Analysis of CD34-positive cells in bone marrow from patients with myelodysplastic syndromes and acute myeloid leukemia and in normal individuals: a comparison between FACS analysis and immunohistochemistry

Theragnostic strategies harnessing the self-renewal pathways of stem-like cells in the acute myeloid leukemia

Acute myelogenous leukemia (AML) is a genetically heterogeneous and aggressive cancer of the Hematopoietic Stem/progenitor cells. It is distinguished by the uncontrollable clonal growth of malignant myeloid stem cells in the bone marrow, venous blood, and other body tissues. AML is the most predominant of leukemias occurring in adults (25%) and children (15-20%). The relapse after chemotherapy is a major concern in the treatment of AML. The overall 5-year survival rate in young AML patients is about 40-45% whereas in the elderly patients it is less than 10%. Leukemia stem-like cells (LSCs) having the ability to self-renew indefinitely, repopulate and persist longer in the G0/G1 phase play a crucial role in the AML relapse and refractoriness to chemotherapy. Hence, novel treatment strategies and diagnostic biomarkers targeting LSCs are being increasingly investigated. Through this review, we have explored the signaling modulations in the LSCs as the theragnostic targets. The significance of the self-renewal pathways in overcoming the treatment challenges in AML has been highlighted.

Retracted: EBF1 gene promotes the proliferation and inhibits the apoptosis of bone marrow CD34+ cells in patients with myelodysplastic syndrome through negative regulation of mitogen-activated protein kinase axis

The transcription factor, early B cell factor 1 (EBF1), plays a vital role in the lineage specification involving early B cell development and the onset of myelodysplastic syndrome (MDS). Therefore, to investigate whether or not EBF1 affects MDS as well as the transcription factor's underlying mechanism, we used CD34+ hematopoietic stem cells in bone marrow from patients with MDS. The extracted cells were then transfected with a series of EBF1, short hairpin RNA against EBF1 (shEBF1), and SB203580 (a specific mitogen-activated protein kinase [MAPK] axis inhibitor). The effects EBF1 gene and MAPK axis had on cell proliferation, apoptosis, and migration were determined by in vitro cell culturing. We made observations that involved EBF1 inhibiting the messenger RNA (mRNA) level of p38 MAPK, increasing the mRNA levels of extracellular-signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), extracellular-signal-regulated kinase 5 (ERK5), decreasing the protein expression of Bcl-2-associated X protein (Bax), and finally elevating the protein levels of B cell lymphoma/leukemia-2 (Bcl-2), stem cell factor (SCF), erythropoietin receptor (EpoR), p-ERK, p-JNK, p-ERK5, cyclin D, cyclin E, cyclin-dependent kinase 2 (CDK2), and CDK6, implying that EBF1 may very well have an inhibitory role in the MAPK axis. Another discovery found that EBF1 had a positive effect on the promotion of bone marrow CD34+ cell proliferation as well as its migration, but inhibited the apoptosis of cells. The results we obtained from this study indicated that the EBF1 gene suppresses the activation of the MAPK axis, thereby promoting both the proliferation and migration of bone marrow CD34+ cells as well as inhibiting the associating apoptosis. The effects of the EBF1 gene are likely to present a new therapeutic target in preventing the progression of MDS.

The challenging task of enumerating blasts in the bone marrow

Enumeration of blasts in the bone marrow is critical for diagnostic, prognostic, and therapeutic response evaluation in myelodysplastic syndromes, myeloproliferative neoplasms and acute leukemias. However, few studies have examined the accuracy and precision of marrow blast counting using standard microscopic procedures. In our study, 4 experienced hematopathologists evaluated blast percentages in marrow using either differential counts on aspirate smears or visual estimates on CD34-stained trephine biopsies. Results of an independent observer's manual counts of individual labeled and unlabeled cells performed on high resolution digital images of CD34-stained trephine biopsies were designated as the "Digital Reference." Hematopathologists' blast counts showed excellent interobserver reproducibility, but the counts in smears and trephine biopsies correlated poorly with each other. Compared to the Digital Reference, both smear and trephine evaluations showed positive bias and high variability. The biopsy showed less variability but higher positive bias relative to the smears, indicating that counts were overestimated more in the hematopathologists' biopsy evaluation. Flow cytometric counts correlated well with the Digital Reference, and cases with high blast count generally showed worse cytogenetic findings. Our results demonstrate the need for better counting methods if significant decisions are made based on microscopic enumeration of blasts. Further efforts should be made to develop markers to better define blast cells and perhaps incorporate automated digital imaging technologies to enumerate them. Also, consideration should be given to quantifying blasts per marrow area in biopsies instead of per nucleated cells.

