BACKGROUND To evaluate the impact of dihydrofolate reductase (DHFR) and reduced folate carrier (RFC) genes on methotrexate (MTX) resistance in osteosarcoma cells in relation to retinoblastoma (RB1) gene status. MATERIALS AND METHODS A series of human osteosarcoma cell lines-either sensitive or resistant to MTX-and 16 osteosarcoma tumour samples were used in this study. RESULTS In U-2OS MTX-...

Many examples of internal translation initiation in eucaryotes have accumulated in recent years. In many cases terminators of upstream reading frames precede the internal initiation site, suggesting that translational reinitiation may be a mechanism for initiation at internal AUGs. To test this idea, a series of recombinants was constructed in the mammalian expression vector pSV2. Each containe...

Dihydrofolate reductase (DHFR) was measured during the development in rats of brain tumors induced following inoculation with avian sarcoma virus. Increasing activity of this enzyme in brain was correlated with the course of primary brain tumor growth. The specific activities of DHFR in primary human brain tumor tissues were comparable to those found in avian sarcoma virus-induced brain tumors ...

para-Aminosalicylic acid (PAS) is one of the antimycobacterial drugs currently used for multidrug-resistant tuberculosis. Although it has been in clinical use for over 60 years, its mechanism(s) of action remains elusive. Here we report that PAS is a prodrug targeting dihydrofolate reductase (DHFR) through an unusual and novel mechanism of action. We provide evidences that PAS is incorporated i...

It has been long recognized that in mammalian cells, DNA damage is preferentially repaired in the transcribed strand of transcriptionally active genes. However, recently, we found that in Chinese hamster ovary (CHO) cells, UV-induced cyclobutane pyrimidine dimers (CPDs) are preferentially repaired in both the transcribed and the non-transcribed strand of exon 1 of the dihydrofolate reductase (D...

Several variants resistant to 1.8 x 10(-4) M DL-methotrexate (MTX) have been isolated from the human cell lines HeLa BU25 and VA2-B by exposing them to progressively increasing concentrations of the drug. A striking variability of phenotype and chromosome constitution was observed among the different variants. All resistant cell lines exhibited a greatly increased dihydrofolic acid reductase (D...

Human cells exposed to antifolates show a rapid increase in the levels of the enzyme dihydrofolate reductase (DHFR). We hypothesized that this adaptive response mechanism can be used to elevate cellular levels of proteins fused to DHFR. In this study, mouse cells transfected to express a green fluorescent protein-DHFR fusion protein and subsequently exposed to the antifolate trimetrexate (TMTX)...

AIM OF DATABASE The aim of the Danish Heart Failure Registry (DHFR) is to monitor and improve the care of patients with incident heart failure (HF) in Denmark. STUDY POPULATION The DHFR includes inpatients and outpatients (≥18 years) with incident HF. Reporting to the DHFR is mandatory for the Danish hospital departments treating patients with incident HF. Final decision to register a patient...

The enzyme DHFR (dihydrofolate reductase) catalyses hydride transfer from NADPH to, and protonation of, dihydrofolate. The physical basis of the hydride transfer step catalysed by DHFR from Escherichia coli has been studied through the measurement of the temperature dependence of the reaction rates and the kinetic isotope effects. Single turnover experiments at pH 7.0 revealed a strong dependen...

Sulfadoxine-pyrimethamine (SP), the current first line antimalarial drug in Tanzania, is compromised by evolution and spread of mutations in the parasite's dhfr and dhps genes. In the present study we established the baseline frequencies of Plasmodium falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) mutant genotypes and their potential for predicting the in vivo...