Pgp and MRP activities using calcein-AM are prognostic factors in adult acute myeloid leukemia patients

Thirteen cell lines with different levels of Pgp and MRP expression were used to assess the ability of calcein acetoxymethyl ester (calcein-AM) uptake and calcein efflux to measure Pgp and MRP functions, respectively. There was a good correlation between MRP expression and the modulatory effect of probenecid (a specific modulator of MRP) on the calcein efflux (r = .91, P = .0003) and between Pgp expression and the modulatory effect of CsA on calcein-AM uptake (r = .96, P < .0001). In light of the high correlations for both proteins, we tested calcein-AM uptake and efflux in fresh myeloid leukemic cells. In 53 acute myeloid leukemia (AML) patients, there was also a good correlation between MRP expression (measured by reverse transcription-polymerase chain reaction and by MRPm6 expression by flow cytometry) and the modulatory effect of probenecid on the calcein fluorescence (r = .92, P < .0001) and between Pgp expression as measured by UIC2 antibody binding on flow cytometry and the modulatory effect of cyclosporin A on calcein-AM uptake (r = .83, P < .0001). Pgp activity was higher in CD34+ leukemia than in CD34- leukemia (2.26 +/- 1.50 v 1.46 +/- 1.21, respectively; P = .003), and MRP activity was higher in CD34- leukemia than in CD34+ leukemia (1.77 +/- 0.40 v 1.4 +/- 0. 29, respectively; P = .004). Pgp expression and activity (P = .004 and P = .01, respectively) and MRP activity (P = .03) but not MRP expression were prognostic factors for achievement of complete remission. These results suggest that functional testing (with calcein-AM +/- modulators) for the presence of both MRP and Pgp activities is of prognostic value and that MRP contributes to drug resistance in AML.

Butyrate-stable monosaccharide derivatives induce maturation and apoptosis in human acute myeloid leukaemia cells

The rapid degradation and subsequent lack of efficacy of n-butyric acid in vivo has been improved by the synthesis of monosaccharide stable pro-drugs of butyric acid. We studied the effects of D1 (O-n-butanoyl-2,3-O-isopropylidene-alpha-D-mannofuranoside), G1 (1-O-n-butanoyl-D,L-xylitol), and F1 (1-O-n-butanoyl 2,3-O-isopropylidene-D,L-xylitol) on the maturation and proliferation of AML cell lines HL 60 and FLG 29.1 and of purified blast cells from 10 cases of de novo acute myeloid leukaemia (AML). AML cell maturation was measured by surface antigen expression, morphology and cytochemistry. Toxicology in mice was also evaluated (DL50 1000 mg/kg). In HL 60 cells G1 and D1 increased the expression of CD15 and CD11a (presenting 62% of promyelo-metamyelocytes), and in 7/10 cases of primary AMLs that of CD11a, CD11b, CD15, and myeloperoxidase. D1, G1 and F1 induced a dose-dependent inhibition of tritiated thymidine uptake. Apoptosis (evaluated by flow cytometry and agarose gel electrophoresis) was induced in AML blasts by D1 and F1 (79% and 94% respectively for HL 60 cells) and, with less effect, by G1 (27%). The persistence of maturative and apoptotic activity in these new pro-drugs of butyric acid, hydrolysed only inside the tumour cell, suggests a possible use in differentiation therapy of myelodysplastic syndromes and AMLs.

Combined analysis of differentiation inhibitory factor nm23-H1 and nm23-H2 as prognostic factors in acute myeloid leukaemia

Differentiation inhibitory factor (nm23 protein) inhibited the induction of the differentiation of various leukaemic cell lines. We previously reported that nm23 genes (H1 and H2) were overexpressed in acute myelogenous leukaemia (AML) and nm23-H1 expression predicted the prognosis of AML, especially AML-M5. To clarify the correlation between French-American-British (FAB) classification and nm23 expression level and to clarify the involvement of nm23-H2 and nm23-H1 in patient survival, we investigated the relative levels of nm23-H1 and -H2 mRNA in 76 AML samples using the reverse transcriptase-polymerase chain reaction. We confirmed that the expression of both nm23-H1 and -H2 genes in AML samples from three different hospitals was significantly higher than that in normal blood cells (P < 0.0005). Overexpression of nm23-H1 was observed in each FAB AML-M1, -M2, -M3, -M4 or -M5 subtype, and the predictive effect of nm23-H1 expression on AML prognosis was shown in FAB AML-M2 and -M5 cases. Although overexpression of nm23-H2 was also found in each FAB subtype, the expression of nm23-H2 in AML-M1 and -M3 cells was not significantly higher than that in normal cells. Among AML subtypes, AML-M3 showed the lowest expression levels of both nm23 genes. To understand the relationship between nm23-H1 and -H2 expression levels, nm23 expression levels for all the AML cases were plotted and divided into four groups (group A, nm23-H1 and -H2 both high; B, both low; C, only nm23-H1 high; D, only nm23-H2 high). A statistically significant correlation between the levels of expression of nm23-H1 and -H2 was observed (r= 0.726). Most AML-M3 cases belonged to group B, but not other types of AML. Analysis of survival probability between the groups showed that group B survived for significantly longer compared with group A. Furthermore, AML-M3 cases survived for significantly longer compared with non-M3 cases in the same group B. These data suggest that low expression levels of both nm23-H1 and -H2 are associated with good prognosis in AML patients.

