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Query: UMLS:C0023467 (acute myeloid leukemia)
 35,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acute myeloid leukaemia (AML) is thought to be maintained by a small population of leukemic progenitor cells. To define the phenotype of such cells with long-term proliferative capacity in vitro and in vivo, we have used the production of leukemic clonogenic cells (CFU) after 2 to 8 weeks in suspension culture as a measure of these cells in vitro and compared their phenotype with that of cells capable of engrafting nonobese diabetic severe combined immune deficient (NOD/SCID) mice. Leukemic blast peripheral blood cells were evaluated for expression of CD34 and Thy-1 (CD90) antigens. The majority of AML blast cells at diagnosis lacked expression of Thy-1. Most primary CFU-blast and the CFU detected at up to 8 weeks from suspension cultures were CD34+/Thy-1-. AML cells that were capable of engrafting NOD/SCID mice were also found to have the CD34+/Thy-1- phenotype. However, significant engraftment was achieved using both CD34+/Thy-1- and CD34- subfractions from one AML M5 patient. These results suggest that while heterogeneity exists between individual patients, the leukemic progenitor cells that are capable of maintaining the disease in vitro and in vivo differ from normal hematopoietic progenitor cells in their lack of expression of Thy-1.
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PMID:Lack of expression of Thy-1 (CD90) on acute myeloid leukemia cells with long-term proliferative ability in vitro and in vivo. 912 12

On the subject of acute myeloid leukemia (AML), there is little consensus about the target cell within the hematopoietic stem cell hierarchy that is susceptible to leukemic transformation, or about the mechanism that underlies the phenotypic, genotypic and clinical heterogeneity. Here we demonstrate that the cell capable of initiating human AML in non-obese diabetic mice with severe combined immunodeficiency disease (NOD/SCID mice) - termed the SCID leukemia-initiating cell, or SL-IC - possesses the differentiative and proliferative capacities and the potential for self-renewal expected of a leukemic stem cell. The SL-ICs from all subtypes of AML analyzed, regardless of the heterogeneity in maturation characteristics of the leukemic blasts, were exclusively CD34++ CD38-, similar to the cell-surface phenotype of normal SCID-repopulating cells, suggesting that normal primitive cells, rather than committed progenitor cells, are the target for leukemic transformation. The SL-ICs were able to differentiate in vivo into leukemic blasts, indicating that the leukemic clone is organized as a hierarchy.
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PMID:Human acute myeloid leukemia is organized as a hierarchy that originates from a primitive hematopoietic cell. 921 98

Long-term cultures (LTC) and immunodeficient (NOD/SCID) mice have been used to quantitate and characterize primitive malignant progenitors from patients with acute myelogenous leukemia (AML). In 5-week-old LTC of cells from newly diagnosed patients with AML cytogenetically abnormal as well as normal progenitors could be easily detected and their numbers increased by cytokine supplements to the cultures. Sixty percent of AML samples will engraft in NOD/SCID mouse marrow. The frequency and level of engraftment of human cells detected appears to vary among the different subtypes of AML but is not generally affected by treatment of the mice with human cytokines. Both the LTC and NOD/SCID mouse assay show promise as tools to allow characterization of differences between leukemic stem cells which maintain malignant hematopoiesis in individual patients and, more importantly, between these cells and their normal stem cell counterparts.
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PMID:Cytokine responsiveness of primitive progenitors in acute myelogenous leukemia. 944 47

