Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The distribution of 4-nitroquinoline 1-oxide (4-NQO) reductase, assumed to be closely related to the carcinogenesis of 4-NQO, was investigated in the mucosa of canine digestive tract, and its results indicated following points. 1) The activity of 4-NQO reductase was highest in the esophagus, next in the stomach, and remarkably low in the small and large intestines. 2) There is no significant difference in the 4-NQO reductase activity between the upper, middle, and lower portion of the esophagus, but its activity was higher in the female than in the male in its upper and middle portions. 3) Among the esophageal tissue, its activity was high only in the mucous epithelium and very low in all other layers. 4) Most of the enzymic activity in the esophageal mucosa existed in the cytosol fraction and activity of the microsome fraction was remarkably low. Even if NADPH or NADH was used as the hydrogen donor, its activity was not different in the cytosol fraction, but the former was a better hydrogen donor in the microsome fraction. 5) In the gastric mucosa, the enzymic activity was equally high in various portions of the corpus ventriculi; the greater and lesser curvatures, anterior and posterior parietes, and fundus. It was remarkably low only in the pyloric antrum.
 ...
PMID:Distribution of 4-nitroquinoline 1-oxide reductase in the mucosa of canine digestive tract. 9 82

Aluminium chloride was subcutaneously administered to mice and its effect on the activities of 4-nitroquinoline 1-oxide (4-NQO) reductase and 4-hydroxyaminoquinoline 1-oxide (4-HAQO) reductase, and the organ distribution of carcinogen(s) in mouse lung and liver were examined. Subcutaneous administration of aluminium chloride in mice results in significant elevation of 4-NQO reductase and 4-HAQO reductase activities in their lung and liver, compared with those of the control. Simultaneous subcutaneous administration of aluminium chloride with 4-nitroquinoline[5, 6, 7, 8, 9, 10-14C] 1-oxide (14C-4-NQO) and examination of radioactivity distribution in the lung and liver showed that the radioactivity per tissue, 0.5 and 1 hr after the administration, decreased in the lung but inversely increased in the liver. Radioactivity in the lung and liver 2 hr after the administration was not different from that of the control. Simultaneous subcutaneous administration of 14C-4-NQO and aluminium chloride resulted in decreased distribution of 4-NQO and 4-HAQO in the lung compared with that of the control, while the distribution of their metabolites, 4-aminoquinoline 1-oxide (4-AQO) and 4-hydroxyquinoline 1-oxide (4-OHQO), inversely increased. Distribution of 4-aminoquinoline (4-AQ) and 4-hydroxyquinoline (4-OHQ) in the lung was not different from that of the control. These results suggest that the rapid metabolic changes of carcinogenic 4-NQO and 4-HAQO to noncarcinogenic substance(s) and decrease in the concentration of carcinogenic substances in the lung by the subcutaneous administration of aluminium chloride constitutes one of the factors for the mechanism of the suppression of carcinogenesis by aluminium chloride.
 ...
PMID:Effect of aluminium chloride on metabolism of 4-nitroquinoline 1-oxide. 11 94

Parenchymal hepatocytes isolated from adult rats were cultured on three types of collagen-containing substrata: collagen-coated plates, collagen membranes and confluent diploid human fibroblasts. Hepatocytes on the latter two substrata maintained characteristic morphology for at least 10 days in culture, whereas degenerative changes (cell death and formation of multinucleated hepatocytes) and growth of nonparenchymal elements were seen after 5 days in cultures on collagen-coated plates. Parallel findings were seen on basal and induced levels of cytochrome P-450 and NADPH-cytochrome C reductase. The basal levels of cytochrome P-450 were not measurable after day 3 in hepatocytes cultured on collagen-coated plates, whereas measurable levels were maintained in the hepatocytes cultured on the other two substrata. Addition of phenobarbital or methylcholanthrene at day 5 in culture caused an increase in cytochromes P-450 and P-448, respectively, only in hepatocytes cultured on collagen membranes and confluent fibroblasts. Analogous results were seen for the enzyme NADPH-cytochrome C reductase. The similarities in performance between hepatocytes on collagen membranes and on human fibroblasts show that a continuous collagen-containing substratum is important for optimal performance of hepatocytes in primary culture. The possible importance of cultures of hepatocytes on human fibroblasts for carcinogenesis studies is discussed.
 ...
PMID:Primary cultures of hepatocytes on human fibroblasts. 11 6

