Recovery Of Clonogenic Cells Research Articles

Hypoxia Up-regulates HIF Expression While Suppressing Cell Growth and NOTCH Activity in Leukaemia Cells.

To examine the influence of hypoxia on the in vitro growth of leukaemia cells and the activity of signalling proteins to better understand the pathophysiology of leukaemia cells in human bone marrow. Six human leukaemia cell lines were cultured under normoxic or hypoxic conditions. Cell growth, recovery of clonogenic cells, and the expression and activation of various signalling proteins were examined. Hypoxia suppressed cell growth and the recovery of clonogenic cells. Moreover, hypoxia up-regulated hypoxia-inducible factor (HIF) 1α and HIF2α expression while suppressing the expression and activation of NOTCH1, mechanistic target of rapamycin kinase (mTOR) activation, and nuclear factor-kappa B (NF-κB) phosphorylation. We found that hypoxia up-regulated HIF expression while it suppressed the self-renewal capacity of leukaemia cells, NOTCH activity, and expression of its down-stream signalling molecules, which differs from previous reports mentioning that HIF activates NOTCH signalling. Our findings serve to further elucidate the in vivo pathophysiology of leukaemia cells.

Bone marrow purging studies in acute myelogenous leukemia using the recombinant anti-CD33 immunotoxin HuM195/rGel

This study was designed to determine the effect of immunotoxin HuM195/rGel on normal human bone marrow before clinical purging. HuM195/rGel is composed of the recombinant plant toxin gelonin (rGel) chemically coupled to the anti-CD33 human chimeric antibody HuM195. The CD33 antigen is of significant interest as a target for therapy of acute myelogenous leukemia because it is present in leukemic blasts of most patients but absent in the earliest progenitor bone marrow cells. HuM195/rGel was optimally cytotoxic to acute myelogenous leukemia HL60 cells with 24 hours of exposure. We developed an in vivo purging model by mixing mobilized peripheral blood progenitor cells with HL60 cells to simulate a remission in bone marrow. Cells were treated with 10 nmol/L of HuM195/rGel either with or without exposure to freeze/thaw procedure, which has been reported to act synergistically with HuM195/rGel to produce cytotoxic effect. When clonogenic cell recovery rates were determined, HuM195/rGel alone did not affect normal peripheral blood progenitor cells, whereas HuM195/rGel plus freeze/thaw provided 2 logs of tumor cell elimination in our purging model. We also observed similar results under conditions used in the transplantation setting. We concluded that for acute myelogenous leukemia blasts expressing CD33, HuM195/rGel could be useful as a purging reagent for autologous transplantation.

Suppression of granulopoiesis by vesnarinone

The effects of vesnarinone (3,4-dihydro-6-[4(3,4-dimethoxybenzoyl)-1-piperanizyl]-2 (1H)-quinolinone) on the hematopoietic precursors in 5 healthy volunteers and leukemic blast progenitors in 11 acute myeloid leukemia (AML) patients, 1 chronic myelocytic leukemia patient (CML) in blast crisis, and 3 leukemic cell lines were studied in methylcellulose and suspension cultures. Normal erythroid precursors (colony-forming unit erythroid: CFU-E and burst-forming unit erythroid: BFU-E) and granulopoietic precursors (colony-forming unit granulocyte/macrophage: CFU-GM) were suppressed in methylcellulose culture by vesnarinone in a dose-dependent manner. Leukemic blast progenitors may replicate themselves and/or undergo terminal divisions with limited differentiation. The plating efficiency of primary blast colony formation (PE1) in methylcellulose, which is considered to reflect the terminal divisions of leukemic blast progenitors, was suppressed by vesnarinone in a dose-dependent manner in all cases tested. The plating efficiency of secondary blast colony-formation (PE2) in methylcellulose culture and the recovery of clonogenic cells in the suspension culture, which are considered to reflect the self-replication function of leukemic blast progenitors, were also suppressed by vesnarinone in a dose-dependent manner in all cases tested. The results suggest that vesnarinone inhibits the growth of normal and leukemic hematopoietic progenitors. To determine the mechanism by which vesnarinone inhibits hematopoiesis, the effect of the agent on apoptosis (programmed cell death) of leukemic cells was studied. DNA ladder formation was recognized in OCI/AML 1 a cells after exposure to 100 micrograms/ml vesnarinone for 18 hours; this means that vesnarinone induced apoptosis in this cell line. Therefore, vesnarinone is considered to be the cause of apoptosis of granulopoietic precursors.

