ALBERT

Description: Here we show that endothelial cells (EC) require matrix type 1-metalloproteinase (MT1-MMP) for the formation of lumens and tube networks in 3-dimensional (3D) collagen matrices. A fundamental consequence of EC lumen formation is the generation of vascular guidance tunnels within collagen matrices through an MT1-MMP-dependent proteolytic process. Vascular guidance tunnels represent a conduit for EC motility within these spaces (a newly remodeled 2D matrix surface) to both assemble and remodel tube structures. Interestingly, it appears that twice as many tunnel spaces are created than are occupied by tube networks after several days of culture. After tunnel formation, these spaces represent a 2D migratory surface within 3D collagen matrices allowing for EC migration in an MMP-independent fashion. Blockade of EC lumenogenesis using inhibitors that interfere with the process (eg, integrin, MMP, PKC, Src) completely abrogates the formation of vascular guidance tunnels. Thus, the MT1-MMP-dependent proteolytic process that creates tunnel spaces is directly and functionally coupled to the signaling mechanisms required for EC lumen and tube network formation. In summary, a fundamental and previously unrecognized purpose of EC tube morphogenesis is to create networks of matrix conduits that are necessary for EC migration and tube remodeling events critical to blood vessel assembly.

Description: We show that endothelial cell (EC)–generated vascular guidance tunnels (ie, matrix spaces created during tube formation) serve as conduits for the recruitment and motility of pericytes along EC ablumenal surfaces to facilitate vessel maturation events, including vascular basement membrane matrix assembly and restriction of EC tube diameter. During quail development, pericyte recruitment along microvascular tubes directly correlates with vascular basement membrane matrix deposition. Pericyte recruitment to EC tubes leads to specific induction of fibronectin and nidogen-1 (ie, matrix-bridging proteins that link together basement membrane components) as well as perlecan and laminin isoforms. Coincident with these events, up-regulation of integrins, α5β1, α3β1, α6β1, and α1β1, which bind fibronectin, nidogens, laminin isoforms, and collagen type IV, occurs in EC-pericyte cocultures, but not EC-only cultures. Integrin-blocking antibodies to these receptors, disruption of fibronectin matrix assembly, and small interfering RNA suppression of pericyte tissue inhibitor of metalloproteinase (TIMP)-3 (a known regulator of vascular tube stabilization) all lead to decreased EC basement membrane, resulting in increased vessel lumen diameter, a key indicator of dysfunctional EC-pericyte interactions. Thus, pericyte recruitment to EC-lined tubes during vasculogenesis is a stimulatory event controlling vascular basement membrane matrix assembly, a fundamental maturation step regulating the transition from vascular morphogenesis to stabilization.

Description: To realize the therapeutic potential of human embryonic stem cells (hESCs), it is necessary to regulate their differentiation in a uniform and reproducible manner. We have developed a method in which known numbers of hESCs in serum-free medium were aggregated by centrifugation to foster the formation of embryoid bodies (EBs) of uniform size (spin EBs). These spin EBs differentiated efficiently and synchronously, as evidenced by the sequential expression of molecular markers representing stem cells, primitive streak, and mesoderm. In the presence of hematopoietic growth factors, reproducible differentiation was achieved with blood cells formed in more than 90% of EBs. Using chimeric EBs generated from mixtures of green fluorescence protein–positive (GFP+) and GFP– hESCs in a clonogenic assay, hematopoietic precursor frequency was estimated to be approximately 1:500 input cells. This method of EB formation provides a generally applicable means for modulating and objectively monitoring the directed differentiation of hESCs.

Description: Humanized anti-Tac is a genetically engineered human IgG1 monoclonal antibody specific for Tac, the alpha subunit of the interleukin-2 (IL- 2) receptor, and blocks IL-2-dependent activation of human T lymphocytes. The safety, pharmacokinetics, and immunosuppressive activity of humanized anti-Tac were evaluated in 20 patients who developed acute graft-versus-host disease (GVHD) after allogeneic marrow transplantation. Patients had developed acute GVHD at 5 to 26 (median, 14) days after transplantation and had failed to respond to primary therapy with glucocorticoids. Sequential groups of 4 patients each received a single 1-hour infusion of antibody in escalating doses of 0.5, 1.0, or 1.5 mg/kg; 8 additional patients were then treated with 1.5 mg/kg. A second infusion of antibody was administered after 11 to 48 (median, 16) days in 8 patients who had transient improvement of GVHD after the first infusion. Acute side effects, limited to chills in 1 patient and diaphoresis in another, were observed during or shortly after the antibody infusion. Overall improvement of acute GVHD occurred in 8 patients, 6 of whom were treated with a single antibody infusion and 2 with two infusions. Four responses were complete and 4 were partial. Three additional patients had improvement in one organ but progression in another. Responses occurred in 9 of 16 cases with skin disease, 3 of 15 with liver disease, and 6 of 12 with gastrointestinal disease. Two patients survive at 529 and 645 days after antibody treatment. Two patients died after relapse of leukemia. Sixteen patients died of infection or organ failure between 5 and 211 (median, 55) days. The terminal elimination half-life of the antibody was 44 to 363 hours, with a harmonic mean of 79, 88, and 94 hours, respectively, for the three doses studied. Absolute peripheral blood T-lymphocyte counts remained unchanged during the 56 days after infusion of the antibody. A fraction of circulating T cells expressed the alpha chain of the IL-2 receptor that, in some patients, was bound by antibody in vivo up to 28 days after treatment. No patient developed a measurable antibody response to humanized anti-Tac. Humanized anti-Tac has a long half-life after intravenous injection in humans, superior to any rodent monoclonal antibody specific for human T cells, and does not appear to induce antibody formation in recipients of marrow transplants. Improvement of steroid-refractory GVHD in 40% of patients after only one or two antibody infusions indicates that humanized anti-Tac is immunosuppressive.

