Linked Life Data

9850074

Source:http://linkedlifedata.com/resource/pubmed/id/9850074

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
23
pubmed:dateCreated
1998-12-31
pubmed:abstractText
Uridine phosphorylase (UPase) catalyzes the reversible phosphorolysis of uridine to uracil. We purified the enzyme from the murine colon 26 tumor using a two-step procedure through 5-amino-benzylacyclouridine affinity chromatography. Antibodies raised in rabbits against the purified protein revealed single bands in Western blots of normal human tissue and tumor extracts. The polyclonal antibody used to screen a human liver expression library allowed the isolation of a 1.2-kb clone that contained the entire open reading frame of the human UPase. The UPase cDNA has been expressed as a fusion protein in Escherichia coli using the pMal-C2 vector. The kinetic analysis demonstrated that the recombinant UPase preferentially uses uridine, 5-fluorouracil, and uracil as substrates, although lower levels of activity were observed with 2-deoxyuridine and thymidine. Clinical samples of human tumors and adjacent normal tissues were assayed for phosphorolytic activity and sensitivity to 5-benzylacyclouridine (BAU), a potent inhibitor of the enzyme presently in Phase I-II clinical trial. Activity in normal tissues appeared to be low but very sensitive to BAU (approximately 90% inhibition at 10 microM). Tumors had generally 2-3-fold greater activity compared with adjacent normal tissues. In breast cancer specimens and head-neck squamous carcinomas, however, uridine cleavage was only partially inhibited (40-60%) by 10 or 100 microM BAU. The BAU-insensitive activity requires phosphate and pH conditions similar to the normal enzyme, and the new phosphorolytic activity was independent from thymidine phosphorylase. The BAU-insensitive phosphorolytic activity in selected tumors, coupled with the potent inhibitory activity of BAU against the "classical" uridine phosphorylase in normal human tissues, provides the rationale for combining BAU with 5-fluorouracil in the treatment of breast and head-neck tumors.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0008-5472
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
58
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5418-24
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:9850074-Amino Acid Sequence, pubmed-meshheading:9850074-Animals, pubmed-meshheading:9850074-Antibody Specificity, pubmed-meshheading:9850074-Cloning, Molecular, pubmed-meshheading:9850074-DNA, Complementary, pubmed-meshheading:9850074-Drug Screening Assays, Antitumor, pubmed-meshheading:9850074-Enzyme Inhibitors, pubmed-meshheading:9850074-Female, pubmed-meshheading:9850074-Humans, pubmed-meshheading:9850074-Kinetics, pubmed-meshheading:9850074-Mice, pubmed-meshheading:9850074-Mice, Inbred BALB C, pubmed-meshheading:9850074-Molecular Sequence Data, pubmed-meshheading:9850074-Neoplasms, pubmed-meshheading:9850074-Rabbits, pubmed-meshheading:9850074-Sequence Homology, Amino Acid, pubmed-meshheading:9850074-Uracil, pubmed-meshheading:9850074-Uridine, pubmed-meshheading:9850074-Uridine Phosphorylase
pubmed:year
1998
pubmed:articleTitle
Expression, characterization, and detection of human uridine phosphorylase and identification of variant uridine phosphorolytic activity in selected human tumors.
pubmed:affiliation
Yale University School of Medicine, Department of Internal Medicine, New Haven, Connecticut 06520, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.