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Prepublished online as a Blood First Edition Paper on July 18, 2002; DOI 10.1182/blood-2002-01-0222.
CLINICAL OBSERVATIONS, INTERVENTIONS, AND THERAPEUTIC TRIALS
From the Division of Hematology, Nippon Medical School,
Hematonosis Cell Analysis Center, Otsuka Assay Laboratories,
Division of Hematology, Tokyo Metropolitan Geriatric Hospital, Division
of Hematology, Tokyo Metropolitan Police Hospital, Division of
Hematology, Tokyo Metropolitan Komagome Hospital, Division of
Hematology, Tokyo Metropolitan Tama Geriatric Hospital, Division of
Hematology, Showa University, Tokyo, Japan; Division of Hematology,
Kyoto University, and Division of Hematology, Takeda Hospital, Kyoto,
Japan.
Knowledge of the blast phenotype in myelodysplastic
syndrome (MDS) would be valuable, as in other malignancies,
but remains sparse. This is mainly because MDS blasts are a minor
population in clinical samples, making analysis difficult. Thus, for
this blast phenotype study, we prepared blast-rich specimens (using a
new density centrifugation reagent for harvesting blasts) from blood
and marrow samples of 95 patients with various MDS subtypes and 21 patients with acute leukemia transformed from MDS (AL-MDS). Flow
cytometry revealed that a high proportion of the enriched blast cells
(EBCs) from almost all patients showed an
immunophenotype of committed myeloid precursors
(CD34+CD38+HLA-DR+CD13+CD33+),
regardless of the disease subtype. The cytochemical reaction for
myeloperoxidase was negative in 58% of the cases. Thus, the EBC
phenotype is more immature in MDS than in de novo acute myeloid leukemia. MDS EBCs often coexpressed stem cell antigens and late-stage myeloid antigens asynchronously, but rarely expressed T- and B-lymphoid cell-specific antigens. Markers for myeloid cell maturation (CD10 and
CD15) were more prevalent on EBCs from low-risk MDS (refractory anemia
[RA] and RA with ringed sideroblasts), whereas markers for myeloid
cell immaturity (CD7 and CD117) were more prevalent on EBCs from
high-risk MDS (chronic myelomonocytic leukemia, RA with excess blasts
[RAEB], and RAEB in transformation) and AL-MDS. A shift to a more
immature phenotype of EBCs, accompanying disease progression, was also
documented by sequential phenotyping of the same patients. Further, CD7
positivity of EBCs was an independent variable for a poor prognosis in
MDS. These data represent new, valuable information regarding MDS.
(Blood. 2002;100:3887-3896) Myelodysplastic syndrome (MDS) is a malignant
disorder of hematopoietic progenitors in which the bone marrow (BM) is
composed of clonal hematopoietic cells showing various degrees of
differentiation in each case.1-3 The
French-American-British (FAB) cooperative group proposed 5 subgroups of
MDS based mainly on the percentage of blasts in the BM and peripheral
blood (PB), that is, refractory anemia (RA), RA with ringed
sideroblasts (RARS), chronic myelomonocytic leukemia (CMML), RA with
excess blasts (RAEB), and RAEB in transformation (RAEB-t).4 Recently, the World Health Organization (WHO)
proposed a classification for MDS,5 but its biologic and
clinical relevance has been thrown into question by subsequent
data.6,7 MDS usually shows cytopenia, mainly due to early
death of partially or fully differentiated hematopoietic cells and
insufficient differentiation capacity of the progenitors to mature
blood cells. The prognosis of MDS, which differs among FAB subtypes and
is more accurately predicted by the International Prognostic Scoring
System (IPSS), is extremely poor.8 Manifestations caused
by cytopenia and transformation to acute leukemia (AL) due to further
loss of the ability of clonal cells to differentiate are the major
causes of death in MDS.
