Early discontinuation of empirical antibiotic treatment in neutropenic patients with acute myeloid leukaemia and high-risk myelodysplastic syndrome.

INTRODUCTION: Current guidelines advocate empirical antibiotic treatment (EAT) in haematological patients with febrile neutropenia. However, the optimal duration of EAT is unknown. In 2011, we have introduced a protocol, promoting discontinuation of carbapenems as EAT after 3 days in most patients and discouraging the standard use of vancomycin. This study assesses the effect of introducing this protocol on carbapenem and vancomycin use in high-risk haematological patients and its safety. METHODS: A retrospective before-after study was performed comparing a cohort from 2007 to 2011 (period I, before restrictive EAT use) with a cohort from 2011 to 2014 (period II, restrictive EAT use). Neutropenic episodes related to chemotherapy or stem cell transplantation (SCT) in patients with acute myeloid leukaemia (AML) or high-risk myelodysplastic syndrome (MDS) were analysed. The primary outcome was the use of carbapenems and vancomycin as EAT during neutropenia, expressed as days of therapy (DOT)/100 neutropenic days and analysed with interrupted time series (ITS). Also the use of other antibiotics was analysed. Safety measurements included 30-day mortality, ICU admittance within 30 days after start of EAT and positive blood cultures with carbapenem-susceptible microorganisms. RESULTS: Three hundred sixty-two neutropenic episodes with a median duration of 18 days were analysed, involving 201 patients. ITS analysis showed decreased carbapenem use with a step change of - 16.1 DOT/100 neutropenic days (95% CI - 26.77 to - 1.39) and an overall reduction of 21.6% (8.7 DOT/100 neutropenic days). Vancomycin use decreased with a step change of - 13.7 DOT/100 neutropenic days (95% CI - 23.75 to - 3.0) and an overall reduction of 54.7% (14.6 DOT/100 neutropenic days). The use of all antibiotics combined decreased from 155.6 to 138 DOT/100 neutropenic days, a reduction of 11.3%. No deaths directly related to early discontinuation of EAT were identified, also no notable difference in ICU-admission (9/116 in period I, 9/152 in period II) and positive blood cultures (4/116 in period I, 2/152 in period II) was detected. CONCLUSION: The introduction of a protocol promoting restrictive use of EAT resulted in reduction of carbapenem and vancomycin use and appears to be safe in AML or high-risk MDS patients with febrile neutropenia during chemotherapy or SCT.

Fludarabine exposure in the conditioning prior to allogeneic hematopoietic cell transplantation predicts outcomes.

Fludarabine is the most frequently used agent in conditioning regimens for allogeneic hematopoietic cell transplantation (HCT). Body surface area-based dosing leads to highly variable fludarabine exposure. We studied the relation between fludarabine exposure and clinical outcomes. A retrospective, pharmacokinetic-pharmacodynamic analysis was conducted with data from patients undergoing HCT with fludarabine (160 mg/m2) as part of a myeloablative conditioning (busulfan targeted to an area under the plasma-concentration-time curve [AUC] of 90 mg*h/L) and rabbit antithymocyte globulin (6-10 mg/kg; from day -9/-12) between 2010 and 2016. Fludarabine exposure as AUC was calculated for each patient using a previously published population pharmacokinetic model and related to 2-year event-free survival (EFS) by means of (parametric) time-to-event models. Relapse, nonrelapse mortality (NRM), and graft failure were considered events. One hundred ninety-two patients were included (68 benign and 124 malignant disorders). The optimal fludarabine exposure was determined as an AUC of 20 mg*h/L. In the overexposed group, EFS was lower (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.1-3.5; P = .02), due to higher NRM (HR, 3.4; 95% CI, 1.6-6.9; P <001) associated with impaired immune reconstitution (HR, 0.43; 95% CI, 0.26-0.70; P <001). The risks of NRM and graft failure were increased in the underexposed group (HR, 3.3; 95% CI, 1.2-9.4; P = .02; HR, 4.8; 95% CI, 1.2-19; P = .02, respectively). No relationship with relapse was found. Fludarabine exposure is a strong predictor of survival after HCT, stressing the importance of optimum fludarabine dosing. Individualized dosing, based on weight and "renal function" or "therapeutic drug monitoring," to achieve optimal fludarabine exposure might improve survival.

