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Biomedical subjects

R L Capizzi

Publications and source records attributed to R L Capizzi.

At least 37 records · Page 2Linked to original sources
PubMed1994

Methotrexate content in squamous cell carcinoma of the head and neck after low-dose methotrexate.

Eleven patients with squamous carcinoma of the head and neck who were scheduled for surgical resection or endoscopic biopsy of tumor received 15 mg/m2 of methotrexate (MTX). Samples of tumor, normal mucosa, and plasma were obtained at surgery or endoscopy, 18-24 hours after the last MTX dose. Tissue content and plasma concentration of MTX and folate were measured using sequential radioligand-binding assays. Median MTX content was 50.0 pmol/g wet weight in tumor, 19.0 in normal mucosa, and < 0.5 nM (pmol/ml) in plasma. Since dihydrofolate reductase (DHFR) content of human tumors has previously been shown to be less than 5 pmol enzyme/g wet weight, tumor MTX content exceeded expected DHFR content in all but one patient. These data support the concept that low doses of MTX saturate tumor DHFR and that, in this regard, dose escalation may have limited value.

Administration, Oral↗
PubMed1994

Protection of normal tissues from the cytotoxic effects of chemotherapy by amifostine (Ethyol): clinical experiences.

The rationale for the clinical trials with amifostine (Ethyol, US Bioscience, Inc, West Conshohocken, PA) is based on an extensive body of preclinical data coming from many laboratories around the world. Initial clinical trials centered on the hematotoxicity produced by cyclophosphamide, carboplatin, and cisplatin; hematotoxicities and mucosal toxicities from radiation therapy; and nephrotoxicity, neurotoxicity, and ototoxicity from cisplatin.

Amifostine↗
PubMed1993

Amifostine-mediated protection of normal bone marrow from cytotoxic chemotherapy.

Amifostine (US Bioscience, West Conshohocken, PA; Ethyol, WR-2721), a phosphorylated thiol developed by the United States Army as a protective agent for military personnel in the event of nuclear warfare, has shown protection of normal tissues from the cytotoxic effects of therapeutic radiation and chemotherapy with preservation of cytotoxic effects on the tumor. The basis of this selective protection derives from the relatively rapid uptake and anabolism of Amifostine into normal tissues and minimal, slower uptake into tumor tissue. Preclinical investigations have demonstrated protection of bone marrow stem cells from the toxic effects of radiation and chemotherapy. Several controlled clinical trials demonstrated this hematoprotective effect. In patients given 1.5 g/m2 cyclophosphamide and month later given Amifostine (740 mg/m2) followed by the same dose of cyclophosphamide, the median nadir neutrophil count was significantly increased and duration of neutropenia was significantly reduced by pretreatment with Amifostine. In women with stage III/IV ovarian cancer treated with 1 g/m2 cyclophosphamide and 100 mg/m2 cisplatin +/- Amifostine 910 mg/m2, treatment with Amifostine before cyclophosphamide and cisplatin resulted in a significant decrease in both the incidence and duration of hospital stays for neutropenic fever compared to cyclophosphamide and cisplatin alone. There were equivalent rates of response and duration of survival in both groups. Other studies have shown Amifostine protects bone marrow purged in vitro with 4-hydroperoxycyclophosphamide before autologous bone marrow transplantation. This preservation of marrow stem cells resulted in a statistically significant decrease in time to marrow engraftment, need for platelet transfusions and antibiotics, and duration of hospital stay. Amifostine-mediated protection of normal bone marrow illustrated in preclinical experiments is also evident in clinical trials. Amifostine preserves trilineage stem cells (red blood cells, platelets, and white blood cells) in contrast to the lineage-specific effects of the colony-stimulating factors. Theoretically, Amifostine and the colony-stimulating factors should provide complementary benefits to bone marrow recovery and function after cytotoxic therapies. These observations offer the promise of using high doses of chemotherapy to exploit antitumor, dose-response relationships in clinical trials.

Amifostine↗
PubMed1993

Purification and characterization of deoxycytidine kinase from acute myeloid leukemia cell mitochondria.

