Deregulated expression of Kruppel-like factors in acute myeloid leukemia.

The known participation of Kruppel-like transcription factors (KLF) in cellular differentiation prompted us to investigate their expression in acute myeloid leukemia (AML) blast cells that are typically blocked in their differentiation. We determined the expression patterns of KLFs with a putative role in myeloid differentiation in a large cohort of primary AML patient samples, CD34+ progenitor cells and granulocytes from healthy donors. We found that KLF2, KLF3, KLF5 and KLF6 are significantly lower expressed in AML blast and CD34+ progenitor cells as compared to normal granulocytes. Moreover, we found markedly increased KLF levels in acute promyelocytic leukemia patients who received oral ATRA. Accordingly, we observed a strong induction of KLF5/6 upon ATRA-treatment in NB4 and HT93 APL but not in ATRA-resistant NB4-R cells. Lastly, knocking down KLF5 or KLF6 in NB4 cells significantly attenuated neutrophil differentiation. In conclusion, we found a significant repression of KLF transcription factors in primary AML samples as compared to mature neutrophils and further show that KLF5 and KLF6 are functionally involved in neutrophil differentiation of APL cells.

Epigallocatechin-3-gallate induces cell death in acute myeloid leukaemia cells and supports all-trans retinoic acid-induced neutrophil differentiation via death-associated protein kinase 2.

Acute promyelocytic leukaemia (APL) patients are successfully treated with all-trans retinoic acid (ATRA). However, concurrent chemotherapy is still necessary and less toxic therapeutic approaches are needed. Earlier studies suggested that in haematopoietic neoplasms, the green tea polyphenol epigallocatechin-3-gallate (EGCG) induces cell death without adversely affecting healthy cells. We aimed at deciphering the molecular mechanism of EGCG-induced cell death in acute myeloid leukaemia (AML). A significant increase of death-associated protein kinase 2 (DAPK2) levels was found in AML cells upon EGCG treatment paralleled by increased cell death that was significantly reduced upon silencing of DAPK2. Moreover, combined ATRA and EGCG treatment resulted in cooperative DAPK2 induction and potentiated differentiation. EGCG toxicity of primary AML blasts correlated with 67 kDa laminin receptor (67LR) expression. Pretreatment of AML cells with ATRA, causing downregulation of 67LR, rendered these cells resistant to EGCG-mediated cell death. In summary, it was found that (i) DAPK2 is essential for EGCG-induced cell death in AML cells, (ii) ATRA and EGCG cotreatment significantly boosted neutrophil differentiation, and 67LR expression correlates with susceptibility of AML cells to EGCG. We thus suggest that EGCG, by selectively targeting leukaemic cells, may improve differentiation therapies for APL and chemotherapy for other AML subtypes.

NDRG1/2 expression is inhibited in primary acute myeloid leukemia.

Expression of N-myc downregulated gene 1 (NDRG1) is associated with growth arrest and differentiation of tumor cells. In hematopoietic cells, NDRG1 was identified in a screen for differentiation-related genes in human myelomonocytic leukemic U937 cells. In the present study, we found significantly higher NDRG1 mRNA levels in granulocytes of healthy donors than in primary acute myeloid leukemia (AML) cells. Another NDRG family member, NDRG2, was significantly higher expressed in normal macrophages compared to primary AML cells. Moreover, NDRG1 mRNA levels increased in two acute promyelocytic leukemia (APL) patients as well as in NB4 and HT93 APL cells upon all-trans retinoic acid (ATRA) therapy. In line with these observations, silencing of NDRG1 diminished neutrophil differentiation of leukemic cell lines. In conclusion, we found an association of low NDRG1 levels with an immature cell phenotype and provide evidence that NDRG1 is functionally involved in neutrophil maturation.

The tumor suppressor gene hypermethylated in cancer 1 is transcriptionally regulated by E2F1.

