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Biomedical subjects

G B Grindey

Publications and source records attributed to G B Grindey.

At least 55 records · Page 3Linked to original sources
PubMed1990

Inhibition of ribonucleotide reduction in CCRF-CEM cells by 2',2'-difluorodeoxycytidine.

The new deoxycytidine analogue 2',2'-difluorodeoxycytidine (dFdC) is a specific inhibitor of DNA synthesis that has marked cytotoxicity and therapeutic activity. A 2-hr incubation with 0.1-10 microM dFdC decreased cellular viability 78-97%. This treatment reduced deoxynucleoside triphosphate pools, similar to the action of the ribonucleotide reductase inhibitor hydroxyurea. The most pronounced decrease occurred in the dCTP pool, quantitatively followed by the decrease of dATP, dGTP, and dTTP. In contrast, inhibition of DNA synthesis by arabinosylcytosine did not affect the dCTP level, whereas dATP, dGTP, and dTTP pools increased, but less than 2-fold. The incorporation of [5-3H]cytidine into the dCTP pool, a measure of ribonucleotide reductase activity in whole cells, was reduced to 3% of controls by 0.1 microM dFdC, but to only 40% by 0.1 microM ara-C. Each drug decreased incorporation of [5-3H]cytidine into DNA to a similar extent (greater than 94%), suggesting limitation by a reaction proximal to this step. The cellular concentration of dFdC 5'-diphosphate was 0.3 microM at 50% inhibition of the in situ activity of ribonucleotide reductase. Direct assays of partially purified ribonucleoside diphosphate reductase (EC 1.17.4.1) demonstrated 50% inhibition by 4 microM dFdC 5'-diphosphate; dFdC 5'-triphosphate was much less inhibitory. We conclude that dFdC 5'-diphosphate acts as an inhibitor of ribonucleoside diphosphate reductase.

Cell Line↗
PubMed1989

Evaluation of N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)-urea against xenografts of pediatric rhabdomyosarcoma.

N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)-urea (LY186641), a novel anticancer compound, was evaluated against six lines of rhabdomyosarcoma xenografts, each of which was established from tissue biopsies from untreated patients, and additional sublines selected as xenografts for primary resistance to vincristine, melphalan, and ifosfamide. LY186641 was given by oral gavage twice daily for 10 consecutive days or as 5-day courses repeated at 7-day intervals. At the optimal schedule, complete regressions of advanced tumors were obtained in each of the six rhabdomyosarcoma lines. There was no apparent cross-resistance in RMS lines selected for vincristine resistance or against multiple-drug-resistance KB cells in vitro. There was slight cross-resistance in xenografts selected for melphalan resistance, but not in an ifosfamide-resistant line. These results indicate that LY186641 may have significant clinical activity in the treatment of childhood rhabdomyosarcoma.

Animals↗
PubMed1989

Synthesis and antitumor activity of 5-deaza-5,6,7,8-tetrahydrofolic acid and its N10-substituted analogues.

Syntheses of 5-deaza-5,6,7,8-tetrahydrofolic acid (7a) and its 10-formyl (7b), 10-acetyl (7c), and 10-methyl (7d) derivatives are described. These compounds, prepared as analogues of 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (DDATHF), the lead compound of a new class of folate antimetabolites, exhibit potent growth inhibition against leukemic cells in culture as well as substantial antitumor activity against transplantable murine solid tumors in vivo.

Animals↗
PubMed1989

Vinca alkaloids.

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Animals↗
PubMed1988

Comparison of the cellular pharmacokinetics and toxicity of 2',2'-difluorodeoxycytidine and 1-beta-D-arabinofuranosylcytosine.

2',2'-Difluorodeoxycytidine (dFdC) is a new deoxycytidine analogue with good activity against human leukemic cell lines and murine solid tumors, while the activity of 1-beta-D-arabinofuranosylcytosine (ara-C) is established in experimental systems and for the treatment of human adult leukemia. This study compared the cellular metabolism and cytotoxic properties of dFdC and ara-C in Chinese hamster ovary cells. In wild-type cells, dFdC was significantly more cytotoxic than ara-C after both 4- and 18-h incubations. The 5'-triphosphate of dFdC (dFdCTP) was the major cellular metabolite (85-90%), reaching cellular concentrations up to 20-fold greater than those observed for ara-C 5'-triphosphate at equimolar concentrations of the parent drug. A deoxycytidine kinase-deficient mutant neither accumulated dFdCTP nor showed any cytotoxic response up to drug concentrations of 100 microM. The cytotoxicity of dFdC could be competitively reversed by deoxycytidine further suggesting that dFdC, like ara-C, required phosphorylation by deoxycytidine kinase for biological activity. Several explanations for the different cellular accumulation of the drug triphosphates were established: (a) nucleoside transport studies demonstrated that the membrane permeation of dFdC was 65% more rapid than that of ara-C; (b) deoxycytidine kinase had a higher affinity for dFdC (Km = 3.6 microM) than for ara-C (Km = 8.8 microM), while the Km for deoxycytidine was 1.4 microM; (c) the elimination of intracellular dFdCTP was biphasic with t1/2 alpha = 3.9 and t1/2 beta greater than 16 h while the degradation of ara-CTP was monophasic and significantly faster (t1/2 = 0.7 h). The comparatively long half-life of dFdCTP was related to the prolonged inhibition of DNA synthesis after removal of exogenous nucleoside. Together these factors contribute to the more potent cytotoxicity of dFdC compared with ara-C.

