|
|
 Previous Article | Table of Contents | Next Article 
Blood, Vol. 93 No. 3 (February 1), 1999:
pp. 796-803
Apoptotic Role of Fas/Fas Ligand System in the Regulation of
Erythropoiesis
By
R. De Maria,
U. Testa,
L. Luchetti,
A. Zeuner,
G. Stassi,
E. Pelosi,
R. Riccioni,
N. Felli,
P. Samoggia, and
C. Peschle
From the Department of Hematology-Oncology, Istituto Superiore di
Sanita', Rome, Italy; the Kimmel Cancer Center, Thomas Jefferson
University, Philadelphia, PA; and the Department of Surgical,
Anatomical and Oncological Sciences, Institute of Human Anatomy,
University of Palermo, Palermo.
 |
ABSTRACT |
The possible involvement of Fas and Fas ligand (FasL) in the
regulation of erythropoiesis was evaluated. Immunohistochemistry of
normal bone marrow specimens revealed that several immature erythroblasts undergo apoptosis in vivo. Analysis of bone marrow erythroblasts and purified progenitors undergoing unilineage erythroid differentiation showed that Fas is rapidly upregulated in early erythroblasts and expressed at high levels through terminal maturation. However, Fas crosslinking was effective only in less mature
erythroblasts, particularly at basophilic level, where it induced
apoptosis antagonized by high levels of erythropoietin (Epo). In
contrast, FasL was selectively induced in late differentiating
Fas-insensitive erythroblasts, mostly at the orthochromatic stage. FasL
is functional in mature erythroblasts, as it was able to kill
Fas-sensitive lymphoblast targets in a Fas-dependent manner.
Importantly, FasL-bearing mature erythroblasts displayed a Fas-based
cytotoxicity against immature erythroblasts, which was abrogated by
high levels of Epo. These findings suggest the existence of a negative
regulatory feedback between mature and immature erythroid cells,
whereby the former cell population might exert a cytotoxic effect on
the latter one in the erythroblastic island. Hypothetically, this
negative feedback operates at low Epo levels to moderate the
erythropoietic rate; however, it is gradually inhibited at increasing
Epo concentrations coupled with enhanced erythrocyte production. Thus,
the interaction of Fas and FasL may represent an apoptotic control
mechanism for erythropoiesis, contributing to the regulation of red
blood cell homeostasis.
© 1999 by The American Society of Hematology.
| |
INTRODUCTION |
ERYTHROPOIESIS IS A multistep process
involving the differentiation of pluripotent hematopoietic stem cells
through the lineage-committed burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E) progenitor cells, which give
rise to a series of early and late erythroblasts, eventually leading to
the formation of reticulocytes and mature erythrocytes.1
During this process, the sequential formation of proerythroblasts,
basophilic, polychromatophilic, and orthochromatic erythroblasts is
positively regulated by erythropoietin (Epo), a glycoprotein hormone
produced by the kidney in response to tissue hypoxia.2 Epo
displays multiple positive effects on early erythroblasts, including
increased proliferation, progression through maturation, and protection
from programmed cell death.3,4 Because of the low
expression of antiapoptotic genes,5 immature erythroblasts are particularly vulnerable in the absence of Epo, which has been shown
to repress apoptosis through the induction of Bcl-XL, a member of the
Bcl-2 family involved in protection from cell death in a number of
systems.6 Bcl-XL expression is very low during early
erythroid differentiation and gradually increases in intermediate and
late erythroblasts, along with the loss of Epo dependence.5 Thus, it has been proposed that the levels of Epo determine the fate of
erythroid differentiation by promoting the survival of early
erythroblasts.4,5
Fas (CD95/APO-1) is a major member of the newly characterized family of
"Death Receptors."7 Several tissues express Fas, including spleen, lymph nodes, bone marrow, heart, lung, kidney, and
ovary.8 Molecular crosslinking of Fas by its natural ligand or by agonistic antibodies results in the sequential triggering of
caspases,9 a family of aspartate-specific cysteine
proteases whose activation is required for the propagation of the
biochemical events responsible for induction of apoptotic cell
death.10 The expression and function of Fas in
hematopoietic cells directly correlate with the rate of proliferation,
suggesting a potential role for Fas and its ligand in the regulation of
hematopoietic homeostasis.11
The ligand for Fas (FasL) is a type II membrane protein predominantly
expressed by activated lymphocytes and monocytes, neutrophils, thyrocytes, and stroma cells of the retina.12-16 Moreover,
a number of other cell types can express FasL under different
pathological conditions, including hepatocytes exposed to ethanol,
macrophages infected with human immunodeficiency virus (HIV), leukemia
cells exposed to chemotherapy drugs, and several cell types following tumor transformation.17 The interaction of Fas with FasL
promotes the physiological deletion of potentially harmful or
unnecessary cells.8 Impaired Fas-induced apoptosis results
in cell accumulation, whereas inappropriate expression or excessive Fas
activity causes tissue damage.18
Primitive hematopoietic progenitor cells express low amounts of
Fas.19-21 However, different cytokines have been shown to
upregulate Fas expression on CD34+ cells, including tumor
necrosis factor- (TNF-) and interferon- (IFN-).19-21 Fas crosslinking enhances TNF-- and
IFN--mediated suppression of colony formation from bone marrow
CD34+ cells.19,20 Moreover, IFN- has been
shown to prime erythroid colony-forming cells for Fas-induced
apoptosis, suggesting Fas-FasL interaction as a possible pathogenetic
mechanism contributing to immune destruction of erythroid
cells.22
In the bone marrow, erythropoiesis occurs in discrete anatomic units,
the erythroblastic islands, consisting of one or two macrophages
surrounded by one or more rings of erythroblasts at different
maturation stages. The inner erythroblastic layers contain immature
cells, whereas the more mature cells are at the periphery of the
island.23 This spatial association of mature and immature erythroblasts may play an important role in erythropoiesis as homocellular cell-cell interaction seems to be required for erythroid cell growth and maturation.24 However, we speculated that
maturating erythroblasts might deliver negative signals to neighboring
cells, as a consequence of a decreased requirement for erythroid cell production. We therefore studied the possible involvement of Fas and
FasL in the regulation of erythropoiesis.
| |
MATERIALS AND METHODS |
In situ apoptosis detection.