Docosahexaenoic acid (DHA) alters the structure and composition of membranous vesicles exfoliated from the surface of a murine leukemia cell line

Membrane lipid microdomains are regions of the membrane thought to be functionally important, but which have remained poorly characterized because they have proven to be difficult to isolate. The exfoliation of small membranous vesicles from the cell surface is a continuous and normal activity in many cells. If microdomains are relatively large or stable, they may influence the structure and composition of exfoliated vesicles, which are easy to isolate. We tested the ability of docosahexaenoic acid (DHA), a fatty acid proposed to alter the structure of microdomains, to change the structure and composition of vesicles exfoliated from a murine leukemia cell line. Cells were cultured in normal and DHA-enriched media for 72 h, then washed and given a 15-h exfoliation period. Afterwards, the pooled vesicles and their parent plasma membrane were collected and analyzed. Vesicles and plasma membrane from cells grown in normal culture medium had similar fatty acid compositions, including equal, and low, proportions of DHA, but the vesicles had much more cholesterol and displayed higher anisotropy than the plasma membrane. When cells were grown in DHA-enriched medium, both the plasma membrane and exfoliated vesicles had 10-fold elevated levels of DHA in their phospholipids, with the DHA displacing other polyunsaturates. These cells released vesicles having significantly reduced levels of cholesterol and monoenoic fatty acids than those in normal culture. The anisotropy of these vesicles was also dramatically reduced. These data are consistent with DHA altering the structure and composition of membrane microdomains on the cell surface, and suggest that exfoliated vesicles may prove useful in the further study of membrane microdomains.

Low-dose irradiation induces expression of heat shock protein 70 mRNA and thermo- and radio-resistance in myeloid leukemia cell line

We examined the effects of in vitro low-dose irradiation on myeloid leukemia cells (M1 cells) and found that it enhanced the colony-forming ability (CFA) of M1 cells in semi-solid agar. This enhancement was inhibited by treatment with a protein synthesis inhibitor, cycloheximide and with an RNA synthesis inhibitor, actinomycin D, after irradiation. These findings suggested that low-dose irradiation induced the synthesis of some proteins which were attributed to the enhancement of CFA. Since we expected that one species of these proteins were heat shock proteins (hsps), we attempted to detect the hsp70 family by the Western blotting method and inducible hsp70 mRNA by the RT-PCR method. Low-dose irradiation induced the expression of hsp70 mRNA, whereas the enhancement of hsp70 (an inducible isoform) and hsc70 (a constitutively expressed isoform) expression could not be found. Furthermore, the M1 cells showed thermoresistance 1 h after low-dose pre-irradiation, and also showed radioresistance 4 h after irradiation. This time difference after pre-irradiation might be attributed to the different species of proteins in showing resistance to lethal stress. Therefore, some proteins other than hsp70 were believed to be concerned with the augmentation of CFA and the induction of thermo- and radio-resistance.

Expression of lung resistance protein and correlation with other drug resistance proteins and outcome in myelodysplastic syndromes

The major vault lung resistance protein LRP is a cytoplasmic protein involved in drug resistance, especially in acute myeloid leukemia. We looked for LRP overexpression, using immunocytochemistry with LRP 56 monoclonal antibody, on marrow slides from 41 cases of myelodysplastic syndromes (MDS). LRP overexpression (LRP+) was defined by expression of LRP 56 in at least 20% of marrow blasts. LRP overexpression was seen in 19 (46%) cases. Concordant results between LRP overexpression and P-glycoprotein (PGP) expression were seen in 66% of the cases (p = 0.03), and discordant results (LRP+ and PGP-, or LRP- and PGP+) in 33% of the cases. No correlation was seen between LRP overexpression and FAB type, karyotype, CD34, p53 expression and bcl2 overexpression in blasts. Furthermore, in the 18 cases treated with anthracycline-AraC intensive chemotherapy and the 7 cases treated with low dose AraC, the response rate was not significantly different in LRP+ and LRP- patients. Survival was also similar in LRP+ and LRP- patients. In conclusion, LRP overexpression is probably more frequent in MDS than in de novo AML and, as in AML, is only partially correlated with PGP expression. In our experience, however, LRP was not a prognostic factor for response to chemotherapy and survival in MDS.