Prognostic significance of the blast self-renewal capacity in patients with acute myeloid leukemia

The proliferation of leukemic cells in acute myeloid leukemia (AML) is supported by a small subpopulation of leukemic blast progenitors, which can be detected in methylcellulose and suspension cultures. It is important to determine the association between the biologic properties of leukemic blast progenitors and the clinical prognosis of patients with AML. Ninety-five patients with AML and two patients with chronic myelocytic leukemia in blast crisis were studied. T-cell depleted mononuclear cells obtained from the peripheral blood cells were cultured in both methylcellulose and suspension cultures. In methylcellulose culture, primary blast colony formation (PE1) and secondary blast colony formation (PE2) were enumerated. The recovery of clonogenic cells was determined in suspension culture. The association between PE1, PE2, or clonogenic cell recovery in suspension and the remission induction outcome or survival duration of the patients were examined. PE1 was not associated with the remission induction outcome. PE2 and clonogenic cells recovered in suspension were significantly associated with the remission induction. Furthermore, the survival duration of the patients who achieved complete remission was associated significantly with the number of clonogenic cells recovered in suspension. PE1 reflects the terminal divisions of leukemic blast progenitors, whereas PE2 and the recovery of clonogenic cells in suspension culture are considered to reflect the self-renewal of leukemic blast progenitors. The results suggest that the self-renewal capacity of leukemic blast progenitors is predictive of not only remission induction outcome but also survival duration of patients with AML.

Automated processing of human bone marrow grafts for transplantation.

Prior to purging or cryopreservation, we concentrated 21 bone marrow (BM) harvests using a modification of the 'grancollect-protocol' of the Fresenius AS 104 cell separator with the P1-Y set. Within 40-70 min, the initial marrow volume of 1,265 ml (+/- 537 ml) was processed two to three times. A mean of 47% (+/- 21%) of the initial mononuclear cells was recovered in a mean volume of 128 ml (+36 ml). The recovery of clonogenic cells, measured by CFU-GM assays, was 68% (+/- 47%). Red blood cells in the BM concentrates were reduced to 7% (+/- 4%) of the initial number. The procedure was efficient and yielded a BM cell fraction suitable for purging, cryopreservation and transplantation. At this time, 10 of the 21 patients whose BM was processed using this technique have been transplanted. Seven of these 10 patients have been grafted using the BM alone. Three of the 10 patients showed reduced cell viability and colony growth in the thawed BM samples, and therefore obtained BM and peripheral blood-derived stem cells. All transplanted patients showed an evaluable engraftment, achieving 1,000 granulocytes per microliter of peripheral blood in a mean of 18 days.

PROGNOSTIC IMPLICATIONS OF BLAST SELF-RENEWAL CAPACITY IN ACUTE MYELOCYTIC-LEUKEMIA

The in vitro culture studies have revealed that the infinite proliferation of leukemic cells in acute myelocytic leukemia (AML) is supported by leukemic blast progenitors with self-renewal capacity. The self-renewal of blast progenitors is assessed by either secondary blast colony-formation in methylcellulose culture or clonogenic cell recovery in suspension culture. The patients whose leukemic blast progenitors had high self-renewal ability were more difficult in achieving complete remission and survived for shorter term than those with leukemic blast progenitors of low self-renewal capacity. Namely, the self-renewal capacity of leukemic blast progenitors was highly predictive of not only remission induction outcome but also survival duration of AML patients. Among several antileukemic agents tested, only a few drugs such as cytosine arabinoside were effective against blast self-renewal. To cure AML, a therapy that aims to eradicate self-renewing leukemic blast progenitors should be developed.

Effect of recombinant human D-factor on the growth of leukemic blast progenitors from acute myeloblastic leukemia patients.