The previously observed alterations in the energy transducing system of rat liver mitochondria during 3'-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB) carcinogenesis were investigated using aliphatic dicarbonyl compounds as molecular probes and the effect of temperature on the membrane-linked NADH-indophenol reductase. The vicinal diketone, diacetyl, uncouples oxidative phosphorylation in normal rat liver mitochondria while the higher diketones, acetylacetone and acetonylacetone, are increasingly less effective in that order; diacetyl totally abolishes respiratory control with substrates the oxidation of which involves the NADH leads to CoQ segment, but only partially with succinate which bypasses this segment. Diacetyl, likewise, uncouples oxidative phosphorylation in liver mitochondria from rats fed 3'-Me-DAB, but the mitochondria are most resistant to this uncoupling (in terms of the P/O ratio) at the time period when the respiratory control index (determined in the absence of diacetyl) is at the dye-induced minmum. This time period is at 3 to 4 weeks of dye administration, representing the cumulative dose for tumorigenesis threshold. At this threshold period of feeding 3'-Me-DAB, discontinuities in the Arrhenius plot of the mitochondrial membrane-localized NADH-indophenol reductase appear, with a return toward the control state (no break) at 8 weeks, only to reappear in the plot of the enzyme from tumor mitochondria, suggesting sequential membrane phase transitions in the mitochondria during azo dye carcinogenesis.
 ...
PMID:Mitochondrial membrane-linked reactions in carcinogenesis: change in steroselective uncoupling of oxidative phosphorylation by aliphatic dicarbonyls and in the Arrhenius plot of NADH-indophenol reductase. 40 68

During diethylnitrosamine (DEN) administration, a distinctive difference was observed between rats and guinea-pigs in the sequence of ultrastructural changes in the hepatic endoplasmic reticulum (ER). In DEN-induced hepatic tumour cells in the guinea-pig there was extensive proliferation of the rough ER, while the smooth ER was quite sparse; in the premalignant liver the opposite was noted. This is in contrast to the rat, in which administration of either DEN or 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) brings about, in both premalignant and malignant hepatic tissue, proliferation of the smooth ER and sparsity of the rough ER. Yet, as in the rat, the number of ribosomes on the outer surface of the guinea-pig liver rough ER is greatly reduced and this is paralleled by a 49% decrease of the RNA/protein ratio as early as 4 weeks of nitrosamine administration. The decrease of RNA/protein ratio and ultrastructurally observed loss of ribosomes from the ER, following nitrosamine administration, correlate with a decrease of photometric response of microsomal suspensions to the sulphydryl probe, p-chloromercuribenzoate. While azo-dye-reductase activity is higher in untreated rats than in untreated guinea-pigs, feeding 3'-Me-DAB for 6 weeks brings about a 76% decrease in the rat, but no significant decrease in the guinea-pig, which is refractory to azo-dye carcinogenesis. Thus, the ability of the liver to inactivate the dye is greatly decreased in the rat, but not in the guinea-pig, as administration progresses toward the threshold dose for tumorigenesis. On the other hand, constitutive levels of nitrosamine dealkylase are identical in the 2 species and remain essentially unchanged following administration of DEN for 10 weeks. Inasmuch as nitrosamine dealkylation represents activating metabolism, this provides a rationale for the comparable susceptibility of the rat and guinea-pig to DEN carcinogenesis. Of the 2 enzymes in the 2 species, it is only azo-dye reductase in the guinea-pig which appears to be unregulated by glucose repression, since starvation brings about no change in this activity. Starvation-induced increase of azo-dye reductase in the rat is not influenced by administration of 3'-Me-DAB and only slightly by DEN. The starvation-induced increase of nitrosamine dealkylation is abolished, however, in both species by administration of DEN but only slightly decreased by 3'-Me-DAB.
 ...
PMID:Ultrastructural and metabolic determinants of resistance to azo-dye susceptibility to nitrosamine carcinogenesis of the guinea-pig. 41 61

