 32 ku and Cx43 protein of 43ku; SMMC-7721 cells showed phosphorylated tyrosine Cx43 protein.CONCLUSION: The results indicated that carcinogenesis and development of human hepatocellular carcinoma related with the abnormal expression of cx genes and disorder of its signal transduction pathway, such as decrease of [Ca2+]i,post-translation phosphorylation on tyrosine of Cx proteins which led to a dramatic disruption of GJIC.

Laminin induces the expression of cytokeratin 19 in hepatocellular carcinoma cells growing in culture

AIM: To study the abnormal cytokeratin (CK) expression,emergence of CK19 with or without CK7, in liver parenchymal cells and the role of laminin (LN), a basement membrane protein, in this process.METHODS: Six hepatocellular carcinoma (HCC) cell lines were examined for different CKs, LN and its receptor by immunocytochemistry and Western blotting. Double immunofluorescent reaction, laser-scanning confocal microscopy and an in vitro induction procedure were used to demonstrate the role of LN in regulating CK19 expression in these cells.RESULTS: Immunoreactivities for CK8, CK18, CK7 and the receptor for LN were observed in all the six HCC cell lines examined. However, CK19 was merely found in four of the six cell lines, and was in any case associated with LN expression. Laser-scanning confocal microscopydemonstrated the concomitant presence of these two molecules in most of the positive cells. In the two HCC cell lines, originally negative for CK19, addition of LN to the culture medium resulted in an induction of CK19 in a dosedependent manner. Both the artificially induced and the intrinsic production of CK19 were completely blocked by an antibody to LN.CONCLUSION: LN can induce expression of CK19 in HCC cells in vitro, providing direct evidence for our hypothesis that the abnormal hepatocytic CK19 expression in situ is due to pathologic LN deposition.

Effect of hepatoma H22 on lymphatic endothelium in vitro

AIM: To determine the effect of metastatic hepatoma cells on lymphangioma-derived endothelium, and to establish in vitro model systems for assessing metastasis-related response of lymphatic endothelium.METHODS: Benign lymphangioma, induced by intraperitoneal injection of the incomplete Freund's adjuvant in BALB/c mice, was embedded in fibrin gel or digested and then cultured in the conditioned medium derived from hepatoma H22. Ught and electron microscopy, and the b-answell migration assay were used to determine the effect of H22 on tissue or cell culture. Expressions of Fit-4, c-Fos, proliferating cell nuclear antigen (PCNA), and inducible nitric oxide synthase (iNOS) in cultured cells, and content of nitric oxide in culture medium were also examined.RESULTS: The embedded lymphangioma pieces gave rise to array of capillaries, while separated cells from lymphangioma grew to a cobblestone-like monolayer. H22 activated growth and migration of the capillaries and cells, induced expressions of Flt-4, c-Fos, PCNA and iNOS in cultured cells, and significantly increased the content of NO in the culture medium.CONCLUSION: Lymphangioma-derived cells keep the differentiated phenotypes of lymphatic endothelium, and the models established in this study are feasible for in vitro study of metastasis-related response of lymphatic endothelium.

Effects of cholesterol on the phenotype of rabbit bile duct fibroblasts

AIM: To investigate how cholesterol (Ch) can affect thephenotype of bile duct fibroblasts of New Zealand rabbits.METHODS: 16 rabbits were divided randomly into twogroups: the control group and the experiment group. Therabbits in experiment group were fed with hypercholesteroldiet for 8 weeks. Bile duct was dissociated from rabbits andprepared for transmission electron microscopy. The purifiedbile duct fibroblasts were cultured and divided randomlyinto there groups: control group, Ch smiddle concentrationgroup (0.6 g/L), Ch high concentration group (1.2 g/L). Afterincubated for 72 h, the fibroblasts were made into specimensfor transmission electron microscopy. The expression of α-actin in bile duct fibroblasts was measured by means oflaser scanning confocal microscopy.RESULTS: With the transmission electron microscopy, thenormal bile duct fibroblasts were shuttle-shaped, and therewere abundant rough endoplasmic reticulums (RER), butfew mitochondria or microfilaments in cytoplasm. This isthe typical phenotype of fibroblasts. Bile duct fibroblasts ofhypercholesterolemic rabbits were observed, by thetransmission electron microscopy Rough endoplasmicreticulums were significantly reduced, with a lot ofmicrofilament bundles or stress fibers appeared in cytoplasm,especially under plasma membrane. Dense bodies werescattered within these bundles. Macula densas anddiscontinuous sarcolemma were found under plasmamembrane. It suggested that the bile duct fibroblasts ofhypercholesterolemic rabbits presented the phenotype ofsmooth muscle cell. The cultured bile duct fibroblasts alsohad typical phenotype of fibroblasts. After stimulated bymiddle concentration cholesterol (0.6 g/L) for 72 h, thereappeared lots of microfilaments in cytoplasm, but withoutdense body, macula densa and discontinuous sarcolemma.Observed with confocal microscopy, there were many regularbundles of microfilaments in fibroblasts treated with middleconcentration ch (0.6 g/L) and the expression of α-actinwas signifiantly increased. The average fluorescence valueof middle concentration group was 1 628+189 (P＜0.01 vscontrol group). Microfilaments and the expression of α-actinwere greatly decreased in fibroblastes of high concentrationgroup (1.2 g/L). The average fluorescence value of highconcentration group was 1 427±153 (P＜0.05 vs middleconcentration group). There were a lower expression of α-actin and few microfilaments in bile duct fibroblasts of controlgroup with an average fluorescence value of 1 224±138.CONCLUSION: Cholesterol can make bile duct fibroblastshave the phenotypic characteristics of smooth muscle cellboth in vitro andin vivo and this effect is more significant invivo. The effect is probably associated with some otherfactors besides cholesterol.

Pathological characteristics of gastric leiomyoblastoma

AIM: To determine the pathological characteristics of gastric leiomyoblastoma.METHODS: All tissues were obtained during surgery or gastroscopy. Tissue specimens for examination by light microscope were 1 cmxl cmxl cm in size, fixed in 40 g/L neutral buffered formaldehyde, embedded in paraffin, and stained with hematoxylin and eosin. The fresh tissues obtained for electron microscopy were 1 mmxl mmxl mm in size, and fixed in phosphate buffered 30 g/L glutaraldehyde, postfixed in 10 g/L osmium tetroxide and dehydrated in graded alcohol, embebbed in Epon 812. UItrathin sections of 50 nm were stained with uranyl acetate and lead citrate and examined under a JEM-2000 EX transmission electron microscope.RESULTS: The most important histopathological feature of leiomyoblastoma was the predominance of large, rounded or polygonal cells with characteristic perinuclear clear zone in cytoplasms. The tumor cells arranged in patch, cell junction or junctional complex could be found occasionally between cells under electron microscope. Most of the neoplastic cytoplasms were filled with myofilaments, dense bodies, and dense patches. Rough endoplasmic reticulum dilatated as lakes, and large quantities of protein secretions of intermediate electron density were found in the dilated cisternae. Intracisternal segregation could also be found. The nuclei were round or oval, and anomalous nuclei were found in part of cells.CONCLUSION: The diagnosis of gastric leiomyoblastoma can be confirmed by electron microscopy. The clear appearance of tumor cells is due to the dilation of rough endoplasmic reticulum, not fat droplets, glycogens or mucus in cytoplasm.