Apoptosis, haemopoiesis and leukaemogenesis

Effect of Cx43 gene-modified leukemic bone marrow stromal cells on the regulation of Jurkat cell line in vitro

We recently reported that Cx43 expression and gap junction intercellular communication (GJIC) between acute leukemic bone marrow stromal cells (BMSCs) were deficient, which could recovery after effective chemotherapy. However, the exact role of GJIC in the hematopoietic microenvironment in leukemic cell death and proliferation is not clear. We show here that following transfection with the Cx43 gene, GJIC function was increased between leukemic BMSCs. Furthermore, compared with leukemic cells alone, the proliferation and apoptosis of leukemic cells co-cultured with BMSCs were inhibited, the percentage of G0-phase cells was higher; and expression of p53 increased and bax decreased. However, after co-culturing leukemic cells with Cx43-modified BMSCs, the number of proliferative and spontaneously apoptotic Jurkat cells increased; the percentage of G0-phase cells decreased; the expression of p53 decreased; and bax increased. Compared with Jurkat cells co-cultured with BMSCs and Jurkat cells alone, the sensitivity of leukemic cells co-cultured with Cx43-modified BMSCs to chemotherapeutics increased. Our data suggests that GJIC between leukemia BMSCs is one of the impact factor to the proliferation, apoptosis and drug sensitivity of co-cultured leukemic cells. Up-regulating its function can inhibit the protective effects of leukemic BMSCS and enhance the efficacy of therapies in hematologic malignancies.

Mapping of treatment-induced apoptosis in normal structures: 99mTc-Hynic-rh-annexin V SPECT and CT image fusion

PURPOSE

The purpose of this study was to map treatment-induced (99m)Tc-Hynic-rh-annexin V uptake in normal tissues using co-registration of SPECT and CT.

METHODS

Nineteen patients (11 male, 8 female, mean age 57 years) with various malignant tumours (12 lymphomas, four non-small cell lung cancers and three head and neck squamous cell carcinomas) underwent (99m)Tc-Hynic-rh-annexin V scintigraphy and CT before and within 48 h after the start of anticancer therapy. SPECT and CT were performed separately, with the patient in a reproducible position. Volume-based automated and manual methods were used to match functional and anatomical data. SPECT/CT co-registration was used to evaluate treatment-induced changes in the normal structures.

RESULTS

A significant radiation field-related increase in early post-treatment (99m)Tc-Hynic-rh-annexin V uptake in salivary glands and bone marrow was detected in eight of nine patients. Radiation field-related increase in bone marrow activity above the baseline value was detected in all 13 irradiated patients. A minimal, symmetrical increase in activity in the salivary glands was detected after the initial course of platinum-based chemotherapy, and a diffuse prominent increase in (99m)Tc-Hynic-rh-annexin V in the bone marrow was detected in all cases. Precise delineation between the tumour and normal tissue tracer accumulation was accomplished in all cases using SPECT/CT co-registered volumes, enhanced by the "colourwash" technique.

CONCLUSION

Mapping of early treatment-related changes in annexin V uptake by SPECT/CT co-registration permits accurate evaluation of tracer distribution in normal structures and precise delineation from tumour uptake. The associations between tracer distribution in the normal tissues and treatment regimen found in this study may contribute to the evaluation of dose-effect relations in various treatment schedules.

Association of reticular cells with CD34+/Sca-1+ apoptotic cells in the hemopoietic organ of grasshopper, Euprepocnemis shirakii

Hemopoiesis in orthopteran insects occurs in a hemopoietic organ that is located bilaterally along the aorta. This organ is also known as a reticulo-hemopoietic organ because of the rich presence of reticular cells. This study was performed to further elucidate hemopoiesis in the reticulo-hemopoietic organ of an orthopteran, Euprepocnemis shirakii. We focused on the question why reticular cells are so abundant (35% of cells in hemopoietic organ). Interestingly, 21% of these reticular cells surrounded hemocytes with their reticular cytoplasm. The surrounded hemocytes were distinguished by their different size and darkly stained nucleus. These cells were characterized by immunostaining using antibodies against several types of hemocytes: 45% of the surrounded hemocytes were CD34+, and these positive cells were double stained (over 85%) when immunostained by another hemopoietic pluripotent cell marker, Sca-1. Transmission electron microscopic analysis showed that reticular cells surrounded hemocytes containing large nuclei and poorly developed cytoplasmic organelles. This strongly suggests that the reticular cells surround hemopoietic stem cells. Additionally, surrounded hemopoietic progenitor cells are undergoing apoptosis as indicated by the TUNEL assay. The enclosed apoptotic cells are engulfed and then phagocytosed by reticular cells. Our results suggest that reticular cells are related to the differentiation and apoptosis of hemopoietic stem cells.