Gene expression profiling of erythroblasts from refractory anaemia with ring sideroblasts (RARS) and effects of G-CSF

Refractory anaemia with ring sideroblasts (RARS) is characterized by anaemia, erythroid apoptosis, cytochrome c release and mitochondrial ferritin accumulation. Granulocyte-colony-stimulating factor (G-CSF) inhibits the first three of these features in vitro and in vivo. To dissect the molecular mechanisms underlying the RARS phenotype and anti-apoptotic effects of G-CSF, erythroblasts generated from normal (NBM) and RARS marrow CD34(+) cells were cultured +/-G-CSF and subjected to gene expression analysis (GEP). Several erythropoiesis-associated genes that were deregulated in RARS CD34(+) cells showed normal expression in erythroblasts, underscoring the importance of differentiation-specific GEP. RARS erythroblasts showed a marked deregulation of several pathways including apoptosis, DNA damage repair, mitochondrial function and the JAK/Stat pathway. ABCB7, transporting iron from mitochondria to cytosol and associated with inherited ring sideroblast formation was severely suppressed and expression decreased with differentiation, while increasing in NBM cultures. The same pattern was observed for the mitochondrial integrity gene MFN2. Other downregulated key genes included STAT5B, HSPA5, FANCC and the negative apoptosis regulator MAP3K7. Methylation status of key downregulated genes was normal. The mitochondrial pathway including MFN2 was significantly modified by G-CSF, and several heat shock protein genes were upregulated, as evidence of anti-apoptotic protection of erythropoiesis. By contrast, G-CSF had no effect on iron-transport or erythropoiesis-associated genes.

An updated approach to the diagnosis of myeloid leukemia cutis

The diagnosis of myeloid leukemia cutis can be difficult, particularly in the context of an initial skin biopsy with a malignant hematopoietic neoplasm. We studied the immunohistochemical characteristics of 33 cases of myeloid leukemia cutis diagnosed at Stanford University Medical Center, Stanford, CA, 1996-2007, and compared them with the corresponding bone marrow blast immunophenotype and World Health Organization classification (2008). In the skin, CD43 marked 97% of cases (32/33), myeloperoxidase marked 42% (14/33), CD68 marked 94% (31/33), CD163 marked 25% (7/28), and CD56 marked 47% (14/30). CD34 and CD117 were predominantly negative. In 19 cases in which myeloperoxidase was negative, all marked with CD68 and CD43. The flow cytometric immunophenotype of the leukemic blasts in the bone marrow was discordant with the immunohistochemical profile in the skin in all cases, showing loss or gain of at least 1 antigen. Given the immunophenotypic differences between skin and bone marrow blasts, we provide an updated immunohistochemical approach to the diagnosis of myeloid leukemia cutis.

High-resolution whole genome tiling path array CGH analysis of CD34+ cells from patients with low-risk myelodysplastic syndromes reveals cryptic copy number alterations and predicts overall and leukemia-free survival

Myelodysplastic syndromes (MDSs) pose an important diagnostic and treatment challenge because of the genetic heterogeneity and poorly understood biology of the disease. To investigate initiating genomic alterations and the potential prognostic significance of cryptic genomic changes in low-risk MDS, we performed whole genome tiling path array comparative genomic hybridization (aCGH) on CD34+ cells from 44 patients with an International Prognostic Scoring System score less than or equal to 1.0. Clonal copy number differences were detected in cells from 36 of 44 patients. In contrast, cells from only 16 of the 44 patients displayed karyotypic abnormalities. Although most patients had normal karyotype, aCGH identified 21 recurring copy number alterations. Examples of frequent cryptic alterations included gains at 11q24.2-qter, 17q11.2, and 17q12 and losses at 2q33.1-q33.2, 5q13.1-q13.2, and 10q21.3. Maintenance of genomic integrity defined as less than 3 Mb total disruption of the genome correlated with better overall survival (P = .002) and was less frequently associated with transformation to acute myeloid leukemia (P = .033). This study suggests a potential role for the use of aCGH in the clinical workup of MDS patients.

Exisulind induces apoptosis in advanced myelodysplastic syndrome (MDS) and acute myeloid leukaemia/MDS

The influence of Exisulind on the viability and apoptosis of CD34(+) stem cells from patients with advanced myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML)/MDS was investigated. In eight out of 10 patient samples Exisulind reduced the fraction of viable cells by inducing apoptosis. We found evidence that Exisulind-mediated apoptosis depends on c-Jun NH(2)-terminal kinase (JNK) activation. Addition of a specific JNK-inhibitor to Exisulind-treated advanced MDS and AML/MDS cells partly abrogated apoptosis. We propose that Exisulind is tested in clinical phase I/II trials for the treatment of advanced MDS and AML/MDS.

