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Previous studies on the pathogenesis of myelodysplastic syndrome (MDS) have identified multiple associated gene mutations, including mutations of tetmethylcytosinedioxygenase 2, isocitrate dehydrogenase [NADP(+)] 1 cytosolic, isocitrate dehydrogenase [NADP(+)] 2 mitochondrial and additional sex combs like 1 transcriptional regulator, all of which may be considered epigenetic regulators. Furthermore, mutations of RAS type GTPase family genes have been identified in 10–15% patients with MDS. The authors' previous study on the gene expression profile of cluster of differentiation 34+ cells using microarray analysis identified elevated expression of RAP1GTPase activating protein 1 (Rap1GAP) in patients with MDS compared with that in non-malignant blood diseases (NM) control group. To further investigate the mechanism of increased Rap1GAP expression, the methylation pattern of the promoter of this gene was determined in 86 patients with MDS (n=29), acute myeloid leukemia (AML) (n=31) or NM (n=26) using bisulfite-specific polymerase chain reaction and DNA sequencing. The results demonstrated that the methylation of Rap1GAP occurred in all 29 patients with MDS at multiple CpG sites. The methylation level of Rap1GAP in patients with MDS was decreased compared with that in patients with NM. Significant differences at 4CpG sites (5,7,8 and 12) of Rap1GAP promoter were identified between MDS and NM. Furthermore, based on the present clinical records of the patient cohort, the methylation status of Rap1GAP promoter did not appear to be associated with the clinicopathological characteristics of patients with MDS, including age, gender and International Prognosis Score System. The difference in methylation level at CpG site 8 of Rap1GAP promoter was identified to be significantly increased in patients with MDS-refractory anemia with ring sideroblasts compared with that in the MDS-refractory cytopenia with multilineage dysplasia or MDS-unclassified groups. The results of the present study suggest that patients with MDS exhibit a lower overall methylation level within Rap1GAP promoter compared with patients with NM or AML. In addition, the methylation level at the four identified CpG sites can distinguish between MDS and NM. [ABSTRACT FROM AUTHOR]

WT1 (Wilms' tumor gene 1) overexpression is implicated in the prognosis of acute leukemia. The purpose of this study was to investigate WT1 expression and its clinical implication in childhood acute leukemia (AL) in Chinese population. Bone marrow specimen from 200 children at different stages of acute leukemia and from 21 children without leukemia were studied. The WT1 expression at diagnostic marrow specimen in both acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL) was higher than control group, whereas WT1 expression in AML was higher than in ALL, and WT1 expression level in relapse in ALL increased more significantly than in AML. The WT1 expression level showed positive correlation with the hypodiploidy and BCR-ABL fusion gene in acute leukemia. A rapidly decrease of WT1 expression level predicted a good response to the induction therapy and low expression of WT1 correlates with remission status. This study suggested that WT1 expression levels in acute leukemia can potentially be a marker for evaluating therapeutic efficacy, correlating with monitoring minimal residue disease, and predicting hematological relapse in children acute leukemia. [ABSTRACT FROM AUTHOR]

Objective: To investigate the contribution of cellular senescence to the progression and prognosis of myelodysplastic syndrome (MDS). Materials and Methods: We have analyzed the expression of p16INK4a in bone marrow mononuclear cells or CD34+ cells from 53 patients with MDS, 12 acute myeloid leukemia (AML), and 11 healthy controls. Additionally, We have assessed quantitatively senescence-associated β-galactosidase (SA-β-gal) staining on bone marrow mononuclear cells from MDS and AML patients, HL60 and SHI-1 leukemia cell lines, and healthy control cells. Results: An upregulated expression of senescence-associated molecular marker p16INK4a was found in MDS compared with healthy controls, while a lower expression of p16INK4a was observed in AML compared with healthy controls. International Prognostic Scoring System score was negatively correlated with the percentage of p16INK4a-positive cells. The SA-β-gal activity measured by mean percentage of positive cells was significantly higher in MDS cases when compared with controls. Meanwhile, percentage of SA-β-gal–positive cells was also remarkably higher in dysplastic cells of MDS when compared to nondysplastic cells from MDS. Conclusions: These results of our present study suggested an accelerated cellular senescence occurred in MDS, and the cellular senescence may be involved in the progression and prognosis of MDS. [Copyright &y& Elsevier]

