Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Black tea extracts (hot aqueous, polyphenols and theaflavins) and green tea extracts (hot aqueous, polyphenols, epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate) were tested in nine standardized cell culture assays for comparative cancer chemopreventive properties. Most black and green tea extracts strongly inhibited neoplastic transformation in mouse mammary organ cultures, rat tracheal epithelial cells and human lung tumor epithelial cells. Nearly all tea fractions strongly inhibited benzo[a]pyrene adduct formation with human DNA. Induction of phase II enzymes, glutathione-S-transferase and quinone reductase, were enhanced by nearly all tea fractions, while glutathione was induced by only a few fractions. Ornithine decarboxylase activity was inhibited by nearly all the green tea fractions, but none of the black tea fractions. 12-O-tetradecanoylphorbol-13-acetate-induced free radicals were inhibited by most tea fractions. These results provide strong evidence of both anti-mutagenic, anti-proliferative and anti-neoplastic activities for both black and green tea extracts. Such anticancer mechanisms may well be responsible for the cancer preventive efficacies seen in both experimental and human studies.
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PMID:Comparative chemopreventive mechanisms of green tea, black tea and selected polyphenol extracts measured by in vitro bioassays. 1060 35

A replication-selective herpes simplex virus type 1 ICP34.5 mutant (HSV-1716) has shown efficacy both in vitro and in vivo against human non-small cell lung cancer (NSCLC) cell lines but complete eradication of tumor has not been accomplished with a single viral treatment in our murine xenograft models. Therefore, strategies to enhance the efficacy of this treatment were investigated. We determined the oncolytic activity of HSV-1716 in NCI-H460 cells in combination with each of four chemotherapeutic agents: mitomycin C (MMC), cis-platinum II (cis-DDP), methotrexate (MTX), or doxorubicin (ADR). Isobologram analysis was performed to evaluate the interaction between the viral and chemotherapeutic agents. The oncolytic effect of HSV-1716 in combination with MMC was synergistic in two of five NSCLC cell lines. In the other three cell lines, the combined effect appeared additive. No antagonism was observed. The in vivo effect of this combination was then examined in a murine xenograft model. NCI-H460 flank tumors were directly injected with HSV-1716 (4 x 106 PFU) followed by intravenous MMC administration (0.17 mg/kg) 24 hr later. After 3 weeks, the mean tumor weight in the combined treatment group was significantly less than either individual treatment in an additive manner. The synergistic dose of MMC neither augmented nor inhibited viral replication in vitro and HSV-1716 infection did not upregulate DT-diaphorase, which is the primary enzyme responsible for MMC activation. In summary, the combination of HSV-1716 with common chemotherapeutic agents may augment the effect of HSV-based therapy in the treatment of NSCLC.
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PMID:Combined therapy with chemotherapeutic agents and herpes simplex virus type 1 ICP34.5 mutant (HSV-1716) in human non-small cell lung cancer. 1060 61

In tumor cell lines with high content of DT-diaphorase (EC 1.6.99.2), the cytotoxicity of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB-1954) and its derivatives is exerted through DT-diaphorase-catalyzed formation of crosslinking species. However, little is known about other possible mechanisms of CB-1954 action. We have examined the toxicity of CB-1954 and its derivatives to bovine leukemia virus-transformed lamb fibroblasts (line FLK), which possessed moderate DT-diaphorase activity, 260 units/mg protein. The action of these compounds was accompanied by lipid peroxidation, their toxicity was decreased by desferrioxamine and antioxidant N,N'-diphenyl-p-phenylene diamine (DPPD), but, in most cases, not by dicumarol, an inhibitor of DT-diaphorase. Using multiparameter regression analysis, we have found that the toxicity of CB-1954 derivatives as well as that of several non-alkylating nitroaromatics, increased upon the increase in their single-electron reduction potential (E(1)7) and octanol/water partition coefficient (P), and almost did not depend on their reactivity towards DT-diaphorase. It seems that in cell lines with a moderate amount of DT-diaphorase, the toxicity of CB- 1954 and its analogs is exerted through their redox cycling.
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PMID:Role of redox cycling and activation by DT-diaphorase in the cytotoxicity of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB-1954) and its analogs. 1065 29

