|
|
 Previous Article | Table of Contents | Next Article 
Blood, Vol. 91 No. 6 (March 15), 1998:
pp. 2092-2098
Relationship Between Major Vault Protein/Lung Resistance Protein,
Multidrug Resistance-Associated Protein, P-Glycoprotein Expression,
and Drug Resistance in Childhood Leukemia
By
M.L. den Boer,
R. Pieters,
K.M. Kazemier,
M.M.A. Rottier,
C.M. Zwaan,
G.J.L. Kaspers,
G. Janka-Schaub,
G. Henze,
U. Creutzig,
R.J. Scheper, and
A.J.P. Veerman
From the Departments of Pediatric Hematology/Oncology and Pathology,
University Hospital Vrije Universiteit, Amsterdam, The Netherlands; the
COALL Study Group, Hamburg, Germany; the ALL-REZ BFM Group, Berlin,
Germany; and the AML-BFM Group, Münster, Germany.
 |
ABSTRACT |
Cellular drug resistance is related to a poor prognosis in childhood
leukemia, but little is known about the underlying mechanisms. We
studied the expression of P-glycoprotein (P-gp), multidrug resistance
(MDR)-associated protein (MRP), and major vault protein/lung resistance
protein (LRP) in 141 children with acute lymphoblastic leukemia (ALL)
and 27 with acute myeloid leukemia (AML) by flow cytometry. The
expression was compared between different types of leukemia and was
studied in relation with clinical risk indicators and in vitro
cytotoxicity of the MDR-related drugs daunorubicin (DNR), vincristine
(VCR), and etoposide (VP16) and the non-MDR-related drugs prednisolone
(PRD) and L-asparaginase (ASP). In ALL, P-gp, MRP, and LRP expression
did not differ between 112 initial and 29 unrelated relapse samples nor
between paired initial and relapse samples from 9 patients. In multiple
relapse samples, LRP expression was 1.6-fold higher compared with both
initial (P = .026) and first relapse samples (P = .050), which was not observed for P-gp and MRP. LRP expression was
weakly but significantly related to in vitro resistance to DNR
(Spearman's rank correlation coefficient 0.25, P = .016) but
not to VCR, VP16, PRD, and ASP. No significant correlations were found
between P-gp or MRP expression and in vitro drug resistance. Samples
with a marked expression of two or three resistance proteins did not
show increased resistance to the tested drugs compared with the
remaining samples. The expression of P-gp, MRP, and LRP was not higher
in initial ALL patients with prognostically unfavorable
immunophenotype, white blood cell count, or age. The expression of P-gp
and MRP in 20 initial AML samples did not differ or was even lower
compared with 112 initial ALL samples. However, LRP expression was
twofold higher in the AML samples (P < .001), which are more
resistant to a variety of drugs compared with ALL samples. In
conclusion, P-gp and MRP are unlikely to be involved in drug resistance
in childhood leukemia. LRP might contribute to drug resistance but only
in specific subsets of children with leukemia.
| |
INTRODUCTION |
CELLULAR DRUG RESISTANCE is related to a
high risk of treatment failure in childhood leukemia. For example,
children with acute lymphoblastic leukemia (ALL) with in vitro
drug-resistant leukemic cells have a poorer prognosis compared to
patients with relatively sensitive cells at initial
diagnosis.1,2 Furthermore, leukemic cells of children with
acute myeloid leukemia (AML) are in vitro more resistant to several
drugs compared with cells of ALL patients.3
Knowledge about mechanisms of multidrug resistance (MDR) in clinical
samples is limited, and studies have mainly focussed on the expression
of P-glycoprotein (P-gp). P-gp is a transmembrane protein encoded by
the MDR1 gene, which transports anthracyclines, vinca
alkaloids, and epipodophyllotoxins out of the cell. In contrast to
adult leukemia, contradictory results have been reported about the
clinical relevance of P-gp in childhood leukemia; in some studies, P-gp
expression was higher at relapse compared with initial leukemias4-7 or was related to long-term survival or
relapse risk,8,9 whereas in other studies no such
associations were found.10-12
Another drug-efflux pump is the MDR-associated protein
(MRP).13 Cell lines in which the MRP gene has been
deleted were more sensitive to the anthracyclines, vinca alkaloids, and
epipodophyllotoxins, whereas the response to cytosine arabinoside
remained unchanged.14 In adult AML, differences in MRP
expression between initial and relapsed patients were
reported.6,15,16 Inconsistent results were found for the
relationship between MRP expression at initial diagnosis and response
to chemotherapy.15,17,18 Knowledge about MRP in childhood
leukemia is limited. Beck et al5 found no difference in MRP
mRNA levels between initial and first relapse ALL samples; however, the
expression was higher in multiple relapse ALL samples. MRP mRNA levels
were also higher in relapsed AML patients compared with initial
patients, but these data may be biased because samples from adults and
children were analyzed together.6 It is unknown whether the
expression of MRP is related to drug resistance and whether it is of
clinical importance in childhood leukemia.
The major vault protein/lung resistance protein (LRP) was initially
described in non-small-cell lung cancer cell lines that lacked
P-gp.19 Recently, it became evident that LRP is present in
a variety of human cancer cell lines that have not previously been
exposed to drugs. In these cell lines, the expression of LRP correlated
with intrinsic resistance to doxorubicin, vincristine, and platinum
compounds.20 LRP has been identified as the human homolog
of the rat major vault protein, which contributes to 70% of the mass
of vault particles.21 The function of these vaults has been
associated with nuclear-cytoplasmic transport,22 although direct evidence is lacking. Recently, the number of vaults was shown to
be elevated in drug-resistant cell lines.23 Information about the clinical relevance of LRP is limited. LRP expression has been
observed in advanced ovarium carcinoma, in melanoma, in non-small-cell
lung carcinoma, and in adult AML and CML.24-28 The
expression of LRP was related to a poor response to chemotherapy in
advanced ovarium carcinoma and adult AML.24,27 In childhood leukemia, the LRP expression and relevance to drug resistance are
unknown.
A pitfall in comparing data on resistance proteins is the use of
different techniques and different reference samples such as
drug-resistant cell lines and normal cells. A heterogeneous group of
patient samples may also limit the interpretation of and comparisons
between different studies, such as the use of pooled data of ALL and
AML and/or initial and relapse samples. Moreover, comparisons
between the expression of resistance proteins and response to
combination chemotherapy may underestimate the importance of the
protein in question as mechanism of resistance to a single drug. In the
present study, we determined the expression of P-gp, MRP, and the novel
LRP in a large series of childhood leukemia and normal cells using an
optimized and standardized flow cytometrical method.29 The
protein expression was compared between different types of leukemia and
was related to clinical risk indicators and to the in vitro
cytotoxicity of three MDR-related drugs, ie, daunorubicin (DNR),
vincristine (VCR), and etoposide (VP16), and two non-MDR-related
drugs, ie, prednisolone (PRD) and L-asparaginase (ASP), which
are all currently used in the treatment of childhood leukemia.
| |
MATERIALS AND METHODS |
Patient samples.
