25 research outputs found
MicroRNA expression profiling in Imatinib-resistant Chronic Myeloid Leukemia patients without clinically significant ABL1-mutations
The development of Imatinib Mesylate (IM), the first specific inhibitor of BCR-ABL1, has had a major impact in patients with Chronic Myeloid Leukemia (CML), establishing IM as the standard therapy for CML. Despite the clinical success obtained with the use of IM, primary resistance to IM and molecular evidence of persistent disease has been observed in 20-25% of IM treated patients. The existence of second generation TK inhibitors, which are effective in patients with IM resistance, makes identification of predictors of resistance to IM an important goal in CML. In this study, we have identified a group of 19 miRNAs that may predict clinical resistance to IM in patients with newly diagnosed CML
Down-Regulation of hsa-miR-10a in Chronic Myeloid Leukemia CD34+ Cells Increases USF2-Mediated Cell Growth
MicroRNAs (miRNA) are small noncoding,
single-stranded RNAs that inhibit gene expression at a
posttranscriptional level, whose abnormal expression
has been described in different tumors. The aim of our
study was to identify miRNAs potentially implicated
in chronic myeloid leukemia (CML). We detected an
abnormal miRNA expression profile in mononuclear and
CD34+ cells from patients with CML compared with
healthy controls. Of 157 miRNAs tested, hsa-miR-10a,
hsa-miR-150, and hsa-miR-151 were down-regulated,
whereas hsa-miR-96 was up-regulated in CML cells.
Down-regulation of hsa-miR-10a was not dependent
on BCR-ABL1 activity and contributed to the increased
cell growth of CML cells. We identified the upstream
stimulatory factor 2 (USF2) as a potential target of
hsa-miR-10a and showed that overexpression of USF2
also increases cell growth. The clinical relevance of
these findings was shown in a group of 85 newly
diagnosed patients with CML in which expression of
hsa-miR-10a was down-regulated in 71% of the patients,
whereas expression of USF2 was up-regulated in 60% of
the CML patients, with overexpression of USF2 being
significantly associated with decreased expression of
hsa-miR-10a (P = 0.004). Our results indicate that
down-regulation of hsa-miR-10a may increase USF2 and
contribute to the increase in cell proliferation of CML
implicating a miRNA in the abnormal behavior of CML
Frequent and simultaneous epigenetic inactivation of TP53 pathway genes in acute lymphoblastic leukemia
Aberrant DNA methylation is one of the most frequent alterations in patients with Acute Lymphoblastic Leukemia (ALL).
Using methylation bead arrays we analyzed the methylation status of 807 genes implicated in cancer in a group of ALL
samples at diagnosis (n = 48). We found that 154 genes were methylated in more than 10% of ALL samples. Interestingly,
the expression of 13 genes implicated in the TP53 pathway was downregulated by hypermethylation. Direct or indirect
activation of TP53 pathway with 5-aza-29-deoxycitidine, Curcumin or Nutlin-3 induced an increase in apoptosis of ALL cells.
The results obtained with the initial group of 48 patients was validated retrospectively in a second cohort of 200 newly
diagnosed ALL patients. Methylation of at least 1 of the 13 genes implicated in the TP53 pathway was observed in 78% of
the patients, which significantly correlated with a higher relapse (p = 0.001) and mortality (p,0.001) rate being an
independent prognostic factor for disease-free survival (DFS) (p = 0.006) and overall survival (OS) (p = 0.005) in the
multivariate analysis. All these findings indicate that TP53 pathway is altered by epigenetic mechanisms in the majority of
ALL patients and correlates with prognosis. Treatments with compounds that may reverse the epigenetic abnormalities or
activate directly the p53 pathway represent a new therapeutic alternative for patients with ALL
BCR-ABL1-induced expression of HSPA8 promotes cell survival in chronic myeloid leukaemia
In order to determine new signal transduction pathways implicated in
chronic myeloid leukaemia (CML), we performed a gene expression profile
comparison between CD34+ cells from CML patients and healthy donors.
