Tryptase a novel biochemical marker of acute myeloid leukemia

Despite maturation arrest, blast cells in acute myeloid leukemia (AML) are often capable of expressing lineage-restricted (granulomonocytic or myelomastocytic) differentiation antigens. Tryptases are lineage-associated serine proteases primarily expressed in mast cells, and less abundantly in blood basophils. We have recently shown that myeloblasts in a group of patients with AML (approximately 40%) produce significant amounts of tryptase(s). In these patients, serum tryptase levels are elevated (> 15 ng/ml) and reflect the total burden of leukemic cells. In most cases, myeloblasts express alpha-tryptase mRNA in excess over beta-tryptase mRNA, and secrete the respective protein (= pro-alpha-tryptase) in a constitutive manner. It was also found that these AML blasts frequentlyco-express tryptase with additional mast cell lineage- and/or basophil-related differentiation antigens including KIT (CD117), histamine, and 2D7. We hypothesize that tryptase-positive AMLs arise from a leukemic progenitor that exhibits a limited potential to differentiate into mast cells and/or basophils.     

CS-1, a novel c-kithi+ acute myeloid leukemia cell line with dendritic cell differentiation capacity and absent immunogenicity

Complex cytogenetic abnormalities confer dismal prognoses in myeloid malignancies. Even bone marrow transplantation from siblings or matched unrelated donors offer minimal chances for cure, suggesting that these cases are not only refractory to chemotherapy but also resist the graft-vs.-leukemia effect. We herein describe the first permanent, factor-independent c-kit(hi+) cell line CS-1 derived from an unrelated donor stem cell transplanted patient with relapsed acute myeloid leukemia (AML)-M5a of high-risk karyotype [monosomy 7, t(2;11)(q31;p13), t(10;12)(q24;q24)]. Having the same karyotype, CS-1 exhibits an autonomous growth pattern and responds to stem cell factor (SCF). CS-1 did not induce T cell activation in mixed-lymphocyte-tumor-cultures (MLTCs) and, when used as third party stimulators, decreased T cell proliferation in mixed-lymphocyte reactions (MLRs). Cytokines added exogenously or secreted from bystander T cells caused CS-1 to differentiate into dendritic cells (DCs). CS-1-derived DCs, in contrast to DCs originating from non-malignant CD34(+) progenitor cells, had virtually no T cell stimulatory effect, indicating that CS-1 is both immunosuppressive and poorly immunogenic. These properties may partially be due to the detected downregulation of costimulatory molecules and appear to involve a soluble factor. CS-1 cells injected subcutaneously (s.c.) to non-obese diabetes/severe combined immunodeficient (NOD/SCID) mice produced solid tumors, disseminating into bone marrow and spleen. The data show that transforming AML blasts with high-risk karyotype into DCs is insufficient to restore their immunogenicity and that the CS-1 cell line is useful to identify tumor-related immunosuppressive mechanisms in vitro and in vivo.     

Glycophorin a as a cell surface marker of early erythroid differentiation in acute leukemia

We show here that the leukemic blast cells from three patients of a total of 15 subsequently diagnosed as having acute leukemia express on their surface the major red cell sialoglycoprotein, glycophorin A (GP-A). This was demonstrated (1) by indirect immunofluorescence using rabbit anti GP-A antiserum and (2) by immune precipitation of GP-A from surface radiolabelled leukemic cells. Since GP-A is exclusively present on erythroid cells and their precursors, these findings indicate that a higher proportion of the blast leukemias than previously recognized show features of early erythroid differentiation.     

Cell surface receptor-targeted therapy of acute myeloid leukemia: a review

Combination chemotherapy produces remissions in patients with acute myeloid leukemia (AML). However, the majority of patients ultimately relapse and die with cytotoxic drug resistant blasts. Novel agents which circumvent resistance are needed. One such class are AML-cell surface targeted proteins. These genetically engineered polypeptides are hybrid molecules composed of two moieties--a haptophore which triggers AML cell binding and a toxophore which kills the cell. The haptophore or ligand portion consists of a monoclonal antibody or antibody fragment or a cytokine. These peptides react with cell surface receptors or antigens on AML cells. The haptophore is genetically or chemically linked to the toxophore. The toxophore may consist of an antibody Fc domain which triggers antibody-dependent cell cytotoxicity, a DNA-damaging cytotoxic drug, a radionuclide or a protein synthesis-inactivating peptide toxin. The toxophore may provide a cell death signal that overcomes standard resistance phenotypes. Further, the targeting provided by the haptophore may reduce normal tissue toxicities. This review describes some of the properties of the cell surface molecular targets, the reactive haptophores and toxophores and how these functional peptides have been optimally combined to kill leukemic blasts in patients with AML.     