Apoptosis in glioma cells: review and analysis of techniques used for study with focus on the laser scanning cytometer

Traditional approaches to the treatment of brain tumors are based on the hypothesis that tumors arise and grow because of the disordered regulation of cell proliferation. More recently, it has become apparent that tumor growth depends not only on the rate of cell proliferation but also on the rate of apoptosis (programmed cell death). Genomic alterations that occur in malignancy may limit the cell's ability to undergo apoptosis. Many new treatment strategies for gliomas stem from the use of techniques aimed at manipulating apoptosis. Being able to assess the efficacy of experimental treatments with refined techniques and being able to use instruments that can provide accurate measurements of the apoptotic markers will open the door for discovering novel strategies with the potential to induce effective and selective cytotoxicity. We discuss here in detail the major traditional techniques of assessing apoptosis. We provide an overview of cytometric techniques, including flow cytometry (FC), and will compare it with the laser scanning cytometer (LSC). This is a powerful new tool with potential for obtaining a fast and objective analysis of apoptosis through multiple mechanisms, as well as for assessing proliferation and DNA ploidy in solid malignant tumors.

Mammalian mitochondrial IAP binding proteins

Four mitochondrial proteins have been identified that immunoprecipitate with the mammalian inhibitor of apoptosis (IAP) protein XIAP. Each of them interacts via a processed amino terminus that resembles those of the insect pro-apoptotic IAP binding proteins Grim, HID, Reaper, and Sickle. Two, Diablo/Smac and HrtA2/Omi, have been extensively characterized. Both Diablo and HtrA2 can bind to IAPs and promote apoptosis when over-expressed in transfected cells, but unlike the insect IAP antagonists, to date there is scant evidence that they are important regulators of apoptosis in more physiological circumstances.

The role of apoptosis in the regulation of hematopoietic stem cells: Overexpression of Bcl-2 increases both their number and repopulation potential

Hematopoietic stem cells (HSC) give rise to cells of all hematopoietic lineages, many of which are short lived. HSC face developmental choices: self-renewal (remain an HSC with long-term multilineage repopulating potential) or differentiation (become an HSC with short-term multilineage repopulating potential and, eventually, a mature cell). There is a large overcapacity of differentiating hematopoietic cells and apoptosis plays a role in regulating their numbers. It is not clear whether apoptosis plays a direct role in regulating HSC numbers. To address this, we have employed a transgenic mouse model that overexpresses BCL-2 in all hematopoietic cells, including HSC: H2K-BCL-2. Cells from H2K-BCL-2 mice have been shown to be protected against a wide variety of apoptosis-inducing challenges. This block in apoptosis affects their HSC compartment. H2K-BCL-2-transgenic mice have increased numbers of HSC in bone marrow (2.4x wild type), but fewer of these cells are in the S/G(2)/M phases of the cell cycle (0.6x wild type). Their HSC have an increased plating efficiency in vitro, engraft at least as well as wild-type HSC in vivo, and have an advantage following competitive reconstitution with wild-type HSC.

Self-renewal, differentiation or death: regulation and manipulation of hematopoietic stem cell fate

Hematopoietic stem cells (HSCs) are the rare cells from which all hematopoietic cells are derived. The absence of HSCs is not compatible with life because many essential cells, such as myeloid and erythroid cells, are short lived. The hematopoietic system is the first essential organ system that fails following cytotoxic treatments. It is the vulnerability of HSCs that prevents regeneration following treatment and thus long-term survival. Because HSCs have the capacity to regenerate a functional hematopoietic system, the manipulation of these cells in vitro holds many promises for gene-therapeutic and other applications; however, these are severely curtailed by current difficulties in maintaining and expanding HSCs in culture. This review focuses on recent approaches towards understanding how the HSC compartment is regulated in vivo and discusses how this knowledge might be applied to manipulating HSC numbers.

Flt3 ligand can promote survival and macrophage development without proliferation in myeloid progenitor cells

Flt3 ligand elicits a variety of effects on early hemopoietic progenitors by occupying its cognate receptor, Flt3, a member of the type III tyrosine kinase receptor family. The cytokines macrophage colony-stimulating factor (M-CSF) and stem cell factor (SCF) bind to related members of this tyrosine kinase receptors family, c-fms and c-kit, respectively. The relative effects of the cytokines M-CSF, SCF, and Flt3L on the proliferation and development of the late myeloid progenitors granulocyte-macrophage colony-forming cells (GM-CFC) were investigated. Distinct biologic responses were stimulated by ligand binding to these different tyrosine kinase receptors in enriched GM-CFC. M-CSF stimulated GM-CFC to proliferate and develop into macrophages. SCF, on the other hand, stimulated GM-CFC to develop into neutrophils. Flt3 ligand had a relatively small proliferative effect on enriched GM-CFC compared to SCF and M-CSF and had no ability to either stimulate colony formation or synergize with these two cytokines in promoting DNA synthesis, colony formation, or expansion in liquid culture. Flt3 ligand, however, was capable of maintaining the clonogenic potential of GM-CFC and acted as an anti-apoptotic agent as assessed using the Annexin-V apoptosis assay. GM-CFC cultured in Flt3 ligand eventually formed macrophages and neutrophils in liquid culture. Labeling with the membrane-associated cell tracker dye PKH26 indicated that the majority of the enriched GM-CFC responded to Flt3 ligand by undergoing limited proliferation and macrophage development, whereas other cells survived but did not proliferate and differentiate into macrophages. Thus, Flt3 ligand promoted survival and stimulated development without proliferation in primary-enriched myeloid progenitor cells.