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T M Dexter

Publications and source records attributed to T M Dexter.

At least 73 records · Page 4Linked to original sources
PubMed1995

Multicyclic, dose-intensive chemotherapy supported by sequential reinfusion of hematopoietic progenitors in whole blood.

PURPOSE: To support multicyclic, dose-intensive chemotherapy, we assessed the effects of reinfusing hematopoietic progenitors collected at each cycle in leukapheresis product or whole blood. PATIENTS AND METHODS: Twenty-five patients with small-cell lung cancer (SCLC) were treated with six cycles of ifosfamide, carboplatin, and etoposide (ICE) with granulocyte colony-stimulating factor (G-CSF) 300 micrograms/d subcutaneously (SC) on days 4 to 15. Hematopoietic progenitors collected during each cycle were reinfused on day 3 of the next cycle. Cohort 1 (n = 6) was treated every 3 weeks, with leukapheresis after 2 weeks and cryopreservation of the leukapheresis product. Chemotherapy was given if the WBC count was > or = 3 x 10(9)/L and platelet count > or = 100 x 10(9)/L. Cohort 2 (n = 7) was treated every 2 weeks, with leukapheresis on day 1 of the next cycle and storage of the leukapheresis product at 4 degrees C. Cohort 3 (n = 12) was treated every 2 weeks, with 500 to 750 mL of blood drawn by venesection on day 1 of the next cycle and stored at 4 degrees C. In cohorts 2 and 3, chemotherapy was given if the WBC count was > or = 3 x 10(9)/L and platelet count > or = 30 x 10(9)/L. Blood and leukapheresis products were assayed for hematopoietic progenitors. RESULTS: ICE chemotherapy with G-CSF was effective in mobilizing blood progenitors (median, 120-fold). Long-term cultures showed no evidence of stem-cell depletion. The cytotoxic dose-intensity of standard every-4-weeks ICE is 100%. In the first three cycles, it was 134% (median) in cohort 1 and 200% in cohorts 2 and 3 (P < .0001). Toxicity and supportive care requirements were not increased. CONCLUSION: The dose-intensity of ICE chemotherapy can be doubled by reinfusing hematopoietic progenitors collected by leukapheresis or venesection and stored at 4 degrees C.

Adult↗
PubMed1995

Macrophage inflammatory protein-1 alpha mediated growth inhibition in a haemopoietic stem cell line is associated with inositol 1,4,5 triphosphate generation.

Macrophage Inflammatory Protein-1 alpha (MIP-1 alpha) can inhibit the proliferation of multipotent haemopoietic cells. Using the FDCP-Mix A4 multipotent stem cell line, MIP-1 alpha was shown to inhibit 1L-3 stimulated cell cycling (assessed using the [3H]-thymidine "suicide" assay). Furthermore, MIP-1 alpha can inhibit 1L-3-stimulated [3H]-thymidine incorporation in FDCP-Mix cells, with half maximal inhibition observed at 3 ng/ml MIP-1 alpha. Prostaglandin E2, but not MIP-1 alpha was able to elevate cyclic AMP levels in FDCP-Mix A4 cells although both agents can cause growth inhibition. However, MIP-1 alpha addition resulted in a pertussis-toxin-insensitive increase in the level of the second messenger inositol 1,4,5 triphosphate (Ins 1,4,5P3). This response was both rapid (maximal at 5 seconds) and transient. A half maximal effect was observed at 5 ng/ml MIP-1 alpha and the dose dependency correlated with that for MIP-1 alpha mediated growth inhibition. A rapid increase in cytosolic Ca2+ levels was also observed in response to MIP-1 alpha. Inositol lipid hydrolysis and an increase in cytosolic Ca2+ (signals normally associated with proliferation) may therefore be implicated in growth inhibitory mechanisms in multipotent cells.

Animals↗
PubMed1995

The Hox-2.4 gene is not involved in the generation of IL-3 dependent multipotent FDCP-mix cell lines.

The establishment of IL-3-dependent multipotent progenitor cell lines from Hox-2.4-expressing bone marrow cells suggests that homeobox genes may contribute to immortalization of early myeloid cells. A survey of 20 independently derived multipotent IL-3-dependent cell lines established from either src-virus-infected long-term bone marrow cultures (FDCP-mix) or Multi-CSF-virus (M3MuV)-infected bone marrow revealed that Hox-2.4 was not expressed in any of these cell lines. In addition DNA rearrangements were not observed. We conclude that activation of Hox-2.4 is not an obligatory event in the immortalization of early myeloid cells.

