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Biomedical subjects

E Estey

Publications and source records attributed to E Estey.

At least 181 records · Page 10Linked to original sources
PubMed1987

Effect of cell proliferation and chromatin conformation on intercalator-induced, protein-associated DNA cleavage in human brain tumor cells and human fibroblasts.

Antineoplastic intercalating agents such as 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) stabilize a cleavable complex between topoisomerase II and DNA. The production of protein-associated DNA cleavage in whole cells exposed to m-AMSA is thought to represent the cellular correlate of this topoisomerase II-mediated reaction. Protein-associated DNA cleavage can be quantified in mammalian cells by using alkaline elution technology. In an attempt to understand the impact of phenotypic and biochemical cellular characteristics on protein-associated DNA cleavage, we quantified m-AMSA-induced DNA cleavage in quiescent or proliferative normal human fibroblasts (cell strain 1508) and human glioblastoma cells (line T98G) as well as in asynchronously proliferating HeLa cells. The magnitude of DNA cleavage in quiescent fibroblasts and quiescent glioblastoma cells was identical and low relative to that observed in the HeLa cells. The magnitude of DNA cleavage was enhanced in both cell types following proliferation. This enhancement was greater in the glioblastoma cells than in the fibroblasts. These results were not due to alterations in cellular m-AMSA uptake. Chromatin was more elongated (open) in the quiescent glioblastoma cells than in the quiescent fibroblasts (as visualized by using the premature chromosome condensation assay), suggesting chromatin accessibility to drug per se may not be a critical determinant of the magnitude of m-AMSA-induced DNA cleavage. The onset of the enhanced m-AMSA-induced DNA cleavability that accompanied proliferation closely followed the formation of regions of localized chromatin decondensation, a late G1 event, and coincided with the onset of enhanced thymidine uptake, a marker for the onset of S phase. m-AMSA-induced cytotoxicity was also enhanced in proliferating compared with quiescent cells. The major finding of this study is that the cellular target for m-AMSA, putatively topoisomerase II, is more susceptible to drug action in proliferating cells than in quiescent cells. Effects of chromatin conformation or cellular phenotype upon topoisomerase II-mediated events such as m-AMSA-induced DNA cleavage are less certain.

Amsacrine↗
PubMed1987

Comparison of results of salvage therapy in adult acute myelogenous leukemia.

The results of initial salvage therapy for refractory and relapsed acute myelogenous leukemia for patients treated between 1973 and 1986 have been evaluated. There was no significant improvement in complete remission (CR) rate and survival in patients treated between 1973 and 1980, and the second group between 1981 and 1986. The remission duration was slightly longer in the second time period than in the initial time period. A number of factors were associated with the probability of achieving a CR. The major factors were the age of the patient, duration of the initial CR, liver function test abnormalities, and white blood cell count.

Adult↗
PubMed1987

Topoisomerase II as a target of antileukemic drugs.

The identification of topoisomerase II as a target of antineoplastic drug therapy is traced from the original observations by Ross et al. (1,2) in murine leukemia cells through studies with m-AMSA-resistant human leukemia cells. Recently developed quantitative biochemical assays of topoisomerase II activity and the susceptibility of topoisomerase II to the effects of m-AMSA have allowed the principles identified in murine and human leukemia cell culture systems to be applied to clinical material; a prospective trial is testing the utility of such assays for individualizing antineoplastic drug therapy.

Amsacrine↗
PubMed1987

Variables predicting response to high dose cytosine arabinoside therapy in patients with refractory acute leukemia.

The cytotoxic effect of cytosine arabinoside (ara-C) is presumably mediated by cytosine arabinoside 5'-triphosphate (ara-CTP). We tested for a correlation between intracellular ara-CTP pharmacokinetics and clinical response among 51 patients who received high dose ara-C (3 g/m2 at 12-hr intervals) as therapy for refractory acute leukemia. After accounting for pretreatment clinical variables that correlated with response, measurement of ara-CTP pharmacokinetics added significant prognostic information. This provides a rationale for manipulation of schedules of high dose ara-C administration in those patients whose pharmacokinetic characteristics are inconsistent with response to an every 12-hr schedule.

Acute Disease↗
PubMed1986

The production of topoisomerase II-mediated DNA cleavage in human leukemia cells predicts their susceptibility to 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA).

