BCR/ABL-negative progenitors are enriched in the adherent fraction of CD34+ cells circulating in the blood of chronic phase chronic myeloid leukemia patients

Abstract

Philadelphia chromosome-positive (Ph + ) hemopoietic cells precan be mobilized, presumably from the bone marrow, into the dominate in patients with chronic myeloid leukemia (CML) in blood of CML patients following chemotherapy. 9 The blood of chronic phase, but some Ph − presumably normal stem cells CML patients has also been used for autologous rescue followpersist in most patients. Ph − cells are relatively frequent, coming high-dose therapy and in some cases Ph chromosomepared to mature cell populations, in primitive hemopoietic cell negative recovery has been observed. 10 IntroductionThe results show that primitive BCR/ABL − cells circulate in the blood of chronic phase CML patients. They are enriched Chronic myeloid leukemia (CML) is characterized by a in the fraction of CD34 + cells that adhere to tissue culture reciprocal translocation between chromosomes 9 and 22 plastic and are predominantly CD33, CD38 and HLA-DR anti-(t[9;22][q34;q11]) which results in the formation of the Philagen-negative. These findings support the view that adhesion delphia (Ph) chromosome. 1 At the molecular level, the Ph to plastic is a property of very primitive normal hemopoietic chromosome involves the fusion of the BCR and ABL genes cells, [18][19][20][21][22] and have implications for the use of peripheral and the production of a p210 protein tyrosine kinase. 2,3 It is blood cells for autografting patients with CML. likely that the rearrangement of BCR and ABL is responsible for the expansion of pluripotent leukemic stem cells and the production of large numbers of committed myeloid, erythroid and megakaryocytic progeny in CML. 4 It may also be responMaterials and methods sible for the adhesive defect that characterizes primitive progenitor cells in CML. 5,6 Cells Good evidence for the persistence of normal hemopoietic stem cells in the marrow of patients with CML has been provided by the Ph chromosome-negative recovery of patients Peripheral blood cells were obtained from patients with treated with ␣-interferon 7 and Ph − hemopoiesis seen after chronic phase (CP) CML in the outpatient clinic ( Norway) according to the manufacturer's instructions.

Proliferating status of peripheral blood progenitor cells from patients with BCR/ABL-positive chronic myelogenous leukemia

“…For patients with newly diagnosed BCR/ABL-positive CML, we showed that CD34 + HPC isolated from PB or BM are predominantly BCR/ABL-positive, which is in accordance with results reported by others. 28 We conclude that in the CML cases, the significantly increased proliferation is caused by BCR/ABLpositive HPC. As an additional confounder, one might argue that BCR/ABL-negative PBPC could be enriched among CD34 + /CD38 low cells.…”

Treatment with interferon-alpha preferentially reduces the capacity for amplification of granulocyte-macrophage progenitors (CFU-GM) from patients with chronic myeloid leukemia but spares normal CFU-GM.

“…Coverslips were then removed, and the slides were washed twice in 2 ϫ SSC, thrice in 50% formamide/2 ϫ SSC pH 7.0-7.2, once in PBS, stained with DAPI, and mounted using Vectashield (Vector Laboratories Inc., Burlingame, CA). BCR-ABL-positive cells were identified by the coincidence of the green and orange signals (20).…”

“…Primitive pre-CFU-GM progenitor cells were assayed as previously described (18,19). The assay detects the activity of CD34-positive cells that are predominantly CD33, CD38, and HLA-DR negative and are capable of producing erythroid BFU-E as well as CFU-GM (19,20). In brief, the mononuclear cell fraction was separated from the blood and bone marrow samples by using Lymphoprep (Nycomed, Oslo, Norway), washed three times, and resuspended in alpha medium (GIBCO, Paisley, UK) supplemented with 15% FCS.…”

Cell biology of CML cells

“…We found that the frequency of Ph-negative cells was significantly higher in this cell population (P = 0.001) than amongst less primitive CD34-positive non-adherent cells, but that the majority (Ͼ80%) of the cells were Ph-positive. 2 The detection of BCR-ABL-negative primitive cells in CML patients in whom 100% of the mature cells are BCR-ABL-positive implies that normal cell proliferation is inhibited by the leukaemia clone. The mechanism for this suppression is not clear but might relate to negative feedback from the greatly increased neutophil count.…”

“…1 Another challenge is to document the fate of the residual normal haemopoietic stem cell population since this is crucial for the success of any treatment strategies apart from allogeneic bone marrow transplantation. The coexistence of primitive Ph-negative cells with primitive Ph-positive cells 2,3 and the virtual absence of mature Ph-negative cells from the blood and bone marrow of patients with chronic phase CML suggests that the Ph-positive clone suppresses mature cell production by normal Ph-negative pluripotent stem cells. Presumably, however, suppression of normal haemopoiesis requires some expansion of the Ph-positive clone, and is not a feature of CML at its inception.…”