Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously reported the identification of a hepatitis B virus (HBV) DNA integration in an intron of the cyclin A gene in an early hepatocellular carcinoma (HCC) and the isolation of human cyclin A cDNA. We have now constructed a cDNA library from the tumor and isolated several hybrid HBV-cyclin A cDNAs from it. The hybrid cDNAs encode an HBV-cyclin A fusion protein. In the chimeric protein, the N-terminus of cyclin A, including the signals for cyclin degradation, is deleted and replaced by viral PreS2/S sequences, transcription being initiated from the viral PreS2/S promoter. This chimeric protein is undegradable in an in vitro cyclin degradation assay. Northern blot analyses showed strong expression of the hybrid transcripts in the tumor, while cyclin A- or HBV-specific transcripts were not detected in the non-tumorous liver of the same patient. Thus, HBV DNA integration in the cyclin A gene resulted in a strong expression of hybrid HBV-cyclin A transcripts encoding a stabilized cyclin A. This chimeric protein may play an important role in the development of the tumor.
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PMID:Modification of cyclin A expression by hepatitis B virus DNA integration in a hepatocellular carcinoma. 132 6

The authors studied histochemically the morphologic features of proliferating hepatocytes positive for proliferating cell nuclear antigen (PCNA/cyclin) to analyze the process of liver regeneration in embedded tissues fixed with formaldehyde using an anti-PCNA/cyclin monoclonal antibody. In liver specimens from patients with acute viral hepatitis (AVH) and confluent necrosis, many small basophilic hepatocytes surrounding large clear hepatocytes were positively stained in the areas next to the confluent necrosis. Therefore these small hepatocytes may be daughter cells derived from large clear hepatocytes that probably enter the mitotic cell cycle repeatedly to repair a large necrotic area. In the case of AVH with spotty necrosis, the positively stained hepatocytes were scattered around the necrotic foci. In the liver specimens from patients with chronic active hepatitis, most of the positively stained hepatocytes were located next to the necrotic area. As for cirrhosis of the liver, the number of hepatocytes positive for PCNA/cyclin varied greatly in different pseudolobules, and in the specimens of hepatocellular carcinoma (HCC), the HCC cells positive for PCNA/cyclin were detected throughout the cancer nests.
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PMID:Analysis of proliferating hepatocytes using a monoclonal antibody against proliferating cell nuclear antigen/cyclin in embedded tissues from various liver diseases fixed in formaldehyde. 134 35

The authors investigated whether immunocytochemical staining with a monoclonal antibody to proliferating cell nuclear antigen (PCNA/cyclin) could be used to identify proliferative hepatocytes in frozen sections fixed in a mixture of periodate, lysine, and 2% paraformaldehyde. Paraffin sections also were used, which were fixed in 10% formaldehyde. Specimens of liver tissue were obtained from 27 patients with various hepatic diseases. Hepatocytes that were positive for PCNA/cyclin were observed in both types of substrate specimens. In acute hepatitis and chronic active hepatitis, most hepatocytes that were labeled for PCNA/cyclin were located near necrotic foci. However, in cirrhosis, they were detected most often near fibrotic septa; the number of immunoreactive cells varied greatly in different areas of tissue sections in such cases. In hepatocellular carcinoma, many PCNA/cyclin-positive tumor cells were seen throughout the neoplasms. Hepatocytes that were positive for DNA polymerase-alpha showed a similar distribution pattern in serial sections of study cases.
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PMID:Immunocytochemical identification of proliferative hepatocytes using monoclonal antibody to proliferating cell nuclear antigen (PCNA/cyclin). Comparison with immunocytochemical staining for DNA polymerase-alpha. 137 17

Maturation-promoting factor (MPF) is a cell cycle control element able to cause metaphase when injected into amphibian oocytes or when incubated with nuclei in a cell-free system. Highly purified MPF consists of a complex between a 34K (K = 10(3) Mr) serine/threonine protein kinase, identified as a Xenopus homolog of the cdc2+ gene product, p34cdc2, and a 45K substrate, identified as a Xenopus B-type cyclin. p34cdc2 is also present in purified preparations of chromatin-derived growth-associated histone H1 kinase from Novikoff hepatoma cells. p34cdc2 is active when dephosphorylated and inactive when phosphorylated during oocyte meiotic cell cycles and in mitotic cell cycles following egg activation. Analysis of the substrate specificity of p34cdc2 indicates a consensus sequence for phosphorylation of (K/R)S/TP(X)K/R. Among substrates identified with this consensus are histone H1 and the pp60c-src proto-oncogene, which is known to be activated and phophorylated in mitosis. MPF injection into oocytes activates ribosomal protein S6 kinase II, which is also a lamin kinase. The mechanism of activation is indirect, possibly involving the c-src proto-oncogene. Continued analysis of regulation of MPF activation/inactivation and characterization of substrates for phosphorylation will have important implications for cell cycle and cell growth control.
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PMID:Maturation-promoting factor and the regulation of the cell cycle. 269 38

