Hypereosinophilic syndrome and cyclic oscillations in blood cell counts. A clonal disorder of hematopoiesis originating in a pluripotent stem cell

We studied a patient with hypereosinophilic syndrome (HES) who had myeloproliferative features, was unresponsive to imatinib mesylate, and showed cyclic oscillations in blood cell counts. No rearrangement in PDGFRA, PDGFRB and ETV6 genes was detected. Clonal analysis of hematopoiesis consistently showed skewed X-chromosome inactivation patterns in both granulocytes and T-lymphocytes, indicating a clonal myeloproliferative disorder originating in a pluripotent stem cell.

Primitive hematopoietic stem cells shows a polyclonal pattern in myelodysplastic syndromes

BACKGROUND AND OBJECTIVES

Clonal hematopoiesis is the hallmark of myelodysplastic syndromes, but the role played by pluripotent stem cells and progenitor cells in these disorders remains unclear.

DESIGN AND METHODS

Eight female patients with myelodysplastic syndrome were studied. X-chromosome inactivation patterns were analyzed in peripheral blood granulocytes, T-lymphocytes, single colonies originating from bone marrow progenitors and pluripotent stem cells, using the human androgen receptor locus polymorphism assay.

RESULTS

Granulocytes and progenitor cells were monoclonal in 7/8 cases. Immature stem cells showed a non-clonal pattern of X-inactivation and were detectable at diagnosis in the presence of clonal hematopoiesis. T-lymphocyte clonality was heterogeneous.

INTERPRETATION AND CONCLUSIONS

In myelodysplastic syndromes, hematopoiesis may be dominated by a neoplastic clone by virtue of its biological advantage over a residual polyclonal, probably still normal, population of immature stem cells still able to grow in vitro.

[Differentiation of pluripotent embryonic stem cells in peritoneal cavity of irradiated mice]

We studied the behavior and differentiation of pluripotent embryonic stem cells of R1 mice in vivo. Undifferentiated embryonic stem cells and differentiating embryoid bodies grafted in abdominal cavity of the irradiated mice were shown to form tumors with derivatives of all germinal layers. Cells of the embryoid bodies form tumors two weeks after the grafting, while the undifferentiated embryonic stem cells form tumors only by week three.

Critical review of pathogenetic mechanisms in myelofibrosis with myeloid metaplasia

Myelofibrosis with myeloid metaplasia is an uncommon chronic myeloproliferative disorder characterized by extramedullary hematopoiesis associated with varying degrees of bone marrow fibrosis (hematopoiesis is clonal and fibrosis is a polyclonal reactive process). The primary defect in a pluripotent stem cell is still unknown. However, advances have been made during the past few years in the knowledge of the pathogenetic mechanisms in this disorder. This review focuses on current data on the cellular and molecular mechanisms possibly participating in the development of the disease.

B lineage acute lymphoblastic leukemia transformation in a child with juvenile myelomonocytic leukemia, type 1 neurofibromatosis and monosomy of chromosome 7. Possible implications in the leukemogenesis

This report describes the case of an 8-month-old infant with a diagnosis of juvenile myelomonocytic leukemia (JMML) and type 1 neurofibromatosis that presented progression to B lineage acute lymphoid leukemia (ALL). The same rearrangement of gene T-cell receptor gamma (TCR gamma) was detected upon diagnosis of JMML and ALL, suggesting that both neoplasias may have evolved from the same clone. Our results support the theory that JMML may derive from pluripotential cells and that the occurrence of monosomy of chromosome 7 within a clone of cells having an aberrant neurofibromatosis type 1 (NF1) gene may be the cause of JMML and acute leukemia.

Mammary stem cell repertoire: new insights in aging epithelial populations

The proliferative lifespan of mammary stem cells was examined in serially transplanted clonal-dominant epithelial populations. Five successive transplant generations were done. The epithelial cell number in each outgrowth expands approximately 500-fold in nulliparous hosts and approximately 10000-fold in impregnated hosts. Despite this, all resulting mammary outgrowths showed lineal identity with the original. Growth senescence was observed in some implants beginning at the third generation in impregnated recipients. The ability of an individual implant to support ductal morphogenesis and also secretory lobule development decayed at independent rates. Individual implants from a single clonal-dominant outgrowth occasionally gave rise to markedly different ductal development within the same host indicating an epithelial cell autonomous mechanism in ductal patterning. Both premalignant and malignant populations appeared focally within the aging transplants. These populations were also lineally related to the original outgrowth supporting the conclusion that the primary growth was derived clonally from one or a few lineally related antecedents. The premalignant and malignant descendant populations no longer exhibit growth senescence suggesting that they are supported by a perpetually self-renewing progenitor. Our evidence indicates that a single mammary cell may have the capacity to self-renew through five transplant generations. Even some sixth generation implants show vigorous growth.

Lineage switch and multilineage involvement in two cases of pH chromosome-positive acute leukemia: evidence for a stem cell disease

Philadelphia chromosome-positive acute leukemias (Ph+ AL) show variable cytologic features, possibly reflecting heterogeneous stem cell involvement. Morphologic, immunologic and cytogenetic studies were performed in two cases of Ph+ acute lymphoblastic leukemia (ALL) in order to better delineate the clinicobiological features of this cytogenetic subset of AL. Sequential cytoimmunologic studies in patient 1 documented a lineage switch from pro-B ALL with a minor myeloid component at diagnosis to minimally differentiated acute myeloid leukemia (AML) at relapse. In this patient the major breakpoint cluster region (M-bcr) was in a rearranged configuration and all metaphase cells showed t(9;22)(q34;q11), both at diagnosis and at relapse. In patient 2 a diagnosis of Ph+ early T-cell ALL with minor myeloid component was made. In this patient the M-bcr was in a germline configuration. Cytogenetic studies documented the presence of the Ph chromosome in all metaphases from a lymphoid cell population obtained by fine-needle aspiration of an enlarged lymph node, and from a bone marrow cell fraction enriched in granulocyte precursors. This finding suggests multilineage involvement in this patient. Lineage switch and multilineage involvement in two patients suggest that a pluripotent stem cell may be affected rather frequently in patients with Ph+ AL. These findings show that biologically Ph+ AL may resemble chronic myelogenous leukemia blast crisis, since it may originate from an undifferentiated stem cell carrying the t(9;22) translocation.