Animals↗
PubMed1995

[The effect of GM-CSF/IL-3 on the grafting efficiency of CD34+ hemopoietic progenitor cells from umbilical cord blood].

CD34+ cells were isolated from human umbilical cord blood by using a high-gradient magnetic cell sorting system with anti-CD34 monoclonal antibody coated with microbeads, and then inoculated onto a pre-formed irradiated bone marrow stroma to evaluate the grafting efficiency of CD34+ cells with rhGM-CSF or IL-3, alone or in combination. The results showed that only 36% CD34+ cells in the control, and 68 - 89.6% in the groups with growth factors treatment seeded to the stroma. A short incubation of CD34+ cells with growth factors could rapidly reconstitute a long-term hemopoiesis in the long-term liquid culture system. This demonstrates that a brief treatment of CD34+ cells with GM-CSF or IL-3 can improve the grafting efficiency of transplanted umbilical cord blood cells.

Adult↗
PubMed1994

Direct comparison by limiting dilution analysis of long-term culture-initiating cells in human bone marrow, umbilical cord blood, and blood stem cells.

Limiting-dilution analysis of long-term culture-initiating cells (LTCIC) is a quantitative method of estimating hematopoietic stem cell activity in clinical samples. We compared the numbers of LTCIC in bone marrow (BM), umbilical cord blood, and blood progenitor cells (obtained from patients with solid tumors at leukapheresis after mobilization with induction chemotherapy and filgrastim administration), using a two-stage long-term culture system and a limiting-dilution technique, scoring cobblestone areas of greater than 15 hematopoietic cells weekly for up to 8 weeks. Samples were obtained from 30 normal BMs, 20 human umbilical cords, and 32 leukapheresis products. Direct comparison of LTCIC in the three sources showed that the median proportions of cells generating hematopoietic foci from unfractionated mononuclear cells at 5 and 8 weeks, respectively, were 1:13,314 and 1:33,949 for BM, 1:12,506 and 1:34,546 for umbilical cord blood, and 1:10,302 and 1:12,891 for leukapheresis product. The estimated proportions of LTCIC from unfractionated mononuclear cells and CD34+ cells were similar in experiments with leukapheresis product. Leukapheresis product was superior to umbilical cord blood and cord blood to BM at 5 and 8 weeks of culture (P = .01). In two-stage long-term cultures, more colonies per flask and CD34+ cells were found in assays of leukapheresis product than in BM or umbilical cord blood cultures (P = .0005). Results obtained by this simplified limiting-dilution analysis correlated well with standard long-term cultures and can be used as a measure of the stem cell population. These data suggest that the incidence of putative stem cells in leukapheresis product and umbilical cord blood are at least comparable with that of BM.

Antigens, CD↗
PubMed1994

Apoptosis in the haemopoietic system.

Our previous studies have shown that haemopoietic stem cells undergo apoptotic death as a consequence of growth factor withdrawal. In this paper we review the new data that has accumulated since this observation and compare it with older data from the 'pre-apoptotic' age. Models of erythropoiesis and granulopoiesis that incorporate apoptosis as a normal physiological process controlling homeostasis are examined. The converse to cell death is cell survival, and we describe experiments which suggest that haemopoietic growth factors can not only act as mitogenic or differentiation stimuli but also act as survival signals. We, and others, have proposed that these growth factor-induced survival signals act through the membrane bound polypeptide receptors and share common features of signal transduction with proliferative responses. Enforced expression of bcl-2 in haemopoietic stem cells is able to overcome apoptosis following the withdrawal of growth factor, and the cells commit into different lineage differentiation programmes. Such cells spontaneously differentiate without cell division, suggesting a stochastic model of haemopoiesis in which the major role of haemopoietic growth factors is to suppress apoptosis and act as mitogens. We review the evidence that the underlying causes of some haematological diseases may be associated with change in the balance between cell survival and death.

Animals↗
PubMed1994

Total marrow failure induced by pegylated stem-cell factor administered before 5-fluorouracil.

