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)

In human diploid cell strains, the substitution of galactose for glucose as the sole hexose in the medium had no measurable effect on the specific activity of the cell protein for any of the three enzymes of the Leloir pathway. These enzymes are galactokinase, alpha-D-galactose-1-phosphate: UDP glucose uridyl transferase and UDP galactose 4-epimerase. A cell strain from a patient with galactosemia had no detectable activity for the transferase. The substitution of galactose for glucose in the medium of these cells (which has been shown to cause the cells to accumulate galactose-1-phosphate) also failed to affect cellular activity for the three enzymes. Similarly, the three activities failed to respond to the substitution of galactose for glucose in cultures of a rat hepatoma line. Cells of this line have been shown by others to perform a number of the tissue-specific functions of liver. The failure of galactose to stimulate increasd cellular activity for the three enzymes represents a striking difference between the behavior of these enzymes in human diploid cell strains and their behavior in E. coli.
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PMID:Studies on the regulation of the three enzymes of the Leloir pathway in cultured mammalian cells. I. Effect of substitution of galactose for glucose as the sole hexose in the medium in human diploid cell strains and in a rat hepatoma line. 17 Feb 94

The metabolism of 2-deoxy-2-fluoro-D-galactose (dGalF) was studied in rodents using HPLC, enzymatic methods, and 19F-NMR spectroscopy in vivo and in vitro. The liver took up the major part of the administered dose of the 14C-labeled D-galactose analog. This was confirmed in vivo by use of the 18F-labeled sugar (1.5 mCi/kg; 25 mumol/kg) and examination by positron emission tomography. After a dose of 1 mmol/kg, dGalF-1-phosphate accumulated rapidly (5.3 +/- 0.4 mmol/kg after 30 min), followed by formation of UDP-dGalF and UDP-2-deoxy-2-fluoro-D-glucose (0.7 +/- 0.1 and 1.8 +/- 0.1 mmol/kg, respectively, after 5 hr). Good quantitative agreement was obtained between the measurements by HPLC and enzymatic analyses and by 19F-NMR. The noninvasive in vivo 19F-NMR technique is particularly advantageous, since it allows the simultaneous analysis of all dGalF metabolites. The diversion of uridylate, due to the accumulation of UDP-2-deoxy-2-fluoro-D-hexoses, was associated with a rapid depletion of hepatic UTP, UDP-glucose, and UDP-galactose. The UTP content was decreased to 11 +/- 6% of normal within 15 min after administration of dGalF at a dose of 1 mmol/kg. The UTP-depleting action was minimal, however, at a dose of 25 mumol/kg or less, indicating that interference in uridylate metabolism will be negligible at the doses required for positron emission tomography of the liver using the 18F-labeled compound. At higher doses the UTP deficiency induced by dGalF may be useful in the chemotherapy of D-galactose-metabolizing tumors such as hepatocellular carcinoma. At moderate doses of dGalF, 19F-NMR spectroscopy in vivo or in vitro could be used to pinpoint defects of the enzymes that cause galactosemia, i.e. of galactokinase, uridyltransferase, or 4-epimerase.
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PMID:In vivo metabolism and UTP-depleting action of 2-deoxy-2-fluoro-D-galactose. 240 33

Studies on Morris hepatomas demonstrate that the specific activity of the enzymes of the Leloir pathway are subject to a variation in tumor tissue. The key enzyme of the galactose pathway, uridine diphosphogalactose 4'-epimerase, is elevated 5- to 9-fold in the rapidly growing and poorly differentiated Tumors 3924A and 7777; in line 9618A2, an even 28-fold increase was found. The observed correlation between enzyme activity, growth rate, and degree of differentiation of the hepatoma suggests that the differences are not coincidental variations. Conversely, the activity of uridine diphosphoglucose: galactose-1-phosphate uridyltransferase was diminished by 40 to 70% as compared to host liver, and the level of galactokinase showed only minor changes. The uptake of galactose and galactosamine by the hepatoma is heavily impaired, whereas the transport of other hexoses and amino sugars (2-deoxyglucose, L-fucose, N-acetylglucosamine, N-acetylmannosamine) is hardly affected. It appears that part of the carrier-mediated diffusion for hexoses is altered without a decisive impact on the whole system. Moreover, autoradiographic analysis of [14C]galactose-labeled tumor plasma membranes revealed a shift of the incorporation pattern from high- to lower-molecular-weight galactopolypeptides. Our results indicate that specific alterations of the D-galactose metabolism are a characteristic feature of Morris hepatomas.
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PMID:Alterations of D-galactose metabolism in Morris hepatomas. 676 57

