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 shown previously that administration of acyclic retinoid to cirrhotic patients who had undergone curative treatment of preceding hepatocellular carcinoma (HCC) induced the disappearance of serum lectin-reactive alpha-fetoprotein (AFP-L3) and subsequently reduced the incidence of second liver cancers. AFP-L3 is a tumor marker that indicates the presence of occult tumors below the detection limit by diagnostic images. Therefore, we have proposed a new concept of 'clonal deletion' therapy with acyclic retinoid for the cancer chemoprevention against HCC. Such eradication of AFP-L3-producing latent malignant (or premalignant) cells from the liver suggested a new strategy to prevent HCC, which may be involved in the same category as cancer chemotherapy. In the present series of studies, we explored the molecular mechanism of 'clonal deletion' and found a novel mechanism of apoptosis induction by the retinoid. We have demonstrated a modification of a retinoid receptor, RXRalpha, by mitogen-activated protein (MAP) kinase-dependent phosphorylation, resulting in the loss of transactivating activity. This may lead HCC cells to be resistant to natural retinoic acid. However, acyclic retinoid restored the function of phosphorylated RXRalpha and induced its downstream pro-apoptotic genes including tissue transglutaminase, an enzyme that is implicated in apoptosis. Tissue transglutaminase-dependent apoptosis in HCC cells was independent of the activation of caspases. This novel mechanism of retinoid-induced apoptosis may give a clue to understand the molecular mechanism of clonal deletion.
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PMID:Apoptosis induction by acyclic retinoid: a molecular basis of 'clonal deletion' therapy for hepatocellular carcinoma. 1157 27

Retinoid X receptor alpha (RXRalpha) has emerged as an important nuclear receptor involved in hepatocarcinogenesis, because its ligand suppresses the development of hepatocellular carcinoma (HCC) in both experimental and clinical studies. We have demonstrated that phosphorylation of RXRalpha at serine 260 interferes with its function and delays its degradation in cultured human HCC, leading to enhanced cellular proliferation. Here, we show that in normal liver and in nonproliferating hepatocyte cultures, RXRalpha is unphosphorylated and highly ubiquitinated, rendering it sensitive to proteasome-mediated degradation. On the other hand, phosphoserine 260 RXRalpha is resistant to ubiquitination and proteasome-mediated degradation in both human HCC tissues and a human HCC cell line, HuH7. In these tissues and cells, serine 260 is phosphorylated by mitogen-activated protein (MAP) kinase. In proliferating normal hepatocytes, similar to HCC cells, RXRalpha is also phosphorylated at serine 260 and resistant to ubiquitin-mediated degradation by proteasome, but this ubiquitination of RXRalpha is differentially regulated between HCC cells and normal hepatocytes. In proliferating hepatocytes, 9-cis retinoic acid (9cRA), a ligand to RXRalpha, suppresses MAP kinase-mediated phosphorylation and thereby enhances ubiquitination of RXRalpha, whereas it fails to exert these effects in HCC cells. In conclusion, switching of the ubiquitin/proteasome-dependent degradation of RXRalpha by phosphorylation at serine 260 may be responsible for the aberrant growth of HCC and its suppression by retinoids.
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PMID:Phosphorylation of retinoid X receptor suppresses its ubiquitination in human hepatocellular carcinoma. 1182 6

Transforming growth factor (TGF) beta1 is a potent inducer of apoptosis in the liver. During TGF-beta1-induced apoptosis, 3 mitogen-activated protein (MAP) kinases (extracellular signal-regulated kinase [ERK], c-Jun N-terminal kinase [JNK], and p38 kinase) showed simultaneously sustained activation in FaO rat hepatoma cells. TGF-beta1-induced apoptosis was markedly enhanced when ERK activation was selectively inhibited by the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor PD98059. In contrast, both interfering with p38 activity by overexpression of the dominant negative (DN) MKK6 mutant and inhibition of the JNK pathway by overexpression of the DN SEK1 mutant resulted in suppression of mitochondrial cytochrome c release, abrogating TGF-beta1-induced apoptosis. In addition, antiapoptotic Bcl-2 blocked mitochondrial cytochrome c release, suppressing TGF-beta1-induced activation of JNK and p38. Inhibition of ERK activity enhanced TGF-beta1-induced p38 and JNK activation. However, inhibition of the JNK pathway suppressed p38 but induced transient ERK activation. Similarly, interfering with the p38 pathway also attenuated JNK activation but generated transient ERK activation in response to TGF-beta1. These results indicate that disrupting one MAP kinase pathway affects the TGF-beta1-induced activation of other MAP kinases, suggesting cross-talk among MAP kinase pathways. In conclusion, we propose that the balance and integration of MAP kinase signaling may regulate commitment to TGF-beta1-induced apoptosis modulating the release of cytochrome c from mitochondria.
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PMID:Role of MAP kinases and their cross-talk in TGF-beta1-induced apoptosis in FaO rat hepatoma cell line. 1202 21