Immunophenotype data for whole myeloid cells of various maturity,
erythroblasts, and megakaryocytes in MDS have been
reported.9 However, contrary to de novo acute myeloid
leukemia (AML), few phenotypic data have been compiled regarding MDS
blasts. One of the main reasons for this is that MDS blasts are not
predominant cells in the BM and PB, making reliable analysis of blasts
difficult. In our own experience, reliable immunophenotype data for MDS
blasts were obtained for only a fraction of MDS cases by flow cytometry (FCM). Hitherto, the available data on the MDS blast phenotype are for
blasts of acute leukemia transformed from MDS (AL-MDS)10 and blasts before leukemic transformation,11,12 the latter of which were able to be analyzed only by immunocytochemistry and
immunohistochemistry. Regarding the latter case, due to weaknesses of
the applied techniques, the accuracy and objectivity of the data were
not definitive and the number of antibodies used was small. Phenotypic
data for MDS blasts would be useful for the following reasons. First,
the phenotype of MDS blasts would help in the development and
application of therapeutic agents for targeting cell surface antigens,
like the anti-CD33 calicheamicin conjugate and inhibitors of
receptor tyrosine kinase (RTK) for de novo AML.13,14 Second, knowledge of the blast phenotype could help to predict the
outcome of patients. Third, blast phenotype data could be used to
subclassify MDS and distinguish between MDS and de novo AML. To date
the latter has been done arbitrarily on the basis of the percentage of
blasts in the BM and PB, which is not biologically relevant.
One of the present authors developed a method, using metrizamide
density centrifugation, for harvesting blasts of high purity and high
recovery from PB and BM of patients with MDS.15 Based on
this method, a stable density centrifugation reagent for reproducibly harvesting viable blasts was developed.16 This is a novel
reagent not containing Ficoll-Hypaque, Percoll, or albumin. Regarding MDS blasts, which often exist as a minor cell population in samples, there had been no reliable data (such as their pattern on the CD45
versus side scatter [SSC] display of FCM) for gating of
blasts by FCM. Therefore, in this study, we used that new density
centrifugation reagent to obtain blast-rich specimens from patients
with MDS and AL-MDS, which allowed reliable blast gating to determine
the phenotype of enriched blast cells (EBCs) in most of the patients at
diagnosis (n = 116). We also analyzed the EBC phenotype after disease
progression in some patients. This is the first report to present the
detailed phenotypic features of MDS blasts and their clinical significance.
Patients
Cell preparation
FCM and cytochemistry Immunophenotyping was performed by 3-color FCM, in which EBCs and other cell populations were gated by a CD45-gating method.19,20 In brief, the cells were stained with anti-CD45 antibody labeled with peridinin chlorophyll (PerCP; Becton Dickinson, San Jose, CA) and pairs of antibodies conjugated with either fluorescein isothiocyanate (FITC) or phycoerythrin (PE). These antibodies were directed to CD3, CD5, CD8, CD15, CD16, CD19, CD25, CD34, HLA-DR (FITC-conjugated; Becton Dickinson), CD4, CD11b, CD13, CD14, CD34 (PE-conjugated; Becton Dickinson), CD2, CD7, CD38 (FITC-conjugated; Pharmingen, San Diego, CA), CD20, CD33, CD56 (PE-conjugated; Pharmingen), CD10, CD117, and glycophorin A (PE-conjugated; Coulter-Immunotech, Hialeah, FL). Single-labeled cells were used to compensate for fluorescence emission overlap of each fluorochrome into inappropriate channels. Isotype-matched negative controls were used in all assays. At least 10 000 events were acquired for most samples. Expression of each antigen was regarded as positive when at least 20% of gated cells were more fluorescent than the negative control. Analysis was performed on a FACScan (Becton Dickinson).Cytospin preparations were subjected to cytochemical stains
(myeloperoxidase [MPO] and nonspecific esterase [ Statistical analyses Differences between 2 groups of data of continuous variables were analyzed by Student t test. Differences in categorical variables were evaluated using the 2 test. The duration
of overall survival (OS) was calculated from the time of diagnosis
(almost identical to the date of the blast phenotyping) until death.
The duration of transformation-free survival (TFS) was calculated from
the time of diagnosis until the date of transformation to AL. Patients
dying from any cause without developing AL were treated as censored
data regarding the date of death in the TFS analysis. Patients who
underwent stem cell transplantation (SCT) or who were lost to follow-up were also censored regarding the date of SCT or the last follow-up in
both the OS and TFS analyses. Survival curves were obtained by the
Kaplan-Meier method and compared by the log-rank test or, when
applicable, by the test for trend. Multivariate analysis was performed
by Cox proportional hazards regression analysis. P > .05 was considered to be statistically significant.
