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)

Vinyl acetate monomer (VAM) produced rat nasal tumors at concentrations in the hundreds of parts per million. However, VAM is weakly genotoxic in vitro and shows no genotoxicity in vivo. A European Union Risk Assessment concluded that VAM's hydrolysis to acetaldehyde (AA), via carboxylesterase, is a critical key event in VAM's carcinogenic potential. In the following study, we observed increases in micronuclei (MN) and thymidine kinase (Tk) mutants that were dependent on the ability of TK6 cell culture conditions to rapidly hydrolyze VAM to AA. Heat-inactivated horse serum demonstrated a high capacity to hydrolyze VAM to AA; this activity was highly correlated with a concomitant increase in MN. In contrast, heat-inactivated fetal bovine serum (FBS) did not hydrolyze VAM and no increase in MN was observed. AA's ability to induce MN was not impacted by either serum since it directly forms Schiff bases with DNA and proteins. Increased mutant frequency at the Tk locus was similarly mitigated when AA formation was not sufficiently rapid, such as incubating VAM in the presence of FBS for 4 hr. Interestingly, neither VAM nor AA induced mutations at the HPRT locus. Finally, cytotoxicity paralleled genotoxicity demonstrating that a small degree of cytotoxicity occurred prior to increases in MN. These results established 0.25 mM as a consistent concentration where genotoxicity first occurred for both VAM and AA provided VAM is hydrolyzed to AA. This information further informs significant key events related to the mode of action of VAM-induced nasal mucosal tumors in rats.
 ...
PMID:Nonlinear responses for chromosome and gene level effects induced by vinyl acetate monomer and its metabolite, acetaldehyde in TK6 cells. 2403 27

Assays measuring mutant frequencies in endogenous reporter genes are used for identifying potentially genotoxic environmental agents and discovering phenotypes prone to genomic instability and diseases, such as cancer. Here, we describe methods for identifying mouse spleen lymphocytes with mutations in the endogenous X-linked hypoxanthine guanine phosphoribosyl transferase (Hprt) gene and the endogenous autosomal thymidine kinase (Tk) gene. The selective clonal expansion of mutant lymphocytes is based upon the phenotypic properties of HPRT- and TK-deficient cells. The same procedure can be utilized for quantifying Hprt mutations in most strains of mice (and, with minor changes, in other mammalian species), while mutations in the Tk gene can be determined only in transgenic mice that are heterozygous for inactivation of this gene. Expanded mutant clones can be further analyzed to classify the types of mutations in the Tk gene (small intragenic mutations vs. large chromosomal mutations) and to determine the nature of intragenic mutation in both the Hprt and Tk genes.
...
PMID:Analysis of in vivo mutation in the Hprt and Tk genes of mouse lymphocytes. 2462 34

Human embryonic stem cells (hESCs) hold great promise in the regenerative therapy of many currently untreatable human diseases. One of the key bottlenecks is the immune rejection of hESC-derived allografts by the recipient. To overcome this challenge, we have established new approaches to induce immune protection of hESC-derived allografts through the coexpression of immune suppressive molecules CTLA4-Ig and PD-L1. However, this in turn raises a safety concern of cancer risk because these hESC-derived cells can evade immune surveillance. To address this safety concern, we developed a safety checkpoint so that the immune evasive hESC-derived cells in the graft can be effectively eliminated if any cellular transformation is detected. In this context, we knock-in the suicidal gene herpes simplex virus thymidine kinase (HSVTK) into the constitutive HPRT locus of CP hESCs (knock-in hESCs expressing CTLA4-Ig and PD-L1), denoted CPTK hESCs. Employing humanized mice (Hu-mice) reconstituted with human immune system, we demonstrated that the CPTK hESC-derived cells are protected from immune rejection. In addition, CPTK hESC-derived cells can be efficiently eliminated in vitro and in vivo with FDA approved TK-targeting drug ganciclovir. Therefore, this new safety checkpoint improves the feasibility to use the immune evasive hESC-derived cells for regenerative medicine. Stem Cells 2017;35:1154-1161.
 ...
PMID:A Safety Checkpoint to Eliminate Cancer Risk of the Immune Evasive Cells Derived from Human Embryonic Stem Cells. 2809 Jul 51

Determining mutant frequencies in endogenous reporter genes is a tool for identifying potentially genotoxic environmental agents, and discovering phenotypes prone to genomic instability and diseases, such as cancer. Here, we describe a high-throughput method for identifying mouse spleen lymphocytes with mutations in the endogenous X-linked hypoxanthine guanine phosphoribosyl transferase (Hprt) gene and the endogenous autosomal thymidine kinase (Tk) gene. The selective clonal expansion of mutant lymphocytes is based upon the phenotypic properties of HPRT- and TK-deficient cells. The same procedure can be utilized for quantifying Hprt mutations in most strains of mice (and, with minor changes, in other mammalian species), while mutations in the Tk gene can be determined only in transgenic mice that are heterozygous for inactivation of this gene. Expanded mutant clones can be further analyzed to classify the types of mutations in the Tk gene (small intragenic mutations vs. large chromosomal mutations) and to determine the nature of intragenic mutation at both the Hprt and Tk genes.
 ...
PMID:Analysis of In Vivo Mutation in the Hprt and Tk Genes of Mouse Lymphocytes. 3198 65


<< Previous 1 2 3 4 5 6 7 8