Deoxycytidine kinase is a key anabolic enzyme for the activation of ara-C and other antitumor drugs, as well as normal purine and pyrimidine deoxynucleotides. Previously, two forms of the kinase have been identified; deoxycytidine kinase I (70 kDa) and deoxycytidine kinase II (70 kDa). Deoxycytidine kinase I utilized dCyd and ara-C as substrates, while deoxycytidine kinase II used dCyd and dThd as substrates. Deoxycytidine kinase kinase II had very low activity on ara-C as a substrate. We report a procedure for the purification of a novel deoxycytidine kinase (52 kDa) from isolated human peripheral blood leukemia cell mitochondria. This enzyme has activity similar to deoxycytidine kinase II. The enzyme was extracted from the mitochondria with digitonin (1 mg/8 mg protein) and 0.3 M NaCl, and the extract was purified by DEAE-cellulose chromatography and thymidine-Sepharose affinity chromatography. This procedure produced a near homogeneous enzyme preparation with a yield of 70%. The mitochondrial deoxycytidine kinase was localized to the outer mitochondrial membrane. The enzyme phosphorylated dCyd (Km = 17 microM), however, ara-C was not a good substrate for the mitochondrial deoxycytidine kinase. ATP was the best phosphate donor, whereas dCTP and dTTP were potent inhibitors of mitochondrial deoxycytidine kinase. In contrast, phosphorylation of ara-C by deoxycytidine kinase I utilized GTP, dGTP, or ATP as a phosphate donor.

Chromatography, Affinity↗
PubMed1992

1-beta-D-arabinofuranosylcytosine-diphosphate-choline is formed by the reversal of cholinephosphotransferase and not via cytidylyltransferase.

In an effort to identify the pathway leading to the formation of 1-beta-D-arabinofuranosylcytosine-diphosphate (ara-CDP)-choline from 1-beta-D-arabinofuranosylcytosine (ara-C) treatment of cultured cells, as well as of cells obtained from leukemia patients, we probed the enzymatic steps involved in the CDP-choline pathway for phosphatidylcholine biosynthesis. Ara-C-triphosphate was not a substrate for CTP:phosphocholine cytidylyltransferase activity under the conditions employed, whereas CTP and dCTP were utilized to form CDP-choline and dCDP-choline, respectively. When presented together, ara-C-triphosphate and CTP inhibited the enzymatic conversion of CTP to CDP-choline in the presence of phosphocholine, with a Ki of 6 mM. Since CTP:phosphocholine cytidylyltransferase did not appear to be responsible for the increased levels of ara-CDP-choline, we next studied the other enzyme in the pathway for phosphatidylcholine synthesis that could form ara-CDP-choline, CDP-choline:1,2-diacylglycerol cholinephosphotransferase. CDP-choline:1,2-diacylglycerol cholinephosphotransferase activity present in microsomes isolated from L5178Y murine leukemia cells exhibited a reversal of its normal catalytic activity, using CMP and 1-beta-D-arabinofuranosylcytosine-monophosphate (ara-CMP) along with phosphatidylcholine to produce either CDP-choline or ara-CDP-choline, plus diradylglycerol. The Vmax and Km values for CMP were 0.78 +/- 0.04 nmol/min/mg and 340 +/- 20 microM, respectively, whereas the Vmax and Km for ara-CMP were 0.22 +/- 0.06 nmol/min/mg and 1410 +/- 540 microM, respectively. A Ki value of 3 mM was obtained for ara-CMP under the cell-free assay conditions used. These results indicate that ara-CDP-choline most likely arises from a reversal of the CDP-choline:1,2-diacylglycerol cholinephosphotransferase utilizing ara-CMP, rather than from the catalysis of ara-C-triphosphate plus phosphocholine to ara-CDP-choline by CTP:phosphocholine cytidylyltransferase. It is speculated that this mechanism may explain, in part, the rapid cellular lysis observed with high dose ara-C therapy.

Animals↗
PubMed1992

Deoxypyrimidine-induced inhibition of the cytokinetic effects of 1-beta-D-arabinofuranosyluracil.