To examine the potential role of stem-cell factor (SCF) in cancer chemotherapy, we have administered it to mice either before or after 5-fluorouracil (5-FU). When polyethylene glycolated (PEG-ylated) SCF was administered to mice before 5-FU, it had a significant sensitizing effect on primitive bone marrow cells. Examination of the hematopoietic status of these mice showed that the damage caused by 5-FU to both bone marrow and spleen hematopoiesis was exaggerated when it was preceded by SCF. SCF given before each of two 5-FU treatments at 7-day intervals resulted in the death of all treated mice. The time of death and hematopoietic status of these animals are compatible with the onset of hypoplastic marrow failure leading to pancytopenia and death. SCF given after 5-FU had little impact either on the initial degree of hematopoietic damage or subsequent recovery. Gut populations were similarly sensitized to 5-FU by prior treatment with SCF, and the damage caused to intestinal populations was greater than that resulting from 5-FU alone. This indicates that the different tissues may be similarly sensitized by SCF. The sensitizing effect of SCF was reversed by concurrent administration of transforming growth factor (TGF)-beta 3, and survival of the majority of the mice was ensured. Examination of hematopoiesis in mice treated concurrently with SCF and TGF-beta 3 showed that the degree of marrow and spleen damage had reverted to that caused by 5-FU alone. In further experiments, 100% survival and normal hematopoiesis could be attained by transplantation of 1 million syngeneic bone marrow cells 24 hours after 5-FU treatment following SCF sensitization. These data indicate that PEG-ylated SCF can sensitize normally resistant hematopoietic and gut stem cells to the effects of 5-FU. This sensitization resulted in effective eradication of hematopoiesis in SCF-pretreated/5-FU-treated animals and their subsequent death from marrow failure. These findings imply that SCF pretreatment may represent a novel method of increasing the effectiveness of conventional chemotherapy, making marrow ablation more effective without drug dose escalation and perhaps sensitizing some tumor cells to the effects of therapy.

Animals↗
PubMed1994

bcl-2 delay of alkylating agent-induced apoptotic death in a murine hemopoietic stem cell line.

Many cytotoxic agents kill cells by invoking a specific death pathway termed physiological cell death, or apoptosis. Treatment of a murine hemopoietic stem cell line, FDCP-mix, with methylmethanesulfonate (MMS) or N'-methyl-N'-nitrosourea (MNU) leads to death by apoptosis. Retroviral gene transfer was used to overexpress the bcl-2 oncogene in FDCP-mix cells, and this was associated with a delay in apoptosis in these cells after treatment with MNU and MMS and decreased sensitivity of colony formation to the cytotoxic effects of MMS. These data suggest an explanation for the refractory nature of bcl-2-expressing follicular lymphoma to cytotoxic chemotherapy and furthermore suggest that DNA-damaging antitumor therapy may contribute to the progression of disease.

Animals↗
PubMed1994

Growth factors and the molecular control of haematopoiesis.

In the absence of appropriate growth factors, for example interleukin-3 or GM-CSF, cultured bone marrow stem cells die by a process known as apoptosis or programmed cell death. Apoptosis may occur in vivo when concentrations of specific growth factors are limiting and may be a means of regulating cell numbers. Growth factors are also essential for proliferation of bone marrow stem cells but differentiation can occur, provided there is a survival stimulus in the absence of growth factors. Combinations of growth factors may be synergistic in stimulating the survival and proliferation of multipotent stem cells. Although neither stem cell factor, nor GM-CSF alone can significantly induce the proliferation of stem cells, the combination induces the proliferation of these cells. Committed progenitor cells such as granulocyte-macrophage colony-forming cells, however, are stimulated to proliferate by GM-CSF alone, while stem cell factor in combination with GM-CSF results in only a slight additive effect. To date, most research has concentrated on the growth stimulatory factors. GM-CSF has an important role in the reversal of chemotherapy-induced myelosuppression in cancer patients and in other bone marrow disorders. A number of growth inhibitory molecules have now been identified, such as macrophage inhibitory protein-1 alpha. In the future, it is possible that improvements in cure rates may be achieved in cancer patients by combining the growth inhibitory factors with the stimulatory factors. Inhibitory factors may be given before chemotherapy to prevent toxicity and stimulatory factors may be given afterwards to treat neutropenic patients.

Cell Differentiation↗
PubMed1994

Cytokine-mediated protein kinase C activation is a signal for lineage determination in bipotential granulocyte macrophage colony-forming cells.

Granulocyte macrophage colony-forming cells (GM-CFC) have the potential to develop into either macrophages and/or neutrophils. With a highly enriched population of these cells we have found that although GM-CFC are equally responsive to macrophage colony stimulating factor (M-CSF) and stem cell factor (SCF) in terms of DNA synthesis, M-CSF stimulated the development of colonies containing macrophages in soft gel assays, while SCF promoted neutrophilic colony formation. When SCF and M-CSF were combined, mainly macrophage development was stimulated both in soft agar colony-forming assays and liquid cultures. An analysis of some potential signaling mechanisms associated with cytokine-mediated developmental decisions in GM-CFC revealed that M-CSF, but not SCF, was able to chronically stimulate phosphatidylcholine breakdown and diacylglycerol production, indicating that protein kinase C (PKC) may be involved in the action of M-CSF. Furthermore, M-CSF, but not SCF, can increase the levels of PKC alpha (PKC alpha) expression and stimulate the translocation of PKC alpha to the nucleus. When the PKC inhibitor, calphostin C, was added to GM-CFC cultured in M-CSF then predominantly neutrophils were produced, conversely PKC activators added with SCF stimulated macrophage development. The data indicate a role for PKC in M-CSF-stimulated macrophage development from GM-CFC.