Evaluation of CD7 and terminal deoxynucleotidyl transferase (TdT) expression in CD34+ myeloblasts from patients with myelodysplastic syndrome

There is an emerging use of flow cytometry to evaluate patients with myelodysplastic syndrome (MDS). We have studied CD7 and TdT expression in the CD34+ myeloid blast cell population in 55 bone marrow samples of patients with MDS. CD7 and/or TdT were detected in 38 out of 55 patients (69%). CD7 expression was not related to other bad prognosis data but conversely, we found an association between TdT+ CD34 myeloblasts and high-risk MDS patients according to the International Prognostic Scoring System. Therefore, CD7 and TdT may help to establish the diagnosis of MDS and, TdT expression also seems to be a useful marker in distinguishing risk groups.

Angiogenesis in relation to clinical stage, apoptosis and prognostic score in myelodysplastic syndromes

The International Prognostic Scoring System (IPSS), based on the number of cytopenias, percentage of bone marrow blasts and cytogenetics, is an important prognostic tool for patients with myelodysplastic syndrome (MDS). In addition, factors such as high bone marrow cellularity and lactate dehydrogenase levels have been associated with an adverse outcome, spontaneously and after chemotherapy. Recently, increased bone marrow angiogenesis, measured as, e.g. microvascular density (MVD), was reported to be more intense in high-risk than in low-risk MDS. To assess the prognostic role of MVD in MDS, a cohort of 56 patients, thoroughly investigated for various clinical and morphological parameters, were followed-up for survival > or =60 months after the diagnostic analysis. As a group MDS patients had higher MVD compared to healthy controls (p<0.02). The highest median MVD value was observed in the RAEB group, but there was no overall significant difference between the FAB groups. No significant correlations were observed between MVD and peripheral blood counts, bone marrow cellularity, percentage of bone marrow blasts and CD34 positive cells, apoptotic index (TUNEL), proliferation index (MIB-1), erythroid index, FAB group and IPSS score. MVD was not correlated to overall survival. In contrast, bone marrow blast count <5%, low or normal cellularity, as well as a high erythroid index, indicated a favorable survival. Thus, our data do not support an important prognostic role of angiogenesis, reflected by microvessel density, in the myelodysplastic syndromes.

Evidence for expression of early myeloid antigens in mature, non-blast myeloid cells in myelodysplasia

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders with frequent cytogenetic abnormalities. They can arise de novo or be related to therapy. Although blasts in MDS have been studied extensively, there is little information available on the mature, non-blast myeloid cells (NBMCs). We used a retrospective case-control study design. NBMC populations in MDS (48 cases) and in tumor-free control (12 cases) bone marrow samples were analyzed using multiparameter flow cytometry for mean side scatter (SSC) channel number and for expression of aberrant cell surface antigens. MDS cases were stratified on the basis of cytogenetic abnormalities. We report that NBMCs in MDS with normal karyotype expressed significantly higher HLA-DR than controls (P = 0.034). NBMCs in MDS cases with cytogenetic abnormalities and with > or =5% marrow blasts, compared with controls, had significantly higher CD34 and higher HLA-DR but lower CD10 and lower SSC mean channel number. CD34 expression in NBMCs was significantly greater in therapy-related MDS compared with de novo MDS ( P = 0.01), although the presence of cytogenetic abnormalities was not different ( P > 0.05). These data suggest that bone marrow, mature, NBMCs have phenotypic changes in MDS that are not seen in normal controls.

Therapy-related changes of CD34+ progenitor cells in chronic myeloid leukemia: a morphometric study on sequential trephine biopsies

In chronic myeloid leukemia (CML), it has been assumed that the number of CD34(+) progenitor cells (PGCs) provides useful diagnostic and prognostic information regarding the evolution of accelerated phase and blastic crisis. However, until now no information is available about changes of this peculiar precursor cell population during therapy or possible associations with the other bone marrow constituents. For this reason, a retrospective clinicopathological study was performed on 83 patients with CML including 209 sequential bone marrow biopsies (intervals ranging between 6 and 143 months) and immunohistological staining of CD34(+) cells (QBEND10), megakaryocyte precursors (CD61), and erythropoiesis (Ret 40f). According to treatment modalities, three different groups of patients could be distinguished that received either monotherapy by interferon-alpha2b (IFN-alpha2b) or hydroxyurea (HU) and a combination of both. In comparison with a control group, morphometry revealed a significant increase in the quantity of CD34(+) PGCs per hematopoiesis (cellularity) in the CML bone marrow before treatment. Independently of treatment modalities and presentation of clinical findings nonresponding patients were generally characterized by a higher amount of progenitors in the initial biopsy specimens. Furthermore, calculation of the CD34(+) cell growth index showed a significant and rapid progression in nonresponding patients and in those developing an accelerated or blastic phase during therapy. This feature was prominently expressed following IFN treatment and related to a failing regeneration of nucleated erythroid precursors. In patients with a myelofibrotic bone marrow at onset no differences in the number of CD34(+) PGCs were recognizable in the pretreatment biopsies. This finding contrasted a significant and gradual change in progenitor cell frequency under treatment and evolving myelofibrosis. Opposed to HU therapy, the latter feature was explicitly detectable in the IFN group. In conclusion, the incidence of CD34(+) PGCs in the CML bone marrow reflects therapeutic efficacy. By demonstrating a significant relationship between fiber content and quantity of CD34(+) cells during treatment, experimental findings concerning the complex functional interactions between the fibrous stroma compartment and progenitor cell differentiation and proliferation are elucidated.