We studied the effects of D‐factor on the growth of leukemic blast progenitors from 15 patients with acute myeloblastic leukemia and two leukemia cell lines in methylcellulose and suspension cultures. When stimulated by granulocyte colony‐stimulating factor (G‐CSF), granulocyte‐macrophage colony‐stimulating factor or interleukin‐3, leukemic blast progenitors undergo terminal division with limited differentiation in methylcellulose culture, forming blast colonies. Leukemic blast progenitors can renew themselves. The self‐renewal can be detected as secondary colony formation after replating primary blast colonies in fresh methylcellulose media and by the growth of clonogenic cells in suspension culture. D‐Factor suppressed primary and secondary colony formation in methylcellulose culture. Furthermore, D‐factor suppressed clonogenic cell recovery in suspension culture. The suppression by D‐factor of the growth of leukemic blast progenitors was not significantly dependent upon the colony‐stimulating factors used as growth‐stimulating factors. High concentration of G‐CSF did not overcome the suppressive effect of D‐factor. The results indicate that D‐factor is effective in suppressing not only terminal division but also self‐renewal of leukemic blast progenitors.

Inhibition of the self-renewal capacity of blast progenitors from acute myeloblastic leukemia patients by site-selective 8-chloroadenosine 3',5'-cyclic monophosphate.

The physiologic balance between the two regulatory subunit isoforms, RI and RII, of cAMP-dependent protein kinase is disrupted in cancer cells; growth arrest and differentiation of malignant cells can be achieved when the normal ratio of these intracellular signal transducers of cAMP is restored by the use of site-selective cAMP analogs. In this study we evaluated the effects of the site-selective cAMP analog 8-chloroadenosine 3',5'-cyclic monophosphate (8-Cl-cAMP) on clonogenic growth of blast progenitors from 15 patients with acute myeloblastic leukemia and 3 patients affected by advanced myelodysplastic syndrome. Leukemic blast progenitors undergo terminal divisions, giving rise to colonies in methylcellulose. The self-renewal capacity of blast progenitors is conversely reflected in a secondary methylcellulose assay after exponential growth of clonogenic cells in suspension cultures. In all the samples tested, 8-Cl-cAMP, at micromolar concentrations (0.1-50 microM), suppressed in a dose-dependent manner both primary colony formation in methylcellulose and the recovery of clonogenic cells from suspension culture. Strikingly, in the samples from the entire group of patients, 8-Cl-cAMP was more effective in inhibiting the self-renewing clonogenic cells than the terminally dividing blast cells (P = 0.005). In addition, in four out of six cases studied, 8-Cl-cAMP was able to induce a morphologic and/or immunophenotypic maturation of leukemic blasts. An evident reduction of RI levels in fresh leukemic cells after exposure to 8-Cl-cAMP was also detected. Our results showing that 8-Cl-cAMP is a powerful inhibitor of clonogenic growth of leukemic blast progenitors by primarily suppressing their self-renewal capacity indicate that this site-selective cAMP analog represents a promising biological agent for acute myeloblastic leukemia therapy in humans.

Bone marrow processing with the Fresenius AS 104: initial results.

Prior to purging, cryopreservation, or ABO-incompatible bone marrow (BM) transplantation, we have concentrated 23 BM harvests using a modification of the "grancollect-protocol" and the recently available bone marrow stem cell (BMSC) protocol of the Fresenius AS 104 cell separator with the P1-Y set. Within 40-70 minutes, the initial marrow volume of 922 ml (+/- 408 ml) was processed two to three times. A mean of 59% (+/- 20%) of the initial mononuclear cells was recovered in a mean volume of 119 ml (+/- 31 ml). The recovery of clonogenic cells, measured by CFU-GM assays, was 98% (+/- 80%). Red blood cells in the BM concentrates were reduced to 8% (+/- 4%) of the initial number. The procedure was efficient and yielded a BM cell fraction suitable for purging, cryopreservation, and transplantation. All transplanted patients showed fast and sustained engraftments after autologous or allogeneic BM transplantation.

