Hematopoietic stem cells (third of three parts)

Role of the RAB7 Protein in Tumor Progression and Cisplatin Chemoresistance

RAB7 is a small guanosine triphosphatase (GTPase) extensively studied as regulator of vesicular trafficking. Indeed, its role is fundamental in several steps of the late endocytic pathway, including endosome maturation, transport from early endosomes to late endosomes and lysosomes, clustering and fusion of late endosomes and lysosomes in the perinuclear region and lysosomal biogenesis. Besides endocytosis, RAB7 is important for a number of other cellular processes among which, autophagy, apoptosis, signaling, and cell migration. Given the importance of RAB7 in these cellular processes, the interest to study the role of RAB7 in cancer progression is widely grown. Here, we describe the current understanding of oncogenic and oncosuppressor functions of RAB7 analyzing cellular context and other environmental factors in which it elicits pro and/or antitumorigenic effects. We also discuss the role of RAB7 in cisplatin resistance associated with its ability to regulate the late endosomal pathway, lysosomal biogenesis and extracellular vesicle secretion. Finally, we examined the potential cancer therapeutic strategies targeting the different molecular events in which RAB7 is involved.

Disruption of Endolysosomal RAB5/7 Efficiently Eliminates Colorectal Cancer Stem Cells

Given that cancer stem cells (CSC) play a key role in drug resistance and relapse, targeting CSCs remains promising in cancer therapy. Here we show that RAB5/7, which are involved in the endolysosomal pathway, play key roles in the maintenance of CSC survival via regulation of the mitophagic pathway. Inhibition of RAB5/7 efficiently eliminated colorectal CSCs and disrupted cancer foci. In addition, we identified mefloquine hydrochloride, an antimalarial drug, as a novel RAB5/7 inhibitor and promising colorectal CSC-targeting drug. Endolysosomal RAB5/7 and LAMP1/2 mediated parkin-dependent mitochondrial clearance and modulated mitophagy through lysosomal dynamics. In a patient-derived xenograft (PDX) model of colon cancer, treatment with mefloquine resulted in suppression of mitophagic PINK1/PARKIN and increased mitochondrial disorder and mitochondria-induced apoptosis without apparent side effects. These results suggest that the combination of mefloquine with chemotherapeutic agents in the PDX model potentially disrupts the hierarchy of colorectal cancer cells and identify endolysosomal RAB5/7 and LAMP1/2 as promising therapeutic targets in CSCs. SIGNIFICANCE: These findings show that endosomal/lysosomal RAB5 and RAB7, which regulate mitophagy, are essential for the survival of colon cancer stem cells.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/7/1426/F1.large.jpg.

A New Stem Cell Biology: Transplantation and Baseline, Cell Cycle and Exosomes

Hematopoietic stem cell biology has focused on stem cell purification and the definition of the regulation of purified stem cells in a hierarchical system. Work on the whole unpurified murine marrow cell population has indicated that a significant number of hematopoietic stem cells, rather than being dormant, are actively cycling, always changing phenotype and therefore resistant to purification efforts by current approaches. The bulk of cycling marrow stem cells are discarded with the standard lineage negative, stem cell marker positive separations. Therefore, the purified stem cells do not appear to be representative of the total hematopoietic stem cell population. In addition, baseline hematopoiesis does not appear to be determined by the transplantable stem cells but rather by many short-lived clones of varying differentiation potential. These systems appear to be impacted by tissue derived extracellular vesicles and a number of other variables. Thus hematopoietic stem cell biology is now at a fascinating new beginning with great promise.

Hematopoietic Stem Cells: Uncomfortable Considerations

Purpose

This report defines new concepts of hematopoietic stem cell biology.

Recent findings

We have utilized 3 different approaches which show that long-term repopulating hematopoietic stem cells are actively cycling and always changing phenotype. In addition this is reversible. This indicates that the stem cell cannot be purified by current epitope selection approaches. The vast bulk of hematopoietic stem cells are discarded in different populations when stem cells are purified to lineage negative c-kit positive and Sca-1 positive cells. Studies to define the hematopoietic niche have been largely carried out on these irrelevant purified cells and thus are not definitive. Studies have indicated the presence of baseline stem cells which function during the normal lifetime of mice. Baseline hematopoiesis appears to be run by thousands of relatively short lived clones with limited differentiation capacity. Thus there appear to be two basic hematopoietic stem cell modes; emergency and baseline.

