Chronic Myelogenous Leukemia Marrow Research Articles

Inhibition of Chronic Myelogenous Leukemia Stem Cells with Novel Wnt Antagonists.

IntroductionA growing proportion of chronic myelogenous leukemia (CML) patients show evidence of disease progression. Recent research suggests that leukemia stem cells (LSC) that share phenotypic characteristics with granulocyte-macrophage progenitors (GMP) are involved in CML progression. These LSC have aberrantly gained self-renewal capacity as a result of enhanced Wnt/beta-catenin signaling. We assayed the capacity of novel Wnt/beta-catenin antagonists to inhibit CML LSC.MethodsTo assay the efficacy of a novel Wnt inhibitor, MC-001, HEK293 cells were transfected with a Wnt-dependent reporter gene and expression plasmid for Dsh. After 16h, the cells were treated for 24 h with MCC-001, a novel marine sponge derived inhibitor, at varying concentrations and the reporter gene activity was measured. All cells were also transfected with a b-gal reporter gene to control for transfection efficiency. To assess the effects of MCC-001 and other Wnt inhibitors on Wnt/beta-catenin induced self-renewal, hematopoietic stem cells (HSC), GMP and lineage positive cells from normal (n=8) and advanced phase CML (n=8) peripheral blood and marrow (n=8) were clone sorted with the aid of a FACS Aria into methocult media (Stem Cell Technologies) with or without Wnt inhibitors including recombinant Dkk1, lentiviral axin or MCC-001. On day 10, individual colonies were plucked and replated in new methylcellulose and the replating efficiency determined at day 10. To establish an in vivo CML LSC model, HSC, GMP and lineage positive cells were transduced with a lentiviral luciferase GFP for 48 hours and transplanted intrahepatically into newborn immunocompromised mice (RAG2−/−gamma−/−) mice that facilitate high levels of human hematopoietic progenitor engraftment.ResultsThe HEK293 beta-catenin reporter assay revealed that the MC-001 IC50 was 2.1 microM. In comparative Wnt inhibitor replating assays (n=8), recombinant Dkk1 did not inhibit CML HSC (n=8) while lentiviral axin and MCC-001 (at 2 and 10 microM) inhibited both CML HSC and CML GMP at doses that spared normal HSC replating (Figure 1). Transplantation of CML HSC, GMP and lineage positive cells into RAG2−/−gamma−/− mice demonstrated that only CML GMP provided serial transplantation potential and thus, were enriched for the LSC population (Figure 2).ConclusionsSelective Wnt/beta-catenin inhibition with a marine sponge derived beta-catenin antagonist, MCC-001, blocks in vitro replating capacity of CML LSC at doses that spare normal HSC. Current experiments focus on in vivo inhibition of LSC self-renewal with novel Wnt inhibitors in a robust CML LSC bioluminescent imaging model (Figure 2). [Display omitted] [Display omitted]

Chronic myeloid lukemia cells: Tyrosine kinase inhibition using ag 957 and arachidonic acid inducing apoptosis

Chronic myelogenous leukemia (CML) is characterized by Philadelphia chromosome that fuses genetic sequences of the BCR gene on chromosome 22. AG 957, a member of the tyrphostin compound produces a selective inhibition of P 210 BCR/ABL tyrosine phosphorylation. A group of ten patients with CML in chronic phase were treated after CD34 separation with 1 to 100 umol/L of AG 957. All patients were 100% Ph1 positive. Eight patients showed a b3a2 BCR/ABL junction and two cases showed a b2a2 junction when analyzed by RT-PCR. The effect of AG 957 on CML and normal CD34 cells in culture assay (CFU/MIX, BFU-E and CFU-GM) is clearly demonstrated. The inhibition on CML untreated and AG957 treated colonies was from 2%–7% for CFU-MIX, 38%–80% for BFU-E and 31%–18–% for CFU-GM. In the group of normal samples the inhibition ranged from 4%–8% for CFU-MIX, 24%–96% for BFU-E and 4%–64% for CFU-GM. The inhibitory effect of AG 957 on CML progenitors is statistically significant at the dose of 1 umol/L for CFU-MIX and BFU-E, 5 umol/L for CFU-GM. For colonies obtained from normal progenitors the inhibiting dose of AG 957 was more consistent: 5 umol/L for CFU-MIX and BFU-E, 10 umol/L for CFU-GM. These data demonstrated the possibility to select non clonal CML progenitors after incubation with the PTK inhibitor AG 957. This selection of “normal” progenitors from CML marrow could be used for autograft in patients without suitable allogeneic bone marrow donors. The research is in progression to explore the potential therapeutic effect of AG 957 in combination with other agents (IFN - ARA-C) and/or inductors of apoptosis as arachidonic acid in cell culture, to briefly translate the “in vitro” experimental approach to clinical therapeutic application.

