Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression data from children diagnosed with ALL in vitro sensitive or resistant to prednisolone

ABSTRACT: Although the prognosis for childhood Acute Lymphoblastic Leukemia (ALL) in general has improved tremendously over the last decades, the survival chances for infants (<1 year of age) with ALL remains poor. A major obstacle hampering successful treatment results in infant ALL is cellular resistance to several drugs currently used in the treatment of ALL, especially to prednisolone (or prednisone). Therefore we set out to search for genes differentially expressed between from infant (children <1 year of age) and non-infant (children >1 year of age) ALL samples either resistant or sensitive to prednisolone. The in vitro prednisolone response in primary infant and non-infant ALL samples was determined by 4-day cytotoxicity (MTT) assays. Patient samples were characterized as either sensitive or resistant based on the LC50 value (i.e. the concentration of prednisolone lethal to 50% of the leukemic cells). Prednisolone sensitivity was defined by LC50 values <0.1 ug/mL prednisolone, and prednisolone resistance by LC50 values >150 ug/mL. Samples showing intermediate in vitro prednisolone responses were excluded. In total 25 infant (<1 year of age) and 27 non-infant (>1 year of age) ALL samples were selected for RNA extraction and hybridization on Affymetrix HU133A microarrays. The obtained gene expression signatures were used to identify gene differentially expressed between prednisolone resistant and sensitive patients, in order to gain insights into the mechanism(s) underlying prednisolone resistance in infant and non-infant ALL.

ORGANISM(S): Homo sapiens

SUBMITTER: Ronald Stam

PROVIDER: E-GEOD-19143 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Association of high-level MCL-1 expression with in vitro and in vivo prednisone resistance in MLL-rearranged infant acute lymphoblastic leukemia.

Stam Ronald W RW Den Boer Monique L ML Schneider Pauline P de Boer Jasper J Hagelstein Jill J Valsecchi Maria G MG de Lorenzo Paola P Sallan Stephen E SE Brady Hugh J M HJ Armstrong Scott A SA Pieters Rob R

Blood 20091204 5

MLL-rearranged acute lymphoblastic leukemia (ALL) represents an unfavorable type of leukemia that often is highly resistant to glucocorticoids such as prednisone and dexamethasone. Because response to prednisone largely determines clinical outcome of pediatric patients with ALL, overcoming resistance to this drug may be an important step toward improving prognosis. Here, we show how gene expression profiling identifies high-level MCL-1 expression to be associated with prednisolone resistance in ...[more]

PMID: 19965632

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Project description:Extensive molecular and prognostic characterization of wild-type MLL infant ALL. Background: Approximately 20% of all infant ALL cases carry wild-type (or germline) MLL genes. To date, wild-type MLL infant ALL patients are generally regarded as young pediatric precursor B-ALL patients, but extensive characterization of this specific patient group largely remains unacknowledged. Methods: We here studied a relatively large cohort of 78 wild-type MLL infant ALL samples, using clinical parameters, array-comparative genomic hybridization analysis, gene expression profiling, multiplex ligation-dependent probe amplification, and conventional sequencing. Findings: Wild-type MLL infant ALL patients are generally characterized by a lower incidence of favourable prognostic factors than pediatric (non-infant) B-ALL patients, and patients at high risk of therapy failure typically display an immature pro-B immunophenotype or respond poorly to prednisone. Using gene expression profiling, we found MEIS1 expression to additionally be highly predictive for clinical outcome in wild-type MLL infant ALL with a favourable prognosis in the wild-type MLL infants with low MEIS1 expression (DFS 88%% versus 50%, p=0•01). Overall the incidence of DNA copy number variations and genetic abnormalities in genes involved in B-cell differentiation is lower in wild-type MLL infant ALL patients as compared with pediatric precursor B-ALL patients. Interpretation: Wild-type MLL infant ALL represents a highly heterogeneous patient group, which cannot be unified by one or a few known recurrent genomic aberrations. High-level MEIS1 expression and an immature pro-B immunophenotype in high-risk wild-type MLL infant ALL patients shows parallel with the unfavourable prognosis of MLL-rearranged infant ALL patients. In contrast, wild-type MLL infant ALL patients expressing lower levels of MEIS1 and displaying more differentiated (pre-B or common) phenotypes may well be more related to pediatric precursor B-ALL patients older than 1 year of age. We advocate that a treatment strategy in wild-type MLL infant ALL based on MEIS1 expression could be beneficial for improving survival. Gene expression profiling of wild-type MLL infant ALL. Additional wild-type MLL infant ALL patient samples (n=17) to the earlier samples published under GSE19475 (GSM485309 to GSM485322).

