Hans M. C. Wessels

Detection of point mutations in DNA using capillary electrophoresis in a polymer network

The use of capillary electrophoresis (CE) in a polymer network for single-strand conformation polymorphism (SSCP) is investigated. SSCP is a method to detect DNA point mutations, essential in the diagnosis of several diseases. The PCR (polymerase chain reaction) amplified p53 gene, a tumour suppressor gene known to be frequently mutated in malignant cells, was subjected to CE analysis. Two single-strand DNA fragments of 372 bp in length differing in only one nucleotide could be separated. We conclude that SSCP using CE in a polymer network is a powerful method for the detection of point mutations in DNA sequences.

Cellular and plasma adriamycin concentrations in long-term infusion therapy of leukemia patients

SummaryTo determine whether long-term adriamycin (ADM) infusions resulted in cellular ADM concentrations at least comparable to those observed after bolus injections, ADM cellular and plasma concentrations were measured in 18 patients with leukemia. ADM was administered at 30 mg/m2 per day for 3 days, either as bolus injections or as 4-, 8-, or 72-h infusions. Negligible accumulation of plasma ADM was observed. Peak plasma ADM concentrations after bolus injections were 1640±470 ng/ml (n=7). Maximum levels were 176±34 ng/ml during 4-h infusion (n=5); 85±50 ng/ml during 8-h infusion (n=4); and 47±5 ng/ml (n=2) after 72-h infusion. ADM concentrations in nucleated blood and bone marrow cells correlated well (r=0.82, n=47). ADM accumulated in leukemic cells up to 30–100 times the plasma concentrations. The shorter the administration time-span, the higher the peak leukemic cell concentration and the greater the loss of drug immediately after the end of the administration. The final cellular ADM half-life was approximately 85–110 h. After long-term infusion and bolus injection of the same dose, similar areas under the curve for plasma or leukemic blast cell ADM concentrations were attained. Since comparable therapeutic efficacy was observed in all regimens, the antileukemic effect appeared not to be related to the peak plasma concentrations, while acute toxicity phenomena decreased with increasing duration of the infusion. Long-term ADM infusion deserves more attention in the treatment of patients with anthracyclines.

Bone marrow repopulation capacity after transplantation of lymphocyte-depleted allogeneic bone marrow using counterflow centrifugation.

Bone marrow from six allogeneic HLA-matched and MCL nonreactive siblings was fractionated by means of isopycnic flotation centrifugation and subsequent counterflow centrifugation. The low density fraction (d ≦ 1.070 g/ml) obtained by IFC contained 20% of the nucleated cells and more than 90% of the myeloid and erythroid progenitors. The putative stem cell fraction obtained by CC showed a satisfactory recovery (88%) of the CFU-GM and BFU-E and only 3.5% of the original number of T lymphocytes. Bone marrow repopulation capacity was not impaired in comparison with a comparable group of patients. Despite the average high age of this group (29.6 years), only one of the four evaluable patients developed graft-versus-host disease.

Leukemic cell and plasma daunomycin concentrations after bolus injection and 72 h infusion

SummaryThe effect of the duration of daunomycin (DNM) infusion on leukemic cell drug concentrations was evaluated. Cellular and plasma DNM concentrations were measured in 20 patients with acute non-lymphocytic leukemia. DNM 45 mg/m2 was administered either as a bolus injection or as a 4-, 8- or 72-h constant-rate infusion during 3 consecutive days. Peak plasma DNM levels amounted to 227±116 ng/ml after bolus injection and were only 16±6 ng/ml after 72-h DNM infusions. Terminal plasma DNM half-lives were 14±4 h. Peak leukemic cell DNM concentrations at the 3rd day of administration were 16810±2580 ng/109 cells (bolus injections) and 10310±5510 ng/109 cells (72-h infusions). The areas under the cellular curve were similar and independent of the duration of the DNM infusion. Peak leukemic cell daunomycinol (DNMol) concentrations were respectively 3500 ± 1600 ng/109 cells and 2850±1720 ng/109 cells. Cellular DNM terminal half-life was 13±4 h. DNM concentrations in nucleated blood and bone marrow cells correlated well (r=0.93, n=26). Long-term infusion produced less severe side effects. Therapeutic efficacy was maintained during long-term infusion.

Plasma and human leukemic cell pharmacokinetics of oral and intravenous 4‐demethoxydaunomycin

On 3 consecutive days, 4‐demethoxydaunomycin (D‐DNM) was administered orally (30 mg/m2) as bolus injection and 4‐ or 24‐hour infusion to seven patients with acute leukemia. Cellular (nucleated blood and bone marrow cells) and plasma drug concentrations were studied. After bolus injection, peak plasma D‐DNM concentrations were about 50 mg/ml. D‐DNM plasma t½s were 0.4 ± 0.3 hours (T½α) and 16.4 ± 4.7 hours (T½β). D‐DNM concentrations in nucleated blood and bone marrow cells were on the same order of magnitude and amounted to more than 400 times the plasma concentration, whereas 4‐demethoxydaunomycinol (D‐DNMol) concentrations were about 200 times higher. Cellular D‐DNM concentrations were maximal at the end of intravenous dosing and at 2 to 4 hours after D‐DNM ingestion. D‐DNMol concentrations increased more slowly and accumulated on subsequent treatment days in cells and plasma; D‐DNM and D‐DNMol cellular t½ times were 42 and 72 hours, respectively. Antileukemic activity was observed.

In vivo cellular adriamycin concentrations related to growth inhibition of normal and leukemic human bone marrow cells.

