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

Community-Wide Experimental Evaluation of the PROSS Stability-Design Method

Recent years have seen a dramatic improvement in protein-design methodology. Nevertheless, most methods demand expert intervention, limiting their widespread adoption. By contrast, the PROSS algorithm for improving protein stability and heterologous expression levels has been successfully applied to a range of challenging enzymes and binding proteins. Here, we benchmark the application of PROSS as a stand-alone tool for protein scientists with no or limited experience in modeling. Twelve laboratories from the Protein Production and Purification Partnership in Europe (P4EU) challenged the PROSS algorithm with 14 unrelated protein targets without support from the PROSS developers. For each target, up to six designs were evaluated for expression levels and in some cases, for thermal stability and activity. In nine targets, designs exhibited increased heterologous expression levels either in prokaryotic and/or eukaryotic expression systems under experimental conditions that were tailored for each target protein. Furthermore, we observed increased thermal stability in nine of ten tested targets. In two prime examples, the human Stem Cell Factor (hSCF) and human Cadherin-Like Domain (CLD12) from the RET receptor, the wild type proteins were not expressible as soluble proteins in E. coli, yet the PROSS designs exhibited high expression levels in E. coli and HEK293 cells, respectively, and improved thermal stability. We conclude that PROSS may improve stability and expressibility in diverse cases, and that improvement typically requires target-specific expression conditions. This study demonstrates the strengths of community-wide efforts to probe the generality of new methods and recommends areas for future research to advance practically useful algorithms for protein science.

Ancestim (r-metHuSCF) plus filgrastim and/or chemotherapy for mobilization of blood progenitors in 513 poorly mobilizing cancer patients: the French compassionate experience

Ancestim (r-MetHuSCF) is available in France for compassionate use in patients who are candidates for high-dose chemotherapy and autologous transplantation, and who failed in previous attempts at mobilization and collection. We report here data from 513 adult patients who benefited from this program, between January 1998 and July 2007. Given with systematic premedication, ancestim was generally well tolerated, although severe but not life-threatening adverse events were reported in 12 individuals. Overall, a graft was obtained or completed for 235 patients (46%). The median number of collected CD34+ cells was 3.00 × 10(6)/kg (range: 0.03-39.50). The target threshold of 2 × 10(6) CD34+ cells/kg was reached in 161 patients (31%). Factors associated with collection were diagnosis of myeloma, no previous autologous transplant, no more than one previous failed attempt and a mobilization regimen including cytotoxic agents. A total of 207 patients (40%) proceeded to high-dose chemotherapy and autologous transplantation. The median time to reach 0.5 × 10(9)/L neutrophils and 20 × 10(9)/L platelets was 12 (6-40) and 13 (0-31) days, respectively. We conclude that a combination of ancestim with filgrastim successfully mobilized CD34+ cells in peripheral blood, and allowed adequate collection in preparation for autologous transplantation in approximately one-third of poorly mobilizing patients.

Stem cell factor prevents neuronal cell apoptosis after acute spinal cord injury

STUDY DESIGN

A rat spinal cord injury (SCI) model and immunohistochemistry were used to examine the levels of expression of stem cell factor and c-kit. In addition, we examined whether intraperitoneal administration of stem cell factor could prevent neural cells apoptosis after acute SCI.

OBJECTIVE

To evaluate the antiapoptotic effect of stem cell factor after SCI.

SUMMARY OF BACKGROUND DATA

It is well known that the mode of delayed neuronal and glial cell death after SCI is apoptosis. Inhibition of apoptosis might thus promote neurologic improvement after SCI. Stem cell factor and its receptor c-kit exhibit pleiotropic effects in early hematopoiesis, and are also known to prevent hematopoietic progenitor cell apoptosis. Stem cell factor has recently been reported to be a survival factor for neural stem cells in vitro. We examined the levels of expression of stem cell factor and c-kit in normal and injured rat spinal cord. In addition, we examined whether stem cell factor prevents neural cell apoptosis after acute SCI.

METHODS

We examined the expression of stem cell factor and c-kit in spinal cord after injury by quantitative RT-PCR and immunohistochemistry. Antiapoptotic effects of stem cell factor were examined using rats with SCI that received stem cell factor intraperitoneally, and were examined immunohistochemically with anticleaved PARP antibody and antiactive caspase-3 antibody between 1 and 3 days after injury.

RESULTS

Upregulation of stem cell factor and c-kit expression occured after SCI. We also found that neurons express stem cell factor, and neurons and oligodendrocytes express c-kit after SCI. In addition, intraperitoneal administration of stem cell factor prevented spinal neural cells apoptosis after injury.

CONCLUSION

These findings suggest the possibility that stem cell factor, a hematopoietic cytokine, could be useful as an agent for treatment of SCI.

Magnetic resonance imaging and confocal microscopy studies of magnetically labeled endothelial progenitor cells trafficking to sites of tumor angiogenesis

AC133 cells, a subpopulation of CD34+ hematopoietic stem cells, can transform into endothelial cells that may integrate into the neovasculature of tumors or ischemic tissue. Most current imaging modalities do not allow monitoring of early migration and incorporation of endothelial progenitor cells (EPCs) into tumor neovasculature. The goals of this study were to use magnetic resonance imaging (MRI) to track the migration and incorporation of intravenously injected, magnetically labeled EPCs into the blood vessels in a rapidly growing flank tumor model and to determine whether the pattern of EPC incorporation is related to the time of injection or tumor size.

