Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A variety of purine analogs inhibit the growth and induce the differentiation of human promyelocytic leukemia (HL-60) cells that lack the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Mechanisms by which purine analogs induce differentiation offer unique potential for cancer chemotherapy. The guanine analogs, 6-thioguanine and 8-azaguanine, induce granulocytic differentiation of HGPRT-deficient HL-60 promyelocytes. Although these compounds are useful as model purine analogs that induce differentiation in HGPRT-deficient HL-60 cells, they suffer the disadvantage that they are highly cytotoxic to wild-type cells. We studied the effect of the hypoxanthine analog 6-ethylmercaptopurine on wild-type and HGPRT-deficient HL-60 cells. 6-Ethylmercaptopurine inhibits growth and produces a specific terminal end-cell in both types of HL-60 cells. The mechanism appears to be independent of the normal modes of cytotoxic activation through HGPRT or adenine phosphoribosyltransferase (APRT), since no new peaks were seen in HPLC chromatograms of the nucleotide pools. Furthermore, hypoxanthine and adenine failed to prevent growth inhibition by 6-ethylmercaptopurine, and inhibition of IMP dehydrogenase and the consequential alteration of the guanine nucleotide pools does not appear to be involved. The mechanism differs from that of guanine analog-induced differentiation in HGPRT-deficient HL-60 cells.
Cancer Chemother Pharmacol 1989
PMID:6-ethylmercaptopurine-mediated growth inhibition of HL-60 cells in vitro irrespective of purine salvage. 259 10

Granulocytic maturation of HL-60 promyelocytic leukemia cells induced by dimethylsulfoxide has been shown to produce a decrease in cellular protein phosphotyrosine residues and increases in both tyrosine kinase and protein phosphotyrosine phosphatase activities (D. A. Frank and A. C. Sartorelli, Biochem. Biophys. Res. Commun., 140: 440-447, 1986). These changes have been shown to not be restricted to dimethylsulfoxide-induced differentiation, since similar changes occur in HL-60 cells initiated with retinoic acid and in HL-60 sublines resistant to dimethylsulfoxide-induced differentiation treated with the retinoid. These regulatory events are not directly coupled to growth arrest, which accompanies terminal maturation, since the anthracycline antibiotics aclacinomycin A and marcellomycin, which induce HL-60 differentiation, cause these changes in phosphotyrosine metabolism, while Adriamycin, at a level which produces an equivalent degree of growth inhibition but does not initiate the maturation of HL-60 cells, does not. Furthermore, an HL-60 subline deficient in hypoxanthine-guanine phosphoribosyltransferase, which differentiates in the presence of 6-thioguanine, produced a decrease in phosphotyrosine residues and increases in tyrosine kinase and phosphotyrosine phosphatase activities in response to the purine antimetabolite, while the parental HL-60 line, in which 6-thioguanine inhibits cellular proliferation but does not induce maturation, does not exhibit these changes. Finally, similar alterations in phosphotyrosine regulation were exhibited during anthracycline-induced differentiation of the murine myelomonocytic leukemia cell line WEHI-3B D+, supporting the concept that the phenomena measured represent a general response to inducers of the granulocytic differentiation of leukemia cells.
Cancer Res 1988 Jan 01
PMID:Alterations in tyrosine phosphorylation during the granulocytic maturation of HL-60 leukemia cells. 282 68

It has been demonstrated that restriction fragment length polymorphisms of X-chromosome genes can be used in conjunction with methylation patterns to determine the clonal composition of human tumors. In this report, we show that several X-chromosome probes can be used for such analyses. In particular, probes derived from the hypoxanthine phosphoribosyltransferase gene and the phosphoglycerate kinase gene could be used for clonal analysis in over 50% of American females. The X-inactivation patterns observed with these probes were found to accurately reflect clonality in more than 95% of 92 tumors tested.
Cancer Res 1987 Sep 15
PMID:Clonal analysis using recombinant DNA probes from the X-chromosome. 288 83

