Proliferative and anti-apoptotic fractions in maturing hematopoietic cell lineages and their role in homeostasis of normal bone marrow.

Recent developments in clinical flow cytometry allow the simultaneous assessment of proliferative and anti-apoptotic activity in the different hematopoietic cell lineages and during their maturation process. This can further advance the flow cytometric diagnosis of myeloid malignancies. In this study we established indicative reference values for the Ki-67 proliferation index and Bcl-2 anti-apoptotic index in blast cells, as well as maturing erythroid, myeloid, and monocytic cells from normal bone marrow (BM). Furthermore, the cell fractions co-expressing both proliferation and anti-apoptotic markers were quantified. Fifty BM aspirates from femoral heads of patients undergoing hip replacement were included in this study. Ten-color/twelve-parameter flow cytometry in combination with a software-based maturation tool was used for immunophenotypic analysis of Ki-67 and Bcl-2 positive fractions during the erythro-, myelo-, and monopoiesis. Indicative reference values for the Ki-67 and Bcl-2 positive fractions were established for different relevant hematopoietic cell populations in healthy BM. Ki-67 and Bcl-2 were equally expressed in the total CD34 positive blast cell compartment and 30% of Ki-67 positive blast cells also showed Bcl-2 positivity. The Ki-67 and Bcl-2 positive fractions were highest in the more immature erythroid, myeloid and monocytic cells. Both fractions then gradually declined during the subsequent maturation phases of these cell lineages. We present a novel application of an earlier developed assay that allows the simultaneous determination of the Ki-67 proliferative and Bcl-2 anti-apoptotic indices in maturing hematopoietic cell populations of the BM. Their differential expression levels during the maturation process were in accordance with the demand and lifespan of these cell populations. The indicative reference values established in this study can act as a baseline for further cell biological and biomedical studies involving hematological malignancies.

Rac1/pSTAT3 expression: A pharmacodynamic marker panel as a first step toward optimization of thiopurine therapy in inflammatory bowel disease patients.

Thiopurine derivatives, such as azathioprine and mercaptopurine, are standard conventional treatment options in inflammatory bowel disease (IBD). Unfortunately, approximately half of patients discontinue thiopurine therapy within 2 years. To improve the prediction of clinical effectiveness, thiopurine therapy is currently optimized using therapeutic drug monitoring. Ras-related C3 botulinum toxin substrate 1 (Rac1) has been suggested as a potential pharmacodynamic marker of the thiopurine effect in lymphocytes. The active thiopurine metabolite 6-thioguanine triphosphate (6-Thio-GTP) causes T cell apoptosis via Rac1 and the downstream transcription factor signal transducer and activator of transcription 3 (STAT3). The aim of this study was to develop and validate a functional pharmacodynamic multiparameter flow cytometric assay to determine Rac1/pSTAT3 expression in the various leukocyte subpopulations in peripheral blood in order to predict therapeutic response in IBD patients in the future. Peripheral blood samples of healthy subjects (no fever or clinical complaints of active disease, C-reactive protein < 10 mg/L) were used for immunocytochemical labeling, applying an optimized fixation and permeabilization strategy. A gating procedure was performed to separate all leukocyte subpopulations. Quantitative data were obtained by measuring presence and median fluorescent intensity. In vitro, Rac1 presence and expression were detectable in all leukocyte subpopulations. After IL-6 stimulation, used as proxy for inflammation, a distinct pSTAT3 signal could be detected in T lymphocytes of healthy subjects. In vivo, an upregulated pSTAT3 signal was detected in nearly all IBD patients with active disease and differed substantially from the signal found in IBD patients in remission on thiopurines and healthy subjects. We developed and validated a functional flow cytometric assay to assess Rac1 and pSTAT3 presence and expression. This opens a venue for a pharmacodynamic assay to predict thiopurine effectiveness in IBD patients.

Determination of the proliferative fractions in differentiating hematopoietic cell lineages of normal bone marrow.

Because of the proven prognostic value of Ki-67 as a proliferation marker in several types of solid cancers, our goal is to develop and validate a multiparameter flow cytometric assay for the determination of the Ki-67 expression in hemato-oncological diseases. The aim of the present study was to establish the reference values for the fraction of Ki-67 positive cells in and during maturation of individual hematopoietic cell lineages present in normal bone marrow. Aspirates derived from femoral heads of 50 patients undergoing a hip replacement were used for the flow cytometric quantification of Ki-67 expression in the different hematopoietic cell populations of healthy bone marrow. Furthermore, the proliferative index was investigated in detail for the maturation steps during erythro-, myelo-, and monopoiesis using recently described immunophenotypic profiles in combination with a software-based maturation tool. Reference values for the proliferative index were established for different relevant hematopoietic cell populations in healthy bone marrow. During maturation, the size of the Ki-67 positive fraction was the highest in the most immature compartment of the myeloid, monocytic, and erythroid cell lineages, followed by a steady decline upon cell maturation. While proerythroblasts showed a proliferative activity of almost 100%, the myelo- and monoblast showed a lower proliferative index of on average of 50%, indicating that a relatively large proportion of these cells exist in a quiescent state. In conclusion, we can state that when using a novel combination of immunophenotypic markers, the proliferation marker (Ki-67) and a software-based maturation tool, it was possible to determine the proliferative fractions in the diverse hematopoietic cell lineages in bone marrow, in particular during maturation. Using this approach, the proliferative indices for the normal myelo-, mono-, and erythropoiesis were determined, which can be used as a reference in future studies of hematologic malignancies originating from bone marrow. © 2018 International Society for Advancement of Cytometry.