Tyrphostin AG957, a tyrosine kinase inhibitor with anti-BCR/ABL tyrosine kinase activity restores beta1 integrin-mediated adhesion and inhibitory signaling in chronic myelogenous leukemia hematopoietic progenitors.

Abnormal beta1 integrin receptor function may contribute to the continuous proliferation and abnormal circulation of malignant hematopoietic progenitors in chronic myelogenous leukemia (CML). Previous studies suggest that abnormal integrin function in CML progenitors is related to the presence of the BCR/ABL oncogene. BCR/ABL may alter integrin function in CML by phosphorylating cytoskeletal and/or signaling proteins important for normal integrin function. We evaluated the effect of Tyrphostin AG957, a protein tyrosine kinase (PTK) inhibitor which has activity against the p210BCR/ABL kinase, on beta1 integrin function in CML progenitors. Incubation of CML marrow CD34+HLA-DR+ cells with Tyrphostin AG957 at concentrations that did not affect colony-forming cells (CFC) viability, but which partly inhibited p210BCR/ABL kinase activity, significantly increased CML CFC adhesion to stroma and alpha4beta1 and alpha5beta1 integrin binding fragments of fibronectin (FN). CML CFC proliferation, unlike that of normal CFC, is not inhibited following integrin receptor engagement with FN or anti-integrin antibodies. AG957 did not alter CML CFC proliferation by itself, but resulted in significant inhibition of CML CFC proliferation following integrin engagement. Another PTK inhibitor, Tyrphostin AG555, which does not have anti-p210BCR/ABL kinase activity, did not affect CML CFC adhesion or proliferation. Neither AG957 nor AG555 affected normal CFC adhesion or proliferation. In BCR/ABL expressing cells, AG957 partially inhibited phosphorylation of several proteins that are BCR/ABL PTK substrates and are involved in normal integrin signaling. These studies suggest that abnormal tyrosine phosphorylation may play an important role in defective integrin function in CML progenitors.

Inhibition of BCR-ABL Expression With Antisense Oligodeoxynucleotides Restores β1 Integrin-Mediated Adhesion and Proliferation Inhibition in Chronic Myelogenous Leukemia Hematopoietic Progenitors

Chronic myelogenous leukemia (CML) is characterized by the continuous proliferation and abnormal circulation of malignant hematopoietic progenitors. This may be related to the unresponsiveness of CML progenitors to beta1 integrin adhesion receptor-mediated inhibition of progenitor proliferation by the marrow microenvironment. In hematopoietic cell lines, the BCR-ABL oncogene product, p210(BCR-ABL), interacts with a variety of cytoskeletal elements important for normal integrin signaling. We studied the role of p210(BCR-ABL) in abnormal integrin function in CML by evaluating the effect of inhibition of BCR-ABL expression with antisense oligodeoxynucleotides (AS-ODNs) on integrin-mediated adhesion and proliferation inhibition of malignant primary progenitors from CML marrow. Preincubation of CML CD34(+)HLA-DR+ (DR+) cells with breakpoint-specific AS-ODNs significantly increased adhesion of CML progenitors to stroma and fibronectin (FN). Pretreatment with breakpoint-specific ODNs also resulted in significant inhibition of CML progenitor proliferation after ligand or antibody-mediated beta1 integrin engagement. Breakpoint-specific ODNs were significantly more effective in restoring CML progenitor adhesion and proliferation inhibition than control ODNs. BCR-ABL mRNA and p210(BCR-ABL) levels in CML CD34(+) cells were significantly reduced after incubation with breakpoint-specific AS-ODN. These studies indicate a role for BCR-ABL in abnormal circulation and defective integrin-dependent microenvironmental regulation of proliferation of CML hematopoietic progenitors.