Numerous acquired molecular and cytogenetic abnormalities are strongly associated with hematological malignancies. The breakpoint cluster region-ABL proto-oncogene 1 ( BCR-ABL ) rearrangement leads to a p210 chimeric protein in typical chronic myeloid leukemia (CML), whereas 17-25% of patients with acute lymphocytic leukemia and 0.9-3% patients with de novo acute myeloid leukemia (AML) carry a p190 BCR-ABL fusion protein. Cases of patients with AML/CML carrying two specific primary molecular changes, BCR-ABL and core binding factor-β-myosin heavy chain 11 ( CBFβ-MYH11 ) fusion genes have been rarely reported. The present study aimed to understand the nature and mechanism of this particular type of leukemia through case reports and literature review. A total of four patients who were diagnosed as AML/CML with BCR-ABL and CBFβ-MYH11 fusion genes in the First Affiliated Hospital of Soochow University (Suzhou, China) between January 2004 and December 2012 were examined. Morphological analysis of bone marrow cells, flow cytometry, quantitative polymerase chain reaction of p 210BCR-ABL and CBFβ-MYH11 transcripts as well as cytogenetic and fluorescence in situ hybridization analyses were performed. A total of 4 patients who exhibited fusion of p 210BCR-ABL and CBFβ-MYH11 were identified. A single patient (case 1) was first diagnosed CML-acute phase (AP), which progressed rapidly to CML-blast crisis (BC), and three patients (cases 2, 3 and 4) were diagnosed with AML with bone marrow eosinophilia at first presentation with no evidence of previous onset of CML. All cases achieved remission following conventional chemotherapy/hematological stem cell transplantation combined with the inhibitor of tyrosine kinase (TKI) maintenance therapy. The patients with CML carrying and expressing BCR-ABL and CBFβ-MYH11 fusion genes appeared more likely to rapidly progress to AP or BC. Therefore, the product of the CBFβ-MYH11 fusion gene may serve an important role in the transformation of CML. The co-expression of p 210BCR-ABL and CBFβ-MYH11 fusion genes in myeloid leukemia may be a molecular event occurring not only during the development of CML, but also in AML.

S100A8 has been increasingly recognized as a biomarker in multiple solid tumors and has played pivotal roles in hematological malignancies. S100A8 is potentially an indicator for poor survival in acute myeloid leukemia (AML) in retrospective studies. However, the mechanisms of S100A8 are diverse in cancers. In this study, we investigated the correlation of S100A8 at the transcription level with clinical parameters in 91 de novo AML patients and explored its mechanisms of chemoresistance to etoposide in vitro. The transcription level of S100A8 was significantly lower at initial and relapse stages of AML samples than at complete remission (P<0.001) and than in the control group (P=0.0078), while no significant difference could be found between initial and relapse stages (P=0.257). Patients with high transcription levels of S100A8 exhibited a shorter overall survival (P=0.0012). HL-60 cells transfected with S100A8 showed resistance to etoposide with a higher level IC50 value and lower apoptosis rate compared with HL-60 cells transfected with empty vector. Thirty-six genes were significantly downregulated and 12 genes were significantly upregulated in S100A8 overexpression group compared with control group in which 360 genes involved in apoptotic genes array were performed by real-time reverse transcriptase polymerase chain reaction. Among them, the caspase-3, Bcl-2, and Bax were verified by Western blot analysis which indicated that the role of S100A8 in resistance to chemotherapy was closely related with antiapoptosis. In conclusion, critical S100A8 provided useful clinical information in predicting the outcome of AML. The main mechanism of S100A8 which promoted chemoresistance was antiapoptosis.

The AML1-ETO fusion transcription factor generated by the t(8;21) translocation is considered to deregulate the expression of genes that are crucial for normal differentiation and proliferation of hematopoietic progenitors, resulting in acute myelogenous leukemia by recruiting co-repressor complexes to DNA. To investigate the role of AML1-ETO in leukemogenesis, we transfected the cloned AML1-ETO cDNA and expressed the AML1-ETO protein in U937 myelomonocytic leukemia cells. By focusing on the anti-apoptotic gene Bcl-2, the key regulator gene of granulocytic differentiation CCAAT/enhancer-binding protein α (CEBPA) and the tumor suppressor gene p14(ARF), we found that both AML1-ETO-expressing cell lines and t(8;21) leukemia samples displayed low levels of these three genes. Chromatin immunoprecipitation assays demonstrated that Bcl-2, CEBPA and p14(ARF) were direct transcriptional targets of AML1-ETO. The universal binding of AML1-ETO to genomic DNA resulted in recruitment of methyl-CpG binding protein 2 (MeCP2), reduction of histone H3 or H4 acetylation and increased trimethylation of histone H3 lysine 9 as well as lysine 27 indicating that AML1-ETO induced heterochromatic silencing of Bcl-2, CEBPA and p14(ARF). These results suggested that the aberrant transcription factor AML1-ETO epigenetically silenced the function of the Bcl-2, CEBPA and p14(ARF) genes by inducing repressed chromatin configurations at their promoters through histone modifications.