d-Galactosone (d-lyxo-2-hexosulose) is phosphorylated and metabolized to the uridine diphosphate derivative in AS-30D hepatoma cells and rat liver. These reactions were catalysed in vitro by galactokinase and hexose-1-phosphate uridylyltransferase. Nucleotide analyses by high-performance liquid chromatography and enzymic assays revealed that this galactose analogue interferes with cellular pyrimidine nucleotide metabolism leading to a deficiency of UTP. [(14)C]Uridine labelling of hepatoma cells indicated a division of [(14)C]uridylate from UTP into UDP-galactosone; the latter was formed at a rate of more than 1.7mmolxh(-1)x(kg AS-30D or liver wet wt.)(-1). As a consequence of UTP deficiency, d-galactosone (1mmol/1 or 1mmol/kg body wt.) strongly enhanced the rate of pyrimidine synthesis de novo as evidenced by incorporation of (14)CO(2) into uridylate and by an expansion of the uridylate pool. This resulted in a doubling of the total acid-soluble uridylate pool within 70min in the hepatoma cells and within 110min in rat liver. Combined treatment of hepatoma cells with d-galactosone and N-(phosphonoacetyl)-l-aspartate, an inhibitor of aspartate carbamoyltransferase, prevented the expansion of the uridylate pool and led to a synergistic reduction of UTP to 10% of the content in control cells. Hepatic UTP deficiency was selective with respect to other nucleotide 5'-triphosphates but was associated with reduced contents of UDP-glucose, UDP-glucuronate, and UDP-N-acetylhexosamines. Isolation of the UDP derivative of d-galactosone revealed an extremely alkali-labile UDP-sugar, probably an isomerization product of UDP-galactosone, that was degraded by elimination of UDP with a half-life of 45min at pH7.5 and 37 degrees C. The instability of UDP-galactosone may contribute in vivo to limit the time period of severe uridine phosphate deficiency in addition to the compensatory role of pyrimidine synthesis de novo. During the initial time period, however, d-galactosone is effective as a powerful uridylate-trapping sugar analogue.
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PMID:Uridylate trapping, induction of UTP deficiency, and stimulation of pyrimidine synthesis de novo by D-galactosone. 712 88

The numerous changes in metabolic pathways that accompany liver development entail associated changes in gene expression. Egr-1 is a zinc-finger transcription factor that regulates genes involved in cellular growth, differentiation, stress response, and apoptosis in many cell types. Egr-1 is induced in liver regeneration in rodents, but its role in normal hepatocyte function has not been characterized. We examined the developmental expression of Egr-1 in mouse liver and found that its expression increased during the suckling period. In screening the sequences of the genes involved in lactose assimilation, we found that the galactokinase gene Glk contains four potential Egr-1 binding sites in its proximal promoter. A minimal promoter of 155 nucleotides encompassing the four Egr-1 sites exhibited activity in hepatoma cell lines by transient transfection assays. Moreover, co-transfection of an Egr-1 expression plasmid increased promoter activity. Finally, mutations introduced into three of the four Egr-1 binding sites decreased activity, whereas mutation of the remaining site increased promoter activity. These data tie Egr-1 and galactokinase together in a developmentally regulated chain to prepare the neonate for suckling.
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PMID:Developmental regulation of galactokinase in suckling mouse liver by the Egr-1 transcription factor. 1497 78

Hepatocellular carcinoma (HCC) is one of the most lethal types of cancer worldwide, with poor prognosis and limited treatments. In order to identify novel therapeutic targets that will lead to development of effective therapies with manageable side effects, we tested the hypothesis that knocking-down galactokinase (GALK1) or galactose-1 phosphate uridylyltransferase (GALT) gene expression would control the growth of cultured hepatoma cells. Our results showed small interfering RNA (siRNA) against GALK1 or GALT inhibited the growth of HepG2 cells in culture. Western blot analysis revealed simultaneous down-regulation of multiple players of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) growth signaling pathway, as well as heat-shock protein 90 (HSP90) and poly ADP ribose polymerase (PARP). Reverse transcription-polymerase chain reaction (RT-PCR) data, however, showed no significant mRNA reduction of the encoded genes. Our study thus not only supports GALK1 and GALT as being possible novel targets for treating HCC, but also uncovers new post-transcriptional regulatory mechanisms that link the galactose metabolic pathway to protein expression of the PI3K/AKT pathway in hepatoma.
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PMID:The Leloir Pathway of Galactose Metabolism - A Novel Therapeutic Target for Hepatocellular Carcinoma. 2791 45

Human primary hepatocytes are able to survive in a medium without glucose and arginine that is instead supplemented with galactose and ornithine (hepatocyte selection medium; HSM). This is because the cells produce glucose and arginine by the action of galactokinase (GALK) and ornithine carbamoyltransferase (OTC), respectively. It was expected that hepatocellular carcinoma (HCC) cells do not survive in HSM. In the current study, HCC cell lines (namely HLE, HLF, PLC/PRL/5, Hep3B and HepG2) and human umbilical vascular endothelial cells (HUVECs) were cultured in HSM, and the expression levels of GALK1, GALK2 and OTC were analyzed by reverse transcription-quantitative polymerase chain reaction. HLE, HLF and PLC/PRL/5 cells died on day 11, while Hep3B, HepG2 and HUVECs died on day 7. HLF cells were further analyzed as these cells had lower expression levels of GALK1, GALK2 and OTC compared with adult liver cells, and survived until day 11. In these cells, the expression levels of GALK1, GALK2 and OTC did not change on days 3 and 7 as compared to day 0. In addition, a co-culture of HLF cells with HUVECs was established and the medium was changed to HSM. It was observed that HLF cells and HUVECs in co-culture were damaged in HSM. In summary, HCC cells and HUVECs died in a medium without glucose and arginine that was supplemented with galactose and ornithine. HCC cells and HUVECs were damaged in HSM, suggesting a potential application for treatment with the medium.
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PMID:Cell death in a co-culture of hepatocellular carcinoma cells and human umbilical vascular endothelial cells in a medium lacking glucose and arginine. 2812 51