In this study, samples of 168 children with leukemia were examined for
resistance protein expression and in vitro drug cytotoxicity (148 fresh
and 20 cryopreserved samples). Bone marrow (BM) or peripheral blood
(PB) samples were collected from patients of the University Hospital
Vrije Universiteit (Amsterdam, The Netherlands) and of hospitals
participating in the COALL study group (initial ALL; Prof Dr G. Janka,
Hamburg, Germany), the ALL-REZ BFM group (relapsed ALL; Prof Dr G. Henze, Berlin, Germany), and the AML-BFM group (initial and relapsed
AML; Prof Dr U. Creutzig and Prof Dr J. Ritter, Münster,
Germany). BM and PB samples of 14 nonleukemic children and 3 adults
were used to determine the expression of resistance proteins in normal
cells. The leukemic patients were classified as follows: 112 initial
ALL, 29 relapsed ALL (22 with first relapse and 7 with second or later
relapse), 20 initial AML, and 7 relapsed AML (6 with first relapse and
1 second relapse). From 9 patients with ALL, paired samples could be
collected at initial diagnosis and at relapse. Within 24 hours of
sampling, the mononuclear cells were separated by Lymphoprep (density
1.077 g/mL; Nycomed Pharma, Oslo, Norway) centrifugation at
480g for 15 minutes at room temperature. The mononuclear cells
were collected and washed twice in RPMI 1640 (Dutch modification,
without L-glutamine; GIBCO BRL, Breda, The Netherlands) supplemented
with 1% heat-inactivated fetal calf serum (GIBCO BRL). The percentage
of leukemic cells in each sample was determined on cytospin
preparations stained with May-Grünwald-Giemsa (Merck, Darmstadt,
Germany). When necessary, the percentage of leukemic cells in the
sample has been enriched to greater than 80% using monoclonal
antibodies linked to magnetic beads (DynaBeads; Dynal, Oslo, Norway) as
described previously.30 The immunophenotypes were
determined at the central laboratories of the above-mentioned study
groups or at the research laboratory of Pediatric Hematology/Oncology,
University Hospital Vrije Universiteit. Precursor B-lineage ALL was
defined by terminal deoxynucleotidyl transferase
(TdT)+/CD19+ and T-lineage ALL by
TdT+/cytoplasmic CD3+/CD7+.
Precursor B-lineage ALL was further subdivided into proB
(CD10 /cytoplasmic µ chain
[cµ]), common
(CD10+/cµ), and preB (CD10+ or
/cµ+).
Antibodies.
P-gp was detected by the monoclonal antibodies C219 (intracellular
epitope; Centocor Diagnostics, Malvern, PA) and MRK16 (extracellular; Kamiya Biomedical Co, Thousand Oaks, CA), which are both mouse IgG2a
antibodies. MRP was detected by MRPm6 (intracellular, mouse IgG1) and
MRPr1 (presumably intracellular, rat IgG2a).31,32 LRP56
(intracellular, mouse IgG2b) was used to determine LRP
expression.19 As a positive control, DNA-42 was used
(intracellular, mouse IgG2a), which recognizes dsDNA (kindly provided
by Dr R. Smeenk, Central Laboratory of Blood Transfusion [CLB],
Amsterdam, The Netherlands). Nonspecific isotype-matched antibodies
(Dako, Glostrup, Denmark) and omission of the primary antibody were
used as negative controls.
Detection of resistance proteins by flow cytometry.
Cells in suspension were fixed using 2% (vol/vol) 37% formaldehyde
solution in 100% acetone incubated for 10 seconds at room temperature
before incubation with C219, MRK16, MRPr1, and LRP56. For MRPm6, cells
were fixed in 100% methanol for 15 minutes at  20°C. These
fixation methods resulted in optimal staining intensities and
reproducibility of staining, as described elsewhere.29
After fixation, cells were washed twice with phosphate-buffered saline supplemented with 0.1% bovine serum albumin (Organon Teknika, Boxtel,
The Netherlands) and centrifuged at 4°C (480g for 5 minutes). Purified human Ig (CLB) that contained greater than 90% IgG
was used to reduce the background staining especially observed for IgG2a isotypic antibodies in AML samples. To this aim, AML cells were
incubated with 0.6% human Ig for 30 minutes on ice and subsequently washed. Blocking of ALL samples with human Ig had no effect on the
intensity of the IgG2a isotypic control, because background staining
was already low in ALL cells. Next, 0.15 × 106 cells
were incubated with the primary antibody for 45 minutes, washed, and
incubated with fluorescein isothiocyanate (FITC)-conjugated rabbit
antimouse (RAM) F(ab )2 or rabbit antirat (RAR)
antibodies (Dako) for 30 minutes at room temperature. The final
antibody concentrations used were 10 µg/mL C219, 5 µg/mL MRK16, 10 µg/mL MRPm6, 1.7 µg/mL MRPr1, 0.6 µg/mL LRP56, 0.2 µg/mL
DNA-42, 1:50 FITC-RAM-F(ab)2, and 1:500 FITC-RAR.
Isotypic control antibodies were tested using the same fixative and the
same IgG concentration as the specific antibodies. The amount of
FITC-labeling was detected by flow cytometry using the 488 nm line of
an argon laser (FACScan; Becton Dickinson, Erembodegem, Belgium). Green
fluorescence was collected through a 530/30 nm bandpass filter set,
using a log mode amplification (FL-1 height). The flow cytometry data
were analyzed using LYSYS II software (Becton Dickinson). Leukemic cells were gated based on forward and sideward scatter characteristics, and the fluorescence intensity of this population was expressed in
arbitrary units on a log-scale. As a measure for the intensity of
staining, the fluorescence index (FI) was used, which represents the
ratio between the mean fluorescence intensity of cells stained with the
specific antibody and that of cells stained with the isotype-matched
control antibody. No difference in the expression of resistance
proteins was observed between fresh and cryopreserved samples or
between BM and PB samples (both paired and unpaired samples).
Therefore, the data were pooled for further analysis.
In vitro drug cytotoxicity assay.
