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)

Transforming growth factor beta (TGF-beta)-mediated G(1) arrest previously has been shown to specifically target inactivation of cyclin D:cyclin-dependent kinase (Cdk) 4/6 complexes. We report here that TGF-beta-treated human HepG2 hepatocellular carcinoma cells arrest in G(1), but retain continued cyclin D:Cdk4/6 activity and active, hypophosphorylated retinoblastoma tumor suppressor protein. Consistent with this observation, TGF-beta-treated cells failed to induce p15(INK4b), down-regulate CDC25A, or increase levels of p21(CIP1), p27(KIP1), and p57(KIP2). However, TGF-beta treatment resulted in the specific inactivation of cyclin E:Cdk2 complexes caused by absence of the activating Thr(160) phosphorylation on Cdk2. Whole-cell lysates from TGF-beta-treated cells showed inhibition of Cdk2 Thr(160) Cdk activating kinase (CAK) activity; however, cyclin H:Cdk7 activity, a previously assumed mammalian CAK, was not altered. Saccharomyces cerevisiae contains a genetically and biochemically proven CAK gene, CAK1, that encodes a monomeric 44-kDa Cak1p protein unrelated to Cdk7. Anti-Cak1p antibodies cross-reacted with a 45-kDa human protein with CAK activity that was specifically down-regulated in response to TGF-beta treatment. Taken together, these observations demonstrate that TGF-beta signaling mediates a G(1) arrest in HepG2 cells by targeting Cdk2 CAK and suggests the presence of at least two mammalian CAKs: one specific for Cdk2 and one for Cdk4/6.
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PMID:Transforming growth factor beta targeted inactivation of cyclin E:cyclin-dependent kinase 2 (Cdk2) complexes by inhibition of Cdk2 activating kinase activity. 1061 20

The nuclear matrix (nuclear scaffold), the RNA-protein skeleton of the nucleus, has a role in the organization and function of nuclear DNA. Nuclear processes associated with the nuclear matrix include transcription, replication, repair and splicing. We have purified a nuclear matrix protein, P130, which binds to several matrix attachment regions (MARs). Since the nucleotide sequence of P130 cDNA cloned by us was closely similar to that of matrin 3 cDNA cloned, except for two incorrect nucleotides within the matrin 3 coding region, and since the functions of matrin 3 were unknown, P130, referred to as P130/Mat3, was functionally characterized. The primary structure deduced for P130/Mat3 contained two DNA binding domains with C2H2-type zinc finger motif and two RNA binding domains. In addition, there were a nuclear localization signal and several phosphorylation sites for tyrosine or serine/threonine protein kinases, suggesting its multiple functions. MAR inserted upstream from the SV40 promoter in pMAR/luc assisted luciferase gene transcription in a transient expression system in Ac2F cells. Cotransfection of a plasmid carrying P130/Mat3 cDNA downstream from the CMV promoter into Ac2F cells produced this protein a level 4 times higher than that in wild-type Ac2F, causing 20 times higher luciferase activity from pMAR/luc than that induced by pMAR/luc alone. These findings indicated that MAR functions as a cis-element to which P130/Mat3 binds as one of the possible transactivators. Nuclear matrix proteins, which are tissue- and cell-type-specific, are altered with transformation and state of differentiation. We have shown that an MAR binding protein, P230, is detectable in rat hepatoma cells but not in normal liver, and suggested that this protein is a diagnostic and prognostic marker for liver cancer. It is clear that nuclear matrix proteins hold a considerable promise as diagnostic tools for pathologists. Present evidence, including our data, suggests that nuclear matrix proteins may be useful biomarkers of neoplastic disease in the serum, body fluids, and tissues. Nuclear matrix proteins are also potential candidates for the use as tumor prognostic factors and targets of anticancer drugs through apoptosis. We will discuss screening of drugs that interact with nuclear matrix proteins and influence nuclear events.
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PMID:[Functional arrangement of genomic DNA and structure of nuclear matrix]. 1086 Apr 85