Modulation of the activation status of Stat5a during LIF-induced differentiation of M1 myeloid leukemia cells

Treatment of M1 myeloid leukemia cells with leukemia inhibitory factor (LIF) causes activation of transcription factors Stat1, Stat3 and Stat5a (signal transducers and activators of transcription). DNA-binding of Stat proteins was detectable for extended periods of time in LIF-treated M1 cells, which simultaneously underwent terminal differentiation. The relative composition of Stat factors in the protein-DNA complexes changed during time. Whereas Stat3 was activated up to 36 h during treatment with LIF, Stat5a was activated only short-termed. Similarly, high expression of the immediate early gene CIS (cytokine-inducible SH2-containing protein), a known target gene of Stat5 in hematopoietic cells, occurred only during the onset of differentiation. This suggests a role of Stat5a in the early phase of LIF-induced differentiation and growth arrest of M1 cells.

Flow cytometric analysis of protein phosphorylation in the hematopoetic system

Cellular growth and differentiation in blood cells are regulated by the phosphorylation status of growth factor receptors and downstream proteins. Protein kinases and phosphatases balance the homeostasis of protein phosphorylation. Various diseases are associated with alterations in these tightly regulated processes. Aberrations have been proved to be of diagnostic value and might enhance the pathophysiological insight into the origin of the disease. However, quantitation of protein phosphorylation is currently not feasible in a clinical situation. We developed a flow cytometric methodology which enables for direct investigation of protein phosphorylation in cell populations defined by multi-color flow cytometry. This assay does not only overcome drawbacks of traditional methodologies (e.g. Western blotting) but also allows quantitative analyses even in rare cell populations. We accurately examined phosphorylation levels in different cell populations of hematological interest and especially analyzed CD34+ hematopoietic progenitor cells. CD34+ cells in bone marrow and in cord blood contained similar, low levels of phosphotyrosine. Circulating pheripheral blood system cells PBSC in patients exposed to G-CSF for stem cell mobilization exhibited significantly increased levels of phosphotyrosine. In vitro exposure of CD34+ progenitors to growth factors (G-CSF, IL-3, SCF) raised the levels of tyrosine phosphorylation in bone marrow and cord blood. Effects were dose and time dependent. Interestingly, in vivo stimulated CD34+ PBSC could not be further stimulated in vitro. In conclusion, we present a new powerful methodology for analysis of protein phosphorylation in hematological specimens. The method does not only allow for accurate detection of phosphorylation levels in vivo, but also enables for quantitative analysis of growth factor receptor stimulation in vitro and in vivo.

A differential screen for ligand-regulated genes: identification of HoxA10 as a target of vitamin D3 induction in myeloid leukemic cells

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the hormonal ligand for vitamin D3, is a potent inducer of myeloid-leukemic-cell differentiation. Such cells differentiate exclusively into monocytes/macrophages in response to this ligand. Since 1,25(OH)2D3 transduces its hormone signal through the vitamin D3 receptor (VDR), a ligand-modulated transcription factor and member of the nuclear hormone receptor superfamily, we sought to identify direct VDR target genes induced during this differentiation process. To do so, we applied a modified differential screen with a nascent-RNA purification strategy using biases for immediate-early-response genes induced by 1,25(OH)2D3 in the myelomonocytic cell line U937. Using this screen, we had previously identified p21Waf1/Cip1 as a gene transcriptionally induced by 1,25(OH)2D3 and demonstrated that this induction facilitates the differentiation of U937 cells into monocytes/macrophages (24). Here, we describe in detail our differential screen strategy and the identification and isolation of 20 1,25(OH)2D3-inducible genes or unknown cDNAs by means of this screen. One gene newly identified as a target of VDR regulation in myeloid cells is the homeobox HoxA10 gene. HoxA10 protein may act as a general regulator of cell growth, since overexpression of HoxA10 facilitated the differentiation of U937 cells into monocytes/macrophages independent of 1,25(OH)2D3 and acted to strongly inhibit the growth of the breast cancer cell line MCF-7 by arresting these cells in G1.