Review : Neural Stem-Like Cells: Developmental Lessons with Therapeutic Potential

It is possible, by a variety of means, to isolate, propagate, and characterize engraftable clones of cells from the mammalian CNS that fulfill the operational definition of a "stem cell": self-maintaining, self-renewing, and extremely multipotent in vitro and in vivo. Even as debates flourish over how neural stem cells might best be defined, identified, represented, and manipulated, clonal cells with "stem-like" features have begun to provide valuable models for studying commitment, differentiation, and plasticity in the CNS. Furthermore, by learning in this way the basic biology of neural stem cells, and by then exploiting those inherent properties for therapeutic ends, novel and multifaceted strategies seem poised to emerge for redressing a variety of heretofore untreatable CNS dysfunctions. Stem-like cells have begun to show promise for neural cell re placement and molecular support therapy in various animal models of degenerative, developmental, and acquired CNS insult. NEUROSCIENTIST 4:408-425, 1998

Gene expression fluctuations in murine hematopoietic stem cells with cell cycle progression

Evolving data suggest that marrow hematopoietic stem cells show reversible changes in homing, engraftment, and differentiation phenotype with cell cycle progression. Furthermore, marrow stem cells are a cycling population. Traditional concepts hold that the system is hierarchical, but the information on the lability of phenotype with cycle progression suggests a model in which stem cells are on a reversible continuum. Here we have investigated mRNA expression in murine lineage negative stem cell antigen-1 positive stem cells of a variety of cell surface epitopes and transcription regulators associated with stem cell identity or regulation. At isolation these stem cells expressed almost all cell surface markers, and transcription factors studied, including receptors for G-CSF, GM-CSF, and IL-7. When these stem cells were induced to transit cell cycle in vitro by exposure to interleukin-3 (IL-3), Il-6, IL-11, and steel factor some (CD34, CD45R c-kit, Gata-1, Gata-2, Ikaros, and Fog) showed stable expression over time, despite previously documented alterations in phenotype, while others showed variation of expression between and within experiments. These latter included Sca-1, Mac-1, c-fms, and c-mpl. Tal-1, endoglin, and CD4. These studies indicate that defined marrow stem cells express a wide variety of genes at isolation and with cytokine induced cell cycle transit show marked and reversible phenotype lability. Altogether, the phenotypic plasticity of gene expression for murine stem cells indicates a continuum model of stem cell regulation and extends the model to reversible expression with cell cycle transit of mRNA for cytokine receptors and stem cell markers.

Marrow stem cell potential within a continuum

On the basis of our studies of the fluctuation of the hematopoietic stem cell phenotype with cell cycle trnsit, we hypothesize that the ability of marrow stem cells to convert to nonhematopoietic cells will also vary at different points in the cell cycle. The new biology of stem cells has an impact on many fields including developmental biology and stem cell biology and the clinical potential is enormous.

A method for clonal analysis of epidermal growth factor-responsive neural progenitors

Epidermal growth factor (EGF) responsive neural progenitors are defined by clonal growth from single cells. In previous studies we were unable to obtain clones at single cell densities using trypsinized cells and trituration alone always gave cellular aggregates. Here we report on single cell derived clones using a technique involving trituration of EGF responsive neurospheres, cell filtration, and single cell sorting using a MoFlo high speed fluorescence activated cell sorter. Single cell deposition was confirmed by labeling cells with Hoechst 33342 and Flow-check Fluorospheres, and visualization by fluorescence microscopy. The cells were deposited into liquid medium and grown from single cells in 10-20 ng/ml EGF for 12-14 days. This gave a cloning efficiency of 2.12%+/-0.37. New colonies occurred as late as day 18 post-sort. Tritiated thymidine suicide indicates that a percentage of these cells are cycling. Immunohistochemical analysis for oligodendrocytes, astroglia, and neuronal lineages performed on colonies at 10-14 and 21-28 days gave 39% uni-lineage, 36% bi-lineage, and 25% tri-lineage colonies. A total of five different types of progenitor cells were observed. In individual colonies, oligodendrons predominated with a lesser presence of astroglial or neuronal cell types. This approach establishes a reliable and reproducible method for single cell cloning of neurosphere cells.