Animals↗
PubMed1994

A reliable approach for sequencing clone-specific CDRIII regions in B-cell lymphoma.

We report a reliable approach for sequencing lymphoma-specific CDRIII regions. CDRIII regions present in DNA prepared from routinely fixed and paraffin-embedded diagnostic lymph node material were amplified by the use of consensus VH and JH primers via PCR. PCR products were subcloned directly, without purification or modification of PCR fragments. Only small amounts of miniprep plasmid DNA of recombinant clones were required for cycle sequencing, resulting in autoradiograms of high quality. The easy and reproducible method which we describe has enabled us to determine the lymphoma-specific CDRIII region in 7/11 high-grade non-Hodgkin's lymphomas as well as in 3/3 cases of ALL and 1/1 case of a centroblastic/centrocytic lymphoma. The obtained sequence data can serve to generate lymphoma-specific oligonucleotides, which then can be used as PCR primers or hybridization probes for the detection of minimal residual disease in individual patients.

Base Sequence↗
PubMed1994

Dose-escalating induction chemotherapy supported by lenograstim preceding high-dose consolidation chemotherapy for advanced breast cancer. Selection of the most acceptable regimen to induce maximal tumor response and investigation of the optimal time to collect peripheral blood progenitor cells for haematological rescue after high-dose consolidation chemotherapy.

BACKGROUND: In advanced breast cancer high-dose consolidation chemotherapy with haematological rescue has resulted in prolonged disease free and overall survival in a small percentage of patients. Maximal reduction of the tumor burden by intensive induction treatment preceding the high-dose chemotherapy may favor that outcome. The aims of this study were to find a rapid highly effective induction regimen with acceptable toxicity and to examine the optimal time for peripheral blood progenitor cell (PBPC) collection for haematological rescue. SUBJECTS AND METHODS: Twenty-four patients received 4 cycles of FAC chemotherapy (5-FU, adriamycin, cyclosphamide), each followed by 10 micrograms/kg/d of lenograstim (glycosylated rHuG-CSF) s.c. day 2 to 11. Chemotherapy was administered at 4 dose intensity levels with 6 patients including at each level (level 1: 500(F)/50(A)/500(C) mg/m2/3wk, level 2: 500/50/500 mg/m2/2wk, level 3: 500/75/500 mg/m2/2wk, m2/2wk, level 4: 500/75/1000 mg/m2/2wk d1 i.v.). In addition lenograstim (10 micrograms/kg/d s.c.) was administered for a period of 10 days before (period X) and after (period Y) chemotherapy. In 16 patients (4 at each dose intensity level) assessment of PBPC was performed during period X and Y as well as during cycle 1 and 4. A single apheresis to collect PBPC was planned during chemotherapy cycle 1. RESULTS: The best response was obtained at dose intensity level 3 (all 6 patients responded, 3 of them achieved CR) with acceptable toxicity. Peak circulating numbers of total CFC/ml blood were median 5819 (period X), 4635 (cycle 1), 3807 (cycle 4) and 3519 (period Y) and occurred concurrently with peak circulating numbers of CD34+ cells. The and median 3.76 x 10(6)/kg CD34+ cells. Three patients received high-dose consolidation chemotherapy with PBPC support. Recovery of ANC > 0.5 x 10(9)/l occurred on median day 11 and of platelets > 20 x 10(9)/l on median day 10. CONCLUSION: Dose intensity level 3 is the best usable induction regimen in this study. The optimal time for apheresis is either during lenograstim before chemotherapy treatment or during the first cycle of chemotherapy. Rapid haematological recovery was obtained by reinfusion of PBPC as sole source of support in the patients receiving high-dose consolidation chemotherapy.

Adult↗
PubMed1994

Granulocyte colony stimulating factor: from laboratory bench to clinical use.