Studies of allogeneic bone marrow and spleen cell transplantation in a murine model using ultraviolet-B light

Ultraviolet irradiation inhibits alloreactive and mitogen-induced responses and might reduce both graft-versus-host and host-versus-graft reactions after bone marrow transplantation (BMT). We have studied proliferative responses to mitogens and reactivity in mixed lymphocyte culture after irradiation with ultraviolet (UV)-B light using splenocytes from Balb/c (H-2d) and CBA (H-2k) mice. Response to mitogens and in MLC was strongly inhibited by 20 J/m2 and abolished at 50 J/m2. Clonogenic cell recovery (CFU-GM; CFU-S) after UV-B irradiation was also reduced. When bone marrow and spleen cells were transplanted from parent (Balb/c) animals into F1 hybrid (Balb/c X CBA) recipients, all animals died with features indicative of graft-versus- host disease (GVHD) in 34 days. If the grafts were first irradiated with 100 J/m2 of UV-B at a mean wavelength of 310 nm, then 76% survived to day 80 when they were killed and shown to have normal marrow cellularity. The remainder died in marrow aplasia or of GVHD. H-2 typing in a group of surviving recipients showed either donor hematopoiesis only (8 of 15), mixed allogeneic chimerism (5 of 15), or recipient type hematopoiesis (2 of 15). Higher doses (200 to 300 J/m2) were detrimental to survival with 88% of recipients dying in marrow aplasia. Syngeneic BMT in Balb/c mice showed slower hematopoietic reconstitution when the grafts were first irradiated with 100 J/m2. After BMT from Balb/c to CBA mice all recipients of unirradiated grafts died within 54 days. By contrast, after graft irradiation with 100 J/m2 survival of recipient animals to day 80 was 59%. If these grafts were treated with 50 J/m2 survival was only 26% with an increase in deaths due to GVHD. Hematopoiesis at day 80 in a group of survivors studied by Ig heavy chain allotyping indicated donor type hematopoiesis in 6 of 10 (50 J/m2) and 2 of 9 (100 J/m2). These data indicate that UV-B irradiation inhibits lymphocyte reactivity and can prevent GVHD. However, there is clear in vitro and in vivo evidence of stem cell damage, such that autologous marrow recovery was demonstrated in a proportion of recipients. In parent----F1 UV-irradiated transplants, sustained hematopoietic recovery was effected in the majority by donor stem cells.

Studies of Allogeneic Bone Marrow and Spleen Cell Transplantation in a Murine Model Using Ultraviolet-B Light

Ultraviolet irradiation inhibits alloreactive and mitogen-induced responses and might reduce both graft-versus-host and host-versus-graft reactions after bone marrow transplantation (BMT). We have studied proliferative responses to mitogens and reactivity in mixed lymphocyte culture after irradiation with ultraviolet (UV)-B light using splenocytes from Balb/c (H-2d) and CBA (H-2k) mice. Response to mitogens and in MLC was strongly inhibited by 20 J/m2 and abolished at 50 J/m2. Clonogenic cell recovery (CFU-GM; CFU-S) after UV-B irradiation was also reduced. When bone marrow and spleen cells were transplanted from parent (Balb/c) animals into F1 hybrid (Balb/c X CBA) recipients, all animals died with features indicative of graft-versus-host disease (GVHD) in 34 days. If the grafts were first irradiated with 100 J/m2 of UV-B at a mean wavelength of 310 nm, then 76% survived to day 80 when they were killed and shown to have normal marrow cellularity. The remainder died in marrow aplasia or of GVHD. H-2 typing in a group of surviving recipients showed either donor hematopoiesis only (8 of 15), mixed allogeneic chimerism (5 of 15), or recipient type hematopoiesis (2 of 15). Higher doses (200 to 300 J/m2) were detrimental to survival with 88% of recipients dying in marrow aplasia. Syngeneic BMT in Balb/c mice showed slower hematopoietic reconstitution when the grafts were first irradiated with 100 J/m2. After BMT from Balb/c to CBA mice all recipients of unirradiated grafts died within 54 days. By contrast, after graft irradiation with 100 J/m2 survival of recipient animals to day 80 was 59%. If these grafts were treated with 50 J/m2 survival was only 26% with an increase in deaths due to GVHD. Hematopoiesis at day 80 in a group of survivors studied by Ig heavy chain allotyping indicated donor type hematopoiesis in 6 of 10 (50 J/m2) and 2 of 9 (100 J/m2). These data indicate that UV-B irradiation inhibits lymphocyte reactivity and can prevent GVHD. However, there is clear in vitro and in vivo evidence of stem cell damage, such that autologous marrow recovery was demonstrated in a proportion of recipients. In parent----F1 UV-irradiated transplants, sustained hematopoietic recovery was effected in the majority by donor stem cells.