Evidence for the disruption of the bone marrow microenvironment by combined exposures to inhaled benzene and ingested ethanol

Studies have been performed to investigate the effects of combined in vivo exposures to inhaled benzene and ingested ethanol on the earliest known murine erythropoietic precursor cells, the Burst Forming Unit--Erythroid (BFU-E) and the Colony Forming Unit--Erythroid (CFU-E). Previously we had determined that murine erythropoietic cell populations were particularly susceptible to combined benzene + ethanol treatments. The most striking example of erythropoietic disruption was the transient appearance of large numbers of nucleated red cells (normoblasts) in the circulating blood. In the present studies, male C57Bl/6 mice were exposed to 300 ppm benzene via inhalation for 6 h/d x 5 d/wk x 9 wks. Groups of mice were also exposed to 5% ethanol in the drinking water 4 d/wk x 9 wks. Appropriate controls were also maintained. The hematological assays were performed after 1, 4, and 9 weeks of exposure. After 4 weeks of exposure large numbers of normoblasts appeared in the circulating blood of mice exposed to benzene + ethanol. However, there were no corresponding increases in the numbers of the earliest erythroid progenitor cells in the bone marrow. There were, however, marked increases in the numbers of these cells in the spleen. Previous work in this laboratory had confirmed that the marrow was the source of circulating normoblasts among animals exposed to benzene + ethanol. We conclude, therefore, that circulating normoblasts appear in the peripheral blood because of changes in the bone marrow microenvironment rather than as a consequence of increased erythropoietic proliferation in the marrow.

Purine metabolism as a target for leukemia chemotherapy

This article focuses on the chemotherapeutic agents which alter purine metabolism as a means to achieve selective killing of leukemic cells. We present an overview of purine metabolism in order to highlight enzymatic steps which are targeted by antileukemic drugs. Purine antimetabolites used in the treatment of leukemia can be grouped into three classes: (1) structural analogs of normal purines (6-mercaptopurine and 6-thioguanine); (2) inhibitors of de novo purine biosynthesis (methotrexate and hydroxyurea); and (3) inhibitors of purine salvage (2'-deoxycoformycin). In addition, a number of investigational drugs (trimetrexate, fludarabine and 2'-chlorodeoxyadenosine) have been recently introduced and show promise in early clinical trials. Purine antimetabolites are active in a variety of lymphoid and myeloid leukemias and represent an important component of the therapy of these disorders. Several of the drugs have been developed with the specific intent of perturbing enzymes involved in purine metabolism. Refinements in our understanding of purine biochemistry in normal and leukemic cells may aid future efforts to design more effective drugs.

Macrophages: current views on their differentiation, structure, and function

Macrophages are large mononuclear phagocytes that represent the major differentiated elements of the mononuclear phagocytic system. They arise from distinct progenitors in the bone marrow, and their immediate precursors, the monocytes, emigrate from the vascular compartment into many tissues and organs where they develop into mature macrophages. The latter display diverse morphological and functional characteristics, depending on the environmental stimuli that they receive. This phenotypic heterogeneity is, therefore, the final consequence of a series of down-regulation of some cellular processes and the up-regulation of others. The kinetics of the production of macrophages and their participation in various physiological and pathological phenomena is the subject of this review.

In situ immunocytochemical staining method for haemopoietic cells grown in vitro

Characterization and enumeration of haemopoietic cells grown in vitro is routinely performed either on unstained cultures or on cultures stained by cytochemical agents. This report describes a novel method for the immunocytochemical analysis of cells grown in plasma clots. The stain is performed in situ by subjecting the whole plasma clot in the culture dish to the staining procedure. The growth of early haemopoietic progenitor cells was monitored in cultures from normal human peripheral blood and proliferating progenitor cells were identified with an anti-human transferrin receptor monoclonal antibody followed by a two-layer immunoperoxidase stain. The number of transferrin receptor positive clusters demonstrable after 5 days of culture was similar to the number of haemopoietic colonies detectable after 12 days of culture.

