32 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
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
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
Alternative trafficking of Weibel-Palade body proteins in CRISPR/Cas9-engineered von Willebrand factor-deficient blood outgrowth endothelial cells
Background: Synthesis of the hemostatic protein von Willebrand factor (VWF) drives
formation of endothelial storage organelles called WeibelâPalade bodies (WPBs). In
the absence of VWF, angiogenic and inflammatory mediators that are costored in
WPBs are subject to alternative trafficking routes. In patients with von Willebrand
disease (VWD), partial or complete absence of VWF/WPBs may lead to additional
bleeding complications, such as angiodysplasia. Studies addressing the role of VWF
using VWD patientâderived blood outgrowth endothelial cells (BOECs) have reported
conflicting results due to the intrinsic heterogeneity of patientâderived BOECs.
Objective: To generate a VWFâdeficient endothelial cell model using clustered regularly interspaced short palindromic repeats (CRISPR) genome engineering of blood
outgrowth endothelial cells.
Methods: We used CRISPR/CRISPRâassociated protein 9 editing in singleâdonor
cord bloodâderived BOECs (cbBOECs) to generate clonal VWFâ/â cbBOECs. Clones
were selected using highâthroughput screening, VWF mutations were validated by
sequencing, and cells were phenotypically characterized.
Results: Two VWFâ/â BOEC clones were obtained and were entirely devoid of WPBs,
while their overall cell morphology was unaltered. Several WPB proteins, including
CD63, syntaxinâ3 and the cargo proteins angiopoietin (Ang)â2, interleukin (IL)â6, and
ILâ8 showed alternative trafficking and secretion in the absence of VWF. Interestingly,
Angâ2 was relocated to the cell periphery and colocalized with Tieâ2.
Conclusions: CRISPR editing of VWF provides a robust method to create VWFâ deficient BOECs that can be directly compared to their wildâtype counterparts. Results obtained with our model system confirmed alternative trafficking of several WPB
proteins in the absence of VWF and support the theory that increased Angâ2/Tieâ2
interaction contributes to angiogenic abnormalities in VWD patients