The MTT assay was used to determine the in vitro cytotoxicity of DNR
(Cerubidine, Rhône-Poulenc Rorer, Amstelveen, The Netherlands), VCR (Oncovin; Eli Lilly, Amsterdam, The Netherlands), VP16 (Vepesid; Bristol Myers, Weesp, The Netherlands), PRD (Bufa Pharmaceutical Products, Uitgeest, The Netherlands), and ASP (Medac, Hamburg, Germany). The assay conditions were essentially the same as described before.30,33,34 To summarize the test principles, cells
were cultured in 96-well plates in the absence (control) or presence of
a drug. Each drug was tested at six different concentrations in
duplicate. After 4 days of culture at 37°C in humidified air containing 5% CO2, 50 µg
3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide (MTT;
Sigma, St Louis, MO) was added to each well. Subsequently,
cells were incubated with MTT for 6 hours at 37°C. In this period,
viable cells can reduce the yellow MTT molecules resulting in a purple
formazan product. The formazan crystals were dissolved using acidified
(0.04 mol/L HCl) isopropanol, and the quantity of reduced product was
measured spectrophotometrically at 562 nm (Bio-Kinetics Reader; Bio-Tek
Instruments, Winooski, VT). The optical density value (OD) at 562 nm is
linearly related to the amount of viable cells in both ALL and AML
samples.33,34 Reproducible test results were obtained when,
after 4 days of culture, the control wells without drug contained
greater than 70% leukemic cells and the OD of these wells (adjusted
for blank values) was higher than 0.050 arbitrary
units.30,35 When a sample met these criteria, the leukemic
cell survival (LCS) at each drug concentration was calculated by the
equation: LCS = (OD drug-containing well/OD wells without
drug) × 100% (after subtraction of blank values). The drug
concentration lethal to 50% of the cells, ie, the LC50 value, was used
as measure for the in vitro drug cytotoxicity. In this study, as in
others,33,34 no difference in LC50 values was observed
between fresh and cryopreserved cells or between BM and PB samples.
Hence, these data were pooled for further analysis.
Statistics.
Differences in the distribution of FI's and LC50 values between
unpaired samples were analyzed using the Mann-Whitney U test adjusted
for tied ranks. Data of paired samples were analyzed by the Wilcoxon
matched pair test. Correlation coefficients were calculated using the
Spearman's rank correlation coefficient (Rs). The t-test has
been used for significance testing of Rs. A P value  .05 was
considered statistically significant (two-tailed tested).
| |
RESULTS |
Expression of resistance proteins in ALL and AML.
Table 1 summarizes the expression of P-gp,
MRP, and LRP in all patients tested, ie, 112 initial ALL, 29 relapsed
ALL, 20 initial AML, and 7 relapsed AML patients. The FI of P-gp, MRP, and LRP did not significantly differ between ALL samples taken at
initial diagnosis and at (unrelated) relapse. However, the median FI of
LRP in multiple relapse samples was 1.6-fold higher compared with
samples taken at initial diagnosis or at first relapse of ALL
(P = .026 and P = .050, respectively;
Fig 1). This difference was not found for
P-gp and MRP.
View larger version (16K):
[in this window]
[in a new window]
| Fig 1.
Expression of LRP in initial and relapsed childhood ALL.
The median FI of each group is depicted by a square; the upper and lower diamonds represent the 75th and 25th percentile, respectively. Data are based on 112 initial, 22 first relapse (1st), and 7 multiple relapse ( 2nd) samples. The difference between the FI of multiple relapse samples and initial or first relapse samples is significant (P = .026 and P = .050, respectively).
|
|
Figure 2 shows the FI of the resistance
proteins in paired samples taken at initial diagnosis and at relapse of
9 children with ALL. No significant differences between initial and
relapse samples were found: both increased and decreased expression of P-gp, MRP, and LRP occurred at relapse.
View larger version (26K):
[in this window]
[in a new window]
| Fig 2.
Expression of resistance proteins in samples taken both
at initial diagnosis (I) and at relapse (R) of the same patients. Depicted are the FI for P-gp, MRP, and LRP using, respectively, MRK16
(n = 7), MRPr1 (n = 8), and LRP56 (n = 9). Each patient is
indicated by the same symbol for each resistance protein. Differences in FI are not significant.
|
|
In AML patients, the FI of P-gp and MRP did not differ between initial
and relapsed patients, but the FI of LRP was lower in the 7 relapse
samples tested (P = .041). The expression of resistance
proteins was compared between AML and ALL patients at initial diagnosis
(Table 1). The FI of P-gp using the C219 antibody did not differ
between AML and ALL patients, but the FI using MRK16 was median
1.7-fold lower in AML cells (P < .001). The FI of MRP was
slightly lower in AML compared with ALL for both the MRPm6 antibody
(median, 1.2-fold; P = .007) and the MRPr1 antibody (median,
1.2-fold; P = .010). AML cells expressed significantly more LRP
compared with ALL cells (median, 2.0-fold; P < .001). The
unexpectedly lower detection of P-gp using MRK16 in AML samples could
not be explained by the blocking procedure before incubation with IgG2a
isotypic antibodies, because this decreased the signal of both the
isotypic control and the specific antibody to the same extent.
The expression of P-gp, MRP, and LRP was also studied in normal cells
(Table 1). For P-gp, the FI using C219 or MRK16 was comparable between
normal PB lymphocytes and initial ALL cells. The detection of MRP by
MRPm6 showed a slightly lower FI in normal lymphocytes compared with
initial ALL patients (P = .008), which was not found for MRPr1.
For LRP, the median FI was 2.6-fold higher in PB lymphocytes compared
with initial ALL patients (P < .001). The expression of
resistance proteins in normal BM cells was studied in only 3 samples.
In Table 1, these results are included to give an indication for the
expression levels of the resistance proteins in these cells.
Correlation between expression of resistance proteins and
immunophenotype, white blood cell count (WBC), and age in childhood
ALL.
ALL patients at initial diagnosis were classified by immunophenotype as
proB (n = 2), common/preB (n = 90), and T-ALL (n = 20). The expression
of the resistance proteins in common/preB and T-ALL patients is shown
in Table 2. The expression of P-gp using
C219 was 1.3-fold lower in T-ALL compared with common/preB samples
(P = .001), whereas for MRK16 no significant difference was
found. The median FI using MRPr1 was slightly higher in T-ALL compared
with common/preB ALL patients (median, 1.2-fold; P < .001),
which was not found using MRPm6. The median FI of LRP was 1.4-fold
lower in T-ALL compared with common/preB ALL patients (P < .001).
View this table:
[in this window]
[in a new window]
|
Table 2.