Modulation of responsiveness of chronic myelogenous leukemia granulocyte-macrophage colony-forming cells to growth regulation following in vivo treatment with recombinant gamma-interferon

A patient with Philadelphia chromosome (Ph) chronic myelogenous leukemia (CML), in chronic phase, was treated with recombinant gamma-interferon (r gamma-IFN) in a phase I clinical trial. Prior to treatment, analysis of in vitro agar culture parameters indicated hyporesponsiveness of granulocyte-macrophage colony-forming cells (CFU-GM) to inhibition by prostaglandin E and acidic isoferritins and diminished expression of class II major histocompatibility complex (MHC) antigens (HLA-DR). Treatment was associated with no change in bone marrow cellularity or in the percentage of Ph cells. However, in vitro cultures of bone marrow cells showed a return to normal levels of both expression of CFU-GM class II antigen and of sensitivity to inhibition by prostaglandin E and acidic isoferritins which predicted and/or confirmed clinical response. Throughout the course of interferon therapy, white blood cell counts (WBC) and the percentage of bone marrow blast cells were maintained at normal levels. Onset of aggressive-phase disease was associated with increased WBC, an increase in bone marrow blast cells, a secondary chromosomal abnormality, loss of CFU-GM sensitivity to inhibition by putative negative growth regulators, and markedly diminished MHC class II antigen expression. Following a bone marrow transplant from a matched sibling, all hematologic parameters studied were found to be normal. These findings indicate that treatment with r gamma-IFN can modulate some of the abnormal growth characteristics of CFU-GM observed in CML.

Bone marrow findings in acquired immunodeficiency syndrome (AIDS)

Bone marrow aspirates and biopsies from 35 AIDS/AIDS-related complex patients, consisting primarily of intravenous drug abusers, were studied. The most common findings included hypercellularity (86%), plasmacytosis (63%), reticular fibrosis (50%), and lymphocytosis (37%) occasionally admixed with histiocytes. Granulocytic hyperplasia was present in 27 patients (77%). Erythrocytic hypoplasia was observed in 15 patients (43%). Megaloblastic changes of intermediate form were seen in two cases and serous fat atrophy was noted in another three patients. One M. tuberculosis granuloma, a foreign body granuloma and two granulomas of undetermined etiology were seen, each in separate patients. A previously unreported focal vascular proliferation was seen in one case. The majority of cases showed increased stainable iron. Some of our findings are at variance with previous reports. This may reflect differences in patient population, geographic distribution, risk factors and epidemiologic mode in our cases.

Haemopoietic stem cell: a new concept

It is generally accepted that morphologically recognizable bone marrow (BM) cells are derived from progenitor cells committed to a specific line of haematopoietic differentiation [51]. The origin and morphological identity of such progenitor cells is not yet known and the question, whether there is a single pluripotent haematopoietic stem cell (HSC) or a variety of stem cells each with a capacity of self-replication and maintenance is still unresolved [37]. Although progress has been made in segregating [43, 47, 49, 64] various progenitor cells from one another and functional assays [11, 17, 42] have significantly promoted the study of haemopoietic precursor cells, morphological investigations were less rewarding. Even after enrichment, the morphology of haemopoietic stem- and colony-forming cells only remained hypothetical, 'candidate stem cells' [3], because their precursor cell qualities could not be deduced from their morphology, but only retrospectively, and statistically from their function, i.e. in vitro colony-formation or in-vivo haemopoietic reconstitution from an enriched cell suspension [58]. We postulate from our studies on semi-thin sections of undecalcified BM from healthy human fetuses, normal adults and patients with acute myeloid leukaemia (AML) and chronic granulocytic leukaemia (CGL) that the endosteal cells are the precursors of all haematopoietic cells in the bone marrow and are also capable of transformation into either stromal (fibroblast-like cells) or bone-related cells (osteoblasts and osteoclasts).

Three steps mutation model of carcinogenesis

Based on recent data, this model supposes that benign and malignant tumors arise when a specific mutation takes place in a specific protein-kinase encoded by a proto-oncogene in a pluripotent stem cell or a committed stem cell. Protein-kinases which are regulated by tissue growth stimulating factors, tissue growth inhibiting factors and differentiating factors phosphorylate specific proteins that can derepress specific genes leading to cell division and cell differentiation. Malignant tumors arise when three mutations happen in a same pluripotent stem cell or committed stem cell: positive mutation at the level of tissue growth stimulating factor; negative mutation at the level of tissue growth inhibiting factor; negative mutation at the level of tissue differentiating factor. Higher expression of oncogenes and amplification reflect the relationship between tumor and host. Chromosomal rearrangements are secondary events that can be important because they may involve genes which are normally not involved in cell division and cell differentiation.