MDS and AML show elevated fractions of CD34-positive blast cell populations with a high anti-apoptotic versus proliferation ratio.

This study investigates the intertwined processes of (anti-)apoptosis and cell proliferation in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). Utilizing antibodies to Bcl-2 and Ki-67, the CD34-positive blast cell compartments in bone marrow aspirates from 50 non-malignant cases, 25 MDS patients, and 25 AML patients were analyzed for their anti-apoptotic and proliferative cell fractions through ten-color flow cytometry. MDS patients exhibited a significantly increased anti-apoptotic (p=0.0014) and reduced proliferative cell fraction (p=0.0030) in their blast cell population as compared to non-malignant cases. AML patients showed an even more exacerbated trend than MDS patients. The resulting Bcl-2:Ki-67 cell fraction ratios in MDS and AML were significantly increased as compared to the non-malignant cases (p=0.0004 and p<0.0001, respectively). AML patients displayed, however, a high degree of variability in their anti-apoptotic and proliferation index, attributed to heterogeneity in maturation stage and severity of the disease at diagnosis. Using double-labeling for Bcl-2 and Ki-67 it could be shown that besides blast cells with a mutually exclusive Ki-67 and Bcl-2 expression, also blast cells concurrently exhibiting anti-apoptotic and proliferative marker expression were found. Integrating these two dynamic markers into MDS and AML diagnostic workups may enable informed conclusions about their biological behavior, facilitating individualized therapy decisions for patients.

Impact of the gating strategy for Ki-67 and Bcl-2 on the determination of proliferation and anti-apoptosis data by flow cytometry in non-malignant bone marrow aspirates and aspirates from patients with myeloid malignancies.

This Data in Brief article displays a flow cytometric assay that was used for the acquisition and analyses of proliferative and anti-apoptotic activity in hematopoietic cells. This dataset includes analyses of the Ki-67 positive fraction (Ki-67 proliferation index) and Bcl-2 positive fraction (Bcl-2 anti-apoptotic index) of the different myeloid bone marrow (BM) cell populations in non-malignant BM, and in BM disorders, i.e. myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). The present dataset comprises 1) the percentage of the CD34 positive blast cells, erythroid cells, myeloid cells and monocytic cells, and 2) the determined Ki-67 positive fraction and Bcl-2 positive fraction of these cell populations in tabular form. This allows the comparison and reproduction of the data when these analyses are repeated in a different setting. Because gating the Ki-67 positive and Bcl-2 positive cells is a critical step in this assay, different gating approaches were compared to determine the most sensitive and specific approach. BM cells from aspirates of 50 non-malignant, 25 MDS and 27 AML cases were stained with 7 different antibody panels and subjected to flow cytometry for determination of the Ki-67 positive cells and Bcl-2 positive cells of the different myeloid cell populations. The Ki-67 or Bcl-2 positive cells were then divided by the total number of cells of the respective cell population to generate the Ki-67 positive fraction (Ki-67 proliferation index) or the Bcl-2 positive fraction (Bcl-2 anti-apoptotic index). The presented data may facilitate the establishment and standardization of flow cytometric analyses of the Ki-67 proliferation index and Bcl-2 anti-apoptotic index of the different myeloid cell populations in non-malignant BM as well as MDS and AML patients in other laboratories. Directions for proper gating of the Ki-67 positive and Bcl-2 positive fraction are crucial for achieving standardization among different laboratories. In addition, the data and the presented assay allows application of Ki-67 and Bcl-2 in a research and clinical setting and this approach can serve as the basis for optimization of the gating strategy and subsequent investigation of other cell biological processes besides proliferation and anti-apoptosis. These data can also promote future research into the role of these parameters in diagnosis of myeloid malignancies, prognosis of myeloid malignancies and therapeutic resistance against anti-cancer therapies in these malignancies. As specific populations were identified based on cell biological characteristics, these data can be useful for evaluating gating algorithms in flow cytometry in general by confirming the outcome (e.g. MDS or AML diagnosis) with the respective proliferation and anti-apoptotic profile of these malignancies. The Ki-67 proliferation index and Bcl-2 anti-apoptotic index may potentially be used for classification of MDS and AML based on supervised machine learning algorithms, while unsupervised machine learning can be deployed at the level of single cells to potentially distinguish non-malignant from malignant cells in the identification of minimal residual disease. Therefore, the present dataset may be of interest for internist-hematologists, immunologists with affinity for hemato-oncology, clinical chemists with sub-specialization of hematology and researchers in the field of hemato-oncology.