Selection of Myeloid Progenitors Lacking BCR/ABL mRNA in Chronic Myelogenous Leukemia Patients After In Vitro Treatment With the Tyrosine Kinase Inhibitor Genistein

Chronic myelogenous leukemia (CML) is a clonal disorder of the hematopoietic stem cell characterized by a chimeric BCR/ABL gene giving rise to a 210-kD fusion protein with dysregulated tyrosine kinase activity. We investigated the effect of genistein, a protein tyrosine kinase inhibitor, on the in vitro growth of CML and normal marrow-derived multi-potent (colony-forming unit-mix [CFU-Mix]), erythroid (burst-forming unit-erythroid [BFU-E]), and granulocyte-macrophage (colony-forming unit-granulocyte-macrophage [CFU-GM]) hematopoietic progenitors. Continuous exposure of CML and normal marrow to genistein induced a statistically significant and dose-dependent suppression of colony formation. Genistein doses causing 50% inhibition of CML and normal progenitors were not significantly different for CFU-Mix (27 mumol/L v 23 mumol/L), BFU-E (31 mumol/L v 29 mumol/L), and CFU-GM (40 mumol/L v 32 mumol/L v 32 mumol/L). Preincubation of CML and normal marrow with genistein (200 mumol/ L for 1 to 18 hours) induced a time-dependent suppression of progenitor cell growth, while sparing a substantial proportion of long-term culture-initiating cells (LTC-IC) from CML (range, 91% +/- 9% to 32% +/- 3%) and normal marrow (range, 85% +/- 8% to 38% +/- 9%). Analysis of individual CML colonies for the presence of the hybrid BCR/ABL mRNA by reverse transcription-polymerase chain reaction (RT-PCR) showed that genistein treatment significantly reduced the mean +/- SD percentage of marrow BCR/ABL+ progenitors both by continuous exposure (76% +/- 18% v 24% +/- 12%, P < or = .004) or preincubation (75% +/- 16% v 21% +/- 10%, P < or = .002) experiments. Preincubation with genistein reduced the percentage of leukemic LTC-IC from 87% +/- 12% to 37% +/- 12% (P < or = .003). Analysis of individual colonies by cytogenetics and RT-PCR confirmed that genistein-induced increase in the percentage of nonleukemic progenitors was not due to suppression of BCR/ABL transcription. Analysis of nuclear DNA fragmentation by DNA gel electrophoresis and terminal deoxynucleotidyl transferase assay showed that preincubation of CML mononuclear and CD34+ cells with genistein induced significant evidence of apoptosis. These observations show that genistein is capable of (1) exerting a strong antiproliferative effect on CFU-Mix, BFU-E, and CFU-GM while sparing the more primitive LTC-IC and (2) selecting benign hematopoietic progenitors from CML marrow, probably through an apoptotic mechanism.

BCR/ABL-Negative Primitive Progenitors Suitable for Transplantation Can Be Selected From the Marrow of Most Early-Chronic Phase But Not Accelerated-Phase Chronic Myelogenous Leukemia Patients

We have previously reported that selection of marrow cells on the basis of the CD34+HLA-DR- phenotype (34+DR-) may result in the recovery of Philadelphia chromosome (Ph)- and BCR/ABL-negative long-term culture-initiating cells (LTC-IC) in selected patients with chronic myelogenous leukemia (CML). We now present data on 27 early chronic-phase ([ECP] studied within 1 year after diagnosis) and 23 advanced-phase ([AP] late chronic phase, ie, studied >1 year from diagnosis, or accelerated phase) CML patients. Fluorescence-activated call-sorting (FACS)-selected 34+DR- and 34+DR+ cells were subjected to reverse transcriptase-polymerase chain reaction and fluorescence in situ hybridization. These cells were also cultured in long-term bone marrow culture for 1 to 5 weeks to examine the number of LTC-IC and the presence or absence of the BCR/ABL gene rearrangement in progeny of primitive LTC-IC. The number of 34+DR- cells and LTC-IC present in ECP CML marrow was similar to that in normal (NL) marrow, whereas the numbers were reduced in AP CML. Furthermore, 34+DR- cells from more than 80% of ECP CML patients were BCR/ABL mRNA- and Ph-negative and contained only BCR/ABL mRNA- and Ph-negative LTC-IC, whereas 34+DR- cells and LTC-IC from less than 40% of AP CML patients were BCR/ABL mRNA- and Ph-negative. In contrast to NL marrow, 34+DR+ cells from CML marrow, irrespective of clinical stage, contained large numbers of LTC-IC. CML 34+DR+ cells and LTC-IC were BCR/ABL mRNA- and Ph-positive. Since these studies suggested that a population of primitive progenitors that are Ph-negative can be selected from steady-state marrow in some ECP CML patients, we determined if similar results could be obtained when large quantities of marrow sufficient for transplantation are processed. We demonstrate that 1 to 3 x 10(5) BCR/ABL mRNA-negative 34+DR- cells/kg recipient body weight, containing only BCR/ABL mRNA-negative LTC-IC, can be obtained from a 2- to 2.5-L marrow collection by sequential COBE Spectra apheresis (COBE BCT, Lakewood, CO), CD34+ enrichment using the CEPRATE SC Cell-Concentrator (CellPro, Bothell, WA), and high-speed FACS. Thus, large-scale selection of a BCR/ABL mRNA- and Ph-negative 34+DR- cell population is possible in a fraction of chronic-phase CML patients, in whom these cells could be used to reconstitute the hematopoietic compartment following autologous transplantation.