Background: Interactions of tumor cells with the microenvironment were deemed to promote the tumor invasion and metastasis. CXC chemokine receptor 4 (CXCR4) and extracellular matrix metalloproteinase inducer (EMMPRIN) had reported to participate in this process. However the roles of bone marrow microenvironment in leukemic infiltration were not well investigated., Methods: A co-culture system between SHI-1 cells and bone marrow stromal cells (BMSCs) is used to simulate the interactions of leukemic cells with their microenvironment. The trans-matrigel invasion was used to detect the capability of SHI-1 cells invasion. The BMSCs and SHI-1 cells were mixed in a ratio of 1:10 and added to the millicell chamber coated with matrigel. Either the co-culture supernatant or the functional blocking peptide of CXCR4 and EMMPRIN were added to the trans-matrigel invasion system. The expressions of EMMPRIN in SHI-1 cells and BMSCs were detected by RT-PCR. The changes of the expression of matrix metalloproteinase-2, 9 (MMP-2, MMP-9), tissue inhibitor of metalloproteinase 2 (TIMP-2), and CXCR4 mRNA in SHI-1 cells were determined by real-time PCR. The concentration of stromal cell derived factor 1 (SDF-1) in serum free supernatant was measured by ELISA., Results: Both SHI-1 cells and BMSCs express EMMPRIN. SHI-1 cells could hardly invade the matrigel membrane; the coculture supernatant did not induce the invasion of SHI-1 cells. When contacting directly with BMSCs, SHI-1 cells invaded to the lower chamber of millicell were significantly increased. The functional blocking peptide of CXCR4 and EMMPRIN could significantly inhibit the invasion triggered by BMSCs. When co-culturing with BMSCs, the expression of CXCR4, MMP-2, MMP-9 and TIMP-2 mRNA in SHI-1 cells were significantly elevated in company with a significantly higher level of SDF-1 in the co-cultured serum-free supernatant., Conclusion: The interactions of leukemic cells and BMSCs play important roles in leukemic cell infiltration.

Rap1 is a small G protein belonging to the RAS superfamily. Rap1 signalling has effects on cell growth, cell proliferation and involves in regulation of the mitogen activated protein (MAP) kinase or ERK (extracellular signal regulated kinase) cascade. Rap1 will directly activate ERK through B-Raf. B-Raf is a member of Raf family, and presents in neuronal and hematopoietic cells. Oncogenic mutations of gene RAS are most frequent and detected in 20% - 30% of human leukemias and 10% - 15% of MDS cases. The review summarizes the regulatory function of Rap1 in development of hematopoietic cells and effect of Rap1 in hematologic malignancies.

Previous study on the gene expression profile of human MDS by using microarray discovered that transcription of RAP1GAP was up-regulated, which was confirmed by quantitative RT-PCR in expanding cohort of MDS patients. This study was pourposed to investigate the expression of RAP1GAP in human MDS and its clinical relevance. The expression of RAP1GAP in bone marrow cells of 19 MDS patients was detected by flow cytometry and was compared with that in patients with non-malignant blood diseases and acute leukemias, meanwhile the relevance between expression level of RAP1GAP and hemoglobin, leukocytes, platelets, blasts percentage in bone marrow cells and IPSS score was analyzed. The results indicated that the expression level of RAP1GAp in MDS patients significantly increased as compared with patients with non-malignant blood diseases or AML (8.42 +/- 8.37% vs 2.97 +/- 4.75% or 2.26 +/- 4.24%). Among MDS patients, the expression level of RAP1GAP in MDS-RA was significantly higher than that in MDS-RAEB (11.64 +/- 9.07% vs 4.37 +/- 4.65%). However, no definitive correlation of expression level with above-mentioned clinical parameters was found in detected patients with DMS. In conclusion, the expression of RAP1GAP in MDS patients obviously increases, the relationship between expression level of RAP1GAP and laboratory hematological parameter and IPSS score does not be confirmed. The role played by RAP1GAP expression in the pathogenesis of MDS and its clinical significance during progression of MDS towards AML deserves further studies.