Integration of the Ki-67 proliferation index into the Ogata score improves its diagnostic sensitivity for low-grade myelodysplastic syndromes.

BACKGROUND: Although flow cytometric detection of myelodysplastic syndrome (MDS) with the Ogata score has a high specificity, its sensitivity for low-grade MDS is low. Additional markers are needed to improve its diagnostic reliability. Therefore, we investigated the diagnostic performance of the Ki-67 proliferation index in bone marrow (BM) cell populations for detection of MDS. METHODS: BM aspirates from 50 MDS patients and 20 non-clonal cytopenic controls were analyzed with flow cytometry to determine the Ogata score and the Ki-67 proliferation indices in different cell populations. RESULTS: Ki-67 proliferation indices alone could be used to detect MDS with a sensitivity of up to 80 % and specificity of up to 70 %. Combining the Ogata score with the Ki-67 proliferation index of erythroid cells significantly improved its sensitivity for detection of MDS from 66 % to 90 %, while maintaining a specificity of 100 %. Particularly, the sensitivity for detection of low-grade MDS improved from 56 % to 91 %. CONCLUSIONS: This is the first study using Ki-67 proliferation indices to detect MDS and shows their particularly high diagnostic sensitivity for detection of low-grade MDS. Integration of the Ki-67 proliferation index of erythroid cells into the Ogata score significantly improved its sensitivity without loss of the high specificity.

Optimized gating strategy and supporting flow cytometry data for the determination of the Ki-67 proliferation index in the diagnosis of myelodysplastic syndrome.

This Data in Brief article presents a novel flow cytometric assay used to acquire and process the data presented and discussed in the research paper by Mestrum et al., co-submitted to Leukemia Research, entitled: "Integration of the Ki-67 proliferation index into the Ogata score improves its diagnostic sensitivity for low-grade myelodysplastic syndromes." [1]. The dataset includes the gated fractions of the different myeloid populations in bone marrow (BM) aspirates (total BM cells, CD34 positive blast cells, erythroid cells, granulocytes and monocytes. The raw data is hosted in FlowRepository, while the analyzed data of 1) the fractions of the different myeloid cell populations and 2) the Ki-67 proliferation indices of these myeloid cell populations are provided in tabular form to allow comparison and reproduction of the data when such analyses are performed in a different setting. BM cells from aspirates of 50 myelodysplastic syndrome (MDS) patients and 20 non-clonal cytopenic controls were stained using specific antibody panels and proper fixation and permeabilization to determine the Ki-67 proliferation indices of the different myeloid cell populations. Data was acquired with the three laser, 10-color Navios™ Flow cytometer (Beckman Coulter, Marseille, France) with a blue diode Argon laser (488 nm, 22 mW), red diode Helium/Neon laser (638 nm, 25 mW) and violet air-cooled solid-state diode laser laser (405 nm, 50 mW). A minimum of 100,000 relevant events were acquired per sample, while we aimed at acquiring 500,000 events per sample. Gating was performed with the Infinicyt v2.0 software package (Cytognos SL, Salamanca, Spain). These data may guide the development and standardization of the flow cytometric analysis of the Ki-67 proliferation index (and other markers for cell behavior) for differentiation between non-clonal cytopenic patients and MDS patients. In addition, this assay may be used in myeloid malignancies for research and clinical purposes in other laboratories. This data can be used to encourage future research regarding stem-/progenitor cell resistance against anti-cancer therapies for myeloid malignancies, diagnostics of myeloid malignancies and prognosis of myeloid malignancies. Therefore, these data are of relevance to internist-hematologists, clinical chemists with sub-specialization of hematology and hemato-oncology oriented researchers.

A report on the potential of Rac1/pSTAT3 protein levels in T lymphocytes to assess the pharmacodynamic effect of thiopurine therapy in Inflammatory Bowel Disease patients.