Bone marrow alterations induced in mice with inhalation of chrysotile asbestos

The effect of chrysotile asbestos exposure on bone marrow and immune parameters was examined in mice at 2, 12, and 26 weeks following a 3-day inhalation exposure. Ultrastructural examination revealed that the fibers were deposited primarily at alveolar duct bifurcations within the centriacinar region of the lung. Histological pulmonary changes were minimal, but by 26 weeks early asbestosis characterized by clusters of macrophages and minimal fibrosis were present in the centriacinar region of the lung. Lymphoproliferative responses, antibody levels, and number of plaque forming cells were not significantly altered in exposed mice. Pulmonary macrophages, but not peritoneal macrophages, showed evidence of activation in the chrysotile-exposed mice at 26 weeks following exposure. The most striking change was the depression of the number of bone marrow pluripotent stem cells (CFU-S) and marrow granulocyte macrophage progenitors (CFU-GM) which were lower at all three postexposure examinations. It is felt that the depression of bone marrow progenitors in asbestos-exposed mice may have relevance to the leukopenia reported in workers with occupational history of asbestos exposure.

T-lymphocytes escape membrane defect in paroxysmal nocturnal haemoglobinuria

Erythrocytes, granulocytes and platelets from patients with paroxysmal nocturnal haemoglobinuria (PNH) are abnormally sensitive to lysis by complement. We studied T-lymphocytes from PNH patients for abnormal complement lysis sensitivity. T-lymphocytes free of other contaminating blood cells were prepared by sedimentation, nylon wool filtration, and density gradient centrifugation. The lymphocytes were then labelled with 51Cr and lysis induced by antithymocyte globulin and rabbit complement. PNH lymphocytes were no more susceptible to complement-mediated lysis than lymphocytes from normal individuals. The unusual sensitivity of PNH erythrocytes could still be demonstrated when rabbit serum was a source of complement so the lack of any difference in the sensitivity of normal and PNH lymphocytes was probably not attributable to the inability of rabbit serum to elicit the membrane defect. PNH erythrocytes and granulocytes also acquire more membrane-bound C3 when human complement is activated. Therefore we also searched for increased membrane C3 binding on PNH lymphocytes using anti-I antibody and human serum as a complement source. C3 binding was measured using 125I labelled monoclonal mouse anti-human C3. While we verified increased membrane C3 binding on PNH granulocytes during complement activation we were unable to show similar differences between PNH and normal T-lymphocytes. Thus PNH T-lymphocytes do not share the membrane abnormalities of PNH-erythrocytes and granulocytes.

Polymorphonuclear leukocytes: dedicated professional phagocytes

Polymorphonuclear leukocytes are termed professional phagocytes because they are specially equipped to seek and destroy invading microorganisms. Polymorphonuclear leukocytes are formed in the bone marrow and released into the circulation, where they are transported to the tissues. At sites of tissue invasion by microorganisms, humoral factors are released that induce these cells to leave the bloodstream and enter the tissues. Chemotactic substances guide polymorphonuclear leukocytes to the infecting organisms. Antibody and complement can function as opsonins and enhance the ability of polymorphonuclear leukocytes to engulf microbes. Ingested organisms are killed by oxidative or nonoxidative systems. Defects in the various aspects of polymorphonuclear leukocyte function may be found in patients with recurrent, severe, or unusual infections. Evaluation of selected patients with recurrent infections should include tests of polymorphonuclear leukocyte function.

Evidence that the uptake of tri-iodo-L-thyronine by human erythrocytes is carrier-mediated but not energy-dependent

