Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0345904 (liver cancer)
 15,188 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biochemical characteristics of cathepsin B secreted from cultured human liver cancer cells were examined. The enzyme activity of culture medium against a synthetic substrate, N-carbobenzoxy-L-arginyl-L-arginine-4-methyl-coumaryl-7-amide, was dependent on the addition of cysteine, and the optimal pH was found to be 6.0. No activity was observed when the enzyme source was fresh medium not used for culture. These results suggest that the enzyme released from liver cancer cells is the thiol-protease cathepsin B. The molecular weight of the enzyme with 90% of the total activity was 40,000. Two cathepsin B molecules were found in liver tissue from patients with hepatocellular carcinoma (HCC); one was equivalent in size to the secreted enzyme, and a smaller one was the same as normal liver cathepsin B (27,000), which was also obtained from HCC-bearing cirrhotic liver. These results demonstrate that two molecules of cathepsin B are synthesized in liver cancer, and that the larger one is released into the surrounding tissue.
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PMID:The secretion of high molecular weight cathepsin B from cultured human liver cancers. 271 72

Twenty-two plasma free amino acid contents from 22 primary liver cancer (PLC) patients were assayed by means of HPLC and compared with those from 16 normal subjects. The results showed that in PLC patients, plasma total amino acid (TAA), branched chain amino acid (BCAA), glycogenic amino acid, glutamine, histidine and arginine were lowered, while plasma aromatic amino acid (AAA) and methionine did not decrease significantly resulting in the BCAA/AAA ratio decline. Comparing 8/22 subclinical and 14/22 clinical liver cancers with healthy controls respectively, it was found that there was a decrease of plasma TAA, glutamine, arginine, histidine, BCAA and BCAA/AAA ratio, and an increase of tyrosine, in subclinical stage of PLC. It suggests that alteration of most amino acids occur in the early stage of PLC and become more obvious in the moderate and late stages. The changes of plasma amino acid contents in PLC were different from those in chronic liver diseases. The alteration of plasma amino acid contents in subclinical stage of PLC suggests that the disturbance of amino acid metabolism be resulted from malignancy. Correction of the amino acid metabolic disturbance in PLC patients may enhance the inhibition of tumor growth and improve the host metabolism and anti-cancer effect.
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PMID:[Alteration of plasma amino acid content in primary liver cancer patients]. 283 57

In order to elucidate the response of plasma glucagon in liver cell carcinoma, a clinical study was performed in 12 patients with liver cell carcinoma in addition to 8 patients with liver cirrhosis and 8 normal subjects. Arginine infusion elicited increases in plasma insulin and glucagon in 6 patients with liver cell carcinoma as well as 8 patients with liver cirrhosis compared with the controls. However, the responses of plasma insulin and glucagon in liver cell carcinoma did not exceed those in liver cirrhosis. No glucagon secreting cell was proved in the hepatic cancer tissues from two other patients. Furthermore, no measurable glucagon was demonstrated in the tumor tissues extracted from four other patients with liver cell carcinoma. The extract of the tumors, infused into the pancreatic artery of anesthetized dogs, did not elicit any discernible changes in glucagon and insulin in the pancreatic vein. The present study demonstrates an elevated response of plasma glucagon in liver cell carcinoma. Since the morphological and biochemical studies failed to demonstrate the glucagon secreting cell or glucagon-stimulating material in the tumor tissues, the elevated plasma glucagon response might be interpreted by the increased A-cell function of the pancreas and the decreased degradation of the hormones in the liver.
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PMID:Secretion of glucagon in liver cell carcinoma. 299 19