Human myeloid inhibitory C‐lectin: a highly specific and stable acute myeloid leukemia marker

The prognosis of acute myeloid leukemia (AML) is poor because of relapses occurring on conventional chemotherapy. The distinction between leukemic and normal stem cells relies on the expression of antigen combinations defining leukemia‐associated immunophenotypes (LAIPs), which are absent or extremely infrequent in normal bone marrow. However, LAIPs are very different from patient to patient and are not necessarily stable over the course of the disease. Accordingly, we addressed the applicability of human myeloid inhibitory C‐lectin (hMICL) by flow cytometry as a specific leukemic myeloid stem cell marker for the diagnosis of AML in CD34⁺ and CD34^? cases and evaluated the stability of hMICL during the course of the disease. hMICL expression was assessed in 78 bone marrow aspirate specimens obtained from AML patients at diagnosis (n = 40), complete remission (CR) (n = 28), and relapse (n = 10). AML patients at diagnosis were compared to 20 newly diagnosed acute lymphoblastic leukemia (ALL) patients and 20 healthy controls. hMICL was reevaluated in CR and relapse specimens. hMICL was expressed in 100% AML patients at diagnosis (mean ± standard deviation [SD], 60.3 ± 19.9%), both CD34⁺ and CD34^?, but not in ALL (mean ± SD, 3.3 ± 1.9%) or healthy controls (mean ± SD, 3.4 ± 2.6%) (P  < .001). hMICL median fluorescence intensity ratio was higher in AML (mean ± SD, 15.9 ± 11.7) compared to ALL (mean ± SD, 4.5 ± 1.4) and healthy controls (mean ± SD, 4.4 ± 1.6) (P  < .001). hMICL was expressed in all studied AML morphologic subtypes. Preserved stable expression of hMICL was found in CR and relapse specimens with no antigen loss. hMICL is a robust pan‐AML‐associated antigen with excellent diagnostic impact, extreme specificity to AML blasts, and stability throughout the course of the disease. hMICL could be incorporated into the routine flow cytometry setting within the initial diagnostic work‐up and follow‐up of AML.     

TWIST-1 promotes cell growth,drug resistance and progenitor clonogenic capacities in myeloid leukemia and is a novel poor prognostic factor in acute myeloid leukemia

Alterations of TWIST-1 expression are often seen in solid tumors and contribute to tumorigenesis and cancer progression. However, studies concerning its pathogenic role in leukemia are scarce. Our study shows that TWIST-1 is overexpressed in bone marrow mononuclear cells of patients with acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Gain-of-function and loss-of-function analyses demonstrate that TWIST-1 promotes cell growth, colony formation and drug resistance of AML and CML cell lines. Furthermore, TWIST-1 is aberrantly highly expressed in CD34⁺CD38⁻ leukemia stem cell candidates and its expression declines with differentiation. Down-modulation of TWIST-1 in myeloid leukemia CD34⁺ cells impairs their colony-forming capacity. Mechanistically, c-MPL, which is highly expressed in myeloid leukemia cells and associated with poor prognosis, is identified as a TWIST-1 coexpressed gene in myeloid leukemia patients and partially contributes to TWIST-1-mediated leukemogenic effects. Moreover, patients with higher TWIST-1 expression have shorter overall and event-free survival (OS and EFS) in AML. Multivariate analysis further demonstrates that TWIST-1 overexpression is a novel independent unfavourable predictor for both OS and EFS in AML. These data highlight TWIST-1 as a new candidate gene contributing to leukemogenesis of myeloid leukemia, and propose possible new avenues for improving risk and treatment stratification in AML.     

Spontaneous remission of acute myeloid leukemia associated with GnRH agonist treatment

Spontaneous remission of acute myeloid leukemia (AML) in adults is a rare but well documented phenomenon. This study reports on a 64-year-old male patient with acute myelogenous leukemia (AML-M4, according to the French-American-British classification) that was developed on a background of chronic myelomonocytic leukemia (CMML) and then underwent remission after treatment with the gonadotropin-releasing hormone agonist (GnRH agonist) triptorelin for presumed prostate cancer. Remission persisted for at least 4 years before the patient was lost to follow-up. To the author' knowledge, this is the first report of remission in an AML-M4 case associated with hormone manipulation. Possible mechanisms of this phenomenon are discussed.     