Validity of the use of BR density centrifugation Figure 1 presents an example of blast enrichment by BR density centrifugation. When PB containing 1.5% blasts (Figure 1A) was obtained from an MDS patient and subjected to BR density centrifugation, nucleated cells were separated into 2 fractions, that is, the BR interface and BR precipitate. Whereas erythrocytes were exclusively in the BR precipitate, blasts were recovered in the BR interface with high purity (Figure 1B) but were negligible in the BR precipitate (Figure 1C). Reagents for mononuclear cell isolation, such as Ficoll-Paque, could not sufficiently enrich blasts from the same PB sample (Figure 1D). When aspirated BM cells from healthy volunteers (n = 5) were subjected to BR density centrifugation and analyzed by FCM, both myeloblasts (CD45lowCD34+CD13+CD33+) and 2 types of B-cell precursors (stage I [CD45lowCD34+CD10+CD19+CD20±] and stage II [CD45lowCD34 CD10+CD19+CD20+]
immature B cells), which were reported to exist in normal BM as very
minor populations,21 were detected on the CD45 versus SSC
display of cells in the BR interface (a representative example is shown
in Figure 1F). These cell populations were not detected on the same
display for cells in the BR precipitate (data not shown). We then
confirmed that the results of immunophenotyping and cytochemistry of
blasts did not differ between unprocessed blasts and blasts obtained by
BR density centrifugation for all the examined samples (n = 64) that
had been obtained from acute lymphocytic leukemia, AML, and RAEB-t
cases (representative immunophenotyping of blasts in unprocessed
samples and blasts separated by BR density centrifugation from the same
samples are shown in Figure 1G-J). The recovery of blasts after BR
density centrifugation (the number of blasts in the BR interface
divided by the number of blasts in the unseparated sample) was
determined for 27 of the above 64 samples and showed a mean value of
69.6% ± 12.5%. The viability of separated cells was at least 98%,
with well-preserved morphology. Based on these findings, we decided to
use BR density centrifugation to enrich MDS blasts for
characterization.
Blast enrichment by BR centrifugation from 143 samples Cell samples (n = 143) from patients with MDS and AL-MDS were subjected to BR density centrifugation, and the blast fraction (the BR interface) was collected for subsequent analyses. Figure 2 shows the correlation between the percentage of blasts in these samples before and after the centrifugation. Blast enrichment was achieved for both the aspirated BM cells and PB and was more efficient in the latter. The smallest percentage of blasts in these 143 samples before centrifugation was 0.25%, which was observed in 3 PB samples. The percentages of blasts after the BR density centrifugation of these 3 samples were 44%, 46%, and 96%.
Flow cytometric gating of blasts enriched by BR centrifugation The BR density centrifugation enriched blasts as well as simplified cell compositions in the harvested cell fractions; thus, reliable gating of blasts by FCM was possible for most samples. Representative examples of this gating are shown in Figure 3A, in which a gate for blasts is marked as R1, and the percentages of blasts determined in Wright-Giemsa-stained cytospin preparations are shown in the legend. Cases 1 and 3 of Figure 3A are examples of the cell fractions in which blasts are predominant. Minor contamination by other cells, most of which were lymphocytes (R2), was able to be easily excluded by gating on the CD45 versus SSC display. Case 2 is an example of a cell fraction in which blasts are a minor population. Because the cell composition of this case is simple (blasts, lymphocytes [R2], and monocytes [R3]), the blasts were easily gated. Each gated cell population in cases 1 to 3 showed a typical cytogram on the forward scatter (FSC) versus SSC display (lower panels of Figure 3A) and a typical antigen profile for each cell population (data not shown). Case 4 of Figure 3A is the most complicated case. The cell fraction of this patient, whose diagnosis was RA, had a relatively diverse cell composition compared with the other cases but consisted of 3 kinds of cell cluster (blasts, lymphocytes [R2], and erythroid cells [R4]) and myeloid cells, other than myeloblasts, in various stages of maturation (cells in the rectangle) on the CD45 versus SSC display. Regarding case 4, part of the flow cytometric immunophenotyping for blasts (cells in R1) is shown in Figure 3B, and the cardinal data of the antigen profiles for 4 gated cell populations are shown in Table 1. The cells in R1 in this case were confirmed to be blasts with a myeloid phenotype on the basis of the following findings. (1) Expression of CD34 is a definitive indicator of blasts, as is the expression of HLA-DR without CD11b on moderately CD45+ cells.21 The cells in R1 in this case met both of these criteria. (2) The cells in R1 showed a typical cytogram of blasts on both FSC versus SSC and CD45 versus SSC displays. (3) The percentage of cells gated by R1 was compatible with the percentage of blasts determined in cytospin preparations.
