Biomaterial Database

Thymidylate synthase overproduction and gene amplification in fluorodeoxyuridine-resistant human cells. 1985

S H Berger, and C H Jenh, and L F Johnson, and F G Berger

Cytotoxicity to 5-fluoro-2'-deoxyuridine (FdUrd) derives from its conversion to 5-fluorodeoxyuridine-5'-monophosphate, which binds to and inhibits thymidylate synthase (TS) in the presence of the cofactor, 5,10-methylenetetrahydrofolate. We have selected FdUrd-resistant variants of the human cell line HEp-2 following adaptation to stepwise increases in drug concentration. In the initial selection, maximal drug resistance was associated with a 26-fold increase in the cellular level of TS. Greater TS overproduction (80-fold) was obtained by selection for FdUrd resistance in the presence of 10 microM folinic acid and 100 microM deoxyinosine. The latter agents were included to expand the folate pool to ensure adequate levels of cofactor during the selection process. Using cDNA plasmid pMTS-4, which is complementary to mouse TS mRNA, we show that TS overproduction in the HEp-2 variants is accompanied by a 100-fold increase in TS mRNA and a 100-fold amplification of the TS structural gene. Thus, TS overproduction and gene amplification is a mechanism of resistance to FdUrd in human cells.

UI	MeSH Term	Description	Entries
D007822	Laryngeal Neoplasms	Cancers or tumors of the LARYNX or any of its parts: the GLOTTIS; EPIGLOTTIS; LARYNGEAL CARTILAGES; LARYNGEAL MUSCLES; and VOCAL CORDS.	Cancer of Larynx,Laryngeal Cancer,Larynx Neoplasms,Cancer of the Larynx,Larynx Cancer,Neoplasms, Laryngeal,Cancer, Laryngeal,Cancer, Larynx,Cancers, Laryngeal,Cancers, Larynx,Laryngeal Cancers,Laryngeal Neoplasm,Larynx Cancers,Larynx Neoplasm,Neoplasm, Laryngeal,Neoplasm, Larynx,Neoplasms, Larynx
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004351	Drug Resistance	Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.	Resistance, Drug
D004586	Electrophoresis	An electrochemical process in which macromolecules or colloidal particles with a net electric charge migrate in a solution under the influence of an electric current.	Electrophoreses
D005467	Floxuridine	An antineoplastic antimetabolite that is metabolized to fluorouracil when administered by rapid injection; when administered by slow, continuous, intra-arterial infusion, it is converted to floxuridine monophosphate. It has been used to treat hepatic metastases of gastrointestinal adenocarcinomas and for palliation in malignant neoplasms of the liver and gastrointestinal tract.	FUdR,Fluorodeoxyuridine,5-FUdR,5-Fluorodeoxyuridine,5 Fluorodeoxyuridine
D005784	Gene Amplification	A selective increase in the number of copies of a gene coding for a specific protein without a proportional increase in other genes. It occurs naturally via the excision of a copy of the repeating sequence from the chromosome and its extrachromosomal replication in a plasmid, or via the production of an RNA transcript of the entire repeating sequence of ribosomal RNA followed by the reverse transcription of the molecule to produce an additional copy of the original DNA sequence. Laboratory techniques have been introduced for inducing disproportional replication by unequal crossing over, uptake of DNA from lysed cells, or generation of extrachromosomal sequences from rolling circle replication.	Amplification, Gene
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA