Sequential acquisition of IgH and TCR rearrangements during the preleukemic phase of acute lymphoblastic leukemia in an adolescent patient.

Acute lymphoblastic leukemia (ALL) can be preceded by a prodromal phase of bone marrow failure. In serial trephine biopsies in a girl with acquired bone marrow hypoplasia, we have identified a monoclonal B-cell precursor population characterized by a clone-specific IgH-FR3 gene rearrangement. Progression to ALL more than 4 months later was accompanied by acquisition of an additional T-cell receptor rearrangement. Thus, hypoplastic pre- and overt leukemia share a common clonal origin. Prospective biobanking and extended molecular analysis can help to better understand the nature and sequence of genetic events during progression of a covert (pre)leukemic clone.

Defining the oncogenic function of the TEL/AML1 (ETV6/RUNX1) fusion protein in a mouse model.

The t(12;21) translocation, generating the TEL/AML1 fusion protein, is the most common genetic lesion in childhood cancer. Using a bone marrow transplantation model, we demonstrate that TEL/AML1 expression impinges on normal hematopoietic differentiation, leading to the in vivo accumulation and persistence of an early progenitor compartment with a Sca1(+)/Kit(hi)/CD11b(+) phenotype and an increased self-renewal capacity, as documented by replating assays in vitro. Differentiation of these cells is not blocked, but the frequency of mature blood cells arising from TEL/AML1-transduced progenitors is low. Impaired differentiation is prominently observed in the pro-B-cell compartment, resulting in an proportional increase in early progenitors in vivo, consistent with the t(12;21) ALL phenotype. Despite the accumulation of both multipotent and B-cell progenitors in vivo, no leukemia induction was observed during an observation period of over 1 year. These results are consistent with findings in twins with concordant ALL, showing that TEL/AML1 generates a preleukemic clone in utero that persists for several years in a clinically covert fashion. Furthermore, our studies showed that the pointed domain of TEL/AML1, which recruits transcriptional repressors and directs oligomerization with either TEL/AML1 or wild-type TEL, was essential for the observed differentiation impairment and could not be replaced with another oligomerization domain.

Effects of marrow grafting on preleukemia cells and thymic nurse cells in C57BL/Ka mice after a leukemogenic split-dose irradiation.

A split-dose regimen of whole-body irradiation (4 X 175 rad at weekly intervals) induced thymic lymphomas in C57BL/Ka mice after a latent period of 3-9 months. Meanwhile, preleukemia cells arose in the thymus and bone marrow and persisted until the onset of lymphomas. Simultaneously, thymic lymphopoiesis was impaired; thymocyte numbers were subnormal and thymic nurse cells disappeared in a progressive but irreversible fashion. The depletion of these lymphoepithelial complexes, which are normally involved in the early steps of thymic lymphopoiesis, was related to altered prothymocyte activity in bone marrow and to damaged thymic microenvironment, perhaps as a consequence of the presence of preleukemia cells. The grafting of normal bone marrow cells after irradiation prevented the development of lymphomas. However, marrow reconstitution did not inhibit the induction of preleukemia cells. They disappeared from the thymus during the second part of the latent period. At the same time, thymic lymphopoiesis was restored; thymocytes and nurse cell numbers returned to normal as a consequence of the proliferation of grafted marrow-derived cells within the thymus. The results thus demonstrated an intimate relationship between preleukemia cells and an alteration of thymic lymphopoiesis, which particularly involved the nurse cell microenvironment. Some preleukemia cells in marrow-reconstituted, irradiated mice derived from the unirradiated marrow inoculate. Thus these cells acquired neoplastic potential through a factor present in the irradiated tissues. The nature of this indirect mechanism was briefly discussed.

Marrow cytogenetic and cell-culture analyses of the myelodysplastic syndromes: insights to pathophysiology and prognosis.

Marrow cytogenetic and granulocyte-macrophage colony formation (CFU-GM) studies were performed on 34 previously untreated patients with documented myelodysplastic syndromes seen between January 1978 and June 1982. All patients were managed without chemotherapy until progression to acute leukemia was observed. All 10 patients with exclusively abnormal marrow metaphases developed acute leukemia (100%) while only one (7%) of 14 patients with solely normal marrow metaphases subsequently developed leukemia (p less than 0.001). Three (42%) of the seven patients with both normal and abnormal marrow metaphases developed acute leukemia. Fifteen (86%) of the 19 patients with either large cluster or no growth patterns developed acute leukemia while only two (13%) of 15 patients with either small cluster or colony forming growth patterns developed acute leukemia (p less than 0.001). Abnormal marrow cytogenetic status correlated with abnormal marrow CFU-GM growth pattern (p less than 0.05). Analysis of CFU-GM sensitivity to inhibition by prostaglandin E was performed in 12 patients. Nine patients showed CFU-GM refractoriness to inhibition by prostaglandin E. Seven of these patients eventually developed leukemia. Three patients had CFU-GMs which were initially sensitive to prostaglandin E inhibition. In these three patients, a loss of CFU-GM sensitivity to prostaglandin E was observed prior to their progression to morphologically identifiable acute leukemia.

Growth modulation of human leukemic, preleukemic, and myeloma progenitor cells by L-ascorbic acid.