Protein-associated DNA cleavage is produced in mammalian cells treated with active antileukemic DNA intercalating agents such as 4'(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA). We have examined the ability of m-AMSA to produce DNA cleavage in 3 human myeloid leukemic cell lines with different sensitivities to the cytotoxic actions of m-AMSA to see if the magnitude of DNA cleavage correlated with the degree of m-AMSA sensitivity. DNA alkaline elution was used to quantify DNA cleavage. The amount of m-AMSA-induced DNA cleavage in the two lines sensitive to m-AMSA was 1-2 orders of magnitude greater than that in an m-AMSA-resistant leukemic line. The m-AMSA resistant line had been developed by prolonged exposure of one of the sensitive lines to m-AMSA. This finding was not secondary to a decreased uptake of m-AMSA in the resistant cell line. m-AMSA treatment of the nuclei isolated from the three lines produced DNA cleavage frequencies comparable to the cleavage frequencies produced by m-AMSA treatment of the whole cells from which the nuclei were isolated. The DNA cleaving ability stimulated by m-AMSA is thought to be mediated by drug-induced effects on topoisomerase II, a nuclear enzyme that mediates alterations in DNA conformation. Alterations in the manner in which this enzyme interacts with antineoplastic agents may explain the emergence of resistant cells following initially successful chemotherapy.

Aminoacridines↗
PubMed1986

Intercalator-induced, topoisomerase II-mediated DNA cleavage and its modification by antineoplastic antimetabolites.

Defining specific biochemical targets of active antineoplastic agents could aid in discovering better anticancer therapy and more thoroughly understanding the biochemical basis of malignancy. Through a series of cellular and biochemical studies, we and others have identified the nuclear enzyme topoisomerase II as the target of several active agents, including 4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA). The interference with topoisomerase II produced by m-AMSA can be quantified in whole cells exposed to m-AMSA by using the alkaline elution technique to measure DNA cleavage. Antimetabolites such as ara-C, hydroxyurea, and 5-azacytidine can augment m-AMSA-induced, topoisomerase II-mediated DNA cleavage and, concurrently, m-AMSA-induced cell killing. Studies in proliferating and quiescent human cells and an m-AMSA-sensitive/resistant human leukemia cell pair further support the hypothesis that a connection exists between topoisomerase II-mediated DNA cleavage and the mechanism by which m-AMSA kills cells. Pharmacologic or hormonal modification of specific biochemical processes critical to drug-induced cytotoxicity may enhance the therapeutic index of clinically useful agents.

Aminoacridines↗
PubMed1986

High-dose cytosine arabinoside: treatment and cellular pharmacology of chronic myelogenous leukemia blast crisis.

Twenty-one patients with chronic myelogenous leukemia (CML) in blastic transformation underwent 22 remission induction attempts with high-dose cytosine arabinoside (ara-C), administered as a two-hour infusion of 3 g/m2 for six to 12 doses. Ara-C doses were administered every 12 hours in 15 patients and every six to ten hours in six patients. Median patient age was 35 years (range, 20 to 62). The median duration of benign phase was 25 months (range, 0 to 167). Morphology of blast crisis blast cells was myeloid in 15 patients and lymphoid in six. Five patients achieved complete remission (CR), three had partial remission (PR), and one had hematologic improvement, for an overall response rate of 41%. Median remission duration was 2.5 months (range, 0.5 to 6 months). Survival duration was 6 months for responding patients and 1.5 months for those with resistant disease. The response rate was similar for patients with myeloid and lymphoid blast crisis (31% v 50%, respectively). The response rate was significantly higher for patients whose benign phase was less than 1 year (75% v 21%, P = .05) and who had prolonged marrow aplasia after ara-C (86% v 27%, P = .05). Myelosuppression was the major dose-limiting toxicity, and cerebellar toxicity occurred in two patients. Intracellular ara-C 5'-triphosphate (ara-CTP) levels were similar in blood and bone marrow leukemic cells and were slightly greater in the cells of responding patients compared to those with resistant disease. We conclude that high-dose ara-C is an effective regimen for CML blast crisis, resulting in a substantial response rate but modest remission duration. Its combination with other agents may further improve the prognosis of patients with this resistant disease.

Adult↗
PubMed1986

Therapeutic response in phase I trials of antineoplastic agents.

