Adhesion to fibronectin stimulates proliferation of wild-type and bcr/abl-transfected murine hematopoietic cells.
(17/11748)
Cells of most tissues require adhesion to a surface to grow. However, for hematopoietic cells, both stimulation and inhibition of proliferation by adhesion to extracellular matrix components have been described. Furthermore, it has been suggested that progenitor cells from chronic myelogenous leukemia show decreased beta1 integrin-mediated adhesion to fibronectin, resulting in increased proliferation and abnormal trafficking. However, we show here that the chronic myelogenous leukemia-specific fusion protein p210bcr/abl stimulates the expression of alpha5beta1 integrins and induces adhesion to fibronectin when expressed in the myeloid cell line 32D. Moreover, proliferation of both p210bcr/abl-transfected 32D (32Dp210) cells and untransfected 32D cells is stimulated by immobilized fibronectin. Cell cycle analysis revealed that nonadherent 32D and 32Dp210 cells are arrested in late G1 or early S phase, whereas the adherent fractions continue cycling. Although both adherent and nonadherent p210bcr/abl-transfected and parental 32D cells express equal amounts of cyclin A, a protein necessary for cell cycle progression at the G1/S boundary, cyclin A complexes immunoprecipitated from 32D cells cultured on immobilized fibronectin were found to be catalytically inactive in nonadherent but not in adherent cells. In addition, as compared with untransfected 32D cells, cyclin A immunoprecipitates from 32Dp210 cells exhibited a greatly elevated kinase activity and remained partially active irrespective of the adhesion status. The lack of cyclin A/cyclin-dependent kinase (CDK) 2 activity in nonadherent 32D cells appeared to result from increased expression and cyclin A complex formation of the CDK inhibitor p27(Kip1). Taken together, our results indicate that adhesion stimulates cell cycle progression of hematopoietic cells by down-regulation of p27(Kip1), resulting in activation of cyclin A/CDK2 complexes and subsequent transition through the G1/S adhesion checkpoint. (+info)
In vitro hematopoietic and endothelial potential of flk-1(-/-) embryonic stem cells and embryos.
(18/11748)
Mice deficient in the Flk-1 receptor tyrosine kinase are known to die in utero because of defective vascular and hematopoietic development. Here, we show that flk-1(-/-) embryonic stem cells are nevertheless able to differentiate into hematopoietic and endothelial cells in vitro, although they give rise to a greatly reduced number of blast colonies, a measure of hemangioblast potential. Furthermore, normal numbers of hematopoietic progenitors are found in 7.5-day postcoitum flk-1(-/-) embryos, even though 8. 5-day postcoitum flk-1(-/-) embryos are known to be deficient in such cells. Our results suggest that hematopoietic/endothelial progenitors arise independently of Flk-1, but that their subsequent migration and expansion require a Flk-1-mediated signal. (+info)
Transcriptional regulation of the cyclin D1 promoter by STAT5: its involvement in cytokine-dependent growth of hematopoietic cells.
(19/11748)
STAT5 is a member of a family of transcription factors that participate in the signal transduction pathways of many hormones and cytokines. Although STAT5 is suggested to play a crucial role in the biological effects of cytokines, its downstream target(s) associated with cell growth control is largely unknown. In a human interleukin-3 (IL-3)-dependent cell line F-36P-mpl, the induced expression of dominant-negative (dn)-STAT5 and of dn-ras led to inhibition of IL-3-dependent cell growth, accompanying the reduced expression of cyclin D1 mRNA. Also, both constitutively active forms of STAT5A (1*6-STAT5A) and ras (H-rasG12V) enabled F-36P-mpl cells to proliferate without added growth factors. In NIH 3T3 cells, 1*6-STAT5A and H-rasG12V individually and cooperatively transactivated the cyclin D1 promoter in luciferase assays. Both dn-STAT5 and dn-ras suppressed IL-3-induced cyclin D1 promoter activities in F-36P-mpl cells. Using a series of mutant cyclin D1 promoters, 1*6-STAT5A was found to transactivate the cyclin D1 promoter through the potential STAT-binding sequence at -481 bp. In electrophoretic mobility shift assays, STAT5 bound to the element in response to IL-3. Furthermore, the inhibitory effect of dn-STAT5 on IL-3-dependent growth was restored by expression of cyclin D1. Thus STAT5, in addition to ras signaling, appears to mediate transcriptional regulation of cyclin D1, thereby contributing to cytokine-dependent growth of hematopoietic cells. (+info)
Multicenter phase III trial to evaluate CD34(+) selected versus unselected autologous peripheral blood progenitor cell transplantation in multiple myeloma.
