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)

The mechanism by which injected methotrexate increases thymidylate synthetase activity in the Novikoff hepatoma has been studied. Folic acid injection causes a similar increase in enzyme activity in hepatoma after 16 hr but the action of folic acid and methotrexate is not additive. The increase in activity of thymidine 5'-phosphate synthetase in the hepatoma caused by methotrexate is not affected by actinomycin D, but is inhibited 50% by puromycin and 100% by cycloheximide. High-speed supernatent fraction prepared from hepatoma of animals treated with methotrexate has, initially, one-half the specific thymidine 5'-phosphate synthetase activity of untreated controls. Upon addition of increasing amounts of tetrahydrofolate, the specific enzyme activity in the supernatant fraction from the methotrexate-treated animals rises to double that of the controls. Puromycin added to homogenates of Novikoff hepatoma consistently increases enzyme activity by approximately 20%. One hypothesis consistent with these results and results reported by others is presented.
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PMID:Thymidylate synthetase activity in the Novikoff hepatoma. 18 25

The behavior of methylenetetrahydrofolate polyglutamate conjugates in cultured mouse hepatoma cells which were starved of folate has been investigated. Folate deprivation caused methylenetetrahydrofolate levels to decrease an order of magnitude. This diminished pool consisted essentially completely of the octaglutamate form. Replenishment of the media with folate caused a slow recovery to normal levels of methylenetetrahydrofolate with undetectable quantities of shorter chain length polyglutamates observable during recovery. Leucovorin, on the other hand, caused a much more rapid recovery to normal levels and gave rise to the early appearance of short chain length polyglutamate intermediates.
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PMID:Response of mouse hepatoma cell methylenetetrahydrofolate polyglutamates to folate deprivation. 660 Sep 35

gamma-Glutamyl hydrolase is a ubiquitous enzyme that has the capacity to cleave gamma-glutamyl bonds of cellular folyl- and antifolylpoly-gamma-glutamates. This study has revealed that the enzyme is secreted by primary cultures of rat hepatocytes and by H35 hepatoma cells. It was found that more than 99% of the total enzyme from H35 cells accumulated in the medium after 48 hr incubation with the serum-free medium. The cells were shown to remain intact during the secretion period since lactate dehydrogenase, dihydrofolate reductase and lysosomal hydrolases other than gamma-glutamyl hydrolase were retained within the cell. When PteGlu5 (folylGlu4) is used as a substrate the initial product is PteGlu (folate), and there is no appearance of intermediate chain length pteroyl polyglutamates. Therefore, the secreted and cellular gamma-glutamyl hydrolase from hepatoma cells appears to be an endopeptidase. Polyclonal antibodies to the poly-gamma-glutamate substrates of the enzyme were prepared and characterized. The antibodies recognize the structural differences between alpha- and gamma-glutamyl linkages but appear equally active with PteGlu5 and its analogs such as 4-NH2-10-CH3PteGlu5 and pABAGlu5. The affinity of the antibodies is related to the gamma-glutamyl structure since L-glutamic acid, folate or p-aminobenzoic acid are inactive with the antibodies. Furthermore, poly-gamma-glutamate has lower affinity for the antibodies than the poly-gamma-glutamate derivatives of PteGlu, 4-NH2-10-CH3PteGlu or pABA.
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PMID:The properties and function of gamma-glutamyl hydrolase and poly-gamma-glutamate. 768 89

Fluoroglutamate-containing analogs of folates and methotrexate (MTX) with altered capacities for poly (gamma-glutamate) metabolism were synthesized to probe the biological roles of polyglutamates. Compared to folic acid, DL-e,t-gamma-fluorofolic acid, a compound that is a poor substrate for polyglutamylation, was approximately 25-fold less potent in promoting growth of folate-depleted H35 rat hepatoma cells. DL-beta,beta-Difluorofolic acid, a compound that forms diglutamates more readily than does folic acid, was at least equivalent to folic acid in potency. Leucovorin (LV), a reduced folate, was 30-fold more potent than folic acid in promoting growth, whereas the analogous form of DL-e,t-gamma-fluorofolate, DL-e,t-gamma-fluoroleucovorin (DL-e,t-gamma-FLV) was only 4-fold more potent than folic acid. Both LV and DL-e,t-gamma-FLV protected or "rescued" cells from the growth inhibitory effects of MTX; however a 37- to 46-fold higher concentration of the fluoro analog was required. Folic acid, DL-e,t-gamma-fluorofolic acid, LV, and DL-e,t-gamma-FLV each potentiated the growth inhibitory effect of 5-fluoro-2'-deoxyuridine on CCRF-CEM human leukemia cells; higher concentrations of fluorinated analogs again were required. Stereochemically pure L-t-gamma-fluoromethotrexate (L-t-gamma-FMTX), a poor substrate for polyglutamylation, was evaluated as a cell growth inhibitor. In continuous exposure, L-t-gamma-FMTX), was 7-fold less potent than MTX as an inhibitor of CCRF-CEM growth. Results with these fluorinated folate and MTX analogs offer insight into the importance of polyglutamate metabolism to these biological and pharmacological effects.
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PMID:Biological properties of fluoroglutamate-containing analogs of folates and methotrexate with altered capacities to form poly (gamma-glutamate) metabolites. 893 38