Correlation Between Expression of Resistance Proteins
and Immunophenotype, WBC, and Age in Childhood ALL at Initial
Diagnosis
|
|
Initial ALL patients were subgrouped by WBC and age using the risk
group stratification criteria of the COALL-92 study (Table 2). The
expression of P-gp, MRP, and LRP was comparable between children with a
WBC less than 25/nL and those with a WBC 25/nL. The expression of MRP
and LRP did also not differ between children with an age between 12 and
120 months and those older than 120 months. P-gp detected by C219 was
1.3-fold lower in the oldest group (P = .016), whereas for
MRK16 this difference was not found. Within the group of common/preB
ALL patients, the expression of P-gp, MRP, and LRP was not related to
WBC and age.
Comparison between the expression of resistance proteins and in vitro
drug cytotoxicity.
AML patients were more resistant to DNR (median, 1.7-fold; P < .001), VCR (median, 4-fold; P = .015), and PRD (median,
>800-fold; P < .001) but not to VP16 and ASP compared with
ALL patients. The FI of LRP correlated weakly with the cytotoxicity of
DNR in ALL (Rs, 0.25; P = .016) but not in AML samples. No
significant correlation was found between LRP and the cytotoxicity of
the other 4 drugs. Neither in ALL samples nor in AML samples was the expression of P-gp and MRP correlated with the LC50 values of DNR, VCR,
VP16, PRD, or ASP. One exception was found for the FI using MRPm6 in
ALL samples, which was weakly related to the LC50 value of VP16 (Rs,
0.22; P = .038).
The FI for P-gp using C219 was weakly related to the FI using MRK16
(Rs, 0.30; P < .001). The cytotoxicity of DNR, VCR, VP16, PRD, or Asp did not differ between patients with the highest and lowest
FI for both antibodies. For MRP, the FI using MRPm6 was not
significantly related to the FI using MRPr1, and no difference in in
vitro drug cytotoxicity was observed between patients with the highest
and lowest FI for both antibodies.
A resistance protein profile was made of each ALL patient by combining
the results obtained using MRK16, MRPr1, and LRP56. Samples with an FI
higher than the median FI were defined positive for the protein in
question. The cytotoxicity of DNR, VCR, VP16, PRD, or ASP did not
differ between samples that were positive for two or three of the
proteins and samples that were positive for one or none of the
proteins.
| |
DISCUSSION |
The expression of P-gp, MRP, and LRP was studied in childhood ALL and
AML and was related to different risk indicators (initial or relapse,
immunophenotype, WBC, and age) and to in vitro cytotoxicity of three
MDR-related drugs, ie, DNR, VCR, and VP16, and two non-MDR-related drugs, ie, PRD and ASP. In earlier studies we showed that resistance to
these drugs was related to the above-mentioned risk indicators, eg, (1)
relapsed ALL patients were more resistant to DNR, PRD, and ASP but not
to VCR and VP16 compared with patients at initial diagnosis36; (2) T-ALL patients were more resistant to DNR,
VCR, PRD, and ASP compared with common/preB ALL
patients37,38; and (3) AML patients were more resistant to
VCR and PRD than ALL patients.3 In the present study, AML
patients were also significantly more resistant to DNR compared with
ALL patients (median, 1.7-fold).
P-gp expression was studied using two antibodies, ie, C219 and MRK16.
The FI using C219 was only weakly related to the FI using MRK16, which
has also been observed in other studies.39,40 The lack of
consensus between both antibodies may be explained by the fact that
C219 binds to a cytoplasmic epitope and recognizes both MDR1 and MDR3
products, whereas MRK16 binds to an external epitope and is specific
for MDR1 products.41-43 Irrespective of which antibody was
used, we found no evidence that P-gp expression is an important
mechanism of drug resistance in childhood leukemia. (1) No difference
was found in P-gp expression between initial and relapsed patients. (2)
Expression did not clearly differ between risk groups of patients
identified by immunophenotype, WBC, or age. (3) Expression did not
differ or was even lower in initial AML compared with ALL samples. (4)
Expression of P-gp in normal lymphocytes was comparable with the
expression of ALL samples. (5) No association between P-gp expression
and cytotoxicity of both MDR and non-MDR-related drugs was found. The
lower expression of P-gp in childhood AML samples has also been
demonstrated by others; Beck et al44 showed that the
MDR1/P-gp mRNA levels were lower in initial AML samples compared with
initial ALL and normal BM cells. These levels were increased in
relapsed AML and in second or later relapsed ALL, which was not found
at the protein level in the present study. In an earlier study, we
already showed that the resistance modifiers verapamil and cyclosporin
A had no effect on the accumulation and cytotoxicity of DNR and VCR in
childhood ALL.11 In summary, our data do not suggest that
P-gp expression is related to drug resistance in childhood ALL and AML.
Although some studies showed that P-gp expression may be related to a
poor prognosis,8,9 other studies10-12 and the
present data give no indication that P-gp is clinically important in
childhood leukemia.
Another transporter protein that might contribute to drug resistance in
leukemia is MRP. Recently, besides MRP (now called MRP-1), at least 4 other homologs of this protein have been identified.45 It
is unknown yet whether these homologs are also related to multidrug resistance. Sequence analysis showed that the protein segment used to
generate the MRPm6 antibody was derived from the most homologous
portion located in the C-terminal part of MRP. In contrast, a more
MRP-1-specific segment in the N-terminal part of the protein was used
for the MRPr1 antibody. This may explain the absence of a significant
correlation between the FI using MRPm6 and MRPr1 in our study.
Irrespective of which antibody was used, no difference between initial
and relapse ALL samples was observed neither compared with the first
nor with multiple relapse samples. The latter is in contrast with a
study of Beck et al,5 who observed elevated MRP mRNA levels
in multiple relapse ALL samples. In our study, the MRP expression was
not related to the in vitro cytotoxicity of DNR, VCR, PRD, and ASP. A
weak correlation was found between VP16 and the FI using MRPm6 in ALL
cells; however, this may not be specific for the resistance-associated
MRP-1 homolog, because this relationship was not found using MRPr1.