Inhibition of clonogenicity of normal and leukemic human hematopoietic progenitor cells was studied after in vivo and in vitro exposure of bone marrow to adriamycin (ADM). Flow cytometric determination of cellular ADM concentrations in blast cells, expressed in fluorescence units/cell (FU/cell), correlated well with the extent of cytotoxicity. After 2 h in vitro exposure to 500 ng ADM/ml, the ADM concentration of leukemic (n = 7) and normal (n = 4) bone marrow blast cells amounted to 231 +/- 180 and 249 +/- 53 FU/cell respectively, producing moderate decreases in clonogenicity by 44 +/- 30 and 54 +/- 27%. Exposure to 2000 ng/ml produced ADM concentrations of 1184 +/- 472 FU/cell for leukemic blast cells and 1024 +/- 281 FU/cell for normal blast cells. Inhibition of clonogenicity was 96 +/- 7% in leukemic blasts and 99 +/- 1% in normal blasts. In vivo ADM concentrations in leukemic blast cells at 1-2 h after administration were 216 +/- 98 FU/cell (n = 8 patients). This implies that inhibition of clonogenicity after administration of conventional dosages of ADM will be approx. 60-70% for both leukemic and normal bone marrow progenitor cells. Such values were noted in four patients of whom bone marrow was cultured, which was obtained shortly after ADM monotherapy.

Determination of 1-β-d-arabinofuranosylcytosine and 1-β-d-arabinofuranosyluracil in human plasma by high-performance liquid chromatography

Abstract A method is described for the determination of 1-β- d -arabinofuranosylcytosine (Ara-C) and its metabolite 1-β- d -arabinofuranosyluracil (Ara-U) in human plasma. After deproteinization of the plasma sample, separation is performed by reversed-phase liquid chromatography. For Ara-C concentrations exceeding 0.05 mg/l and for Ara-U concentrations exceeding 1 mg/l, injection volumes of 100 μl are applied. For lower concentrations an injection volume of 500 μl is used. Ara-C is detected at 280 nm with a lowest detection limit of 0.002 mg/l in plasma. Ara-U is detected at 264 nm with a lowest detection limit varying from 0.01 to 0.1 mg/l in plasma. This variation is caused by an unknown substance with the same elution properties as Ara-U and which appears to be present in plasma in variable concentrations. The coefficient of variation of the whole procedure is about 6% for Ara-C concentrations above 0.005 mg/l and for Ara-U concentrations above 0.1 mg/l. For lower concentrations the coefficient of variation is about 14%.

The influence of splenectomy on the in vitro lymphocyte response to phytohemagglutinin and pokeweed mitogen in Hodgkin's disease

Using tissue culture techniques, the 14C‐thymidine incorporation of peripheral lymphocytes in 17 Hodgkins patients was tested before and after splenectomy under stimulation with phytohemagglutinin and pokeweed. Incorporation under phytohemagglutinin stimulation about 10 days after splenectomy was not affected in Hodgkins patients with pathologic Stages I and II, but was significantly (p < 0.005) increased in those with Stages III and IV. The total PHA stimulation potency, i.e. the product of the lymphocyte count and PHA stimulation, increased slightly in both groups. Incorporation under pokeweed stimulation after splenectomy did not significantly differ from that before the operation in the two groups. Although the number of cases studied is rather small, it is concluded that splenectomy causes no demonstrable untoward effect on the cellular immunologic potency. The immunologic state is more likely to be favorably influenced than unfavorably.

Proliferation patterns in acute myeloid leukemia: leukemic clonogenic growth and in vivo cell cycle kinetics

SummaryIn a prospective study of 33 newly diagnosed patients with acute myeloid leukemia (AML), we analyzed the relationship of proliferation parameters with clinical parameters, response to induction therapy, and survival. The median follow-up was 26 months. The proliferative capacity of the leukemic progenitor cells was studied using colony-forming assays (number of colonyforming units, growth pattern, and spontaneous clonogenic growth capacity). The cell kinetic parameters of the bone marrow blasts were determined by in vivo labeling with iododeoxyuridine and subsequent flow cytometry: labeling index (LI), DNA synthesis time (Ts), potential doubling time. No or only weak relationships were observed between the experimental and clinical parameters such as age, sex, % blasts, white blood cell count, FAB subtype, cytogenetics, and % CD 34+ cells. This suggests that clonogenic growth and cell cycle kinetics of bone marrow blasts are independent cell biologic properties of AML. No association between the proliferation parameters and induction response rate was noticed. Analysis of the overall survival and event-free survival revealed trends to longer survival rates in patients with a belowmedian LI (≤7.6%) and below-median Ts value (≤14.3 h). These trends were more pronounced in the group of de novo AML (n=23), where the prolonged event-free survival in patients with below-median Ts reached statistical significance (p=0.02). None of the other parameters appeared significantly correlated with survival, although there was a trend to longer survival rates in patients who had no spontaneous clonogenic growth capacity (p=0.13). In conclusion, proliferation parameters in leukemic cells provide additional information on the cell biologic characteristics of AML, and these parameters may have prognostic value for response and duration of survival in AML.

Mitoxantrone: Pharmacokinetic and Pharmacodynamic Studies in Patients with Leukemia

Mitoxantrone is one of the newer drugs with cytotoxic activity against leukemic cells. The drug binds to DNA and it induces both single- and double-strand breaks and DNA-protein crosslinks within the cells. In addition the drug binds to the cellular cytoskeleton. It appears that binding of the drug in the various cellular compartments occurs at a different rate, with different affinity and most likely also with different cytotoxic significance. It is not known which of these or other events is responsible for the interference with the survival of the cell. Mitoxantrone is widely distributed through the body and also accumulates in nonhematologic tissue [1, 2].