(20/11748)
High-dose chemotherapy followed by autologous transplantation has been shown to improve response rates and survival in multiple myeloma and other malignancies. However, autografts frequently contain detectable tumor cells. Enrichment for stem cells using anti-CD34 antibodies has been shown to reduce autograft tumor contamination in phase I/II studies. To more definitively assess the safety and efficacy of CD34 selection, a phase III study was completed in 131 multiple myeloma patients randomized to receive an autologous transplant with either CD34-selected or unselected peripheral blood progenitor cells after myeloablative therapy. Tumor contamination in the autografts was assessed by a quantitative polymerase chain reaction detection assay using patient-specific, complementarity-determining region (CDR) Ig gene primers before and after CD34 selection. A median 3.1 log reduction in contaminating tumor cells was achieved in the CD34 selected product using the CEPRATE SC System (CellPro, Inc, Bothell, WA). Successful neutrophil engraftment was achieved in all patients by day 15 and no significant between-arm difference for time to platelet engraftment occurred in patients who received an infused dose of at least 2.0 x 10(6) CD34(+) cells/kg. In conclusion, this phase III trial demonstrates that CD34-selection of peripheral blood progenitor cells significantly reduces tumor cell contamination yet provides safe and rapid hematologic recovery for patients receiving myeloablative therapy. (+info)
Transduction of primitive human marrow and cord blood-derived hematopoietic progenitor cells with adeno-associated virus vectors.
(21/11748)
We evaluated the capacity of adeno-associated virus (AAV) vectors to transduce primitive human myeloid progenitor cells derived from marrow and cord blood in long-term cultures and long-term culture-initiating cell (LTC-IC) assays. Single-colony analyses showed that AAV vectors transduced CD34(+) and CD34(+)38(-) clonogenic cells in long-term culture. Gene transfer was readily observed in LTC-ICs derived from 5-, 8-, and 10-week cultures. Recombinant AAV (rAAV) transduction was observed in every donor analyzed, although a wide range of gene transfer frequencies (5% to 100%) was noted. AAV transduction of LTC-ICs was stable, with week-8 and -10 LTC-ICs showing comparable or better transduction relative to week-5 LTC-ICs. Fluorescence in situ hybridization (FISH) analyses performed to determine the fate of AAV vectors in transduced cells showed that 9% to 28% of CD34(+) and CD34(+)38(-) cells showed stable vector integration as evidenced by chromosome-associated signals in metaphase spreads. Comparisons of interphase and metaphase FISH suggested that a fraction of cells also contained episomal vector at early time points after transduction. Despite the apparent loss of the episomal forms with continued culture, the number of metaphases containing integrated vector genomes remained stable long term. Transgene transcription and placental alkaline phosphatase (PLAP) expression was observed in CD34(+), CD34(+)38(-) LTC-ICs in the absence of selective pressure. These results suggest that primitive myeloid progenitors are amenable to genetic modification with AAV vectors. (+info)
Genetically corrected autologous stem cells engraft, but host immune responses limit their utility in canine alpha-L-iduronidase deficiency.