The Hypermethylated in Cancer 1 (HIC1) gene encodes a zinc finger transcriptional repressor that cooperates with p53 to suppress cancer development. We and others recently showed that HIC1 is a transcriptional target of p53. To identify additional transcriptional regulators of HIC1, we screened a set of transcription factors for regulation of a human HIC1 promoter reporter. We found that E2F1 strongly activates the full-length HIC1 promoter reporter. Promoter deletions and mutations identified two E2F responsive elements in the HIC1 core promoter region. Moreover, in vivo binding of E2F1 to the HIC1 promoter was shown by chromatin immunoprecipitation assays in human TIG3 fibroblasts expressing tamoxifen-activated E2F1. In agreement, activation of E2F1 in TIG3-E2F1 cells markedly increased HIC1 expression. Interestingly, expression of E2F1 in the p53(-/-) hepatocellular carcinoma cell line Hep3B led to an increase of endogenous HIC1 mRNA, although bisulfite genomic sequencing of the HIC1 promoter revealed that the region bearing the two E2F1 binding sites is hypermethylated. In addition, endogenous E2F1 induced by etoposide treatment bound to the HIC1 promoter. Moreover, inhibition of E2F1 strongly reduced the expression of etoposide-induced HIC1. In conclusion, we identified HIC1 as novel E2F1 transcriptional target in DNA damage responses.

HIC1 tumour suppressor gene is suppressed in acute myeloid leukaemia and induced during granulocytic differentiation.

A hallmark of acute myeloid leukaemia (AML) is a block in differentiation caused by deregulated gene expression. The tumour suppressor Hypermethylated In Cancer 1 (HIC1) is a transcriptional repressor, which is epigenetically silenced in solid cancers. HIC1 mRNA expression was found to be low in 128 patient samples of AML and CD34+ progenitor cells when compared with terminally differentiated granulocytes. HIC1 mRNA was induced in a patient with t(15;17)-positive acute promyelocytic leukaemia receiving all-trans retinoic acid (ATRA) therapy. We therefore investigated whether HIC1 plays a role in granulocytic differentiation and whether loss of function of this gene might contribute to the differentiation block in AML. We evaluated HIC1 mRNA levels in HL-60 and U-937 cells upon ATRA-induced differentiation and in CD34+ progenitor cells after granulocyte colony-stimulating factor-induced differentiation. In both models of granulocytic differentiation, we observed significant HIC1 induction. When HIC1 mRNA was suppressed in HL-60 cells using stably expressed short hairpin RNA targeting HIC1, granulocytic differentiation was altered as assessed by CD11b expression. Bisulphite sequencing of GC-rich regions (CpG islands) in the HIC1 promoter provided evidence that the observed suppression in HL-60 cells was not because of promoter hypermethylation. Our findings indicate a role for the tumour suppressor gene HIC1 in granulocytic differentiation. Low expression of HIC1 may very well contribute to pathogenic events in leukaemogenesis.

The death-associated protein kinase 2 is up-regulated during normal myeloid differentiation and enhances neutrophil maturation in myeloid leukemic cells.

The death-associated protein kinase 2 (DAPK2) belongs to a family of Ca(2+)/calmodulin-regulated serine/threonine kinases involved in apoptosis. During investigation of candidate genes operative in granulopoiesis, we identified DAPK2 as highly expressed. Subsequent investigations demonstrated particularly high DAPK2 expression in normal granulocytes compared with monocytes/macrophages and CD34(+) progenitor cells. Moreover, significantly increased DAPK2 mRNA levels were seen when cord blood CD34(+) cells were induced to differentiate toward neutrophils in tissue culture. In addition, all-trans retinoic acid (ATRA)-induced neutrophil differentiation of two leukemic cell lines, NB4 and U937, revealed significantly higher DAPK2 mRNA expression paralleled by protein induction. In contrast, during differentiation of CD34(+) and U937 cells toward monocytes/macrophages, DAPK2 mRNA levels remained low. In primary leukemia, low expression of DAPK2 was seen in acute myeloid leukemia samples, whereas chronic myeloid leukemia samples in chronic phase showed intermediate expression levels. Lentiviral vector-mediated expression of DAPK2 in NB4 cells enhanced, whereas small interfering RNA-mediated DAPK2 knockdown reduced ATRA-induced granulocytic differentiation, as evidenced by morphology and neutrophil stage-specific maturation genes, such as CD11b, G-CSF receptor, C/EBPepsilon, and lactoferrin. In summary, our findings implicate a role for DAPK2 in granulocyte maturation.

Drug treatment is superior to allografting as first-line therapy in chronic myeloid leukemia.