The merits of N-unsubstituted indoles and cyclopent[b]indoles as DNA-directed reductive alkylating agents are described. These systems represent a departure from N-substituted and pyrrolo[1, 2-a]-fused systems such as the mitomycins and mitosenes. The cyclopent[b]indole-based aziridinylquinone system, when bearing an acetate leaving group with or without an N-acetyl group, was cytotoxic and displayed significant in vivo activity against syngeneic tumor implants. These analogues were superior to the others studied in terms of both high specificity for the activating enzyme DT-diaphorase and high percent DNA alkylation. Alkylation by a quinone methide intermediate as well as by the aziridinyl group could lead to cross-linking. The possible metabolites of the most active indole species were prepared and found to retain cytotoxicity, suggesting that in vivo activity could be sustained. The indole systems in the present study display selectivity for melanoma and, depending on the substituents present, selectivity for non-small-cell lung, colon, renal, and prostate cancers. The cancer specificities observed are believed to pertain to differential substrate specificities for DT-diaphorase.
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PMID:Design of cancer-specific antitumor agents based on aziridinylcyclopent[b]indoloquinones. 1066 73

beta-Lapachone activates a novel apoptotic response in a number of cell lines. We demonstrate that the enzyme NAD(P)H:quinone oxidoreductase (NQO1) substantially enhances the toxicity of beta-lapachone. NQO1 expression directly correlated with sensitivity to a 4-h pulse of beta-lapachone in a panel of breast cancer cell lines, and the NQO1 inhibitor, dicoumarol, significantly protected NQO1-expressing cells from all aspects of beta-lapachone toxicity. Stable transfection of the NQO1-deficient cell line, MDA-MB-468, with an NQO1 expression plasmid increased apoptotic responses and lethality after beta-lapachone exposure. Dicoumarol blocked both the apoptotic responses and lethality. Biochemical studies suggest that reduction of beta-lapachone by NQO1 leads to a futile cycling between the quinone and hydroquinone forms, with a concomitant loss of reduced NAD(P)H. In addition, the activation of a cysteine protease, which has characteristics consistent with the neutral calcium-dependent protease, calpain, is observed after beta-lapachone treatment. This is the first definitive elucidation of an intracellular target for beta-lapachone in tumor cells. NQO1 could be exploited for gene therapy, radiotherapy, and/or chemopreventive interventions, since the enzyme is elevated in a number of tumor types (i.e. breast and lung) and during neoplastic transformation.
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PMID:NAD(P)H:Quinone oxidoreductase activity is the principal determinant of beta-lapachone cytotoxicity. 1068 17

We have analyzed the tumor biopsies of 45 patients with bladder cancer for p53 mutations by direct sequencing. In addition to N-acetyltransferase-2 (NAT2) and GSTM1 allelisms, which were examined previously, we have analyzed the genetic polymorphisms of GSTT1, GSTP1, COMT, NQO1, TS-SULT and MPO in buffy coat DNA using PCR-based methods. All subjects were interviewed through a questionnaire on smoking, dietary habits and other risk factors. No specific pattern was evident for p53 mutations. Eight out of ten mutations occurred in grade 3 tumors. All p53 mutations occurred in subjects with the COMT mutated allele (p=0.03). The prevalence of cases with p53 mutations was 3.5-fold higher in subjects with wild type than in those with variant GSTP1 alleles (p=0.03). The other polymorphisms investigated were not associated with p53 mutations.
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PMID:Impact of polymorphisms in xeno(endo)biotic metabolism on pattern and frequency of p53 mutations in bladder cancer. 1076 40

The ability of the naturally-occurring naphthoquinone derivatives, juglone and plumbagin, to increase tissue activities of the Phase II detoxification enzymes quinone reductase (QR) and glutathione transferase (GT) has been investigated in rats. Groups of female Sprague-Dawley rats were dosed by oral intubation on 5 consecutive days with either juglone or plumbagin at 12.5, 25, 50, 75, 100 or 125 mumoles/kg/day. The animals were then killed and the activities of QR and GT determined in tissue homogenates. The naphthoquinone derivatives had no significant effect on enzyme activities in the liver, spleen, heart, lung or urinary bladder. Increases in the activities of one or both enzymes were recorded, however, in the caecum, kidney, forestomach, duodenum, colon, glandular stomach and jejunum. The possibility that induction of Phase II enzymes could contribute to the previously-reported ability of juglone and plumbagin to protect animals against chemically-induced intestinal neoplasia is discussed.
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PMID:Induction of quinone reductase and glutathione transferase in rat tissues by juglone and plumbagin. 1090 56

