Optimising parameters for peripheral blood leukapheresis after r-metHuG-CSF (filgrastim) and r-metHuSCF (ancestim) in patients with multiple myeloma: a temporal analysis of CD34(+) absolute counts and subsets

Patients (n = 69) with multiple myeloma undergoing peripheral blood stem cell collection (PBSC) were treated with cyclophosphamide and a combination of recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) and recombinant methionyl human stem cell factor (r-metHuSCF, ancestim). The objectives of this study were to determine: (1) The proportion of patients reaching a target yield of >or=5 x 10(6) CD34(+) cells/kg in one or two successive large-volume (20 liter) leukapheresis procedures; (2) the optimal collection time for leukapheresis; (3) mobilization kinetics of CD34(+) subsets in response to G-CSF/SCF. All patients were mobilized with cyclophosphamide (2.5 g/m(2)) on day 0 followed by filgrastim (10 microg/kg ) plus ancestim (20 microg/kg) commencing day 1 and continuing to day 11 or 12. Of the 65 evaluable patients, 57 were considered not heavily pretreated and 96.5% obtained a target of >or=5 x 10(6)/kg in one collection. The median CD34(+) cells/kg was 39.5 x 10(6) (range: 5.2-221.2 x 10(6)). Subset analysis demonstrated the number of CD38(-), CD33(-), and CD133(+) peaked at day 11; and CD34(+), CD90(+) cells peaked at day 10. The optimum day for leukapheresis was determined to be day 11. The median absolute peripheral blood CD34(+) cell numbers on day 11 was 665 x 10(6)/l (range: 76-1481 x 10(6)/l). Eight of the 10 heavily pretreated patients were evaluable: three achieved the target dose in one leukapheresis (37.5%) and three (37.5%) achieved the target dose with two leukaphereses. Use of this mobilization strategy allowed the collection of high numbers of CD34(+) cells and early progenitors and the ability to predictably schedule leukapheresis.

Number of viable CD34(+) cells reinfused predicts engraftment in autologous hematopoietic stem cell transplantation

Reduced CD34(+) cell viability due to cryopreservation has unknown effects on subsequent hematopoietic engraftment in autologous transplantation. Thirty-six consecutive autologous peripheral stem cell collections were analyzed for absolute viable CD34(+) cell numbers at the time of stem cell collection and prior to re-infusion. Viable CD34(+) cells were enumerated using single platform flow cytometry and the molecular exclusion dye 7-amino actinomycin D. The median number of viable CD34(+) cells was 3.6 x 10(6)/kg at the time of harvest and 2.0 x 10(6)/kg after thawing. When viable CD34(+)cells enumerated after thawing were <2.0, 2.0-5.0, or >5.0 x 10(6)/kg, the median time to platelet engraftment was 17, 12 and 10 days, respectively (P < 0.05 for comparison of the group with <2.0 x 10(6)/kg and the other two groups), and the median time to neutrophil engraftment was 13, 14 and 12 days, respectively (P = NS). A minimum of 2.0 x 10(6) CD34(+) cells/kg was harvested in 33 of 36 patients (92%) but only 19 of 36 (52%) patients met this threshold at the time of reinfusion. The reduced numbers of viable CD34(+) cells measured prior to re-infusion is associated with time to platelet engraftment and may be useful in monitoring stem cell loss during processing and identifying patients at risk of graft failure.

Comparison of five platforms for enumeration of residual leucocytes in leucoreduced blood components

The need for quality control of leucoreduction of blood products has led to the development of various methods to count low levels of residual leucocytes. We compared five platforms side-by-side: the Nageotte haemocytometer and four based on fluorescent staining of nuclei: two flowcytometers (Beckman Coulter, BD Biosciences) with methods based on counting beads, a volumetric flow cytometer (Partec) and the microvolumic fluorimeter ImagN2000 (BD Biosciences), all according to their manufacturers' recommended methods. Analysis of double-filtered red cell concentrates (RCCs) and platelet concentrates (PCs), spiked with various numbers of leucocytes, revealed good linearity for all methods over the range of 1.6-32.7 leucocytes/microl, all with r(2) > 0.99. At the rejection level of leucocyte-reduced blood components, i.e. 1 x 10(6) per unit corresponding with approximately 3.3 leucocytes/microl, the Nageotte haemocytometer had low accuracy (0% for RCCs, 56% for PCs), and was relatively imprecise [coefficient of variance (CV) of 34% and 30% respectively]. The Partec flow cytometer gave good results for RCCs (accuracy 67%, CV 22%), but not for PCs (accuracy 0%, CV 25%). The ImagN2000 had an accuracy of 44% for RCCs and 89% for PCs, but the precision was variable (CV 32% for RCCs, 15% for PCs). The best results were obtained with the Beckman Coulter (RCCs: accuracy 86%, CV 13%, PCs: accuracy 67%, CV 16%), and BD Biosciences platforms (RCCs: accuracy 100%, CV 10%; PCs: accuracy 89%, CV 11%). We conclude that, at the rejection level of 1 x 10(6) leucocytes per unit, the widely used Nageotte haemocytometer performs poorly in terms of inaccuracy and imprecision, and that both counting-bead-based, flow cytometric methods performed best.