Normal human bone marrow specimens were obtained from hematologically
normal patients after their informed consent and the approval by the
Committee for Human Studies. Bone marrow biopsies were fixed in 4%
paraformaldehyde and paraffin embedded at 50°C. Serial bone marrow
sections (6 mm) were mounted onto polylysine-coated microscope slides
and allowed to equilibrate to room temperature. The sections were
exposed to xylene for 6 minutes for deparaffinization and then
rehydrated using scalar dilution of ethanol (100% to 50%), followed
by Tris-buffer saline (TBS) incubation for 5 minutes before starting
the labeled streptavidin-biotin (Dako LSAB Kit, Dako Corporation, Santa
Barbara, CA) staining technique. Sections stained with anti-CD68 (Dako)
or anti-glycophorin-A (JC159, Dako) were treated with biotinylated
antimouse immunoglobulins prediluted in TBS, following by a 30-minute
incubation at room temperature with peroxidase-conjugated streptavidin.
The binding was revealed by aminoethylcarbazole (AEC)
colorimetric substrate. For in situ TUNEL staining, CD68- or
glycophorin-A-labeled bone marrow sections were permeabilized with
0.1% Triton X-100 and 0.1% sodium citrate for 2 minutes on ice and
washed twice with phosphate-buffered saline (PBS). The labeling of
3'-OH fragmented DNA ends (TdT-mediated dUTP nick end labeling)
was performed by an in situ apoptosis detection kit (In Situ Cell Death
Detection, AP; Boehringer Mannheim, Indianapolis, IN). Detection of
labeled ends was performed with a Fab2 antifluorescein
antibody conjugated with alkaline phosphatase (AP).
5-bromo-4-chloro-3-indolyl-phosphate (BCIP; Dako) was used as
colorimetric substrate. Control tissue sections were prelabeled with
irrelevant isotype-matched monoclonal antibodies (MoAbs) and subjected
to identical treatment for TUNEL staining without terminal
deoxynucleotidyl transferase (TdT).
Bone marrow erythroblast purification.
Bone marrow cells from healthy donors were obtained by needle
aspiration and purified over a Ficoll-Hypaque density gradient (Pharmacia, Piscataway, NJ). A greater than 97% pure erythroid population was then obtained by flow cytometry sorting on the basis of
glycophorin-A expression. Briefly, 106 cells/mL were
incubated with saturating amounts of fluorescein isothiocyanate
(FITC)-conjugated anti-glycophorin-A MoAb (Dako) or an isotype-matched
control antibody for 30 minutes on ice. Cells were washed twice with
cold PBS and run on a fluorescence-activated cell sorter (FACS) VANTAGE
cell sorter (Becton Dickinson, San Jose, CA). Glycophorin-A positive
cells were then sorted on the basis of fluorescence emission at 525 nm.
Adult peripheral blood (PB) human progenitor cell purification and
erythropoietic unilineage cultures.
Adult PB was obtained from male donors after their informed consent
and the approval by the Committee for Human Studies.25 Hematopoietic progenitor cells (HPCs) were purified as
reported26 and modified as described.27
Briefly, (IA) PB samples were separated over a Ficoll-Hypaque density
gradient and (IB) PB mononuclear cells resuspended in Iscove's
modified Dulbecco's medium (IMDM) containing 20% heat-inactivated
fetal calf serum (FCS) (GIBCO, Grand Island, NY) for three cycles of
plastic adherence. Thereafter, (II) cells were separated by
centrifugation on a discontinuous Percoll gradient (Biochrom KG,
Berlin, Germany). (III) Step III purification was potentiated (Step
IIIP) as described.26 For unilineage cultures, Step IIIP
HPCs were seeded at 5 × 104/mL and grown in liquid
suspension cultures supplemented with low doses of interleukin-3 (IL-3;
0.01 U/mL) and granulocyte-macrophage colony-stimulating factor
(GM-CSF; 0.001 ng/mL), and high levels of Epo (3 U/mL).26
HPCs grown under these conditions undergo selective erythroid
differentiatiation. Recombinant human IL-3 (rhIL-3; 2 × 106 U/mg) and rhGM-CSF (2 × 108 U/mg)
were supplied by the Genetics Institute (Cambridge, MA); rhEpo (1.2 × 105 U/mg) was obtained from Amgen (Thousand Oaks, CA).
Fas and FasL staining.
For immunofluorescence staining and flow cytometry analysis, cells were
incubated for 30 minutes on ice with phycoerythrin (PE)-conjugated
anti-Fas MoAb (DX2, IgG1; Pharmigen, San Diego, CA) or control IgG1,
and washed twice with cold PBS. Alternatively, cells were incubated for
30 minutes at 4°C with 5 µg/mL of purified rabbit polyclonal
anti-FasL (Ab-1; Calbiochem-Novachem Corp, La Jolla, CA) or control
rabbit IgG, washed, and treated with PE-conjugated donkey anti-rabbit
IgG (Chemicon, Temecula, CA). After an additional washing, cells were
analyzed on a FACSCAN cytofluorimeter (Becton Dickinson).
Cytospins of sorted bone marrow erythroid cells were allowed to
equilibrate to room temperature and fixed in 4% paraformaldheyde for
15 minutes, followed by air-drying. Bound rabbit polyclonal anti-FasL
Ab (Ab-1) or control rabbit IgG were detected by immunoenzymatic alkaline phosphatase antialkaline phosphatase (APAAP) complex procedure (Dako).
Reverse-transcription polymerase chain reaction (RT-PCR) analysis.
Total RNA from erythroblasts at different maturation stages was
extracted by the standard guanidinium thyocianate-CsCl technique and
quantitated by dot hybridization with a human rRNA probe. After
densitometric analysis, the same amount of RNA was reverse-transcribed with oligo (dT) as a primer, and the products were normalized by
amplification of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
gene together with HuT78 cDNA.
cDNA amplification was obtained by 35 PCR cycles, which generated a
346-bp fragment of human FasL (forward primer, from 641to 661 bp;
reverse primer, from 966 to 986 bp).15 PCR products were
verified by sequencing and analyzed by Southern blotting with an
internal oligomer as a probe. The probe used for GAPDH gene was from
880 to 914 bp.
Evaluation of caspase activity and apoptosis in mature and immature
erythroblasts.
