Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intercalator-induced DNA strand breaks in mammalian cells represent topoisomerase II:DNA complexes trapped by intercalators. These complexes are detected as protein-associated DNA single-strand breaks (SSB) and DNA double-strand breaks (DSB) by filter elution. Using Chinese hamster lung fibroblasts (V79 cells) that were treated for 30 min with various concentrations of 4'-(9-acridinylamino)methanesulfon-m-anisidide or 5-iminodaunorubicin, we measured DNA strand breaks (SSB and DSB), sister chromatid exchanges (SCE), mutations at the hypoxanthine:guanine phosphoribosyltransferase locus, and cell killing. Further, we correlated DNA strand breakage with the three other parameters. Both drugs induced SCE, mutations, and cell killing at concentrations which also produced reversible DNA strand breaks. While the quantity of DSB correlated with SCE, mutations, and cytotoxicity for both drugs, we found more SCE, mutations, and cytotoxicity per SSB in cells treated with 5-iminodaunorubicin than in those treated with 4'-(9-acridinylamino)methanesulfon-m-anisidide. These data show that the DSB (but not the SSB) induced by 4'-(9-acridinylamino)methanesulfon-m-anisidide and 5-iminodaunorubicin at DNA topoisomerase II binding sites correlated closely with SCE, mutations, and cell killing and could therefore be responsible for their production.
Cancer Res 1985 Jul
PMID:Correlations between intercalator-induced DNA strand breaks and sister chromatid exchanges, mutations, and cytotoxicity in Chinese hamster cells. 298 62

The metabolic activation of the carcinogens N-nitrosobis(2-oxopropyl)amine (BOP) and N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) by Fischer rat and Syrian hamster hepatocytes was investigated in order to determine the existence of species differences in the induction of cell mutation. The conversion of BOP and HPOP into forms mutagenic to V79 cells was studied by using the hepatocyte-mediated mutagenicity assay. Mutations at the hypoxanthine:guanine phosphoribosyltransferase locus and the Na-K-ATPase locus were scored by the induction of 6-thioguanine resistance (TGr) or ouabain resistance (Ouar), respectively. Hepatocytes of both species were capable of converting BOP and HPOP to mutagens for V79 cells in a dose-dependent manner. Metabolism of BOP by rat hepatocytes resulted in higher mutation frequencies than that by hamster hepatocytes. At a BOP concentration of 240 microM, rat hepatocyte metabolism yielded 90.7 TGr mutants and 19.5 Ouar mutants per 10(5) V79 cells. At the same concentration, hamster hepatocyte metabolism of BOP yielded 54.1 TGr mutants and 13.0 Ouar mutants per 10(5) V79 cells. These results did not correlate with the known carcinogenic potency of BOP in the hamster as compared to the rat. Hamster hepatocytes carried out the catabolism of BOP to CO2 at faster rates than rat hepatocytes; therefore, the species difference in mutagenic activation was not due to a defect in BOP uptake or metabolism by hamster hepatocytes. In contrast, metabolism of HPOP by hamster hepatocytes resulted in significantly higher mutation frequencies than that by rat hepatocytes. At an HPOP concentration of 240 microM, hamster hepatocyte metabolism yielded 83.5 TGr mutants per 10(5) V79 cells; rat hepatocyte metabolism yielded only 19.8 TGr mutants per 10(5) V79 cells. This species difference in mutagenic activation correlated well with the known potency of HPOP as a carcinogen for the hamster as compared to the rat. Since hamster pancreatic cells and subcellular fractions are known to have very limited capacity to perform the metabolic activation of HPOP, the results of this study imply that liver metabolism plays an important role in the conversion of HPOP to an agent(s) which subsequently affects the hamster pancreas. The mutagenic potency of BOP versus HPOP was compared after metabolism by hepatocytes from both species. Following their metabolism by hamster hepatocytes, the two compounds were nearly equivalent in mutagenic potency. After metabolism by rat hepatocytes, BOP was significantly more potent mutagen than HPOP.(ABSTRACT TRUNCATED AT 400 WORDS)
Cancer Res 1987 Sep 15
PMID:Species specificity in the metabolism of N-nitrosobis(2-oxopropyl)amine and N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine to mutagens by isolated rat and hamster hepatocytes. 311 24

