188 research outputs found
Resistance to different classes of drugs is associated with impaired apoptosis in childhood acute lymphoblastic leukemia
Resistance of leukemic cells to chemotherapeutic agents is associated with
an unfavorable outcome in pediatric acute lymphoblastic leukemia (ALL). To
investigate the underlying mechanisms of cellular drug resistance, the
activation of various apoptotic parameters in leukemic cells from 50
children with ALL was studied after in vitro exposure with 4 important
drugs in ALL therapy (prednisolone, vincristine, l-asparaginase, and
daunorubicin). Exposure to each drug resulted in early induction of
phosphatidylserine (PS) externalization and mitochondrial transmembrane
(Deltapsim) depolarization followed by caspase-3 activation and
poly(ADP-ribose) polymerase (PARP) inactivation in the majority of
patients. For all 4 drugs, a significant inverse correlation was found
between cellular drug resistance and (1) the percentage of cells with PS
externalization (<.001 < P <.008) and (2) the percentage of cells with
Deltapsim depolarization (.002 < P <.02). However, the percentage of cells
with caspase-3 activation and the percentage of cells with PARP
inactivation showed a significant inverse correlation with cellular
resistance for prednisolone (P =.001; P =.001) and l-asparaginase (P =.01;
P =.001) only. This suggests that caspase-3 activation and PARP
inactivation are not essential for vincristine- and daunorubicin-induced
apoptosis. In conclusion, resistance to 4 unrelated drugs is associated
with defect(s) upstream or at the level of PS externalization and
Deltapsim depolarization. This leads to decreased activation of apoptotic
parameters in resistant cases of pediatric AL
Biological background of pediatric medulloblastoma and ependymoma: A review from a translational research perspective
Survival rates of pediatric brain tumor patients have significantly improved over the years due to developments in diagnostic techniques, neurosurgery, chemotherapy, radiotherapy, and supportive care. However, brain tumors are still an important cause of cancer-related deaths in children. Prognosis is still highly dependent on clinical characteristics, such as the age of the patient, tumor type, stage, and localization, but increased knowledge about the genetic and biological features of these tumors is being obtained and might be useful to further improve outcome for these patients. It has become clear that the deregulation of signaling pathways essential in brain development, for example, sonic hedgehog (SHH), Wnt, and Notch pathways, plays an important role in pathogenesis and biological behavior, especially for medulloblastomas. More recently, data have become available about the cells of origin of brain tumors and the possible existence of brain tumor stem cells. Newly developed array-based techniques for studying gene expression, protein expression, copy number aberrations, and epigenetic events have led to the identification of other potentially important biological abnormalities in pediatric medulloblastomas and ependymomas. Copyright 2008 by the Society for Neuro-Oncology
Decreased PARP and procaspase-2 protein levels are associated with cellular drug resistance in childhood acute lymphoblastic leukemia
Drug resistance in childhood acute lymphoblastic leukemia (ALL) and acute
myeloid leukemia (AML) is associated with impaired ability to induce
apoptosis. To elucidate causes of apoptotic defects, we studied the
protein expression of Apaf-1, procaspases-2, -3, -6, -7, -8, -10, and
poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) in cells from
children with acute lymphoblastic leukemia (ALL; n = 43) and acute myeloid
leukemia (AML; n = 10). PARP expression was present in all B-lineage
samples, but absent in 4 of 15 T-lineage ALL samples and 3 of 10 AML
cases, which was not caused by genomic deletions. PARP expression was a
median 7-fold lower in T-lineage ALL (P < .001) and 10-fold lower in AML
(P < .001) compared with B-lineage ALL. PARP expression was 4-fold lower
in prednisolone, vincristine and L-asparaginase (PVA)-resistant compared
with PVA-sensitive ALL patients (P < .001). Procaspase-2 expression was
3-fold lower in T-lineage ALL (P = .022) and AML (P = .014) compared with
B-lineage ALL. In addition, procaspase-2 expression was 2-fold lower in
PVA-resistant compared to PVA-sensitive ALL patients (P = .042). No
relation between apoptotic protease-activating factor 1 (Apaf-1),
procaspases-3, -6, -7, -8, -10, and drug resistance was found. In
conclusion, low baseline expression of PARP and procaspase-2 is related to
cellular drug resistance in childhood acute lymphoblastic leukemia
Correlation between clinical course and quantitative analysis of the ischemia related artery in patients with unstable angina pectoris, refractory to medical treatment