Effect of Platelet-Derived Growth Factor on the Proliferation of Blast Progenitors from Acute Myeloblastic Leukemia Patients

The effect of platelet-derived growth factor (PDGF) on self-renewal and terminal divisions of blast progenitors of acute myeloblastic leukemia was studied. The terminal divisions of blast progenitors were determined as the primary blast colony formation in methylcellulose culture; self-renewal was assessed by secondary colony formation by replating in methylcellulose and the recovery of clonogenic cells in suspension culture. PDGF neither enhanced nor suppressed primary or secondary blast colony formation in methylcellulose culture nor recovery of clonogenic cells in suspension. The results show that PDGF does not affect the self-renewal or terminal divisions of leukemic blast progenitors.

The Effects of Vincristine and Doxorubicin on the Clonogenic Cells of a Human Lung Cancer Cell Line in Methylcellulose and Suspension Culture

The effects of vincristine (VCR) and doxorubicin (DOX) on the growth of an established line of human lung cancer cells, PC9, were studied in methylcellulose and suspension cultures. The secondary colony formation in methylcellulose and recovery of clonogenic cells in suspension were considered to reflect well the self‐renewal of the clonogenic cells. When dose‐response curves were obtained for VCR and DOX, the primary clonogenic cells (PE1) were more sensitive than secondary clonogenic cells (PE2) or clonogenic cells in suspension. Repeated exposure to VCR in suspension did not inhibit the exponential growth of the clonogenic cells. These data indicated that both drugs were relatively ineffective in specifically suppressing the self‐renewal of the clonogenic cells.

Enrichment of human bone marrow aspirates for low-density mononuclear cells using a haemonetics discontinuous blood cell separator.

Isopycnic density floatation centrifugation has been proven to be a suitable technique to enrich bone marrow aspirates for clonogenic cells on a small scale. We have tested a Haemonetics semicontinuous blood cell separator in order to process large volumes of bone marrow with minimal bone marrow manipulation. The efficacy of isopycnic density floatation was tested in a one and a two-step procedure. Both procedures showed a recovery of about 20% of the nucleated cells and 1-2% of the erythrocytes. The enrichment of clonogenic cells in the one-step procedure appeared superior to the two-step enrichment, first separating buffy coat cells. The recovery of clonogenic cells was 70 and 50%, respectively. Repopulation capacity of the low-density cell fraction containing the clonogenic cells was excellent after autologous reinfusion (6 cases) and allogeneic bone marrow transplantation (3 cases). Fast enrichment of large volumes of bone marrow aspirates with low-density cells containing the clonogenic cells by isopycnic density floatation centrifugation can be done safely using a Haemonetics blood cell separator.

Enrichment of Human Bone Marrow Aspirates for Low-Density Mononuclear Cells Using a Haemonetics Discontinuous Blood Cell Separator

Isopycnic density floatation centrifugation has been proven to be a suitable technique to enrich bone marrow aspirates for clonogenic cells on a small scale. We have tested a Haemonetics semicontinuous blood cell separator in order to process large volumes of bone marrow with minimal bone marrow manipulation. The efficacy of isopycnic density floatation was tested in a one and a two-step procedure. Both procedures showed a recovery of about 20% of the nucleated cells and 1-2% of the erythrocytes. The enrichment of clonogenic cells in the one-step procedure appeared superior to the two-step enrichment, first separating buffy coat cells. The recovery of clonogenic cells was 70 and 50%, respectively. Repopulation capacity of the low-density cell fraction containing the clonogenic cells was excellent after autologous reinfusion (6 cases) and allogeneic bone marrow transplantation (3 cases). Fast enrichment of large volumes of bone marrow aspirates with low-density cells containing the clonogenic cells by isopycnic density floatation centrifugation can be done safely using a Haemonetics blood cell separator.