Download SNP309 as predictor for sensitivity of CLL cells to the MDM2

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2168
BLOOD, 1 SEPTEMBER 2008 䡠 VOLUME 112, NUMBER 5
CORRESPONDENCE
To the editor:
SNP309 as predictor for sensitivity of CLL cells to the MDM2 inhibitor nutlin-3a
From a recent comprehensive genomic analysis focusing on loss of
heterozygosity, p53 deletion/mutation, and other chronic lymphocytic leukemia (CLL)–specific risk parameters, Saddler et al
concluded that the p53 status is the major determinant of response
to murine double minute 2 (MDM2) inhibitors in chronic lymphocytic leukemia.1 They found that sensitivity of CLL cells to MDM2
inhibitors was significantly dependent on functional p53, but was
influenced neither by the other genetic aberrations tested (del11q,
trisomy12, del13q14), by Ig VH mutational status, or by Zap-70
expression.1 Their subgroup analysis of CLL cases without p53
aberrations unexpectedly revealed that chemonaive patients who
displayed high sensitivity to MDM2-inhibitor treatment in vitro
showed a significantly reduced treatment-free survival (TFS)
compared with patients with relatively less sensitive CLL cells.1
The molecular reasons for this observation, however, could not be
elucidated in that study.
We recently analyzed the role of a single nucleotide polymorphism (SNP) at position 309 in the promoter region of MDM22
that has been reported to increase expression of MDM2 and to
attenuate p53 function in B-cell CLL (B-CLL).3 We could
demonstrate a significant correlation between the SNP309
genotype and overall survival (OS) and TFS but not with
incidence or onset of B-CLL.2
It was shown earlier by 3 independent groups4-6 and now
confirmed by Saddler et al1 that the MDM2 inhibitor nutlin-3a
efficiently induces apoptosis in B-CLL cells in vitro. In our
present study we could also confirm its proapoptotic activity in
B-CLL cells in general (Figure 1A), which was higher compared
with B cells from healthy donors (Figure 1B). Kojima et al
initially reported that MDM2 overexpression is not an obstacle
to nutlin-induced apoptosis.6 We therefore tested whether sensitivity of B-CLL cells was also independent of the SNP309
genotype. Interestingly, the percentages of apoptotic B-CLL
Specific apoptosis [% of control]
A
100
B-CLL
T/G (n=14) or G/G (n=3)
T/T (n=16)
B
80
P = .007
60
P = .01
P = .01
Irina Seyfried, Sebastian Hofbauer, Markus Stoecher, Richard Greil, and
Inge Tinhofer
This work was supported by a grant from the Paracelsus Medical University
(PMU) Forschungsgesellschaft (grant no. 05/02/014 to I.S.) and by grants of
the Austrian Science Foundation (to I.T.: SFB021-11) and the Province of
Salzburg (to R.G. and I.T.).
Conflict-of-interest disclosure: The authors declare no competing financial
interests.
Correspondence: Inge Tinhofer, Laboratory of Immunological and
Molecular Cancer Research, Department of Hematology, Oncology,
Hemostaseology, Rheumatology and Infectiology, University Hospital
Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria; e-mail:
[email protected].
References
Healthy donors
T/G (n=8)
T/T (n=5)
P = .01
cells following nutlin-3a treatment were even significantly
higher in B-CLL samples with the unfavorable SNP309 T/G or
G/G genotypes (Figure 1A). Higher sensitivity of SNP309 T/G
variants to nutlin-3a treatment was not specific for B-CLL cells,
but also observed in CD19⫹ B cells from healthy controls
(Figure 1B). Comparable with our observation, a positive
correlation of MDM2 basal expression and sensitivity to
nutlin-3a has also been reported recently for AML7 and human
solid tumor cell lines.8
From our results it is tempting to speculate that the aggressive course of disease observed by Saddler et al in patients with
high sensitivity to nutlin-3a treatment in vitro results from a
higher frequency of patients with the unfavorable SNP309 T/G
or G/G genotype in that patient subgroup. This could be tested
easily and, if confirmed, would significantly support the value of
the SNP309 genotype as prognostic factor for aggressive B-CLL
as well as predictor for increased sensitivity to treatment
with nutlin-3a.
P = .04
1.
Saddler C, Ouillette P, Kujawski L, et al. Comprehensive biomarker and
genomic analysis identifies p53 status as the major determinant of response
to MDM2 inhibitors in chronic lymphocytic leukemia. Blood. 2008;111:15841593.
2.
Gryshchenko I, Hofbauer S, Stoecher M, et al. MDM2 SNP309 is associated
with poor outcome in B-cell chronic lymphocytic leukemia. J Clin Oncol. 2008;
26:2252-2257.
3.
Bond GL, Hu W, Bond EE, et al. A single nucleotide polymorphism in the MDM2
promoter attenuates the p53 tumor suppressor pathway and accelerates tumor
formation in humans. Cell. 2004;119:591-602.
4.
Coll-Mulet L, Iglesias-Serret D, Santidrian AF, et al. MDM2 antagonists activate
p53 and synergize with genotoxic drugs in B-cell chronic lymphocytic leukemia
cells. Blood. 2006;107:4109-4114.
5.
Secchiero P, Barbarotto E, Tiribelli M, et al. Functional integrity of the
p53-mediated apoptotic pathway induced by the nongenotoxic agent
nutlin-3 in B-cell chronic lymphocytic leukemia (B-CLL). Blood. 2006;107:
4122-4129.
6.
Kojima K, Konopleva M, McQueen T, O’Brien S, Plunkett W, Andreeff M. Mdm2
inhibitor Nutlin-3a induces p53-mediated apoptosis by transcription-dependent
and transcription-independent mechanisms and may overcome Atm-mediated
resistance to fludarabine in chronic lymphocytic leukemia. Blood. 2006;108:
993-1000.
7.
Kojima K, Konopleva M, Samudio IJ, et al. MDM2 antagonists induce p53dependent apoptosis in AML: implications for leukemia therapy. Blood. 2005;106:
3150-3159.
8.
Tovar C, Rosinski J, Filipovic Z, et al. Small-molecule MDM2 antagonists reveal
aberrant p53 signaling in cancer: implications for therapy. Proc Natl Acad Sci
U S A. 2006;103:1888-1893.
P = .1
40
P = .1
20
0
1
2.5
5
10
1
2.5
5
10
Nutlin-3a [µmol/L]
Figure 1. The SNP309 genotype influences sensitivity of B-CLL cells and
B cells from healthy controls to in vitro-treatment with nutlin-3a. PBMCs
from (A) B-CLL patients or (B) healthy donors with T/T, T/G or G/G SNP309
genotype were treated with increasing concentrations of nutlin-3a for 24 hours.
Analysis of apoptosis in the CD19⫹CD5⫹ fraction (A, B-CLL) or CD19⫹ fraction (B,
healthy controls) was performed by the annexin V–fluorescein isothiocyanate
binding assay. The relative number of cells undergoing nutlin-3a-induced apoptosis are presented as the percentage of untreated control. Sample numbers within
the respective genotype subgroup are indicated.
From www.bloodjournal.org by guest on August 3, 2017. For personal use only.
2008 112: 2168
doi:10.1182/blood-2008-05-158634
SNP309 as predictor for sensitivity of CLL cells to the MDM2 inhibitor
nutlin-3a
Irina Seyfried, Sebastian Hofbauer, Markus Stoecher, Richard Greil and Inge Tinhofer
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