Characterization and use of an antibody detecting the CBFbeta-SMMHC fusion protein in inv(16)/t(16;16)-associated acute myeloid leukemias

The inv(16)(p13q22) and t(16;16)(p13;q22) cytogenetic abnormalities occur commonly in acute myeloid leukemia (AML), typically associated with French-American-British (FAB) AML-M4Eo subtype. Reverse transcriptase-polymerase chain reaction (RT-PCR) techniques have been recently developed to detect the presence of several variants of the resultant CBFB-MYH11 fusion gene that encodes a CBFbeta-smooth muscle myosin heavy chain (SMMHC) fusion protein. We have now determined the clinical use of a polyclonal antibody [anti-inv(16) Ab] directed against a junctional epitope of the most common type of CBFbeta-SMMHC fusion protein (type A), which is present in 90% of inv(16)/t(16;16) AML cases. Using flow cytometry, reproducible methods were developed for detection of CBFbeta-SMMHC proteins in permeabilized cells; flow cytometric results were then correlated with cytogenetics and RT-PCR detection methods. In an analysis of 42 leukemia cases with various cytogenetic abnormalities and several normal controls, the anti-inv(16) Ab specifically detected all 23 cases that were cytogenetically positive for inv(16) or t(16;16), including a single AML case that was RT-PCR-negative. In addition to detecting all type A fusions, the anti-inv(16) Ab also unexpectedly identified the type C and type D CBFbeta-SMMHC fusion proteins. Molecular characterization of one RT-PCR-positive and Ab-positive t(16;16) case with a non-type A product showed a novel previously unreported CBFB-MYH11 fusion (CBFB nt 455-MYH11 nt 1893). Flow cytometric results were analyzed using the Kolmogorov-Smirnov statistic D-value and the median value for positive samples was 0.65 (range, 0.35 to 0.77) versus 0.07 (range, -0.21 to 0.18) in the negative group (P < .0001). The overall concordance between cytogenetics and RT-PCR was 97%, whereas the concordance between flow cytometry and cytogenetics was 100%. Thus, using the anti-inv(16) Ab, all cytogenetically positive and RT-PCR-positive AML cases with inv(16) or t(16;16) could be rapidly identified. This study demonstrates the use of this antibody as an investigational tool in inv(16)/t(16;16) AML and suggests that the development of such reagents may have potential clinical diagnostic use.

Evaluation by multivariate analysis of the differentiation inhibitory factor nm23 as a prognostic factor in acute myelogenous leukemia and application to other hematologic malignancies

The differentiation inhibitory factor nm23 can inhibit the differentiation of murine and human myeloid leukemia cells. We recently reported that nm23 genes were overexpressed in acute myelogenous leukemia (AML), and a higher level of nm23-H1 expression was correlated with a poor prognosis in AML, especially in AML-M5 (acute monocytic leukemia). To evaluate the importance of nm23 expression as a prognostic factor in AML, we compared it with other putative prognostic factors in AML. An analysis of the correlation between nm23 expression and the clinical parameters of 110 patients with AML demonstrated that increased nm23-H1 mRNA levels were associated with resistance to initial chemotherapy and with reduced overall survival. Multivariate analysis using Cox's proportional hazard model also showed that elevated nm23-H1 mRNA levels significantly contributed to the prognosis of patients with AML. Especially in AML-M5, nm23-H1 status was the most important prognostic factor. Furthermore, to determine whether we can apply the results observed in AML to other hematologic malignancies, we investigated the relative levels of nm23-H1 and nm23-H2 transcripts in 149 patients with hematologic neoplasms, including 110 with de novo AML, 9 with de novo acute lymphoblastic leukemia, 14 with myelodysplastic syndrome, 16 with chronic myelogenous leukemia (CML), and 5 normal subjects by the reverse transcriptase-polymerase chain reaction. Expression of nm23-H1 was significantly higher in all the hematologic neoplasms, except CML in chronic phase, than in normal blood cells. nm23 may have a prognostic effect in these hematologic malignancies as well as in AML.

Accelerated entry into S phase associated with up-regulation of cyclin D1 as a mechanism for granulocyte colony-stimulating factor (G-CSF)-induced apoptosis of murine myeloid leukemia cells

We previously reported that injection of recombinant granulocyte colony-stimulating factor (G-CSF) suppressed the development of leukemia in mice transplanted with C2M-A5 (C2M) myeloid leukemia cells and that the anti-leukemic effect of G-CSF was ascribed to the induction of apoptosis of C2M cells. These observations make a striking contrast with other previous reports on the biological activities of G-CSF. In the present study, in order to further clarify the G-CSF-induced apoptosis of C2M cells, we studied the effects of G-CSF on the cell cycle as well as the molecular events involving D-type cyclines and their cyclin-dependent kinases (cdk) in G-CSF-treated C2M cells. Cell cycle analysis revealed that G-CSF treatment of C2M cells resulted in accelerated entry from the first gap (G1) phase into the DNA synthesis (S) phase. Western blotting disclosed that G-CSF treatment resulted in down-regulation of cyclin D2 and cdk2 and up-regulation of cyclin D1 and cdk4. The reciprocal relationship between the up-regulation of cyclin D1 and down-regulation of cyclin D2 was closely associated with accelerated entry into S phase and subsequent apoptosis of C2M cells. These results suggest that G-CSF-induced apoptosis of C2M cells might be ascribed to imbalanced cell cycle progression due to deregulated expression of D-type cyclins and their cdks.