Reactive oxygen species (ROS) are important for intracellular signaling mechanisms regulating many cellular processes. Manganese superoxide dismutase (MnSOD) may regulate cell growth by changing the level of intracellular ROS. In our study, we investigated the effect of ROS on 7721 human hepatoma cell proliferation. Treatment with H2O2 (1-10 microM) or transfection with antisense MnSOD cDNA constructs significantly increased the cell proliferation. Recently, the mitogen-activated protein kinases (MAPK) and the protein kinase B (PKB) were proposed to be involved in cell growth. Accordingly, we assessed the ability of ROS to activate MAPK and PKB. PKB and extracellular signal-regulated kinase (ERK) were both rapidly and transiently activated by 10 microM H2O2, but the activities of p38 MAPK and JNK were not changed. ROS-induced PKB activation was abrogated by the phosphatidylinositol 3-kinase (PI3-K) inhibitor LY294002, suggesting that PI3-K is an upstream mediator of PKB activation in 7721 cells. Transfection with sense PKB cDNA promoted c-fos and c-jun expression in 7721 cells, suggesting that ROS may regulate c-fos and c-jun expression via the PKB pathway. Furthermore we found that exogenous H2O2 could stimulate the proliferation of PKB-AS7721 cells transfected with antisense PKB cDNA, which was partly dependent on JNK activation, suggesting that H2O2 stimulated hepatoma cell proliferation via cross-talk between the PI3-K/PKB and the JNK signaling pathways. However, insulin could stimulate 7721 cell proliferation, which is independent of cross-talk between PI3-K/PKB and JNK pathways. In addition, H2O2 did not induce the cross-talk between the PI3-K/PKB and the JNK pathways in normal liver cells. Taken together, we found that ROS regulate hepatoma cell growth via specific signaling pathways (cross-talk between PI3-K/PKB and JNK pathway) which may provide a novel clue to elucidate the mechanism of hepatoma carcinogenesis.
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PMID:Reactive oxygen species stimulated human hepatoma cell proliferation via cross-talk between PI3-K/PKB and JNK signaling pathways. 1236 5

A contribution of intracellular dehydration to insulin resistance has been established in human subjects and in different experimental systems. Here the effect of hyperosmolarity (405 mosmol/l) on insulin-induced mitogen-activated protein (MAP) kinase phosphatase (MKP)-1 expression was studied in H4IIE rat hepatoma cells. Insulin induces robust MKP-1 expression which correlates with a vanadate-sensitive decay of extracellular-signal-regulated kinase (Erk-1/Erk-2) activity. Hyperosmolarity delays MKP-1 accumulation by insulin and this corresponds to impaired MKP-1 synthesis, whereas MKP-1 degradation remains unaffected by hyperosmolarity. Rapamycin, which inhibits signalling downstream from the mammalian target of rapamycin (mTOR) and a peptide inhibiting protein kinase C (PKC) zeta/lambda abolish insulin-induced MKP-1 protein but not mRNA expression, suggesting the involvement of the p70 ribosomal S6 protein kinase (p70S6-kinase) and/or the eukaryotic initiation factor 4E-binding proteins (4E-BPs) as well as atypical PKCs in MKP-1 translation. Hyperosmolarity induces sustained suppression of p70S6-kinase and 4E-BP1 hyperphosphorylation by insulin, whereas insulin-induced tyrosine phosphorylation of the insulin receptor (IR) beta subunit and the IR substrates IRS1 and IRS2, recruitment of the phosphoinositide 3-kinase (PI 3-kinase) regulatory subunit p85 to the receptor substrates as well as PI 3-kinase activation, and Ser-473 phosphorylation of protein kinase B and Thr-410/403 phosphorylation of PKC zeta/lambda are largely unaffected under hyperosmotic conditions. The hyperosmotic impairment of both, MKP-1 expression and p70S6-kinase hyperphosphorylation by insulin is insensitive to K(2)CrO(4), calyculin A and vanadate, and inhibition of the Erk-1/Erk-2 and p38 pathways. The suppression of MKP-1 may further contribute to insulin resistance under dehydrating conditions by allowing unbalanced MAP kinase activation.
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PMID:Osmotic regulation of insulin-induced mitogen-activated protein kinase phosphatase (MKP-1) expression in H4IIE rat hepatoma cells. 1252 77