Similar to these examples, the reliability of flow cytometric gating of
blasts was carefully checked for all 143 samples, and 6 samples were
excluded from the subsequent analyses (3 samples due to insufficient
cell number and 3 samples due to inaccurate gating of the blasts).
Thus, data for 137 samples from 116 cases (both PB and BM samples for
21 cases) were analyzed. Table 2 shows
the characteristics of these 116 cases. Because a larger volume of
aspirated BM cells was needed for harvesting blasts from RA and RARS
cases, the number of these cases was relatively small compared with the
other disease subtypes.
Immunophenotyping and cytochemistry of EBCs from 116 cases The data for EBCs from 116 cases are summarized in Tables 3 and 4. B-cell precursors, which can be detected in normal BM samples after BR density centrifugation, were detected in 2 RA cases and 1 RAEB case among the subjects whose BM cells were analyzed (n = 79). For these 3 cases, the data of gated blasts other than B-cell precursors are presented in Tables 3 and 4. The data for PB and BM samples from the same subjects (n = 21) did not differ. We also show the immunophenotype of de novo AML blasts prepared by BR density centrifugation for comparison (Table 5).
The MDS EBCs of almost all cases had the phenotype of a committed
myeloid precursor
(CD34+CD38+HLA-DR+CD13+CD33+;
Table 3). Cases positive for CD34, CD38, HLA-DR, CD13, and CD33
were 112 of 116 cases (positive cases among total cases examined, 97%), 108 of 111 cases (97%), 116 of 116 cases (100%), 114 of 114 cases (100%), and 114 of 116 cases (98%), respectively. The percentages of EBCs positive for CD34, CD38, HLA-DR, CD13, and CD33
(mean ± SD of data from the positive cases) were
81.6% ± 18.9%, 88.0% ± 14.1%, 90.5% ± 13.0%,
84.3% ± 16.6%, and 76.5% ± 20.5%, respectively. All 116 cases
were positive for CD13 or CD33 or both. Three cases had a
CD34+CD38 CD117, which is expressed on a subset of hematopoietic progenitors and
mast cells in normal hematopoiesis, was expressed in 73 of 114 cases
(64%). MPO was negative in 63 of 108 cases (58%). The high prevalence
of CD34+ cases and MPO Table 4 shows the expression data for lymphoid lineage-associated antigens. Among the T cell-associated antigens, no cases were CD3+ or CD8+, and 3 cases were CD2+ or CD5+. Compared with these antigens, CD4 and CD7 are less restricted to lymphoid cells in normal hematopoiesis; that is, the former is expressed on monocytes, and the latter is expressed on a fraction of CD34+ myeloid progenitors and proposed as a marker of immaturity in myeloid cells (see "Discussion"). EBCs expressed CD4 and CD7 in 54 of 114 cases (47%) and 40 of 116 cases (34%), respectively. Among B cell-associated antigens, no cases were CD19+ or CD20+ or both. Expression of CD10, which is detected on B-cell precursors and mature neutrophils in normal hematopoiesis,25 was observed in 22 of 116 cases (19%). Regarding natural killer (NK) cell-associated antigens, 31 of 116 cases (27%) were CD56+. Expression of CD16, which is observed on NK cells, metamyelocytes, and mature neutrophils in normal hematopoiesis,23 was negative for all examined cases. When the disease subtype was classified as low-risk MDS (RA and RARS),
high-risk MDS (CMML, RAEB, and RAEB-t), or AL-MDS, the proportion of
cases positive for CD7, CD10, CD15, and CD117 differed significantly
among them (Table 6), whereas the other data presented in Tables 3 and 4 did not. Markers for immaturity of
myeloid cells (CD7 and CD117) were more prevalent in high-risk MDS and
AL-MDS, whereas markers for maturation of myeloid cells (CD10 and CD15)