T-ALL cells have a slightly higher expression of MRP compared with
precursor B-lineage, but it is unlikely that this small difference can
explain the resistance to drugs observed in T-ALL
samples.37,38 Moreover, this difference may be
lineage-specific, because normal T lymphocytes also express more MRP
than B lymphocytes.15,46 Also, in AML samples, we found no
evidence that MRP is involved in the resistance to drugs observed in
these patients. The expression of MRP in AML patients may be even lower
than in ALL patients. Based on these data, it is unlikely that
expression of the MRP protein is an important mechanism of drug
resistance in childhood leukemia. In other tumor types, MRP may be more
important, eg, a high frequency of MRP positivity has been associated
with a poor clinical outcome in childhood
neuroblastoma.47,48
LRP has been identified as the major component of vaults, which are
large ribonucleoprotein particles.21 Approximately 5% of
the vaults is associated with the nuclear membrane and nuclear pore
complex, but the majority of vaults are located in the
cytoplasm.22,49 Knowledge about the role of LRP and vaults
in drug resistance is still very limited. Recently, the number of
vaults has been shown to be increased in non-P-gp MDR cell lines
compared with parental cell lines.23 Although direct
evidence is lacking, vaults may contribute to drug resistance by
redistributing the drug from the nucleus (drug target) to the
cytoplasm. This may explain the lower nuclear-cytoplasmic ratio that
was found for doxorubicin in LRP-expressing SW1573/2R120 cells compared
with LRP-negative parental cells.19,50 LRP/vaults may also
be involved in the sequestration of drugs into vesicles. This may
explain the granular staining of LRP found in drug-resistant cell
lines, which we and others also observed in leukemic cells using
immunocytochemistry (data not shown).19,27 Recently, LRP
expression has been related to a poor response to chemotherapy in
advanced ovarium carcinoma and adult AML.24,27 In the
present study, the expression of LRP was weakly but significantly
related to in vitro resistance to DNR in childhood ALL, whereas no
significant relationship was found between LRP and the other 4 drugs
tested. This illustrates the multifactorial phenomenon of drug
resistance; one protein cannot explain resistance to a variety of drugs
in all patients. In this respect, drug resistance in T-ALL samples
cannot be explained by elevated LRP expression, indicating that other
mechanisms should be more important in these cells; eg, an increased
expression or activity of glutathione-S-transferases, elevated levels
of glutathione, and inhibition of (CD95-mediated)
apoptosis.51-54 In AML patients, LRP expression did not
correlate with the cytotoxicity of DNR or the other drugs. However, it
should be noticed that expression of LRP in initial AML cells, as well
as in multiple relapse ALL cells and normal PB lymphocytes, was higher
compared with initial ALL cells, all being more resistant to DNR and
other drugs compared with ALL cells.3,33,36
In clinical practice, children with leukemia receive a multiagent
chemotherapy including corticosteroids, vinca alkaloids, L-asparaginase, antimetabolites, anthracyclines, and
epipodophyllotoxins. Treatment failures may be related to the cellular
resistance to one or more classes of drugs and to the pharmacokinetics
of drugs in each patient. In the present study, we showed that P-gp and MRP are not related to any of the poor-risk indicators and cellular resistance to MDR and non-MDR-related drugs, whereas LRP may
contribute to drug (DNR) resistance in subsets of
poor-risk patients in childhood leukemia. Further studies are warranted
to address the functional role of LRP in cellular drug resistance and
its relationship with clinical outcome in childhood leukemia.
| |
FOOTNOTES |
Submitted July 18, 1997;
accepted November 10, 1997.
Supported by Dutch Cancer Society Grant No. VU 93-641.
Address reprint requests to M.L. den Boer, Department of Pediatric
Hematology/Oncology, University Hospital Vrije Universiteit, PO Box
7057, 1007 MB Amsterdam, The Netherlands.
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. section
1734 solely to indicate this fact.
| |
ACKNOWLEDGMENT |
The authors thank the members of the German COALL study group, ALL-REZ
BFM group, and the AML-BFM group for providing the leukemic samples.
| |
REFERENCES |
1.
Pieters R,
Huismans DR,
Loonen AH,
Hählen K,
Van der Does-van den Berg A,
Van Wering ER,
Veerman AJP:
Relation of cellular drug resistance to long-term clinical outcome in childhood acute lymphoblastic leukaemia.
Lancet
338:399,
1991[Medline]
[Order article via Infotrieve]
2.
Kaspers GJL,
Veerman AJP,
Pieters R,
Van Zantwijk CH,
Smets LA,
Van Wering ER,
Van der Does-van den Berg A:
In vitro cellular drug resistance and prognosis in newly diagnosed childhood acute lymphoblastic leukemia.
Blood
90:2723,
1997[Abstract/Free Full Text]
3.
Kaspers GJL,
Kardos G,
Pieters R,
Van Zantwijk CH,
Klumper E,
Hählen K,
De Waal FC,
Van Wering ER,
Veerman AJP:
Different cellular drug resistance profiles in childhood lymphoblastic and non-lymphoblastic leukemia: A preliminary report.
Leukemia
8:1224,
1994[Medline]
[Order article via Infotrieve]
4.
Tafuri A,
Sommaggio A,
Burba L,
Albergoni MP,
Petrucci MT,
Mascolo MG,
Testi AM,
Basso G:
Prognostic value of rhodamine-efflux and MDR-1/P-170 expression in childhood acute leukemia.
Leuk Res
19:927,
1995[Medline]
[Order article via Infotrieve]
5.
Beck J,
Handgretinger R,
Dopfer R,
Klingebiel T,
Niethammer D,
Gekeler V:
Expression of mdr1, mrp, topoisomerase II / , and cyclin A in primary or relapsed states of acute lymphoblastic leukaemias.
Br J Haematol
89:356,
1995[Medline]
[Order article via Infotrieve]
6.
Beck J,
Handgretinger R,
Klingebiel T,
Dopfer R,
Schaich M,
Ehninger G,
Niethammer D,
Gekeler V:
Expression of PKC isozyme and MDR-associated genes in primary and relapsed state AML.
Leukemia
10:426,
1996[Medline]
[Order article via Infotrieve]
7.
Ivy SP,
Olshefski RS,
Taylor BJ,
Patel KM,
Reaman GH:
Correlation of P-glycoprotein expression and function in childhood acute leukemia: A Children's Cancer Group study.
Blood
88:309,
1996[Abstract/Free Full Text]
8.
Sauerbrey A,
Zintl F,
Volm M:
P-glycoprotein and glutathione S-transferase  in childhood acute lymphoblastic leukaemia.
Br J Cancer
70:1144,
1994[Medline]
[Order article via Infotrieve]
9.
Goasguen JE,
Dossot JM,
Fardel O,
Le Mee F,
Le Gall E,
Leblay R,
LePrise PY,
Chapereon J,
Fauchet R:
Expression of the multidrug resistance-associated P-glycoprotein (P-170) in 59 cases of de novo acute lymphoblastic leukemia: Prognostic implications.
Blood
81:2394,
1993[Abstract/Free Full Text]
10.
Sievers EL,
Smith FO,
Woods WG,
Lee JW,
Bleyer WA,
Willman CL,
Bernstein ID:
Cell surface expression of the multidrug resistance P-glycoprotein (P-170) as detected by monoclonal antibody MRK-16 in pediatric acute myeloid leukemia fails to define a poor prognostic group: A report from the Childrens Cancer Group.