Ara-U-induced S-phase accumulation and the interaction between high concentrations of ara-U (HiCAU) and ara-C were investigated in L1210 leukemia cells in vitro. Treatment of exponentially growing L1210 murine leukemia cells with ara-U (200-1000 microM) for 48 h caused a dose-dependent accumulation of cells in the S-phase. The extent of this ara-U-induced S-phase accumulation correlated with ara-U incorporation into DNA and with increases of up to 172% and 464% in the specific activities of deoxycytidine kinase and thymidine kinase, respectively, over control values. Metabolism of 1 microM ara-C following the exposure of cells to ara-U (1 mM) resulted in 4.5 pmol araC DNA/mg protein vs 2.1 pmol/mg protein in control cells. Although 48-h exposure of cells to 200 and 400 microM ara-U is not cytotoxic, it enhances the cytotoxicity of ara-C (10-100 microM) 4- to 10-fold. Ara-U-induced S-phase accumulation is inhibited by deoxypyrimidine nucleosides but not by pyrimidine or deoxypurine nucleosides. Some of the ara-U and ara-C concentrations used in this study are achievable in clinical practice, and ara-U/ara-C interactions may explain in part the unique therapeutic utility of high-dose ara-C.

Animals↗
PubMed1992

Modulation of the cellular pharmacokinetics of ara-CTP in human leukemic blasts by dipyridamole.

The effect of dipyridamole (DP) on the cellular retention of 1-beta-D-arabinofuranosylcytosine (ara-C) and its metabolites was examined in leukemic blasts that had been isolated directly from bone marrow aspirates from patients afflicted with acute myeloid leukemia (AML). When AML cells were loaded for 2 h with 1 microM [3H]-ara-C and then transferred to ara-C-free medium, total intracellular concentrations of radiolabel and [3H]-ara-C 5'-triphosphate [3H]-ara-C-CTP rapidly declined. After 8 h, total intracellular levels of tritium were 4.4 times higher if 10 microM was included in the washout medium; however, the majority of this intracellular radiolabel corresponded to [3H]-uridine arabinoside ([3H]-ara-U) and [3H]-ara-C. DP significantly increased the mean t1/2 for [3H]-ara-CTP from 102 to 136 min (P less than 0.01), but this effect was much less pronounced than that obtained for total tritium and the increase was quite variable (0-70%; median, 19%). The presence of DP in the washout medium also increased the incorporation of ara-C into DNA and the formation of ara-CDP-choline. The level of ara-CDP-choline continued to increase in both DP-containing and DP-free media for the first 4 h following drug removal and the formation of ara-CDP-choline continued during the first few hours in ara-C-free medium. At the end of the 8-h wash in DP-containing medium, the cellular concentration of ara-CDP-choline was equivalent to that found at the beginning of the washout period. Although statistically significant, the effect of DP on ara-CTP retention in AML blasts was much less pronounced than that previously observed in L5178Y leukemia. The former cells exhibited only 10% as many nucleoside transport carriers as did the L5178Y cells as measured by their capacity to bind [3H]-nitrobenzylmercaptopurine riboside (NBMPR). The effect of DP in prolonging ara-CTP retention was proportional to the number of [3H]-NBMPR binding sites. This suggests that in patients cells that exhibit extremely low transport capacity, most of the net catabolism occurs via deamination, and further inhibition of transport by DP in an effort to improve cellular retention of ara-C has little effect on ara-CTP catabolism.

Biological Transport↗
PubMed1992

Rapid intravenous infusion of amphotericin B: a pilot study.

PURPOSE: The administration of amphotericin B in the conventional prolonged infusion over 4 to 6 hours is complicated by the acute toxicities of fevers and chills in 50% to 90% of patients and the chronic toxicities of increased creatinine levels and hypokalemia in 60% to 80% of patients. To determine the safety and toxicity of rapid infusions, we conducted a prospective, nonrandomized study in patients with clinical indications for antifungal therapy. PATIENTS AND METHODS: Twenty-five granulocytopenic adults with acute leukemia and myelodysplastic syndromes were enrolled in a phase I trial using four sequentially shorter infusion durations: a standard infusion over 4 hours (n = 3) and shortened infusion durations at 3 hours (n = 3), 2 hours (n = 4), and 1 hour (n = 15). Toxicity was assessed by daily examinations of study subjects by one of the study investigators, by documentation of all infusion-related fevers and chills, and by daily monitoring of serum levels of creatinine, potassium, magnesium, and aspartate aminotransferase. RESULTS: Temperatures greater than 38 degrees C occurred in 16 of 25 (64%) patients, but only two had temperatures exceeding 40 degrees C. Chills were observed in 13 of 25 (56%) patients, but only one had severe symptoms. Serum creatinine increased more than 0.5 mg/dL (44.20 mumol/L) above the pretreatment baseline in 17 of 25 (68%) patients, and the absolute creatinine level was greater than or equal to 2.0 mg/dL (176.8 mumol/L) in 10 of 25 (40%) patients. Serum potassium levels dropped below the normal limit of 3.5 mEq/L (3.5 mmol/L) in all patients, but no patient had potassium levels below 2.5 mEq/L (2.5 mmol/L). Intravenous potassium supplementation was administered to all patients and exceeded 100 mEq/d in 12 of 25 (48%) patients. CONCLUSIONS: Rapid infusions of amphotericin B are safe, are associated with similar toxicity as prolonged infusions, and facilitate inpatient care by decreasing nursing time needed for administration and minimizing scheduling conflicts with other necessary intravenous medications. Shorter infusions also facilitate outpatient and home administration of amphotericin B.