Early allogeneic hematopoietic stem cell transplantation (HSCT) has been proposed as primary treatment modality for patients with chronic myeloid leukemia (CML). This concept has been challenged by transplantation mortality and improved drug therapy. In a randomized study, primary HSCT and best available drug treatment (IFN based) were compared in newly diagnosed chronic phase CML patients. Assignment to treatment strategy was by genetic randomization according to availability of a matched related donor. Evaluation followed the intention-to-treat principle. Six hundred and twenty one patients with chronic phase CML were stratified for eligibility for HSCT. Three hundred and fifty four patients (62% male; median age, 40 years; range, 11-59 years) were eligible and randomized. One hundred and thirty five patients (38%) had a matched related donor, of whom 123 (91%) received a transplant within a median of 10 months (range, 2-106 months) from diagnosis. Two hundred and nineteen patients (62%) had no related donor and received best available drug treatment. With an observation time up to 11.2 years (median, 8.9 years), survival was superior for patients with drug treatment (P = .049), superiority being most pronounced in low-risk patients (P = .032). The general recommendation of HSCT as first-line treatment option in chronic phase CML can no longer be maintained. It should be replaced by a trial with modern drug treatment first.

Hematopoietic and endothelial progenitor cell trafficking in patients with myeloproliferative diseases.

BACKGROUND AND OBJECTIVES: The presence of circulating hematopoietic progenitor cells in patients with myeloproliferative diseases (MPD) has been described. However, the exact nature of such progenitor cells has not been specified until now. The aim of this work was to investigate the presence of endothelial precursor cells in the blood of patients with MPD and to assess the role of the endothelial cell lineage in the pathophysiology of this disease. DESIGN AND METHODS: Endothelial progenitor cell marker expression (CD34, prominin (CD133), kinase insert domain receptor (KDR) or vascular endothelial growth factor receptor 2 (VEGFR2), and von Willebrand factor) was assessed in the blood of 53 patients with MPD by quantitative polymerase chain reaction. Clonogenic stem cell assays were performed with progenitor cells and monocytes to assess differentiation towards the endothelial cell lineage. The patients' were divided according to whether they had essential thrombocythemia (ET, n=17), polycythemia vera (PV, n=21) or chronic idiopathic myelofibrosis (CIMF, n=15) and their data compared with data from normal controls (n=16) and patients with secondary thrombo- or erythrocytosis (n=17). RESULTS: Trafficking of CD34-positive cells was increased above the physiological level in 4/17 patients with ET, 5/21 patients with PV and 13/15 patients with CIMF. A subset of patients with CIMF co-expressed the markers CD34, prominin (CD133) and KDR, suggesting the presence of endothelial precursors among the circulating progenitor cells. Clonogenic stem cell assays confirmed differentiation towards both the hematopoietic and the endothelial cell lineage in 5/10 patients with CIMF. Furthermore, the molecular markers trisomy 8 and JAK2 V617F were found in the grown endothelial cells of patients positive for trisomy 8 or JAK2 V617F in the peripheral blood, confirming the common clonal origin of both hematopoietic and endothelial cell lineages. INTERPRETATION AND CONCLUSIONS: Endothelial precursor cells are increased in the blood of a subset of patients with CIMF, and peripheral endothelial cells bear the same molecular markers as hematopoietic cells, suggesting a primary role of pathological endothelial cells in this disease.

Gene expression profiling reveals consistent differences between clinical samples of human leukaemias and their model cell lines.

Microarray gene expression profiles of fresh clinical samples of chronic myeloid leukaemia in chronic phase, acute promyelocytic leukaemia and acute monocytic leukaemia were compared with profiles from cell lines representing the corresponding types of leukaemia (K562, NB4, HL60). In a hierarchical clustering analysis, all clinical samples clustered separately from the cell lines, regardless of leukaemic subtype. Gene ontology analysis showed that cell lines chiefly overexpressed genes related to macromolecular metabolism, whereas in clinical samples genes related to the immune response were abundantly expressed. These findings must be taken into consideration when conclusions from cell line-based studies are extrapolated to patients.

Progenitor cell trafficking in physiologic conditions and in myeloproliferative diseases: quantification of CD34+ cells by polymerase chain reaction.