Patients with unstable angina, refractory to intensive medical therapy, are at high risk for developing thrombotic complications, such as recurrent ischemia, myocardial infarction and coronary occlusion during coronary angioplasty. As both platelet ag
Inhibition of glycolysis modulates prednisolone resistance in acute lymphoblastic leukemia cells
Treatment failure in pediatric acute lymphoblastic leukemia (ALL) is related to cellular resistance to glucocorticoids (eg, prednisolone). Recently, we demonstrated that genes associated with glucose metabolism are differentially expressed between prednisolone-sensitive and prednisolone-resistant precursor B-lineage leukemic patients. Here, we show that prednisolone resistance is associated with increased glucose consumption and that inhibition of glycolysis sensitizes prednisolone-resistant ALL cell lines to glucocorticoids. Treatment of prednisolone-resistant Jurkat and Molt4 cells with 2-deoxy-D-glucose (2-DG), lonidamine (LND), or3-bromopyruvate (3-BrPA) increased the in vitro sensitivity to glucocorticoids, while treatment of the prednisolone-sensitive cell lines Tom-1 and RS4; 11 did not influence drug cyto-toxicity. This sensitizing effect of the glycolysis inhibitors in glucocorticoid-resistant ALL cells was not found for other classes of antileukemic drugs (ie, vincris-tine and daunorubicin). Moreover, down-regulation of the expression of GAPDH by RNA interference also sensitized to prednisolone, comparable with treatment with glycolytic inhibitors. Importantly, the ability of 2-DG to reverse glucocorticoid resistance was not limited to cell lines, but was also observed in isolated primary ALL cells from patients. Together, these findings indicate the importance of the glycolytic pathway in glucocorticoid resistance in ALL and suggest that targeting glycolysis is a viable strategy for modulating prednisolone resistance in ALL
A U-HPLC-ESI-MS/MS-based stable isotope dilution method for the detection and quantitation of methotrexate in plasma
INTRODUCTION: High-dose methotrexate (MTX) is used in the treatment of proliferative diseases such as acute lymphoblastic leukemia. Therapeutic drug monitoring of plasma MTX is important to monitor efficacy and adverse events. The authors aimed to develop a liquid chromatography, electrospray ionization, tandem mass spectrometry (LC-ESI-MS/MS)-based method to determine MTX in plasma for therapeutic drug monitoring and pharmacokinetic studies. METHODS: Samples were analyzed using a Waters Acquity UPLC and Quattro Premier XE. A Waters Acquity UPLC BEH C18 column (2.1 mm x 100 mm, 1.7 μm) was used running an isocratic mobile phase of 21% methanol and 10 mM ammonium bicarbonate. The electrospray was operated in the positive ionization mode monitoring the following mass transitions: m/z 455.2 > 308.2 for MTX and m/z 458.2 > 311.2 for MTXd3. The analysis combined straightforward sample preparation, consisting of dilution and protein precipitation, with a 3-minute run time. RESULTS: The method was linear up to 50 μM (r > 0.99), and the coefficient of variation was 1:10, was 5 nM. Method comparison with the Abbott TDx fluorescent polarization immunoassay (FPIA) showed excellent agreement, and a small but significant negative constant bias was detected (LC-MS/MS = 0.98 x FPIA - 7.3). CONLUSIONS: The authors developed a specific and sensitive stable isotope dilution LC-ESI-MS/MS method to monitor MTX concentrations in plasma within the clinically relevant range. The method can be easily applied in clinical laboratories because it combines straightforward sample pretreatment with LC-MS/MS. Copyrigh
Asparagine synthetase expression is linked with L-asparaginase resistance in TEL-AML1-negative but not TEL-AML1-positive pediatric acute lymphoblastic leukemia
Resistance to L-asparaginase in leukemic cells may be caused by an
elevated cellular expression of asparagine synthetase (AS). Previously, we
reported that high AS expression did not correlate to L-asparaginase
resistance in TEL-AML1-positive B-lineage acute lymphoblastic leukemia
(ALL). In the present study we confirmed this finding in TEL-AML1-positive
patients (n = 28) using microarrays. In contrast, 35
L-asparaginase-resistant TEL-AML1-negative B-lineage ALL patients had a
significant 3.5-fold higher AS expression than 43 sensitive patients (P <
.001). Using real-time quantitative polymerase chain reaction (RTQ-PCR),
this finding was confirmed in an independent group of 39 TEL-AML1-negative
B-lineage ALL patients (P = .03). High expression of AS was associated
with poor prognosis (4-year probability of disease-free survival [pDFS]
58% +/- 11%) compared with low expression (4-year pDFS 83% +/- 7%; P =
.009). We conclude that resistance to l-asparaginase and relapse risk are
associated with high expression of AS in TEL-AML1-negative but not
TEL-AML1-positive B-lineage ALL
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