The AML1/ETO(MTG8) and AML1/Evi-1 leukemia-associated chimeric oncoproteins accumulate PEBP2beta(CBFbeta) in the nucleus more efficiently than wild-type AML1

AML1, a gene on chromosome 21 encoding a transcription factor, is disrupted in the (8;21)(q22;q22) and (3;21)(q26;q22) chromosomal translocations associated with myelogenous leukemias; as a result, chimeric proteins AML1/ETO(MTG8) and AML1/Evi-1 are generated, respectively. To clarify the roles of AML1/ETO(MTG8) and AML1/Evi-1 in leukemogenesis, we investigated subcellular localization of these chimeric proteins by immunofluorescence labeling and subcellular fractionation of COS-7 cells that express these chimeric proteins. AML1/ETO(MTG8) and AML1/Evi-1 are nuclear proteins, as is wild-type AML1. Polyomavirus enhancer binding protein (PEBP)2beta(core binding factor [CBF]beta), a heterodimerizing partner of AML1 that is located mainly in the cytoplasm, was translocated into the nucleus with dependence on the runt domain of AML1/ETO(MTG8) or AML1/Evi-1 when coexpressed with these chimeric proteins. When a comparable amount of wild-type AML1 or the chimeric proteins was coexpressed with PEBP2beta(CBFbeta), more of the cells expressing the chimeric proteins showed the nuclear accumulation of PEBP2beta(CBFbeta), as compared with the cells expressing wild-type AML1. We also showed that the chimeric proteins associate with PEBP2beta(CBFbeta) more effectively than wild-type AML1. These data suggest that the chimeric proteins are able to accumulate PEBP2beta(CBFbeta) in the nucleus more efficiently than wild-type AML1, probably because of the higher affinities of the chimeric proteins for PEBP2beta(CBFbeta) than that of wild-type AML1. These effects of the chimeric proteins on the cellular distribution of PEBP2beta(CBFbeta) possibly cause the dominant negative properties of the chimeric proteins over wild-type AML1 and account for one of the mechanisms through which these chimeric proteins contribute to leukemogenesis.

Transcriptional regulation of urokinase-type plasminogen activator receptor by cyclic AMP in PL-21 human myeloid leukemia cells: comparison with the regulation by phorbol myristate acetate

We investigated the effect of dibutyryl cyclic AMP (Bt2-cAMP) on urokinase-type plasminogen activator receptor (uPAR) expression in human PL-21 myeloid leukemia cells and compared it with the effect of phorbol myristate acetate (PMA). Flow cytometric analysis clearly demonstrated that Bt2-cAMP and PMA both induced the cell surface expression of uPAR. Northern analysis and nuclear run-on assay revealed that cAMP and PMA activated the uPAR gene transcription and both additively increased the uPAR mRNA level. However, actinomycin-D decay experiment showed that PMA, but not cAMP, prolonged the uPAR mRNA half-life. Furthermore, inhibition of the ongoing protein synthesis with cycloheximide abrogated completely the PMA-induced uPAR mRNA accumulation but only partially the induction by PMA plus cAMP, whereas the induction by cAMP alone was rather amplified, indicating that the de novo protein synthesis is necessary in the induction by PMA but not in the induction by cAMP and that the cAMP pathway may be dominant in uPAR gene expression in the PL-21 cells as compared to the PMA pathway. These results suggest that cAMP induces the uPAR expression exclusively through activating the gene transcription in which a preexisting transcriptional factor may be involved, whereas PMA transcriptionally and posttranscriptionally regulates the uPAR gene expression.

MUC18, a member of the immunoglobulin superfamily, is expressed on bone marrow fibroblasts and a subset of hematological malignancies

Despite the importance of bone marrow stromal cells in hemopoiesis, the profile of surface molecule expression is relatively poorly understood. Mice were immunized with cultured human bone marrow stromal cells in order to raise monoclonal antibodies to novel cell surface molecules, which might be involved in interactions with hemopoietic cells. Three antibodies, WM85, CC9 and EB4 were produced, and were found to identify a 100-110 kDa antigen on bone marrow fibroblasts. Molecular cloning revealed the molecule to be MUC18 (CD146), a member of the immunoglobulin superfamily, previously described as a marker of metastatic melanoma. In addition to the expected expression on melanoma cell lines and endothelial cells, a number of human leukemic cell lines were found to express MUC18, including all six T leukemia lines tested, one of five B lineage lines and one of four myeloid lines. Analysis of bone marrow samples from patients revealed positivity in 20% of B lineage ALL (n = 20), one of three T-ALL, 15% of AML (n = 13) and 43% of various B lymphoproliferative disorders (n = 7). No apparent reactivity was observed with mononuclear cells from normal peripheral blood or bone marrow, including candidate hemopoietic stem cells characterized by their expression of the CD34 antigen. However, positive selection of bone marrow mononuclear cells labeled with MUC18 antibody revealed a rare subpopulation (<1%) containing more than 90% of the stromal precursors identified in fibroblast colony-forming assays. The structure and tissue distribution of MUC18 suggest a functional role in regulation of hemopoiesis.