were more prevalent in low-risk MDS. In particular, none of 23 low-risk
cases were CD7+, and almost all low-risk MDS cases (21 of
22 cases) were CD15+. We then investigated whether the
difference in immunophenotype between MDS subtypes occurs during
disease progression of individual cases. For this purpose we assumed
that, among the 4 antigens presented in Table 6, CD7 is a target
marker. This assumption was based on the following reasons. (1) During
several years of follow-up, transformation from low-risk MDS to
high-risk MDS or AL-MDS occurs at only a low frequency, whereas
transformation from high-risk MDS to AL-MDS is more
common.8 (2) Among the 4 antigens, the percentage
of CD7+ cases alone differed between RAEB, RAEB-t, and
AL-MDS (31%, 52%, and 52%, respectively; P = .0466 for
RAEB versus RAEB-t and AL-MDS). Further, the percentage of EBCs
positive for CD7 (mean of data from the positive cases) was highest in
AL-MDS (RAEB 38%, RAEB-t 39%, and AL-MDS 56%). We were able to
examine the immunophenotype after disease progression in 8 of the 116 cases (Table 7). Compared with the
immunophenotype before disease progression in each case, after disease
progression the EBCs had clearly gained CD7 expression in 3 of the 8 cases (cases 6, 116, and 46) and, in addition, 2 of these 3 cases were
accompanied by a decrease in CD15 expression on the EBCs (cases 116 and
46). There were 2 other cases in which CD15 expression on the EBCs
decreased after disease progression (cases 49 and 45). Furthermore, the
EBCs of case 46 gained CD34 expression during disease progression.
Compared with these data, expression of CD10 and CD117 did not show
such clear changes accompanying disease progression. These data
indicate that, in the process of disease progression, the blast
phenotype becomes more immature in at least some MDS cases. The
decrease in CD15 expression during transformation from high-risk MDS to
AL-MDS in individual cases conflicts with the data at the initial
evaluation of the 116 cases, in which similar percentages of cases were
CD15+ in high-risk MDS and AL-MDS. However, this conflict
does not present a problem (see "Discussion").
Prognostic value of EBC phenotype in MDS The IPSS is a well-validated prognostic index for MDS.8 The IPSS is composed of 3 parameters the percentage
of BM blasts, degree of cytopenia, and karyotype. Although the data for
these parameters change with time in MDS, the IPSS determined by the data at initial evaluation is strongly associated with the prognosis. Hence, we examined the prognostic value of the phenotype of EBCs at the
initial evaluation in our MDS cases. At the time of survival analysis,
52 of the 95 MDS patients had died. The median follow-up for patients
alive at the time of analysis was 20 months.
The age, IPSS, and all variables presented in Tables 3 and 4 were
analyzed for the MDS patients. AL-MDS patients were excluded from the
analysis. The results of prognostic analyses for the cardinal variables
are summarized in Table 8. In univariate
analysis, CD7 positivity (
We then evaluated the association between CD7 expression and IPSS. The
proportion of CD7+ cases differed between IPSS categories,
that is, 0 of 14 (CD7+ cases per total cases, 0%), 6 of 22 (27.3%), 7 of 17 (41.2%), and 14 of 35 cases (40.0%) in the low,
INT-1, INT-2 and high categories of IPSS, respectively (Table
9, P = .0347). Further, CD7
positivity was associated with a short OS and TFS in the INT-1, INT-2,
and high IPSS categories with statistic significance or
marginal statistical significance (Table 9 and Figure 4E).