Autologous Activated Natural Killer Cells Suppress Primitive Chronic Myelogenous Leukemia Progenitors in Long-Term Culture

A graft-versus-leukemia effect has been well documented to prevent relapse in chronic myelogenous leukemia (CML) after allogeneic marrow transplantation. One type of lymphocytes that may contribute to this effect are natural killer cells (NK), which after activation with interleukin (IL)-2, exhibit a broad range of cytolytic activity against allogeneic and autologous cells. We have previously demonstrated that IL-2-activated NK (ANK) can be generated from blood of patients with CML and are benign in origin. Their proliferation and function, however, diminish with disease progression in CML, suggesting a role in tumor surveillance. We studied the effect of IL-2-activated NK (ANK) on normal and malignant primitive and committed progenitors in a novel long-term bone marrow culture (LTBMC) assay. Because ANK destroy marrow stromal layers, the use of classic stroma-dependent long-term cultures is not possible. Therefore, we used the stroma noncontact LTBMC system developed in our laboratory to analyze the effect of autologous ANK cells on primitive hematopoietic progenitors. Autologous ANK (CD56+/CD3-) were generated from the peripheral blood of 10 patients with chronic phase CML and from six normal individuals by culturing CD5/CD8-depleted mononuclear cells for 14 days in 1,000 U/mL IL-2. At the same time ANK cultures were initiated, sorted normal (CD34+/DR+) marrow populations were plated in Transwell inserts of the stroma noncontact culture. On day 15, hydrocortisone, which rapidly inhibits ANK function, was removed, and autologous ANK were added to the Transwell inserts with fresh LTBMC medium without hydrocortisone but supplemented with 1,000 U/mL IL-2. After 48 hours, the number of colony-forming cells (CFC) was enumerated in methylcellulose culture. To determine the effect of ANK on more primitive long-term culture-initiating cells (LTCIC), the IL-2-supplemented LTBMC medium was replaced with fresh hydrocortisone containing LTBMC medium, and cultures were maintained for an additional 5 weeks. We demonstrate that autologous ANK did not suppress normal CFC or LTCIC. In contrast, ANK from eight patients with CML with potent cytotoxicity against NK-sensitive (K562) NK-resistant (Raji) tumor targets exhibited an ANK dose-dependent suppression of both CFC and LTCIC. Interestingly, ANK from two patients with CML who exhibited diminished cytotoxicity also did not suppress autologous CFC and LTCIC. These studies indicate that ANK with potent major histocompatibility complex unrestricted cytotoxic activity suppress malignant hematopoiesis. This effect was not mediated by soluble factors and was absolutely dependent on direct cell-to-cell contact. We further demonstrate that the beta2 integrin receptor is involved in ANK recognition of CML targets. These observations support the use of autologous ANK therapy to prevent relapse of CML after autologous marrow transplantation or use of ANK to purge CML marrow for autologous transplantation.