Norcantharidin (NCTD) is an anticancer drug routinely used against hepatoma in China. Previously, we reported that NCTD could induce mitotic arrest and apoptosis in human hepatoma HepG2 cells. However, the intracellular signaling pathways involved in NCTD-induced apoptotic cell death are still obscure. Caspase inhibitors were used to clarify the role of specific caspase in NCTD-triggered apoptotic process. Results showed that activation of caspase-9/caspase-3 cascade is required for NCTD-induced apoptotic death. To decipher the upstream signals for NCTD-induced apoptosis, we characterized the involvement of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38MAPK. The role of their downstream targets, transcription factors activating protein-1 (AP-1), and nuclear factor kappaB (NF-kappaB) in NCTD-induced apoptosis was also analyzed. Immunoblot analyses and in vitro kinase assay demonstrated that NCTD-induced apoptosis was accompanied by the elevations of the levels of phosphorylated form and kinase activity of ERK and JNK, but not p38MAPK. The inhibitor of ERK pathway (U0126 or PD98059) or JNK pathway (SP600125) markedly prevented kinase activation, and also greatly reduced NCTD-induced apoptotic cell death. Increased DNA-binding activity of AP-1 and NF-kappaB was also observed after NCTD treatment. Inhibition of NF-kappaB activation by PDTC or inhibition of AP-1 activation by curcumin drastically blocked NCTD-induced cell death. These results imply that activation of ERK and JNK, and modulation of downstream transcription factors NF-kappaB and AP-1, may be involved in NCTD-induced apoptosis.
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PMID:Norcantharidin-induced apoptosis is via the extracellular signal-regulated kinase and c-Jun-NH2-terminal kinase signaling pathways in human hepatoma HepG2 cells. 1297 86

Hepatitis B virus (HBV) X protein (HBx) has been shown to be essential for the development of hepatocellular carcinoma (HCC). Recently, we have found that HBx causes the progression of liver cancer through down-expression of PTEN, known as a tumor suppressor gene (1). The prognosis for HCC depends mainly on the clinicopathological characteristic regarding invasion and metastasis. The expression of matrix metalloproteinase (MMP)-9 has been implicated as playing an important role in HCC invasion and metastasis. We previously reported that HBV infection increased the invasiveness of hepatocytes and HCC cells through the transcriptional activation of MMP-9 (2). The HBx was shown to activate the mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase (PI-3K) signal cascade, which is essential for activation of transcription factors such as activating protein (AP)-1 and nuclear factor (NF)-kappaB. In this study, we show that the HBx protein stimulates the activities of the PI-3K-Akt/ protein kinase B (PKB) as well as extracellular signal-regulated kinase 1/2 (ERK 1/2) in HBx-transfected cells. Furthermore, we have shown that enhanced expression of MMP-9 in HBx-transfected cells mediated by not only activation of AP-1 transcriptional activity through ERKs pathway but also activation of NF-kappaB transcriptional activity through PI-3K-AKT/PKB pathway, and was associated with the invasive potential. However, treatment with U0126 (known as the ERKs inhibitor) or wortmannin (known as the PI-3K inhibitor), but not SB203580 (known as the p38 MAPK inhibitor), markedly inhibited the expression of MMP-9 induced by HBx in HBx-transfected cells. Seemingly, the invasiveness of HBx-transfected cells was decreased by treating with U0126 or wortmannin, but not SB203580. These results clearly suggest that the HBx contributed to the transcriptional regulation of MMP-9 through the ERKs and PI-3K-AKT/PKB pathway, and increased an invasive potential of cells.
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PMID:Hepatitis B viral HBx induces matrix metalloproteinase-9 gene expression through activation of ERK and PI-3K/AKT pathways: involvement of invasive potential. 1513 91