Density gradient centrifugation using the BR reagent is suitable for enriching blasts from patients with myeloid malignancies and lymphoid malignancies16 (and Hyodo et al, manuscript in preparation). When this method was applied to normal BM cells, both myeloblasts and immature B cells were able to be enriched. In this study, we used this reagent to enrich MDS blasts and then determined their phenotypic features. MDS is a heterogeneous group of disorders in regard to both the differentiation capacity of the clonal cells and the prognosis. However, in this paper we showed that MDS EBCs from almost all the cases had a common immunophenotype, that is, an immunophenotype of committed myeloid progenitors (CD34+CD38+HLA-DR+CD13+CD33+),27,28 irrespective of the MDS subtype. Prior reports showed that an increase in CD34+ cells in the PB and the BM was associated with poor survival and a higher risk of leukemic transformation in MDS.29-31 In view of the present data that CD34 is expressed by a high percentage of EBCs in nearly all MDS cases, we consider that the prior data simply denote that an increase in blasts in the PB and the BM was associated with a poor prognosis in MDS. Contrary to the common CD34+CD38+HLA-DR+CD13+CD33+ phenotype, MDS EBCs from various proportions of cases expressed other antigens that are expressed on normal myeloid cells more mature than myeloblasts. That is, CD10 was detected in 19% of the cases, CD11b in 48%, CD15 in 64%, and CD16 in 0%. Thus, although the expression profiles of these antigens differ among MDS cases, coexpression of stem cell antigens and late-stage myeloid antigens on myeloblasts (asynchronous expression of antigens, which is well known in de novo AML [reviewed by Stelzer and Goodpasture22]) is common in MDS. In the meantime, expression of antigens restricted to lymphoid cells in normal hematopoiesis, that is, CD2, CD3, CD5, CD8, CD19, and CD20, was very rare for the MDS EBCs. The exception is CD56, whose expression is observed only on NK-cell lineages and a subset of T-cell lineages in healthy subjects, which was expressed on EBCs from 27% of our cases. This is consistent with the data for de novo AML as shown in Table 5 and reported by others.32 The present data, that is, 97% of the cases expressed CD34 and 58% of
the cases were MPO CD33 is a target molecule of antibody target therapy of MDS. In our cohort, EBCs from all MDS cases and 19 of the 21 AL-MDS cases were CD33+, but the percentage of EBCs positive for CD33 was variable. Recently, Estey et al reported a low response rate when MDS patients were treated with an anti-CD33 calicheamicin conjugate.38 It is important to determine whether the response to this MDS therapy is related to the degree of CD33 expression on blasts or some other factor such as expression of multidrug-resistance proteins by blasts. CD117 (RTK c-kit) is another target molecule of antibody target therapy of MDS. A recent report showed that synthetic small-molecule inhibitors of RTK inhibited phosphorylation of c-kit and a signaling event downstream of c-kit activation and induced apoptosis of CD117+ de novo AML blasts in all cases tested.14 Remission induction of an AML case by one of these inhibitors, SU5416, was also reported.39 In our cohort, EBCs from 64% of cases were CD117+, but the percentage of EBCs positive for CD117 was variable. It will be very interesting to determine whether these inhibitors are effective for the treatment of CD117+ MDS cases. CD7 is expressed on T-lineage cells as well as a fraction of CD34+ hematopoietic progenitors, which are capable of differentiating into either T cells or myeloid cells.40,41 CD7+ cells expressing CD13 or CD33 (or both), which lose CD7 expression by differentiation induction, have also been reported.42 In de novo AML, CD7 expression is associated with an immature AML phenotype.20,43 Therefore, CD7 has been proposed as a marker of immaturity in myeloid cells. We have reported a strong association between the cytogenetic data and CD7 expression in 256 de novo AML cases.20 That is, when de novo AML cases were classified according to their cytogenetic data as favorable, intermediate, and unfavorable, the percentage of CD7+ patients increased stepwise from the favorable group to the intermediate and unfavorable groups (4.3%, 36.4%, and 53.2%, respectively, P < .0001). Therefore, we analyzed for cytogenetic data showing a significant association with CD7 expression in the present 116 subjects, but we could not find any significant associations (data not shown). When the phenotype data of 116 cases were examined, expression of CD7
and CD117 (markers of immaturity of myeloid cells) was more frequent in
high-risk MDS and AL-MDS compared with low-risk MDS. In particular, no
low-risk MDS cases were CD7+. Conversely, expression of
CD10 and CD15 (markers of maturation of myeloid cells) was more
frequent in low-risk MDS compared with high-risk MDS and AL-MDS.
