Myelodysplastic syndromes: immunohistochemical and morphometric evaluation of proliferative activity in erythropoiesis and endoreduplicative capacity of megakaryocytes

The potential of proliferative and apoptotic parameters in clinical flow cytometry of myeloid malignancies

Standardization of the detection and quantification of leukocyte differentiation markers by the EuroFlow Consortium has led to a major step forward in the integration of flow cytometry into classification of leukemia and lymphoma. In our opinion, this now enables introduction of markers for more dynamic parameters, such as proliferative and (anti)apoptotic markers, which have proven their value in the field of histopathology in the diagnostic process of solid tumors and lymphoma. Although use of proliferative and (anti)apoptotic markers as objective parameters in the diagnostic process of myeloid malignancies was studied in the past decades, this did not result in the incorporation of these biomarkers into clinical diagnosis. This review addresses the potential of these markers for implementation in the current, state-of-the-art multiparameter analysis of myeloid malignancies. The reviewed studies clearly recognize the importance of proliferation and apoptotic mechanisms in the pathogenesis of bone marrow (BM) malignancies. The literature is, however, contradictory on the role of these processes in myelodysplastic syndrome (MDS), MDS/myeloproliferative neoplasms, and acute myeloid leukemia. Furthermore, several studies underline the need for the analysis of the proliferative and apoptotic rates in subsets of hematopoietic BM cell lineages and argue that these results can have diagnostic and prognostic value in patients with myeloid malignancies. Recent developments in multiparameter flow cytometry now allow quantification of proliferative and (anti)apoptotic indicators in myeloid cells during their different maturation stages of separate hematopoietic cell lineages. This will lead to a better understanding of the biology and pathogenesis of these malignancies.

The role of monocyte-derived cells and inflammation in baboon ductus arteriosus remodeling

Inflammatory processes play a crucial role in the pathogenesis of atherosclerosis and other vascular disorders. We hypothesized that ischemia of the ductus arteriosus might initiate an active inflammatory response that could play a role in ductus remodeling and permanent closure. To test this hypothesis, we studied effects of postnatal ductus construction on inflammatory processes and remodeling in late-gestation fetal and newborn baboons, and preterm newborn baboons. After postnatal ductus constriction, the expression of several genes known to be essential for atherosclerotic remodeling [vascular cell adhesion molecule (VCAM)-1, E-selectin, IL-8, macrophage colony stimulating factor-1, CD154, interferon-gamma, IL-6, and tumor necrosis factor-alpha] was increased in the ductus wall. We were unable to detect intercellular adhesion molecule (ICAM)-1, ICAM-2, P-selectin, monocyte chemoattractant protein-1, or IL-1 by either real-time PCR or immunohistochemistry. VCAM-1, which is newly expressed by luminal cells of the closed ductus, is an important ligand for the mononuclear cell adhesion receptor VLA4. After postnatal constriction, VLA4+ monocytes/macrophages (CD68+ and CD14+) and, to a lesser extent, T-lymphocytes adhered to the ductus wall. Neutrophils and platelets were not observed. The extent of postnatal neointimal remodeling (both endothelial cell layering and subendothelial space thickening) was associated with the degree of mononuclear cell adhesion. Similarly, the extent of vasa vasorum ingrowth correlated with the invasion of CD68+ cells, from the adventitia into the muscle media. Based on these data, we conclude that the inflammatory response following postnatal ductus constriction may be as necessary for ductus remodeling as it is for atherosclerotic remodeling.