Animals↗
PubMed1987

Pharmacokinetics of the 5'-triphosphates of arabinosylcytosine and 2',2'-difluorodeoxycytidine in L1210 cells.

The clinical efficacy of ara-C is limited by a rapid elimination of the active triphosphate by target cells. The nucleoside antimetabolite, 2',2'-difluorodeoxycytidine, accumulates in leukemia cells as the respective 5'-triphosphate dFdCTP. In contrast to ara-C triphosphate, dFdCTP is eliminated with biphasic kinetics that exhibit a terminal half-life that approaches the cell cycle time. The cellular pharmacokinetics of dFdCTP may explain the unusual dose schedule and spectrum of efficacy against murine tumors.

Animals↗
PubMed1986

Studies of the antitumor activity of (2-alkoxyalkyl)- and (2-alkoxyalkenyl)phosphocholines.

Analogues of the synthetic antitumor phospholipid ALP (1-octadecyl-2-methyl-sn-glycero-3-phosphocholine; alkyl lysophospholipid) in which the 1-ether oxygen atom has been removed have been prepared and evaluated for in vitro and in vivo anticancer activity. Compounds are presented in which the saturated long chain varies in length from 8 to 25 carbon atoms. Sites of unsaturation are also incorporated into the framework in some examples. In particular, rac-(2-ethoxyeicosyl)phosphocholine (10) displays the best in vivo activity of the chemical series against a variety of transplanted tumors and activates murine peritoneal macrophages to express tumor cytotoxicity in vitro. However, 10 does not offer the wide spectrum of antitumor activity we feel necessary to warrant further study.

Animals↗
PubMed1980

Antitumor activity of cytidine dialdehyde and its effects on nucleotide and nucleic acid synthesis.

Cytidine dialdehyde inhibited the growth of leukemia L1210 cells in culture at a 50% inhibitory concentration of 3.5 X 10(-5) M and, when administered i.p. at 200 mg/kg daily for 5 days, increased the mean survival of L1210 tumor-bearing mice by up to 171%. Given by the s.c. or i.v. routes, the compound was ineffective. The ethanol adduct of cytidine dialdehyde, although inactive in cell culture, increased the mean survival of L1210 tumor-bearing mice by up to 225% when administered i.p. but was inactive upon s.c. administration. Exposure of L1210 cells in culture for 25 hr to cytidine dialdehyde at the 50% inhibitory concentration increased the ribonucleoside di- and triphosphate pools, slightly increased deoxyadenosine triphosphate, deoxythymidine triphosphate, and deoxyguanosine triphosphate pools, and caused a pronounced increase in the deoxycytidine triphosphate pool. As determined by the rate of pyrimidine precursor incorporation into nucleic acids, this concentration of drug showed no effect on RNA synthesis but caused a reduction in DNA synthesis to 53% of control. Exposure of L1210 cells for 3 to 6 hr to 10(-4) M cytidine dialdehyde, a concentration which inhibits growth completely, effected an increase in the ribonucleoside di- and triphosphate pools and a rapid decrease of the deoxythymidine triphosphate pool. The deoxycytidine triphosphate and deoxyguanosine triphosphate pools decreased more slowly, and the deoxyadenosine triphosphate pool remained slightly elevated. Analysis of the rate of substrate incorporation into nucleic acids showed that this concentration of drug produced an 80% decrease in RNA synthesis and a 75% decrease in DNA synthesis 3 hr after drug exposure. These results suggest that the mechanism of action of cytidine dialdehyde may be due to its initial interference with DNA synthesis followed by a generalized inhibition of DNA, RNA, and protein synthesis at cytotoxic concentrations.

Animals↗
PubMed1979

Evaluation of ribonucleoside and deoxyribonucleoside triphosphate pools in cultured leukemia cells during exposure to methotrexate or methotrexate plus thymidine.