Leukemia
9:2042,
1995[Medline]
[Order article via Infotrieve]
11.
Pieters R,
Hongo T,
Loonen AH,
Huismans DR,
Broxterman HJ,
Hählen K,
Veerman AJP:
Different types of non-P-glycoprotein mediated multiple drug resistance in children with relapsed acute lymphoblastic leukaemia.
Br J Cancer
65:691,
1992[Medline]
[Order article via Infotrieve]
12.
Kingreen D,
Sperling C,
Notter M,
Schmidt C,
Diddens H,
Riehm H,
Thiel E,
Ludwig WD:
Sequential analysis of P-glycoprotein expression in childhood acute lymphoblastic leukemia.
Hematol Blood Transfus
34:23,
1992
13.
Cole SPC,
Bhardwaj G,
Gerlach JH,
Mackie JE,
Grant CE,
Almquist KC,
Stewart AJ,
Kurz EU,
Duncan AMV,
Deeley RG:
Overexpression of a transporter gene in a multidrug-resistant human lung cancer cell line.
Science
258:1650,
1992[Abstract/Free Full Text]
14.
Lorico A,
Rappa G,
Flavell RA,
Sartorelli AC:
Double knockout of the MRP gene leads to increased drug sensitivity in vitro.
Cancer Res
56:5351,
1996[Abstract/Free Full Text]
15.
Scheidner E,
Cowan KH,
Bader H,
Toomey S,
Schwartz GN,
Karp JE,
Burke PJ,
Kaufmann SH:
Increased expression of the multidrug resistance-associated protein gene in relapsed acute leukemia.
Blood
85:186,
1995[Abstract/Free Full Text]
16.
Hart SM,
Ganeshaguru K,
Hoffbrand AV,
Prentice HG,
Mehta AB:
Expression of the multidrug resistance-associated protein (MRP) in acute leukaemia.
Leukemia
8:2163,
1994[Medline]
[Order article via Infotrieve]
17.
Filipits M,
Suchomel RW,
Zöchbauer S,
Brunner R,
Lechner K,
Pirker R:
Multidrug resistance-associated protein in acute myeloid leukemia: No impact on treatment outcome.
Clin Cancer Res
3:1419,
1997[Abstract]
18.
Zhou DC,
Zittoun R,
Marie JP:
Expression of multidrug resistance-associated protein (MRP) and multidrug resistance (MDR1) genes in acute myeloid leukemia.
Leukemia
9:1661,
1995[Medline]
[Order article via Infotrieve]
19.
Scheper RJ,
Broxterman HJ,
Scheffer GL,
Kaaijk P,
Dalton WS,
Van Heijningen THM,
Van Kalken CK,
Slovak ML,
De Vries EGE,
Van der Valk P,
Meijer CJLM,
Pinedo HM:
Overexpression of a Mr 110,000 vesicular protein in non-P-glycoprotein-mediated multidrug resistance.
Cancer Res
53:1475,
1993[Abstract/Free Full Text]
20.
Izquierdo MA,
Shoemaker RH,
Flens MJ,
Scheffer GL,
Wu L,
Prather TR,
Scheper RJ:
Overlapping phenotypes of multidrug resistance among panels of human cancer-cell lines.
Int J Cancer
65:230,
1996[Medline]
[Order article via Infotrieve]
21.
Scheffer GL,
Wijngaard PLJ,
Flens MJ,
Izquierdo MA,
Slovak ML,
Pinedo HM,
Meijer CJLM,
Clevers HC,
Scheper RJ:
The drug resistance-related protein LRP is the human major vault protein.
Nat Med
1:578,
1995[Medline]
[Order article via Infotrieve]
22.
Kedersha NL,
Heuser JE,
Chugani DC,
Rome LH:
Vaults. III. Vault ribonucleoprotein particles open into flower-like structures with octagonal symmetry.
J Cell Biol
112:225,
1991[Abstract/Free Full Text]
23.
Kickhoefer V,
Rajavel K,
Scheffer G,
Dalton W,
Scheper R,
Rome L:
Multidrug resistant cancer cell lines contain elevated levels of vaults.
Proc Am Assoc Cancer Res
38:252,
1997
24.
Izquierdo MA,
Van der Zee AGJ,
Vermorken JB,
Van der Valk P,
Beliën JAM,
Giaccone G,
Scheffer GL,
Flens MJ,
Pinedo HM,
Kenemans P,
Meijer CJLM,
De Vries EGE,
Scheper RJ:
Drug resistance-associated marker Lrp for prediction of response to chemotherapy and prognoses in advanced ovarian carcinoma.
J Natl Cancer Inst
87:1230,
1995[Abstract/Free Full Text]
25.
Schadendorf D,
Makki A,
Stahr C,
Van Dyck A,
Wanner R,
Scheffer GL,
Flens MJ,
Scheper RJ,
Henz BM:
Membrane transport proteins associated with drug resistance expressed in human melanoma.
Am J Pathol
147:1545,
1995[Abstract]
26.
Dingemans AMC,
Van Ark-Otte J,
Van der Valk P,
Apolinario RM,
Scheper RJ,
Postmus PE,
Giaccone G:
Expression of the human major vault protein LRP in human lung cancer samples and normal lung tissues.
Ann Oncol
7:625,
1996[Abstract/Free Full Text]
27.
List AF,
Spier CS,
Grogan TM,
Johnson C,
Roe DJ,
Greer JP,
Wolff SN,
Broxterman HJ,
Scheffer GL,
Scheper RJ,
Dalton WS:
Overexpression of the major vault transporter protein lung-resistance protein predicts treatment outcome in acute myeloid leukemia.
Blood
87:2464,
1996[Abstract/Free Full Text]
28.
Michieli M,
Damiani D,
Ermacora A,
Raspadori D,
Michelutti A,
Grimaz S,
Fanin R,
Russo D,
Lauria F,
Masolini P,
Baccarani M:
P-glycoprotein (PGP) and lung resistance-related protein (LRP) expression and function in leukaemic cells.
Br J Haematol
96:356,
1997[Medline]
[Order article via Infotrieve]
29.
Den Boer ML,
Zwaan CM,
Pieters R,
Kazemier KM,
Rottier MMA,
Flens MJ,
Scheper RJ,
Veerman AJP:
Optimal immunocytochemical and flow cytometric detection of P-gp, MRP and LRP in childhood acute lymphoblastic leukemia.
Leukemia
11:1078,
1997[Medline]
[Order article via Infotrieve]
30.
Kaspers GJL,
Veerman AJP,
Pieters R,
Broekema GJ,
Huismans DR,
Kazemier KM,
Loonen AH,
Rottier MMA,
Van Zantwijk CH,
Hählen K,
Van Wering ER:
Mononuclear cells contaminating leukaemic samples tested for cellular drug resistance using the methyl-thiazol-tetrazolium assay.