Day-7 and day-14 erythroblasts were incubated with 200 ng/mL of
agonistic anti-Fas MoAb (CH-11, IgM; UBI, Lake Placid, NY) or control
IgM. The percentage of erythroblasts undergoing apoptosis was measured
by DNA staining and flow cytometry analysis, as previously described.12 Briefly, the cell pellet was gently
resuspended in hypotonic fluorochrome solution (propidium iodide 50 µg/mL [Sigma, St Louis, MO] in 0.1% sodium citrate plus 0.1%
Triton X-100) and kept overnight at 4°C in the dark until flow
cytometry analysis. The percentage of apoptotic cells was determined by evaluating the number of hypodiploid nuclei.
Evaluation of caspase activation in erythroblasts at different
maturation stages was performed by the ApoAlert assay kit (Clontech, Palo Alto, CA), according to the manufacturer's instructions. Lysates
from 106 cells were incubated with the fluorogenic
substrate (DEVD-AFC) for 60 minutes at 37°C in a buffer containing
5 mmol/L dithiotreitol (DTT). Samples were then analyzed on a plate
fluorimeter (Flow Laboratories, McLean, VA) at 538 nm.
Cytotoxicity studies.
Fas-sensitive and Fas-resistant Epstein-Barr virus (EBV)-transformed
lymphoblastoid target cells were exposed overnight to 1 mmol/L
3,3'-dioctadecyloxacarbocyanine (DioC18), washed
twice with RPMI containing 5% FCS, transferred to round bottom tubes containing different numbers of day-7 or day-14 erythroblasts, and
centrifuged at 1,000 rpm for 10 minutes. Cells were analyzed after 8 hours of culture.
Day-7 erythroblasts, loaded with DioC18 as described above,
were used as target cells and incubated for 36 hours with day-14 effector cells in the presence of either 30 mU/mL or 3 U/mL recombinant Epo. In some cases, 10 µg/mL of an anti-Fas antagonist MoAb ZB4 (UBI)
was added to the target cells 15 minutes before the assay. At the end
of the incubation, cells were treated with 5 µg/mL propidium iodide
and immediately analyzed by flow cytometry. The percentage of specific
lysis was determined by comparing the number of
DioC18-labeled propidium iodide-positive (dead) and
-negative (living) cells among the different samples.15
| |
RESULTS |
Immature erythroblasts are the major apoptotic population in normal
bone marrow.
To determine whether erythroblast apoptosis is a process occurring in
vivo under physiological conditions, bone marrow specimens from healthy
donors were analyzed for in situ apoptosis. Immunohistochemistry of
formalin-fixed sections double labeled for glycophorin staining and
TUNEL reaction revealed the presence of several apoptotic erythroblasts
(about 2% to 3% of the immature erythroid population), showing
phenotypical characteristics of immature cells, such as large volume,
thin cytoplasm, and the cell nucleus occupying at least three fourths
of the whole cell area
(Fig 1A and
B). A minority of cells from other lineages seem to undergo apoptosis
in normal bone marrow, as glycophorin-negative/TUNEL-positive cells
were only occasionally observed (not shown). Moreover, analysis of sections double stained for the macrophage marker CD68 and TUNEL showed
bone marrow macrophages surrounding (Fig 1C) and phagocytosing (Fig 1D)
apoptotic cells, suggesting that macrophages in erythroblastic islands
are responsible for the clearance of apoptotic erythroblasts.
View larger version (83K):
[in this window]
[in a new window]
| Fig 1.
Erythroblast apoptosis in normal bone marrow. Sections
from bone marrow biopsies were fixed in paraformaldehyde and paraffin
and double-labeled for TUNEL reaction with BCIP (black) and
anti-glycophorin-A or anti-CD68 with AEC (red). (A) Control section
treated with irrelevant IgG Abs and TUNEL reaction without TdT. (B)
Section stained with anti-glycophorin-A and TUNEL reaction showing an
immature apoptotic erythroblast (arrowhead). (C and D) Sections treated
with anti-CD68 and TUNEL reaction representing macrophages surrounding
and phagocytosing apoptotic cells are indicated by arrows.
Representative sections from one donor out of four are shown.
|
|
View larger version (62K):
[in this window]
[in a new window]
| Fig 2.
Fas and FasL expression in bone marrow erythroblasts.
Bone marrow erythroid cells obtained by needle aspiration were purified
by Ficoll and flow cytometry sorting based on glycophorin-A positivity.
Erythroblasts were subsequently analyzed by flow cytometry for Fas and
FasL expression (A), and by immunohistochemistry on cytospins stained
with control (B) or anti-FasL polyclonal Abs (C) and revealed with
alkaline phosphatase. A representative experiment out of five performed
with cells from three different donors is shown.
|
|
Erythroblasts express Fas and FasL.
The expression of Fas and FasL was analyzed on freshly isolated bone
marrow erythroid cells sorted for glycophorin-A expression. Figure 2A
shows that most glycophorin-positive erythroblasts (>90%) constitutively express Fas, presumably because they have a high proliferative rate, which is associated with Fas upregulation in
hematopoietic cells.8 In contrast, the expression of FasL in these cells is heterogeneous, FasL being present on about 60% to
70% of bone marrow erythroblasts. To determine whether the differential expression of FasL is related to different maturation stages, we analyzed the morphology of purified bone marrow erythroid cells stained with control or anti-FasL Abs. As shown in Fig 2B and C,
FasL was expressed only on small mature erythroblasts, suggesting that
FasL expression is acquired during the late phases of erythroid
differentiation (ie, at the stage of late polychromatophilic and
orthochromatic erythroblasts).
Expression of Fas and FasL during unilineage erythroid
differentiation.
The unilineage erythroid culture system allows the study of discrete
steps of cell maturation, from undifferentiated CD34+ cells
to the terminal stages of erythroid differentiation.28 Purified CD34+ progenitor cells, grown in the presence of
very low doses of IL-3 and GM-CSF and high amounts of Epo,
differentiate to basophilic erythroblasts after 7 days and
orthochromatic erythroblasts after 14 days of culture. The comparative
analysis of early (day-7) and late (day-14) erythroblasts showed that
Fas is expressed in immature cells and further upregulated in mature
erythroblasts, whereas FasL is absent or barely detectable in immature
erythroblasts and highly expressed in late erythroblasts
(Fig 3A). Membrane-bound FasL is rapidly
cleaved to a soluble form by metalloproteases. We therefore
investigated FasL mRNA expression by semiquantitative RT-PCR to
facilitate accurate quantification of FasL production.29 As
shown in Fig 3B, FasL mRNA is absent in immature erythroblasts but
gradually increases in more mature erythroblasts starting from day 12. At day 14, FasL mRNA levels are comparable or higher than those found
in the positive control HuT78 T lymphoma cell line, known to produce
considerable amounts of FasL.29
View larger version (20K):
[in this window]
[in a new window]
| Fig 3.
