P.C.M. Linssen

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.

The Tetraspanin CD37 Orchestrates the alpha4beta1 Integrin-Akt Signaling Axis and Supports Long-Lived Plasma Cell Survival

Antibody-producing B cells require CD37-dependent integrin signaling for long-term survival. CD37 Stimulates Plasma Cell Survival To generate immunological memory, B cells with high-affinity immunoglobulin receptors proliferate and differentiate in germinal centers in the spleen to produce memory B cells and long-lived antibody-secreting cells known as plasma cells. van Spriel et al. found that mice deficient in the tetraspanin protein CD37 had defective antibody production and decreased numbers of germinal center B cells compared to those in wild-type mice, which was a result of enhanced apoptosis. Survival signals in B cells were initiated by engagement of the integrin α4β1 and activation of the downstream kinase Akt. In the absence of CD37, integrin clustering and function were impaired, and activation of the Akt survival pathway was defective. Thus, long-lived plasma cells rely on the tetraspanin CD37 to enable integrin-Akt survival signaling. Signaling by the serine and threonine kinase Akt (also known as protein kinase B), a pathway that is common to all eukaryotic cells, is central to cell survival, proliferation, and gene induction. We sought to elucidate the mechanisms underlying regulation of the kinase activity of Akt in the immune system. We found that the four-transmembrane protein CD37 was essential for B cell survival and long-lived protective immunity. CD37-deficient (Cd37−/−) mice had reduced numbers of immunoglobulin G (IgG)–secreting plasma cells in lymphoid organs compared to those in wild-type mice, which we attributed to increased apoptosis of plasma cells in the germinal centers of the spleen, areas in which B cells proliferate and are selected. CD37 was required for the survival of IgG-secreting plasma cells in response to binding of vascular cell adhesion molecule 1 to the α4β1 integrin. Impaired α4β1 integrin–dependent Akt signaling in Cd37−/− IgG-secreting plasma cells was the underlying cause responsible for impaired cell survival. CD37 was required for the mobility and clustering of α4β1 integrins in the plasma membrane, thus regulating the membrane distribution of α4β1 integrin necessary for activation of the Akt survival pathway in the immune system.

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.

Chemokine induction by all-trans retinoic acid and arsenic trioxide in acute promyelocytic leukemia: triggering the differentiation syndrome

In acute promyelocytic leukemia (APL), differentiation therapy with all-trans retinoic acid (ATRA) and/or arsenic trioxide can induce a differentiation syndrome (DS) with massive pulmonary infiltration of differentiating leukemic cells. Because chemokines are implicated in migration and extravasation of leukemic cells, chemokines might play a role in DS. ATRA stimulation of the APL cell line NB4 induced expression of multiple CC-chemokines (CCLs) and their receptors (> 19-fold), resulting in increased chemokine levels and chemotaxis. Induction of CCL2 and CCL24 was directly mediated by ligand-activated retinoic acid receptors. In primary leukemia cells derived from APL patients at diagnosis, ATRA induced chemokine production as well. Furthermore, in plasma of an APL patient with DS, we observed chemokine induction, suggesting that chemokines might be important in DS. Dexamethasone, which efficiently reduces pulmonary chemokine production, did not inhibit chemokine induction in APL cells. Finally, chemokine production was also induced by arsenic trioxide as single agent or in combination with ATRA. We propose that differentiation therapy may induce chemokine production in the lung and in APL cells, which both trigger migration of leukemic cells. Because dexamethasone does not efficiently reduce leukemic chemokine production, pulmonary infiltration of leukemic cells may induce an uncontrollable hyperinflammatory reaction in the lung.

Plasma and cellular adriamycin concentrations in patients with myeloma treated with ninety-six-hour continuous infusion.

Adriamycin (ADM) concentrations in neoplastic plasma cells, nucleated blood cells, bone marrow cells, and plasma were measured in seven patients with advanced multiple myeloma. ADM was administered as a 96‐hour infusion of 9 mg/m2/24 hr. Maximum plasma ADM concentrations were 15.8 ± 4.4 ng/ml. ADM concentrations in nucleated blood cells, bone marrow cells, and plasma cells increased continuously throughout the 96‐hour infusion. Maximum cellular levels were up to 200‐fold higher than the maximum plasma concentration and were similar to levels observed shortly after administration of the total dose in one rapid injection. The cellular AUC for 96‐hour infusion and bolus injection were comparable. Thus continuous infusion is the equivalent of bolus injection in delivering ADM to the target cells in bone marrow, although plasma ADM concentrations remained very low. These results provide support for administering ADM as a continuous infusion with less toxicity and better patient tolerance.

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.

Cellular and plasma pharmacokinetics of weekly 20-mg 4′-epi-adriamycin bolus injection in patients with advanced breast carcinoma

SummaryWeekly low-dose injections of 20 mg 4′-epiadriamycin (E-ADM) were given to 12 patients with advanced postmenopausal breast cancer for at least 8 weeks. In advance, all patients were given hormonal therapy and polychemotherapy not containing anthracyclines. E-ADM concentrations in plasma and urine and in blood and bone marrow cells were determined during 8 consecutive weeks. Plasma concentrations in the range of a few nanograms per milliliter were seen up to 72–96 h. Cellular concentrations, and were 190±66 ng/109 cells on day 8, before the next injection was given. Nevertheless, no serious bone marrow toxicity was observed. In two patients with an increased plasma bilirubin concentration, cellular E-ADM concentrations were 20%–40% higher than those observed in the other patients. Plasma concentrations of E-ADM and 4′-epi-adriamycinol showed terminal half-lives 2–3 times longer and could be followed throughout the week. In three patients biopsies of skin metastases were examined. In two patients E-ADM could be demonstrated in the tumor tissue up to 7 days after the last injection. Although the number of patients investigated is too small to relate the drug kinetics to clinical response, it is of interest that the two patients with the highest cellular E-ADM concentrations responded better than the others.

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%.