We analyzed the therapeutic effect reported in 187 phase I trials of 54 anticancer drugs introduced into National Cancer Institute-sponsored clinical trial from 1974 to 1982. An additional 12 drugs entering clinical trial prior to 1974 were also examined. Objective responses (partial and complete) were reported in 271 of the 6447 patients (4.2%). Thirty-nine percent of the patients were treated at an initial dose level greater than or equal to the dose ultimately recommended for phase II trials. Patients in phase I trials generally had adequate performance status (Karnofsky scale greater than 80% or Eastern Cooperative Oncology Group 0, 1, or 2). More than 90% of the patients had received prior chemotherapy. We next examined the therapeutic effect observed in phase II trials for each of the drugs. Thirty-eight of the 54 drugs had completed at least one phase II trial. Twenty-one drugs were rated active, and nine were rated inactive. For the drugs entering clinical trial since 1974, the median phase I response rate for those active in phase II was 4.3%, compared to 2.7% for the drugs not found active in phase II. This difference was not statistically significant. The tabulated response rate in phase I trials reported here should be interpreted cautiously. There are many factors which may contribute to significant variability in the reported response rates, including the heterogeneity of patient population with respect to prior therapy and tumor type, lack of requirement for measurable/evaluable disease on entry into many studies, and variations in the rigor with which tumor sites are followed for response. These factors may lead to either an overestimate or underestimate of the true response rate in phase I. Although little therapeutic effect is produced in phase I, we discuss several measures which might increase patient benefit during these trials.

Antineoplastic Agents↗
PubMed1985

Phase I evaluation of intravenous difluoromethylornithine--a polyamine inhibitor.

Difluoromethylornithine (DFMO), a non-competitive inhibitor of ornithine decarboxylase (ODC), the rate limiting enzyme of the polyamine synthetic pathway was evaluated in a Phase I trial. Intravenous DFMO was given to twenty patients with refractory leukemia by continuous infusion in doses from 5.5 to 64 g/m2. Toxicity clearly attributable to the drug was not severe and other than nausea and vomiting did not increase with dose. The previously reported ototoxicity which occurred with the oral form appeared to be less frequent. Loss of hearing which improved when the drug was stopped was seen in four patients, three of whom were simultaneously receiving aminoglycosides. Anorexia occurred in some patients at all doses. Vomiting, necessitating dosage reduction, was a significant problem at the highest dose administered. No patient achieved a remission but there was stabilization or decrease in circulating blast cells in several patients. This growth inhibition did not appear to be dosage related.

Acute Disease↗
PubMed1985

Pharmacologically directed ara-C therapy for refractory leukemia.

During a two-year experience treating patients with refractory acute leukemia with a fixed 12-hour schedule of high-dose ara-C, cellular ara-CTP pharmacodynamics were ascertained in circulating blasts of these patients. A strong correlation was found between achievement of complete remission and cellular ara-CTP levels. We therefore, attempted to improve the complete remission rate in patients with low ara-CTP levels by decreasing the intermittent ara-C dosing interval, thereby raising the minimum ara-CTP level in leukemic cells between doses. This initial attempt at pharmacologic direction of chemotherapy was successful in elevating minimum ara-CTP levels but did not produce an increase in response rate, probably because the total duration of ara-CTP exposure was decreased when the dose intervals were shortened. Currently we are engaged in a new approach based on the knowledge accumulated over the past three years. Patients receive a test ara-C dose from which data on ara-CTP cellular metabolism is derived, followed by a CI of ara-C at a dose calculated individually for each patient. Preliminary results of this approach thus far indicate an increased response rate and a different spectrum of toxicity than that observed with intermittent dose ara-C. Further clinical trials will determine the true effectiveness of this approach.

Arabinofuranosylcytosine Triphosphate↗
PubMed1984

Infection prophylaxis in acute leukemia. Comparative effectiveness of sulfamethoxazole and trimethoprim, ketoconazole, and a combination of the two.

In a comparative study of infection prophylaxis, patients with acute leukemia receiving remission induction therapy were assigned either no prophylaxis, sulfamethoxazole and trimethoprim, ketoconazole, or the combination of sulfamethoxazole and trimethoprim and ketoconazole. Both sulfamethoxazole and trimethoprim and the combination of sulfamethoxazole and trimethoprim and ketoconazole substantially reduced the overall incidence of infection consequent to a marked decrease in bacterial infection. However, sulfamethoxazole and trimethoprim were associated with an increased rate of fungal infection, while ketoconazole decreased this complication. No form of prophylaxis reduced infectious mortality or increased the complete remission rate. However, because of its effect in reducing infectious morbidity, we conclude that patients with acute leukemia receiving remission induction treatment should be given antibacterial and antifungal prophylaxis.