Br J Cancer
70:1047,
1994[Medline]
[Order article via Infotrieve]
31.
Flens MJ,
Izquierdo MA,
Scheffer GL,
Fritz JM,
Meijer CJLM,
Scheper RJ,
Zaman GJR:
Immunochemical detection of the multidrug resistance-associated protein MRP in human multidrug-resistant tumor cells by monoclonal antibodies.
Cancer Res
54:4557,
1994[Abstract/Free Full Text]
32.
Bakos E,
Hegedüs T,
Holló Z,
Welker E,
Tusnády GE,
Zaman GJR,
Flens MJ,
Váradi A,
Sarkadi B:
Membrane topology and glycosylation of the human multidrug resistance-associated protein.
J Biol Chem
271:12322,
1996[Abstract/Free Full Text]
33.
Kaspers GJL,
Pieters R,
Van Zantwijk CH,
De Laat PAJM,
De Waal FC,
Van Wering ER,
Veerman AJP:
In vitro drug sensitivity of normal peripheral blood lymphocytes and childhood leukaemic cells from bone marrow and peripheral blood.
Br J Cancer
64:469,
1991[Medline]
[Order article via Infotrieve]
34.
Klumper E,
Pieters R,
Kaspers GJL,
Huismans DR,
Loonen AH,
Rottier MMA,
Van Wering ER,
Van der Does-van den Berg A,
Hählen K,
Creutzig U,
Veerman AJP:
In vitro chemosensitivity assessed with the MTT assay in childhood acute non-lymphoblastic leukemia.
Leukemia
9:1864,
1995[Medline]
[Order article via Infotrieve]
35.
Pieters R,
Loonen AH,
Huismans DR,
Broekema GJ,
Dirven MWJ,
Heyenbrok MW,
Hählen K,
Veerman AJP:
In vitro drug sensitivity of cells from children with leukemia using the MTT assay with improved culture conditions.
Blood
76:2327,
1990[Abstract/Free Full Text]
36.
Klumper E,
Pieters R,
Veerman AJP,
Huismans DR,
Loonen AH,
Hählen K,
Kaspers GJL,
Van Wering ER,
Hartmann R,
Henze G:
In vitro cellular drug resistance in children with relapsed/refractory acute lymphoblastic leukemia.
Blood
86:3861,
1995[Abstract/Free Full Text]
37.
Pieters R,
Kaspers GJL,
Van Wering ER,
Huismans DR,
Loonen AH,
Hählen K,
Veerman AJP:
Cellular drug resistance profiles that might explain the prognostic value of immunophenotype and age in childhood acute lymphoblastic leukemia.
Leukemia
7:392,
1993[Medline]
[Order article via Infotrieve]
38.
Kaspers GJL,
Pieters R,
Van Zantwijk CH,
Van Wering ER,
Veerman AJP:
Clinical and cell biological features related to cellular drug resistance of childhood acute lymphoblastic leukemia cells.
Leuk Lymphoma
19:407,
1995[Medline]
[Order article via Infotrieve]
39.
Faulkner Pulsford JF,
Sargent JM,
Elgie AW,
Williamson CJ,
Taylor CG:
Comparison of P-glycoprotein expression with in vitro drug sensitivity in fresh blast cells from acute myeloid leukaemia patients.
Br J Biomed Sci
52:188,
1995[Medline]
[Order article via Infotrieve]
40.
Damiani D,
Michieli M,
Michelutti A,
Geromin A,
Raspadori D,
Fanin R,
Savignano C,
Giacca M,
Pileri S,
Mallardi F,
Baccarani M:
Expression of multidrug resistance gene (mdr-1) in human normal leukocytes.
Haematologica
78:12,
1993[Medline]
[Order article via Infotrieve]
41.
Kartner N,
Evernden-Porelle D,
Bradley G,
Ling V:
Detection of P-glycoprotein in multidrug-resistant cell lines by monoclonal antibodies.
Nature
316:820,
1985[Medline]
[Order article via Infotrieve]
42.
Schinkel AH,
Roelofs MEM,
Borst P:
Characterization of the human MDR3 P-glycoprotein and its recognition by P-glycoprotein-specific monoclonal antibodies.
Cancer Res
51:2628,
1991[Abstract/Free Full Text]
43.
Hamada H,
Tsuruo T:
Functional role for the 170- to 180-kDa glycoprotein specific to drug-resistant tumor cells as revealed by monoclonal antibodies.
Proc Natl Acad Sci USA
83:7785,
1986[Abstract/Free Full Text]
44.
Beck J,
Niethammer D,
Gekeler V:
MDR1, MRP, topoisomerase II/, and cyclin A gene expression in acute and chronic leukemias.
Leukemia
10:S39,
1996
45.
Kool M,
De Haas M,
Scheffer GL,
Scheper RJ,
Van Eijk MJT,
Juijn JA,
Baas F,
Borst P:
Analysis of expression of cMOAT (MRP2), MRP3, MRP4, and MRP5, homologues of the multidrug resistance-associated protein gene (MRP1), in human cancer cell lines.
Cancer Res
57:3537,
1997[Abstract/Free Full Text]
46.
Legrand O,
Perrot JY,
Tang RP,
Simonin G,
Gurbuxani S,
Zittoun R,
Marie JP:
Expression of the multidrug resistance-associated protein (MRP) mRNA and protein in normal peripheral blood and bone marrow haemopoietic cells.
Br J Haematol
94:23,
1996[Medline]
[Order article via Infotrieve]
47.
Bordow SB,
Haber M,
Madafiglio J,
Cheung B,
Marshall GM,
Norris MD:
Expression of the multidrug resistance-associated protein (MRP) gene correlates with amplification and overexpression of the N-myc oncogene in childhood neuroblastoma.
Cancer Res
54:5036,
1994[Abstract/Free Full Text]
48.
Norris MD,
Bordow SB,
Marshall GM,
Haber PS,
Cohn SL,
Haber M:
Expression of the gene for multidrug-resistance-associated protein and outcome in patients with neuroblastoma.
N Engl J Med
334:231,
1996[Abstract/Free Full Text]
49.
Chugani DC,
Rome LH,
Kedersha NL:
Evidence that vault ribonucleoprotein particles localize to the nuclear pore complex.
J Cell Sci
106:23,
1993[Abstract]
50.
Schuurhuis GJ,
Broxterman HJ,
De Lange JHM,
Pinedo HM,
Van Heijningen THM,
Kuiper CM,
Scheffer GL,
Scheper RJ,
Van Kalken CK,
Baak JPA,
Lankelma J:
Early multidrug resistance, defined by changes in intracellular doxorubicin distribution, independent of P-glycoprotein.