Neocarzinostatin (NCS) is mutagenic in bacteria, yeast, fungi, and mammalian cells. In cell-free systems, DNA strand breakage induced by NCS requires a reducing agent like 2-mercaptoethanol, unless very high (greater than 100 micrograms/ml) concentrations of NCS are used. In this study, we have investigated the role of the sulfhydryl compound glutathione (GSH), which is usually the most common intracellular thiol, in the bioactivation of NCS to a toxic and mutagenic species. Chinese hamster V79 cells were pretreated with one of two GSH depleting agents, buthionine sulfoximine or diethyl maleate. These agents deplete GSH via different mechanisms, but both will lower GSH levels within the cell to less than 5% of control (untreated) values. GSH-depleted cells and control cells were then exposed to NCS concentrations of 0.5-2.5 micrograms/ml for 1 h, assayed for survival, and plated for expression of hypoxanthine-guanine phosphoribosyltransferase-negative (HGPRT-) mutants. After an expression period of 7 days, during which the cultures were subcultured twice, HGPRT- mutants were selected by plating in hypoxanthine-free medium containing 5 micrograms of 6-thioguanine per ml, at a density of 2 X 10(5) cells per 100 mm dish. NCS alone decreased the surviving fraction to about 1% at 2.5 micrograms/ml and produced dose-related increases in HGPRT-mutants that reached greater than 10 times the spontaneous mutation frequency at 2.5 micrograms NCS per ml. In GSH-depleted cells, however, NCS was only mildly cytotoxic (60-80% surviving fraction) and did not produce dose-related increases in HGPRT- mutants over cells treated only with diethyl maleate or buthionine sulfoximine. Thus, GSH appears to be the main reducing agent for the bioactivation of NCS to a toxic and mutagenic species in Chinese hamster V79 cells.
Cancer Res 1985 Oct
PMID:Glutathione dependence of neocarzinostatin cytotoxicity and mutagenicity in Chinese hamster V-79 cells. 316 10

In an attempt to elucidate the role of somatic mutation in the development of resistance to cancer chemotherapy, an assay was sought to measure the frequency of hypoxanthine-guanine phosphoribosyltransferase (HPRT) mutants in human tumors. Based on the same principle as [3H]thymidine/autoradiography, a method was developed to identify cell proliferation using the thymidine analog 5-bromo-2'-deoxyuridine (BrdUrd). BrdUrd incorporation into DNA was measured following the immunofluorescent staining of fixed cells using a monoclonal antibody highly specific for this nucleoside analog. The human leukemic cell line, CCRF-CEM, was used to investigate the conditions necessary for the stringent selection of HPRT- mutants using 6-thioguanine (6TG). The appropriate 6TG exposure necessary to inhibit BrdUrd incorporation in wild-type cells, while allowing proliferation of spontaneous HPRT- mutants, was greater than or equal to 30 microM 6TG for 72 h (10 microM BrdUrd added 24 h prior to harvest). BrdUrd did not affect the growth of HPRT- mutants in the presence of 6TG. BrdUrd-labeled 6TG-resistant cells were enumerated flow cytometrically using fluorescent microspheres as an internal standard and the nonparametric, Kolmogorov-Smirnov test was used for independent statistical analysis of the subpopulations of fluorescent, 6TG-resistant cells. Evidence that CCRF-CEM cells which incorporated BrdUrd in the presence of 6TG were, in fact, HPRT- mutants was sought. It was demonstrated that spontaneous 6TG-resistant cells from the CCRF-CEM population were reduced by growth in medium containing aminopterin. The mutant frequency in the CCRF-CEM cell line was found to be 4.28 x 10(-5) +/- 2.04 x 10(-5) using the BrdUrd/flow cytometric technique.
Cancer Res 1988 Nov 01
PMID:Flow cytometric enumeration of drug-resistant tumor cells. 316 54

By cloning T cells, mutations at the hypoxanthine-guanine phosphoribosyltransferase locus were quantified in peripheral blood lymphocytes of 12 patients with connective tissue diseases receiving long-term cyclophosphamide. Frequency of mutation was higher than in control subjects and was related to the duration of therapy; therefore, some cells with mutations are long-lived, and these cells accumulate in the peripheral circulation. Mutation frequency was also independently related to age. The results indicate that even low doses of cyclophosphamide are mutagenic and may explain, in part, why these patients are at risk of drug-induced malignancy.
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PMID:Use of T cell cloning to detect in vivo mutations induced by cyclophosphamide. 328 48

A lymphocyte clonal assay developed to quantitate in vivo somatic cell mutations at the hypoxanthine-guanine phosphoribosyltransferase locus was modified in order to study resistance to methotrexate. Even though nucleoside-free culture conditions were used methotrexate was not lethal to lymphocytes plated into micro-wells at greater than 10(2) cells/well. HPLC analysis of supernatants from wells plated initially with 10(4) cells/well in 100 microM methotrexate revealed the presence of micro-molar levels of hypoxanthine and thymidine by the 5th and 8th day of culture respectively. When lymphocytes were plated at less than or equal to 10(2) cells/well in nucleoside free medium, methotrexate was cytotoxic and micro-molar levels of thymidine together with hypoxanthine protected lymphocytes cultured under these conditions from toxicity. Modulation of nucleic acid antimetabolite cytotoxicity by nucleosides and bases has been recognised for some years. Nucleoside free culture conditions have been advocated for studying cellular sensitivity to antifolates to avoid such interfering factors. However our results indicate that metabolites from dying or damaged cells can prevent methotrexate cytotoxicity, further complicating the development of a suitable clonogenic assay for investigating antifolate sensitivity.
Br J Cancer 1988 May
PMID:Modulation of antifolate cytotoxicity by metabolites from dying cells in a lymphocyte clonal assay. 339 52