Defective megakaryocytic development in myelodysplastic syndromes

Megakaryocytic proliferation and differentiation is typically abnormal in patients with myelodysplastic syndromes (MDS). The underlying mechanisms for this finding are not known, but may involve defects at the level of the thrombopoietin-receptor (c-mpl) or post-receptor signaling pathways in megakaryocyte progenitor cells. Premature apoptosis of the bone marrow cells and inhibitory effects of cytokines such as tumor necrosis factor alpha have been implicated as contributing to altered megakaryopoiesis in MDS, but their significance remains unclear. The availability of thrombopoietin (TPO) has facilitated more detailed analysis of megakaryocytic biology using several experimental in-vitro systems. However numerous studies have shown that the developmental abnormalities of MDS megakaryocytes could not be corrected by TPO. Increasing investigations are being extended to the evaluation of signal transduction pathways of c-mpl both in cell lines and human hematopoietic cells in order to identify the molecular mechanisms responsible for the defective megakaryocytic development in MDS.

The diagnostic and prognostic value of bone marrow immunostaining in myelodysplastic syndromes

Immunohistochemistry has been introduced as a means of increasing the diagnostic accuracy of bone marrow biopsy (BMB) in myelodysplastic syndromes (MDS); more recently the possibility of coupling immunostaining with other investigational techniques has broadened the spectrum of applications to the biology and physiopathology of MDS. Using panels of monoclonal antibodies (MoAbs), various histological classifications of MDS have been proposed as an alternative to the FAB criteria. The use of lineage-specific MoAbs has allowed a deeper insight into the dysplastic features of early hematopoietic precursors. The study of various gene products involved in the regulation of cell growth, proliferation and sensitivity to antineoplastic drugs, has revealed significant differences between MDS and morphologically-related disorders, particularly acute myelogenous leukemias (AML); these can be considered markers of a biological difference between the two groups of disorders and deserve consideration when designing therapeutic strategies for MDS. Both an increase in the percentage of cell positivity for the CD34 glycoprotein and a tendency of positive cells towards forming aggregates have been shown to be reliable predictors of leukemic transformation and survival, irrespective of the FAB subtype; furthermore, CD34 positivity has also proved to be a better prognostic factor than the presence of the abnormal localization of immature precursors (ALIP) on BMB. Finally, the simultaneous occurrence of "large" and CD34 positive aggregates can be proposed as a means of recognizing MDS patients with an exceedingly unfavourable prognosis, and who are therefore suitable for early aggressive therapy.

Ploidy Analysis and Ki-67 Expression in Myelodysplastic Syndromes

BACKGROUND

The Myelodysplastic Syndromes (MDS) are disorders involving clonal proliferative activity in the bone marrow that can lead to marrow failure and acute leukemia. This study was undertaken to evaluate the relationships between clinical factors, type of MDS, DNA ploidy, and Ki-67 expression.

DESIGN

Air-dried bone marrow smears from 27 patients were Feulgen stained for DNA and analyzed using the CAS 200 image analyzer. Ki-67 expression was also examined by image analysis in 25 of these cases in bone marrow core biopsy specimens using the monoclonal antibody MIB-1. Age, sex, bone marrow cellularity, and MDS grade of each patient were also recorded. Percent S-phase was assessed only for the diploid samples.

RESULTS

There were 16 diploid and 11 aneuploid cases on analysis of Feulgen-stained bone marrow aspirate smears. The percentage of MIB-1+ cells ranged from 6.4%-61.7% (mean-37.7 ± 6.4%). Among the 16 diploid cases, 18.2 ± 5.7% of the cells were in S-phase. High grade MDS (RAEB-T, RAEB, CMML) was associated with younger age and male sex (p = 0.03), lower percentage of cells in S-phase (p = 0.04), greater bone marrow cellularity (p = 0.005), and greater MIB-1 expression (p = 0.04). With increasing age, there were more females (p = 0.03), more low grade MDS (RA, RARS), and a lower percentage of cells in S-Phase (p = 0.04). Female patients tended to be older, have less cellular bone marrows (p = 0.003), less MIB-1 expression (p = 0.03), low grade MDS (p = 0.02), and increased percentage of cells in S phase (p = 0.008).

CONCLUSION

Ki-67 expression, percent cells in S-phase, clinical parameters and subtype of MDS tend to distinguish two separate groups of MDS patients, and may explain in part the difference in biologic behaviour between high and low grade MDS.