Benign Marrow Progenitors Are Enriched in the CD34+/HLA-DRlo Population But Not in the CD34+/CD38lo Population in Chronic Myeloid Leukemia: An Analysis Using Interphase Fluorescence In Situ Hybridization

Fluorescence in situ hybridization (FISH) was used to discriminate between benign and malignant cells in sorted populations of chronic myelogenous leukemia (CML) marrow. FISH has the advantage of allowing for a cell by cell analysis of the breakpoint cluster region (BCR) gene rearrangement immediately after flow sorting in nondividing G0/G1 cells that are potentially transcriptionally inactive. We initially selected CD34+ cells with very low expression of the activation antigen CD38 as a candidate phenotype for an immature and hypothetically more benign cell population, but found no enrichment for Ph negativity in that subtype. In five CML samples, 55% +/- 3.3% (mean +/- SE) of CD34+/CD38hi cells had the BCR gene rearrangement, similar to 57% +/- 3.7% seen in the CD34+/CD38lo population. In contrast, subsequent experiments (n = 4) determined that the CD34+/HLA-DRlo population in CML marrow does contain an increased proportion of benign cells: 15% +/- 1% of the CD34+/DRlo cells were BCR rearranged, compared with 52% +/- 5.8% of the CD34+/DRhi cells (P = .001). Our results indicate that benign progenitors in CML are enriched within the CD34+ cells with low DR antigen expression, but not low CD38 expression. One possible interpretation of these observations is that low CD38 antigen expression is not as useful as low HLA-DR expression for isolating immature cells.

Abnormal Function of the Bone Marrow Microenvironment in Chronic Myelogenous Leukemia: Role of Malignant Stromal Macrophages

The bone marrow microenvironment supports and regulates the proliferation and differentiation of hematopoietic cells. Dysregulated hematopoiesis in chronic myelogenous leukemia (CML) is caused, at least in part, by abnormalities in CML hematopoietic progenitors leading to altered interactions with the marrow microenvironment. The role of the microenvironment itself in CML has not been well characterized. We examined the capacity of CML stroma to support the growth of long-term culture-initiating cells (LTC-IC) obtained from normal and CML marrow. The growth of normal LTC-IC on CML stroma was significantly reduced compared with normal stroma. This did not appear to be related to abnormal production of soluble factors by CML stroma because normal LTC-IC grew equally well in Transwells above CML stroma as in Transwells above normal stroma. In addition, CML and normal stromal supernatants contained similar quantities of both growth-stimulatory (granulocyte colony-stimulating factor (CSF), interleukin-6, stem cell factor, granulocyte-macrophage CSF, and interleukin-1 beta) and growth-inhibitory cytokines (transforming growth factor-beta, macrophage inflammatory protein-1 alpha, and tumor necrosis factor-alpha). The relative proportion of different cell types in CML and normal stroma was similar. However, polymerase chain reaction and fluorescence in situ hybridization studies showed the presence of bcr-abl-positivo cells in CML stroma, which were CD14+ stromal macrophages. To assess the effect of these malignant macrophages on stromal function, CML and normal stromal cells were separated by fluorescence-activated cell sorting into stromal mesenchymal cell (CD14-) and macrophage (CD14+) populations. CML and normal CD14- cells supported the growth of normal LTC-IC equally well. However, the addition of CML macrophages to normal or CML CD14- mesenchymal cells resulted in impaired progenitor support. This finding indicates that the abnormal function of CML bone marrow stroma is related to the presence of malignant macrophages. In contrast to normal LTC-IC, the growth of CML LTC-IC on allogeneic CML stromal layers was not impaired and was significantly better than that of normal LTC-IC cocultured with the same CML stromal layers. These studies demonstrate that, in addition to abnormalities in CML progenitors themselves, abnormalities in the CML marrow microenvironment related to the presence of malignant stromal macrophages may contribute to the selective expansion of leukemic progenitors and suppression of normal hematopoiesis in CML.

Long-Term Culture of Chronic Myelogenous Leukemia Marrow Cells on Stem Cell Factor-Deficient Stroma Favors Benign Progenitors

Long-term culture of marrow from patients with chronic myelogenous leukemia (CML) has been reported to favor the outgrowth of bcr/abl- progenitor cells in some patients. We examined the effect of the presence of soluble or transmembrane forms of stem cell factor (SCF) in long-term cultures of CML marrow. CD34-enriched cells from CML patients in advanced chronic phase or accelerated phase were plated on immortalized fetal liver stromal cells from homozygous SCF-deficient SI/SI mice (SI/SI4) with or without the addition of soluble human SCF, SI/SI4 cells expressing high levels of the transmembrane form of human SCF (SI/SIh220), or primary human allogeneic stroma. Cells were removed from cultures and plated weekly in colony assays. The clonagenic cell output from cultures completely lacking SCF was lower over the first 2 to 3 weeks, but by 5 weeks was similar to the clonagenic cell output from the other culture conditions. Analysis of bcr/abl transcripts from individual colonies showed a lower percentage of malignant progenitors present in long-term cultures completely deficient in SCF than under the other culture conditions, particularly compared with primary human stroma-containing long-term cultures. SCF may specifically favor malignant versus benign progenitor cells present in the marrow of CML patients, and an abnormal proliferative response to SCF in very primitive cells may be an underlying defect in the pathophysiology of this disease.