Aged↗
PubMed1991

Interrupted versus continuous chemotherapy in patients with metastatic breast cancer. The Piedmont Oncology Association.

BACKGROUND: Chemotherapy for metastatic breast cancer is palliative, and the optimal duration of therapy is unknown. We designed a trial to determine whether continuous treatment is superior to stopping treatment after a brief induction period and resuming treatment when the disease progresses. METHODS: We treated 250 women with metastatic breast cancer with six courses of cyclophosphamide, doxorubicin, and fluorouracil given every three weeks. At the completion of this induction period, women whose disease either regressed or remained stable were randomly assigned to receive either continued treatment with cyclophosphamide, methotrexate, and fluorouracil (maintenance therapy) or no further treatment (observation) followed by treatment with cyclophosphamide, methotrexate, and fluorouracil when disease progression became evident (reinduction). RESULTS: The combined rate of complete and partial responses after initial therapy was 30 percent (71 of 233 patients who could be evaluated; 95 percent confidence interval, 25 percent to 37 percent). In another 42 percent (98 patients), the disease remained stable. A total of 145 patients were randomized. Seventy-one were randomly assigned to the maintenance-therapy group, and 74 to the observation group. The median time to progression was 9.4 months for patients in the maintenance-therapy group and 3.2 months for patients in the observation group (P less than 0.001). After reinduction therapy, the median time to progression was 3.5 months. The median length of survival from the time of initial therapy was 14.8 months for all 250 patients; it was 21.1 months for the 71 patients in the maintenance-therapy group and 19.6 months for the 74 patients in the observation group (P = 0.67). Maintenance therapy was the most important determinant of the time before progression (P less than 0.001), but it was not associated with prolonged survival. The changes in performance status were similar in the patients in both groups, but nausea, vomiting, and mucositis were significantly more frequent in the maintenance-therapy group. CONCLUSIONS: In patients with breast cancer who received induction chemotherapy for 18 weeks, subsequent continuous chemotherapy was associated with a significant prolongation of the time before progression as compared with those receiving no further therapy; overall survival, however, was not significantly different in the two groups.

Adult↗
PubMed1991

A critical role for uridine nucleotides in the regulation of deoxycytidine kinase and the concentration dependence of 1-beta-D-arabinofuranosylcytosine phosphorylation in human leukemia cells.