A comparison of three rapid D-dimer methods for the diagnosis of venous thromboembolism

We compared three rapid D-dimer methods for the diagnosis of venous thromboembolism. Patients presenting to four teaching hospitals with the possible diagnosis of deep vein thrombosis or pulmonary embolism were investigated with a combination of clinical likelihood, D-dimer (SimpliRED) and initial non-invasive testing. Patients were assigned as being positive or negative for deep vein thrombosis or pulmonary embolism based on their three-month outcome and initial test results. The three D-dimer methods compared were: (a) Accuclot D-dimer (b) IL-Test D-dimer (c) SimpliRED D-dimer. Of 993 patients, 141 had objectively confirmed deep vein thrombosis or pulmonary embolism. The sensitivity of SimpliRED, Accuclot and IL-Test were 79, 90 and 87% respectively. All three D-dimer tests gave similar negative predictive values. The SimpliRED D-dimer was found to be less sensitive than the Accuclot or IL-Test. When combined with pre-test probability all three methods are probably acceptable for use in the diagnosis of venous thromboembolism.

Inactivation of p53 sensitizes U87MG glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea

We examined the effect of p53 inactivation on the response of U87MG glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). These studies were motivated by three observations: (a) some human astrocytomas are sensitive to BCNU and some are resistant; (b) chemosensitive astrocytomas are more likely to be found in young adults whose tumors are more likely to harbor a p53 mutation; and (c) mouse astrocytes lacking the p53 gene are more sensitive to BCNU than wild-type cells. Here, we observed that p53 inactivation by transfection with pCMV-E6 sensitized U87MG cells to BCNU. Compared with control U87MG-neo cells with intact p53 function, the clonogenic survival of U87MG-E6 cells exposed to BCNU was reduced significantly. In U87MG-E6 cells, sensitization to BCNU was associated with failure of p21(WAF1) induction, transient cell cycle arrest in S phase, accumulation of polyploid cells, and significant cell death. In contrast, resistance to BCNU in U87MG-neo cells was associated with up-regulation of p53, prolonged induction of p21(WAF1), sustained cell cycle arrest in S phase, and enhancement of DNA repair. U87MG cells with disrupted p53 function were less able to repair BCNU-induced DNA damage and survive this chemotherapeutic insult. The question arises of whether p53 dysfunction might be a chemosensitizing genetic alteration in human astrocytic gliomas.

Flow cytometric enumeration and immunophenotyping of hematopoietic stem and progenitor cells

Flow cytometric enumeration of CD34(+) hematopoietic stem and progenitor cells (HPC) is widely used to evaluate the adequacy of peripheral blood stem cell grafts and is also useful for planning the apheresis sessions needed to obtain these grafts. A state-of-the-art method to enumerate CD34(+) cells has been developed that makes use of a multiparameter definition of HPC, based on their light scatter characteristics and dim expression of CD45, utilizing fluorescent counting beads. This approach allows the absolute CD34(+) cell count to be determined directly from a flow cytometer. The method can be extended with a viability stain and additional markers for further immunologic characterization of CD34(+) cells, and has been successfully implemented in multicenter trials. Using such a standardized assay, it should be possible to define more accurately the lower threshold for a safe HPC graft in terms of short- and long-term hematopoietic reconstitution. Semin Hematol 38:139-147.