Autografting for chronic myelogenous leukemia.

Two thirds of patients with chronic myelogenous leukemia do not have suitable donors for allogeneic transplantation. As for other leukemias, autografting may potentially be curative, because normal Ph- hematopoietic stem cells persist in the marrow and blood of patients with chronic myelogenous leukemia. Several studies indicate that use of unpurged autologous blood or marrow grafts may extend survival for patients undergoing transplantation in chronic phase. Ex vivo or in vivo purging of chronic myelogenous leukemia marrow or blood prior to autografting may result in increased cytogenetic remissions after transplantation in those patients in whom the Ph+ clone can be eliminated. However, when the Ph+ clone cannot be eliminated, use of purged rather than unpurged autografts provides no advantage and may be associated with increased graft failure. Although sustained cytogenetic remissions have not been observed, autografting may result in a plateau in the survival curve not observed with conventional chemotherapy. Efforts are currently directed toward developing improved methods of purging as well as posttransplantation treatments directed against leukemic cells persisting after myeloablative therapy.

Fractionation of chronic myelogenous leukemia marrow cells by stroma adherence: implications for marrow purging.

Chronic myelogenous leukemia (CML) progenitor cells have been shown to be defective in their ability to adhere to marrow stroma. It was the aim of the present study to investigate at the cytogenetic level marrow-derived CML clonogenic cells fractionated on the basis of their ability to adhere to preformed, allogeneic, normal marrow-derived stromal layers. Mononuclear marrow cells from CML patients (n = 15) were incubated with mafosfamide (100 micrograms/ml) or control medium, seeded onto marrow stromal layers and allowed to adhere (3 hrs, 37 degrees C). Following a short-term liquid culture, the different cell fractions were harvested and incorporated in methylcellulose cultures. CFU-GM grown from these cultures were analyzed by single colony karyotyping. On direct cytogenetic analysis, the overall mean (+/- SD) percentage of Ph-negative metaphases was 7 +/- 20%. Following stroma adherence and shortterm suspension culture, the mean (+/- SD) percentages of Ph-negative clones were as follows: 33 +/- 25% for adherent CFU-GM, 59 +/- 40% for adherent, mafosfamide-treated CFU-GM, 12 +/- 16% for non-adherent CFU-GM, and 32 +/- 26% for non-adherent-mafosfamide-treated CFU-GM. If only the patients showing a percentage of Ph-negative clones > or = 20% were included in this analysis, the mean (+/- SD) percentages of Ph-negative clones were 47 +/- 19% for adherent CFU-GM, and 81 +/- 21% for adherent-Mafosfamide-treated CFU-GM. In contrast, the majority of pH-positive CFU-GM were detected within the stroma non-adherent cell fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular analysis of retroviral transduction in chronic myelogenous leukemia.

We have developed a polymerase chain reaction (PCR) assay for detection of integrated retroviral transgenomes containing the neo G418 resistance gene in colonies (40 cells or more) grown in G418 selection after exposure to the neo-positive retrovirus LNL6. This assay also provides for simultaneous characterization of these colonies as belonging to a chronic myelogenous leukemic (bcr-abl positive) or nonleukemic population (bcr-abl negative). Using these techniques, we assessed transduction of the LNL6 retrovirus into the normal and leukemic cells of a blast-crisis chronic myelogenous leukemia (CML) patient. This work was designed to support the use of the LNL6 retroviral marker to help identify the origin of relapse after autologous marrow infusion. The data from these experiments show that the majority of CML blast crisis cells that, following exposure to the LNL6 virus, produce colonies under rigorous G418 selection are indeed transduced by the virus, as shown by the presence of the neo retroviral gene. Most of these colonies are also shown to be leukemic by PCR detection of the bcr-abl RNA. This demonstrates the feasibility of the study of CML marrow for retroviral marking. These procedures will be of use in establishing if relapse arises from leukemic blasts which contaminate purged autologous bone marrow infused following intensive therapy for leukemia.