Our aim was to study the anticancer effect of the novel immunomodulator FTY720 in vitro and in vivo by investigation of cell cycle entry, cell cycle regulation, cell survival and apoptosis pathways. Three hepatoma cell lines with different p53 statuses (HepG2, Huh-7 and Hep3B) and one non-tumorigenic immortalized liver cell line (MIHA) were used for an in vitro study. The in vivo effects of FTY720 were evaluated in a nude mouse tumor model. Cell cycle distribution and cell cycle regulator proteins p27(Kip1) and cyclin D1, together with the PI3-K/Akt pathway, mitogen-activated protein kinases and cleaved caspase-3 and caspase-9, were evaluated. FTY720 selectively induced cell apoptosis in hepatoma cell lines with overexpression of cleaved caspase-3 and caspase-9, but the same phenomena were not found in MIHA cells. FTY720 induced Akt dephosphorylation at Ser473 mediated by phosphoinositide 3-kinase (PI3-K) inhibition. Dephosphorylation led to down-regulation of p42/p44 and dephosphorylation of Forkhead transcription factor and GSK-3beta and, subsequently, up-regulation of p27(Kip1) and down-regulation of cyclin D1. In our in vivo model FTY720 induced apoptosis of tumor cells by down-regulation of the Akt pathway. FTY720 suppressed tumor growth without notable side-effects in normal liver. In conclusion, FTY720 is a novel anticancer agent that induces apoptosis of hepatoma cell lines both in vitro and in vivo through PI3-K-mediated Akt dephosphorylation in a p53-independent manner.
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PMID:FTY720 induces apoptosis of human hepatoma cell lines through PI3-K-mediated Akt dephosphorylation. 1529 71

Garlic organosulfur compounds (OSCs) are recognized as a group of potential chemopreventive compounds. It is known that garlic OSCs can modulate drug metabolism systems, especially various phase II detoxifying enzymes, though the mechanism underlying their inductive effect on these enzymes remains largely unknown. In the present study, we investigated the transcriptional levels of NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase 1 (HO1) genes, the reporter activity mediated by antioxidant response element (ARE), and the protein level of transcription factor nuclear factor E2-related factor 2 (Nrf2), after administration of three major garlic OSCs--diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS)--in human hepatoma HepG2 cells. Our results showed that ARE activation and Nrf2 protein accumulation were well correlated with phase II gene expression induction. The structure-activity relationship study indicated that the third sulfur in the structure of OSCs contributed substantially to their bioactivities, and that allyl-containing OSCs were more potent than propyl-containing OSCs. To better understand the signaling events involved in the upregulation of detoxifying enzymes by DATS, ARE activity and Nrf2 protein levels were examined after transient transfection of HepG2 cells with mutant Nrf2, cotreatment with antioxidants, and pretreatment with protein kinase inhibitors. DATS-induced ARE activity was inhibited by dominant-negative Nrf2 Kelch-like ECH-associating protein 1 and constructs. Cotreatment with thiol antioxidants decreased the ARE activity and Nrf2 protein level induced by DATS. Three major mitogen-activated protein kinases (MAPKs)--extracellular signal-regulated protein kinase, c-Jun N-terminal kinase, and p38--were activated by DATS treatment. However, the inhibition of these MAPKs did not affect DATS-induced ARE activity. Pretreatment with various upstream protein kinase inhibitors showed that the protein kinase C pathway was not directly involved in DATS-induced ARE activity, but instead the calcium-dependent signaling pathway appeared to play a role in the DATS-induced cytoprotective effect.
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PMID:Induction of detoxifying enzymes by garlic organosulfur compounds through transcription factor Nrf2: effect of chemical structure and stress signals. 1547 9

Hydroxyurea is commonly used to treat hematologic disorders and some type of solid tumors, but the mechanism for its therapeutic effect is not clearly known. In this study, we examined the effect of hydroxyurea on rat hepatoma McA-RH7777 cells, specifically, on the role of mitogen-activated protein (MAP) kinase signal transduction pathways and p21(Waf1), p27(Kip1) and p53. Rat hepatoma McA-RH7777 cells treated with hydroxyurea for 7 days, caused the inhibition of cell growth in a dose-dependent manner. But, this growth inhibition was not caused by necrosis or apoptosis but instead was associated with cell senescence-like change as evidenced by senescence associated-beta-galactosidase staining, and cells arrest at G1 phase of cell cycle. Phosphorylation of MAP kinases, such as ERK, JNK, and p38, was found to be decreased after treatment of cells with hydroxyurea. But, the expression of p21(Waf1) was increased, while p27(Kip1) and p53 were not detected in hydroxyurea treated rat hepatoma cells. Hydroxyurea treatment induced G1 arrest and a senescence-like changes in rat hepatoma McA-RH7777 cells may be the likely results of signal disruption of MAP kinases (ERK, JNK, and p38 MAP kinase) and p21(Waf1) over-expression.
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PMID:Involvement of mitogen-activated protein kinases and p21Waf1 in hydroxyurea-induced G1 arrest and senescence of McA-RH7777 rat hepatoma cell line. 1555 22


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