Further, increased CD7 expression and reduced CD15 expression, which
are accompanied by disease progression of MDS, were observed in
sequential samples of the same subjects. These data indicate that
during disease progression in MDS, phenotypical clonal evolution
(transition from blasts with a relatively mature phenotype to blasts
with a more immature phenotype) occurs at least in some cases. For 4 of
the 5 cases who showed phenotypical clonal evolution in Table 7,
cytogenetic data were available from both before and after disease
progression (cases 45, 46, 49, and 116). Clonal evolution revealed by
the karyotype was not detected in 2 of the 4 cases (cases 45 and 49)
and was observed only after full transformation to leukemia in case 46. Both clonal evolution (intrinsic changes in clonal cells) and blunted
host defense may cause disease progression in MDS. Hopefully, the EBC immunophenotype will supplement the karyotype data in the detection of
clonal evolution in MDS. There is a possibility that blasts from a
normal clone may be present in EBCs in MDS samples, especially in
low-risk MDS. Nevertheless, this possibility cannot readily explain the
differences in immunophenotype between low-risk MDS, high-risk MDS, and
AL-MDS. This is because we showed in a separate project that the
immunophenotype of myeloblasts, prepared by BR density centrifugation
from hematologically healthy individuals, is
CD13+CD33+CD34+CD117+or We showed that CD7 positivity, with or without consideration of the CD15 expression status, was an independent variable associated with a poor prognosis for MDS. Although the in vivo function of CD7 is largely unknown, it may be involved in T- and NK-cell activation and adhesion as well as production of granulocyte-macrophage colony-stimulating factor by myeloid precursors.44-47 It remains unknown whether these putative functions of CD7, blast immaturity itself, or other factors explain the poor prognosis of CD7+ MDS cases. Regarding de novo AML, there is continued debate over whether CD7 expression is associated with a poor prognosis (for a review, see Ogata et al20). However, in our recent study examining 256 de novo AML cases, we showed a strong association between the cytogenetic data and CD7 expression as described above, which explains why the prognostic value of CD7 expression has been contradictory in de novo AML.20 Further, CD7 expression was associated with an extremely poor prognosis only when de novo AML patients with unfavorable cytogenetics were analyzed.20 The finding that CD7 expression was associated with a poor prognosis in disease groups that per se have a poor prognosis, that is, MDS and de novo AML with unfavorable cytogenetics, is interesting. The biologic background that explains this finding needs to be studied further. In conclusion, this is the first report to clarify the detailed phenotypic features of MDS blasts and their clinical significance. We believe that the data presented here are clinically useful and important for understanding the pathophysiology of MDS.
Submitted January 28, 2002; accepted July 8, 2002.
Prepublished online as Blood First Edition Paper, July 18, 2002; DOI 10.1182/blood-2002-01-0222.
Supported in part by a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science (no. 14571002).
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
Reprints: Kiyoyuki Ogata, Division of Hematology, Third Department of Internal Medicine, Nippon Medical School, Sendagi 1-1-5, Bunkyo-ku, Tokyo 113-8603, Japan; e-mail: ogata{at}nms.ac.jp.
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  T. Yamashita, H. Tamura, C. Satoh, E. Shinya, H. Takahashi, L. Chen, A. Kondo, T. Tsuji, K. Dan, and K. Ogata Functional B7.2 and B7-H2 Molecules on Myeloma Cells Are Associated with a Growth Advantage Clin. Cancer Res., February 1, 2009; 15(3): 770 - 777. [Abstract] [Full Text] [PDF]
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K. Ogata, Y. Kishikawa, C. Satoh, H. Tamura, K. Dan, and A. Hayashi Diagnostic application of flow cytometric characteristics of CD34+ cells in low-grade myelodysplastic syndromes Blood, August 1, 2006; 108(3): 1037 - 1044. [Abstract] [Full Text] [PDF]
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A. Sternberg, S. Killick, T. Littlewood, C. Hatton, A. Peniket, T. Seidl, S. Soneji, J. Leach, D. Bowen, C. Chapman, et al. Evidence for reduced B-cell progenitors in early (low-risk) myelodysplastic syndrome Blood, November 1, 2005; 106(9): 2982 - 2991. [Abstract] [Full Text] [PDF]
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Top
Abstract
Introduction
-naphthyl
butyrate esterase]).
20% of EBCs expressing CD7) was
significantly associated with a short OS (P = .0007,
Figure 