A great deal has been learned about haematopoiesis since the discovery, purification and cloning of haemopoietic growth factors. The function of these growth factors is to promote survival and enhance mitosis (at higher concentrations), and influence differentiation and development of stem cells and progenitor cells. The type of mature cells produced reflects the combinations of growth factors to which the stem cells are exposed. Growth factors may also control the functional activity of mature cells. Treatment with granulocyte colony stimulating factor (G-CSF) produces neutrophils that are at least equivalent to those produced during normal haematopoiesis and does not appear to deplete the haematopoietic stem or progenitor cell populations.

Animals↗
PubMed1994

Viability of haemopoietic progenitors from whole blood, bone marrow and leukapheresis product: effects of storage media, temperature and time.

High-dose cytotoxic chemotherapy can be supported with autologous haemopoietic cells. Cryopreserved bone marrow has conventionally been used for this but blood stem cells are now in common use. We have examined different storage conditions for haemopoietic cells from bone marrow, leukapheresis product and whole blood primed with chemotherapy and filgrastim. The mean number of GM-CFC surviving cryopreservation was 80% in leukapheresis product (95% CI 66-96). At 4 degrees C, GM-CFC viability in all three sources of haemopoietic progenitors declined at the same rate, with mean recovery at 24 h of 90% (95% CI 82-98), at 48 h of 68% (95% CI 61-75) and at 72 h of 47% (95% CI 40-53). Progenitors remained viable for longer in autologous serum and citrate phosphate dextrose or Iscove's medium than in phosphate buffered saline. There was no significant difference in GM-CFC recovery from whole blood or whole blood buffy layer at 4 degrees C. The capacity to generate and sustain haemopoiesis in long-term culture is a feature of the more primitive progenitor cells. This capacity was similar in cryopreserved bone marrow and leukapheresis product, cryopreserved or stored for up to 5 days at 4 degrees C, suggesting that long-term culture-initiating cells are more resilient than colony-forming cells when cryopreserved or stored at 4 degrees C. These data indicate that primed whole blood, in addition to leukapheresis product and bone marrow, could be stored at 4 degrees C and used to support multicyclic high-dose chemotherapy.

Blood Cells↗
PubMed1994

Combinations of colony-stimulating factors promote enhanced proliferative potential in enriched granulocyte-macrophage colony-forming cells.

The effects of combinations of colony-stimulating factors (CSFs) have been assessed using a highly enriched population of murine granulocyte-macrophage colony-forming cells (GM-CFC). Unlike the situation observed with more primitive myeloid progenitor cells, little or no effect on the numbers of colonies formed from GM-CFC in response to specific combinations of growth factors was observed; however, the size of the majority of colonies formed was greatly increased. The largest increase in the number of cells per colony was observed when interleukin-3 (IL-3) was present with either granulocyte-macrophage colony-stimulating factor (GM-CSF), GM-CSF plus granulocyte-colony-stimulating factor (G-CSF), or macrophage colony-stimulating factor (M-CSF); there was a > five-fold increase when compared to colony size in the presence of IL-3 alone. The combination of G-CSF with IL-3 was not able to promote an increase in mean colony size; however, G-CSF plus GM-CSF did give a significant increase. Where combinations of hematopoietic growth factors led to increased numbers of cells per colony, the delayed addition of one of the cytokines to soft gel assays for a period > 2 days led to a loss of the observed enhancement in the number of cells per colony. In cultures of progenitor cells enriched by centrifugal elutriation and that contained combinations of CSFs, there was an increase in the number of GM-CFC over a 2-day incubation period. The distinct effects observed with GM-CSF, IL-3, and G-CSF on GM-CFC suggest that they influence different molecular signaling mechanisms within common target progenitor cells.

Bone Marrow Cells↗
PubMed1994

Mutants of a multipotent hematopoietic cell line blocked in GM-CSF-induced differentiation are leukemogenic in vivo.

FDCP-Mix cells infected with a retroviral vector expressing the GM-CSF gene (GMV-FDCP-Mix) self-renew in the presence of interleukin-3 (IL-3), are multipotent, and undergo differentiation into granulocytes and macrophages coupled with clonal extinction after removal of IL-3. Mutants of GMV-FDCP-Mix were isolated that escape clonal extinction after differentiation induction by the autocrine secreted GM-CSF. Some of these mutant clones have a blast cell morphology and are blocked in differentiation, whereas others exhibit all stages of granulocyte and macrophage differentiation without clonal extinction. In contrast to the parental GMV-FDCP-Mix cells, all the mutants tested were leukemogenic when injected into syngeneic mice. Depending on the in vitro differentiation capacity of the transplanted mutant cell lines, the animals developed undifferentiated blast cell leukemias or CML-like syndromes. Thus, these mutant cell lines can be used to define the cooperating steps in autocrine myeloid leukemia.

Animals↗