Continuous exposure to inhibitory concentrations of methotrexate produces distinct rates of steady-state growth of murine leukemia L1210 and human leukemia CCRF-CEM cells in culture. Addition of thymidine to the medium produces reversal (6 to 40%) of this steady-state growth rate inhibition. This study utilized combinations of methotrexate and thymidine for an evaluation of the accompanying relationship between steady-state growth rate and changes in the ribo- and deoxyribonucleoside triphosphate pools. In L1210 cells exposed to methotrexate alone, the deoxythymidine 5'-phosphate (dTTP) pools decreased, whereas deoxyadenosine 5'-triphosphate, deoxyguanosine 5'-triphosphate, and deoxycytidine 5'-triphosphate (dCTP) remained relatively constant up to 70% inhibition of growth rate, with dCTP at a constant 112% of controls. The corresponding ribonucleoside triphosphates decreased only slightly. With the combination of methotrexate and thymidine resulting in up to 40% inhibition of growth rate, there was also a decrease in the dTTP pool while the other deoxyribonucleoside triphosphates remained relatively constant, and the corresponding ribonucleoside triphosphates again decreased only slightly. The dCTP pool was reduced to a constant 42% of control comparable to that produced by thymidine alone. With greater than 40% (with thymidine) or 70% (without thymidine) inhibition of growth rate, all pools decreased, but only dTTP was substantially reduced in proportion to the growth rate inhibition caused by methotrexate. The dTTP pool became depleted in spite of the presence of exogenous thymidine. Evaluation of CCRF-CEM cells indicated that inhibition of growth rate and nucleotide pool perturbations by methotrexate were similar to those observed in L1210 cells. However, in the presence of thymidine, inhibition of growth rate appeared related to decreased pools of dCTP, deoxyadenosine 5'-triphosphate, and deoxyguanosine 5'-triphosphate, rather than dTTP as was observed for L1210 cells. Hence, mammalian cells were capable of responding in a differential fashion to pharmacological perturbations, and this capacity may play a role in determining therapeutic selectivity. Since the ribonucleoside triphosphate decreases were slight and relatively uniform during methotrexate-induced perturbations, the deoxyribonucleoside triphosphate pools appear to be more directly related to inhibition of growth rate. The results are consistent with the concept that slight imbalances in the deoxyribonucleoside triphosphate pools dramatically inhibit DNA synthesis, as mediated through their interaction with DNA polymerase.

Animals↗
PubMed1979

Isolation of a DNA polymerase alpha-associated regulatory protein from calf thymus.

A regulatory protein for DNA polymerase alpha, responsive to noncomplementary deoxyribonucleoside triphosphates, has been isolated from calf thymus. The regulatory protein was separated from DNA polymerase alpha using Affi-Gel Blue and gel filtration. The regulatory protein had a molecular weight of approximately 70,000 as determined by gel filtration, and its activity was nondialyzable, heat labile, and abolished by pronase treatment. In the presence of regulatory protein, DNA polymerase alpha activity, measured by using polydeoxyadenylate-oligodeoxythymidylate as template primer, was inhibited by 2'-deoxyguanosine 5'-triphosphate in a parabolic-competitive fashion [Ki = 15 +/- 1 (S.E.) microM] and by 2'-deoxycytidine 5'-triphosphate in a linear-competitive manner (Ki = 162 +/- 23 microM). Neither the four natural ribonucleoside triphosphates nor 2'-deoxyadenosine 5'-triphosphate inhibited the DNA polymerase-regulatory protein system to any significant extent. The regulatory protein by itself had no effect on either DNA polymerase alpha activity or the Km for template primer. These results indicate that deoxyribonucleoside triphosphate pools may be involved in the regulation of cellular DNA synthesis through a direct effect on DNA polymerization.

Animals↗
PubMed1978

Modulation versus rescue of antimetabolite toxicity by salvage metabolites administered by continuous infusion.

A system has been developed for the long-term continuous intravenous infusion of chemotherapeutic agents into unrestrained mice which allows new approaches to the toxicological and chemotherapeutic evaluation of antimetabolites. In mice, the concurrent infusion of thymidine and a source of preformed purine reversed both the toxicity and antitumor activity of MTX comparable to what was previously observed in cell culture. The infusion of thymidine alone, however, also blocked the toxicity of MTX without interfering with antitumor activity. A comparison of leucovorin rescue versus the utilization of thymidine plus preformed purine indicated that these salvage metabolites were as effective as leucovorin in reducing the toxicity of high-dose MTX while retaining antitumor activity.

Animals↗