Expression of Fas and FasL in unilineage erythroid
differentiation. Purified peripheral blood CD34+ cells
were cultivated with high concentration of Epo and very low amounts of
IL-3 and GM-CSF for up to 14 days. (A) After 7 and 14 days cells were
stained with control, anti-Fas (Fas), and anti-FasL (FasL) Abs, and
analyzed by flow cytometry. (B) Semiquantitative RT-PCR analysis from
erythroblasts at different days of culture and from HuT78 cells. Top
lane, human FasL cDNA amplification; bottom lane, GAPDH cDNA
amplification used to normalize RT-RNAs. A representative experiment
out of three performed with cells from different donors is shown.
|
|
Immature erythroid cells undergo Fas-induced apoptosis in the absence
of high levels of Epo.
Fas expression does not always correlate with its ability to transduce
an apoptotic signal. We therefore analyzed Fas sensitivity of early and
late erythroblasts and the possible interference of Epo in the death
signal generated by Fas crosslinking.
Figure 4A and B show that Fas triggering
induces massive apoptosis of immature erythroblasts in the absence of
Epo, which is extremely effective in protection from Fas-induced
apoptosis. In contrast, Fas crosslinking in mature erythroblasts is not
able to transduce a death signal, even in the absence of Epo (Fig 4A),
suggesting that Fas in mature erythroblasts is not coupled to the
apoptotic machinery. Accordingly, Fas crosslinking in immature
erythroblasts resulted in a strong and persistent caspase activation,
as evaluated by the ability of cell extracts to cleave the fluorogenic
substrate DEVD, whereas no increase in caspase activity was detected in Fas-stimulated mature erythroblasts (Fig 4C), even in the presence of
high Fas expression.
View larger version (13K):
[in this window]
[in a new window]
View larger version (13K):
[in this window]
[in a new window]
| Fig 4.
Fas is functional in immature erythroblasts in the
absence of high levels of Epo. (A) Peripheral CD34-derived day-7 and
day-14 erythroblasts were incubated for 24 hours with or without 200 ng/mL of agonistic anti-Fas MoAb in the absence ( Epo) or in the
presence (+Epo) of 3 U/mL recombinant Epo. Apoptosis was quantitated
by DNA staining and flow cytometry analysis. (B) Day-7 cells were
treated as described above with different concentrations of Epo.
Percentage of protection was calculated by comparison with cells
stimulated in the absence of Epo. A representative experiment out of
five performed with cells from different donors is shown. (C) Lysates
from day-7 and day-14 cells untreated (control) or stimulated for
different times with agonistic anti-Fas MoAb (anti-Fas) were analyzed
for their ability to cleave the fluorogenic caspase substrate DEVD-AFC.
Data are expressed in arbitrary fluorescence units and show a
representative experiment out of four performed with cells from
different donors.
|
|
FasL is functional in mature erythroblasts and able to kill immature
erythroblasts in the absence of high levels of Epo.
To determine whether FasL present on the membrane of mature
erythroblasts is capable of eliciting a cytotoxic response, we exposed
Fas-sensitive and Fas-resistant EBV-transformed lymphoblasts to
increasing numbers of immature (day-7) or mature (day-14)
erythroblasts. As shown in Fig 5A,
FasL-positive mature erythroblasts were able to massively kill
Fas-sensitive, but not Fas-resistant, lymphoblast targets in a
Fas-dependent fashion, as the target lysis was completely prevented by
the addition of anti-Fas antagonist MoAb. As expected, FasL-negative
immature erythroblasts were unable to kill either lymphoblast target
(Fig 5A). To investigate whether Fas-FasL interaction among
erythroblasts results in apoptotic cell death of immature erythroblasts, we evaluated the ability of FasL-expressing mature erythroblasts to kill immature Fas-sensitive erythroblasts. Figure 5B
shows that in the presence of Epo levels comparable to those routinely
found in normal sera, mature erythroblasts are able to efficiently kill
immature erythroblasts through the induction of Fas-mediated apoptosis,
as pretreatment of immature erythroblasts with anti-Fas antagonist MoAb
essentially abolished the cell cytotoxicity. In contrast, no
cytotoxicity against immature erythroblast targets was observed in the
presence of high levels of Epo, indicating that elevated Epo
concentrations are required for protection of immature erythroblasts
against the abundant FasL production of mature erythroblasts.
View larger version (18K):
[in this window]
[in a new window]
| Fig 5.
FasL is functional in mature erythroblasts and able to
kill immature erythroblasts in the absence of high levels of Epo. (A)
Cytotoxic activity of day-7 and day-14 erythroblasts toward
Fas-sensitive (sens) and Fas-resistant (res) EBV-transformed
lymphoblastoid cell lines. Effector and target cells were spun down
together and incubated for 8 hours. In some experiments anti-Fas
antagonist MoAb ZB4 (10 µg/mL) was added to Fas-sensitive cells (sens + ZB4). Data show a representative experiment out of three performed
with cells from different donors. (B) Cytotoxic activity of day 14 erythroblasts toward day-7 erythroblasts pretreated or not with 10 µg/mL ZB4, in the presence of low (30 mU/mL) or high (3 U/mL) amounts
of Epo. Effector and target cells were spun down together and incubated
for 36 hours. Data show mean ± SD of three experiments performed with
cells from different donors.
|
|
| |
DISCUSSION |
The erythroblastic island is a relatively autonomous
unit.23 It is therefore of interest to identify potential
regulators of erythroid cell homeostasis among the cell population
forming the island.
Several studies have shown that the interaction of Fas with FasL plays
a major role in the maintenance of hematopoietic cell homeostasis,
because physiological deletion of T and B lymphocytes, granulocytes,
and natural killer cells seems primarily due to the engagement of Fas
following homocellular or heterocellular FasL
production.8,14,30 Due to the adjacent location of mature and immature erythroblasts in the bone marrow, the possible interaction between these cells may be critical for their fate. Here we have examined the possible apoptotic role of Fas and FasL in the regulation of erythropoiesis.