Detection of bcr/abl fusion transcripts by semiquantitative multiplex RT-PCR combined with a colormetric assay in Ph positive leukemia

We studied the feasibility of the clinical application of a new bcr/abl analysis system, C-TRAK t(9;22), consisting of a multiplex RT-PCR and a colormetric assay. With this system, bcr/abl transcripts could be detected in all of 24 cytogenetic Philadelphia chromosome (Ph) positive leukemia patients and in none of eight Ph negative patients. Multiple bcr/abl transcripts could be detected in three of the 24 Ph positive patients, the fusion of bcr exon 1 to abl exon 2 (e1a2 junction) dominated that of bcr exon 13 to abl exon 2 (b2a2 junction) in two cases and that of bcr exon 14 to abl exon 2 (b3a2 junction) and b2a2 dominated e1a2 in one case. This system was sensitive enough to be able to detect even one bcr/abl transcript-producing cell in 50000 bcr/abl negative background cells, thus making it suitable for semiquantitative evaluation. Minimal residual disease (MRD) was monitored in one Ph positive leukemia patient who underwent allogenic bone marrow transplantation (allo-BMT). After allo-BMT, a weak positivity of the bcr/abl transcript continued with no clinical relapse; this result was consistent with that of a conventional nested PCR assay using ethidium bromide staining. Including all the procedures for RNA extraction, it took only about 10 h to detect the bcr/abl transcripts. Our findings indicate that this bcr/abl analysis system provides a quick and sensitive method for screening bcr/abl transcripts and possibly for monitoring MRD in Ph positive leukemia patients.

Detection of unique ALL1 (MLL) fusion transcripts in normal human bone marrow and blood: distinct origin of normal versus leukemic ALL1 fusion transcripts

The partial tandem duplication (PTD) of ALL1 (MLL) is one of the more common molecular abnormalities in adult de novo acute myeloid leukemia (AML) and carries a poor prognosis. The PTD of ALL1 is identified in leukemic blasts at the genomic level by ALL1 rearrangement upon Southern analysis and by genomic fusion following DNA PCR. The genomic defect encodes for a unique fusion transcript that is readily detected by reverse transcription-PCR (RT-PCR). To determine if the ALL1 fusion transcript is specific for leukemic blasts or instead can be found with any frequency in normal cells, we analyzed 52 bone marrow and 8 peripheral blood samples from 60 normal donors by nested RT-PCR. Ten of 60 samples (16%; 7 bone marrow and 3 peripheral blood) contained a unique transcript showing a fusion of two ALL1 exons that was consistent with the PTD of ALL1. However, a corresponding genomic rearrangement or a unique genomic fusion of ALL1 could not be demonstrated by Southern analysis or DNA PCR, respectively. Marked differences were observed in the size and sequence of the ALL1 fusion transcripts detected in normal donors, compared to those detected in leukemic patients with a PTD of ALL1. Moreover, although the ALL1 fusion transcripts seen in AML always maintain the open reading frame, the open reading frame was preserved in only 5 of 10 fusion transcripts from normal donors. Finally, in contrast to leukemic blasts with the PTD of ALL1, the fusion transcripts in normal cells could not be detected in the poly(A)+ RNA fraction by RT-PCR. In summary, the origin and the composition of the ALL1 fusion transcripts found in normal cells appear to be distinct from those found in the leukemic cells. The data accumulated thus far suggest that the ALL1 fusion product detected in normal tissue results from the process of differential mRNA splicing rather than true ALL1 gene rearrangement. These findings also suggest caution in the use of RT-PCR for detection of minimal residual disease in AML patients with the PTD of ALL1.

Renin in acute myeloid leukaemia blasts

Hypokalaemia is a clinical phenomenon in patients with acute myeloid leukaemia (AML) to which activation of the renin-angiotensin system (RAS) may contribute. Recently monocytes were found to express renin, the key initializing enzyme of the RAS. By RT/PCR, transcripts for renin were detected in four of 18 bone marrow samples from patients with AML. Three leukaemic cell lines, isolated monocytes, bone marrow stromal cells and 25 peripheral blood and 24 bone marrow samples of normal controls were negative for renin transcripts. In view of the importance of local RAS in other tissues, the expression of renin in the bone marrow of AML patients warrants further investigation.