We investigated 3,3',5-tri-iodo-l-thyronine transport by human erythrocytes and by ;ghosts' prepared from these cells. Uptake of tri-iodothyronine by erythrocytes at 37 degrees C was time-dependent with a maximum reached after 60min. Tracer analysis after incubation for 1min revealed only one saturable binding site, with K(m) 128+/-19nm (mean+/-s.e.m.; n=7) and V(max.) 4.6+/-0.7pmol of tri-iodothyronine/min per 6x10(7) cells. After 10min incubation K(m) 100+/-16nm (n=10) was found with V(max.) 7.7+/-1.2pmol of tri-iodothyronine/10min per 6x10(7) cells. At 0 degrees C the uptake system is still active, with K(m) 132+/-26nm and V(max.) 1.8+/-0.3pmol of tri-iodothyronine/10min per 6x10(7) cells. The V(max.) with intact cells is 5-fold greater than the V(max.) with membranes derived from the same amount of cells when uptake studies are performed in media with similar free tri-iodothyronine concentrations. This indicates that at least 80% of tri-iodothyronine taken up by the intact erythrocytes enters the cell. This saturable uptake system can be inhibited by X-ray-contrast agents in a dose-dependent fashion. (+/-)-Propranolol, but not atenolol, has the same effect, indicating that the membrane-stabilizing properties of (+/-)-propranolol are involved. Furthermore, there is no inhibition by ouabain or vanadate, which indicates that tri-iodothyronine uptake is not dependent on the activity of Na(+)+K(+)-dependent adenosine triphosphatase. We have prepared erythrocyte ;ghosts', resealed after 2.5min with 0mm-, 2mm- or 4mm-ATP inside. Inclusion of ATP and integrity of the membrane of the erythrocyte ;ghosts' were verified on the basis of an ATP-concentration-dependent functioning of the Ca(2+) pump. No difference was found in the uptake of tri-iodothyronine by erythrocyte ;ghosts' with or without ATP included, indicating that uptake of tri-iodothyronine is not ATP-dependent. The following conclusions are drawn. (1) Tri-iodothyronine enters human erythrocytes. (2) There is only one saturable uptake system present for tri-iodothyronine, which is neither energy (i.e. ATP)-dependent nor influenced by the absence of an Na(+) gradient across the plasma membrane. This mode of uptake of tri-iodothyronine by human erythrocytes is in sharp contrast with that of rat hepatocytes, which uptake system is energy-dependent and ouabain-sensitive [Krenning, Docter, Bernard, Visser & Hennemann (1978) FEBS Lett.91, 113-116; Krenning, Docter, Bernard, Visser & Hennemann (1980) FEBS Lett.119, 279-282]. (3) X-ray-contrast agents inhibit tri-iodothyronine uptake by erythrocytes in a similar fashion to that by which they inhibit the uptake of tri-iodothyronine by rat hepatocytes [Krenning, Docter, Bernard, Visser & Hennemann (1982) FEBS Lett.140, 229-233].

Myeloproliferative Disease with Megakaryocytic Predominance in a Dog with Occult Dirofilariasis

A 7-year-old male German Shepherd dog with a history of lethargy, weight loss and severe anemia was referred to the University of Florida Veterinary Medical Teaching Hospital for examination. Abnormal laboratory findings included a normocytic and normochromic anemia, thrombocytosis, eosinophilia, basophilia and hyperproteinemia. An increased pulmonary density in the caudal lung lobes was observed on thoracic radiographs. Bone marrow aspiration and core biopsy revealed a hypercellular bone marrow with increased numbers of unidentified blast cells and bizarre megakaryocyte proliferation. Circulating microfilariae were not present in the blood, but serum examined by immunofluorescence was strongly positive for antibodies against Dirofilaria immitis microfilariae. A diagnosis of myeloproliferative disease with megakaryocytic predominance and occult dirofilariasis was made.

Pathogenetic significance of "pure" monosomy 7 in myeloproliferative disorders. Analysis of 14 cases

Monosomy 7 is frequent in acute myeloid leukaemia (AML) and in preleukaemic dysmyelopoietic syndromes but often it is not the only chromosome anomaly associated with these conditions. We report 14 patients with "pure" monosomy 7 and their clinical and haematological data are analysed in order to clarify the possible implications of this chromosome anomaly. The following points are considered: 1) In spite of the apparent variability of clinical forms in which monosomy 7 is found, several characteristics are common to all monosomy 7 patients, i.e. the presence of a preleukaemic phase and blood and marrow features suggesting the early involvement in the disease of all marrow cell lines. The different diagnoses associated with monosomy 7 are correlated with different steps of a unique myeloproliferative disease whose typical course can be reconstructed. 2) Monosomy 7 has a negative prognostic value. When it is found in a preleukaemic disorder it indicates a high risk of progression to AML, while in AML it implies recurrent infections, poor response to therapy and short survival. 3) The significance of the lack of Colton blood group antigens in monosomy 7 patients is discussed, with particular regard to the fact that the patients in whom this lack was found are the only ones who had not received transfusions in the months before the tests were done. 4) The finding of defective neutrophil chemotaxis in monosomy 7 patients is confirmed and the clinical importance of this fact is emphasized. 5) The data on the 14 patients support the opinion that AML, in general, is heterogeneous in origin. It is postulated that monosomy 7 is a marker of a specific pathogenetic pathway of AML, which implies the beginning of the malignancy in a pluripotent stem cell.