The aim of the study was to establish enzyme-deficient mutants of the human permanent cell line U-937. Following chemical mutagenesis with the use of ethyl methanesulfonate, this cell line was chronically exposed to increasing concentrations of the toxic hypoxanthine analogue 6-thioguanine. Cells surviving hypoxanthine-aminopterin-thymidine selective media were separated by glass adherence with the use of 12-O-tetradecanoyl-phorbol-13-acetate. Three mutant clones were established, which have remained hypoxanthine phosphoribosyltransferase (HPRT) deficient for a period of 7 months, as shown by indirect measurements with the use of autoradiography and scintillation counting of cells exposed to [3H]hypoxanthine. Since the phenotypic properties and growth behavior of U-937 cells have remained unaltered after the induced mutation, a highly restricted chromosomal segment coding for HPRT seems to have been mutated.
J Natl Cancer Inst 1986 Feb
PMID:Induction of hypoxanthine phosphoribosyltransferase deficiency in human U-937 cells. 345 59

It has recently been reported that human osteosarcomas may lack the purine salvage pathway enzyme, hypoxanthine:guanine phosphoribosyltransferase (EC 2.4.2.8). We have established a quantitative assay for measurement of this enzyme in human osteosarcoma xenografts with analysis of products by thin-layer chromatography. Nucleotidase or phosphatase activity was readily detected and could be abolished by preheating cytosol at 60 degrees C for 10 min and performing the assay at pH 10. Alternatively, the use of 25 mM NaF at pH 7.4 also inhibited this activity. The pH optimum for this enzyme in red blood cell sonicates and tumor cytosols was pH 10. All six human osteosarcoma xenografts contained hypoxanthine:guanine phosphoribosyltransferase activity ranging from 0.97 to 4.06 nmol/min/mg of protein at pH 7.4. Control human red blood cell sonicates demonstrated activity of 0.83 nmol/min/mg of protein. These data demonstrate that human osteosarcoma xenografts contain substantial activities of this purine salvage pathway enzyme.
Cancer Res 1986 Oct
PMID:Hypoxanthine:guanine phosphoribosyltransferase activity in xenografts of human osteosarcoma. 346 7

The genetic stability of normal and neoplastic lymphocytes was compared by using base-line mutation frequency and mutation rate/cell generation. Mutations at the hypoxanthine-guanine phosphoribosyltransferase locus were studied by enumerating thioguanine-resistant cells in a clonogenic assay. The base-line ("spontaneous") mutation frequency was 1.52 X 10(-6), 6.38 X 10(-6), and 1.06 X 10(-6) for normal cells from three individuals and was 1.16 X 10(-3), 6.08 X 10(-5), and 3.06 X 10(-5) for the three malignant cell lines, Jurkat (JM), HRIK, FMC-Hu1B, respectively. The mutation cell/generation rate was 24.6 X 10(-8), 15 X 10(-8), and 5.5 X 10(-8) for lymphocytes from the three normal individuals, and 666.4 X 10(-8), 52.8 X 10(-8), and 131 X 10(-8) for the three malignant cell lines. The results suggest that neoplastic lymphocytes are more genetically unstable than normal lymphocytes.
Cancer Res 1987 Jan 15
PMID:Mutation rate of normal and malignant human lymphocytes. 346 91

The cell surface antigen associated with the transformed state of cells that could grow in an anchorage-independent manner was analyzed by use of techniques of DNA transfection and hybridomas secreting the monoclonal antibody (MoAb). Spleen cells of C57BL/6 mice immunized with a highly tumorigenic, chemically induced murine cultured colon 36 tumor (C-C36) of BALB/c origin were hybridized with NS-1, a hypoxanthine phosphoribosyltransferase-deficient myeloma line of BALB/c mice. Screening of hybridomas revealed an antibody that reacted with C-C36 and transformed Swiss 3T3 cells growing in soft agar after transfection of 3T3 cells with C-C36 DNA. The hybridomas that did not react with nontransformed 3T3 and the less tumorigenic BALB/c hemangioendothelioma line D10 were then selected. An MoAb was designated "#71295." This MoAb immunoprecipitated the antigen that consisted of 65,000- and 14,000-molecular-weight components with soluble C-C36 membrane antigens. It also reacted with 2 other chemically induced syngeneic colon tumor lines, cultured colon 26 tumor line and cultured colon 51 tumor line, and with fibrosarcoma Meth A. However, #71295 was not found in NS-1, D14, and BALB/c normal thymus, liver, colon, and kidney tissues. In addition, this MoAb could not inhibit the anchorage-independent growth of C-C36 and transformed 3T3 cells. These results suggest that although the molecule defined by #71295 might not be associated with the anchorage independence of cell growth, it could be a newly expressed determinant on the cell surface that is related to the events of cell transformation.
J Natl Cancer Inst 1987 Feb
PMID:Identification of transformation-related antigen by monoclonal antibody on Swiss 3T3 cells induced by transfection with murine cultured colon 36 tumor DNA. 346 94


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