(22/11748)
Canine alpha-L-iduronidase (alpha-ID) deficiency, a model of the human storage disorder mucopolysaccharidosis type I (MPS I), is an ideal system in which to evaluate the clinical benefit of genetically corrected hematopoietic stem cells. We performed adoptive transfer of genetically corrected autologous hematopoietic cells in dogs with alpha-ID deficiency. Large volume marrow collections were performed on five alpha-ID-deficient dogs. Marrow mononuclear cells in long-term marrow cultures (LTMCs) were exposed on three occasions during 3 weeks of culture to retroviral vectors bearing the normal canine alpha-ID cDNA. Transduced LTMC cells from deficient dogs expressed enzymatically active alpha-ID at 10 to 200 times the levels seen in normal dogs. An average of 32% of LTMC-derived clonogenic hematopoietic cells were provirus positive by polymerase chain reaction and about half of these expressed alpha-ID. Approximately 10(7) autologous gene-modified LTMC cells/kg were infused into nonmyeloablated recipients. Proviral DNA was detected in up to 10% of individual marrow-derived hematopoietic colonies and in 0.01% to 1% of blood and marrow leukocytes at up to 2 to 3 years postinfusion. Despite good evidence for engraftment of provirally marked cells, neither alpha-ID enzyme nor alpha-ID transcripts were detected in any dog. We evaluated immune responses against alpha-ID and transduced cells. Humoral responses to alpha-ID and serum components of the culture media (fetal bovine and horse sera and bovine serum albumin) were identified by enzyme-linked immunosorbent assay. Cellular immune responses to autologous alpha-ID but not neo(r) transduced cells were demonstrated by lymphocyte proliferation assays. To abrogate potential immune phenomena, four affected dogs received posttransplant cyclosporine A. Whereas immune responses were dampened in these dogs, alpha-ID activity remained undetectable. In none of the dogs engrafted with genetically corrected cells was there evidence for clinical improvement. Our data suggest that, whereas the alpha-ID cDNA may be transferred and maintained in approximately 5% of hematopoietic progenitors, the potential of this approach appears limited by the levels of provirally derived enzyme that are expressed in vivo and by the host's response to cultured and transduced hematopoietic cells expressing foreign proteins. (+info)
Hematopoietic stem cell tracking in vivo: a comparison of short-term and long-term repopulating cells.
(23/11748)
We have previously demonstrated that we could separate long-term repopulating stem cells from cells that provided radioprotection (short-term repopulating cells) on the basis of size and suggested that this might be due to the quiescent nature of long-term repopulating cells. To further define the activity of these populations, we used a dye (PKH26), which incorporates into the membrane of cells and is equally distributed to daughter cells when they divide. We developed an assay, which allowed us to retrieve PKH26(+) long-term and short-term repopulating cells in the hematopoietic tissues of the recipients posttransplant. We were able to recover the labeled cells and determine their cell cycle activity, as well as their ability to reconstitute secondary lethally irradiated hosts in limiting dilution. The results of our assay suggest that long-term repopulating cells are quiescent in the bone marrow (BM) 48 hours after transplant. We were able to detect only a few labeled cells in the peripheral blood posttransplant and even though cells homed to both the spleen and BM, more long-term repopulating cells homed to the marrow and only these cells, which homed to the marrow, were capable of reconstituting lethally irradiated secondary hosts long-term. (+info)
A novel spliced form of SH2-containing inositol phosphatase is expressed during myeloid development.
(24/11748)
SH2-containing Inositol Phosphatase (SHIP) is a 145 kD protein expressed in hematopoietic cells. SHIP is phosphorylated on tyrosine after receptor binding by several cytokines and has a negative role in hematopoiesis. We cloned a murine complementary DNA (cDNA) sequence for an isoform of SHIP with an internal 183 nucleotide deletion, encoding a protein 61 amino acids shorter than 145 kD SHIP. This deletion eliminates potential SH3-domain binding regions and a potential binding site for the p85 subunit of Phosphatidylinositol 3-Kinase. Using polyclonal anti-SHIP antibodies, we and others have previously observed a 135 kD SHIP isoform that is coexpressed with 145 kD SHIP. Here, we used monoclonal antibodies raised against the region deleted in the spliced form to show that the product of the novel spliced SHIP cDNA is antigenically identical to the 135 kD SHIP isoform. Like 145 kD SHIP, 135 kD SHIP expression was induced on differentiation of bone marrow cells. After macrophage colony-stimulating factor (M-CSF) stimulation of FDC-P1(Fms) myeloid cells, both 145 and 135 kD SHIP forms were tyrosine phosphorylated and could be coimmunoprecipitated with antibodies to Shc and Grb2. However, experiments showed only a weak association of 135 kD SHIP with p85. A potentially analogous 135 kD SHIP species also appears in human differentiated leukocytes. (+info)