The intracellular concentration of 1-beta-D-arabinofuranosylcytosine (ara-C) for half-maximal phosphorylation by leukemic blasts obtained directly from patients was 2.1 +/- 2.5 microM (median, 1.3 microM, N = 25), and the rate of ara-C accumulation actually declined at concentrations above 20 microM in 35% of these cell populations. These apparent Km values for cellular phosphorylation were an order of magnitude lower than the Km of deoxycytidine (dCyd) kinase for ara-C with ATP as phosphate donor. dCyd kinase was purified from human leukemia cells and assayed for [3H]ara-C kinase activity with a mixture of 7 nucleotides at their approximate cellular concentrations or with a single nucleotide deleted. At low or high ara-C concentrations, ATP, GTP, CTP, or dTTP could be eliminated without significantly altering the rate. The only potential phosphate donor that was clearly important was UTP, since its deletion reduced the rate to only 25% of that with the complete mix. As anticipated, eliminating dCTP, the end product of this salvage pathway, moderately increased the rate by 50% at 0.4 microM ara-C or by 26% at 40 microM ara-C. At 40 microM ara-C, deleting UDP from the mix increased the rate more than deleting dCTP. dCTP was less inhibitory against 1 mM UTP (50% inhibitory concentration, 26 microM) than against 4 mM ATP (50% inhibitory concentration, 2.2 microM). In kinetic assays with 4 mM ATP and variable ara-C, UDP was a potent uncompetitive inhibitor with a Ki of 4 microM; the Ki for ADP was 1000-fold higher. Direct fit of kinetic data to the Michaelis equation yielded a Km for ara-C of 49 microM with 4 mM ATP as the phosphate donor; however, there was evidence of negative cooperativity with a Hill coefficient of 0.7. High ara-C Km values were also obtained with GTP and CTP, but with no evidence of cooperativity. With 1 mM UTP, the Km was 1.5 microM with moderate substrate inhibition; thus the kinetic data with UTP were similar to those for ara-C phosphorylation by intact cells. UDP was less potent versus UTP than versus ATP. It lowered the Vmax and enhanced the ara-C substrate inhibition without altering the Km. When 1 mM UTP and 4 mM ATP were mixed, the kinetic pattern was similar to that for UTP alone. The Km for UTP with [3H]dCyd as the phosphate acceptor of 0.8 microM was 25-fold lower than the Km for ATP of 20 microM.(ABSTRACT TRUNCATED AT 400 WORDS)

Blast Crisis↗
PubMed1991

Antimetabolites.

Explore the source record for details and available documents.

Antimetabolites, Antineoplastic↗
PubMed1991

The influence of drug interval on the effect of methotrexate and fluorouracil in the treatment of advanced colorectal cancer.

The importance of the interval between methotrexate (MTX) and fluorouracil (5-FU) was studied in 168 patients with previously untreated, measurable, advanced colorectal cancer. They were randomized to receive MTX 200 mg/m2, followed by 5-FU 600 mg/m2 either 24 hours (arm A) or 1 hour (arm B) after MTX. All patients received leucovorin (LV) 24 hours after MTX, 10 mg/m2 orally every 6 hours for six doses. The regimen was repeated every 2 weeks, with 5-FU escalation as tolerated. Arm A was significantly better than arm B with respect to overall response rate (29% v 14.5%, P = .026), time to progression (TTP; median, 9.9 months v 5.9 months, P = .009), and survival (median, 15.3 months v 11.4 months, P = .003). Significant differences between arms were not found in response rate, median TTP, or median survival for the subgroup of patients with rectal primaries who comprised 20% of the patients in each arm. Significant factors prognostic for survival were performance status and number of metastases, as well as treatment. Age did not influence survival. Toxicity was similar in both arms and was primarily gastrointestinal. More mucositis was seen in arm A. There were four toxic deaths secondary to neutropenia and infection (one from arm A and three from arm B) and three other deaths (two from arm A and one from arm B) that were possibly drug-related. The combination of MTX with LV rescue and 5-FU is an active regimen in advanced colorectal cancer; its efficacy is increased in colon, but not rectal cancer, when the interval between MTX and 5-FU is long (24 hours) rather than short (1 hour).

Aged↗
PubMed1991

Leukapheresis induced changes in cell cycle distribution and nucleoside transporters in patients with untreated acute myeloid leukemia.

Bone marrow leukemia cells from eight adults with untreated acute myeloid leukemia (AML) were evaluated before and after three daily leukaphereses to determine if mechanical cytoreduction can modulate the cell cycle distribution. The percentage of cells in S-phase and the proliferative fraction (PF = %S + %G2M) were determined by flow cytometry after dual labeling with bromodeoxyuridine and propidium iodide. Prior to pheresis the median %S and PF were 5.4 and 15.4%, respectively. The median change in %S was +2.5% (range -5.5 to +18.8) with increases greater than or equal to 3.7% in 4/8 patients. The median change in PF was +6.1% (range -13.8 to +25.3) with an increase of greater than or equal to 3.6% in 6/8 patients. The median absolute changes of 2.5 and 6.1% represent increases of 47% for %S and 40% for PF compared to the day 1 (pre-pheresis) median values. As the number of nucleoside transporters in the cell membrane [nitrobenzylmercaptopurine riboside (NBMPR) binding sites] has been related to the percentage of cells in S-phase and to cytosine arabinoside (ara-C) cellular pharmacology, these were also measured before and after leukapheresis. Changes in the number of NBMPR binding sites varied widely with a median increase of 365 sites per cell (range -26,061 to +10,396). The change in NBMPR sites was significantly and positively correlated with changes in %S (r = 0.829, p = 0.042). These data suggest that mechanical cytoreduction by leukapheresis can increase the fraction of leukemia cells in S-phase and the PF in some patients with AML. The increase in %S is accompanied by an increase in NBMPR binding sites per cell. These changes in leukemia cell characteristics would be expected to result in an increase in efficacy of ara-C or other S-phase specific agents.