In situ TUNEL analysis of normal bone marrow specimens has shown here
that several immature erythroblasts are apoptotic. Although an accurate
quantification of this phenomenon is not feasible, due to the unknown
clearance rate of these apoptotic cells in vivo, it is likely that
apoptosis of immature erythroblasts significantly contributes to the
ineffective quote of erythropoietic process described in normal
subjects.31,32
The level of Epo dictates the fate of immature erythroblasts, which
display a high proliferative potential and therefore represent a key
target for the regulation of erythropoiesis in physiological and
pathological conditions.4 We found that immature
erythroblasts, mostly at the basophilic stage, are Epo-dependent and
more susceptible to apoptosis upon Epo deprivation. These cells express
a functional Fas molecule, and in the presence of FasL-producing mature
erythroblasts undergo apoptosis, unless exposed to high levels of Epo.
In contrast, because mature erythroblasts are completely resistant to
Fas-induced apoptosis, they are not susceptible to the autotoxic lysis
mediated by high FasL production. Interestingly, the Epo levels
necessary for protection from Fas-induced apoptosis in immature
erythroblasts are comparable to those found in sera of subjects with
low hemoglobin concentrations or decreased red blood cell
precursor mass.33 We hence postulate that the inhibitory
effect of mature erythroblasts on erythropoiesis may act as a negative
regulatory feedback by inducing cell death of immature erythroblasts
when there is a lower metabolic requirement for new erythrocytes, and
consequently low levels of Epo are present in the bone marrow. On the
other hand, this inhibitory effect is gradually blocked at increasing Epo concentrations coupled with enhanced erythrocyte production. Thus,
the Fas/FasL system may contribute, together with low Epo levels, to
the negative regulation of physiological erythropoiesis.
Several other regulatory systems, including the interaction of other
death receptors with their ligands, may be also involved in the
physiological inhibition of erythropoiesis. This would result in
redundancy and may explain why mice with targeted mutation of the Fas
gene do not show major abnormalities in the erythroid compartment.34
The presence of high levels of functional FasL in mature erythroblasts
may play an important pathogenetic role in a number of diseases
resulting in dyserythropoiesis and anemia. Cytokines or inflammatory
factors able to increase Fas-sensitivity in immature erythroblasts are
likely to alter the balance between Epo and Fas/FasL, with deleterious
effects on erythropoiesis. This may account for the potent erythroid
suppression induced by IFN-, which has been shown to upregulate both
Fas and its apoptotic machinery.35 This suppressor
mechanism might be operating in patients suffering from aplastic
anemia, who often present overproduction of IFN- in the bone
marrow.36,37 Similarly, mice with targeted mutations of the
Fanconi anemia group C gene, a murine model for Fanconi anemia, show
hypersensitivity to IFN-, which, at doses ineffective in normal
mice, primes progenitor cells for Fas-mediated destruction and impaired
clonal growth of erythroid and granulocyte-macrophage lineages.38
Alternatively, it is possible that FasL-producing erythroblasts may
increase their Fas-sensitivity following exposure to priming agents
such as IFN-, resulting in erythroblast suicide as recently proposed.22 However, here we identify
prebasophilic/basophilic erythroblasts as the most sensitive maturation
stage for Fas-induced apoptosis during erythroid differentiation. These
cells do not express FasL and are more sensitive to the inhibitory
effect of IFN- than mature erythroblasts, which gradually lose the
susceptibility to apoptosis while increasing FasL expression. Thus,
immature erythroblasts seem to be a major target for both physiological and pathological inhibition of erythropoiesis.
In conclusion, we provide evidence for an apoptotic role of Fas and
FasL in the regulation of erythropoiesis. Massive FasL production
following mature erythroblast accumulation may act as a negative
regulator of erythroblast development and is likely to contribute to
homeostasis of the erythroblastic island. In this context, basophilic
erythroblasts are the most sensitive target of FasL-induced
antierythropoietic effects and therefore represent a preferential
target for potential Fas/FasL-based anemia.
| |
FOOTNOTES |
Submitted July 31, 1998; accepted September 25, 1998.
The publication costs of this
article were defrayed in part by
page charge payment. This article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. section
1734 solely to indicate this fact.
Address reprint requests to C. Peschle, MD, Kimmel Cancer Center, Room
#902, Thomas Jefferson University, Philadelphia, PA 19107-5541; e-mail:
cesare.peschle{at}mail.tju.edu.
| |
REFERENCES |
1.
Gregory CJ, Eaves AC:
Three stages of erythropoietic progenitor cell differentiation distinguished by a number of physical and biologic properties.
Blood
51:527, 1978[Abstract/Free Full Text]
2.
Krantz SB:
Erythropoietin.
Blood
77:419, 1991[Free Full Text]
3.
Koury MJ, Bondurant MC:
Erythropoietin retards DNA breakdown and prevents programmed cell death in erythroid progenitor cells.
Science
248:378, 1990[Abstract/Free Full Text]
4.
Kelley LL, Koury MJ, Bondurant MC, Koury ST, Sawyer ST, Wickrema A:
Survival or death of individual proerythroblasts results from differing erythropoietin sensitivities: A mechanism for controlled rates of erythrocyte production.
Blood
82:2340, 1993[Abstract/Free Full Text]
5.
Gregoli PA, Bondurant MC:
The roles of Bcl-XL and apopain in the control of erythropoiesis by erythropoietin.
Blood
90:630, 1997[Abstract/Free Full Text]
6.
Reed JC:
Double identity for proteins of the Bcl-2 family.
Nature
387:773, 1997[Medline]
[Order article via Infotrieve]
7.
Nagata S:
Apoptosis by death factor.
Cell
88:355, 1997[Medline]
[Order article via Infotrieve]
8.
Nagata S, Golstein P:
The Fas death factor.
Science
267:1449, 1995[Abstract/Free Full Text]
9.
Alnemri ES, Livingston DJ, Nicholson DW, Salvesen G, Thornberry NA, Wong WW, Yuan J:
Human ICE/CED-3 protease nomenclature.
Cell
87:171, 1996[Medline]
[Order article via Infotrieve]
10.
De Maria R, Lenti L, Malisan F, d' Agostino F, Zeuner A, Rippo MR, Tomassini B, Testi R:
Requirement for GD3 ganglioside in CD95- and ceramide-induced apoptosis.
Science
277:1652, 1997[Abstract/Free Full Text]
11.
Krammer PH:
The CD95(APO-1/Fas) receptor/ligand system: Death signals and disease.
Cell Death Differ
3:159, 1996
12.