To better understand the role of beta-catenin mutation in hepatocellular carcinoma (HCC), we correlated the gene mutation with hepatitis virus B (HBV) and hepatitis virus C (HCV) status and the clinicopathological features in 366 patients with resected primary unifocal HCC. beta-Catenin mutations were also analyzed in 55 patients with multifocal HCC (68 tumors). Of the whole series, 57 (13.1%) of 434 tumors examined had beta-catenin mutations, 34 occurred at the serine/threonine residues of the GSK-3beta region of beta-catenin. Outside the GSK-3beta phosphorylation site, codons 32 and 34 were two mutational hot spots (17 tumors). The non-HBV-related HCC that was predominantly HCV related had a higher frequency of mutation (P: < 0.00001) and more frequent mutations at codon 45 than HBV-related HCC. HBV-related HCC had a younger mean age (P: < 0.00001), and higher male-to-female ratio (P: < 0.003) and positive familial history of HCC (P: < 0.014). Among 366 unifocal HCCs selected for clinicopathological analysis, beta-catenin mutations were associated with grade I (P: = 0.005) and stage I and II HCC (P: < 0.0001), and a better 5-year survival rate (P: = 0. 00003). These findings suggest mechanisms for beta-catenin mutations differ between HBV-related and non-HBV-related HCCs, and that beta-catenin mutation is a favorable prognostic factor related to low stage. beta-Catenin mutation was associated with nuclear expression of the protein (P: < 0.00001), but we failed to detect point or large fragment deletion mutation in 39 HCCs with nuclear beta-catenin expression, presumably wild-type protein. HCCs expressing mutant nuclear beta-catenin had a better 5-year survival rate (P: < 0.007), suggesting that mutant and wild-type nuclear beta-catenin proteins are not functionally equivalent and deserve more studies for further clarification.
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PMID:Beta-catenin mutations are associated with a subset of low-stage hepatocellular carcinoma negative for hepatitis B virus and with favorable prognosis. 1098 Jan 16

The cyclin-dependent kinase (Cdk)-associated protein phosphatase (KAP) is a human dual specificity protein phosphatase that dephosphorylates Cdk2 on threonine 160 in a cyclin-dependent manner. To investigate whether mutations of this enzyme occur in hepatocellular carcinoma (HCC), KAP mRNA was analyzed by reverse transcription-PCR (RT-PCR), followed by cloning and sequencing. Eight of 14 biopsy tissues obtained from advanced HCC, 6 of 13 surgically removed HCC tissues, and 2 of the adjacent noncancerous tissues contained aberrant KAP transcripts. Using the yeast two-hybrid system, five of seven representative KAP mutants were shown to be defective in interacting with Cdk2. These data suggest a possible role of KAP mutations in multiple-step hepatocarcinogenesis.
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PMID:Aberrant transcripts of the cyclin-dependent kinase-associated protein phosphatase in hepatocellular carcinoma. 1098 70

Aldolase B is an abundant cytosolic protein found in all eukaryotic cells. Like many glycolytic enzymes, this protein was sequestered into lysosomes for degradation during nutrient starvation. We report here that the degradation of recombinant aldolase B was enhanced two-fold when rat and human hepatoma cells were starved for amino acid and serum. In addition, starvation-induced degradation of aldolase B was inhibited by chloroquine, an inhibitor of lysosomal proteinases and by 3-methyladenine, an inhibitor of autophagy. Aldolase B has three lysosomal targeting motifs (Q(12)KKEL, Q(58)FREL, and IKLDQ(111)) that have been proposed to interact with hsc73 thereby initiating its transport into lysosomes. In this study, we have mutated the essential glutamine residues in each of these hsc73-binding motifs in order to evaluate their roles in the lysosomal degradation of aldolase B during starvation. We have found that when glutamines 12 or 58 are mutated to asparagines enhanced degradation of aldolase B proceeded normally. However, when glutamine 111 was mutated to an asparagine or a threonine, starvation-induced degradation was completely suppressed. These mutations did not appear to alter the tertiary structure of aldolase B since enzymatic activity was not affected. Our results suggest that starvation-induced lysosomal degradation of aldolase B requires both autophagy and glutamine 111. We discuss the possible roles for autophagy and hsc73-mediated transport in the lysosomal sequestration of aldolase B.
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PMID:Starvation-induced lysosomal degradation of aldolase B requires glutamine 111 in a signal sequence for chaperone-mediated transport. 1124 48