Folate coenzymes are critical for de novo synthesis of purine and thymidine, and for interconversion of amino acids. Folate deficiency inhibits cellular proliferation, disturbs cell cycling, causes genetic damage and eventually results in cell death. Previously, we demonstrated that the demise of human hepatoma Hep G2 cells mediated by folate deficiency proceeded via a p53-independent apoptosis, and the perturbation of intracellular calcium homeostasis was also shown to be involved. To further delineate the mechanism associated with this observed phenomenon, Hep G2 cells were cultivated in the control or folate-deficient media (control media lacking folate, glycine, thymidine and hypoxanthine) for 4 weeks. At the end of this cultivation period, we found that TBARS (an index of lipid peroxidation) concentrations in the folate-deficient cells were drastically increased as compared to the control cells (0.04 vs 0.01 nmole/10(6) cells), indicating that a severe oxidative stress of the former cells had occurred. This phenomenon was also shown to coincide with the ability of these folate-deficient cells to elaborate increased amounts of H2O2 as compared to its folate-supplemented cells (2.87 vs 0.98 nmole/10(5) cells/h). Furthermore, the accelerated production of H2O2 by the folate-deficient cells was also closely correlated with the elevated homocysteine concentrations released in the culture medium (15.37 +/- 2.4 vs 3.58 +/- 2.4 micromole/L; P< 0.001). Finally, we demonstrated that folate deficiency was indeed capable of activating a redox-sensitive transcription factor, NF-kappaB, which is crucial in the control of a reactive oxygen species-mediated apoptosis. In summary, we show that folate deficiency-induced apoptosis is proceeded via the enhanced activation of NF-kappaB, which is the resulting form of the homocysteine-mediated overproduction of hydrogen peroxide.
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PMID:Folate deficiency-induced oxidative stress and apoptosis are mediated via homocysteine-dependent overproduction of hydrogen peroxide and enhanced activation of NF-kappaB in human Hep G2 cells. 1168 76

We reported earlier that expression of Sox-4 was found to be elevated during prostaglandin (PG) A(2) and delta(12)-PGJ(2) induced apoptosis in human hepatocarcinoma Hep3B cells. In this study, the role of Sox-4 was examined using human Hep3B and HepG2 cell lines. Sox-4 induction by several apoptotic inducer such as A23187 (Ca(2+) ionophore) and etoposide (topoisomerase II inhibitor) and Sox-4 transfection into the cells were able to induce apoptosis as observed by the cellular DNA fragmentation. Antisense oligonucleotide of Sox-4 inhibited the induction of Sox-4 expression and blocked the formation of DNA fragmentation by PGA(2) and delta(12)-PGJ(2) in Hep3B and HepG2 cells. Sox-4-induced apoptosis was accompanied with caspase-1 activation indicating that caspase cascade was involved in this apoptotic pathway. These results indicate that Sox-4 is involved in Hep3B and HepG2 cells apoptosis as an important apoptotic mediator.
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PMID:Sox-4 is a positive regulator of Hep3B and HepG2 cells' apoptosis induced by prostaglandin (PG)A(2) and delta(12)-PGJ(2). 1221 17

Multilayer nanofilms, formed by the layer-by-layer (LbL) adsorption of positively and negatively charged polyelectrolytes, are promising substrates for tissue engineering. We investigate here the attachment and function of hepatic cells on multilayer films in terms of film composition, terminal layer, rigidity, charge, and presence of biofunctional species. Human hepatocellular carcinoma (HepG2) cells, adult rat hepatocytes (ARH), and human fetal hepatoblasts (HFHb) are studied on films composed of the polysaccharides chitosan (CHI) and alginate (ALG), the polypeptides poly(l-lysine) (PLL) and poly(l-glutamic acid) (PGA), and the synthetic polymers poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS). The influence of chemical cross-linking following LbL assembly is also investigated. We find HepG2 to reach confluence after 7 days of culture on only 2 of 18 candidate multilayer systems: (PAH-PSS)(n) (i.e. nPAH-PSS bilayers) and cross-linked (PLL-ALG)(n)-PLL. Cross-linked PLL-ALG and PLL-PGA films support attachment and function of ARH, independently of the terminal layer, provided collagen is adsorbed to the top of the film. (PAH-PSS)(n), cross-linked (PLL-ALG)(n), and cross-linked (PLL-PGA)(n)-PLL films all support attachment, layer confluence, and function of HFHb, with the latter film promoting the greatest level of function at 8 days. Overall, film composition, terminal layer, and rigidity are key variables in promoting attachment and function of hepatic cells, while film charge and biofunctionality are somewhat less important. These studies reveal optimal candidate multilayer biomaterials for human liver tissue engineering applications.
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PMID:Multilayer nanofilms as substrates for hepatocellular applications. 1865 30