Multidrug resistance-1 gene polymorphisms associated with treatment outcomes in de novo acute myeloid leukemia

Multidrug resistance-1 (MDR-1) gene single nucleotide polymorphisms (SNPs) have been identified as associated with the treatment outcomes of acute myeloid leukemia (AML) in Caucasians; yet, similar evidence is lacking for Asian populations. A total of 101 AML patients were enrolled in the current study. Two MDR1 SNPs (C3435T and G2677T/A) were analyzed with PCR/RFLP assay. As regards C3435T polymorphism, C/C genotype was significantly correlated with lower functional P-glycoprotein (P-gp) activity in leukemic blasts (7.5%) compared with C/T (10.7%) or T/T genotype (19.9%, p = 0.029). In genotypic analyses, C/C at -3435 (p = 0.05) and G/G at -2677 (p = 0.04) were strongly associated with a higher probability of complete remission (CR). In addition, the 3-year event-free survival (EFS) was higher in G/G genotype at -2677 (60.6%) than nonG/G (21.9%; p = 0.0241), in C/C at -3435 was higher than nonC/C genotype (p = 0.0139), and was higher in GC haplotype homozygote (58.2%) than nonGC homozygote (22.6%; p = 0.0427). In a multivariate analysis, the group without GC haplotype showed worse EFS (p = 0.030), with unfavorable cytogenetic risk (p = 0.008). However, no differences were noted in overall survival according to the MDR1 SNPs (p = 0.491 for C3435T and p = 0.955 for G2677T/A).     

Telomerase activity is prognostic in pediatric patients with acute myeloid leukemia: comparison with adult acute myeloid leukemia

BACKGROUND: Significantly elevated telomerase activity (TA) has been found in samples from patients with almost all malignant hematologic diseases. The impact of elevated TA on the course of pediatric patients with acute myeloid leukemia (P-AML) is unknown. METHODS: Using a modified polymerase chain reaction-based, telomeric repeat-amplification protocol assay, the authors measured TA in bone marrow samples from 40 patients with P-AML and, for comparison, in 65 adult patients with AML (A-AML), excluding patients with French-American-British M3 disease. The results were correlated with patient characteristics and survival. RESULTS: TA in patients with P-AML was significantly lower compared with TA in patients with A-AML (P = 0.005). Patients who had P-AML with low TA had a projected 5-year survival rate of 88%, whereas patients who had P-AML with high TA had a projected 5-year survival rate of 43% (P = 0.009). Conversely, patients who had A-AML with very high TA (upper quartile) had significantly longer survival compared with patients who had A-AML with lower TA (P = 0.03). There was no correlation between complete remission rate or disease free survival and TA in P-AML or A-AML. In the A-AML group, when patients were separated by cytogenetic findings (poor prognosis vs. others), it was found that TA was significantly lower in patients with a poor prognosis, but the prognostic value of TA was not independent of cytogenetic status. CONCLUSIONS: The current results suggest, that for patients with P-AML, bone marrow TA is a highly significant prognostic factor.     

Myelodysplasia terminating in acute myeloid leukemia in a hairy cell leukemia patient treated with 2-deoxycoformycin

Purine analogs are effective in the treatment of several chronic lymphoproliferative disorders (CLPD) including hairy cell leukemia (HCL). To date, little evidence exists that these drugs are oncogenic. We report a case of HCL in a 66-year-old male treated with 2-deoxycoformycin. Just over 1 year following completion of his treatment, falling platelet and white cell counts were associated with the development of dysplastic features in his bone marrow and a rising blast cell count, culminating in the development of acute myeloid leukemia (AML). To the best of our knowledge only two previous cases of AML have been linked to treatment of HCL with purine analogs, both with 2-chlorodeoxyadenosine. We emphasize the need for long term follow up of patients treated with purine analogs and suggest that even those who are apparently cured be monitored periodically.     

Characterization of a monoclonal antibody specific for a novel primate cell surface marker with distinct biochemical properties on human erythroleukemia and myeloid cell lines

A hybridoma, CSC-1, which secretes monoclonal antibody (MAb) specific for a cell surface molecule on African green monkey kidney cell line, BGMK, was isolated and characterized. The cell surface molecule recognized by CSC-1 is widely expressed on a variety of human cell lines. Among the hematopoietic cell lines examined, the CSC-1 marker seems to be preferentially expressed by lymphoid cell lines (e.g., Raji, CEM-SS, Jurkat, and MOLT-3). Although CSC-1 also recognizes some uncommitted myeloid and erythroleukemia cell lines (e.g., U-937 and K562), the CSC-1 marker expression on these cell lines is subjected to PMA-induced down-regulation. In addition, the PMA-induced cell surface down-regulation of the CSC-1 marker required more than 24 h. Proteolytic analysis shows that the CSC-1 marker can be categorized into proteinase K-resistant and-sensitive phenotypes. Furthermore, the CSC-1 marker exhibits a slow cell surface turnover rate after proteinase K treatment. Our data suggest that the CSC-1 cell surface molecule might be useful as a megakaryocytic or monocytic differentiation marker.