Diagnostic utility of flow cytometric immunophenotyping in myelodysplastic syndrome

The myelodysplastic syndromes (MDSs) are characterized by bilineage or trilineage dysplasia. Although diagnostic criteria are well established for MDS, a significant number of patients have blood and bone marrow findings that make diagnosis and classification difficult. Flow cytometric immunophenotyping is an accurate and highly sensitive method for detection of quantitative and qualitative abnormalities in hematopoietic cells. Flow cytometry was used to study hematopoietic cell populations in the bone marrow of 45 patients with straightforward MDS. The results were compared with those obtained in a series of patients with aplastic anemia, healthy donors, and patients with a history of nonmyeloid neoplasia in complete remission. The immunophenotypic abnormalities associated with MDS were defined, and the diagnostic utility of flow cytometry was compared, with morphologic and cytogenetic evaluations in 20 difficult cases. Although morphology and cytogenetics were adequate for diagnosis in most cases, flow cytometry could detect immunophenotypic abnormalities in cases when combined morphology and cytogenetics were nondiagnostic. It is concluded that flow cytometric immunophenotyping may help establish the diagnosis of MDS, especially when morphology and cytogenetics are indeterminate. (Blood. 2001;98:979-987)

Immunophenotypic profile of myeloid cells in granulocytic sarcoma by immunohistochemistry. Correlation with blast differentiation in bone marrow

The present study was designed to evaluate the lineage differentiation (particularly monocytic differentiation) of immature myeloid cells in granulocytic sarcoma (GS) by immunohistochemistry and correlate the results with lineage differentiation of blasts in the bone marrow and to determine the degree of maturation of the infiltrating myeloid cells in GS by immunohistochemistry using CD34 and HLA-DR. Immunohistochemical stains were performed on paraffin-embedded tissue from 17 GS lesions with lineage-associated markers: myeloperoxidase, CD68 (KP1), CD68 (PG-Ml), glycophorin A, factor VIII, and CD56; and with markers for blasts and immature myeloid cells: CD34 and HLA-DR. Our results show that positive staining with PG-M1, but not KP1, suggests monocytic differentiation of myeloid cells in GS and correlates with the monocytic differentiation of blasts in the bone marrow. Expression of CD56 is frequent in GS, especially when the marrow blasts have monocytic differentiation, and should not be interpreted as a primary natural-killer cell process. The immature myeloid cells in GS are frequently HLA-DR positive. However, CD34 positivity of the immature myeloid cells is relatively uncommon, except in cases with underlying myelodysplastic syndrome or chronic myelogenous leukemia.

Growth characteristics of myelodysplastic CD34+ cells

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis entailing hyperproliferative and ineffective hematopoiesis associated with morphologic evidence of marrow cell dysplasia resulting in refractory cytopenia(s), and an increased risk of transformation into acute myeloblastic leukemia (AML). The administration of colony-stimulating factor(s) (CSFs) to patients with MDS increased blood neutrophil concentrations, in most patients, and it was anticipated to be of benefit to prevent infections. The progression to AML while being treated with CSFs has come under close scrutiny. In vitro studies are expected to produce more pertinent criteria for selection of patients who are likely to benefit, as well as the overall benefits of various therapies. For this purpose, in vitro colony assays are an excellent approach for investigation of the biologic characteristics of MDS progenitor cells. The stem cell phenotype CD34 is the one of the best markers of progenitor cells, and can be used for the purification of these cells to unify levels of maturation; a direct comparison of proliferative and differentiative capacity of MDS progenitor cells with normal CD34+ cells can thus be made. The properties of MDS CD34+ cells are described here in association with proliferation and differentiation, with special emphasis on the role of stem cell factor (a ligand for c-kit) in leukemic type growth of MDS CD34+ cells.