Flow cytometric enumeration and immunophenotyping of hematopoietic stem and progenitor cells

Flow cytometric enumeration of CD34+ hematopoietic stem and progenitor cells (HPC) is widely used for evaluation of graft adequacy of peripheral blood stem cell grafts, and is also useful in planning the apheresis sessions necessary to obtain these grafts. The state-of-the-art method to enumerate CD34+ cells makes use of a multiparameter definition of HPC based on their light scatter characteristics and dim expression of CD45, and the use of counting beads to derive the concentration of CD34+ cells directly from the flow cytometric assessment. This method can be extended with a viability stain and additional markers for further immunological characterization of CD34+ cells, and has been successfully implemented in multicenter trials. Thus, the lower threshold of a safe HPC graft in terms of short- and long-term hematopoiesis may be more accurately defined.

The human hematopoietic stem cell compartment is heterogeneous for CXCR4 expression

The chemokine stromal derived factor-1alpha (SDF-1alpha) has been implicated recently in the chemotaxis of primitive human hematopoietic cells, suggesting that pluripotent human stem cells express the SDF-1alpha receptor, CXCR4. By using flow cytometry and confocal microscopy, we have identified and isolated primitive subsets of human CXCR4(+) and CXCR4(-) cells. Distinctions in the progenitor content and response to SDF-1alpha in vitro indicate that CXCR4(+) and CXCR4(-) cells represent discrete populations of primitive blood cells. The i.v. transplantation of these subfractions into immune-deficient mice established that both possess comparable engraftment capacity in vivo. Human myeloid, lymphoid, and primitive CD34(+) CXCR4(+) cells were present in chimeric animals transplanted with either subset, indicating that CXCR4(+) and CXCR4(-) stem cells have equivalent proliferative and differentiative abilities. Our study indicates that the human stem cell compartment is heterogeneous for CXCR4 expression, suggesting that the relationship between CXCR4 expression and stem cell repopulating function is not obligatory.

Characterization of chemokine receptors expressed in primitive blood cells during human hematopoietic ontogeny

Chemokines are capable of regulating a variety of fundamental processes of hematopoietic cells that include proliferation, differentiation, and migration. To evaluate potential chemokine signaling pathways important to the regulation of primitive human hematopoietic cells, we examined chemokine receptor expression of highly purified subpopulations of uncommitted human blood cells. CXCR1-, CXCR2-, CXCR4-, and CCR5-expressing cells were detected by flow cytometry among human blood subsets depleted of lineage-restricted cells (Lin(-)) derived from adult bone marrow, mobilized peripheral blood, cord blood (CB), and circulating fetal blood. Although these chemokine receptors could be detected on Lin(-) cells throughout human development, only CXCR4 could be detected in CD34(-)CD38(-)Lin(-) and CD34(+)CD38(-)Lin(-) subfractions enriched for stem cell function, suggesting that independent of ontogeny, CXCR4-mediated signals are critical to primitive hematopoiesis. Distinct to other stages of human hematopoietic development, primitive CB cells expressed higher levels of CXCR1, CXCR2, CCR5, and CXCR4 on both CD34(-)CD38(-)Lin(-) and CD34(+)CD38(-)Lin(-) subsets. Isolation of these fractions revealed expression of additional chemokine receptors CCR7, CCR8, and Bonzo (STRL133), whereas BOB (GPR15) could not be detected. Our study illustrates that rare uncommitted hematopoietic cells express chemokine receptors not previously associated with primitive human blood cells. Based on these results, we suggest that signaling pathways mediated by chemokine receptors identified here may play a fundamental role in hematopoietic stem cell regulation and provide alternative receptor targets for retroviral pseudotyping for genetic modification of repopulating cells.

Isolation and characterization of human CD34(-)Lin(-) and CD34(+)Lin(-) hematopoietic stem cells using cell surface markers AC133 and CD7

Recent evidence indicates that human hematopoietic stem cell properties can be found among cells lacking CD34 and lineage commitment markers (CD34(-)Lin(-)). A major barrier in the further characterization of human CD34(-) stem cells is the inability to detect this population using in vitro assays because these cells only demonstrate hematopoietic activity in vivo. Using cell surface markers AC133 and CD7, subfractions were isolated within CD34(-)CD38(-)Lin(-) and CD34(+)CD38(-)Lin(-) cells derived from human cord blood. Although the majority of CD34(-)CD38(-)Lin(-) cells lack AC133 and express CD7, an extremely rare population of AC133(+)CD7(-) cells was identified at a frequency of 0.2%. Surprisingly, these AC133(+)CD7(-) cells were highly enriched for progenitor activity at a frequency equivalent to purified fractions of CD34(+) stem cells, and they were the only subset among the CD34(-)CD38(-)Lin(-) population capable of giving rise to CD34(+) cells in defined liquid cultures. Human cells were detected in the bone marrow of non-obese/severe combined immunodeficiency (NOD/SCID) mice 8 weeks after transplantation of ex vivo-cultured AC133(+)CD7(-) cells isolated from the CD34(-)CD38(-)Lin(-) population, whereas 400-fold greater numbers of the AC133(-)CD7(-) subset had no engraftment ability. These studies provide novel insights into the hierarchical relationship of the human stem cell compartment by identifying a rare population of primitive human CD34(-) cells that are detectable after transplantation in vivo, enriched for in vitro clonogenic capacity, and capable of differentiation into CD34(+) cells. (Blood. 2000;95:2813-2820)