De Maria R, Boirivant M, Cifone MG, Roncaioli P, Hahne M, Tschopp J, Pallone F, Santoni A, Testi R:
Functional expression of Fas and Fas Ligand on human gut lamina propria lymphocytes. A potential role for the acidic sphingomyelinase pathway in normal immunoregulation.
J Clin Invest
97:316, 1996[Medline]
[Order article via Infotrieve]
13.
Kiener PA, Davis PM, Rankin BM, Klebanoff SJ, Ledbetter JA, Starling GC, Liles WC:
Human monocytic cells contain high levels of intracellular Fas ligand. Rapid release following cellular activation.
J Immunol
159:1594, 1997[Abstract]
14.
Liles WC, Kiener PA, Ledbetter JA, Aruffo A, Klebanoff SJ:
Differential expression of Fas (CD95) and Fas ligand on normal human phagocytes: Implications for the regulation of apoptosis in neutrophils.
J Exp Med
184:429, 1996[Abstract/Free Full Text]
15.
Giordano C, Stassi G, De Maria R, Todaro M, Richiusa P, Papoff G, Ruberti G, Bagnasco M, Testi R, Galluzzo A:
Potential involvement of Fas and its ligand in the pathogenesis of Hashimoto's Thyroiditis.
Science
275:960, 1997[Abstract/Free Full Text]
16.
Griffith TS, Yu X, Herndon JM, Green D, Ferguson TA:
CD95-induced apoptosis of lymphocytes in an immune-privileged site induces immunological tolerance.
Immunity
5:7, 1996[Medline]
[Order article via Infotrieve]
17.
French LE, Tschopp J:
Thyroiditis and hepatitis: Fas on the road to disease.
Nat Med
3:387, 1997[Medline]
[Order article via Infotrieve]
18.
De Maria R, Testi R:
Fas/FasL interactions: A common pathogenetic mechanism in organ-specific autoimmunity.
Immunol Today
19:121, 1998[Medline]
[Order article via Infotrieve]
19.
Maciejewski JP, Selleri C, Anderson S, Young NS:
Fas antigen expression on CD34+ human marrow cells is induced by interferon gamma and tumor necrosis factor alpha and potentiates cytokine-mediated hematopoietic suppression in vitro.
Blood
85:3183, 1995[Abstract/Free Full Text]
20.
Nagafuji K, Shibuya T, Harada M, Mizuno S, Takenada K, Miyamoto T, Okamura T, Gondo H, Niho Y:
Functional expression of Fas antigen (CD95) on hematopoietic progenitor cells.
Blood
86:883, 1995[Abstract/Free Full Text]
21.
Barcena A, Park SW, Banapour B, Muench MO, Mechetner E:
Expression of Fas/CD95 and Bcl-2 by primitive hematopoietic progenitors freshly isolated from human fetal liver.
Blood
88:2013, 1996[Abstract/Free Full Text]
22.
Dai CH, Price JO, Brunner T, Krantz SB:
Fas ligand is present in human erythroid colony-forming cells and interacts with Fas induced by interferon to produce erythroid cell apoptosis.
Blood
91:1235, 1998[Abstract/Free Full Text]
23.
Bernard J:
The erythroblastic island: Past and future.
Blood Cells
17:5, 1991[Medline]
[Order article via Infotrieve]
24.
Hanspal M:
Importance of cell-cell interactions in regulation of erythropoiesis.
Curr Opin Hematol
4:142, 1997[Medline]
[Order article via Infotrieve]
25.
Gabbianelli M, Sargiacomo M, Pelosi E, Testa U, Isacchi G, Peschle C:
"Pure" human progenitors: Permissive action of basic fibroblast growth factor.
Science
249:1561, 1990[Abstract/Free Full Text]
26.
Labbaye C, Valtieri M, Testa U, Giampaolo A, Meccia E, Sterpetti P, Parolini I, Pelosi E, Bulgarini D, Cayre YE, Peschle C:
Retinoic acid downmodulates erythroid differentiation and GATA-1 expression in purified adult progenitor culture.
Blood
83:651, 1994[Abstract/Free Full Text]
27.
Testa U, Fossati C, Samoggia P, Masciulli R, Mariani G, Hassan HJ, Sposi NM, Guerriero R, Rosato V, Gabbianelli M, Pelosi E, Valtieri M, Peschle C:
Expression of growth factor receptors in unilineage differentiation culture of purified hematopoietic progenitors.
Blood
88:3391, 1996[Abstract/Free Full Text]
28.
Condorelli G, Vitelli L, Valtieri M, Marta I, Montesoro E, Lulli V, Baer R, Peschle C:
Coordinate expression and developmental role of Id2 protein and TAL1/E2A heterodimer in erythroid progenitor differentiation.
Blood
86:164, 1995[Abstract/Free Full Text]
29.
Mariani SM, Matiba B, Baumler C, Krammer PH:
Regulation of cell surface APO-1/Fas (CD95) ligand expression by metalloproteases.
Eur J Immunol
25:2303, 1995[Medline]
[Order article via Infotrieve]
30.
Adachi M, Suematsu S, Kondo T, Ogasawara J, Tanaka T, Yoshida N, Nagata S:
Targeted mutation in the Fas gene causes hyperplasia in peripheral lymphoid organs and liver.
Nat Genet
11:294, 1995[Medline]
[Order article via Infotrieve]
31.
Ricketts C, Jacobs A, Cavill I:
Ferrokinetics and erythropoiesis in man. The measurement of effective and ineffective erythropoiesis and red lifespan using 59Fe.
Br J Haematol
31:65, 1975[Medline]
[Order article via Infotrieve]
32.
Samson D, Tikerpae J, Crowne H:
A simple in vitro method for the assessment of ineffective erythropoiesis.
Blood
58:782, 1981[Abstract/Free Full Text]
33.
Cazzola M, Guarnone R, Cerani P, Centenara E, Rovati A, Beguin Y:
Red blood cell precursor mass as an independent determinant of serum erythropoietin level.
Blood
91:2139, 1998[Abstract/Free Full Text]
34.
Adachi M, Suematsu S, Kondo T, Ogasawara J, Tanaka T, Yoshida N, Nagata S:
Targeted mutation in the Fas gene causes hyperplasia in peripheral lymphoid organs and liver.
Nat Med
11:294, 1995
35.
Ossina NK, Cannas A, Powers VC, Fitzpatrick PA, Knight JD, Gilbert JR, Shekhtman EM, Tomei LD, Umansky SR, Kiefer MC:
Interferon- modulates a p53-independent apoptotic pathway and apoptosis-related gene expression.