Pitfalls in cytokine measurements - Plasma TGF-ß1 in chronic fatigue syndrome.

BACKGROUND: Serum TGF-ß1 concentrations are reported to be elevated in chronic fatigue syndrome (CFS). However, measurement of circulating cytokines is a complex procedure and control of pre-analytical procedures is essential. The objective of the current study was to measure circulating TGF-ß1 concentrations in CFS patients compared to healthy controls, taking into account differences in pre-analytical procedures. METHODS: Two cohorts of female CFS patients were included. In both studies patients were asked to bring a healthy, age-matched control. At baseline, TGF-ß1 levels were measured in plasma and additionally P-selectin, a marker of platelet activity, was determined in a subgroup of participants. RESULTS: 50 patients and 48 controls were included in cohort I, and 90 patients and 29 controls in cohort II. Within the cohorts there were no differences in TGF-ß1 concentrations. However, between the cohorts there was a large discrepancy, which appeared to be caused by differences in g-force of the centrifuges used. The lower g-force used in cohort II (1361 g) caused more platelet activation, reflected by higher p-selectin concentrations, compared to cohort I (p < 0.0001), which was confirmed in a second independent experiment. There was a correlation between TGF-ß1 and p-selectin concentrations (r 0.79, p < 0.0001). CONCLUSION: These results demonstrate that control of pre-analytical procedures is an essential aspect when measuring circulating cytokines. No evidence for enhanced TGF-ß1 in patients with CFS was found.

AU binding proteins recruit the exosome to degrade ARE-containing mRNAs.

Inherently unstable mammalian mRNAs contain AU-rich elements (AREs) within their 3' untranslated regions. Although found 15 years ago, the mechanism by which AREs dictate rapid mRNA decay is not clear. In yeast, 3'-to-5' mRNA degradation is mediated by the exosome, a multisubunit particle. We have purified and characterized the human exosome by mass spectrometry and found its composition to be similar to its yeast counterpart. Using a cell-free RNA decay system, we demonstrate that the mammalian exosome is required for rapid degradation of ARE-containing RNAs but not for poly(A) shortening. The mammalian exosome does not recognize ARE-containing RNAs on its own. ARE recognition requires certain ARE binding proteins that can interact with the exosome and recruit it to unstable RNAs, thereby promoting their rapid degradation.

The heterogeneous nuclear ribonucleoproteins I and K interact with a subset of the ro ribonucleoprotein-associated Y RNAs in vitro and in vivo.

The hY RNAs are a group of four small cytoplasmic RNAs of unknown function that are stably associated with at least two proteins, Ro60 and La, to form Ro ribonucleoprotein complexes. Here we show that the heterogeneous nuclear ribonucleoproteins (hnRNP) I and K are able to associate with a subset of hY RNAs in vitro and demonstrate these interactions to occur also in vivo in a yeast three-hybrid system. Experiments performed in vitro and in vivo with deletion mutants of hY1 RNA revealed its pyrimidine-rich central loop to be involved in interactions with both hnRNP I and K and clearly showed their binding sites to be different from the Ro60 binding site. Both hY1 and hY3 RNAs coprecipitated with hnRNP I in immunoprecipitation experiments performed with HeLa S100 extracts and cell extracts from COS-1 cells transiently transfected with VSV-G-tagged hnRNP-I, respectively. Furthermore, both anti-Ro60 and anti-La antibodies coprecipitated hnRNP I, whereas coprecipitation of hnRNP K was not observed. Taken together, these data strongly suggest that hnRNP I is a stable component of a subpopulation of Ro RNPs, whereas hnRNP K may be transiently bound or interact only with (rare) Y RNAs that are devoid of Ro60 and La. Given that functions related to translation regulation have been assigned to both proteins and also to La, our findings may provide novel clues toward understanding the role of Y RNAs and their respective RNP complexes.

Three novel components of the human exosome.