The thiopurine derivatives azathioprine (AZA), mercaptopurine (MP) and tioguanine (TG) remain standard treatment of inflammatory bowel disease (IBD). The immune suppressive effect of thiopurines is primarily based on blocking the Ras-related C3 botulinum toxin substrate 1 (Rac1) causing apoptosis of T lymphocytes by inhibition of the phosphorylated downstream transcription factor Signal Transducer and Activator of Transcription 3 (pSTAT3). A functional pharmacodynamic marker in T lymphocytes may be useful to predict therapeutic outcome of thiopurine therapy. The aim of this study was to explore whether protein levels of Rac1 and pSTAT3 in T lymphocytes may be applied as a specific pharmacodynamic marker for thiopurine therapy in IBD patients. Rac1 and pSTAT3 protein levels in T lymphocytes were explored in 57 IBD patients (median age 51 years, 56% female), subdivided into six groups based on IBD activity and its treatment: patients with active disease without IBD maintenance medication (1) or patients in remission on AZA/MP (2), TG (3), infliximab (IFX) (4), thiopurine and IFX combination-treatment (5) or without IBD medication (6). Reference values were obtained from healthy subjects. Rac1 and pSTAT3 protein levels in T lymphocytes from patients on thiopurine monotherapy (group 2 and 3) were compared to the other groups, and to healthy subjects. Absolute Rac1 and pSTAT3 protein levels showed no differences between the thiopurine monotherapy groups when compared to patients with active disease. However, the ratio of Rac1 and pSTAT3 protein levels was lower in thiopurine patients groups compared to patients with active disease. Rac1-corrected pSTAT3 protein levels may serve as a pharmacodynamic marker of thiopurine monotherapy and may be a potential tool to predict therapeutic effectiveness in IBD patients.

Proliferative activity is disturbed in myeloproliferative neoplasms (MPN), myelodysplastic syndrome (MDS), and MDS/MPN diseases. Differences between MDS and MDS/MPN.

The proliferation marker Ki-67 is widely used within the field of diagnostic histopathology as a prognostic marker for solid cancers. However, Ki-67 is hardly used for prognostic and diagnostic purposes in flow cytometric analyses of hematologic neoplasms. In the present study, we investigated to what extent the proliferative activity, as determined by Ki-67 expression, is disturbed in myeloproliferative neoplasms (MPN), myelodysplastic syndrome (MDS), and MDS/MPN diseases. Bone marrow aspirates from 74 patients suffering from MPN, MDS, or MDS/MPN, and aspirates from 50 non-malignant cases were analyzed by flow cytometry for Ki-67 expression in the erythro-, myelo-, and monopoiesis. Ki-67 expression was used to investigate the proliferative activity during the various maturation steps within these hematopoietic cell lineages. In the MPN patient cohort, the proliferative activity of all cell lineages is significantly higher during almost all maturation stages compared to those of the benign control cohort. In the MDS and MDS/MPN cohort, a significantly lower proliferative activity is observed in the early maturation stages. In the MDS/MPN patient cohort, increased proliferative activity is seen in the later stages of the maturation. MDS and MDS/MPN display a distinct pattern in the proliferating fraction of maturing hematopoietic cells. This could become of added value in order to classify these malignancies based on their biological background and behavior, as well as in gaining a better understanding into the pathobiology of these malignancies.

Increased osteopontin plasma levels in multiple sclerosis patients correlate with bone-specific markers.

The pro-inflammatory cytokine osteopontin has been found to be highly expressed in multiple sclerosis lesions and plasma levels are increased during relapses in relapse-onset multiple sclerosis patients. The objective was to determine the relationship between osteopontin plasma and cerebrospinal fluid levels in relation to the immunoglobulin G index. In addition, osteopontin plasma levels were compared with osteopontin mRNA levels in peripheral blood mononuclear cells and bone-specific markers to analyse whether osteopontin may be peripherally produced. Osteopontin and bone-specific markers were determined in paired plasma-cerebrospinal fluid samples and serum samples of relapse-onset multiple sclerosis patients (n = 36), respectively. Osteopontin mRNA levels were determined by quantitative polymerase chain reaction analysis. Compared to healthy controls (n = 20), plasma osteopontin levels were significantly increased in relapsing-remitting multiple sclerosis patients and correlated (r = 0.43, p = 0.013) with the immunoglobulin G index. In contrast, cerebrospinal fluid osteopontin levels correlated neither with plasma osteopontin in paired samples nor with the immunoglobulin G index. Since osteopontin mRNA levels in peripheral blood mononuclear cells of relapsing-remitting multiple sclerosis patients did not correlate with osteopontin plasma levels, peripheral blood mononuclear cells might not be the major source for the increased osteopontin plasma levels. Osteopontin plasma levels correlated (r = 0.42, p = 0.035) with the bone-specific degradation product C-telopeptide of type-1 collagen. In addition, another immunomodulatory molecule involved in bone metabolism, 25-OH vitamin D, correlated negatively (r = -0.359, p = 0.048) with the immunoglobulin G index. This study suggests that bone-related molecules like osteopontin and vitamin D with important immunomodulatory functions are related to the immunoglobulin G index in relapsing-remitting multiple sclerosis patients.