Feeding excess orotic acid (OA) in the diet promotes the carcinogenic process in different organs including the liver. A number of metabolic and genetic disorders are associated with increased synthesis of endogenous OA and some of these disorders appear to pose an increased risk of liver cancer development. This study therefore examines whether excess OA of endogenous origin also exerts a promoting effect on hepatocarcinogenesis in the mouse and the rat. Increased endogenous synthesis of OA was achieved by (i) feeding a diet deficient in arginine (AD) and (ii) feeding excess dietary carbamylaspartate (CA), a precursor for the synthesis of OA. A single dose of diethylnitrosamine (DENA) was given i.p. to male Fischer 344 rats (200 mg/kg) or to male DBA/2 mice (90 mg/kg). One week later they were placed on either AD diet or the same diet supplemented with 1.35% arginine (AS) for a total of 4 weeks. Two-thirds partial hepatectomy (PH) was performed at the end of the second week. All animals were then transferred to a control semisynthetic basal diet for a total of 20 weeks before they were killed. The results indicated that AD diet increased the incidence of hepatic nodules in both rats (percentage area occupied by nodules was 4.7 +/- 0.4 in the AD group compared to a control value of 0.7 +/- 0.5) and mice (4/10 mice had nodules > 5 mm diameter in the AD group while none in the AS group had such large nodules). In another experiment male Fischer 344 rats similarly initiated with DENA were exposed to either basal diet or basal diet containing 2% CA for 4 weeks coupled with PH performed at the end of the second week. This regimen was followed by 20 weeks of feeding basal diet to both groups. Rats given CA developed larger hepatic foci and nodules (0.84 +/- 0.56 mm3) compared to the control group, which was fed basal diet throughout the experiment (0.07 +/- 0.03 mm3). Further, both AD diet and dietary CA, like dietary OA, induced an increase in hepatic uridine nucleotides. Taken together, these results suggest that increased levels of endogenously synthesized OA, like exogenously supplied excess OA, can induce an imbalance in hepatic nucleotide pools and can exert a promoting effect on hepatocarcinogenesis.
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PMID:Perturbations of endogenous levels of orotic acid and carcinogenesis: effect of an arginine-deficient diet and carbamyl aspartate on hepatocarcinogenesis in the rat and the mouse. 795 98

Woodchuck hepatitis virus surface antigen (WHsAg) stimulated hepatocytes in culture to produce nitric oxide (NO.), as evidenced by the accumulation of nitrite in the medium. NO. synthesis by hepatocytes was positively correlated with WHsAg concentration. WHsAg-induced NO. synthesis was inhibited by NG-monomethyl-L-arginine and anti-WHsAg antibody. To our knowledge, this is the first demonstration of an increase in NO. formation by a viral antigen. These data, when considered in the light of the known genotoxicity of NO., raise the possibility that viral hepatitis increases the risk of liver cancer by increasing the production of NO.. Long-term elevated production of NO. free radicals due to stimulation by WHsAg in chronic hepatitis may directly cause reactions with cellular DNA leading to mutagenesis, as well as the formation of hepatocarcinogenic N-nitroso compounds. This provides a new mechanism by which hepatitis B virus infection might hypothetically increase the risk of liver cancer.
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PMID:Woodchuck hepatitis virus surface antigen induces nitric oxide synthesis in hepatocytes: possible role in hepatocarcinogenesis. 800 Dec 49

The tumor suppressor p53 exerts important protective functions towards DNA-damaging agents. Its inactivation by allelic deletions or point mutations within the P53 gene as well as complex formation of wildtype p53 with cellular or viral proteins is a common and crucial event in carcinogenesis. Mutations increase the half-life of the p53 protein allowing the immunohistochemical detection and anti-p53 antibody formation. Distinct G to T point mutations in codon 249 leading to a substitution of the basic amino acid arginine by the neutral amino acid serine are responsible for the altered functionality of the mutant gene product and were originally identified in 8 of 16 Chinese and 5 of 10 African HCC patients. Both groups are frequently exposed to mycotoxin contaminations of their food. Today an average P53 gene mutation rate of 25% is assumed for high-aflatoxin B1-exposure regions. This is double the rate observed in low-aflatoxin B1-exposure countries. Although many HCC patients displaying P53 mutations also suffer from HBV infection, which itself can lead to rearrangements of P53 coding regions or induce the synthesis of viral proteins possibly interacting with p53, the specific G to T transversion within codon 249 of the P53 gene seems to directly reflect the extent of aflatoxin B1 exposure.
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PMID:Point mutations of the P53 gene, human hepatocellular carcinoma and aflatoxins. 830 Oct 66