L-Ascorbic acid (LAA) was shown to modulate the in vitro growth of colonies of human and mouse myeloma progenitor-stem cells through use of a unique cell-culture assay. LAA was also shown to modulate the in vitro growth of leukemic colony-forming cells (L-CFC) from bone marrow of patients with acute myelocytic leukemia. LAA enhanced the growth of L-CFC in 35% of patients and suppressed the growth of L-CFC in 15% of patients. The minimum effective concentration was 0.03 mmol/L. The modulating effect is specific to LAA because other redox compounds are without effect. From the cell kinetic standpoint, the LAA effect is cytostatic rather than cytocidal. Similar LAA effects have prognostic value in patients with myelodysplastic syndromes (MDS), with LAA-sensitive patients displaying shorter survival than LAA-insensitive patients. MDS appears to be the ideal disease for clinical trials involving in vivo LAA manipulation to control the disease process.

Acute nonlymphocytic leukemia.

The discovery of cytosine arabinoside, and then the anthrocycline antibiotics, 6-thioguanine, vincristine, cyclophosphamide, and other drugs, has added to the armamentarium of known effective agents. The use of combination chemotherapy, the recognition of the need during induction for virtual marrow aplasia to obtain a remission, and recognition of the predilection of the disease for the central nervous system requiring prophylaxis constitute major advances. The impediment to long-term survival is the lack of effective maintenance therapy.

[Myelodysplastic syndromes: preleukemic syndromes]. / Les syndromes myélodysplasiques: syndromes préleucémiques.

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by peripheral blood cytopenias with a hypercellular bone marrow exhibiting dyspoiesis. The predominant in elderly patients are associated with a high risk of progression to acute myelogenous leukemia. The etiology of MDS is unknown in most cases. About 10% of MDSs are secondary. MDS are classified by the French American British (FAB) classification into five subgroups. The incidence of the disorders is difficult to estimate but it seems to be increasing. Clonal cytogenetic aberrations are found in 30 to 50% of de novo MDS. The only currative treatment for MDS is allogeneic bone marrow transplantation.

Preleukaemia and myelodysplastic syndromes today.

The clinical picture of myelodysplastic syndromes (MDS) results from the expansion of an abnormal clone of haemopoietic stem cells that has undergone premalignant transformation. Different types of "oncogene" may be involved in this process, some of which code for growth factors and their receptors, some for membrane or cytoplasmic proteins and some for nuclear binding proteins. The insults causing gene mutations are not known, though chemical, viral or radiation damage could be important. The most striking feature of MDS is the inadequate production of dysplastic, poorly functional cells as a result of impaired differentiation and premature cell death in the bone marrow. Treatment is currently directed to supportive therapy with blood components and antibiotics, attempts to stimulate proliferation and differentiation with recombinant human growth factors, and, in a few cases, bone marrow transplantation. Chemotherapy alone has met with little success.

[Preleukemic disorders].

Certain hematopoietic disorders and immunodeficiency states are known to carry a risk of developing acute nonlymphocytic leukemia. In the past some of them have been classified by a variety of terms ranging from refractory anemia to preleukemia, but are currently grouped into a new concept of the myelodysplastic syndromes (MDS). The purpose of this article is to briefly review the updated knowledge of the MDS with emphasis on the clonal origin, natural history and mechanisms of leukemogenesis.

Aberrant megakaryocytopoiesis preceding radiation-induced leukemia in the dog.

Six of nine decedent beagles exposed continuously to 2.5 R*/22 hour day of whole-body 60Co gamma-radiation died with myeloproliferative diseases: three cases of myelogenous leukemia and one each of monocytic leukemia, erythroleukemia, and erythremic myelosis. The three dogs that died with myelogenous leukemia had micromegakaryocytes and megakaryoblasts in the peripheral blood during the preleukemic phase when myeloblasts were not observed in the peripheral blood or in increased numbers in the bone marrow. In this study we have examined the megakaryocytes during the preleukemic period by a combination of light, transmission, and scanning electron microscopy. Morphologic abnormalities seen by light microscopy included mononucleated and binucleated forms, many with cytoplasmic blebs. The small mononuclear forms in the bone marrow tended to form clusters. Ultrastructural features included a paucity of both specific alpha granules and dense granules. The micromegakaryocytes showed dysgenesis of the demarcation membrane system. This membrane system appeared disorganized with a few dilated round, oval, or rarely, elongated vesicles and showed no evidence of platelet formation. The cells also had a paucity of endoplasmic reticulum, few mitochrondria, and sparse glycogen accumulations. The scarcity of cytoplasmic organelles gave a pale immature appearance to the cytoplasm. By scanning electron microscopy, the sponge-like surface of large mature megakaryocytes from unirradiated marrow contrasted with the characteristically smooth, topographically featureless surfaces of the micromegakaryocytes from preleukemic dogs.

Role of mononuclear phagocyte system in hemopoiesis regulation in AKR/JY mice during preleukemic period.

Feeder activity of bone marrow adherent cells and peritoneal macrophages is decreased and colony-stimulating and erythropoietic activity of unfractionated bone marrow increased in highly leukemic AKR/JY mice in comparison with CBA/CaLac mice. At the same time maturation of hemopoietic precursor cells in AKR/JY mice is delayed compared to controls. This indicates compensatory activation of nonadherent elements of the hemopoiesis-inducing microenvironment against the background of suppressed activity of adherent elements. Hence, leukemogenic virus produced a systemic damage to target cells (e.g. mononuclear phagocyte system), which probably represent a mechanism of leukemic transformation in AKR/JY mice.