The effect of time course and context on the facilitation of semantic features in the cerebral hemispheres

Two divided visual field priming experiments were designed to determine the nature of lexical retrieval in the cerebral hemispheres by studying the facilitation of semantic features of unambiguous nouns. Unambiguous nouns have a single meaning, yet semantic features associated with these nouns may vary in the degree to which they are compatible with this single meaning (e.g., LAMB-WOOL as compared with LAMB-CHOPS). Results suggest that the left hemisphere selects both strongly and weakly associated semantic features that are compatible with the dominant representation of the noun. Dominance compatibility, rather than association strength, seems to be the more important factor for deciding what features are maintained in the left hemisphere. In contrast, the right hemisphere maintains more varied information, including features that are less compatible with the dominant representation (Experiment 1) and context information (Experiment 2).

Cerebral hemispheric mechanisms linking ambiguous word meaning retrieval and creativity

The deferral of ambiguity resolution has been thought to be an important component of creativity. The time course of priming of dominant and subordinate meanings of ambiguous words was investigated using a divided visual field priming paradigm with subjects that varied on a measure of creativity. The Wallach-Kogan similarities subtest was used to group 72 subjects into three levels of verbal creativity to compare their performance on the ambiguity resolution task (Burgess & Simpson, 1988a). Results suggest that both the left and right hemispheres contribute to the maintenance of multiple word meanings in highly creative subjects, while less creative subjects show sustained subordinate priming only in the right hemisphere or no sustained subordinate priming. These results support an interactive, collaborative theory of verbal creativity (Bogen & Bogen, 1969) and suggest that there are important individual differences that expand on the basic time course model of hemispheric processing (Burgess & Simpson, 1988a).

The effect of time course and context on the facilitation of semantic features in the cerebral hemispheres

Two divided visual field priming experiments were designed to determine the nature of lexical retrieval in the cerebral hemispheres by studying the facilitation of semantic features of unambiguous nouns. Unambiguous nouns have a single meaning, yet semantic features associated with these nouns may vary in the degree to which they are compatible with this single meaning (e.g., LAMB-WOOL as compared with LAMB-CHOPS). Results suggest that the left hemisphere selects both strongly and weakly associated semantic features that are compatible with the dominant representation of the noun. Dominance compatibility, rather than association strength, seems to be the more important factor for deciding what features are maintained in the left hemisphere. In contrast, the right hemisphere maintains more varied information, including features that are less compatible with the dominant representation (Experiment 1) and context information (Experiment 2).

Three different chromogenic methods do not give equivalent anti-Xa levels for patients on therapeutic low molecular weight heparin (dalteparin) or unfractionated heparin

In this study we compare three chromogenic methods (IL-Heparin, Stachrom Heparin and Heparin Sigma) on two different instruments (ACL300+ and AMAX CS190) for patients on dalteparin (n = 41), a low molecular weight heparin or unfractionated heparin (n = 50). For dalteparin the mean anti-Xa levels for IL-Heparin, Stachrom Heparin and Heparin Sigma were 0.27, 0.30 and 0.21 U/ml, respectively, while for heparin they were 0.52, 0.55 and 0.41 U/ml, respectively. To test for instrument specific effects, IL-Heparin and Stachrom Heparin were repeated on both instruments on 42 patients receiving unfractionated heparin. For IL-Heparin the mean anti-Xa levels on the AMAX CS190 and ACL300+ were 0.51 and 0.59 U/ml, respectively, while for Stachrom Heparin they were 0.55 and 0.67 anti-Xa U/ml. We conclude that different chromogenic anti-Xa methods do not give equivalent anti-Xa levels for the same samples. Moreover, the differences are clinically significant. This is not explained entirely by instrumentation effects. Recommended therapeutic ranges may need to be method and instrument specific.