Lecithin and kephalin content in the microsomes and mitochondria of the rat liver, and also the activity of enzymatic and nonenzymatic systems of the phospholipid peroxidation showed a sharp change following 3,4-benzpyrene injection. Carcinogenesis is accompanied by significant changes in the lipid peroxides content and in the activity of the enzyme utilizing lipoperoxides (glutathion peroxidase, glutathion reductase). Accumulation of lipid peroxides in the rat liver in carcinogenesis was connected with disturbed balance of the generating systems and detoxication of lipid peroxides in the tumour is attributed to the high activity of the protective enzymatic systems and serves as a reflection of the adaptation mechanisms directed to the maintenance of a high pool of proliferating cells in the tumour.
 ...
PMID:[Lipid peroxide metabolism in chemical carcinogenesis]. 42 80

Prostate cancer is a major health problem for the aging male population. Despite hormonal dependence, the inevitable emergence of androgen insensitive tumors, which have a dismal prognosis, highlights the need to develop prevention strategies such as chemoprevention. An acceptable agent must interfere with either the process of carcinogenesis or tumor growth, and have minimal toxicity. In clinical studies, 5 alpha-reductase inhibitors have been shown to suppress serum and intraprostatic levels of dihydrotestosterone, an important promoter of prostate cancer, leading to reduction in prostate size and suppression of glandular cell activity as measured by prostate specific antigen secretion. In addition, 5 alpha-reductase inhibitors have demonstrated an excellent safety profile and tolerability in 12 month controlled clinical trials. No significant metabolic effects have been observed in gonadotropin secretion, spermatogenesis, serum lipids or glucose tolerance. The efficacy and safety of 5 alpha-reductase inhibitors in studies to date, combined with the androgen dependence of tumor production, strongly supports investigating their use for chemoprevention of prostate cancer.
 ...
PMID:Chemoprevention strategies for prostate cancer: the role of 5 alpha-reductase inhibitors. 128 94

An important feature of malignant transformation is loss of the cholesterol feedback inhibition mechanism that regulates cholesterol synthesis. Cancer cells seem to require an increase in the concentrations of cholesterol and of cholesterol precursors. Therefore, a reasonable assumption is that prevention of tumour-cell growth can be achieved by restricting either cholesterol availability or cholesterol synthesis. In-vivo and cell-culture experiments have shown that lowering the plasma cholesterol concentration or intervening in the mevalonate pathway with 3-hydroxy-3-methylglutaryl (HMG) CoA reductase inhibitors decreases tumour growth. Currently prescribed doses of HMG-CoA reductase inhibitors given orally or continuously by an implantable infusion pump could achieve tumour therapeutic tissue concentrations of these agents. My hypothesis is that cholesterol inhibition can inhibit tumour cell growth, can act as an adjuvant to cancer chemotherapy, and, possibly, can prevent carcinogenesis.
 ...
PMID:Cholesterol inhibition, cancer, and chemotherapy. 135 10