The yeast exosome is a complex of 3' --> 5' exoribonucleases. Sequence analysis identified putative human homologues for exosome components, although several were found only as expressed sequence tags. Here we report the cloning of full-length cDNAs, which encode putative human homologues of the Rrp40p, Rrp41p, and Rrp46p components of the exosome. Recombinant proteins were expressed and used to raise rabbit antisera. In Western blotting experiments, these decorated HeLa cell proteins of the predicted sizes. All three human proteins were enriched in the HeLa cells nucleus and nucleolus, but were also clearly detected in the cytoplasm. Size exclusion chromatography revealed that hRrp40p, hRrp41p, and hRrp46p were present in a large complex. This cofractionated with the human homologues of other exosome components, hRrp4p and PM/Scl-100. Anti-PM/Scl-positive patient sera coimmunoprecipitated hRrp40p, hRrp41p, and hRrp46p demonstrating their physical association. The immunoprecipitated complex exhibited 3' --> 5' exoribonuclease activity in vitro. hRrp41p was expressed in yeast and shown to suppress the lethality of genetic depletion of yeast Rrp41p. We conclude that hRrp40p, hRrp41p, and hRrp46p represent novel components of the human exosome complex.

Frog diazepam-binding inhibitor: peptide sequence, cDNA cloning, and expression in the brain.

Three peptides derived from diazepam-binding inhibitor (DBI) were isolated in pure form from the brain of the frog Rana ridibunda. The primary structures of these peptides showed that they correspond to mammalian DBI-(1-39), DBI-(58-87), and DBI-(70-87). A set of degenerate primers, whose design was based on the amino acid sequence data, was used to screen a frog brain cDNA library. The cloned cDNA encodes an 87-amino acid polypeptide, which exhibits 68% similarity with porcine and bovine DBI. Frog DBI contains two paired basic amino acids (Lys-Lys) at positions 14-15 and 62-63 and a single cysteine within the biologically active region of the molecule. Northern blot analysis showed that DBI mRNA is expressed at a high level in the brain but is virtually absent in peripheral tissues. The distribution of DBI mRNA and DBI-like immunoreactivity in the frog brain was studied by in situ hybridization and immunocytochemistry. Both approaches revealed that the DBI gene is expressed in ependymal cells and circumventricular organs lining the ventricular cavity. Since amphibia diverged from mammals at least 250 million years ago, the data show that evolutionary pressure has acted to conserve the structure of DBI in the vertebrate phylum. The distribution of both DBI mRNA and DBI-like immunoreactivity indicates that DBI is selectively expressed in glial cells.

Cell cycle kinetics of hematopoiesis before and after in vivo administration of GM-CSF in refractory anemia: evidence for a shortening of the granulocyte release time.

GM-CSF administration to patients with refractory anemia (RA) induces an increase in neutrophils and eosinophils. We studied cell kinetic mechanisms underlying this observation using clonogenic assays and in vivo iododeoxyuridine labeling of bone marrow cells. Cell cycle kinetics were studied in three patients before and during GM-CSF administration (two daily subcutaneous injections of 54 or 108 micrograms). No consistent effect on the relative number of bone marrow CFU-GM was noticed. The DNA synthesis time and potential doubling time of low-density bone marrow cells remained essentially the same. A slight decrease (1.5-3.7%) in labeling index was found, originating from the myelo(-mono)cytic lineage. In all three patients the release time of labeled granulocytes from the bone marrow into the peripheral blood was shortened (before GM-CSF treatment 5-7 days and during GM-CSF 3-4 days). Cell cycle kinetics of CD34+ cells were studied in order to obtain kinetic information on immature precursor and progenitor cells. The DNA synthesis time of the CD34+ cells was shortened during GM-CSF therapy, resulting in a shorter potential doubling time. GM-CSF administration to patients with RA results in a rise in granulocytes that might be due partly to an accelerated release of granulocytes from the bone marrow compartment into the circulating blood and partly to an increased proliferative activity of the immature precursor and progenitor cells.

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.

Infusion-rate independent cellular adriamycin concentrations and cytotoxicity to human bone marrow clonogenic cells (CFU-GM).