Determination of cellular clonality in hematological malignancies provides fundamental information that is important in understanding the pathogenesis of these disorders. We present here an extension of one approach to accomplish this that is based on the interpretation of different methylation patterns on active and inactive X chromosomes within the region of the hypoxanthine-guanine phosphoribosyltransferase gene spanned by a restriction fragment length polymorphism. The successful application of the method to determine clonality is described for three female patients with acute nonlymphocytic leukemia.
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PMID:Determination of clonality in acute nonlymphocytic leukemia by restriction fragment length polymorphism and methylation analysis. 288 56

We have measured the forward mutation rate at the hypoxanthine phosphoribosyltransferase (HPRT) gene of the human promyelocytic leukemia cell line HL-60 and have determined the molecular spectrum of spontaneous HPRT mutations in 45 independent 6-thioguanine-resistant HL-60 sublines. Four fluctuation tests using a total of 132 replicate HL-60 cultures revealed a mean forward mutation rate of HL-60 cells to thioguanine resistance of 1.7-6 x 10(-7)/cell/generation. Blot hybridization analysis of the X-linked HPRT gene using a human HPRT complementary DNA probe revealed abnormalities in HPRT gene structure and/or HPRT mRNA expression in 24 of 45 (53%) independent thioguanine-resistant HL-60 sublines. Six different classes of mutation were identified. The most prevalent (47%; 21 of 45 mutations) consists of mutations that are not detected by blot hybridization analyses and that do not disrupt HPRT mRNA production. These results suggest that a comparatively low forward mutation rate may be found in malignant human cells that exhibit both karyotypic and molecular evidence of genomic instability and that several different molecular classes of mutation may contribute to thioguanine resistance in HL-60, and perhaps in other, malignant human cells. The forward mutation assay system we have developed using the X-linked HPRT gene of HL-60 cells may be useful for analyses of the mutagenic potential and molecular spectrum of mutations produced by chemotherapeutic agents, suspected human mutagens and carcinogens, and phagocyte respiratory burst oxidants in human cells.
Cancer Res 1989 Jan 01
PMID:Molecular analysis of spontaneous hypoxanthine phosphoribosyltransferase mutations in thioguanine-resistant HL-60 human leukemia cells. 290 55

The herpes simplex virus (HSV) thymidine kinase (tk) gene was transfected into Chinese hamster ovary (CHO) 51-11 gly- cells to test its effect on the cytotoxic and mutagenic activity of anti-herpetic nucleoside analogues. Insertion of the viral tk was verified by Southern blot analysis, by sensitivity to acyclovir, and by elevated in vitro thymidine kinase (TK) activity. TK activity was increased by superinfection with a tk- virus and inhibited by antibody to viral TK. Acyclovir (ACV) was somewhat more cytotoxic in the 51-D3 cell line that expresses the viral TK than in the 51-11 parent line. Growth in ACV did not increase over background mutations at the hprt locus. FIAC (2'-fluoro-5-iodio-aracytosine) was slightly cytotoxic to the parent 51-11 line and the tk-containing clone 51-D3. FMAU (2'-fluoro-5-methyl-arauracil) had pronounced cytotoxicity in both cell lines: the 50% survival points were 1.0 microM for 51-11 cells and 0.2 microM for 51-D3. The clone 51-D3 was more sensitive than 51-11 to low concentrations of FIAU (2'-fluoro-5-iodo-arauracil), and when treated with FIAU 51-D3 had a mutation frequency to glycine independence 5 times greater than that of 51-11 cells. With both cell lines the mutation frequency at the hprt locus did not increase after growth in the presence of FIAC or FIAU. A 7-fold increase in mutation frequency at the hprt locus was detected after 51-D3 cells were grown with iododeoxyuridine. Trifluorothymidine was more toxic to 51-D3 than to 51-11 cells and increased the mutation frequency 2-fold. Cytosine-beta-D-arabinofuranoside showed no differential cytotoxicity on the two cell lines and did not increase the mutation frequency at the hprt locus.
Int J Cancer 1987 Jul 15
PMID:A mammalian cell line designed to test the mutagenic activity of anti-herpes nucleosides. 303 17

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


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