Incubation of rat liver cytosolic or microsomal fractions with chromium(VI) led to a dramatic decrease in chromium(VI) mutagenicity, as determined by the Ames Salmonella assay using the TA100 tester strain. The cytosol-dependent decrease in chromium(VI) mutagenicity was found to be counteracted in the presence of dicumarol, an inhibitor of the cytosolic enzyme NAD(P)H:quinone oxidoreductase (DT-diaphorase). In order to determine whether DT-diaphorase is a significant factor in enzymatic reduction of chromium(VI) in rat liver tissue, cytosolic and microsomal fractions were analyzed for NAD(P)H-dependent chromium (VI) reductase activity leading to chromium(V) formation by using electron paramagnetic resonance (EPR) spectroscopy. Reaction of chromium(VI) with NADH or NADPH in the presence of either cytosolic or microsomal fractions led to the formation of stable chromium(V)--NAD(P)H complexes. When glucose 6-phosphate (G6P) was present in the reaction as part of a NADPH-generating system, stable chromium(V)--G6P complexes were formed in addition to the chromium(V)--NAD(P)H complexes. The chromium(V) complexes had g values of 1.980-1.982 and superhyperfine splitting constants of 0.8-0.9 characteristic of bis(diol)oxochromium(V) complexes. Inhibition of 90% of the cytosolic DT-diaphorase activity by dicumarol led to only partial (20-22%) inhibition of chromium(V) formation. Visible and EPR spectroscopic studies showed that purified DT-diaphorase had no detectable chromium(VI) reductase activity and did not catalyze formation of chromium(V). Inhibition of 69% of microsomal aryl hydrocarbon hydroxylase activity by ketoconazole led to partial (10%) inhibition of chromium(V) formation. These results indicate that intracellular NAD(P)H-dependent enzymatic reduction of chromium(VI) in rat liver cannot be attributed to the activity of any one enzyme in the cytosolic or microsomal fractions. DT-diaphorase appears to play an indirect role in decreasing chromium(VI)-induced mutagenicity in Salmonella, possibly through interaction with other redox active cellular components. The involvement of diols such as sugars and pyridine nucleotides in stabilizing intracellularly generated chromium(V) is discussed.
Carcinogenesis 1992 Jul
PMID:Reduction of chromium(VI) to chromium(V) by rat liver cytosolic and microsomal fractions: is DT-diaphorase involved? 137 26

Chromium(VI) reductase activity was measured in ultrafiltrates of rat lung after various pretreatments in vitro at 37 degrees C and pH 7.0. Pretreatment of ultrafiltrates with L-ascorbate oxidase (EC 1.10.3.3), which specifically eliminated ascorbate, blocked approximately 95% of chromium(VI) reductase activity in ultrafiltrates. Preincubation of ultrafiltrates with heat-denatured ascorbate oxidase or the sulfhydryl-blocking agent N-ethylmaleimide (NEM) had no significant effect on Cr(VI) reductase activity. In rat lung cytosols, L-ascorbate oxidase blocked approximately 95% and NEM blocked approximately 15% of Cr(VI) reductase activity. The extent of inhibition of Cr(VI) reductase activity in cytosols by L-ascorbate oxidase was significantly decreased to approximately 75% after addition of 1.0 mM NADPH. When Cr(VI) was incubated with salmon sperm nuclei suspended in rat lung cytosol for 15 min, Cr became bound to nuclear DNA. This Cr-DNA binding was completely inhibited by preincubation of rat lung cytosols with L-ascorbate oxidase and inhibited approximately 60% by preincubation with NEM. Taken together these data suggest that ascorbate and/or ascorbate-dependent factors are the principal reductants of Cr(VI) in both ultrafiltrates and cytosols prepared from rat lung and ascorbate-dependent metabolism of Cr(VI) results in Cr binding to nuclear DNA in vitro. Although sulfhydryl-containing factors and NADPH-dependent factors only make a minor contribution to Cr(VI) reduction in rat lung cytosols, sulfhydryls may be significantly involved in the binding of Cr to nuclear DNA.
Carcinogenesis 1992 Aug
PMID:Ascorbate is the principal reductant of chromium(VI) in rat lung ultrafiltrates and cytosols, and mediates chromium-DNA binding in vitro. 149 83


1 2 3 4 5 6 7 8 9 10 Next >>