ABSTRACT
BACKGROUND: Hepatoma cells are morphologically different from those of the normal liver. Intermediate filaments (IFs) are important in building the cellular architecture and maintaining the outline of cells. Plectin is a cross-linking protein that organizes the cytoskeleton into a stable meshwork, which can maintain the uniform size and shape of hepatocytes. Apoptosis might be the most possible pathway for creating plectin deficiency in the in vivo state. MATERIALS AND METHODS: Apoptosis was induced by staurosporine (STS) treatment in liver cells. The protein expression of cytokeratin 18 (CK18) and plectin as well as the morphology of the liver cells and the distribution of CK18 and plectin in the cells was studied after STS treatment. RESULTS: Plectin was cleaved in the liver cells during apoptosis and CK18 was modulated. Morphological changes were observed in the liver cells. CONCLUSION: By affecting the organization of IFs, plectin might play an important role in the pleomorphism of hepatoma cells and even the tumorigenesis of hepatoma.
Subject(s)
Apoptosis/drug effects , Keratin-18/metabolism , Liver/drug effects , Plectin/metabolism , Staurosporine/pharmacology , Blotting, Western , Fluorescent Antibody Technique , Humans , Liver/cytology , Liver/metabolism , Tumor Cells, CulturedABSTRACT
BACKGROUND: Previously we found some low molecular weight proteins identified as histone in hepatocelluar carcinoma. Our objective was to clarify whether the coimmunoprecipitation of histone and cytokeratin 18 was an artifact or not. MATERIALS AND METHODS: Histone 3 and cytokeratin 18 were investigated in three cases of human hepatocellular carcinoma and one case of normal liver tissue. Nuclei of the tissues were isolated; the proteins inside the nuclei were analyzed by Western blot. RESULTS: The results revealed histone was co-immunoprecipitated with cytokeratin 18 in hepatocellular carcinoma. It was speculated that modulation of the cytoskeleton in human hepatocellular carcinoma might disturb the organization of the nucleoskeleton. The unstable nucleoskeleton might further cause instability and fragility of nuclei, thus possibly exposing the histone and co-immunoprecipitating it with cytokeratin 18. CONCLUSION: The evidence might indicate that expression of histone 3 was highly related to modulation of cytokeratin 18 and might play an important role in tumorigenesis of hepatocellular carcinoma.
Subject(s)
Carcinoma, Hepatocellular/metabolism , Gene Expression Regulation, Neoplastic , Histones/physiology , Keratin-18/physiology , Liver Neoplasms/metabolism , Cell Nucleus/metabolism , Chromatin/metabolism , Histones/biosynthesis , Humans , Immunoprecipitation , Keratin-18/biosynthesis , Keratins/metabolism , Liver/metabolismABSTRACT
Intermediate filaments are important in building the cellular architecture. Previously we found cytokeratin18 was modulated in human hepatocellular carcinoma. Plectin is a cross-linking protein that organizes the cytoskeleton into a stable meshwork, which can maintain the uniform size and shape of hepatocytes. Because the cells of hepatocellular carcinoma were morphologically different from the hepatocytes, we speculated that expression of plectin and organization of intermediate filament might play roles in the pleomorphism of hepatocellular carcinoma cells. In this paper, we studied the plectin expression of hepatocellular carcinoma and liver tissues by immunohistochemistry and immunoblot. The results revealed that plectin was deficient and cytokeratin18 was modulated in hepatocellular carcinoma. Furthermore, we knockdown the plectin mRNA in Chang cells, the result revealed the plectin was deficient and the organization of cytokeratin18 was altered. Conclusively, this study offers a hypothesis that plectin deficient might play an important role in the tumorigenesis of hepatocellular carcinoma.
Subject(s)
Carcinoma, Hepatocellular/metabolism , Keratin-18/metabolism , Liver Neoplasms/metabolism , Plectin/deficiency , Plectin/metabolism , Carcinoma, Hepatocellular/ultrastructure , Humans , Immunoblotting , Immunohistochemistry , Keratin-18/ultrastructure , Liver Neoplasms/ultrastructure , Plectin/antagonists & inhibitorsABSTRACT
Intermediate filaments are important in building the architecture of liver cells and are proposed to interact with other cellular components. Among intermediate filament associated proteins, plectin is a versatile cytoskeletal linkage protein which has been shown to interact with a variety of cytoskeletal structures. Intermediate filament and plectin might play some roles in tumorigenesis of human hepatocellular carcinoma since cells of hepatocellular carcinoma were morphologically different from normal liver. Plectin exhibited wide distribution spectrum among various tissues, however, it was poorly investigated in human liver and hepatoma tissues. In this paper, we studied the plectin expression in 18 cases of human hepatocellular carcinoma and normal hepatocytes by immunohistochemistry. The results revealed that plectin expression was deficient in human hepatocellular carcinoma and was probably through post-translational modification. Many 0.4 to 0.8 microm-thick keratin bundles were found in intermediate filament extracts of liver and hepatoma tissues. These bundles were greater in diameter about 40 to 80 times of single intermediate filament. We speculated that intermediate filament organized into "filament bundles" to maintain the shape of normal cells. In cancer cells, plectin was deficient and the irregularly loosened filament bundles could cause pleomorphism of cancer cells.