The effect of adriamycin (ADM) infusion-rate on cellular ADM concentrations and on clonogenicity of human haematopoietic cells was studied in vivo and in vitro. In patients an ADM dose of 30 mg m-2 was administered as a bolus injection, or as a 4 h or a 24 h infusion. In vitro the effect of ADM on clonogenic cell growth was determined after exposure during 5 min, 2 h and 24 h of human bone marrow cells to increasing ADM concentrations. ADM showed rapid intracellular accumulation, to levels 100-fold the plasma concentration in vivo or the incubation medium concentration in the in vitro experiments. After a bolus injection or 5 min exposure only approximately 10% of the cellular peak ADM was retained after elimination of the drug from the plasma or the incubation medium. Ninety percent of the ADM was apparently 'loosely' bound. After 4 h and 24 h constant-rate infusions and also after 2 h and 24 h incubations in vitro, the cells accumulated ADM gradually, and the subsequent washing-out of the cellular ADM was substantially less, most of the ADM being 'tightly' bound. Despite these different patterns of uptake and retention after in vivo short- and long-lasting infusion of the same total dose, the 'tightly-bound' cellular ADM concentrations were the same. Moreover, comparable cellular ADM concentrations, retained after efflux of the 'loosely-bound' cellular ADM fraction were equally cytotoxic to normal human clonogenic cells. Short-lasting cellular peak ADM concentrations which occur after a bolus injection or after short exposure to high ADM concentrations are not essential for the cytotoxic effect, in contrast to the retained, 'tightly-bound' cellular ADM levels.

Influence of dose and duration of exposure on the cytotoxic effect of cytarabine toward human hematopoietic clonogenic cells.

The cytotoxic effect of cytarabine (ara-C) on the clonogenic potential of human normal and leukemic hematopoietic cells was investigated. Cells were exposed to ara-C at different concentrations and for periods of one to 120 hours and continuously. Colony growth (CFU-GM/CFU-E/BFU-E) in semisolid culture was assessed after seven and 14 days. The exposure time to ara-C appeared much more important in colony growth inhibition than the drug concentration. For instance, one-hour exposure to 10(-5) mol/L ara-C appeared not cytotoxic, while cocultivation in the presence of 10(-7) mol/L ara-C resulted in a total inhibition of colony growth. Cell fractionation with use of counterflow centrifugation allowed enrichment in subfractions for cells with different amounts of DNA. The inhibition of the clonogenic potential by ara-C was most pronounced in the cell fractions with the highest proliferation activity. Colony-forming cells, assessed after 14 days of culturing appeared less sensitive for ara-C cytotoxicity than seven-day CFUs. This means that ara-C is more cytotoxic to cycling than noncycling cells because compared to the seven-day colonies, 14-day colonies originate from the more resting, more primitive progenitor cells. The cytotoxicity of ara-C to clonogenic cells appears to be related to the proliferating and the cycling state of the progenitor cells and increases with the time of exposure. This phenomenon may be explained by the fact that ara-C is a cycle-specific drug and by the fact that the probability of cells entering the cell cycle is a time-dependent process. The results of this study indicate that development of more effective antileukemic therapy should not aim so much at very high drug levels but rather at prolonged administration of ara-C.

The relation of exposure time and drug concentration in their effect on cloning efficiency after incubation of human bone marrow with cytosine arabinoside.

The effect of different cytosine arabinoside (Ara-C) concentrations and exposure times upon clonogenicity of normal bone marrow cells was studied. One hour incubation, even at the pharmacologically high Ara-C concentration of 10(-5) M, was not cytotoxic. Prolonged incubation resulted in a very great increase in Ara-C cytotoxicity, provided that inactivation of Ara-C by deamination was limited. The results show that long-term exposure to Ara-C, even at pharmacologically very low concentrations, is deleterious to clonogenic cells and provide an experimental basis for the reported therapeutic efficacy of long-term low dose Ara-C administration in leukaemia and preleukaemic syndromes.

Enrichment of human bone marrow aspirates for low-density mononuclear cells using a haemonetics discontinuous blood cell separator.

Isopycnic density floatation centrifugation has been proven to be a suitable technique to enrich bone marrow aspirates for clonogenic cells on a small scale. We have tested a Haemonetics semicontinuous blood cell separator in order to process large volumes of bone marrow with minimal bone marrow manipulation. The efficacy of isopycnic density floatation was tested in a one and a two-step procedure. Both procedures showed a recovery of about 20% of the nucleated cells and 1-2% of the erythrocytes. The enrichment of clonogenic cells in the one-step procedure appeared superior to the two-step enrichment, first separating buffy coat cells. The recovery of clonogenic cells was 70 and 50%, respectively. Repopulation capacity of the low-density cell fraction containing the clonogenic cells was excellent after autologous reinfusion (6 cases) and allogeneic bone marrow transplantation (3 cases). Fast enrichment of large volumes of bone marrow aspirates with low-density cells containing the clonogenic cells by isopycnic density floatation centrifugation can be done safely using a Haemonetics blood cell separator.