Quantitative expression of thrombopoietin receptor on leukaemia cells from patients with acute myeloid leukaemia and acute lymphoblastic leukaemia

Using a non-isotopic ligand binding assay, we quantitatively examined the amount of human thrombopoietin (TPO) receptor (TPO-R) on leukaemia cells from 128 patients with acute myeloid leukaemia (AML) or acute lymphoblastic leukaemia (ALL). The TPO-R was expressed in 53 (47%) of 114 AML cases, and an in vitro treatment with TPO led to proliferation (stimulation index >1 5) of leukaemia cells in 13 (20%) of 66 AML cases examined. The TPO levels had no relation to the FAB classification except for FAB-M7 AML. All five FAB-M7 cases expressed TPO-R, and one of three FAB-M7 examined showed in vitro proliferative response to TPO. Although there was no significant correlation (r = 0.3125) between the amount of TPO-R and the proliferative response, all of the AML cases which showed the in vitro response had TPO-R expression. There was no relationship between TPO-R amount and CD phenotypes, or the amount of granulocyte-colony stimulating factor (G-CSF) receptor. TPO-R was also expressed in two (14%) of 14 cases of ALL, and only these two cases had in vitro proliferative response to TPO. One had only lymphoid antigens, and the other had both lymphoid and myeloid antigens. Our results suggest that some leukaemia cells express functionally active TPO-R.

Possible association between adult T-cell leukemia/lymphoma and acute myeloid leukemia

BACKGROUND

To the authors' knowledge, an association between adult T-cell leukemia/lymphoma (ATL) and acute myeloid leukemia (AML) has been reported only in four patients. The authors identified five additional patients with both neoplasms.

METHODS

A review of the clinical records of patients with AML, ATL, or lymphoid neoplasms other than ATL diagnosed between 1986 and 1995 was performed. Cytokine levels were assayed in selected patients. The authors searched for reports from other institutions using MEDLINE and the proceedings of two Japanese hematology societies.

RESULTS

ATL was diagnosed in 134 patients, whereas 180 had AML. Five patients with both neoplasms were identified (3.7% of ATL patients and 2.8% of AML patients). In seven of the nine patients (including four patients in the literature) with ATL and AML, the ATL was diagnosed prior to the AML, whereas in the remaining two patients both neoplasms were diagnosed simultaneously. Six of the nine cases were therapy-related (t)-AML, which developed after chemotherapy for ATL. Monoclonal integration of proviral human T-lymphotropic virus type 1 was detected in ATL cells but not in AML cells in the six patients examined. The plasma levels of macrophage colony-stimulating factor (M-CSF), granulocyte-colony stimulating factor, and granulocyte-macrophage-colony stimulating factor (GM-CSF) were elevated in 3, 1, and 1, respectively, of the 4 patients examined at AML onset who had active ATL. In one case, the levels of several cytokines, including GM-CSF and M-CSF, in the supernatant fluid of short term cultured ATL cells were elevated. Three patients with de novo ATL and AML received remission induction therapy, and two achieved a complete remission (CR) of both diseases. Among the four patients who received chemotherapy for t-AML, two achieved CR.

CONCLUSIONS

ATL patients also can develop AML, irrespective of treatment with chemotherapy for ATL. This association does not indicate exclusive chemoresistance of both neoplasms. Cytokines produced by ATL cells may support the growth of AML cells.

Acute myeloid leukemia cells with low P-glycoprotein expression and high rhodamine 123 efflux capacity display high clonogenicity

This study was designed to correlate the clonogenic capacity of acute myeloid leukemia (AML) cells with P-glycoprotein (P-gp) expression level and P-gp-mediated efflux capacity. Fifty AML cell samples were tested for P-gp expression using MRK16 monoclonal antibody and flow cytometry. Among them, 12 samples were selected for sorting experiments according to the following two criteria: their clonogenic capacity in methylcellulose in the presence of 5637 conditioned medium, and the heterogeneity of P-gp distribution in leukemic cells. For each of these 12 samples, leukemic cells which displayed the highest P-gp expression level (P-gp++) and P-gp- leukemic cells were sorted after MRK16 staining and seeded into methylcellulose for primary clonogenic assay. In each case, the number of CFU-L in the P-gp fraction was significantly higher than that of the P-gp++ fraction (P < 0.01); the median number of CFU-L for 10(5) seeded cells being 147 (range 3-1855) and 495 (range 60-4100) for P-gp++ and P-gp- populations, respectively. Furthermore, in order to correlate clonogenic capacity and P-gp function, AML cells were stained with rhodamine 123 (Rh 123), washed and then sorted after 4 h incubation at 37 degrees C in Rh 123-free media on the basis of their residual fluorescence intensity before plating. For each of six samples, we found that the number of CFU-L in the AML cell fraction which displayed the most efficient Rh 123 efflux capacity (Rh 123dull) was significantly higher compared to that of the AML cell fraction which displayed high residual fluorescence signal (Rh 123bright) (P = 0.05); the median number of CFU-L for 10(5) seeded cells being 1025 (range 250-2240) and 296 (range 11-838) for Rh 123dull and Rh 123bright populations, respectively. Altogether this study suggests that, for an individual AML cell population, the clonogenic fraction is preferentially recruited in AML cells which display low P-gp expression and high P-gp-mediated efflux capacity.