Binding Sites↗
PubMed1991

Effect of dose on the pharmacokinetic and pharmacodynamic effects of cytarabine.

In summary, there are compelling laboratory and clinical data indicating that higher doses of ara-C than are currently used in SDaC protocols constitute optimal therapy. The cellular pharmacokinetics of ara-C are optimized at extracellular drug concentrations in the 10 to 15 mumol/L range. At these concentrations, transport rates are no longer rate-limiting, and ara-C phosphorylation capacity is saturated. The prime determinants of ara-C effect then shift to multiple intracellular events including anabolism to nucleotides, catabolism via deamination by Cyd-dCyd deaminase and dCMP deaminase, half-life of ara-CTP, the extent of incorporation into DNA, and the half-life of ara-CMP residues in DNA. It is postulated that at these high doses an additional effect of ara-C occurs on the cell membrane through affects on membrane phospholipid synthesis. This effect may contribute to the brisk cell lysis associated with HiDaC treatment. When administered as repetitive doses of 3 g/m2 over a 1- to 3-hour period, systemic deamination of ara-C gives rise to high plasma concentrations of ara-U. This metabolite has a long plasma half-life and, at least in the mouse, is concentrated in the liver and kidneys. High concentrations in these organs retard the further catabolism of ara-C and thus increase the systemic AUC providing a longer exposure period to the drug. A similar mechanism may obtain in patients treated with HiDaC. The observed decreased clearance of ara-C when administered in gram versus milligram doses and the long-terminal gamma-phase in plasma clearance of the drug associated with HiDaC usage quite probably reflects this effect of ara-U in patients. Additionally, by some as yet unknown mechanism, high concentrations of ara-U cause accumulation of leukemia cells in S-phase, the phase of the cell cycle wherein ara-C is maximally effective. This effect of ara-U may add to the cytokinetic effects initiated by rapid cytoreduction, which summate in the observed enhancement of the proliferative fraction of residual leukemia cells on day 8. The effect of a second course of therapy at this time is thereby enhanced. These dose-related and metabolite-drug interactions that occur when ara-C is given at high doses constitute a means for "self-potentiation" and may thus contribute to its overall therapeutic efficacy.

Animals↗
PubMed1991

S-phase fraction is not correlated with nucleoside transport in acute myeloid leukemia cells.

The expression of nucleoside carrier [nitrobenzylmercaptopurine riboside (NBMPR) binding] sites has been related to proliferative fraction in cell lines and in patient myeloid and lymphoid blasts. This correlation was examined in patients with untreated acute myeloid leukemia (AML). Bone marrow blasts were incubated with 8 microM bromodeoxyuridine (BrdUrd) and dual-labeled with propidium iodide and anti-BrdUrd monoclonal antibody. Flow cytometry was used to determine the percentage of cells with detectable BrdUrd incorporation into DNA (%S) and the proliferative fraction (PF = %S+%G2M) in 63 patients; NBMPR binding sites were quantitated in samples from 29 patients. The median %S was 6.1% (range 0.6-25.9%) and the median PF was 13.0% (range 2.4-36.1%), with a median of 7243 NBMPR binding sites per cell (range 1716-27247). In contrast to a previous report which included bone marrow and peripheral blood blasts, %S in marrow blasts did not correlate with NBMPR binding sites per cell (r = 0.005, p = 0.979). Similarly, PF did not correlate with NBMPR sites per cell (r = 0.190, p = 0.325). This lack of correlation between leukemia cell proliferation and NBMPR binding sites per cell suggests that DNA synthesis in AML blasts depends primarily on de novo nucleoside synthesis rather than the usage of salvage pathways.

Adult↗