Acute Disease↗
PubMed1979

Lergotrile in Parkinson disease: further studies.

Lergotrile was administered to 53 patients with advanced Parkinson disease (PD), who had increasing disability despite optimal treatment with levodopa/carbidopa (Sinemet). Thirty-nine patients who could tolerate at least 20 mg per day lergotrile (thus considered "adequately treated") had significant descreases in rigidity, tremor, bradykinesia, gait disturbance, and total score without increased involuntary movements. Twenty-one of these 39 patients improved by at least one stage. Among the 39 patients, 23 had "on-off" effects, and in 13 of these the "on-off" effects decreased on lergotrile. The mean daily dose of lergotrile in adequately treated patients was 49 mg, permitting a 10 percent reduction in the dose of levodopa. Lergotrile was discontinued in 33 of the 53 patients because of adverse effects, including hepatotoxicity (11 patients), mental changes (12 patients) and orthostatic hypotension (8 patients). Although lergotrile, when added to levodopa, has a definite antiparkinsonian effect, the incidence of adverse effects, particularly hepatotoxicity, makes it unlikely that this ergot alkaloid will become widely available for the treatment of PD. Analogues of lergotrile have been synthesized, and it is hoped that they will duplicate the antiparkinsonian effect of this drug without its toxicity.

Aged↗
PubMed1979

Bromocriptine in Parkinson disease: further studies.

Bromocriptine was administered to 66 patients with advanced Parkinson disease (PD) and increasing disability despite optimal treatment with levodopa/carbidopa (Sinemet). Forty-five patients tolerated at least 25 mg per day of bromocriptine (the "adequately treated" group) in addition to Sinemet and had significantly decreased rigidity, tremor, bradykinesia, gait disturbance, and total score, but increased involuntary movements. Twenty-five of these 45 patients improved by at least one stage. Among the 45 patients, 27 had "on-off" effects, and in 19 the "on-off" effects decreased on bromocriptine. The mean dose of bromocriptine in adequately treated patients las 47 mg, permitting a 10 percent reduction in the dose of levodopa. Twelve adequately treated patients received bromocriptine for at least 1 year, and 8 continued for longer than this. Bromocriptine was discontinued in 29 of 66 patients because of adverse effects, including mental changes (14 patients) and involuntary movements (9 patients). All adverse effects were reversible. Despite adverse effects, expense, and scarcity, bromocriptine, when added to levodopa, is useful in patients with advanced disease who no longer respond satisfactorily to levodopa, and for whom no other treatment is available.

Adult↗
PubMed1978

Comparative effectiveness of two extracerebral DOPA decarboxylase inhibitors in Parkinson disease.

In four patients with Parkinson disease, we compared carbidopa combined with levodopa (Sinemet) and benserazide combined with levodopa (Madopar). All of these patients had responded to treatment, first with levodopa and then with Sinemet; after 6 years two continued to show a good response, while two developed marked "on-off" phenomena. Clinically, Sinemet and Madopar were similar; however, DOPA levels were higher, but with a shorter half-life, on Madopar. The higher DOPA levels may have been offset by the shorter half-life, resulting in no clinical change. DOPA levels were lower and half-life was shorter in patients with on-off phenomena. These differences may be responsible in part for the on-off phenomena.

Aromatic Amino Acid Decarboxylase Inhibitors↗
PubMed1977

Treatment of Parkinson's disease with lergotrile mesylate.

Lergotrile mesylate, an ergot alkaloid derivative and putative dopamine agonist, was effective in the majority of patients with Parkinson's disease who were showing signs of disease progression despite treatment with levodopa combined with a peripheral decarboxylase inhibitor (carbidopa). Among 20 patients completing a six-month trial, there was a significant (P less than .01) reduction in rigidity, tremor, bradykinesia, gait disturbance, and total score when lergotrile was added to levodopa plus carbidopa. Mean daily dose of lergotrile mesylate was 52 mg, and the mean daily dose of levodopa was reduced by 15%. Abnormal involuntary movements were decreased on addition of lergotrile and reduction in levodopa while mental changes and orthostatic hypotension were increased. Elevations in serum transaminase levels were noted in three patients. The ergot alkaloids promise to be an important new class of antiparkinsonian drugs.

Acetonitriles↗