cDNA microarray, recently applied to analyze gene expression profile of cancers, was difficult to be utilized in myelodysplastic syndrome (MDS) for a special need of excessive mRNA hardly provided by ordinary bone marrow aspiration in MDS patients. The aim of this study was to investigate the feasibility of exploring the molecular events underlying MDS by using cDNA microarray and mixing mRNA from multiple patients. A commercially purchased BioStar H141 cDNA microarray containing 14,110 clones of cDNA or EST was employed to analyze the gene expression profile of bone marrow mononuclear cells from two cases of MDS. Equal amount of total RNA from each patient was mixed, reversely transcribed to cDNA and labeled with Cy5. Mixture of Cy5-labeled cDNA and Cy3-labeled cDNA from normal bone marrow cells was concomitantly hybridized to H141 microarray in duplicate. In H141 chips, 1,064 cDNAs were spotted at least twice targeting different fragments of a single gene cDNA. The results showed that among these 1,064 cDNA clones, the expression level of 625 (58.7%) and 630 (59.2%) ones was consistent within these two chips, respectively, 297 (27.9%) and 191 (18.0%) inconsistent, 21 (2.0%) and 11 (1.0%) in opposite. Among 411 duplicately spotted cDNAs with complete data, expression levels of 400 (97.3%) was consistent between two chips. 488 genes with known function were identified as differentially expressed in MDS, among which 101 genes were involved in hematopoiesis regulation, including those encoding transcription factors, cell cycle-regulating proteins, metabolism-relating enzymes, and adhesive molecules. It is concluded that cDNA microarray can be used for profiling gene expression of mixed MDS samples and replication shall be necessary for reducing the data bias caused by experimental operation.

Background: This study was designed to quantitatively measure WT-1 expression levels in patients with chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL) during follow-up and to clarify the value of WT-1 as a molecular marker in minimal residual disease monitoring., Methods: The TaqMan quantitative real-time RT-PCR method was established by using cloned WT-1 cDNA or synthesized oligonucleotides resembling WT-1 cDNA fragments in limit dilution as template until a stable and reliable standard curve was obtained. In a 25-month follow-up, the transcriptional levels of WT-1, Bcr-Abl, and Abl gene, were quantitatively measured in bone marrow cells from 25 CML or acute lymphoblastic leukemia (ALL) patients with the Ph chromosome. In addition, the expression of these genes in 40 samples of normal peripheral blood was also examined using the same method. The ratios of WT-1/Abl and Bcr-Abl/Abl were both plotted, and the two expression patterns were compared as well as their clinical significance., Results: The levels of WT-1 expression in normal peripheral blood were detectable. In CML and Ph positive ALL patients, WT-1 expression levels changed in parallel with the Bcr-Abl expression pattern as the disease progressed or responded to effective treatment., Conclusion: WT-1 expression provides a novel molecular marker in addition to Bcr-Abl for monitoring minimal residual disease (MRD) and targeting therapy in Ph chromosome-positive leukemia patients.

The identification of genes inducing resistance to anticancer chemotherapeutic agents and their introduction into hematopoietic cells represents a promising approach to overcome bone marrow toxicity, the limiting factor for most high-dose chemotherapy regimens. Because resistance to cyclophosphamide has been correlated with increased levels of expression of the aldehyde-dehydrogenase (ALDH1) gene in tumor cells lines in vitro, this study tested whether ALDH1 overexpression could directly induce cyclophosphamide resistance. Results showed that a retroviral vector was used to transduce full-length human ALDH1 cDNA into human hematopoietic cell line K562 that was then tested for resistance to 4-hydroxycyclophosphamide (4-HC), an active analogue of cyclophosphamide. Overexpression of the ALDH1 gene resulted in a significant increases in cyclophosphamide resistance in transduced K562 cells (50% inhibition concentration, IC50 = 10 micro mol/L). These findings indicate that ALDH1 overexpression is sufficient to induce cyclophosphamide resistance in vitro and provide a basis for testing the efficacy of ALDH1 gene transduction to protect bone marrow cells from high-dose cyclophosphamide in vivo.