A phosphatase activity present in peripheral blood myeloid cells of chronic myelogenous leukemia patients but not normal individuals alters nuclear protein binding to transcriptional enhancers of interferon-inducible genes.

Cytoplasmic protein from peripheral blood myeloid cells of chronic myelogenous leukemia (CML) patients altered the electrophoretic mobility of complexes formed between nuclear proteins and interferon-inducible transcriptional enhancers. Immature myeloid marrow cells (blasts and promyelocytes) have a higher level of this activity than do mature myeloid marrow cells (bands and polys). This activity, which is not detectable in the peripheral blood cells of normal individuals, is at least 50-fold higher in CML marrow blasts and promyelocytes than that found in marrow blasts and promyelocytes of normal individuals. This activity was inhibited by in vivo incubation of immature myeloid cells with the phosphatase inhibitor, sodium orthovanadate (0.2 mM), and by adding orthovanadate (20 mM) directly to cytoplasmic proteins of myeloid cells. Interferon-alpha (1,000 U/ml) reduced the effects of the CML myeloid cell cytoplasmic protein on the electrophoretic mobility of nuclear protein-DNA complexes. These data suggest that a unique phosphatase may be involved in the abnormalities in CML which are modulated by interferon-alpha.

Proliferative Potential of Subpopulations of Granulocyte-Macrophage Progenitor Cells in Normal Subjects and Chronic Myelogenous Leukemia Patients

AbstractThe studies described compare the subpopulations of granulocyte-macrophage progenitor cells present in normal marrow with those derived from the marrow of patients with Ph1-positive chronic myelogenous leukemia (CML). The subpopulations were separated on the basis of size by velocity sedimentation and measured for their proliferative capacity by the colony formation technique. A pattern of development of colonies in the individual fractions was obtained by assaying the absolute number of colonies present at time intervals from 3 to 21 days. The number of colonies present at 3 days was taken as 100%, and the percentage of increase or decrease from this value was determined on subsequent days. In the fractions containing the most rapidly sedimenting large cells, the pattern of development of colonies derived from normal and CML marrow was similar. The CML colony-forming units in culture (CFU-C) began to show a deviation from the normal CFU-C pattern of development in the fractions containing CFU-C intermediate in size, and this deviation became progressively more pronounced in the slowest sedimenting small cell fractions. In these latter fractions, the CFU-C derived from CML marrow decreased in number at a rate similar to those arising from the more rapidly sedimenting fractions. This is in contrast to CFU-C derived from normal marrow, which increased in number in the more slowly sedimenting fractions and in the intermediate fractions, remained constant in number, or decreased at a rate slower than those arising from the more rapidly sedimenting fractions. The most likely explanation for these findings is accelerated maturation of the early small granulocyte-macrophage progenitor cells in CML so that these cells show the same limited proliferative capacity as do the later larger progenitor cells.

Proliferative potential of subpopulations of granulocyte-macrophage progenitor cells in normal subjects and chronic myelogenous leukemia patients

The studies described compare the subpopulations of granulocyte-macrophage progenitor cells present in normal marrow with those derived from the marrow of patients with Ph1-positive chronic myelogenous leukemia (CML). The subpopulations were separated on the basis of size by velocity sedimentation and measured for their proliferative capacity by the colony formation technique. A pattern of development of colonies in the individual fractions was obtained by assaying the absolute number of colonies present at time intervals from 3 to 21 days. The number of colonies present at 3 days was taken as 100%, and the percentage of increase or decrease from this value was determined on subsequent days. In the fractions containing the most rapidly sedimenting large cells, the pattern of development of colonies derived from normal and CML marrow was similar. The CML colony-forming units in culture (CFU-C) began to show a deviation from the normal CFU-C pattern of development in the fractions containing CFU-C intermediate in size, and this deviation became progressively more pronounced in the slowest sedimenting small cell fractions. In these latter fractions, the CFU-C derived from CML marrow decreased in number at a rate similar to those arising from the more rapidly sedimenting fractions. This is in contrast to CFU-C derived from normal marrow, which increased in number in the more slowly sedimenting fractions and in the intermediate fractions, remained constant in number, or decreased at a rate slower than those arising from the more rapidly sedimenting fractions. The most likely explanation for these findings is accelerated maturation of the early small granulocyte-macrophage progenitor cells in CML so that these cells show the same limited proliferative capacity as do the later larger progenitor cells.