J Biol Chem
272:16351, 1997[Abstract/Free Full Text]
36.
Maciejewski JP, Selleri C, Sato T, Anderson S, Young NS:
Increased expression of Fas antigen on bone marrow CD34+ cells of patients with aplastic anaemia.
J Haematol
91:245, 1995
37.
Young NS, Maciejewski J:
The pathophysiology of acquired aplastic anemia.
N Engl J Med
336:1365, 1997[Free Full Text]
38.
Rathbun RK, Faulkner GR, Ostroski MH, Christianson TA, Hughes G, Jones G, Cahn R, Maziarz R, Royle G, Keeble W, Heinrich MC, Grompe M, Tower PA, Bagby GC:
Inactivation of the Fanconi anemia group C gene augments interferon--induced apoptotic responses in hematopoietic cells.
Blood
90:974, 1997[Abstract/Free Full Text]
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
M. J. Weiss and C. O. dos Santos
Chaperoning erythropoiesis
Blood,
March 5, 2009;
113(10):
2136 - 2144.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Zeuner, F. Pedini, F. Francescangeli, M. Signore, G. Girelli, A. Tafuri, and R. De Maria
Activity of the BH3 mimetic ABT-737 on polycythemia vera erythroid precursor cells
Blood,
February 12, 2009;
113(7):
1522 - 1525.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T.P. Zwaka
Ronin and Caspases in Embryonic Stem Cells: A New Perspective on Regulation of the Pluripotent State
Cold Spring Harb Symp Quant Biol,
January 1, 2008;
73(0):
163 - 169.
[Abstract]
[PDF]
|
|
|
|
|
|
|
J. Palis
ICAM-4 lands on the erythroblast island
Blood,
September 15, 2006;
108(6):
1793 - 1794.
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Lee, A. Lo, S. A. Short, T. J. Mankelow, F. Spring, S. F. Parsons, K. Yazdanbakhsh, N. Mohandas, D. J. Anstee, and J. A. Chasis
Targeted gene deletion demonstrates that the cell adhesion molecule ICAM-4 is critical for erythroblastic island formation
Blood,
September 15, 2006;
108(6):
2064 - 2071.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y.-E. Claessens, M. Fontenay, F. Pene, J.-D. Chiche, M. Guesnu, C. Hababou, N. Casadevall, J.-F. Dhainaut, J.-P. Mira, and A. Cariou
Erythropoiesis Abnormalities Contribute to Early-Onset Anemia in Patients with Septic Shock
Am. J. Respir. Crit. Care Med.,
July 1, 2006;
174(1):
51 - 57.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
H. Walczak
Polycythemia vera erythroblasts: too tough to die
Blood,
May 1, 2006;
107(9):
3422 - 3423.
[Full Text]
[PDF]
|
|
|
|
|
|
|
N. Felli, F. Pedini, A. Zeuner, E. Petrucci, U. Testa, C. Conticello, M. Biffoni, A. Di Cataldo, J. A. Winkles, C. Peschle, et al.
Multiple Members of the TNF Superfamily Contribute to IFN-{gamma}-Mediated Inhibition of Erythropoiesis
J. Immunol.,
August 1, 2005;
175(3):
1464 - 1472.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
P. Mirandola, C. Ponti, G. Gobbi, I. Sponzilli, M. Vaccarezza, L. Cocco, G. Zauli, P. Secchiero, F. A. Manzoli, and M. Vitale
Activated human NK and CD8+ T cells express both TNF-related apoptosis-inducing ligand (TRAIL) and TRAIL receptors but are resistant to TRAIL-mediated cytotoxicity
Blood,
October 15, 2004;
104(8):
2418 - 2424.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L. Gutierrez, F. Lindeboom, A. Langeveld, F. Grosveld, S. Philipsen, and D. Whyatt
Homotypic signalling regulates Gata1 activity in the erythroblastic island
Development,
July 1, 2004;
131(13):
3183 - 3193.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
U. Schmidt, E. van den Akker, M. Parren-van Amelsvoort, G. Litos, M. de Bruijn, L. Gutierrez, R. W. Hendriks, W. Ellmeier, B. Lowenberg, H. Beug, et al.
Btk Is Required for an Efficient Response to Erythropoietin and for SCF-controlled Protection against TRAIL in Erythroid Progenitors
J. Exp. Med.,
March 8, 2004;
(2004)
jem.20031109.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
W. Aerbajinai, Y. T. Lee, U. Wojda, V. A. Barr, and J. L. Miller
Cloning and Characterization of a Gene Expressed during Terminal Differentiation That Encodes a Novel Inhibitor of Growth
J. Biol. Chem.,
January 16, 2004;
279(3):
1916 - 1921.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Tsantes, S. Tassiopoulos, S. I. Papadhimitriou, S. Bonovas, L. Kavalierou, G. Vaiopoulos, and I. Meletis
Suboptimal Erythropoietic Response to Hypoxemia in Idiopathic Pulmonary Fibrosis
Chest,
August 1, 2003;
124(2):
548 - 553.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Q. Nhan, W. C. Liles, A. Chait, J. T. Fallon, and S. M. Schwartz
The p17 Cleaved Form of Caspase-3 Is Present Within Viable Macrophages In Vitro and in Atherosclerotic Plaque
Arterioscler. Thromb. Vasc. Biol.,
July 1, 2003;
23(7):
1276 - 1282.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Lee, F. A. Spring, S. F. Parsons, T. J. Mankelow, L. L. Peters, M. J. Koury, N. Mohandas, D. J. Anstee, and J. A. Chasis
Novel secreted isoform of adhesion molecule ICAM-4: potential regulator of membrane-associated ICAM-4 interactions
Blood,
March 1, 2003;
101(5):
1790 - 1797.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
V. Hietakangas, M. Poukkula, K. M. Heiskanen, J. T. Karvinen, L. Sistonen, and J. E. Eriksson
Erythroid Differentiation Sensitizes K562 Leukemia Cells to TRAIL-Induced Apoptosis by Downregulation of c-FLIP
Mol. Cell. Biol.,
February 15, 2003;
23(4):
1278 - 1291.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
V. Katavic, I. K. Lukic, N. Kovacic, D. Grcevic, J. A. Lorenzo, and A. Marusic
Increased Bone Mass Is a Part of the Generalized Lymphoproliferative Disorder Phenotype in the Mouse
J. Immunol.,
February 1, 2003;
170(3):
1540 - 1547.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y.-H. Ling, L. Liebes, B. Ng, M. Buckley, P. J. Elliott, J. Adams, J.-D. Jiang, F. M. Muggia, and R. Perez-Soler
