51 research outputs found
Novel genomic determinants of apoptotic defects in acute lymphoblastic leukemia
The treatment of pediatric acute leukemia has greatly improved over the past 4 decades,
resulting in long-term disease-free survival of approximately 80% for ALL1-3 and 60% for
AML.4 Despite this progress, a considerable number of children ultimately relapse with a
disease that is highly refractory to further treatment. A high proportion of the contemporary
treatment failures can be contributed to cellular drug resistance. However, relatively little is
known about the causes of cellular drug resistance in childhood acute leukemia.
In the last years it has become clear that most, if not all, chemotherapeutic agents
ultimately induce programmed cell death or apoptosis in their target cells.5 Defects in the
apoptosis route allow genetically instable cells to survive and are thought of as one of the
major driving forces behind leukemogenesis.6,7 These observations led to the hypothesis
that aberrations in the apoptosis pathway contribute to cellular drug resistance in children
with acute leukemia. Therefore, a thorough knowledge of the aberrations in the apoptosis
route is critical for understanding the causes of treatment failure and for a rational
approach to drug design and therapy
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
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
Asparagine synthetase expression is linked with L-asparaginase resistance in TEL-AML1-negative but not TEL-AML1-positive pediatric acute lymphoblastic leukemia
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