Acute myeloid leukemia (AML) occurs as the result of malignant transformation in a hematopoietic progenitor cell, which proliferates to form an accumulation of AML blasts. Only a minority of these AML cells are capable of proliferation in vitro, suggesting that AML cells may be organized in a hierarchy, with only the most primitive of these cells capable of maintaining the leukemic clone. To further investigate this hypothesis, we have evaluated a strategy for purifying these primitive cells based on surface antigen expression. As an in vitro endpoint, we have determined the phenotype of AML progenitor cells which are capable of producing AML colony-forming cells (CFU) for up to 8 weeks in suspension culture (SC) and compared the phenotype with that of cells which reproduce AML in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. AML cells were fluorescence-activated cell sorted (FACS) for coexpression of CD34 and CD71, CD38, and/or HLA-DR and the subfractions were assayed in vitro and in vivo at various cell doses to estimate purification. While the majority of primary AML CFU lacked expression of CD34, most cells capable of producing CFU after 2 to 8 weeks in SC were CD34(+)/CD71(-). HLA-DR expression was heterogeneous on cells producing CFU after 2 to 4 weeks. However, after 6 to 8 weeks in SC, the majority of CFU were derived from CD34(+)/HLA-DR- cells. Similarly, the majority of cells capable of long-term CFU production from SC were CD34(+)/CD38(-). Most cells that were capable of engrafting NOD/SCID mice were also CD34(+)/CD71(-) and CD34(+)/HLA-DR-. Engraftment was not achieved with CD34(+)/CD71(+) or HLA-DR+ subfractions, however, in two patients, both the CD34(+) and CD34(-) subfractions were capable of engrafting the NOD/SCID mice. A three-color sorting strategy combining these antigens allowed approximately a 2-log purification of these NOD/SCID leukemia initiating cells, with engraftment achieved using as few as 400 cells in one experiment. Phenotyping studies suggest even higher purification could be achieved by combining lack of CD38 expression with the CD34(+)/CD71(-) or CD34(+)/HLA DR- phenotype. These results suggest that most AML cells capable of long-term proliferation in vitro and in vivo share the CD34(+)/CD71(-)/HLA-DR- phenotype with normal stem cells. Our data suggests that in this group of patients the leukemic transformation has occurred in a primitive progenitor, as defined by phenotype, with some degree of subsequent differentiation as defined by functional assays.
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PMID:Most acute myeloid leukemia progenitor cells with long-term proliferative ability in vitro and in vivo have the phenotype CD34(+)/CD71(-)/HLA-DR-. 983 39

Little is known about the cell types or mechanisms that underlie the engraftment process. Here, we have examined parameters affecting the engraftment of purified human Lin-CD34+CD38- normal and AML cells transplanted at limiting doses into NOD/SCID recipients. Mice transplanted with 500 to 1000 Lin-CD34+CD38- cord blood (CB) or AML cells required the co-transplantation of accessory cells (ACs) or short-term in vivo cytokine treatment for engraftment, whereas transplantation of higher doses (>5000 Lin-CD34+CD38- cells) did not show these requirements suggesting that ACs are effective for both normal and leukemic stem cell engraftment in this model. Mature Lin+CD34- and primitive Lin-CD34+CD38+ cells were capable of acting as ACs even though no repopulating cells are present. Cytokine treatment of NOD/SCID mice could partially replace the requirement for co-transplantation of AC. Furthermore, no difference was seen between the percentage of engrafted mice treated with cytokines for only the first 10 days after transplant compared to those receiving cytokines for the entire time of repopulation. Surprisingly, no engraftment was detected in mice when cytokine treatment was delayed until 10 days posttransplant. Together, these studies suggest that the engraftment process requires pluripotent stem cells plus accessory cells or cytokine treatment which act early after transplantation. The NOD/SCID xenotransplant system provides the means to further clarify the processes underlying human stem cell engraftment.
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PMID:Cytokine treatment or accessory cells are required to initiate engraftment of purified primitive human hematopoietic cells transplanted at limiting doses into NOD/SCID mice. 1008 50

The use of immunodeficient mice, particularly of the nonobese diabetic/severe combined immunodeficient (NOD/SCID) strain, has allowed detection of very primitive malignant progenitors from patients with acute myelogenous leukemia (AML). To define the sensitivity and reproducibility with which the engraftment of different AML cells can be detected, 61 different samples from patients with newly diagnosed AML representing a variety of cytogenetic and French-American-British (FAB) subtypes were injected into NOD/SCID mice. Eight weeks after intravenous injection of 10(7) AML cells, the average percent of human cells in mouse bone marrow was 13.3%, with 70% of samples showing easily detectable engraftment of CD45(+) cells. AML samples with cytogenetic changes associated with a poor clinical prognosis tended to engraft to higher levels than those with changes associated with a good prognosis. Cells with FAB subtypes M3 and, to a lesser extent, M2, engrafted more poorly (P =.002 and.06, respectively) than those from other subtypes. Intraperitoneal injection of human interleukin-3 and Steel factor thrice weekly for 4 weeks did not enhance the levels of AML cell engraftment. However, AML samples that showed cytokine-independent colony growth in methylcellulose assay or expressed growth-factor mRNA in malignant blasts achieved significantly higher levels of engraftment than those which were cytokine dependent in culture or failed to express cytokine message (P <.03 and P <.02, respectively). In 6 patient samples, the frequency of NOD/SCID leukemia-initiating cells (NOD/SL-IC) varied from 0.7 to 45 per 10(7) cells, which was 200- to 800-fold lower than the frequency of AML long-term culture-initiating cells (AML LTC-IC) in the same samples. Each NOD/SL-IC will produce more than 10(6) leukemic blasts as well as many AML-CFC and AML LTC-IC as detected 8 weeks postinjection into mice. Serial transplant experiments showed the ability of NOD/SL-IC to maintain their own numbers over at least 3 to 4 weeks in vivo. The ability of these progenitors to self-renew combined with their potential to differentiate to produce large numbers of more mature progenitors and leukemic blasts suggests that the NOD/SL-IC assay identifies leukemic 'stem cells' that may maintain the malignant clone in human patients. The further use of this assay should facilitate studies of AML stem cell biology and the evolution of novel therapeutic strategies.
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PMID:Growth characteristics of acute myelogenous leukemia progenitors that initiate malignant hematopoiesis in nonobese diabetic/severe combined immunodeficient mice. 1047 2