Incubation of rat hepatoma Fao cells with insulin leads to a transient rise in Tyr phosphorylation of insulin receptor substrate (IRS) proteins. This is followed by elevation in their P-Ser/Thr content, and their dissociation from the insulin receptor (IR). Wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor, abolished the increase in the P-Ser/Thr content of IRS-1, its dissociation from the IR, and the decrease in its P-Tyr content following 60 min of insulin treatment, indicating that the Ser kinases that negatively regulate IRS-1 function are downstream effectors of PI3K. PKCzeta fulfills this criterion, being an insulin-activated downstream effector of PI3K. Overexpression of PKCzeta in Fao cells, by infection of the cells with adenovirus-based PKCzeta construct, had no effect on its own, but it accelerated the rate of insulin-stimulated dissociation of IR.IRS-1 complexes and the rate of Tyr dephosphorylation of IRS-1. The insulin-stimulated negative regulatory role of PKCzeta was specific and could not be mimic by infecting Fao cells with adenoviral constructs encoding for PKC alpha, delta, or eta. Because the reduction in P-Tyr content of IRS-1 was accompanied by a reduced association of IRS-1 with p85, the regulatory subunit of PI3K, it suggests that this negative regulatory process induced by PKCzeta, has a built-in attenuation signal. Hence, insulin triggers a sequential cascade in which PI3K-mediated activation of PKCzeta inhibits IRS-1 functions, reduces complex formation between IRS-1 and PI3K, and inhibits further activation of PKCzeta itself. These findings implicate PKCzeta as a key element in a multistep negative feedback control mechanism of IRS-1 functions.
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PMID:Insulin stimulates PKCzeta -mediated phosphorylation of insulin receptor substrate-1 (IRS-1). A self-attenuated mechanism to negatively regulate the function of IRS proteins. 2975 17

Insulin induces apolipoprotein A-I, apoA-I gene transcription via a membrane receptor with intrinsic tyrosine kinase activity. This finding prompted us to ask whether the gene is stimulated by epidermal growth factor (EGF), EGF a peptide hormone that binds to another member of the receptor superfamily with tyrosine kinase activity. Our data showed that like insulin, EGF increased abundance of apoA-I protein and transcription of the gene in human hepatoma, Hep G2 cells. The effects of both hormones appeared direct because their induction of apoA-I gene transcription was not affected by the protein synthesis inhibitor, cycloheximide. Although both insulin and EGF stimulate apoA-I expression, each hormone binds to a distinct membrane receptor thus suggesting differential intracellular signaling. Therefore, we used a panel of inhibitors to define the pathway(s) that mediate the actions of these hormones. Whereas, the actions of EGF required only the Ras-mitogen-activated protein, MAP kinase, those of insulin were mediated by equal participation of both the Ras-MAP kinase and protein kinase C, PKC cascades. Despite differences in signaling pathways triggered by each hormone receptor, the activation of apoA-I transcription required the participation of a single transcription factor, Sp1. Furthermore, EGF induction of transcription was attenuated by mutating the MAP kinase site at amino acid, Thr(266) rendering Sp1 phosphorylation deficient. In summary, EGF stimulation of apoA-I expression is mediated solely by the Ras-MAP kinase cascade and enhanced activity of this pathway requires Sp1 with an intact phosphorylation site at Thr(266). However, insulin induction of this gene is different and requires both Ras-MAP kinase and PKC pathways but their actions are also mediated by Sp1.
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PMID:Epidermal growth factor induction of apolipoprotein A-I is mediated by the Ras-MAP kinase cascade and Sp1. 1127 17