Delivering intact small interfering RNA (siRNA) into the cytoplasm of targeted cells in vivo is considered a major obstacle in the development of clinically applicable RNA interference-based therapies. Although dextran hydroxyethyl methacrylate (dex-HEMA) nanogels have been reported to be suitable carriers for siRNA delivery in vitro, and are ideally sized (approximately 180 nm) for intravenous delivery to tumors, they likely possess insufficient blood circulation times to enable an adequate extravasation and accumulation in the tumor tissue. PEGylation of these nanogels should not only improve their circulation time but also minimize their aggregation upon intravenous injection. For this reason, a new type of nanogels and three different methods of PEGylating dextran nanogels were evaluated. Covalent PEGylation of the siRNA-loaded nanogels using N-hydroxysuccinimidyl polyethylene glycol (NHS-PEG) was shown to be superior to the addition of both polyethylene glycol (PEG) and PEG grafted poly-l-glutamic acid (PGA-PEG). Flow cytometry and confocal microscopy revealed that PEGylated nanogels are still taken up efficiently by HuH-7 human hepatoma cells and A431 human epithelial carcinoma cells and that the process is cell type dependent. Moreover, PEGylated nanogels loaded with siRNA cause significant EGFP knockdown in a human hepatoma cell line (HuH-7_EGFP) and are non-toxic for these cells.
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PMID:PEGylation of biodegradable dextran nanogels for siRNA delivery. 2043 39

Glycine N-methyltransferase (GNMT) is a major hepatic enzyme that converts S-adenosylmethionine to S-adenosylhomocysteine while generating sarcosine from glycine, hence it can regulate mediating methyl group availability in mammalian cells. GNMT is also a major hepatic folate binding protein that binds to, and, subsequently, may be inhibited by 5-methyltetrafolate. GNMT is commonly diminished in human hepatoma; yet its role in cellular folate metabolism, in tumorigenesis and antifolate therapies, is not understood completely. In the present study, we investigated the impacts of GNMT expression on cell growth, folate status, methylfolate-dependent reactions and antifolate cytotoxicity. GNMT-diminished hepatoma cell lines transfected with GNMT were cultured under folate abundance or restriction. Folate-dependent homocysteine remethylation fluxes were investigated using stable isotopic tracers and gas chromatography/mass spectrometry. Folate status was compared between wild-type (WT), GNMT transgenic (GNMT(tg)) and GNMT knockout (GNMT(ko)) mice. In the cell model, GNMT expression increased folate concentration, induced folate-dependent homocysteine remethylation, and reduced antifolate methotrexate cytotoxicity. In the mouse models, GNMT(tg) had increased hepatic folate significantly, whereas GNMT(ko) had reduced folate. Liver folate levels correlated well with GNMT expressions (r = 0.53, P = 0.002); and methionine synthase expression was reduced significantly in GNMT(ko), demonstrating impaired methylfolate-dependent metabolism by GNMT deletion. In conclusion, we demonstrated novel findings that restoring GNMT assists methylfolate-dependent reactions and ameliorates the consequences of folate depletion. GNMT expression in vivo improves folate retention and bioavailability in the liver. Studies on how GNMT expression impacts the distribution of different folate cofactors and the regulation of specific folate dependent reactions are underway.
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PMID:GNMT expression increases hepatic folate contents and folate-dependent methionine synthase-mediated homocysteine remethylation. 2121 71

A new type of drug delivery system (DDS) involved chitosan (CHI) modified single walled carbon nanotubes (SWNTs) for controllable loading/release of anti-cancer doxorubicin (DOX) was constructed. CHI was non-covalently wrapped around SWNTs, imparting water-solubility and biocompatibility to the nanotubes. Folic acid (FA) was also bounded to the outer CHI layer to realize selective killing of tumor cells. The targeting DDS could effectively kill the HCC SMMC-7721 cell lines and depress the growth of liver cancer in nude mice, showing superior pharmaceutical efficiency to free DOX. The results of the blood routine and serum biochemical parameters, combined with the histological examinations of vital organs, demonstrating that the targeting DDS had negligible in vivo toxicity. Thus, this DDS is promising for high treatment efficacy and low side effects for future cancer therapy.
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PMID:Targeted therapy of SMMC-7721 liver cancer in vitro and in vivo with carbon nanotubes based drug delivery system. 2197 23


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