Rare primitive progenitors among the malignant cells from most patients with AML include AML long-term culture-initiating cells (AML LTC-IC) and NOD/SCID mouse leukemia-initiating cells (NOD/SL-IC). To evaluate the feasibility of genetic modification of these progenitors for gene marking and/ or gene therapy strategies, cells from patients with newly-diagnosed AML were cocultured with retroviral producer cells and then placed in colony (AML-CFC) assays, LTC, and injected intravenously into NOD/SCID mice. Southern blotting demonstrated transfer of the neo(r) gene to 30% to 80% of leukemic blasts when cells were cultured for 48 hours in the presence of IL-3 and steel factor (SF) prior to 48-hour coculture with viral producers. Three of six retrovirally-infected AML samples showed both engraftment in NOD/SCID mice and the presence of the neo(r) transgene in mouse tissues 8-15 weeks after injection of transduced cells. Thirteen weeks after injection of one of these samples, >80% of cells from mouse bone marrow were the progeny of two retrovirally-transduced AML progenitors. Four of the remaining five samples showed markedly reduced ability to engraft in mice after retroviral infection. Subsequent experiments demonstrated that the loss of engraftment potential took place within 24 hours of culture initiation in the absence of retroviral producers and regardless of the cytokines present. Interestingly, the majority of AML-CFC or AML LTC-IC survived the 24-hour culture period. A retroviral vector containing the murine cell surface marker heat stable antigen (HSA), which allows purification of transduced cells on immunomagnetic columns, was used to obtain an enriched population of gene-modified AML cells following an infection protocol that eliminated the 48 hours of prestimulation in IL-3 and SF and reduced coculture with viral producers to 10-36 hours. These modifications failed to improve engraftment of the infected cells. In addition, in these experiments more than 10 hours of cocultivation with viral producer cells was necessary to achieve gene transfer and expression in AML LTC-IC. These data demonstrate that although retroviral-mediated gene transfer can be achieved to AML progenitors, including NOD/SL-IC, improved culture conditions will be required before substantial numbers of such transduced primitive progenitors can be obtained. In addition, the difference in the ability of AML LTC-IC and NOD/SL-IC to survive ex vivo suggests that these assays may detect different populations of cells or that changes are induced in vitro in primitive cells which can only be detected in the mouse assay.
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PMID:Retroviral marking of acute myelogenous leukemia progenitors that initiate long-term culture and growth in immunodeficient mice. 1056 Sep 8

Internal tandem duplications of the FIt3 gene (FIt3/ITDs) are present in about 18% of all AML cases and are therefore one of the most frequent somatic gene mutations in AML. Little is known about the role of FIt3/ITDs in leukemogenesis or their clinical relevance. In this study we compared 18 samples with FIt3/ITDs and 63 AML samples without these mutations with respect to clinical prognosis, cytokine responsiveness, progenitor cell content and repopulation in the NOD/SCID mouse. We found that in patients with a mutation CR rates are reduced (P=0.03) and relapse rates are increased (P=0.01), indicating the prognostic importance of FIt3/ITDs. This is also emphasized by the finding that in patients under the age of 60 years, as well as in older patients the event-free survival was more unfavorable for the mutant patients (P=0.003 and P=0.03, respectively). At diagnosis FIt3/ITD and non-mutant AML bone marrow samples did not differ in their progenitor/stem cell frequencies. Cobblestone area forming cell (CAFC) subsets showed a similar frequency distribution in mutant and non-mutant samples. In 7-day liquid cultures, FIt3/ITD samples showed a reduced growth in response to a variety of myeloid growth factors. In contrast, FIt3/ITD samples displayed a higher ability to engraft the NOD/SCID bone marrow with leukemic cells. Together these data show that the FIt3/ITD represents an important diagnostic marker for patient prognosis, and that the presence of these mutations is associated with altered proliferative ability of progenitors in vivo and in vitro.
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PMID:Biological characteristics and prognosis of adult acute myeloid leukemia with internal tandem duplications in the Flt3 gene. 1076 54