Furin is a mammalian propeptide-processing endoprotease in nonendocrine cells and has been demonstrated to be present in virtually all nonendocrine cells, including fibroblasts, epithelial cells, and hepatocytes. Furin cleaves the concensus processing site -Arg-4-X-3-Lys/Arg-2-Arg-1 decreases X+1-. Some subunit-containing precursor proteins, including an insulin receptor precursor, possess an additional basic residue at position -3, thus forming a tetrabasic processing site. This implies that a tetrabasic processing site must be easily cleavable in nonendocrine cells. We created a mutant proinsulin DNA with a peptide structure comprised of B- and A-chains linked to the C-peptide by a pair of tetrabasic residues, in the following order: B-chain-Arg-Arg-Lys-Arg-C peptide-Arg-Arg-Lys-Arg-A-chain. The native proinsulin structure was B-chain-Arg-Arg-C-peptide-Lys-Arg-A-chain. Both the native and mutant proinsulins were expressed in the following four cell lines: a monkey kidney-derived cell line (COS-7), a Chinese hamster ovary-derived cell line (CHO), a human liver cancer-derived cell line (HepG2), and a mouse fibroblast-like cell line (NIH3T3). We used these cell lines because they contain different quantities of furin mRNA, ranking as follows: NIH3T3 > HepG2 > COS > CHO. When mutant insulin was expressed in these cells, the conversion of proinsulin to mature insulin was approximately 85% in NIH3T3, 70% in HepG2, 60% in COS, and 50% in CHO. The conversion correlated well with the furin expression in each cell line as measured by the density of its Northern blot band. Moreover, in CHO, the cell line with the lowest furin expression, coexpression of mutant proinsulin with furin resulted in complete conversion of proinsulin to mature insulin.
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PMID:Processing of mutated proinsulin with tetrabasic cleavage sites to mature insulin reflects the expression of furin in nonendocrine cell lines. 834 3

We have developed a useful strategy for identifying amino acid spin systems and side-chain carbon resonance assignments in small 15N-, 13C-enriched proteins. Multidimensional constant-time pulsed field gradient (PFG) HCC(CO)NH-TOCSY experiments provide side-chain resonance frequency information and establish connectivities between sequential amino acid spin systems. In PFG HCC(CO)NH-TOCSY experiments recorded with a properly tuned constant-time period for frequency labeling of aliphatic 13C resonances, phases of cross peaks provide information that is useful for identifying spin system types. When combined with 13C chemical shift information, these patterns allow identification of the following spin system types: Gly, Ala, Thr, Val, Leu, Ile, Lys, Arg, Pro, long-type (i.e., Gln, Glu and Met), Ser, and AMX-type (i.e., Asp, Asn, Cys, His, Phe, Trp and Tyr).
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PMID:Classification of amino acid spin systems using PFG HCC(CO)NH-TOCSY with constant-time aliphatic 13C frequency labeling. 858 9

Cyanobacteria (blue-green algae) produce toxins that may present a hazard for drinking water safety. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer, to neurotoxicity. The occurrence of cyanobacteria and their toxins in water bodies used for the production of drinking water poses a technical challenge for water utility managers. With respect to their removal in water treatment procedures, of the more than 60 microcystin congeners, microcystin-LR (L, L-leucine; R, L-arginine) is the best studied cyanobacterial toxin, whereas information for the other toxins is largely lacking. In response to the growing concern about nonlethal acute and chronic effects of microcystins, the World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 microg/L drinking water. This will lead to further efforts by water suppliers to develop effective treatment procedures to remove these toxins. Of the water treatment procedures discussed in this review, chlorination, possibly micro-/ultrafiltration, but especially ozonation are the most effective in destroying cyanobacteria and in removing microcystins. However, these treatments may not be sufficient during bloom situations or when a high organic load is present, and toxin levels should therefore be monitored during the water treatment process. In order to perform an adequate human risk assessment of microcystin exposure via drinking water, the issue of water treatment byproducts will have to be addressed in the future.
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PMID:Cyanobacterial toxins: removal during drinking water treatment, and human risk assessment. 1069 27

Chronic hepatitis C virus (HCV) infection is the most frequent cause of progressive liver disease and liver cancer in the West. The p53 tumor suppressor gene is known to play an important role in carcinogenesis of different tissues being involved in gene transcription, DNA synthesis and repair and somatic mutations of p53 are common in primary liver cancer. The p53 gene displays a common genetic Arg/Pro polymorphism at codon 72 with functional significance, that has been investigated as risk factor in several cancer models. We analyzed p53 codon 72 polymorphism in a group of 340 HCV-infected subjects at different stages of disease, including 84 hepatocellular carcinoma patients. No association between codon 72 genotypes and disease severity or liver cancer was observed.
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PMID:Codon 72 polymorphism of P53 gene does not affect the risk of cirrhosis and hepatocarcinoma in HCV-infected patients. 1510 48


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