BACKGROUND AND OBJECTIVES: Previous studies using flow cytometry have shown that CD34+ cell trafficking is increased in patients with chronic idiopathic myelofibrosis. Few data exist on physiologic CD34 + cell trafficking and the quantification of very low cell ranges requires reliable and sensitive measurement techniques. The aim of this study was to establish a quantitative polymerase chain reaction (PCR) technique for studying CD34+ cell trafficking in physiologic conditions, and in patients with myeloproliferative diseases. DESIGN AND METHODS: CD34+ cell trafficking was measured in 56 controls [(healthy controls (n=21), patients with ischemic cardiopathy (n=21), patients with secondary thrombocytosis or erythrocytosis (n=14)], and in 37 untreated patients with myeloproliferative diseases diagnosed according to the WHO-criteria [(essential thrombocythemia (n=10), polycythemia vera (n=14) and chronic idiopathic myelofibrosis (n=13)]. Quantitative PCR was used to determine CD34 mRNA expression in peripheral blood samples. RESULTS: Physiologic CD34 mRNA expression ranges were determined in the healthy control group. Mean CD34 mRNA expression was within the physiologic range in patients with ischemic cardiopathy, secondary thrombocytosis or erythrocytosis, essential thrombocythemia and polycythemia vera (p=0.146), but was significantly increased in patients with chronic idiopathic myelofibrosis (p<0.001). When analyzed individually, 12/13 patients with chronic idiopathic myelofibrosis and 3/14 patients with polycythemia vera showed CD34 mRNA expression above the physiologic range. INTERPRETATION AND CONCLUSIONS: This is a first report about CD34+ cell trafficking measured by quantitative PCR. Quantitative PCR is a reliable method suitable for the quantification of very low cell populations. Our study confirms the significant increase of CD34+ cell trafficking in patients with chronic idiopathic myelofibrosis, and in a subset of patients with polycythemia vera. Prospective studies are underway to characterize these circulating CD34+ cells and to investigate their role in the pathophysiology of myeloproliferative diseases.

Polysomy 8 defines a clinico-cytogenetic entity representing a subset of myeloid hematologic malignancies associated with a poor prognosis: report on a cohort of 12 patients and review of 105 published cases.

Tetrasomy, pentasomy, and hexasomy 8 (polysomy 8) are relatively rare compared to trisomy 8. Here we report on a series of 12 patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or myeloproliferative disorder (MPD) associated with polysomy 8 as detected by conventional cytogenetics and fluorescence in situ hybridization (FISH). In an attempt to better characterize the clinical and hematological profile of this cytogenetic entity, our data were combined with those of 105 published patients. Tetrasomy 8 was the most common presentation of polysomy 8. In 60.7% of patients, polysomy 8 occurred as part of complex changes (16.2% with 11q23 rearrangements). No cryptic MLL rearrangements were found in cases in which polysomy 8 was the only karyotypic change. Our study demonstrates the existence of a polysomy 8 syndrome, which represents a subtype of AML, MDS, and MPD characterized by a high incidence of secondary diseases, myelomonocytic or monocytic involvement in AML and poor overall survival (6 months). Age significantly reduced median survival, but associated cytogenetic abnormalities did not modify it. Cytogenetic results further demonstrate an in vitro preferential growth of the cells with a high level of aneuploidy suggesting a selective advantage for polysomy 8 cells.

Testisin, a glycosyl-phosphatidylinositol-linked serine protease, promotes malignant transformation in vitro and in vivo.

Human testisin, a serine protease, is highly expressed in ovarian cancer and premeiotic spermatocytes with relatively little expression in other normal tissues. We first showed that testisin was localized on the surface of cultured tumor cells as a glycosyl-phosphatidylinositol-linked protein. We next explored the biological function of testisin in malignant transformation through manipulation of testisin expression in cell culture model systems. Small interfering RNA-mediated knockdown of endogenous testisin mRNA and protein expression in tumor cell lines led to increased apoptosis and diminished growth in soft agar. Conversely, overexpression of testisin in an epithelial cell line induced colony formation in soft agar as well as s.c. tumor growth in severe combined immunodeficient mice. A catalytic domain mutant was unable to induce soft-agar growth indicating that testisin protease activity is required for transformation. Ectopic expression of testisin in a human ovarian cancer cell line without endogenous testisin expression, led to the formation of larger tumors in severe combined immunodeficient mice. Data presented here provide the first demonstration that testisin can promote cellular processes that drive malignant transformation. Our functional data coupled with the restricted normal tissue distribution of testisin and its overexpression in a majority of ovarian cancers validates this cell surface protein as a target for therapeutic intervention.

The SNPlex genotyping system: a flexible and scalable platform for SNP genotyping.