A hierarchy of progenitor cells is thought to exist in human acute myeloid leukemia (AML), with only the most primitive cells capable of proliferating to maintain the malignant clone. To further characterize this AML cell hierarchy, we evaluated the coexpression of CD34 and c-kit (CD117) on cells that are capable of long-term proliferation in vitro and in vivo.AML cells were sorted for coexpression of CD34 and c-kit (CD117) using two c-kit monoclonal antibodies (mAbs), clones 95C3 and 104D2. Sorted subfractions were evaluated for the ability to produce colony-forming units (CFU) for up to 8 weeks in suspension culture (SC) and for the capacity to repopulate NOD/SCID mice. When expression of c-kit on blood cells from 19 AML patients at diagnosis was compared using both mAbs, expression defined by 104D2 (34% +/- 6% c-kit(+)) was somewhat higher than that defined using 95C3 (18% +/- 4%). AML cells were sorted for coexpression of CD34 and c-kit using both c-kit mAbs, and the subfractions were assayed in vitro and in vivo. Whereas the majority of AML blast cells lacked expression of CD34, most AML cells capable of proliferating to produce CFU after 4 to 8 weeks in SC were CD34(+)/c-kit(-). Cultures of sorted CD34(+)/c-kit(-) cells, supplemented with steel factor, were composed of a large proportion (18% to 87%) of CD34(+)/c-kit(+) cells after 1 week, suggesting that either c-kit expression was upregulated or CD34(+)/c-kit(+) cells were produced. Moreover, the CD34(+)/c-kit(-) subfraction was found to be capable of responding to steel factor alone to produce CFU after 4 weeks in SC. In most AML patients tested (11/15), the only sorted subfraction capable of engrafting NOD/SCID mice was CD34(+)/c-kit(-). The CD34(+)/c-kit(+) subfraction from only 2 of the 15 patients and CD34(-) cells from 3 patients also engrafted the NOD/SCIDs. Only the CD34(+)/c-kit(+) subfraction of normal bone marrow engrafted. These studies suggest that primitive AML cells capable of long-term proliferation in vitro and NOD/SCID repopulation differ from primitive normal progenitor cells in their lack of surface expression of c-kit.
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PMID:Primitive acute myeloid leukemia cells with long-term proliferative ability in vitro and in vivo lack surface expression of c-kit (CD117). 1088 Jul 52

Recent studies suggest that the population of malignant cells found in human acute myelogenous leukemia (AML) arises from a rare population of leukemic stem cells (LSCs). LSCs have been documented for nearly all AML subtypes and have been phenotypically described as CD34+/CD38- or CD34+/HLA-DR-. Given the potentially critical role of these primitive cells in perpetuating leukemic disease, we sought to further investigate their molecular and cellular characteristics. Flow cytometric studies using primary AML tissue showed that the interleukin-3 receptor alpha chain (IL-3Ralpha or CD123) was strongly expressed in CD34+/CD38- cells (98 +/- 2% positive) from 16 of 18 primary specimens. Conversely, normal bone marrow derived CD34+/CD38- cells showed virtually no detectable expression of the CD123 antigen. To assess the functional role of IL-3Ralpha positive cells, purified CD34+/CD123+ leukemia cells were transplanted into immune deficient NOD/SCID mice. These experiments showed that CD123+ cells were competent to establish and maintain leukemic populations in vivo. To begin to elucidate a biological role for CD123 in leukemia, primary AML samples were analyzed with respect to signal transduction activity in the MAPK, Akt, and Stat5 pathways. Phosphorylation was not detected in response to IL-3 stimulation, thereby suggesting CD123 is not active in conventional IL-3-mediated signaling. Collectively, these data indicate that CD123 represents a unique marker for primitive leukemic stem cells. Given the strong expression of this receptor on LSCs, we propose that targeting of CD123 may be a promising strategy for the preferential ablation of AML cells.
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PMID:The interleukin-3 receptor alpha chain is a unique marker for human acute myelogenous leukemia stem cells. 1102 53


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