Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies on a series of benzoquinazoline folate analogues as inhibitors of human thymidylate synthase led to the selection of 1843U89 for further evaluation. This compound had a Ki of 90 pM versus human thymidylate synthase and was noncompetitive with (6R,S)-5,10-methylenetetrahydrofolate. It was a good substrate for the addition of the second glutamate by hog liver folylpolyglutamate synthetase, having a Vmax/Km value 7.8-fold higher than (6R,S)-tetrahydrofolate. The data indicate that 1843U89 was transported into cells via the reduced folate carrier. The Kt for 1843U89 in MOLT-4 cells was 0.33 microM, which was 3-fold lower than that for methotrexate and 16-fold lower than that for (6S-5-formyltetrahydrofolate. V/K values were 20.3 for 1843U89 versus 1.2 and 1.9 for methotrexate and (6S)-5-formyltetrahydrofolate, respectively. It was a potent inhibitor of the growth of human cells, having 50% inhibitory concentrations below 1 nM for all cell lines tested. Growth inhibition was reversed by thymidine alone, indicating that thymidylate synthase was the only site of action of this compound. Growth inhibition was not affected by (6R,S-5-formyltetrahydrofolate at concentrations below 5 microM. However, the 50% inhibitory concentration increased when the concentration in the medium was increased to 100 microM, presumably due to competition for transport. Relative to the human cell lines used, murine cell lines were 80-1300-fold less sensitive to 1843U89 and the other benzoquinazolines tested. This decreased sensitivity appeared to be due, at least in part, to decreased transport or accumulation in murine cells. Ki values for inhibition of methotrexate transport for the benzoquinazolines were 5-17-fold higher in L1210 cells than in MOLT-4 cells. 1843U89, the benzoquinazoline which was transported most efficiently and which was the most potent inhibitor of the growth of human cells, exhibited the largest difference between binding to the MOLT-4 human and L1210 murine transporter. The V/K for L1210 transport was 80-fold less than that for MOLT-4. Initial antitumor studies, using the human thymidine kinase-deficient line GC3TK- to circumvent problems associated with murine transport as well as the high circulating thymidine levels in mice, indicated that 1843U89 had marked in vivo antitumor activity.
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PMID:Biochemical and cellular pharmacology of 1843U89, a novel benzoquinazoline inhibitor of thymidylate synthase. 842 62

ZD9331 is a novel, potent thymidylate synthase (TS) inhibitor which does not require polyglutamation by folylpolyglutamate synthetase (FPGS) for its activity. In contrast to Tomudex (ZD1694), ZD9331 may therefore be active against tumours with low FPGS activity. ZD9331 shows anti-tumour activity by both 24-h infusion and bolus administration in the murine thymidine kinase-deficient (TK -/-) lymphoma L5178Y. In view of the history of renal toxicity with some earlier TS inhibitors and the possible therapeutic use of bolus ZD9331, we have examined the effects of bolus ZD9331 dose and route of administration on plasma and kidney pharmacokinetics and renal function in mice. Renal function was assessed by measuring [14C]inulin clearance, and drug concentrations were assayed by reverse-phase high-performance liquid chromatography (HPLC). Renal function was unaffected by ZD9331 up to 150 mg kg(-1) either i.v. or i.p. However, at 200 mg kg(-1), glomerular filtration rate was significantly inhibited following i.v. but not i.p. administration. Pharmacokinetic studies showed that these effects were consistent with the markedly higher plasma drug concentrations occurring during early times following i.v. dosing, although the plasma drug profiles were otherwise similar for both routes. Kidney drug concentrations were slightly elevated in i.v.- versus i.p.-treated animals at the low dose (50 mg kg(-1)), with a correspondingly larger area under the curve. However, at the highest dose (200 mg kg(-1)), peak kidney drug concentrations were 20-fold higher following i.v. administration than after i.p., with marked kidney retention, resulting in a 50-fold greater kidney drug exposure for the i.v. versus the i.p. route. These data show that ZD9331 is non-nephrotoxic at active anti-tumour doses (50 mg kg(-1) i.p.) in mice, and only at very high bolus i.v. doses is there impaired renal function as a result of very high peak plasma concentrations. These adverse effects can be readily overcome by i.p. administration, indicating the likely need for short infusions in clinical settings.
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PMID:The renal effects of the water-soluble, non-folylpolyglutamate synthetase-dependent thymidylate synthase inhibitor ZD9331 in mice. 983 78

Pretherapeutic determination of tumor resistance to chemotherapy is a main challenge, hindered by the low number of mechanisms characterized at the same time, the small size of the clinical specimens and the heterogeneity of the techniques or the lack of true quantification. The aim of the present study was to determine in real time quantitative RT-PCR, tumor cell expression of several transcripts involved in cancer cell resistance with a unique cDNA sample from a tumor biopsy. The technique had to be suitable in clinical practice for determination of several factors involved in resistance to a given drug family, for example, fluoropyrimidines resistance factors: thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine kinase (TK), dihydrofolate reductase (DHFR), folylpolyglutamate synthetase (FPGS). A frame-shifted artificial construct was designed specifically to work within the same conditions. We validated our technique by quantifying expressions of these 5 genes starting from tissue samples of colorectal carcinoma and the surrounding normal mucosa of 33 different patients. That real time quantitative RT-PCR technique using the frame-shifted artificial construct as a standard provided a real comparison and quantification of different resistance factors. Tumor resistance phenotype determination based on that approach will be investigated in a control study.
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PMID:Tumor quantification of several fluoropyrimidines resistance gene expression with a unique quantitative RT-PCR method. Implications for pretherapeutic determination of tumor resistance phenotype. 1638 26