A novel prodrug activation system, endogenous in human tumor cells, is described. A latent enzyme-prodrug system is switched on by a simple synthetic, small molecule co-substrate. This ternary system is inactive if any one of the components is absent. CB 1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide] is an antitumor prodrug that is activated in certain rat tumors via its 4-hydroxylamine derivative to a potent bifunctional alkylating agent. However, human tumor cells are resistant to CB 1954 because they are unable to catalyze this bioactivation efficiently. A human enzyme has been discovered that can activate CB 1954, and it has been shown to be commonly present in human tumor cells. The enzyme is NQO2 [NAD(P)H quinone oxidoreductase 2], but its activity is normally latent, and a nonbiogenic co-substrate such as NRH [nicotinamide riboside (reduced)] is required for enzymatic activity. There is a very large (100-3000-fold) increase in CB 1954 cytotoxicity toward either NQO2-transfected rodent or nontransfected human tumor cell lines in the presence of NRH. Other reduced pyridinium compounds can also act as co-substrates for NQO2. Thus, the simplest quaternary salt of nicotinamide, 1-methyl-3-carboxamidopyridinium iodide, was a co-substrate for NQO2 when reduced to the corresponding 1,4-dihydropyridine derivative. Increased chain length and/or alkyl load at the 1-position of the dihydropyridine ring improved specific activity, and compounds more active than NRH were found. However, little activity was seen with either the 1-benzyl or 1-(2-phenylethyl) derivatives. A negatively charged substituent at the 3-position of the reduced pyridine ring also negated the ability of these compounds to act as cosubstrates for NQO2. In particular, 1-carbamoylmethyl-3-carbamoyl-1,4dihydropyridine was shown to be a co-substrate for NQO2 with greater stability than NRH, with the ability to enter cells and potentiate the cytotoxicity of CB 1954. Furthermore, this agent is synthetically accessible and suitable for further pharmaceutical development. NQO2 activity appears to be related to expression of NQO1 (DT-diaphorase), an enzyme that is known to have a favorable distribution toward certain human cancers. NQO2 is a novel target for prodrug therapy and has a unique activation mechanism that relies on a synthetic co-substrate to activate an apparently latent enzyme. Our findings may reopen the use of CB 1954 for the direct therapy of human malignant disease.
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PMID:Bioactivation of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB 1954) by human NAD(P)H quinone oxidoreductase 2: a novel co-substrate-mediated antitumor prodrug therapy. 1094 27

NAD(P)H:quinone oxidoreductase (NQO1) is a polymorphic enzyme involved in the detoxification of potentially mutagenic and carcinogenic quinones. The homozygous C609T NQO1 genotype resulting in loss of reductase activity is found in 2-20% of individuals. In the present study, the NQO1-dependent risk for sporadic colorectal cancer (CRC) was studied in 247 incident CRC cases and 296 hospital-based controls recruited during 1996-1997. Four subgroups of cases were studied: (i) all CRCs; (ii) a molecular CRC subgroup (n = 117, cases with molecular tumor analyses); (iii) within the molecular subgroup those tumors with K-ras mutations in codon 12 (CRC K12); (iv) within the molecular subgroup those tumors with K-ras mutations in codon 13 (CRC K13). The C609T NQO1 genotype was found to be twice as prevalent in all CRC patients (6.8%) compared with controls (3%) and six times more common in the subset CRC K12 (20%). Multivariant analyses in the overall population of 247 cases and 296 controls showed a significant age and gender adjusted risk for CRC associated with the C609T NQO1 genotype (OR 2.9, 95% CI 1.19-6.97; P = 0.01) or with any variant genotype (the low activity allele frequency, i.e. heterozygotes plus homozygotes) (OR 1.41, 95% CI 1.02-1.92; P = 0.03). Within cases of the molecular subgroup (n = 117) the C609T NQO1 genotype was associated with the presence of K-ras codon 12 mutation (OR 6.5 95%, CI 1.39-34.9; P = 0.003). Logistic regression showed an age and gender adjusted risk for K-ras codon 12 mutant CRC associated with the C609T NQO1 genotype (OR 10.5, 95% CI 2.99-36.7; P: = 0.0002) or with any variant NQO1 genotype (OR 2.23, 95% CI 1.23-4.00; P = 0.007) compared with the control group. Genetically determined variations in NQO1 may modify the risk for CRC and these risks may be greatest for tumors containing K-ras codon 12 mutations. CRC with K-ras codon 12 mutations may represent a distinct and etiologically more homogeneous subtype of the disease, which may be associated with toxicants that are metabolized via a NQO1-dependent pathway.
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PMID:NAD(P)H:quinone oxidoreductase-dependent risk for colorectal cancer and its association with the presence of K-ras mutations in tumors. 1102 38

An extensive body of evidence supports the conclusion that by catalyzing obligatory two-electron reductions of quinones to hydroquinones, NAD(P)H:quinone reductase (QR1) protects cells against the deleterious effects of redox cycling of quinones, their ability to deplete glutathione, and to produce neoplasia. The effects of elevation of QR1 levels by various enzyme inducers, inhibition of the enzyme by dicumarol, and genetic deletion of the enzyme (knockout mouse) are all consistent with the proposed protective functions. Measurement of QR1 activity in murine hepatoma cells grown in 96-well microtiter plates has provided a rapid and quantitative method for detecting inducer activity and determining inducer potency. This constitutes a strategy for the identification of potential chemoprotectors against cancer. Epidemiological studies show that humans who are genetically deficient in QR1 are more susceptible to the hematological toxicity and carcinogenicity of benzene exposure, and may be more susceptible to the development of a number of malignant tumors.
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PMID:Persuasive evidence that quinone reductase type 1 (DT diaphorase) protects cells against the toxicity of electrophiles and reactive forms of oxygen. 1103 51


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