The hepatitis B virus-X (HBx) protein is known as a multifunctional protein that not only coactivates transcription of viral and cellular genes but coordinates the balance between proliferation and programmed cell death, by inducing or blocking apoptosis. In this study the role of the HBx protein in activation of phosphatidylinositol 3-kinase (PI3K) was investigated as a possible cause of anti-apoptosis in liver cells. HBx relieved serum deprivation-induced and pro-apoptic stimuli-induced apoptosis in Chang liver (CHL) cells. Treatment with 1-d-3-deoxy-3-fluoro-myo-inositol, an antagonist to PI3K, which blocks the formation of 3'-phosphorylated phosphatidyl inositol in CHL cells transformed by HBx (CHL-X) but not normal Chang liver (CHL) cells, showed a marked loss of viability with evidence of apoptosis. Similarly, treatment with wortmannin, an inhibitor of PI3K, stimulated apoptosis in HBx-transformed CHL cells but not in normal cells, confirming that HBx blocks apoptosis through the PI3K pathway. The serine 47 threonine kinase, Akt, one of the downstream effectors of PI3K-dependent survival signaling was 2-fold higher in HBx-transformed CHL (CHL-X) cells than CHL cells. Phosphorylation of Akt at serine 473 and Bad at serine 136 were induced by HBx, which were specifically blocked by wortmannin and dominant negative mutants of Akt and Bad, respectively. We also demonstrated that HBx inhibits caspase 3 activity and HBx down-regulation of caspase 3 activity was blocked by the PI3K inhibitor. Regions required for PI3K phosphorylation on the HBx protein overlap with the known transactivation domains. HBx blocks apoptosis induced by serum withdrawal in CHL cells in a p53-independent manner. The results indicate that, unlike other DNA tumor viruses that block apoptosis by inactivating p53, the hepatitis B virus achieves protection from apoptotic death through a HBx-PI3K-Akt-Bad pathway and by inactivating caspase 3 activity that is at least partially p53-independent in liver cells. Moreover, these data suggest that modulation of the PI3K activity may represent a potential therapeutic strategy to counteract the occurrence of apoptosis in human hepatocellular carcinoma.
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PMID:The hepatitis B virus-X protein activates a phosphatidylinositol 3-kinase-dependent survival signaling cascade. 1127 72

Here we report a quick functional analysis of two mammalian serine/threonine kinases, a serum inducible kinase (Snk) and Homo sapiens hepatoma protein kinase (HsHPK), using Drosophila eye as a model system. We generated transgenic fly lines carrying constructs of both kinases under control of the GAL upstream activating sequence (UAS). Each UAS line was then crossed to a line in which GAL4 expression was driven by one of the following promoters, eyeless (ey), glass or decapentaplegic. Thus, different kinase mutants can be ectopically expressed in a promoter-dependent manner. We observed that the ectopic expression of either the wild-type or active form of Snk driven by the glass promoter resulted in a rough-eye phenotype. Nevertheless, the ectopic expression of HsHPK under the control of the ey promoter resulted in a small-eye phenotype. The results of this study demonstrated that ectopic expression of these two mammalian genes could be achieved by the regulation of Drosophila promoters. In addition, the effects of these ectopically expressed genes on eye development could be an implication of their functions with respect to cell proliferation and differentiation. Thus, Drosophila eye, with the powerful genetic tools and vast information on eye development available, can be a useful system to probe the functions of mammalian genes in the postgenome era.
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PMID:Utilization of Drosophila eye to probe the functions of two mammalian serine/threonine kinases, Snk and HsHPK. 1138 99

The molecular details of hypoxia-induced cellular responses have been difficult to identify since there is as yet no known oxygen receptor. We used cDNA microarray technology to extend our studies pertaining to these molecular details in human hepatocellular carcinoma (Hep3B) cells that produce erythropoietin (Epo) in response to hypoxia. Of approximately 1200 genes in the array, those associated with integrin-linked kinase (ILK), fibronectin precursor and glycogen synthase kinase-3beta (GSK-3beta) were markedly stimulated after exposure of Hep3B cells to low oxygen (1%) for 6 h. Epo, HIF-1, and von Hippel-Lindau cDNAs were measured in parallel as markers of low oxygen responses in Hep3B cells. ILK is a serine, threonine protein kinase that interacts with the cytoplasmic domains of integrin beta1 and beta3. This interaction localizes ILK to focal adhesion plaques. ILK is stimulated by cell-fibronectin interaction as well as insulin. It is regulated in a phosphatidylinositol 3-kinase dependent manner and can phosphorylate protein kinase B (PKB/AKT) and GSK-3beta. As a result of these and other activities ILK has been shown to affect anchorage-independent cell survival, cell cycle progression and tumorigenesis in nude mice. ILK has also been implicated in the Wnt pathway and as a critical target in PTEN-dependent tumor therapies. To our knowledge this is the first report implicating the ILK pathway in low oxygen responses. Other genes identified as a result of the microarray analysis not previously known to change as a result of low oxygen treatment were elongation factor-1alpha, glycyl-tRNA synthetase, and laminin receptor protein-1. These findings were all corroborated by RT-PCR assays and in some instances Western blot analysis.
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PMID:Gene microarray analysis reveals a novel hypoxia signal transduction pathway in human hepatocellular carcinoma cells. 1140 33


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