Functional studies were performed using the Mo7e and Mo7e-p210 cell lines.
Expression of CCND1 (Cyclin D1), as well as the chaperone HSPA8, which is
important for regulation of CCND1, were significantly upregulated in CD34+
CML cells. Upregulation of HSPA8 was dependent, at least in part, on STAT5
(signal transducer and activator of transcrition 5)-dependent transcriptional
activation, as demonstrated by chromatin immunoprecipitation. The
presence of HSPA8 in the nuclear protein fraction as well as its binding to
CCND1 suggests that it may contribute to stabilization of the CCND1/CDK4
complex, which, in turn, may participate in proliferation of CML
cells. Treatment of CML cells with the specific HSPA8 inhibitor
15-deoxyspergualin induced inhibition of CML cell viability but did not
induce apoptosis. In conclusion, our studies suggest that STAT5-mediated
activation of HSPA8 induces nuclear translocation and activation of the
CCND1/CDK4 complex leading to increased proliferation of CML cells,
deciphering a new pathway implicated in CML and supporting a potential
role of chaperone inhibitors in the treatment of CML
Preclinical activity of LBH589 alone or in combination with chemotherapy in a xenogeneic mouse model of human acute lymphoblastic leukemia.
Histone deacetylases (HDACs) have been identified as therapeutic targets due to their regulatory function in chromatin structure and organization. Here, we analyzed the therapeutic effect of LBH589, a class I-II HDAC inhibitor, in acute lymphoblastic leukemia (ALL). In vitro, LBH589 induced dose-dependent antiproliferative and apoptotic effects, which were associated with increased H3 and H4 histone acetylation. Intravenous administration of LBH589 in immunodeficient BALB/c-RAG2(-/-)Îłc(-/-) mice in which human-derived T and B-ALL cell lines were injected induced a significant reduction in tumor growth. Using primary ALL cells, a xenograft model of human leukemia in BALB/c-RAG2(-/-)Îłc(-/-) mice was established, allowing continuous passages of transplanted cells to several mouse generations. Treatment of mice engrafted with T or B-ALL cells with LBH589 induced an in vivo increase in the acetylation of H3 and H4, which was accompanied with prolonged survival of LBH589-treated mice in comparison with those receiving vincristine and dexamethasone. Notably, the therapeutic efficacy of LBH589 was significantly enhanced in combination with vincristine and dexamethasone. Our results show the therapeutic activity of LBH589 in combination with standard chemotherapy in pre-clinical models of ALL and suggest that this combination may be of clinical value in the treatment of patients with ALL
TET2 mutations are associated with specific 5-methylcytosine and 5-hydroxymethylcytosine profiles in patients with chronic myelomonocytic leukemia
Chronic myelomonocytic leukemia (CMML) has recently been associated with a high incidence of diverse mutations in genes such as TET2 or EZH2 that are implicated in epigenetic mechanisms. We have performed genome-wide DNA methylation arrays and mutational analysis of TET2, IDH1, IDH2, EZH2 and JAK2 in a group of 24 patients with CMML. 249 genes were differentially methylated between CMML patients and controls. Using Ingenuity pathway analysis, we identified enrichment in a gene network centered around PLC, JNK and ERK suggesting that these pathways, whose deregulation has been recently described in CMML, are affected by epigenetic mechanisms. Mutations of TET2, JAK2 and EZH2 were found in 15 patients (65%), 4 patients (17%) and 1 patient (4%) respectively while no mutations in the IDH1 and IDH2 genes were identified. Interestingly, patients with wild type TET2 clustered separately from patients with TET2 mutations, showed a higher degree of hypermethylation and were associated with higher risk karyotypes. Our results demonstrate the presence of aberrant DNA methylation in CMML and identifies TET2 mutant CMML as a biologically distinct disease subtype with a different epigenetic profile