To evaluate the correlation between the polyamine metabolism and the degree of malignancy in hepatocellular carcinoma, we measured ornithine decarboxylase activity and polyamine concentrations in neoplastic tissue and adjacent noncancerous tissue from resected specimens of liver from 30 patients. Ornithine decarboxylase activity, polyamines (putrescine, spermidine and spermine) and ornithine decarboxylase mRNA levels were significantly higher in hepatoma tissue than in noncancerous tissue. The activity of this enzyme in the tumor tissue had a negative correlation with the histological degree of differentiation judged according to a modification of the Edmondson and Steiner classification. Resected hepatoma tissue was stained immunohistochemically with antibodies for proliferating cell nuclear antigen (also called cyclin), a marker of cell proliferation. We noted correlation between ornithine decarboxylase activity and the number of cells stained for this antigen (r = 0.882, p < 0.001). These results indicate that ornithine decarboxylase activity is high in human hepatocellular carcinoma, leading to increased intracellular concentrations of polyamines. Ornithine decarboxylase activity also reflected the rate of tumor proliferation and was correlated with the histological findings.
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PMID:Relationship of ornithine decarboxylase activity and histological findings in human hepatocellular carcinoma. 792 50

The recently cloned protein, p21 (WAF1/CIP1) is a downstream effector of p53, and mediates growth arrest by inhibiting the action of G1 cyclin-dependent kinases. Since cellular differentiation is frequently characterized by G1 arrest, we examined whether p21 upregulation occurs in differentiation. We show that p21 expression is triggered by multiple differentiation-inducing agents in hematopoietic and hepatoma cells through a p53-independent pathway. The dramatic rise in p21 levels occurs as an immediate early response to differentiation inducers. The induction of p21 is coupled to the expression of early differentiation markers, and is uncoupled from apoptosis. Finally, evidence is presented that p21 expression is uncoupled from G1 arrest in the presence of deregulated c-myc.
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PMID:Induction of p21 (WAF-1/CIP1) during differentiation. 793 67

Proliferating cell nuclear antigen (PCNA), also known as cyclin, is an auxiliary protein of DNA polymerase-delta and is found only in the nuclei of proliferating cells in the late G1 and S phases. The proliferation of hepatocellular carcinoma (HCC) by immunohistochemical staining for PCNA using paraffin sections of 20 surgically resected HCC specimens was analysed. The mean percentage of PCNA-positive nuclei in the HCC tissue was 10.3% in grade I of Edmondson and Steiner's classification, 25.5% in grade II, 28.4% in grade III and 41.5% in grade IV. In early HCC, we observed only a few PCNA-positive tumour cells. However, PCNA-positive nuclei were numerous in the tumour thrombi found in portal vein branches, in regions of extracapsular tumour growth, and in the inner nodules of tumours with a nodule-in-nodule formation. Proliferating cell nuclear antigen positivity was correlated with an increase of the nucleocytoplasmic ratio of tumour cells as determined by image analysis. Our findings showed that PCNA positivity was correlated with the histological grade and invasiveness of HCC, suggesting that this antigen may be used as an indicator to predict tumour invasion in patients with HCC.
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PMID:Immunohistochemical detection of proliferating cell nuclear antigen in hepatocellular carcinoma: relationship to histological grade. 810 98

Mitotic cyclins constitute a regulatory subunit of the histone H1 kinase complex. On the ground of their primary structure they are divided into two classes A and B, both necessary for the mitosis. Cyclin A activates histone H1 kinase and becomes destroyed by proteolysis earlier than cyclines B and plays an important role in the DNA replication. Cyclins A and B may be involved in the development of neoplastic disorders either directly (inappropriate expression of the cyclin A gene caused by hepatitis B virus in hepatocellular carcinoma, or interactions of this cyclin with factors participating in the regulation of cell proliferation) or indirectly by phosphorylation of some oncogene or antioncogene proteins by a cdk (cyclin dependent kinase).
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PMID:[Mitotic cyclins--new possibilities for examining mechanisms of neoplasm growth]. 823 85

Mitotic cyclins constitute a regulatory subunit of the histone H1 kinase complex. On the basis of primary structure differences, they are divided into two classes, A and B. Both classes are necessary for mitosis to occur. Cyclins A and B differ in the timing of their cellular expression and in their affinity with the various members of the cdk (cyclin-dependent kinases) family. They also have specific functions: cyclin A plays a role in DNA replication, whereas cyclin B are involved in the inhibition of the fusion of early endosomes and in the activation of cdc25 phosphatase. Cyclins A and B can contribute to the development of neoplastic disorders, either directly (inappropriate expression of the cyclin A gene caused by the hepatitis B virus in hepatocellular carcinoma, interactions between cyclin A and factors involved in the regulation of cell division), or indirectly by causing phosphorylation of oncogene products by a cdk.
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PMID:[Cyclins A and B: redundancy and specificity]. 824 35

A protein kinase inhibitor K252a suppressed the growth of HuH7 hepatoma cells and the hyperphosphorylation of retinoblastoma protein (pRb) at late G1 phase of cell cycle. However, K252a treatment did not alter the levels of cyclin D1, cyclin E, cyclin A and Cdk2 protein bound to cyclin E or cyclin A. Therefore, the K252a inhibition of pRb phosphorylation is considered to be brought about probably by inhibiting the action of Cdk-cyclin complex rather than by changing its cellular level. These results also suggest that K252a is a useful tool for investigating the mechanism of phosphorylation of pRb mediated by Cdk-cyclin.
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PMID:K252a inhibits the phosphorylation of pRb without changing the levels of G1 cyclins and Cdk2 protein in human hepatoma cells. 869 9


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