PS-341, a Novel Proteasome Inhibitor, Induces Bcl-2 Phosphorylation and Cleavage in Association with G2-M Phase Arrest and Apoptosis
Mol. Cancer Ther.,
August 1, 2002;
1(10):
841 - 849.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
H. A. Papadaki, H. D. Kritikos, V. Valatas, D. T. Boumpas, and G. D. Eliopoulos
Anemia of chronic disease in rheumatoid arthritis is associated with increased apoptosis of bone marrow erythroid cells: improvement following anti-tumor necrosis factor-alpha antibody therapy
Blood,
June 28, 2002;
100(2):
474 - 482.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y.-E. Claessens, D. Bouscary, J.-M. Dupont, F. Picard, J. Melle, S. Gisselbrecht, C. Lacombe, F. Dreyfus, P. Mayeux, and M. Fontenay-Roupie
In vitro proliferation and differentiation of erythroid progenitors from patients with myelodysplastic syndromes: evidence for Fas-dependent apoptosis
Blood,
March 1, 2002;
99(5):
1594 - 1601.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
F. Silvestris, P. Cafforio, M. Tucci, and F. Dammacco
Negative regulation of erythroblast maturation by Fas-L+/TRAIL+ highly malignant plasma cells: a major pathogenetic mechanism of anemia in multiple myeloma
Blood,
February 15, 2002;
99(4):
1305 - 1313.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
B. T. Suratt, S. K. Young, J. Lieber, J. A. Nick, P. M. Henson, and G. S. Worthen
Neutrophil maturation and activation determine anatomic site of clearance from circulation
Am J Physiol Lung Cell Mol Physiol,
October 1, 2001;
281(4):
L913 - L921.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. C. P. Somervaille, D. C. Linch, and A. Khwaja
Growth factor withdrawal from primary human erythroid progenitors induces apoptosis through a pathway involving glycogen synthase kinase-3 and Bax
Blood,
September 1, 2001;
98(5):
1374 - 1381.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Matsushima, M. Nakashima, K. Oshima, Y. Abe, J. Nishimura, H. Nawata, T. Watanabe, and K. Muta
Receptor binding cancer antigen expressed on SiSo cells, a novel regulator of apoptosis of erythroid progenitor cells
Blood,
July 15, 2001;
98(2):
313 - 321.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Moreau, M. Leite-de-Moraes, S. Ezine, J. P. Di Santo, M. Dy, and E. Schneider
Natural killer cell-dependent apoptosis of peripheral murine hematopoietic progenitor cells in response to Fas cross-linking: involvement of tumor necrosis factor-{alpha}
Blood,
May 15, 2001;
97(10):
3069 - 3074.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
N. Droin, F. Bichat, C. Rebe, A. Wotawa, O. Sordet, A. Hammann, R. Bertrand, and E. Solary
Involvement of caspase-2 long isoform in Fas-mediated cell death of human leukemic cells
Blood,
March 15, 2001;
97(6):
1835 - 1844.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
F. Silvestris, M. Tucci, P. Cafforio, and F. Dammacco
Fas-L up-regulation by highly malignant myeloma plasma cells: role in the pathogenesis of anemia and disease progression
Blood,
March 1, 2001;
97(5):
1155 - 1164.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. D'Alessio, A. Riccioli, P. Lauretti, F. Padula, B. Muciaccia, P. De Cesaris, A. Filippini, S. Nagata, and E. Ziparo
Testicular FasL is expressed by sperm cells
PNAS,
February 22, 2001;
(2001)
51566098.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
S. C. Kogan, D. E. Brown, D. B. Shultz, B.-T. H. Truong, V. Lallemand-Breitenbach, M.-C. Guillemin, E. Lagasse, I. L. Weissman, and J. M. Bishop
BCL-2 Cooperates with Promyelocytic Leukemia Retinoic Acid Receptor {{alpha}} Chimeric Protein (PMLRAR{{alpha}}) to Block Neutrophil Differentiation and Initiate Acute Leukemia
J. Exp. Med.,
February 20, 2001;
193(4):
531 - 544.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Zermati, C. Garrido, S. Amsellem, S. Fishelson, D. Bouscary, F. Valensi, B. Varet, E. Solary, and O. Hermine
Caspase Activation Is Required for Terminal Erythroid Differentiation
J. Exp. Med.,
January 16, 2001;
193(2):
247 - 254.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Kashii, M. Uchida, K. Kirito, M. Tanaka, K. Nishijima, M. Toshima, T. Ando, K. Koizumi, T. Endoh, K.-i. Sawada, et al.
A member of Forkhead family transcription factor, FKHRL1, is one of the downstream molecules of phosphatidylinositol 3-kinase-Akt activation pathway in erythropoietin signal transduction
Blood,
August 1, 2000;
96(3):
941 - 949.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L. Zamai, P. Secchiero, S. Pierpaoli, A. Bassini, S. Papa, E. S. Alnemri, L. Guidotti, M. Vitale, and G. Zauli
TNF-related apoptosis-inducing ligand (TRAIL) as a negative regulator of normal human erythropoiesis
Blood,
June 15, 2000;
95(12):
3716 - 3724.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
I. Choi, K. Muta, A. Wickrema, S. B. Krantz, J. Nishimura, and H. Nawata
Interferon gamma delays apoptosis of mature erythroid progenitor cells in the absence of erythropoietin
Blood,
June 15, 2000;
95(12):
3742 - 3749.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
N. Sol, J. Le Junter, I. Vassias, J. M. Freyssinier, A. Thomas, A. F. Prigent, B. B. Rudkin, S. Fichelson, and F. Morinet
Possible Interactions between the NS-1 Protein and Tumor Necrosis Factor Alpha Pathways in Erythroid Cell Apoptosis Induced by Human Parvovirus B19
J. Virol.,
October 1, 1999;
73(10):
8762 - 8770.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. D'Alessio, A. Riccioli, P. Lauretti, F. Padula, B. Muciaccia, P. De Cesaris, A. Filippini, S. Nagata, and E. Ziparo
Testicular FasL is expressed by sperm cells
PNAS,
March 13, 2001;
98(6):
3316 - 3321.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
Top
Abstract
Introduction