We developed the SNPlex Genotyping System to address the need for accurate genotyping data, high sample throughput, study design flexibility, and cost efficiency. The system uses oligonucleotide ligation/polymerase chain reaction and capillary electrophoresis to analyze bi-allelic single nucleotide polymorphism genotypes. It is well suited for single nucleotide polymorphism genotyping efforts in which throughput and cost efficiency are essential. The SNPlex Genotyping System offers a high degree of flexibility and scalability, allowing the selection of custom-defined sets of SNPs for medium- to high-throughput genotyping projects. It is therefore suitable for a broad range of study designs. In this article we describe the principle and applications of the SNPlex Genotyping System, as well as a set of single nucleotide polymorphism selection tools and validated assay resources that accelerate the assay design process. We developed the control pool, an oligonucleotide ligation probe set for training and quality-control purposes, which interrogates 48 SNPs simultaneously. We present performance data from this control pool obtained by testing genomic DNA samples from 44 individuals. in addition, we present data from a study that analyzed 521 SNPs in 92 individuals. Combined, both studies show the SNPlex Genotyping system to have a 99.32% overall call rate, 99.95% precision, and 99.84% concordance with genotypes analyzed by TaqMan probe-based assays. The SNPlex Genotyping System is an efficient and reliable tool for a broad range of genotyping applications, supported by applications for study design, data analysis, and data management.

P73 status in B-cell chronic lymphocytic leukaemia.

B-cell chronic lymphocytic leukemia is a heterogenous disease with disturbed apoptosis in which the precise molecular defects leading to this pathogenesis are still unclear. The p73 gene (a p53 homologue) encodes 2 proteins with opposing functions. TAp73 induces cell cycle arrest and apoptosis, whilst the oncogenic deltaNp73 inhibits both TAp73 and p53 induced apoptosis. Microsatellite analysis was performed to investigate the p73 gene locus in B-CLL. Moreover, we investigated the expression of the TAp73 and deltaNp73 variant by measuring the mRNA transcripts in 51 B-CLL patients by real-time RT-PCR. And in addition, protein expression was analyzed by Western blotting technique in 20 B-CLL patients. There was no evidence of clonal loss of heterozygosity at 1p36, the p73 gene locus in B-CLL patients. The real time RT-PCR analysis showed that the expression of both p73 gene variants was much higher in leukemic cells compared to controls. In 17/20 (85%) patients deltaNp73 and TAp73 protein were present. The observed increase of expression of the antiapoptotic deltaNp73 variant in neoplastic cells may lead to a functional p53 inactivation. This mechanism might be relevant in malignancies with an intact p53 gene but disturbed apoptosis mechanisms such as in B-CLL.

Two clonal occurrences of tetrasomy 21 in an atypical chronic myeloid leukemia with wild-type RUNX1 alleles. Additional support for a gene dosage effect of chromosome 21 or RUNX1 in leukemia.

Atypical chronic myeloid leukemia (aCML) is a rare leukemic disorder with no specific genetic lesion. Here we demonstrate clonal occurrences of tetrasomy for the long arm of chromosome 21 in a patient with aCML, and a thorough review of the literature provides evidence that this chromosomal anomaly is a so far not recognised recurrent finding in aCML. Further, the timely association of the occurrence of the tetrasomy 21q with acceleration of the leukemia suggests a role for chromosome 21 in leukemic disease progression. The chromosome 21 gene most strongly implicated in both normal and abnormal hematopoiesis is RUNX1. Also, RUNX1 haploinsufficiency due to RUNX1 point mutations characterises the familial platelet disorder with propensity to develop leukemia, and thromboytopenia was a leading feature in the present case. Therefore, an extensive molecular analysis of RUNX1 was performed. However, these analyses did not reveal a mutation, and the results support a gene dosage effect for RUNX1 in myeloid disease similar to observations in lymphoid disease. Patients with aCML and a tetrasomy 21 may form a karyotypically and phenotypically defined subgroup of aCML.

Allelotyping in B-cell chronic lymphocytic leukemia (B-CLL).

B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous malignant disease, both in terms of molecular abnormalities and clinical course. The most frequent chromosomal aberrations in B-CLL are deletions on 13q, 11q, and 17p, and trisomy 12, all of which are of prognostic significance. These aberrations can be detected by conventional cytogenetic analysis and fluorescence in situ hybridization (FISH), but cytogenetics are hampered by the low mitotic index of B-CLL cells, and FISH depends on genetic information of candidate regions. Microsatellites are unique highly polymorphic and informative genetic markers dispersed in the human genome. They have become the most commonly used markers to trace loss of heterozygosity in tumors. Their detection by PCR is rapid and can be semi-automated with maximal robustness and reproducibility. In this review, we discuss the implications of a recent genome-wide analysis in B-CLL with 400 microsatellite markers. This analysis led to the detection of new aberrant loci in B-CLL which are not visible in the leukemic conventional karyotype. We conclude that microsatellite allelotyping provides a complementary comprehensive view of genetic alterations in B-CLL, and it may identify new loci with candidate genes relevant in the molecular biology of B-CLL.