Project description:Background: Glucocorticoids are important pharmaceutical agents in the treatment of acute lymphoblastic leukemia in children. Resistance or sensitivity to glucocorticoids is considered to be of crucial importance for disease prognosis. Prednisolone is a first-line chemotherapeutic agent in the treatment of acute lymphoblastic leukemia. Here, the effects of prednisolone on the resistant CCRF-CEM leukemic cell line were studied. Methods: Prednisolone’s cytotoxic and cell cycle effects were studied with flow cytometry. NF-κB translocation was studied with Western Blotting and differential gene expression was studied with cDNA microarrays. Results: Prednisolone exerted a delayed biphasic effect, necrotic at low doses and apoptotic at higher doses. At low doses, prednisolone exerted a pre-dominant mitogenic effect despite its induction on total cell death, while at higher doses, prednisolone’s mitogenic and cell death effects were counterbalanced. NF-κB was constitutively present in the nucleus. Early gene microarray analysis revealed 40 differentially expressed genes upon 4 hours of prednisolone’s exposure. Notable differences in gene regulation were observed between the lowest and the highest glucocorticoid doses. Prednisolone activated genes related to apoptosis/tumor suppression, cell cycle progression, metabolism and intra-/ extra-cellular signaling pathways. Conclusions: The mitogenic/biphasic effects of prednisolone are of clinical importance in the case of resistant leukemic cells. This approach might lead to the identification of gene candidates for future molecular drug targets in combination therapy with glucocorticoids, along with early markers for glucocorticoid resistance. Elucidation of the mechanisms of GC action may lead to identification of gene targets responsible for GC resistance. Key tools in this process are high-throughput technologies such as microarray-based gene expression analysis. For this purpose, the parental CCRF-CEM cell line was chosen as the system of study for the effects of prednisolone treatment. This is a T-cell leukemia cell line characterized by a mutation (L753F) on one GR gene allele that impairs ligand binding (Thompson and Johnson 2003). It is known that both the DNA and ligand binding domains of the GR are required in order to repress NF-κB transactivation (Wissink, van Heerde et al. 1997). Interestingly, concerning the question whether this mutation would affect GC resistance, it has been reported previously that both the GC-resistant as well as the GC-sensitive CCRF-CEM subclones express heterogeneous populations of the GR (GRwt/GRL753F) (Palmer and Harmon 1991; Powers, Hillmann et al. 1993). The CCRF-CEM cell line has been reported to be resistant to GCs, presumably due to the accumulation of more resistant variants after long periods of prolonged culture (Norman and Thompson 1977). It is possible that these cells are clonally inhomogeneous, as possibly the cells obtained in vivo by patients. Moreover, the large number of the CCRF-CEM subclone studies in the literature makes it difficult to choose an appropriate resistant cell model. In addition, the utilization of an in vitro system for this study offered reproducibility, an opportunity to closely examine intracellular signals and avoid interference from other in vivo-participating systems. Thus, the cell line used for this study was considered to be useful in studying GC action and resistance in leukemic cells. The aim of this work was to determine the cytotoxic, cell cycle phase distribution and early cancer-specific gene expression effects of prednisolone in CCRF-CEM cells, as an in vitro model of ALL resistance to glucocorticoids. The early gene expression profile allowed identification of genes initiating pivotal, early onset regulatory mechanisms activated by GC and excluded ensuing feedback responses and further downstream signals. Samples tested were in the form of a loop-design i.e. control vs. 10nM prednisolone (designated 0vs1) , 10nM prednisolone vs.700uM prednisolone (designated 1vs3) and control vs. 700uM prednisolone (designated 0vs3), the sum of the logarithms of the first two should equal the third. In other words if Rj,i is the ratio of the ith gene in the jth experiment then R0vs1,i+R1vs3,i=R0vs3,i. We tested this using a statistical test. We have applied an intensity-dependent z-score where the sum of the ratios was compared to the ratio of the third experiment. If the difference was significant genes, in a standard deviation threshold of ±1.5 in relative units, were rejected from further analysis (Kerr and Churchill 2001; Kerr and Churchill 2001; Altman and Hua 2006; Kerr and Churchill 2007).

Dataset Information

Gene expression data from children diagnosed with ALL in vitro sensitive or resistant to prednisolone

Publications

Association of high-level MCL-1 expression with in vitro and in vivo prednisone resistance in MLL-rearranged infant acute lymphoblastic leukemia.

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