Differences in CD14 and alpha-naphthyl acetate esterase positivity and relation to prognosis in AML

Alpha-naphthyl acetate esterase (ANAE) and CD14 expression, used for determination of monocytic cells, were compared and related to prognosis in 65 AML patients. Bone marrow aspiration material from AML patients has been used for the cytochemistry as well as flow cytometry. All non-erythroid cells have been included in the evaluation in both methods. 17/65 cases showed at least 15% difference between the proportion CD14 and ANAE positive cells. Cases with 20% or more CD14 positivity had poorer prognosis. For FAB classes M0-M3, presence of 10% or more CD14 was negative for overall survival (P = 0.01). ANAE did not show significant prognostic influence.

Lack of interferon consensus sequence binding protein (ICSBP) transcripts in human myeloid leukemias

Interferon consensus sequence binding protein (ICSBP) was first identified as a transcription factor of the interferon (IFN) regulatory factor family (IRF) which regulates expression of IFN-dependent genes by binding to DNA at specific sites, IFN-stimulated responsive elements. Analysis of ICSBP-deficient mice showed hematologic alterations similar to chronic myelogenous leukemia (CML) in humans and suggested a novel role for ICSBP in regulating proliferation and differentiation of hematopoietic progenitor cells. Here we show that ICSBP-mRNA expression is impaired in human myeloid leukemias: 27 of 34 CML patients (79%) and 21 of 32 patients with acute myeloid leukemia (AML) (66%) showed very low or absent transcript numbers of ICSBP. In contrast, only 2 of 33 normal volunteers (6%) showed low transcription of ICSBP (P < . 0001 both for CML and AML values). The lack of expression was not associated with lack of lymphatic cells, which normally have been shown to express ICSBP at the highest level. More detailed analysis showed an absence of ICSBP-mRNA also in sorted B cells derived from CML patients. To analyze whether ICSBP may be induced in leukemic cells, ex vivo experiments using a known inducer of ICSBP, IFN-gamma, were performed. Ex vivo treatment of primary CML cells using IFN-gamma resulted in induction of ICSBP transcripts. Furthermore, samples of CML patients during IFN-alpha treatment were analyzed. In 11 of 12 CML patients ICSBP-mRNA was inducible upon in vivo treatment with IFN-alpha, but decreased with progression of CML. Stable transfection of K-562 cell line with ICSBP led to no difference in bcr-abl expression in vitro, although two patients showed an inverse correlation between bcr-abl and ICSBP in vivo. These data suggest that lack of ICSBP may have an important role also in human myeloid leukemogenesis.

Adult biphenotypic acute leukaemia: an entity with poor prognosis which is related to unfavourable cytogenetics and P-glycoprotein over-expression

Biphenotypic acute leukaemia (BAL) patients represented 8% of the 287 de novo consecutive adult acute leukaemias (23 BAL, 230 acute myeloid leukaemia (AML) and 34 acute lymphoblastic leukaemia (ALL)) referred to our department during the last 4-year period. Of these 23 BAL patients, 14 patients showed myeloid morphology and nine cases lymphoid morphology according to FAB criteria. There were no differences between lymphoid and myeloid BAL according to clinical and biological presentation and treatment outcome. We confirm the poor prognosis of BAL when compared to AML or ALL seen during the same period of time, in terms of complete remission (47%, 62% and 82% respectively, BAL v AML, NS and BAL v ALL, P = 0.006) and 4-year overall survival (8.1%, 25.8% and 23.8% respectively, BAL v AML, P = 0.05 and BAL v ALL, P = 0.003). Comparing adult BAL patients with AML patients, we found an increase in poor prognostic factors: CD34+ phenotype (82% v 60% respectively, P = 0.03), unfavourable karyotype (60% v 20%, P < 0.0001) and Pgp over-expression by RT-PCR (0.705 v 0.107, P < 0.0001) and flow cytometry (0.824 v 0.391, P = 0.0001). MRP and LRP were not found to be poor prognostic factors. Comparing BAL patients with ALL patients, we found also an increase in poor prognostic factors: age (51 v 39, P = 0.003) and CD34+ phenotype (82% v 50%, P = 0.02). We conclude that BAL patients need a more aggressive treatment procedure, including high-dose AraC or the use of Pgp modulators for first-line therapy.