MATERIALS AND METHODS

EPCs labeled with ferumoxide-protamine sulfate (FePro) complexes were injected into mice bearing xenografted glioma, and MRI was obtained at different stages of tumor development and size.

RESULTS

Migration and incorporation of labeled EPCs into tumor neovasculature were detected as low signal intensity on MRI at the tumor periphery as early as 3 days after EPC administration in preformed tumors. However, low signal intensities were not observed in tumors implanted at the time of EPC administration until tumor size reached 1 cm at 12 to 14 days. Prussian blue staining showed iron-positive cells at the sites corresponding to low signal intensity on MRI. Confocal microscopy showed incorporation into the neovasculature, and immunohistochemistry clearly demonstrated the transformation of the administered EPCs into endothelial cells.

CONCLUSION

MRI demonstrated the incorporation of FePro-labeled human CD34+/AC133+ EPCs into the neovasculature of implanted flank tumors.

Role of c-Kit and erythropoietin receptor in erythropoiesis

Erythropoiesis is regulated by a number of growth factors, among which stem cell factor (SCF) and erythropoietin (Epo) play a non-redundant function. Viable mice with mutations in the SCF gene (encoded by the Steel (Sl) locus), or its receptor gene c-Kit (encoded by the White spotting (W) locus) develop a hypoplastic macrocytic anemia. Mutants of W or Sl that are completely devoid of c-Kit or SCF expression die in utero of anemia between days 14 and 16 of gestation and contain reduced numbers of erythroid progenitors in the fetal liver. Likewise, Epo and Epo receptor (Epo-R)-deficient mice die in utero due to a marked reduction in the number of committed fetal liver derived erythroid progenitors. Thus, committed erythroid progenitors require both c-Kit and Epo-R signal transduction pathways for their survival, proliferation and differentiation. In vitro, Epo alone is capable of generating mature erythroid progenitors; however, a combined treatment of Epo and SCF results in synergistic proliferation and expansion of developing erythroid progenitors. This review summarizes recent advances made towards understanding the signaling mechanisms by which Epo-R and c-Kit regulate growth, survival, and differentiation of erythroid progenitors alone and cooperatively.

Factors for PBPC collection efficiency and collection predictors

Factors affecting collection efficiency of peripheral blood stem cells (PBSCs) include patient's age, diagnosis, preceding chemoradiotherapy, disease invasion of the bone marrow and mobilizing chemotherapy in PBSC collection for autologous transplants. Mobilizing cytokines, timing for apheresis, machines and operating software would affect mobilization and collection of PBSCs both for autologous and allogeneic transplantation. Also donor's age and gender would affect PBSC yield for allogeneic transplantation. Surrogate markers including peripheral blood CD34+ cell counts before mobilization and on day of collection have been reported to predict the yield of PBSC harvest. A number of standard procedures have been developed based on these findings. Newer agents for PBSC mobilization are being evaluated and still other factors affecting mobilization are being sought to better predict and cope with poor mobilization.

Kinetics of peripheral blood stem cell mobilization following G-CSF-supported chemotherapy

It would be a clinical and economical advantage if the optimal time point of peripheral blood stem cell (PBSC) mobilization following G-CSF-supported chemotherapy (CT) was known in advance. Therefore, we retrospectively analyzed mobilization parameters in 113 adult tumor patients treated in our institution within 1 year. The start of apheresis was guided by CD34(+) cell measurements in the PB and occurred on or after day 11 after start of mobilization CT in 97% of patients. The median peak (p)CD34(+) cell count in PB uniformly occurred on day 14-15 (range: 6-32 days) after the start of CT, irrespective of the diagnosis (multiple myeloma n = 76, other histology n = 37), the type, but not the amount, of premobilization CT or radiotherapy (RT), the mobilization regimen, or the G-CSF dosage administered. Among more heavily pretreated patients (>six cycles of prior CT or RT), a higher proportion mobilized late (pCD34(+) cell count later than day 20 in 12% and 13%, respectively, versus 2%-5% in the other groups). Therefore, we propose to start measuring CD34(+) cells in the PB on day 11 after the start of mobilization therapy. The wide range of optimal mobilization time points argues for an individualized rather than a preset start of apheresis.

Protection from endotoxemia by adenoviral-mediated gene transfer of human bactericidal/permeability-increasing protein

Sepsis represents a growing concern in high-risk patients and there has been a lack of effective preventives and therapies. Bacterial/permeability increasing protein (BPI) is a human neutrophil granule-associated defense molecule specific for Gram-negative bacteria and their products. To develop a BPI-transgene-based prophylactic or therapeutic modality, we have developed a recombinant, replication-deficient adenoviral vector expressing full-length human BPI protein (AdhBPI). The expression of BPI is under control of a murine cytomegalovirus (CMV) promoter. Using in vitro and in vivo systems, AdhBPI-mediated gene transfer led to extracellular secretion of BPI protein, which effectively neutralized endotoxin (lipopolysaccharide [LPS]) and markedly reduced the production of proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and macrophage inflammatory protein 2 (MIP-2) by freshly isolated murine alveolar macrophages. By using a mouse model of nonlethal sepsis elicited with LPS, we demonstrated that in vivo gene transfer of BPI was able to markedly inhibit the effect of a large dose of LPS on cytokine responses when injected intraperitoneally. Furthermore, such in vivo BPI gene transfer also improved the survival of mice suffering from lethal septic shock elicited by intraperitoneal injection of d-galactosamine and LPS. Thus, our results suggest that human BPI gene transfer vector has the potential to be used as a therapeutic agent for septic conditions.