Juvenile and adult types of chronic granulocytic leukemia of childhood: growth patterns and characteristics of granulocyte-macrophage colony forming cells

Peripheral blood and bone marrow cells from three children with the juvenile (Ph1 negative) type of chronic granulocytic leukemia and from one with the adult (Ph1 positive) type were cultured in soft agar, and their specific growth patterns were evaluated. Greatly increased numbers of colonies were obtained in all cases, particularly from peripheral blood cells. By morphologic, cytochemical and ultrastructural criteria, colonies from one juvenile type and from the single adult type patients were found to be almost exclusively granulocytic, whereas in the other two juvenile type leukemia patients colonies were either granulocytic or macrophage. Moreover, both growth patterns were obtained in the same patients on different occasions. It appears that the leukemic cell populations of the juvenile and the adult forms of chronic granulocytic leukemia do not arise from different cell lines. Rather, both are the progeny of the common monocyte-granulocyte progenitor cell, whose abnormal proliferation and differentiation along either the granulocytic or the monocytic pathway is probably directed by fluctuations in humoral and/or microenvironmental factors.

Nucleolar immunofluorescence in bone marrow specimens of human hematological malignancies

Leukemic cells and myeloma cells were studied in bone marrow of untreated patients with acute and chronic myeloid leukemia, chronic lymphocytic leukemia, and multiple myeloma to provide more information on the nucleolar immunofluorescence produced by antibodies no nucleoli of HeLa cells. The nucleolar immunofluorescence was mainly observed in myeloblasts of myeloid leukemias an in immature as well as mature cells of the plasmacytic or lymphocytic cell lines of multiple myeloma or chronic lymphocytic leukemia. With respect to the nucleolar immunofluorescence, both positive and negative populations of cells were noted in the specimens of all patients studied.

Monoclonal antibody assessments of T cell interactions in erythropoietin studies

The contemporary application of clonal assay techniques has greatly expanded our knowledge of the regulation of hematopoiesis. Our efforts have been directed toward the investigation of non-erythropoietin-mediated regulation of human erythropoiesis in the form of cell-to-cell interaction between mature T cells and erythroid progenitors. Our data indicate that three such progenitors, the early marrow erythrocyte precursor BFU-E, the more mature marrow erythrocyte precursor, CFU-E and the peripheral blood BFU-E, each exhibit totally different requirements for their colony expression in culture, with respect to the absence of erythropoietin and the presence of mature T cells or their products. The capacity of erythroid progenitors to withstand incubation in the absence of erythropoietin appears to be a characteristic of immature rather than mature erythroid progenitors. Furthermore, use of OKT3 antibody depletion techniques shows that peripheral blood-derived BFU-E appear to depend upon mature lymphocytes or T cell-conditioned medium for erythropoietin-stimulated differentiation while bone marrow BFU-E and CFU-E have no requirement for mature T cells to produce erythropoietin-dependent maturation. Our results, plus a vast array of data provided by other investigators in the field, are integrated into a proposed framework for further investigation of T cell induction of erythropoietin-dependent erythroid differentiation aimed at more specifically identifying the inducer cell subset(s) in that system.

[Humoral factors in the regulation of cell proliferation in haematopoiesis. I. Granulopoiesis and lymphopoiesis (author's transl)]

Humoral Factors obviously play an important role in the maintenance of the steady state in haematopoiesis. There has been work on stimulators and inhibitors for several years. Colony-stimulating factor is the best characterized chemically and biologically. Interest in more or less cell-line-specific stimulators and inhibitors of lymphopoiesis is now growing. Various tissue extracts and cell culture supernatants have been partially purified and characterized biologically and chemically. Monocytes, producing stimulators and inhibitors, have a central function in the regulation of cell proliferation in haematopoiesis. Experiments performed in vitro can help better to understand data so far difficult to explain regarding patients with disturbed haematopoiesis. The in vivo relevance of these experiments, however, remains unclear.