Assessment of cell proliferation in normal and pathological bone marrow biopsies: a study using double sequential immunophenotyping on paraffin sections

The proliferative activity of the haematopoietic and plasma cells in bone marrow was evaluated under normal and neoplastic conditions, by means of a sequential double immunostaining technique, using monoclonal antibody MIB-1 recognizing the cell proliferation-associated nuclear antigen Ki-67, and antibodies against glycophorin-C, myeloperoxidase, factor VIII-related antigen, and immunoglobulin light chains. Fifty-eight B5 fixed, paraffin-embedded bone marrow biopsies were analysed, including 11 normal controls. 10 cases of myelodysplasia, 14 cases of chronic myeloproliferative disorder, eight cases of acute non-lymphoid leukaemia, and 15 cases of myeloma. In normal marrows, the highest proliferative activity was noticed in the erythroid cells (75% to 95%; mean 90%), in comparison with myeloid precursors (15% to 80%; mean 38%), and megakaryocytes (10% to 20%; mean 14%): no Ki-67 positive plasma cells were found. In all investigated haematological disorders, the expression of MIB-1 by erythroid cells was similar to that observed in controls. Similarly, the percentage of MIB-1 + myeloid precursors in chronic myeloproliferative disorders and myelodysplasia largely overlapped the values observed in normals, and comparable values were also found in the blast cells from acute non-lymphoid leukaemia type M1 and M2. These findings suggest that the evaluation of either erythroid or myeloid proliferative activity is of little value in the differential diagnosis between these myeloproliferative disorders. By contrast, the obvious increase of Ki-67 expression of megakaryocytes in chronic myeloproliferative disorders, with labelling also of micro-megakaryocytes, might sustain the diagnosis in controversial cases. Since cases of mature myeloma showed less than 2% of Ki-67 positive cells, evaluation of proliferative activity is of no value in the differential diagnosis with reactive plasmacytosis. The sequential double immunophenotyping for Ki-67 antigen and for haematopoietic cell lineage-associated markers can be applied in a consistent manner to routine bone marrow biopsies to evaluate proliferating cells in normal and neoplastic conditions.

Ki-S1 and PCNA expression in erythroid precursors and megakaryocytes--a comparative study on proliferative and endoreduplicative activity in reactive and neoplastic bone marrow lesions

The monoclonal antibody Ki-S1 reacts with a cell proliferation-associated nuclear antigen which is expressed in the G1 through G2/M phases of the cell cycle and is resistant to formalin fixation. We have studied Ki-S1 and PCNA (PC10) immunostaining of erythroid precursors (proliferative activity) and megakaryocytes (endoreduplicative activity) in bone marrow trephine biopsies in a variety of reactive and neoplastic lesions using double immunohistochemistry to identify both cell lineages. A significant increase in Ki-S1 labelling compared with PCNA positivity was found in all conditions studied. In particular, specimens derived from secondary polycythaemia (SP), polycythaemia vera (P. vera), and primary osteomyelofibrosis (OMF), and from splenic tissue with myeloid metaplasia (MM), revealed a disproportionally high labelling index of erythropoiesis, which was not present in chronic myelogenous leukaemia (CML), AIDS, and autoimmune (idiopathic) thrombocytopenia (ITP). Enhancement of Ki-S1 (PCNA) staining in SP and P. vera is in keeping with the relevant increase in erythroid precursor proliferation, but in OMF and MM there is overexpression of both proliferation markers, possibly due to secondary folic acid deficiency, which is known to cause a block in the S-phase of the cell cycle. A significant correlation was observed between the sizes of megakaryocytes and their nuclei with Ki-S1 (and also PCNA) staining. Ki-S1 (and PCNA) labelling of predominantly smaller elements of this lineage supports a hypothesis that the phases of the cell cycle have different durations in the various steps of polyploidization, with a prolongation of G1/G2 at higher ploidy levels.(ABSTRACT TRUNCATED AT 250 WORDS)