Br J Cancer
64:857,
1991[Medline]
[Order article via Infotrieve]
51.
Maung ZT,
Hogarth L,
Reid MM,
Proctor SJ,
Hamilton PJ,
Hall AG:
Raised intracellular glutathione levels correlate with in vitro resistance to cytotoxic drugs in leukaemic cells from patients with acute lymphoblastic leukaemia.
Leukemia
8:1487,
1994[Medline]
[Order article via Infotrieve]
52.
Hall AG,
Autzen P,
Cattan AR,
Malcolm AJ,
Cole M,
Kernahan J,
Reid MM:
Expression of µ class glutathione S-transferase correlates with event-free survival in childhood acute lymphoblastic leukemia.
Cancer Res
54:5251,
1994[Abstract/Free Full Text]
53.
Friesen C,
Herr I,
Krammer PH,
Debatin KM:
Involvement of the CD95 (APO-1/Fas) receptor/ligand system in drug-induced apoptosis in leukemia cells.
Nat Med
2:574,
1996[Medline]
[Order article via Infotrieve]
54.
Landowski TH,
Gleason-Guzman MC,
Dalton WS:
Selection for drug resistance results in resistance to Fas-mediated apoptosis.
Blood
89:1854,
1997[Abstract/Free Full Text]
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
M. HIROSE
The Process Behind the Expression of mdr-1/P-gp and mrp/MRP in Human Leukemia/Lymphoma
Anticancer Res,
April 1, 2009;
29(4):
1073 - 1077.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. Hulleman, K. M. Kazemier, A. Holleman, D. J. VanderWeele, C. M. Rudin, M. J. C. Broekhuis, W. E. Evans, R. Pieters, and M. L. Den Boer
Inhibition of glycolysis modulates prednisolone resistance in acute lymphoblastic leukemia cells
Blood,
February 26, 2009;
113(9):
2014 - 2021.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Gjymishka, S. S. Palii, J. Shan, and M. S. Kilberg
Despite Increased ATF4 Binding at the C/EBP-ATF Composite Site following Activation of the Unfolded Protein Response, System A Transporter 2 (SNAT2) Transcription Activity Is Repressed in HepG2 Cells
J. Biol. Chem.,
October 10, 2008;
283(41):
27736 - 27747.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Meshinchi and R. J. Arceci
Prognostic Factors and Risk-Based Therapy in Pediatric Acute Myeloid Leukemia
Oncologist,
March 1, 2007;
12(3):
341 - 355.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Ge, C. L. Haska, K. LaFiura, M. Devidas, S. B. Linda, M. Liu, R. Thomas, J. W. Taub, and L. H. Matherly
Prognostic Role of the Reduced Folate Carrier, the Major Membrane Transporter for Methotrexate, in Childhood Acute Lymphoblastic Leukemia: A Report from the Children's Oncology Group
Clin. Cancer Res.,
January 15, 2007;
13(2):
451 - 457.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Efferth, J.-P. Gillet, A. Sauerbrey, F. Zintl, V. Bertholet, F. de Longueville, J. Remacle, and D. Steinbach
Expression profiling of ATP-binding cassette transporters in childhood T-cell acute lymphoblastic leukemia.
Mol. Cancer Ther.,
August 1, 2006;
5(8):
1986 - 1994.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. M. Zwaan, M. L. den Boer, K. M. Kazemier, K. Hahlen, A. H. Loonen, D. Reinhardt, U. Creutzig, G. J. L. Kaspers, R. Pieters, G. V. Dahl, et al.
Does modulation of P-glycoprotein have clinical relevance in pediatric acute myeloid leukemia?
Blood,
June 15, 2006;
107(12):
4975 - 4977.
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. J. Arceci, J. Sande, B. Lange, K. Shannon, J. Franklin, R. Hutchinson, T. A. Vik, D. Flowers, R. Aplenc, M. S. Berger, et al.
Safety and efficacy of gemtuzumab ozogamicin in pediatric patients with advanced CD33+ acute myeloid leukemia
Blood,
August 15, 2005;
106(4):
1183 - 1188.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Labialle, G. Dayan, L. Gayet, D. Rigal, J. Gambrelle, and L. G. Baggetto
New invMED1 element cis-activates human multidrug-related MDR1 and MVP genes, involving the LRP130 protein
Nucleic Acids Res.,
July 22, 2004;
32(13):
3864 - 3876.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. Steinbach, S. Wittig, G. Cario, S. Viehmann, A. Mueller, B. Gruhn, R. Haefer, F. Zintl, and A. Sauerbrey
The multidrug resistance-associated protein 3 (MRP3) is associated with a poor outcome in childhood ALL and may account for the worse prognosis in male patients and T-cell immunophenotype
Blood,
December 15, 2003;
102(13):
4493 - 4498.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. L. A. Plasschaert, D. M. van der Kolk, E. S. J. M. de Bont, W. A. Kamps, K. Morisaki, S. E. Bates, G. L. Scheffer, R. J. Scheper, E. Vellenga, and E. G. E. de Vries
The Role of Breast Cancer Resistance Protein in Acute Lymphoblastic Leukemia
Clin. Cancer Res.,
November 1, 2003;
9(14):
5171 - 5177.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Itoh, T. Kitano, M. Watanabe, T. Kondo, T. Yabu, Y. Taguchi, K. Iwai, M. Tashima, T. Uchiyama, and T. Okazaki
Possible Role of Ceramide as an Indicator of Chemoresistance: Decrease of the Ceramide Content via Activation of Glucosylceramide Synthase and Sphingomyelin Synthase in Chemoresistant Leukemia
Clin. Cancer Res.,
January 1, 2003;
9(1):
415 - 423.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Filipits, J. Drach, G. Pohl, J. Schuster, T. Stranzl, J. Ackermann, R. Konigsberg, H. Kaufmann, H. Gisslinger, H. Huber, et al.
Expression of the Lung Resistance Protein Predicts Poor Outcome in Patients with Multiple Myeloma
Clin. Cancer Res.,
September 1, 1999;
5(9):
2426 - 2430.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G.J.L. Kaspers, R. Pieters, C.H. Van Zantwijk, E.R. VanWering, A. Van Der Does-Van Den Berg, and A.J.P. Veerman
Prednisolone Resistance in Childhood Acute Lymphoblastic Leukemia: Vitro-Vivo Correlations and Cross-Resistance to Other Drugs
Blood,
July 1, 1998;
92(1):
259 - 266.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
Abstract
Introduction
Abstract