Epigenetic regulation of Wnt-signaling pathway in acute lymphoblastic leukemia
Activation of the Wnt/ -catenin signaling
pathway is a hallmark of a number of
solid tumors. We analyzed the regulation
of the Wnt/ -catenin pathway in acute
lymphoblastic leukemia (ALL) and its role
in the pathogenesis of the disease. We
found that expression of the Wnt inhibitors
sFRP1, sFRP2, sFRP4, sFRP5, WIF1,
Dkk3, and Hdpr1 was down-regulated due
to abnormal promoter methylation in ALL
cell lines and samples from patients with
ALL. Methylation of Wnt inhibitors was
associated with activation of the Wntsignaling
pathway as demonstrated by
the up-regulation of the Wnt target genes
WNT16, FZ3, TCF1, LEF1, and cyclin D1 in
cell lines and samples and the nuclear
localization of -catenin in cell lines. Treatment
of ALL cells with the Wnt inhibitor
quercetin or with the demethylating agent
5-aza-2 -deoxycytidine induced an inactivation
of the Wnt pathway and induced
apoptosis of ALL cells. Finally, in a group
of 261 patients with newly diagnosed
ALL, abnormal methylation of Wnt inhibitors
was associated with decreased 10-
year disease-free survival (25% versus
66% respectively, P < .001) and overall
survival (28% versus 61% respectively,
P .001). Our results indicate a role of
abnormal Wnt signaling in ALL and establish
a group of patients with a significantly
worse prognosis (methylated
group)
Epigenetic regulation of Wnt-signaling pathway in acute lymphoblastic leukemia
Activation of the Wnt/ -catenin signaling
pathway is a hallmark of a number of
solid tumors. We analyzed the regulation
of the Wnt/ -catenin pathway in acute
lymphoblastic leukemia (ALL) and its role
in the pathogenesis of the disease. We
found that expression of the Wnt inhibitors
sFRP1, sFRP2, sFRP4, sFRP5, WIF1,
Dkk3, and Hdpr1 was down-regulated due
to abnormal promoter methylation in ALL
cell lines and samples from patients with
ALL. Methylation of Wnt inhibitors was
associated with activation of the Wntsignaling
pathway as demonstrated by
the up-regulation of the Wnt target genes
WNT16, FZ3, TCF1, LEF1, and cyclin D1 in
cell lines and samples and the nuclear
localization of -catenin in cell lines. Treatment
of ALL cells with the Wnt inhibitor
quercetin or with the demethylating agent
5-aza-2 -deoxycytidine induced an inactivation
of the Wnt pathway and induced
apoptosis of ALL cells. Finally, in a group
of 261 patients with newly diagnosed
ALL, abnormal methylation of Wnt inhibitors
was associated with decreased 10-
year disease-free survival (25% versus
66% respectively, P < .001) and overall
survival (28% versus 61% respectively,
P .001). Our results indicate a role of
abnormal Wnt signaling in ALL and establish
a group of patients with a significantly
worse prognosis (methylated
group)
Downregulation of DBC1 expression in acute lymphoblastic leukaemia is mediated by aberrant methylation of its promoter
The DBC1 gene is a potential tumour suppressor gene that is commonly
hypermethylated in epithelial cancers. We studied the role of promoter
hypermethylation in the regulation of DBC1 in acute lymphoblastic
leukaemia (ALL) cell lines and 170 ALL patients at diagnosis. Abnormal
methylation of DBC1 was observed in all ALL cell lines and in 17% of ALL
patients. Moreover, DBC1 methylation was associated with decreased DBC1
expression, while treatment of ALL cells with 5-Aza-2Âą-deoxycytidine resulted
in demethylation of the promoter and upregulation of DBC1 expression.
Fluorescence in situ hybridisation identified the deletion of one allele of
DBC1 in some ALL cell lines, which indicated that the lack of DBC1
expression was due to deletion of one allele and methylation of the other. In
conclusion, these results demonstrate, for the first time, that the expression of
DBC1 is downregulated in a percentage of patients with ALL due to the
hypermethylation of its promoter and/or gene deletion