Description: The human CD34 surface antigen is selectively expressed on hematopoietic stem/progenitor cells, suggesting that it plays an essential role in early hematopoiesis. Using a 1.5-kb partial human CD34 cDNA sequence, RNA-polymerase chain reaction (PCR), and rapid amplification of cDNA ends (RACE) methods, we cloned and sequenced the full-length (2.65 kb) cDNA. The cDNA encodes a type I transmembrane protein with no obvious homology to other known proteins. The entire CD34 gene of 28 kb was cloned, and the coding sequences mapped to eight exons. Mapping of the 5′ termini of mRNAs by 5′-RACE and RNAase protection analyses has indicated that the human CD34 gene uses multiple transcription initiation sites. Analysis of the upstream regulatory sequences revealed the absence of TATA and CAAT box sequences, and the presence of myb, myc, and ets-like DNA binding motifs. We have identified significant homology between human and mouse CD34 genes in 5′ and 3′ untranslated regions, amino acid coding sequences, and 5′ flanking sequences. This investigation of the CD34 gene should facilitate study of the function and regulation of this stem cell antigen.

Description: Purpose Ovarian cancer is the most lethal gynecologic cancer. Chemotherapy, the standard of care, has hematologic toxicity, primarily neutropenia. G-CSF is currently used to support white blood cell (WBC) and absolute neutrophil counts (ANC). Prior clinical trials from China suggest that acupuncture could ameliorate chemotherapy-induced leukopenia; the proposed mechanism is an increase in G-CSF levels. In the current study, we investigated the effect of acupuncture, administered during myelosuppressive therapy, on WBC and ANC counts in ovarian cancer patients. Patients and methods Twenty-one newly diagnosed or recurrent ovarian cancer patients were randomized to receive active versus sham acupuncture while undergoing standard IV platinum and taxane-containing chemotherapy. A standardized protocol with 9 acupuncture points was employed with manual and electroacupuncture stimulation. The frequency of acupuncture treatment was 2–3 times per week for a total of 10 sessions, starting 1 week before the 2nd cycle of chemotherapy. WBC and ANC counts were checked weekly at five time points. Serum G-CSF was collected four times during the study. Results Of 587 patients screened, 21 patients were enrolled and received either acupuncture or sham treatment. Patients in both the active and control arms had similar patient characteristics and treatment. Both median WBC and ANC values at nadir in the acupuncture arm were higher than in the control arm, but the differences were not statistically significant, after adjusting for the baseline difference. However, the median WBC in the acupuncture arm at recovery was statistically significantly higher than the control arm, after adjustment (8,600 cell/μL, range: 4,800–12,000 vs. 4,400 cell/μL range: 2,300–10,000) (p=0.045). The recovering median ANC in the patients receiving acupuncture also was higher, but this difference was not statistically significant (p=0.094). The median serum G-CSF at baseline for patients in the active vs. control arm was similar (37.3 pg/mL, range 28.6–393.3 vs. 32.0, range 11.8–211.3, respectively) (p=0.291). At the second time point, the 1st day of the 2nd cycle, the acupuncture group had a higher G-CSF value than the control group (p=0.121). At nadir, the acupuncture group still had a slightly higher G-CSF value than in the control group (p=0.796). However, at the recovery day, the 1st day of 3rd cycle, the G-CSF value in the acupuncture group was lower than in the control arm (p=0.729). No statistical significance in G-CSF value was found at each time point between the two groups. Conclusion The acupuncture protocol used in this study was feasible and safe. We report trends of higher WBC and ANC values during one cycle of myelosuppressive chemotherapy in ovarian cancer patients, suggesting a potential myeloprotective effect of acupuncture. However, current data do not support an acupuncture effect on G-CSF production. These findings warrant a larger study to explore the observed clinical trends and other potential underlying mechanisms.